WorldWideScience

Sample records for axonal mitochondrial transport

  1. Dynamics of mitochondrial transport in axons

    Directory of Open Access Journals (Sweden)

    Robert Francis Niescier

    2016-05-01

    Full Text Available The polarized structure and long neurites of neurons pose a unique challenge for proper mitochondrial distribution. It is widely accepted that mitochondria move from the cell body to axon ends and vice versa; however, we have found that mitochondria originating from the axon ends moving in the retrograde direction never reach to the cell body, and only a limited number of mitochondria moving in the anterograde direction from the cell body arrive at the axon ends of mouse hippocampal neurons. Furthermore, we have derived a mathematical formula using the Fokker-Planck equation to characterize features of mitochondrial transport, and the equation could determine altered mitochondrial transport in axons overexpressing parkin. Our analysis will provide new insights into the dynamics of mitochondrial transport in axons of normal and unhealthy neurons.

  2. Cyclophilin D Deficiency Rescues Axonal Mitochondrial Transport in Alzheimer’s Neurons

    OpenAIRE

    Lan Guo; Heng Du; Shiqiang Yan; Xiaoping Wu; Guy M. McKhann; John Xi Chen; Shirley ShiDu Yan

    2013-01-01

    Normal axonal mitochondrial transport and function is essential for the maintenance of synaptic function. Abnormal mitochondrial motility and mitochondrial dysfunction within axons are critical for amyloid β (Aβ)-induced synaptic stress and the loss of synapses relevant to the pathogenesis of Alzheimer's disease (AD). However, the mechanisms controlling axonal mitochondrial function and transport alterations in AD remain elusive. Here, we report an unexplored role of cyclophilin D (CypD)-depe...

  3. Disruption of mitochondrial DNA replication in Drosophila increases mitochondrial fast axonal transport in vivo.

    Directory of Open Access Journals (Sweden)

    Rehan M Baqri

    Full Text Available Mutations in mitochondrial DNA polymerase (pol gamma cause several progressive human diseases including Parkinson's disease, Alper's syndrome, and progressive external ophthalmoplegia. At the cellular level, disruption of pol gamma leads to depletion of mtDNA, disrupts the mitochondrial respiratory chain, and increases susceptibility to oxidative stress. Although recent studies have intensified focus on the role of mtDNA in neuronal diseases, the changes that take place in mitochondrial biogenesis and mitochondrial axonal transport when mtDNA replication is disrupted are unknown. Using high-speed confocal microscopy, electron microscopy and biochemical approaches, we report that mutations in pol gamma deplete mtDNA levels and lead to an increase in mitochondrial density in Drosophila proximal nerves and muscles, without a noticeable increase in mitochondrial fragmentation. Furthermore, there is a rise in flux of bidirectional mitochondrial axonal transport, albeit with slower kinesin-based anterograde transport. In contrast, flux of synaptic vesicle precursors was modestly decreased in pol gamma-alpha mutants. Our data indicate that disruption of mtDNA replication does not hinder mitochondrial biogenesis, increases mitochondrial axonal transport, and raises the question of whether high levels of circulating mtDNA-deficient mitochondria are beneficial or deleterious in mtDNA diseases.

  4. In vivo Imaging of Mitochondrial Transport in Single-Axon Regeneration of Zebrafish Mauthner Cells

    Science.gov (United States)

    Xu, Yang; Chen, Min; Hu, Bingbing; Huang, Rongchen; Hu, Bing

    2017-01-01

    Mitochondrial transport is essential for neuronal function, but the evidence of connections between mitochondrial transport and axon regeneration in the central nervous system (CNS) of living vertebrates remains limited. Here, we developed a novel model to explore mitochondrial transport in a single Mauthner axon (M axon) of zebrafish with non-invasive in vivo imaging. To confirm the feasibility of using this model, we treated labeled zebrafish with nocodazole and demonstrated that it could disrupt mitochondrial transport. We also used two-photon laser axotomy to precisely axotomize M axons and simultaneously recorded their regeneration and the process of mitochondrial transport in living zebrafish larvae. The findings showed that the injured axons with stronger regenerative capability maintain greater mitochondrial motility. Furthermore, to stimulate axon regeneration, treatment with dibutyryl cyclic adenosine monophosphate (db-cAMP) could also augment mitochondrial motility. Taken together, our results provide new evidence that mitochondrial motility is positively correlated with axon regeneration in the living vertebrate CNS. This promising model will be useful for further studies on the interaction between axon regeneration and mitochondrial dynamics, using various genetic and pharmacological techniques. PMID:28174522

  5. Impaired mitochondrial biogenesis, defective axonal transport of mitochondria, abnormal mitochondrial dynamics and synaptic degeneration in a mouse model of Alzheimer's disease.

    Science.gov (United States)

    Calkins, Marcus J; Manczak, Maria; Mao, Peizhong; Shirendeb, Ulziibat; Reddy, P Hemachandra

    2011-12-01

    Increasing evidence suggests that the accumulation of amyloid beta (Aβ) in synapses and synaptic mitochondria causes synaptic mitochondrial failure and synaptic degeneration in Alzheimer's disease (AD). The purpose of this study was to better understand the effects of Aβ in mitochondrial activity and synaptic alterations in neurons from a mouse model of AD. Using primary neurons from a well-characterized Aβ precursor protein transgenic (AβPP) mouse model (Tg2576 mouse line), for the first time, we studied mitochondrial activity, including axonal transport of mitochondria, mitochondrial dynamics, morphology and function. Further, we also studied the nature of Aβ-induced synaptic alterations, and cell death in primary neurons from Tg2576 mice, and we sought to determine whether the mitochondria-targeted antioxidant SS31 could mitigate the effects of oligomeric Aβ. We found significantly decreased anterograde mitochondrial movement, increased mitochondrial fission and decreased fusion, abnormal mitochondrial and synaptic proteins and defective mitochondrial function in primary neurons from AβPP mice compared with wild-type (WT) neurons. Transmission electron microscopy revealed a large number of small mitochondria and structurally damaged mitochondria, with broken cristae in AβPP primary neurons. We also found an increased accumulation of oligomeric Aβ and increased apoptotic neuronal death in the primary neurons from the AβPP mice relative to the WT neurons. Our results revealed an accumulation of intraneuronal oligomeric Aβ, leading to mitochondrial and synaptic deficiencies, and ultimately causing neurodegeneration in AβPP cultures. However, we found that the mitochondria-targeted antioxidant SS31 restored mitochondrial transport and synaptic viability, and decreased the percentage of defective mitochondria, indicating that SS31 protects mitochondria and synapses from Aβ toxicity.

  6. The genetics of axonal transport and axonal transport disorders.

    Directory of Open Access Journals (Sweden)

    Jason E Duncan

    2006-09-01

    Full Text Available Neurons are specialized cells with a complex architecture that includes elaborate dendritic branches and a long, narrow axon that extends from the cell body to the synaptic terminal. The organized transport of essential biological materials throughout the neuron is required to support its growth, function, and viability. In this review, we focus on insights that have emerged from the genetic analysis of long-distance axonal transport between the cell body and the synaptic terminal. We also discuss recent genetic evidence that supports the hypothesis that disruptions in axonal transport may cause or dramatically contribute to neurodegenerative diseases.

  7. Miro, MCU, and calcium: bridging our understanding of mitochondrial movement in axons

    Directory of Open Access Journals (Sweden)

    Robert eNiescier

    2013-09-01

    Full Text Available Neurons are extremely polarized structures with long axons and dendrites, which require proper distribution of mitochondria and maintenance of mitochondrial dynamics for neuronal functions and survival. Indeed, recent studies show that various neurological disorders are linked to mitochondrial transport in neurons. Mitochondrial anterograde transport is believed to deliver metabolic energy to synaptic terminals where energy demands are high, while mitochondrial retrograde transport is required to repair or remove damaged mitochondria in axons. It has been suggested that Ca2+ plays a key role in regulating mitochondrial transport by altering the configuration of mitochondrial protein, miro. However, molecular mechanisms that regulate mitochondrial transport in neurons still are not well characterized. In this review, we will discuss the roles of miro in mitochondrial transport and how the recently identified components of the mitochondrial calcium uniporter add to our current model of mitochondrial mobility regulation.

  8. Miro, MCU, and calcium: bridging our understanding of mitochondrial movement in axons.

    Science.gov (United States)

    Niescier, Robert F; Chang, Karen T; Min, Kyung-Tai

    2013-09-10

    Neurons are extremely polarized structures with long axons and dendrites, which require proper distribution of mitochondria and maintenance of mitochondrial dynamics for neuronal functions and survival. Indeed, recent studies show that various neurological disorders are linked to mitochondrial transport in neurons. Mitochondrial anterograde transport is believed to deliver metabolic energy to synaptic terminals where energy demands are high, while mitochondrial retrograde transport is required to repair or remove damaged mitochondria in axons. It has been suggested that Ca(2) (+) plays a key role in regulating mitochondrial transport by altering the configuration of mitochondrial protein, miro. However, molecular mechanisms that regulate mitochondrial transport in neurons still are not well characterized. In this review, we will discuss the roles of miro in mitochondrial transport and how the recently identified components of the mitochondrial calcium uniporter add to our current model of mitochondrial mobility regulation.

  9. Geniposide Alleviates Amyloid-Induced Synaptic Injury by Protecting Axonal Mitochondrial Trafficking

    Science.gov (United States)

    Zhang, Haijing; Zhao, Chunhui; Lv, Cui; Liu, Xiaoli; Du, Shijing; Li, Zhi; Wang, Yongyan; Zhang, Wensheng

    2017-01-01

    Synaptic and mitochondrial pathologies are early events in the progression of Alzheimer's disease (AD). Normal axonal mitochondrial function and transport play crucial roles in maintaining synaptic function by producing high levels of adenosine triphosphate and buffering calcium. However, there can be abnormal axonal mitochondrial trafficking, distribution, and fragmentation, which are strongly correlated with amyloid-β (Aβ)-induced synaptic loss and dysfunction. The present study examined the neuroprotective effect of geniposide, a compound extracted from gardenia fruit in Aβ-treated neurons and an AD mouse model. Geniposide alleviated Aβ-induced axonal mitochondrial abnormalities by increasing axonal mitochondrial density and length and improving mitochondrial motility and trafficking in cultured hippocampal neurons, consequently ameliorating synaptic damage by reversing synaptic loss, addressing spine density and morphology abnormalities, and ameliorating the decreases in synapse-related proteins in neurons and APPswe/PS1dE9 mice. These findings provide new insights into the effects of geniposide administration on neuronal and synaptic functions under conditions of Aβ enrichment. PMID:28179878

  10. A heterogeneous population of nuclear-encoded mitochondrial mRNAs is present in the axons of primary sympathetic neurons.

    Science.gov (United States)

    Aschrafi, Armaz; Kar, Amar N; Gale, Jenna R; Elkahloun, Abdel G; Vargas, Jose Noberto S; Sales, Naomi; Wilson, Gabriel; Tompkins, Miranda; Gioio, Anthony E; Kaplan, Barry B

    2016-09-01

    Mitochondria are enriched in subcellular regions of high energy consumption, such as axons and pre-synaptic nerve endings. Accumulating evidence suggests that mitochondrial maintenance in these distal structural/functional domains of the neuron depends on the "in-situ" translation of nuclear-encoded mitochondrial mRNAs. In support of this notion, we recently provided evidence for the axonal targeting of several nuclear-encoded mRNAs, such as cytochrome c oxidase, subunit 4 (COXIV) and ATP synthase, H+ transporting and mitochondrial Fo complex, subunit C1 (ATP5G1). Furthermore, we showed that axonal trafficking and local translation of these mRNAs plays a critical role in the generation of axonal ATP. Using a global gene expression analysis, this study identified a highly diverse population of nuclear-encoded mRNAs that were enriched in the axon and presynaptic nerve terminals. Among this population of mRNAs, fifty seven were found to be at least two-fold more abundant in distal axons, as compared with the parental cell bodies. Gene ontology analysis of the nuclear-encoded mitochondrial mRNAs suggested functions for these gene products in molecular and biological processes, including but not limited to oxidoreductase and electron carrier activity and proton transport. Based on these results, we postulate that local translation of nuclear-encoded mitochondrial mRNAs present in the axons may play an essential role in local energy production and maintenance of mitochondrial function.

  11. Where does slow axonal transport go?

    Science.gov (United States)

    Terada, Sumio

    2003-12-01

    Axonal transport is the specialized and well-developed intracellular transport system for regulated and/or long-distance transport based on generalized cellular machineries. Among them, slow axonal transport conveys cytoplasmic proteins. The motor molecule, the nature of transporting complex and the transport regulation mechanism for slow transport are still unclarified. There has been a dispute regarding the nature of transporting complex of cytoskeletal proteins, polymer-sliding hypothesis versus subunit-transport theory. Recent data supporting the hypothesis of polymer sliding in cultured neurons only reconfirm the previously reported structure and this inference suffers from the lack of ultrastructural evidence and the direct relevance to the physiological slow transport phenomenon in vivo. Observation of the moving cytoskeletal proteins in vivo using transgenic mice or squid giant axons revealed that subunits do move in a microtubule-dependent manner, strongly indicating the involvement of microtubule-based motor kinesin. If the slow transport rate reflects the intermittent fast transport dependent on kinesin motor, we have to investigate the molecular constituents of the transporting complex in more detail and evaluate why the motor and cargo interaction is so unstable. This kind of weak and fluctuating interaction between various molecular pairs could not be detected by conventional techniques, thus necessitating the establishment of a new experimental system before approaching the molecular regulation problem.

  12. Synaptic Democracy and Vesicular Transport in Axons

    Science.gov (United States)

    Bressloff, Paul C.; Levien, Ethan

    2015-04-01

    Synaptic democracy concerns the general problem of how regions of an axon or dendrite far from the cell body (soma) of a neuron can play an effective role in neuronal function. For example, stimulated synapses far from the soma are unlikely to influence the firing of a neuron unless some sort of active dendritic processing occurs. Analogously, the motor-driven transport of newly synthesized proteins from the soma to presynaptic targets along the axon tends to favor the delivery of resources to proximal synapses. Both of these phenomena reflect fundamental limitations of transport processes based on a localized source. In this Letter, we show that a more democratic distribution of proteins along an axon can be achieved by making the transport process less efficient. This involves two components: bidirectional or "stop-and-go" motor transport (which can be modeled in terms of advection-diffusion), and reversible interactions between motor-cargo complexes and synaptic targets. Both of these features have recently been observed experimentally. Our model suggests that, just as in human societies, there needs to be a balance between "efficiency" and "equality".

  13. Differential extraction of axonally transported proteoglycans

    Energy Technology Data Exchange (ETDEWEB)

    Elam, J.S. (Florida State Univ., Tallahassee (USA))

    1990-10-01

    Axonally transported proteoglycans were differentially solubilized by a sequence of extractions designed to infer their relationship to nerve terminal membranes. Groups of goldfish were injected unilaterally with 35SO4 and contralateral optic tecta containing axonally transported molecules were removed 16 h later. Tecta were homogenized in isotonic buffer and centrifuged at 100,000 g for 60 min to create a total supernatant fraction. Subsequent homogenizations followed by recentrifugation were with hypotonic buffer (lysis extract), 1 M NaCl, Triton X-100 or alternatively Triton-1 M NaCl. Populations of proteoglycans in each extract were isolated on DEAE ion exchange columns and evaluated for content of glycosaminoglycans (GAGs). Results show the distribution of transported proteoglycans to be 26.3% total soluble, 13.7% lysis extract, 13.8% NaCl extract, 12.2% Triton extract, and 46.2% Triton-NaCl extract. Proteoglycans from all fractions contained heparan sulfate as the predominant GAG, with lesser amounts of chondroitin (4 or 6) sulfate. The possible localizations of transported proteoglycans suggested by the extraction results are discussed.

  14. Mitochondrial ABC transporters.

    Science.gov (United States)

    Lill, R; Kispal, G

    2001-01-01

    In contrast to bacteria, mitochondria contain only a few ATP binding cassette (ABC) transporters in their inner membrane. The known mitochondrial ABC proteins fall into two major classes that, in the yeast Saccharomyces cerevisiae, are represented by the half-transporter Atm1p and the two closely homologous proteins Mdl1p and Mdl2p. In humans two Atm1p orthologues (ABC7 and MTABC3) and two proteins homologous to Mdll/2p have been localized to mitochondria. The Atm1p-like proteins perform an important function in mitochondrial iron homeostasis and in the maturation of Fe/S proteins in the cytosol. Mutations in ABC7 are causative of hereditary X-linked sideroblastic anemia and cerebellar ataxia (XLSA/A). MTABC3 may be a candidate gene for the lethal neonatal syndrome. The function of the mitochondrial Mdl1/2p-like proteins is not clear at present with the notable exception of murine ABC-me that may transport intermediates of heme biosynthesis from the matrix to the cytosol in erythroid tissues.

  15. The pathophysiology of axonal transport in alzheimer’s disease

    OpenAIRE

    Vicario Orri, Elena; Opazo, Carlos; Muñoz López, Francisco José, 1964-

    2015-01-01

    Neurons communicate in the nervous system by carrying out information along the length of their axons to finally transmit it at the synapse. Proper function of axons and axon terminals relies on the transport of proteins, organelles, vesicles, and other elements from the site of synthesis in the cell body. Conversely, neurotrophins secreted from axonal targets and other components at nerve terminals need to travel toward the cell body for clearance. Molecular motors, namely kinesins and dynei...

  16. Organophosphate Related Alterations in Myelin and Axonal Transport in the Living Mammalian Brain

    Science.gov (United States)

    2015-10-01

    and tri-o-cresyl phosphate (i.e., compounds associated with OP-induced delayed neuropathies -OPIDN) inhibited fast anterograde axonal transport in an ex...other deleterious effects of OPs that may be additive (or unrelated) to AChE inhibition and include oxidative stress, impairments of mitochondrial

  17. Fast axonal transport in early experimental disc edema.

    Science.gov (United States)

    Radius, R L; Anderson, D R

    1980-02-01

    Previous work has documented impairment of slow axonal transport in papilledema, but the abnormalities in rapid transport were less certain. Therefore fast axonal transport was studied in 19 primate eyes subjected to ocular hypotony for 6 to 72 hr following surgical fistulization of the anterior chamber. Mild, irregular alterations in fast axonal transport were detected only after nerve head swelling was apparent. These changes in fast transport mechanisms in cases of nerve head edema occur after, and may be secondary to, impaired slow axoplasmic flow and the resultant axonal swelling. Furthermore, since prolonged complete interruption of axonal transport is theoretically inconsistent with the continued normal neuron function characteristic of papilledema and, moreover, since previous data shows a "slowdown" rather than complete blockade of axonal transport in papilledema, it is likely that in eyes with papilledema there does not exist a complete flock of axonal transport. Therefore we hypothesize that the swelling results when slow axoplasmic flow is locally slowed down but not totally stopped, with the axon distention producing secondary mild, irregular changes in fast axonal transport.

  18. Increased Human Wildtype Tau Attenuates Axonal Transport Deficits Caused by Loss of APP in Mouse Models

    OpenAIRE

    Smith, Karen D.B.; Erica Peethumnongsin; Han Lin; Hui Zheng; Pautler, Robia G.

    2010-01-01

    Amyloid precursor protein (APP) is implicated in axonal elongation, synaptic plasticity, and axonal transport. However, the role of APP on axonal transport in conjunction with the microtubule associated protein tau continues to be debated. Here we measured in vivo axonal transport in APP knockout mice with Manganese Enhanced MRI (MEMRI) to determine whether APP is necessary for maintaining normal axonal transport. We also tested how overexpression and mutations of tau affect axonal transport ...

  19. Morphology of axonal transport abnormalities in primate eyes.

    Science.gov (United States)

    Radius, R L; Anderson, D R

    1981-11-01

    The ultrastructure of the retina and optic nerve head was studied in primate eyes after central retinal artery occlusion. Within 2 hours of the vascular occlusion the inner retinal layers undergo watery (isosmotic) swelling. This watery swelling of axons and astroglia extends into the nerve head as far back as the anterior boundary of the scleral lamina cribrosa. The swelling is increased 4 hours after the occlusion, and by 24 hours disintegration has occurred. At the optic nerve head mitochondria and vesicles of smooth endoplasmic reticulum begin to accumulate within 2 hours. The accumulation increases at 4 hours and persists to 24 hours. The watery swelling seems characteristic of ischaemic axons. Membranous organelles accumulate at the boundary of an ischaemic zone when material carried by axonal transport is brought via the healthy axon segment to the boundary, but they cannot proceed further into the ischaemic zone. Such accumulation is typical of locations where rapid orthograde axonal transport or retrograde axonal transport is blocked. In contrast, when slow axonal flow is impaired, the swelling is characterised by an excess of cytoplasmic gel without a marked accumulation of organelles. Rapid orthograde transport and retrograde transport seem to be closely related to one another, while slow axoplasmic flow seems fundamentally different. From morphological findings we suspect that, in experimental glaucoma, intraocular pressure first affects the intracellular physiological process of rapid orthograde and retrograde axonal transport. Watery swelling may not occur unless the ischaemic injury to cell metabolism is more advanced. In contrast, in experimental papilloedema, the swelling results predominantly from impaired slow axoplasmic flow.

  20. Mitochondrial biogenesis and fission in axons in cell culture and animal models of diabetic neuropathy.

    Science.gov (United States)

    Vincent, Andrea M; Edwards, James L; McLean, Lisa L; Hong, Yu; Cerri, Federica; Lopez, Ignazio; Quattrini, Angelo; Feldman, Eva L

    2010-10-01

    Mitochondrial-mediated oxidative stress in response to high glucose is proposed as a primary cause of dorsal root ganglia (DRG) neuron injury in the pathogenesis of diabetic neuropathy. In the present study, we report a greater number of mitochondria in both myelinated and unmyelinated dorsal root axons in a well-established model of murine diabetic neuropathy. No similar changes were seen in younger diabetic animals without neuropathy or in the ventral motor roots of any diabetic animals. These findings led us to examine mitochondrial biogenesis and fission in response to hyperglycemia in the neurites of cultured DRG neurons. We demonstrate overall mitochondrial biogenesis via increases in mitochondrial transcription factors and increases in mitochondrial DNA in both DRG neurons and axons. However, this process occurs over a longer time period than a rapidly observed increase in the number of mitochondria in DRG neurites that appears to result, at least in part, from mitochondrial fission. We conclude that during acute hyperglycemia, mitochondrial fission is a prominent response, and excessive mitochondrial fission may result in dysregulation of energy production, activation of caspase 3, and subsequent DRG neuron injury. During more prolonged hyperglycemia, there is evidence of compensatory mitochondrial biogenesis in axons. Our data suggest that an imbalance between mitochondrial biogenesis and fission may play a role in the pathogenesis of diabetic neuropathy.

  1. Functional Impact of Corticotropin-Releasing Factor Exposure on Tau Phosphorylation and Axon Transport.

    Science.gov (United States)

    Le, Michelle H; Weissmiller, April M; Monte, Louise; Lin, Po Han; Hexom, Tia C; Natera, Orlangie; Wu, Chengbiao; Rissman, Robert A

    2016-01-01

    Stress exposure or increased levels of corticotropin-releasing factor (CRF) induce hippocampal tau phosphorylation (tau-P) in rodent models, a process that is dependent on the type-1 CRF receptor (CRFR1). Although these preclinical studies on stress-induced tau-P provide mechanistic insight for epidemiological work that identifies stress as a risk factor for Alzheimer's disease (AD), the actual impact of stress-induced tau-P on neuronal function remains unclear. To determine the functional consequences of stress-induced tau-P, we developed a novel mouse neuronal cell culture system to explore the impact of acute (0.5hr) and chronic (2hr) CRF treatment on tau-P and integral cell processes such as axon transport. Consistent with in vivo reports, we found that chronic CRF treatment increased tau-P levels and caused globular accumulations of phosphorylated tau in dendritic and axonal processes. Furthermore, while both acute and chronic CRF treatment led to significant reduction in CREB activation and axon transport of brain-derived neurotrophic factor (BDNF), this was not the case with mitochondrial transport. Acute CRF treatment caused increased mitochondrial velocity and distance traveled in neurons, while chronic CRF treatment modestly decreased mitochondrial velocity and greatly increased distance traveled. These results suggest that transport of cellular energetics may take priority over growth factors during stress. Tau-P was required for these changes, as co-treatment of CRF with a GSK kinase inhibitor prevented CRF-induced tau-P and all axon transport changes. Collectively, our results provide mechanistic insight into the consequences of stress peptide-induced tau-P and provide an explanation for how chronic stress via CRF may lead to neuronal vulnerability in AD.

  2. Functional Impact of Corticotropin-Releasing Factor Exposure on Tau Phosphorylation and Axon Transport.

    Directory of Open Access Journals (Sweden)

    Michelle H Le

    Full Text Available Stress exposure or increased levels of corticotropin-releasing factor (CRF induce hippocampal tau phosphorylation (tau-P in rodent models, a process that is dependent on the type-1 CRF receptor (CRFR1. Although these preclinical studies on stress-induced tau-P provide mechanistic insight for epidemiological work that identifies stress as a risk factor for Alzheimer's disease (AD, the actual impact of stress-induced tau-P on neuronal function remains unclear. To determine the functional consequences of stress-induced tau-P, we developed a novel mouse neuronal cell culture system to explore the impact of acute (0.5hr and chronic (2hr CRF treatment on tau-P and integral cell processes such as axon transport. Consistent with in vivo reports, we found that chronic CRF treatment increased tau-P levels and caused globular accumulations of phosphorylated tau in dendritic and axonal processes. Furthermore, while both acute and chronic CRF treatment led to significant reduction in CREB activation and axon transport of brain-derived neurotrophic factor (BDNF, this was not the case with mitochondrial transport. Acute CRF treatment caused increased mitochondrial velocity and distance traveled in neurons, while chronic CRF treatment modestly decreased mitochondrial velocity and greatly increased distance traveled. These results suggest that transport of cellular energetics may take priority over growth factors during stress. Tau-P was required for these changes, as co-treatment of CRF with a GSK kinase inhibitor prevented CRF-induced tau-P and all axon transport changes. Collectively, our results provide mechanistic insight into the consequences of stress peptide-induced tau-P and provide an explanation for how chronic stress via CRF may lead to neuronal vulnerability in AD.

  3. Mitochondrial Dynamics Decrease Prior to Axon Degeneration Induced by Vincristine and are Partially Rescued by Overexpressed cytNmnat1.

    Directory of Open Access Journals (Sweden)

    Gregory Berbusse

    2016-07-01

    Full Text Available Axon degeneration is a prominent feature of various neurodegenerative diseases, such as Parkinson’s and Alzheimer’s, and is often characterized by aberrant mitochondrial dynamics. Mitochondrial fission, fusion, and motility have been shown to be particularly important in progressive neurodegeneration. Thus we investigated these imperative dynamics, as well as mitochondrial fragmentation in vincristine induced axon degradation in cultured DRG neurons. CytNmnat1 inhibits axon degeneration in various paradigms including vincristine toxicity. The mechanism of its protection is not yet fully understood; therefore, we also investigated the effect of cytNmnat1 on mitochondrial dynamics in vincristine treated neurons. We observed that vincristine treatment decreases the rate of mitochondrial fission, fusion and motility and induces mitochondrial fragmentation. These mitochondrial events precede visible axon degeneration. Overexpression of cytNmnat1 inhibits axon degeneration and preserves the normal mitochondrial dynamics and motility in vincristine treated neurons. We suggest the alterations in mitochondrial structure and dynamics are early events which lead to axon degeneration and cytNmnat1 blocks axon degeneration by halting the vincristine induced changes to mitochondrial structure and dynamics.

  4. The Myriad Roles of Miro in the Nervous System: Axonal Transport of Mitochondria and Beyond

    Directory of Open Access Journals (Sweden)

    Bingwei eLu

    2014-10-01

    Full Text Available Mitochondrial rho GTPase (Miro is a mitochondrial outer membrane protein containing two GTPase domains and two helix-loop-helix Ca2+-binding domains called EF hands. Pioneering genetic studies in Drosophila first revealed a key function of Miro in regulating the axonal transport of mitochondria, during which Miro forms a multi-protein transport complex with Milton and Kinesin heavy chain (KHC to link trafficking mitochondria with the microtubule cytoskeleton. Recent studies showed that through binding to the EF hands of Miro and causing conformational changes of Miro and alteration of protein-protein interactions within the transport complex, Ca2+ can alter the engagement of mitochondria with the microtubule (MT/kinesin network, offering one mechanism to match mitochondrial distribution with neuronal activity. Despite the importance of the Miro/Milton/Kinesin complex in regulating mitochondrial transport in metazoans, not all components of the transport complex are conserved in lower organisms, and transport-independent functions of Miro are emerging. Here we review the diverse functions of the evolutionarily conserved Miro proteins that are relevant to the development, maintenance, and functioning of the nervous system and discuss the potential contribution of Miro dysfunction to the pathogenesis of diseases of the nervous system.

  5. Loss of mitochondrial fission depletes axonal mitochondria in midbrain dopamine neurons.

    Science.gov (United States)

    Berthet, Amandine; Margolis, Elyssa B; Zhang, Jue; Hsieh, Ivy; Zhang, Jiasheng; Hnasko, Thomas S; Ahmad, Jawad; Edwards, Robert H; Sesaki, Hiromi; Huang, Eric J; Nakamura, Ken

    2014-10-22

    Disruptions in mitochondrial dynamics may contribute to the selective degeneration of dopamine (DA) neurons in Parkinson's disease (PD). However, little is known about the normal functions of mitochondrial dynamics in these neurons, especially in axons where degeneration begins, and this makes it difficult to understand the disease process. To study one aspect of mitochondrial dynamics-mitochondrial fission-in mouse DA neurons, we deleted the central fission protein dynamin-related protein 1 (Drp1). Drp1 loss rapidly eliminates the DA terminals in the caudate-putamen and causes cell bodies in the midbrain to degenerate and lose α-synuclein. Without Drp1, mitochondrial mass dramatically decreases, especially in axons, where the mitochondrial movement becomes uncoordinated. However, in the ventral tegmental area (VTA), a subset of midbrain DA neurons characterized by small hyperpolarization-activated cation currents (Ih) is spared, despite near complete loss of their axonal mitochondria. Drp1 is thus critical for targeting mitochondria to the nerve terminal, and a disruption in mitochondrial fission can contribute to the preferential death of nigrostriatal DA neurons.

  6. Computational Analysis of Axonal Transport: A Novel Assessment of Neurotoxicity, Neuronal Development and Functions

    Directory of Open Access Journals (Sweden)

    Toshiyuki Gotoh

    2012-03-01

    Full Text Available Axonal transport plays a crucial role in neuronal morphogenesis, survival and function. Despite its importance, however, the molecular mechanisms of axonal transport remain mostly unknown because a simple and quantitative assay system for monitoring this cellular process has been lacking. In order to better characterize the mechanisms involved in axonal transport, we formulate a novel computer-assisted monitoring system of axonal transport. Potential uses of this system and implications for future studies will be discussed.

  7. Aberrant Schwann cell lipid metabolism linked to mitochondrial deficits leads to axon degeneration and neuropathy.

    Science.gov (United States)

    Viader, Andreu; Sasaki, Yo; Kim, Sungsu; Strickland, Amy; Workman, Cayce S; Yang, Kui; Gross, Richard W; Milbrandt, Jeffrey

    2013-03-06

    Mitochondrial dysfunction is a common cause of peripheral neuropathy. Much effort has been devoted to examining the role played by neuronal/axonal mitochondria, but how mitochondrial deficits in peripheral nerve glia (Schwann cells [SCs]) contribute to peripheral nerve diseases remains unclear. Here, we investigate a mouse model of peripheral neuropathy secondary to SC mitochondrial dysfunction (Tfam-SCKOs). We show that disruption of SC mitochondria activates a maladaptive integrated stress response (ISR) through the actions of heme-regulated inhibitor (HRI) kinase, and causes a shift in lipid metabolism away from fatty acid synthesis toward oxidation. These alterations in SC lipid metabolism result in depletion of important myelin lipid components as well as in accumulation of acylcarnitines (ACs), an intermediate of fatty acid β-oxidation. Importantly, we show that ACs are released from SCs and induce axonal degeneration. A maladaptive ISR as well as altered SC lipid metabolism are thus underlying pathological mechanisms in mitochondria-related peripheral neuropathies.

  8. Live imaging of mitochondrial dynamics in CNS dopaminergic neurons in vivo demonstrates early reversal of mitochondrial transport following MPP(+) exposure.

    Science.gov (United States)

    Dukes, April A; Bai, Qing; Van Laar, Victor S; Zhou, Yangzhong; Ilin, Vladimir; David, Christopher N; Agim, Zeynep S; Bonkowsky, Joshua L; Cannon, Jason R; Watkins, Simon C; Croix, Claudette M St; Burton, Edward A; Berman, Sarah B

    2016-11-01

    Extensive convergent evidence collectively suggests that mitochondrial dysfunction is central to the pathogenesis of Parkinson's disease (PD). Recently, changes in the dynamic properties of mitochondria have been increasingly implicated as a key proximate mechanism underlying neurodegeneration. However, studies have been limited by the lack of a model in which mitochondria can be imaged directly and dynamically in dopaminergic neurons of the intact vertebrate CNS. We generated transgenic zebrafish in which mitochondria of dopaminergic neurons are labeled with a fluorescent reporter, and optimized methods allowing direct intravital imaging of CNS dopaminergic axons and measurement of mitochondrial transport in vivo. The proportion of mitochondria undergoing axonal transport in dopaminergic neurons decreased overall during development between 2days post-fertilization (dpf) and 5dpf, at which point the major period of growth and synaptogenesis of the relevant axonal projections is complete. Exposure to 0.5-1.0mM MPP(+) between 4 and 5dpf did not compromise zebrafish viability or cause detectable changes in the number or morphology of dopaminergic neurons, motor function or monoaminergic neurochemistry. However, 0.5mM MPP(+) caused a 300% increase in retrograde mitochondrial transport and a 30% decrease in anterograde transport. In contrast, exposure to higher concentrations of MPP(+) caused an overall reduction in mitochondrial transport. This is the first time mitochondrial transport has been observed directly in CNS dopaminergic neurons of a living vertebrate and quantified in a PD model in vivo. Our findings are compatible with a model in which damage at presynaptic dopaminergic terminals causes an early compensatory increase in retrograde transport of compromised mitochondria for degradation in the cell body. These data are important because manipulation of early pathogenic mechanisms might be a valid therapeutic approach to PD. The novel transgenic lines and

  9. Rapid axonal transport in primate optic nerve. Distribution of pressure-induced interruption.

    Science.gov (United States)

    Radius, R L; Anderson, D R

    1981-04-01

    Six primate eyes were studied after four hours of elevated intraocular pressure. Tissue specimens from the region of the lamina cribrosa were examined in cross section by transmission electron microscopy. Interruption in fast orthograde and retrograde axonal transport was identified in individual axons by noting accumulation of membraneous microorganelles, such as mitochondria and microvesicles within axon cylinders. Although organelle accumulation varied from bundle to bundle, involvement of individual axons was diffuse across the extent of a specific axon bundle. This observation contradicts the apparent association of axonal transport block with crosswise-oriented trabecular beams at the level of the lamina cribrosa as seen in tissue specimens examined in longitudinal section. It also fails to support the notion that blocked axonal transport with elevated pressure is produced by kinking of axons at the lamina.

  10. Diversity of Mitochondrial Pathology in a Mouse Model of Axonal Degeneration in Synucleinopathies

    Directory of Open Access Journals (Sweden)

    Akio Sekigawa

    2013-01-01

    Full Text Available There is mounting evidence for a role of mitochondrial dysfunction in the pathogenesis of α-synucleinopathies such as Parkinson's disease (PD and dementia with Lewy bodies (DLB. In particular, recent studies have demonstrated that failure of mitochondrial quality control caused by loss of function of the PTEN-induced kinase 1 (PINK1, PARK6 Parkin (PARK2 pathway may be causative in some familial PD. In sporadic PD, α-synuclein aggregation may interfere with mitochondrial function, and this might be further exacerbated by leucine-rich repeat kinase 2 (LRRK2. The majority of these findings have been obtained in Drosophila and cell cultures, whereas the objective of this paper is to discuss our recent results on the axonal pathology of brains derived from transgenic mice expressing α-synuclein or DLB-linked P123H β-synuclein. In line with the current view of the pathogenesis of sporadic PD, mitochondria abnormally accumulated in α-synuclein/LRRK2-immunopositive axonal swellings in mice expressing α-synuclein. Curiously, neither mitochondria nor LRRK2 was present in the swellings of mice expressing P123H β-synuclein, suggesting that α- and β-synuclein might play differential roles in the mitochondrial pathology of α-synucleinopathies.

  11. Axonal transport interruption and anatomy at the lamina cribrosa.

    Science.gov (United States)

    Radius, R L; Bade, B

    1982-10-01

    Pressure-induced, focal axonal transport abnormalities were studied in 14 cat eyes by the examination of serial step-section tissue radioautogram. Although the patterns of the transport interruption at the lamina cribrosa varied from eye to eye, the temporal sectors of the nerve head were most often involved by this abnormality. The anatomy at the lamina cribrosa was studied in adjacent (6 micrometers) cross-sectional specimens. The thickness of the extra-bundle trabeculae and the nerve fiber bundle dimensions including the cross-sectional area and the number and the shape (the ratio of the major and the minor axis diameters) of the laminar pores were measured by computer-assisted perimeter analysis. There was no correlation between the location of the transport interruption and any of these anatomic measurements.

  12. Mitochondrial dynamics and peripheral neuropathy.

    Science.gov (United States)

    Baloh, Robert H

    2008-02-01

    Peripheral neuropathy is perhaps the archetypal disease of axonal degeneration, characteristically involving degeneration of the longest axons in the body. Evidence from both inherited and acquired forms of peripheral neuropathy strongly supports that the primary pathology is in the axons themselves and points to disruption of axonal transport as an important disease mechanism. Recent studies in human genetics have further identified abnormalities in mitochondrial dynamics--the fusion, fission, and movement of mitochondria--as a player in the pathogenesis of inherited peripheral neuropathy. This review provides an update on the mechanisms of mitochondrial trafficking in axons and the emerging relationship between the disruption of mitochondrial dynamics and axonal degeneration. Evidence suggests mitochondria are a "critical cargo" whose transport is necessary for proper axonal and synaptic function. Importantly, understanding the regulation of mitochondrial movement and the consequences of decreased axonal mitochondrial function may define new paths for therapeutic agents in peripheral neuropathy and other neurodegenerative diseases.

  13. Neuroinflammation by cytotoxic T-lymphocytes impairs retrograde axonal transport in an oligodendrocyte mutant mouse.

    Directory of Open Access Journals (Sweden)

    Chi Wang Ip

    Full Text Available Mice overexpressing proteolipid protein (PLP develop a leukodystrophy-like disease involving cytotoxic, CD8+ T-lymphocytes. Here we show that these cytotoxic T-lymphocytes perturb retrograde axonal transport. Using fluorogold stereotactically injected into the colliculus superior, we found that PLP overexpression in oligodendrocytes led to significantly reduced retrograde axonal transport in retina ganglion cell axons. We also observed an accumulation of mitochondria in the juxtaparanodal axonal swellings, indicative for a disturbed axonal transport. PLP overexpression in the absence of T-lymphocytes rescued retrograde axonal transport defects and abolished axonal swellings. Bone marrow transfer from wildtype mice, but not from perforin- or granzyme B-deficient mutants, into lymphocyte-deficient PLP mutant mice led again to impaired axonal transport and the formation of axonal swellings, which are predominantly located at the juxtaparanodal region. This demonstrates that the adaptive immune system, including cytotoxic T-lymphocytes which release perforin and granzyme B, are necessary to perturb axonal integrity in the PLP-transgenic disease model. Based on our observations, so far not attended molecular and cellular players belonging to the immune system should be considered to understand pathogenesis in inherited myelin disorders with progressive axonal damage.

  14. Tau phosphorylation affects its axonal transport and degradation

    Science.gov (United States)

    Rodríguez-Martín, Teresa; Cuchillo-Ibáñez, Inmaculada; Noble, Wendy; Nyenya, Fanon; Anderton, Brian H.; Hanger, Diane P.

    2013-01-01

    Phosphorylated forms of microtubule-associated protein tau accumulate in neurofibrillary tangles in Alzheimer's disease. To investigate the effects of specific phosphorylated tau residues on its function, wild type or phosphomutant tau was expressed in cells. Elevated tau phosphorylation decreased its microtubule binding and bundling, and increased the number of motile tau particles, without affecting axonal transport kinetics. In contrast, reducing tau phosphorylation enhanced the amount of tau bound to microtubules and inhibited axonal transport of tau. To determine whether differential tau clearance is responsible for the increase in phosphomimic tau, we inhibited autophagy in neurons which resulted in a 3-fold accumulation of phosphomimic tau compared with wild type tau, and endogenous tau was unaffected. In autophagy-deficient mouse embryonic fibroblasts, but not in neurons, proteasomal degradation of phosphomutant tau was also reduced compared with wild type tau. Therefore, autophagic and proteasomal pathways are involved in tau degradation, with autophagy appearing to be the primary route for clearing phosphorylated tau in neurons. Defective autophagy might contribute to the accumulaton of tau in neurodegenerative diseases. PMID:23601672

  15. Effect of vesicle traps on traffic jam formation in fast axonal transport.

    Science.gov (United States)

    Kuznetsov, A V

    2010-08-01

    The purpose of this paper is to develop a model for simulation of the formation of organelle traps in fast axonal transport. Such traps may form in the regions of microtubule polar mismatching. Depending on the orientation of microtubules pointing toward the trap region, these traps can accumulate either plus-end or minus-end oriented vesicles. The model predicts that the maximum concentrations of organelles occur at the boundaries of the trap regions; the overall concentration of organelles in the axon with traps is greatly increased compared to that in a healthy axon, which is expected to contribute to mechanical damages of the axon. The organelle traps induce hindrance to organelle transport down the axon; the total organelle flux down the axon with traps is found to be significantly reduced compared to that in a healthy axon.

  16. Axonal transport rate decreased at the onset of optic neuritis in EAE mice.

    Science.gov (United States)

    Lin, Tsen-Hsuan; Kim, Joong Hee; Perez-Torres, Carlos; Chiang, Chia-Wen; Trinkaus, Kathryn; Cross, Anne H; Song, Sheng-Kwei

    2014-10-15

    Optic neuritis is frequently the first symptom of multiple sclerosis (MS), an inflammatory demyelinating neurodegenerative disease. Impaired axonal transport has been considered as an early event of neurodegenerative diseases. However, few studies have assessed the integrity of axonal transport in MS or its animal models. We hypothesize that axonal transport impairment occurs at the onset of optic neuritis in experimental autoimmune encephalomyelitis (EAE) mice. In this study, we employed manganese-enhanced MRI (MEMRI) to assess axonal transport in optic nerves in EAE mice at the onset of optic neuritis. Axonal transport was assessed as (a) optic nerve Mn(2+) accumulation rate (in % signal change/h) by measuring the rate of increased total optic nerve signal enhancement, and (b) Mn(2+) transport rate (in mm/h) by measuring the rate of change in optic nerve length enhanced by Mn(2+). Compared to sham-treated healthy mice, Mn(2+) accumulation rate was significantly decreased by 19% and 38% for EAE mice with moderate and severe optic neuritis, respectively. The axonal transport rate of Mn(2+) was significantly decreased by 43% and 65% for EAE mice with moderate and severe optic neuritis, respectively. The degree of axonal transport deficit correlated with the extent of impaired visual function and diminished microtubule-associated tubulins, as well as the severity of inflammation, demyelination, and axonal injury at the onset of optic neuritis.

  17. Parkinson's disease-associated kinase PINK1 regulates Miro protein level and axonal transport of mitochondria.

    Directory of Open Access Journals (Sweden)

    Song Liu

    Full Text Available Mutations in Pten-induced kinase 1 (PINK1 are linked to early-onset familial Parkinson's disease (FPD. PINK1 has previously been implicated in mitochondrial fission/fusion dynamics, quality control, and electron transport chain function. However, it is not clear how these processes are interconnected and whether they are sufficient to explain all aspects of PINK1 pathogenesis. Here we show that PINK1 also controls mitochondrial motility. In Drosophila, downregulation of dMiro or other components of the mitochondrial transport machinery rescued dPINK1 mutant phenotypes in the muscle and dopaminergic (DA neurons, whereas dMiro overexpression alone caused DA neuron loss. dMiro protein level was increased in dPINK1 mutant but decreased in dPINK1 or dParkin overexpression conditions. In Drosophila larval motor neurons, overexpression of dPINK1 inhibited axonal mitochondria transport in both anterograde and retrograde directions, whereas dPINK1 knockdown promoted anterograde transport. In HeLa cells, overexpressed hPINK1 worked together with hParkin, another FPD gene, to regulate the ubiquitination and degradation of hMiro1 and hMiro2, apparently in a Ser-156 phosphorylation-independent manner. Also in HeLa cells, loss of hMiro promoted the perinuclear clustering of mitochondria and facilitated autophagy of damaged mitochondria, effects previously associated with activation of the PINK1/Parkin pathway. These newly identified functions of PINK1/Parkin and Miro in mitochondrial transport and mitophagy contribute to our understanding of the complex interplays in mitochondrial quality control that are critically involved in PD pathogenesis, and they may explain the peripheral neuropathy symptoms seen in some PD patients carrying particular PINK1 or Parkin mutations. Moreover, the different effects of loss of PINK1 function on Miro protein level in Drosophila and mouse cells may offer one explanation of the distinct phenotypic manifestations of PINK1

  18. Oxidative stress, mitochondrial and proteostasis malfunction in adrenoleukodystrophy: A paradigm for axonal degeneration.

    Science.gov (United States)

    Fourcade, Stéphane; Ferrer, Isidre; Pujol, Aurora

    2015-11-01

    Peroxisomal and mitochondrial malfunction, which are highly intertwined through redox regulation, in combination with defective proteostasis, are hallmarks of the most prevalent multifactorial neurodegenerative diseases-including Alzheimer's (AD) and Parkinson's disease (PD)-and of the aging process, and are also found in inherited conditions. Here we review the interplay between oxidative stress and axonal degeneration, taking as groundwork recent findings on pathomechanisms of the peroxisomal neurometabolic disease adrenoleukodystrophy (X-ALD). We explore the impact of chronic redox imbalance caused by the excess of very long-chain fatty acids (VLCFA) on mitochondrial respiration and biogenesis, and discuss how this impairs protein quality control mechanisms essential for neural cell survival, such as the proteasome and autophagy systems. As consequence, prime molecular targets in the pathogenetic cascade emerge, such as the SIRT1/PGC-1α axis of mitochondrial biogenesis, and the inhibitor of autophagy mTOR. Thus, we propose that mitochondria-targeted antioxidants; mitochondrial biogenesis boosters such as the antidiabetic pioglitazone and the SIRT1 ligand resveratrol; and the autophagy activator temsirolimus, a derivative of the mTOR inhibitor rapamycin, hold promise as disease-modifying therapies for X-ALD.

  19. Abnormal intermediate filament organization alters mitochondrial motility in giant axonal neuropathy fibroblasts.

    Science.gov (United States)

    Lowery, Jason; Jain, Nikhil; Kuczmarski, Edward R; Mahammad, Saleemulla; Goldman, Anne; Gelfand, Vladimir I; Opal, Puneet; Goldman, Robert D

    2016-02-15

    Giant axonal neuropathy (GAN) is a rare disease caused by mutations in the GAN gene, which encodes gigaxonin, an E3 ligase adapter that targets intermediate filament (IF) proteins for degradation in numerous cell types, including neurons and fibroblasts. The cellular hallmark of GAN pathology is the formation of large aggregates and bundles of IFs. In this study, we show that both the distribution and motility of mitochondria are altered in GAN fibroblasts and this is attributable to their association with vimentin IF aggregates and bundles. Transient expression of wild-type gigaxonin in GAN fibroblasts reduces the number of IF aggregates and bundles, restoring mitochondrial motility. Conversely, silencing the expression of gigaxonin in control fibroblasts leads to changes in IF organization similar to that of GAN patient fibroblasts and a coincident loss of mitochondrial motility. The inhibition of mitochondrial motility in GAN fibroblasts is not due to a global inhibition of organelle translocation, as lysosome motility is normal. Our findings demonstrate that it is the pathological changes in IF organization that cause the loss of mitochondrial motility.

  20. Abnormal mitochondrial transport and morphology as early pathological changes in human models of spinal muscular atrophy

    Directory of Open Access Journals (Sweden)

    Chong-Chong Xu

    2016-01-01

    Full Text Available Spinal muscular atrophy (SMA, characterized by specific degeneration of spinal motor neurons, is caused by mutations in the survival of motor neuron 1, telomeric (SMN1 gene and subsequent decreased levels of functional SMN. How the deficiency of SMN, a ubiquitously expressed protein, leads to spinal motor neuron-specific degeneration in individuals affected by SMA remains unknown. In this study, we examined the role of SMN in mitochondrial axonal transport and morphology in human motor neurons by generating SMA type 1 patient-specific induced pluripotent stem cells (iPSCs and differentiating these cells into spinal motor neurons. The initial specification of spinal motor neurons was not affected, but these SMA spinal motor neurons specifically degenerated following long-term culture. Moreover, at an early stage in SMA spinal motor neurons, but not in SMA forebrain neurons, the number of mitochondria, mitochondrial area and mitochondrial transport were significantly reduced in axons. Knocking down of SMN expression led to similar mitochondrial defects in spinal motor neurons derived from human embryonic stem cells, confirming that SMN deficiency results in impaired mitochondrial dynamics. Finally, the application of N-acetylcysteine (NAC mitigated the impairment in mitochondrial transport and morphology and rescued motor neuron degeneration in SMA long-term cultures. Furthermore, NAC ameliorated the reduction in mitochondrial membrane potential in SMA spinal motor neurons, suggesting that NAC might rescue apoptosis and motor neuron degeneration by improving mitochondrial health. Overall, our data demonstrate that SMN deficiency results in abnormal mitochondrial transport and morphology and a subsequent reduction in mitochondrial health, which are implicated in the specific degeneration of spinal motor neurons in SMA.

  1. Abnormal mitochondrial transport and morphology as early pathological changes in human models of spinal muscular atrophy.

    Science.gov (United States)

    Xu, Chong-Chong; Denton, Kyle R; Wang, Zhi-Bo; Zhang, Xiaoqing; Li, Xue-Jun

    2016-01-01

    Spinal muscular atrophy (SMA), characterized by specific degeneration of spinal motor neurons, is caused by mutations in the survival of motor neuron 1, telomeric (SMN1) gene and subsequent decreased levels of functional SMN. How the deficiency of SMN, a ubiquitously expressed protein, leads to spinal motor neuron-specific degeneration in individuals affected by SMA remains unknown. In this study, we examined the role of SMN in mitochondrial axonal transport and morphology in human motor neurons by generating SMA type 1 patient-specific induced pluripotent stem cells (iPSCs) and differentiating these cells into spinal motor neurons. The initial specification of spinal motor neurons was not affected, but these SMA spinal motor neurons specifically degenerated following long-term culture. Moreover, at an early stage in SMA spinal motor neurons, but not in SMA forebrain neurons, the number of mitochondria, mitochondrial area and mitochondrial transport were significantly reduced in axons. Knocking down of SMN expression led to similar mitochondrial defects in spinal motor neurons derived from human embryonic stem cells, confirming that SMN deficiency results in impaired mitochondrial dynamics. Finally, the application of N-acetylcysteine (NAC) mitigated the impairment in mitochondrial transport and morphology and rescued motor neuron degeneration in SMA long-term cultures. Furthermore, NAC ameliorated the reduction in mitochondrial membrane potential in SMA spinal motor neurons, suggesting that NAC might rescue apoptosis and motor neuron degeneration by improving mitochondrial health. Overall, our data demonstrate that SMN deficiency results in abnormal mitochondrial transport and morphology and a subsequent reduction in mitochondrial health, which are implicated in the specific degeneration of spinal motor neurons in SMA.

  2. Neuronal Logistics : Axonal Transport in Development and Disease

    NARCIS (Netherlands)

    R. van den Berg (Robert)

    2016-01-01

    markdownabstractBrain cells are uniquely shaped among the many cell types of the body. While most cells are more or less rounded or square-shaped, neurons grow one or more long axons that can reach lengths of a meter or more. To keep these axons alive and functional, neurons are dependent on an intr

  3. Optic nerve fast axonal transport abnormalities in primates. Occurrence after short posterior ciliary artery occlusion.

    Science.gov (United States)

    Radius, R L

    1980-11-01

    Fast axonal transport abnormalities in primate (Aotus trivirgatus) optic nerve were studied in ten eyes at various intervals after occlusion of the lateral short posterior ciliary circulation. Evidence of focal axonal ischemia, as indicated by swelling of mitochondria and dissolution of cytoplasmic detail, was noted as early as one hour after occlusion. Accumulation of mitochondria, microvesicles, and dense bodies, indicating focal interruption of axonal transport mechanisms, was noted in eyes examined at 2, 4, and 6 hours. This accumulation of organelles was limited to the region of the lamina cribrosa. Nerve head abnormalities were not seen in two eyes studied at two weeks.

  4. In vivo axonal transport deficits in a mouse model of fronto-temporal dementia

    Directory of Open Access Journals (Sweden)

    Tabassum Majid

    2014-01-01

    Discussion: In our study, we identified the presence of age-dependent axonal transport deficits beginning at 3 months of age in rTg4510 mice. We correlated these deficits at 3 months to the presence of hyperphosphorylated tau in the brain and the presence within the olfactory epithelium. We observed tau pathology not only in the soma of these neurons but also within the axons and processes of these neurons. Our characterization of axonal transport in this tauopathy model provides a functional time point that can be used for future therapeutic interventions.

  5. Neurofilament subunit (NFL) head domain phosphorylation regulates axonal transport of neurofilaments.

    LENUS (Irish Health Repository)

    Yates, Darran M

    2009-04-01

    Neurofilaments are the intermediate filaments of neurons and are synthesised in neuronal cell bodies and then transported through axons. Neurofilament light chain (NFL) is a principal component of neurofilaments, and phosphorylation of NFL head domain is believed to regulate the assembly of neurofilaments. However, the role that NFL phosphorylation has on transport of neurofilaments is poorly understood. To address this issue, we monitored axonal transport of phosphorylation mutants of NFL. We mutated four known phosphorylation sites in NFL head domain to either preclude phosphorylation, or mimic permanent phosphorylation. Mutation to preclude phosphorylation had no effect on transport but mutation of three sites to mimic permanent phosphorylation inhibited transport. Mutation of all four sites together to mimic permanent phosphorylation proved especially potent at inhibiting transport and also disrupted neurofilament assembly. Our results suggest that NFL head domain phosphorylation is a regulator of neurofilament axonal transport.

  6. Mitochondrial swelling impairs the transport of organelles in cerebellar granule neurons.

    Science.gov (United States)

    Kaasik, Allen; Safiulina, Dzhamilja; Choubey, Vinay; Kuum, Malle; Zharkovsky, Alexander; Veksler, Vladimir

    2007-11-09

    Organelle transport in neuronal processes is central to the organization, developmental fate, and functions of neurons. Organelles must be transported through the slender, highly branched neuronal processes, making the axonal transport vulnerable to any perturbation. However, some intracellular structures like mitochondria are able to considerably modify their volume. We therefore hypothesized that swollen mitochondria could impair the traffic of other organelles in neurite shafts. To test this hypothesis, we have investigated the effects of mitochondrial swellers on the organelle traffic. Our data demonstrate that treatment of neurons with potassium ionophore valinomycin led to the fast time-dependent inhibition of organelle movement in cerebellar granule neurons. Similar inhibition was observed in neurons treated with the inhibitors of the mitochondrial respiratory chain, sodium azide and antimycin, which also induced swelling. No decrease in the motility of organelles was observed in cultures treated with inhibitors of ATP production or transport, oligomycin or bongkrekic acid, suggesting that inhibition of the ATP-generating activity itself without swelling does not affect the motility of organelles. The effect of swellers on the traffic was more important in thin processes, thus indicating the role of steric hindrance of swollen mitochondria. We propose that the size and morphology of the transported cargo is also relevant for seamless axonal transport and speculate that mitochondrial swelling could be one of the reasons for impaired organelle transport in neuronal processes.

  7. Abnormal mitochondrial transport and morphology are common pathological denominators in SOD1 and TDP43 ALS mouse models.

    Science.gov (United States)

    Magrané, Jordi; Cortez, Czrina; Gan, Wen-Biao; Manfredi, Giovanni

    2014-03-15

    Neuronal mitochondrial morphology abnormalities occur in models of familial amyotrophic lateral sclerosis (ALS) associated with SOD1 and TDP43 mutations. These abnormalities have been linked to mitochondrial axonal transport defects, but the temporal and spatial relationship between mitochondrial morphology and transport alterations in these two distinct genetic forms of ALS has not been investigated in vivo. To address this question, we crossed SOD1 (wild-type SOD1(WT) and mutant SOD1(G93A)) or TDP43 (mutant TDP43(A315T)) transgenic mice with mice expressing the fluorescent protein Dendra targeted to mitochondria in neurons (mitoDendra). At different time points during the disease course, we studied mitochondrial transport in the intact sciatic nerve of living mice and analyzed axonal mitochondrial morphology at multiple sites, spanning from the spinal cord to the motor terminals. Defects of retrograde mitochondrial transport were detected at 45 days of age, before the onset of symptoms, in SOD1(G93A) and TDP43(A315T) mice, but not in SOD1(WT). At later disease stages, also anterograde mitochondrial transport was affected in both mutant mouse lines. In SOD1(G93A) mice, mitochondrial morphological abnormalities were apparent at 15 days of age, thus preceding transport abnormalities. Conversely, in TDP43(A315T) mice, morphological abnormalities appeared after the onset of transport defects. Taken together, these findings demonstrate that neuronal mitochondrial transport and morphology abnormalities occur in vivo and that they are common denominators of different genetic forms of the ALS. At the same time, differences in the temporal and spatial manifestation of mitochondrial abnormalities between the two mouse models of familial ALS imply that different molecular mechanisms may be involved.

  8. Impaired axonal transport in motor neurons correlates with clinical prion disease.

    Directory of Open Access Journals (Sweden)

    Vladimir Ermolayev

    2009-08-01

    Full Text Available Prion diseases are fatal neurodegenerative disorders causing motor dysfunctions, dementia and neuropathological changes such as spongiosis, astroglyosis and neuronal loss. The chain of events leading to the clinical disease and the role of distinct brain areas are still poorly understood. The role of nervous system integrity and axonal properties in prion pathology are still elusive. There is no evidence of both the functional axonal impairments in vivo and their connection with prion disease. We studied the functional axonal impairments in motor neurons at the onset of clinical prion disease using the combination of tracing as a functional assay for axonal transport with immunohistochemistry experiments. Well-established and novel confocal and ultramicroscopy techniques were used to image and quantify labeled neurons. Despite profound differences in the incubation times, 30% to 45% of neurons in the red nucleus of different mouse lines showed axonal transport impairments at the disease onset bilaterally after intracerebral prion inoculation and unilaterally -- after inoculation into the right sciatic nerve. Up to 94% of motor cortex neurons also demonstrated transport defects upon analysis by alternative imaging methods. Our data connect axonal transport impairments with disease symptoms for different prion strains and inoculation routes and establish further insight on the development of prion pathology in vivo. The alterations in localization of the proteins involved in the retrograde axonal transport allow us to propose a mechanism of transport disruption, which involves Rab7-mediated cargo attachment to the dynein-dynactin pathway. These findings suggest novel targets for therapeutic and diagnostic approaches in the early stages of prion disease.

  9. Difference Tracker: ImageJ plugins for fully automated analysis of multiple axonal transport parameters.

    Science.gov (United States)

    Andrews, Simon; Gilley, Jonathan; Coleman, Michael P

    2010-11-30

    Studies of axonal transport are critical, not only to understand its normal regulation, but also to determine the roles of transport impairment in disease. Exciting new resources have recently become available allowing live imaging of axonal transport in physiologically relevant settings, such as mammalian nerves. Thus the effects of disease, ageing and therapies can now be assessed directly in nervous system tissue. However, these imaging studies present new challenges. Manual or semi-automated analysis of the range of transport parameters required for a suitably complete evaluation is very time-consuming and can be subjective due to the complexity of the particle movements in axons in ex vivo explants or in vivo. We have developed Difference Tracker, a program combining two new plugins for the ImageJ image-analysis freeware, to provide fast, fully automated and objective analysis of a number of relevant measures of trafficking of fluorescently labeled particles so that axonal transport in different situations can be easily compared. We confirm that Difference Tracker can accurately track moving particles in highly simplified, artificial simulations. It can also identify and track multiple motile fluorescently labeled mitochondria simultaneously in time-lapse image stacks from live imaging of tibial nerve axons, reporting values for a number of parameters that are comparable to those obtained through manual analysis of the same axons. Difference Tracker therefore represents a useful free resource for the comparative analysis of axonal transport under different conditions, and could potentially be used and developed further in many other studies requiring quantification of particle movements.

  10. In vitro low frequency electromagnetic field effect on fast axonal transport.

    Science.gov (United States)

    Zborowski, M; Atkinson, M; Lewandowski, J J; Jacobs, G; Mitchell, D; Breuer, A C; Nosé, Y

    1988-01-01

    The objective of this study was to evaluate the effects of a low frequency electromagnetic field on fast axonal transport for future neuroprosthetic applications. Changes in speeds and densities of retrograde fast organelle transport in rat sciatic nerve preparations were measured in vitro upon exposure to 15 and 50 Hz pulsed magnetic fields with peak intensities of 4.4 and 8.8 mT. Maximum current density of the induced eddy current was calculated to be about 40 microA/cm2. Video enhanced differential interference contrast microscopy was used to record axons supporting active organelle transport. Strong effects were observed in myelinated axons (cessation of transport in up to 10 min). Such effects may eventually be used as part of a neuroprosthesis to noninvasively modify or couple to various parts of the nervous system.

  11. Cryo electron tomography of herpes simplex virus during axonal transport and secondary envelopment in primary neurons.

    Directory of Open Access Journals (Sweden)

    Iosune Ibiricu

    2011-12-01

    Full Text Available During herpes simplex virus 1 (HSV1 egress in neurons, viral particles travel from the neuronal cell body along the axon towards the synapse. Whether HSV1 particles are transported as enveloped virions as proposed by the 'married' model or as non-enveloped capsids suggested by the 'separate' model is controversial. Specific viral proteins may form a recruitment platform for microtubule motors that catalyze such transport. However, their subviral location has remained elusive. Here we established a system to analyze herpesvirus egress by cryo electron tomography. At 16 h post infection, we observed intra-axonal transport of progeny HSV1 viral particles in dissociated hippocampal neurons by live-cell fluorescence microscopy. Cryo electron tomography of frozen-hydrated neurons revealed that most egressing capsids were transported independently of the viral envelope. Unexpectedly, we found not only DNA-containing capsids (cytosolic C-capsids, but also capsids lacking DNA (cytosolic A-/B-capsids in mid-axon regions. Subvolume averaging revealed lower amounts of tegument on cytosolic A-/B-capsids than on C-capsids. Nevertheless, all capsid types underwent active axonal transport. Therefore, even few tegument proteins on the capsid vertices seemed to suffice for transport. Secondary envelopment of capsids was observed at axon terminals. On their luminal face, the enveloping vesicles were studded with typical glycoprotein-like spikes. Furthermore, we noted an accretion of tegument density at the concave cytosolic face of the vesicle membrane in close proximity to the capsids. Three-dimensional analysis revealed that these assembly sites lacked cytoskeletal elements, but that filamentous actin surrounded them and formed an assembly compartment. Our data support the 'separate model' for HSV1 egress, i.e. progeny herpes viruses being transported along axons as subassemblies and not as complete virions within transport vesicles.

  12. Mitochondrial abnormality in sensory, but not motor, axons in paclitaxel-evoked painful peripheral neuropathy in the rat.

    Science.gov (United States)

    Xiao, W H; Zheng, H; Zheng, F Y; Nuydens, R; Meert, T F; Bennett, G J

    2011-12-29

    The dose-limiting side effect of the anti-neoplastic agent, paclitaxel, is a chronic distal symmetrical peripheral neuropathy that produces sensory dysfunction (hypoesthesia and neuropathic pain) but little or no distal motor dysfunction. Similar peripheral neuropathies are seen with chemotherapeutics in the vinca alkaloid, platinum-complex, and proteasome inhibitor classes. Studies in rats suggest that the cause is a mitotoxic effect on axonal mitochondria. If so, then the absence of motor dysfunction may be due to mitotoxicity that affects sensory axons but spares motor axons. To investigate this, paclitaxel exposure levels in the dorsal root, ventral root, dorsal root ganglion, peripheral nerve, and spinal cord were measured, and the ultrastructure and the respiratory function of mitochondria in dorsal roots and ventral roots were compared. Sensory and motor axons in the roots and nerve had comparably low exposure to paclitaxel and exposure in the spinal cord was negligible. However, sensory neurons in the dorsal root ganglion had a very high and remarkably persistent (up to 10 days or more after the last injection) exposure to paclitaxel. Paclitaxel evoked a significant increase in the incidence of swollen and vacuolated mitochondria in the myelinated and unmyelinated sensory axons of the dorsal root (as seen previously in the peripheral nerve) but not in the motor axons of the ventral root. Stimulated mitochondrial respiration in the dorsal root was significantly depressed in paclitaxel-treated animals examined 2-4 weeks after the last injection, whereas respiration in the ventral root was normal. We conclude that the absence of motor dysfunction in paclitaxel-evoked peripheral neuropathy may be due to the absence of a mitotoxic effect in motor neuron axons, whereas the sensory dysfunction may be due to a mitotoxic effect resulting from the primary afferent neuron's cell body being exposed to high and persistent levels of paclitaxel.

  13. Morphology of axonal transport abnormalities in primate eyes.

    OpenAIRE

    Radius, R L; Anderson, D. R.

    1981-01-01

    The ultrastructure of the retina and optic nerve head was studied in primate eyes after central retinal artery occlusion. Within 2 hours of the vascular occlusion the inner retinal layers undergo watery (isosmotic) swelling. This watery swelling of axons and astroglia extends into the nerve head as far back as the anterior boundary of the scleral lamina cribrosa. The swelling is increased 4 hours after the occlusion, and by 24 hours disintegration has occurred. At the optic nerve head mitocho...

  14. Tri-partite complex for axonal transport drug delivery achieves pharmacological effect

    Directory of Open Access Journals (Sweden)

    Frederickson Martyn

    2010-01-01

    Full Text Available Abstract Background Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior. Results We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle. Conclusion Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal

  15. CAR-associated vesicular transport of an adenovirus in motor neuron axons.

    Science.gov (United States)

    Salinas, Sara; Bilsland, Lynsey G; Henaff, Daniel; Weston, Anne E; Keriel, Anne; Schiavo, Giampietro; Kremer, Eric J

    2009-05-01

    Axonal transport is responsible for the movement of signals and cargo between nerve termini and cell bodies. Pathogens also exploit this pathway to enter and exit the central nervous system. In this study, we characterised the binding, endocytosis and axonal transport of an adenovirus (CAV-2) that preferentially infects neurons. Using biochemical, cell biology, genetic, ultrastructural and live-cell imaging approaches, we show that interaction with the neuronal membrane correlates with coxsackievirus and adenovirus receptor (CAR) surface expression, followed by endocytosis involving clathrin. In axons, long-range CAV-2 motility was bidirectional with a bias for retrograde transport in nonacidic Rab7-positive organelles. Unexpectedly, we found that CAR was associated with CAV-2 vesicles that also transported cargo as functionally distinct as tetanus toxin, neurotrophins, and their receptors. These results suggest that a single axonal transport carrier is capable of transporting functionally distinct cargoes that target different membrane compartments in the soma. We propose that CAV-2 transport is dictated by an innate trafficking of CAR, suggesting an unsuspected function for this adhesion protein during neuronal homeostasis.

  16. Effect of the degree of polar mismatching on traffic jam formation in fast axonal transport.

    Science.gov (United States)

    Kuznetsov, A V

    2010-12-01

    This paper simulates an axon with a region of reversed microtubule (MT) polarity, and investigates how the degree of polar mismatching in this region affects the formation of organelle traps in the axon. The model is based on modified Smith-Simmons equations governing molecular-motor-assisted transport in neurons. It is established that the structure that develops as a result of a region with disoriented MTs consists of two organelle traps, the trap to the left of this region accumulates plus-end-oriented organelles and the trap to the right of this region accumulates minus-end-oriented organelles. The presence of such a structure is shown to inhibit the transport of organelles down the axon. The degree by which the transport of organelles is inhibited depends on the degree of polar mismatching of MTs in the region between MT traps. Four cases with a different degree of polar mismatching are investigated.

  17. Clinical pathological and genetic analysis of 2 cases of mitochondrial myopathy presented as acute motor axonal neuropathy

    Directory of Open Access Journals (Sweden)

    Hou-min YIN

    2014-06-01

    Full Text Available Background The main clinical manifestations of mitochondrial myopathy are chronic limb weakness and muscular soreness. Subclinical peripheral nerve injury is also reported, but acute axonal neuropathy.like syndrome concurrent with lactic acidosis is rare. In this paper the clinical features of 2 patients presenting as acute lactic acidosis and sudden muscle weakness were analyzed. Pathological changes and genetic mutations were detected.  Methods Electromyography (EMG and muscle biopsy were performed. Modified Gomori trichrome (MGT and succinodehydrogenase (SDH staining were used to identify pathological changes. Changes of ultra microstructure of muscular tissue were observed under electron microscope. Mitochondrial DNA (mtDNA full length sequencing was performed using 24 pairs of partially overlapping primers.  Results EMG showed a coexistence of neurogenic and myogenic changes. Dramatic decrease of motor nerve amplitude and moderately reduced sensory nerve amplitude were observed but nerve conduction velocity was normal in both patients. Impressive ragged red fibers were seen on MGT staining. Electron microscope showed dramatic mitochondrial abnormalities in Case 1 and paracrystaline inclusions in Case 2. mtDNA sequencing showed 3243A > G mutation in Case 1 and 8344A > G mutation in Case 2. Conclusions Mitochondrial myopathy can present as metabolic crisis like acute lactic acidosis, dyspnea and acute motor axonal neuropathy.like syndrome. It is a life.threatening phenotype that needs more attention. doi: 10.3969/j.issn.1672-6731.2014.06.007

  18. 4-Hydroxy-2-nonenal induces mitochondrial dysfunction and aberrant axonal outgrowth in adult sensory neurons that mimics features of diabetic neuropathy.

    Science.gov (United States)

    Akude, Eli; Zherebitskaya, Elena; Roy Chowdhury, Subir K; Girling, Kimberly; Fernyhough, Paul

    2010-01-01

    Modification of proteins by 4-hydroxy-2-nonenal (4-HNE) has been proposed to cause neurotoxicity in a number of neurodegenerative diseases, including distal axonopathy in diabetic sensory neuropathy. We tested the hypothesis that exposure of cultured adult rat sensory neurons to 4-HNE would result in the formation of amino acid adducts on mitochondrial proteins and that this process would be associated with impaired mitochondrial function and axonal regeneration. In addition, we compared 4-HNE-induced axon pathology with that exhibited by neurons isolated from diabetic rats. Cultured adult rat dorsal root ganglion (DRG) sensory neurons were incubated with varying concentrations of 4-HNE. Cell survival, axonal morphology, and level of axon outgrowth were assessed. In addition, video microscopy of live cells, western blot, and immunofluorescent staining were utilized to detect protein adduct formation by 4-HNE and to localize actively respiring mitochondria. 4-HNE induced formation of protein adducts on cytoskeletal and mitochondrial proteins, and impaired axon regeneration by approximately 50% at 3 microM while having no effect on neuronal survival. 4-HNE initiated formation of aberrant axonal structures and caused the accumulation of mitochondria in these dystrophic structures. Neurons treated with 4-HNE exhibited a distal loss of active mitochondria. Finally, the distal axonopathy and the associated aberrant axonal structures generated by 4-HNE treatment mimicked axon pathology observed in DRG sensory neurons isolated from diabetic rats and replicated aspects of neurodegeneration observed in human diabetic sensory neuropathy.

  19. A simple method for imaging axonal transport in aging neurons using the adult Drosophila wing.

    Science.gov (United States)

    Vagnoni, Alessio; Bullock, Simon L

    2016-09-01

    There is growing interest in the link between axonal cargo transport and age-associated neuronal dysfunction. The study of axonal transport in neurons of adult animals requires intravital or ex vivo imaging approaches, which are laborious and expensive in vertebrate models. We describe simple, noninvasive procedures for imaging cargo motility within axons using sensory neurons of the translucent Drosophila wing. A key aspect is a method for mounting the intact fly that allows detailed imaging of transport in wing neurons. Coupled with existing genetic tools in Drosophila, this is a tractable system for studying axonal transport over the life span of an animal and thus for characterization of the relationship between cargo dynamics, neuronal aging and disease. Preparation of a sample for imaging takes ∼5 min, with transport typically filmed for 2-3 min per wing. We also document procedures for the quantification of transport parameters from the acquired images and describe how the protocol can be adapted to study other cell biological processes in aging neurons.

  20. Kinesin I transports tetramerized Kv3 channels through the axon initial segment via direct binding.

    Science.gov (United States)

    Xu, Mingxuan; Gu, Yuanzheng; Barry, Joshua; Gu, Chen

    2010-11-24

    Precise targeting of various voltage-gated ion channels to proper membrane domains is crucial for their distinct roles in neuronal excitability and synaptic transmission. How each channel protein is transported within the cytoplasm is poorly understood. Here, we report that KIF5/kinesin I transports Kv3.1 voltage-gated K(+) (Kv) channels through the axon initial segment (AIS) via direct binding. First, we have identified a novel interaction between Kv3.1 and KIF5, confirmed by immunoprecipitation from mouse brain lysates and by pull-down assays with exogenously expressed proteins. The interaction is mediated by a direct binding between the Kv3.1 N-terminal T1 domain and a conserved region in KIF5 tail domains, in which proper T1 tetramerization is crucial. Overexpression of this region of KIF5B markedly reduces axonal levels of Kv3.1bHA. In mature hippocampal neurons, endogenous Kv3.1b and KIF5 colocalize. Suppressing the endogenous KIF5B level by RNA interference significantly reduces the Kv3.1b axonal level. Furthermore, mutating the Zn(2+)-binding site within T1 markedly decreases channel axonal targeting and forward trafficking, likely through disrupting T1 tetramerization and hence eliminating the binding to KIF5 tail. The mutation also alters channel activity. Interestingly, coexpression of the YFP (yellow fluorescent protein)-tagged KIF5B assists dendritic Kv3.1a and even mutants with a faulty axonal targeting motif to penetrate the AIS. Finally, fluorescently tagged Kv3.1 channels colocalize and comove with KIF5B along axons revealed by two-color time-lapse imaging. Our findings suggest that the binding to KIF5 ensures properly assembled and functioning Kv3.1 channels to be transported into axons.

  1. Tracking Quantum-Dot labeled neurotropic factors transport along primary neuronal axons in compartmental microfluidic chambers.

    Science.gov (United States)

    Gluska, Shani; Chein, Michael; Rotem, Nimrod; Ionescu, Ariel; Perlson, Eran

    2016-01-01

    Neurons are highly polarized cells, with very long axons. Neurotrophic factors like the neuronal growth factor (NGF) are secreted from neuronal targets to promote neuron survival and proper function. These neurotrophic factors must undergo retrograde axonal transport towards the cell body, wherein they initiate signaling pathways important for neurons' various functions and overall health. This process of long-distance axonal signaling is conducted by the dynein motor protein, which transmits signaling endosomes of ligand-receptor complexes retrogradely along microtubule tracks. Here we describe step by step the use of polydimethylsiloxane (PDMS) compartmentalized microfluidic chambers for tracking axonal transport of trophic factors, with a focus on labeled NGF. We describe in detail how to fabricate the molds, assemble the PDMS platform, plate neurons and image, as well as analyze NGF transport along the axon. This method is useful for studying molecular communication mechanisms within the neuron's different compartments as well as between the neuron and its diverse microenvironments, both in health and under pathological conditions.

  2. Mitochondrial Electron Transport and Plant Stress

    DEFF Research Database (Denmark)

    Rasmusson, Allan G; Møller, Ian Max

    2011-01-01

    redox compounds from carbon degradation are used for powering ATP synthesis. The standard ETC contains three sites of energy conservation in complexes I, III, and IV, which are in common with most other eukaryotes. However, the complexity of the plant metabolic system is mirrored in the ETC. In addition...... conservation in the ETC. The alternative oxidase provides a non-energy-conserving alternative to electron transport through complexes III and IV. There also appears to be a special coupling between specific NAD(P)H dehydrogenases and specific members of the alternative oxidase family. These additional enzymes...... therefore give a great flexibility in the type and origin of the substrate, the electron transport route(s) used, and the energy yield. At the same time special reactions, such as ascorbate biosynthesis, can take place. In this way, the mitochondrial ETC can mediate major adjustments in cellular metabolism...

  3. Novel RNA- and FMRP-binding protein TRF2-S regulates axonal mRNA transport and presynaptic plasticity.

    Science.gov (United States)

    Zhang, Peisu; Abdelmohsen, Kotb; Liu, Yong; Tominaga-Yamanaka, Kumiko; Yoon, Je-Hyun; Ioannis, Grammatikakis; Martindale, Jennifer L; Zhang, Yongqing; Becker, Kevin G; Yang, In Hong; Gorospe, Myriam; Mattson, Mark P

    2015-11-20

    Despite considerable evidence that RNA-binding proteins (RBPs) regulate mRNA transport and local translation in dendrites, roles for axonal RBPs are poorly understood. Here we demonstrate that a non-telomeric isoform of telomere repeat-binding factor 2 (TRF2-S) is a novel RBP that regulates axonal plasticity. TRF2-S interacts directly with target mRNAs to facilitate their axonal delivery. The process is antagonized by fragile X mental retardation protein (FMRP). Distinct from the current RNA-binding model of FMRP, we show that FMRP occupies the GAR domain of TRF2-S protein to block the assembly of TRF2-S-mRNA complexes. Overexpressing TRF2-S and silencing FMRP promotes mRNA entry to axons and enhances axonal outgrowth and neurotransmitter release from presynaptic terminals. Our findings suggest a pivotal role for TRF2-S in an axonal mRNA localization pathway that enhances axon outgrowth and neurotransmitter release.

  4. Mitochondrial lipid transport and biosynthesis: A complex balance

    Science.gov (United States)

    2016-01-01

    Little is known about how mitochondrial lipids reach inner membrane–localized metabolic enzymes for phosphatidylethanolamine synthesis. Aaltonen et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201602007) and Miyata et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201601082) now report roles for two mitochondrial complexes, Ups2–Mdm35 and mitochondrial contact site and cristae organizing system, in the biosynthesis and transport of mitochondrial lipids. PMID:27354376

  5. Loss of fractalkine signaling exacerbates axon transport dysfunction in a chronic model of glaucoma

    Directory of Open Access Journals (Sweden)

    Kevin T Breen

    2016-11-01

    Full Text Available Neurodegeneration in glaucoma results in decline and loss of retinal ganglion cells (RGCs, and is associated with activation of myeloid cells such as microglia and macrophages. The chemokine fractalkine (FKN or Cx3cl1 mediates communication from neurons to myeloid cells. Signaling through its receptor Cx3cr1 has been implicated in multiple neurodegenerative diseases, but the effects on neuronal pathology are variable. Since it is unknown how FKN-mediated crosstalk influences RGC degeneration in glaucoma, we assessed this in a chronic mouse model, DBA/2J. We analyzed a DBA/2J substrain deficient in Cx3cr1, and compared compartmentalized RGC degeneration and myeloid cell responses to those in standard DBA/2J mice. We found that loss of FKN signaling exacerbates axon transport dysfunction, an early event in neurodegeneration, with a significant increase in RGCs with somal accumulation of the axonal protein phosphorylated neurofilament, and reduced retinal expression of genes involved in axon transport, Kif1b and Atp8a2. There was no change in the loss of Brn3-positive RGCs, and no difference in the extent of damage to the proximal optic nerve, suggesting that the loss of fractalkine signaling primarily affects axon transport. Since Cx3cr1 is specifically expressed in myeloid cells, we assessed changes in retinal microglial number and activation, changes in gene expression, and the extent of macrophage infiltration. We found that loss of fractalkine signaling led to innate immune changes within the retina, including increased infiltration of peripheral macrophages and upregulated nitric oxide synthase-2 (Nos-2 expression in myeloid cells, which contributes to the production of NO and can promote axon transport deficits. In contrast, resident retinal microglia appeared unchanged either in number, morphology, or expression of the myeloid activation marker ionized calcium binding adaptor molecule 1 (Iba1. There was also no significant increase in the

  6. Non-Cell-Autonomous Regulation of Retrograde Motoneuronal Axonal Transport in an SBMA Mouse Model.

    Science.gov (United States)

    Halievski, Katherine; Kemp, Michael Q; Breedlove, S Marc; Miller, Kyle E; Jordan, Cynthia L

    2016-01-01

    Defects in axonal transport are seen in motoneuronal diseases, but how that impairment comes about is not well understood. In spinal bulbar muscular atrophy (SBMA), a disorder linked to a CAG/polyglutamine repeat expansion in the androgen receptor (AR) gene, the disease-causing AR disrupts axonal transport by acting in both a cell-autonomous fashion in the motoneurons themselves, and in a non-cell-autonomous fashion in muscle. The non-cell-autonomous mechanism is suggested by data from a unique "myogenic" transgenic (TG) mouse model in which an AR transgene expressed exclusively in skeletal muscle fibers triggers an androgen-dependent SBMA phenotype, including defects in retrograde transport. However, motoneurons in this TG model retain the endogenous AR gene, leaving open the possibility that impairments in transport in this model also depend on ARs in the motoneurons themselves. To test whether non-cell-autonomous mechanisms alone can perturb retrograde transport, we generated male TG mice in which the endogenous AR allele has the testicular feminization mutation (Tfm) and, consequently, is nonfunctional. Males carrying the Tfm allele alone show no deficits in motor function or axonal transport, with or without testosterone treatment. However, when Tfm males carrying the myogenic transgene (Tfm/TG) are treated with testosterone, they develop impaired motor function and defects in retrograde transport, having fewer retrogradely labeled motoneurons and deficits in endosomal flux based on time-lapse video microscopy of living axons. These findings demonstrate that non-cell-autonomous disease mechanisms originating in muscle are sufficient to induce defects in retrograde transport in motoneurons.

  7. Rabies Virus Hijacks and accelerates the p75NTR retrograde axonal transport machinery.

    Science.gov (United States)

    Gluska, Shani; Zahavi, Eitan Erez; Chein, Michael; Gradus, Tal; Bauer, Anja; Finke, Stefan; Perlson, Eran

    2014-08-01

    Rabies virus (RABV) is a neurotropic virus that depends on long distance axonal transport in order to reach the central nervous system (CNS). The strategy RABV uses to hijack the cellular transport machinery is still not clear. It is thought that RABV interacts with membrane receptors in order to internalize and exploit the endosomal trafficking pathway, yet this has never been demonstrated directly. The p75 Nerve Growth Factor (NGF) receptor (p75NTR) binds RABV Glycoprotein (RABV-G) with high affinity. However, as p75NTR is not essential for RABV infection, the specific role of this interaction remains in question. Here we used live cell imaging to track RABV entry at nerve terminals and studied its retrograde transport along the axon with and without the p75NTR receptor. First, we found that NGF, an endogenous p75NTR ligand, and RABV, are localized in corresponding domains along nerve tips. RABV and NGF were internalized at similar time frames, suggesting comparable entry machineries. Next, we demonstrated that RABV could internalize together with p75NTR. Characterizing RABV retrograde movement along the axon, we showed the virus is transported in acidic compartments, mostly with p75NTR. Interestingly, RABV is transported faster than NGF, suggesting that RABV not only hijacks the transport machinery but can also manipulate it. Co-transport of RABV and NGF identified two modes of transport, slow and fast, that may represent a differential control of the trafficking machinery by RABV. Finally, we determined that p75NTR-dependent transport of RABV is faster and more directed than p75NTR-independent RABV transport. This fast route to the neuronal cell body is characterized by both an increase in instantaneous velocities and fewer, shorter stops en route. Hence, RABV may employ p75NTR-dependent transport as a fast mechanism to facilitate movement to the CNS.

  8. Rabies Virus Hijacks and accelerates the p75NTR retrograde axonal transport machinery.

    Directory of Open Access Journals (Sweden)

    Shani Gluska

    2014-08-01

    Full Text Available Rabies virus (RABV is a neurotropic virus that depends on long distance axonal transport in order to reach the central nervous system (CNS. The strategy RABV uses to hijack the cellular transport machinery is still not clear. It is thought that RABV interacts with membrane receptors in order to internalize and exploit the endosomal trafficking pathway, yet this has never been demonstrated directly. The p75 Nerve Growth Factor (NGF receptor (p75NTR binds RABV Glycoprotein (RABV-G with high affinity. However, as p75NTR is not essential for RABV infection, the specific role of this interaction remains in question. Here we used live cell imaging to track RABV entry at nerve terminals and studied its retrograde transport along the axon with and without the p75NTR receptor. First, we found that NGF, an endogenous p75NTR ligand, and RABV, are localized in corresponding domains along nerve tips. RABV and NGF were internalized at similar time frames, suggesting comparable entry machineries. Next, we demonstrated that RABV could internalize together with p75NTR. Characterizing RABV retrograde movement along the axon, we showed the virus is transported in acidic compartments, mostly with p75NTR. Interestingly, RABV is transported faster than NGF, suggesting that RABV not only hijacks the transport machinery but can also manipulate it. Co-transport of RABV and NGF identified two modes of transport, slow and fast, that may represent a differential control of the trafficking machinery by RABV. Finally, we determined that p75NTR-dependent transport of RABV is faster and more directed than p75NTR-independent RABV transport. This fast route to the neuronal cell body is characterized by both an increase in instantaneous velocities and fewer, shorter stops en route. Hence, RABV may employ p75NTR-dependent transport as a fast mechanism to facilitate movement to the CNS.

  9. DRP1 inhibition rescues retinal ganglion cells and their axons by preserving mitochondrial integrity in a mouse model of glaucoma.

    Science.gov (United States)

    Kim, K-Y; Perkins, G A; Shim, M S; Bushong, E; Alcasid, N; Ju, S; Ellisman, M H; Weinreb, R N; Ju, W-K

    2015-08-06

    Glaucoma is the leading cause of irreversible blindness and is characterized by slow and progressive degeneration of the optic nerve head axons and retinal ganglion cell (RGC), leading to loss of visual function. Although oxidative stress and/or alteration of mitochondrial (mt) dynamics induced by elevated intraocular pressure (IOP) are associated with this neurodegenerative disease, the mechanisms that regulate mt dysfunction-mediated glaucomatous neurodegeneration are poorly understood. Using a mouse model of glaucoma, DBA/2J (D2), which spontaneously develops elevated IOP, as well as an in vitro RGC culture system, we show here that oxidative stress, as evidenced by increasing superoxide dismutase 2 (SOD2) and mt transcription factor A (Tfam) protein expression, triggers mt fission and loss by increasing dynamin-related protein 1 (DRP1) in the retina of glaucomatous D2 mice as well as in cultured RGCs exposed to elevated hydrostatic pressure in vitro. DRP1 inhibition by overexpressing DRP1 K38A mutant blocks mt fission and triggers a subsequent reduction of oxidative stress, as evidenced by decreasing SOD2 and Tfam protein expression. DRP1 inhibition promotes RGC survival by increasing phosphorylation of Bad at serine 112 in the retina and preserves RGC axons by maintaining mt integrity in the glial lamina of glaucomatous D2 mice. These findings demonstrate an important vicious cycle involved in glaucomatous neurodegeneration that starts with elevated IOP producing oxidative stress; the oxidative stress then leads to mt fission and a specific form of mt dysfunction that generates further oxidative stress, thus perpetuating the cycle. Our findings suggest that DRP1 is a potential therapeutic target for ameliorating oxidative stress-mediated mt fission and dysfunction in RGC and its axons during glaucomatous neurodegeneration. Thus, DRP1 inhibition may provide a new therapeutic strategy for protecting both RGCs and their axons in glaucoma and other optic

  10. Calsyntenin-1 shelters APP from proteolytic processing during anterograde axonal transport

    Directory of Open Access Journals (Sweden)

    Martin Steuble

    2012-06-01

    Endocytosis of amyloid-β precursor protein (APP is thought to represent the major source of substrate for the production of the amyloidogenic Aβ peptide by the β-secretase BACE1. The irreversible nature of proteolytic cleavage implies the existence of an efficient replenishment route for APP from its sites of synthesis to the cell surface. We recently found that APP exits the trans-Golgi network in intimate association with calsyntenin-1, a transmembrane cargo-docking protein for Kinesin-1-mediated vesicular transport. Here we characterized the function of calsyntenin-1 in neuronal APP transport using selective immunoisolation of intracellular trafficking organelles, immunocytochemistry, live-imaging, and RNAi. We found that APP is co-transported with calsyntenin-1 along axons to early endosomes in the central region of growth cones in carriers that exclude the α-secretase ADAM10. Intriguingly, calsyntenin-1/APP organelles contained BACE1, suggesting premature cleavage of APP along its anterograde path. However, we found that APP contained in calsyntenin-1/APP organelles was stable. We further analyzed vesicular trafficking of APP in cultured hippocampal neurons, in which calsyntenin-1 was reduced by RNAi. We found a markedly increased co-localization of APP and ADAM10 in axons and growth cones, along with increased proteolytic processing of APP and Aβ secretion in these neurons. This suggested that the reduced capacity for calsyntenin-1-dependent APP transport resulted in mis-sorting of APP into additional axonal carriers and, therefore, the premature encounter of unprotected APP with its ectodomain proteases. In combination, our results characterize calsyntenin-1/APP organelles as carriers for sheltered anterograde axonal transport of APP.

  11. Mitochondrial Ca2+ transport and permeability transition pore opening and mitochondrial energetic status

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The relationship between mitochondrial Ca2+ transport and permeability transition pore (PTP) opening as well as the effects of mitochondrial energetic status on mitochondrial Ca2+ transport and PTP opening were studied. The results showed that the calcium-induced calcium release from mitochondria (mCICR) induced PTP opening. Inhibitors for electron transport of respiratory chain inhibited mCICR and PTP opening. Partial recovery of electron transport in respiratory chain resulted in partial recovery of mCICR and PTP opening. mCICR and PTP opening were also inhibited by CCCP which eliminated transmembrane proton gradient. The results indicated that mitochondrial Ca2+ transport and PTP opening are largely dependent on electron transport and energy coupling.

  12. Mitochondrial Ca2+ transport and permeability transition pore opening and mitochondrial energetic status

    Institute of Scientific and Technical Information of China (English)

    黄行许; 翟大勇; 黄有国; 杨福愉

    2000-01-01

    The relationship between mitochondrial Ca2+ transport and permeability transition pore (PTP) opening as well as the effects of mitochondrial energetic status on mitochondrial Ca2+ transport and PTP opening were studied. The results showed that the calcium-induced calcium release from mitochondria (mClCR) induced PTP opening. Inhibitors for electron transport of respiratory chain inhibited mClCR and PTP opening. Partial recovery of electron transport in respiratory chain resulted in partial recovery of mClCR and PTP opening. mClCR and PTP opening were also inhibited by CCCP which eliminated transmembrane proton gradient. The results indicated that mitochondrial Ca2+ transport and PTP opening are largely dependent on electron transport and energy coupling.

  13. Inhibition of fast axonal transport by pathogenic SOD1 involves activation of p38 MAP kinase.

    Directory of Open Access Journals (Sweden)

    Gerardo A Morfini

    Full Text Available Dying-back degeneration of motor neuron axons represents an established feature of familial amyotrophic lateral sclerosis (FALS associated with superoxide dismutase 1 (SOD1 mutations, but axon-autonomous effects of pathogenic SOD1 remained undefined. Characteristics of motor neurons affected in FALS include abnormal kinase activation, aberrant neurofilament phosphorylation, and fast axonal transport (FAT deficits, but functional relationships among these pathogenic events were unclear. Experiments in isolated squid axoplasm reveal that FALS-related SOD1 mutant polypeptides inhibit FAT through a mechanism involving a p38 mitogen activated protein kinase pathway. Mutant SOD1 activated neuronal p38 in mouse spinal cord, neuroblastoma cells and squid axoplasm. Active p38 MAP kinase phosphorylated kinesin-1, and this phosphorylation event inhibited kinesin-1. Finally, vesicle motility assays revealed previously unrecognized, isoform-specific effects of p38 on FAT. Axon-autonomous activation of the p38 pathway represents a novel gain of toxic function for FALS-linked SOD1 proteins consistent with the dying-back pattern of neurodegeneration characteristic of ALS.

  14. Fluorescence Imaging of Fast Retrograde Axonal Transport in Living Animals

    Directory of Open Access Journals (Sweden)

    Dawid Schellingerhout

    2009-11-01

    Full Text Available Our purpose was to enable an in vivo imaging technology that can assess the anatomy and function of peripheral nerve tissue (neurography. To do this, we designed and tested a fluorescently labeled molecular probe based on the nontoxic C fragment of tetanus toxin (TTc. TTc was purified, labeled, and subjected to immunoassays and cell uptake assays. The compound was then injected into C57BL/6 mice (N = 60 for in vivo imaging and histologic studies. Image analysis and immunohistochemistry were performed. We found that TTc could be labeled with fluorescent moieties without loss of immunoreactivity or biologic potency in cell uptake assays. In vivo fluorescent imaging experiments demonstrated uptake and retrograde transport of the compound along the course of the sciatic nerve and in the spinal cord. Ex vivo imaging and immunohistochemical studies confirmed the presence of TTc in the sciatic nerve and spinal cord, whereas control animals injected with human serum albumin did not exhibit these features. We have demonstrated neurography with a fluorescently labeled molecular imaging contrast agent based on the TTc.

  15. Pressure-induced optic nerve axonal transport interruption in cat eyes.

    Science.gov (United States)

    Radius, R L; Bade, B

    1981-12-01

    After intravitreal injection of tritiated leucine, optic nerve axonal transport was studied in 30 cat eyes by tissue radioautography. Twenty-five experimental eyes were examined after four hours of acute pressure elevation with perfusion pressures maintained at 20 to 70 mm Hg. In five control specimens, intraocular pressures were maintained at 10 mm Hg for the four-hour interval. The extent of leucine accumulation, as seen by radioautographs, was inversely proportional to the perfusion pressure. Accumulation was limited to the region fo the lamina cribrosa. The anatomic distribution and pressure response of this transport interruption were similar to those seen in primate eyes studied under similar conditions.

  16. Pressure-induced optic nerve axonal transport interruption in cat eyes

    Energy Technology Data Exchange (ETDEWEB)

    Radius, R.L.; Bade, B.

    1981-12-01

    After intravitreal injection of tritiated leucine, optic nerve axonal transport was studied in 30 cat eyes by tissue radioautography. Twenty-five experimental eyes were examined after four hours of acute pressure elevation with perfusion pressures maintained at 20 to 70 mm Hg. In five control specimens, intraocular pressures were maintained at 10 mm Hg for the four-hour interval. The extent of leucine accumulation, as seen by radioautographs, was inversely proportional to the perfusion pressure. Accumulation was limited to the region fo the lamina cribrosa. The anatomic distribution and pressure response of this transport interruption were similar to those seen in primate eyes studied under similar conditions.

  17. Botulinum neurotoxins A and E undergo retrograde axonal transport in primary motor neurons.

    Directory of Open Access Journals (Sweden)

    Laura Restani

    2012-12-01

    Full Text Available The striking differences between the clinical symptoms of tetanus and botulism have been ascribed to the different fate of the parental neurotoxins once internalised in motor neurons. Tetanus toxin (TeNT is known to undergo transcytosis into inhibitory interneurons and block the release of inhibitory neurotransmitters in the spinal cord, causing a spastic paralysis. In contrast, botulinum neurotoxins (BoNTs block acetylcholine release at the neuromuscular junction, therefore inducing a flaccid paralysis. Whilst overt experimental evidence supports the sorting of TeNT to the axonal retrograde transport pathway, recent findings challenge the established view that BoNT trafficking is restricted to the neuromuscular junction by highlighting central effects caused by these neurotoxins. These results suggest a more complex scenario whereby BoNTs also engage long-range trafficking mechanisms. However, the intracellular pathways underlying this process remain unclear. We sought to fill this gap by using primary motor neurons either in mass culture or differentiated in microfluidic devices to directly monitor the endocytosis and axonal transport of full length BoNT/A and BoNT/E and their recombinant binding fragments. We show that BoNT/A and BoNT/E are internalised by spinal cord motor neurons and undergo fast axonal retrograde transport. BoNT/A and BoNT/E are internalised in non-acidic axonal carriers that partially overlap with those containing TeNT, following a process that is largely independent of stimulated synaptic vesicle endo-exocytosis. Following intramuscular injection in vivo, BoNT/A and TeNT displayed central effects with a similar time course. Central actions paralleled the peripheral spastic paralysis for TeNT, but lagged behind the onset of flaccid paralysis for BoNT/A. These results suggest that the fast axonal retrograde transport compartment is composed of multifunctional trafficking organelles orchestrating the simultaneous transfer

  18. Impulse conduction increases mitochondrial transport in adult mammalian peripheral nerves in vivo.

    Directory of Open Access Journals (Sweden)

    Marija Sajic

    2013-12-01

    Full Text Available Matching energy supply and demand is critical in the bioenergetic homeostasis of all cells. This is a special problem in neurons where high levels of energy expenditure may occur at sites remote from the cell body, given the remarkable length of axons and enormous variability of impulse activity over time. Positioning mitochondria at areas with high energy requirements is an essential solution to this problem, but it is not known how this is related to impulse conduction in vivo. Therefore, to study mitochondrial trafficking along resting and electrically active adult axons in vivo, confocal imaging of saphenous nerves in anaesthetised mice was combined with electrical and pharmacological stimulation of myelinated and unmyelinated axons, respectively. We show that low frequency activity induced by electrical stimulation significantly increases anterograde and retrograde mitochondrial traffic in comparison with silent axons. Higher frequency conduction within a physiological range (50 Hz dramatically further increased anterograde, but not retrograde, mitochondrial traffic, by rapidly increasing the number of mobile mitochondria and gradually increasing their velocity. Similarly, topical application of capsaicin to skin innervated by the saphenous nerve increased mitochondrial traffic in both myelinated and unmyelinated axons. In addition, stationary mitochondria in axons conducting at higher frequency become shorter, thus supplying additional mitochondria to the trafficking population, presumably through enhanced fission. Mitochondria recruited to the mobile population do not accumulate near Nodes of Ranvier, but continue to travel anterogradely. This pattern of mitochondrial redistribution suggests that the peripheral terminals of sensory axons represent sites of particularly high metabolic demand during physiological high frequency conduction. As the majority of mitochondrial biogenesis occurs at the cell body, increased anterograde

  19. Automated Measurement of Fast Mitochondrial Transport in Neurons

    Directory of Open Access Journals (Sweden)

    Kyle eMiller

    2015-11-01

    Full Text Available There is a growing recognition that fast mitochondrial transport in neurons is disrupted in multiple neurological diseases and psychiatric disorders. However a major constraint in identifying novel therapeutics based on mitochondrial transport is that the large-scale analysis of fast transport is time consuming. Here we describe methodologies for the automated analysis of fast mitochondrial transport from data acquired using a robotic microscope. We focused on addressing questions of measurement precision, speed, reliably, workflow ease, statistical processing and presentation. We used optical flow and particle tracking algorithms, implemented in ImageJ, to measure mitochondrial movement in primary cultured cortical and hippocampal neurons. With it, we are able to generate complete descriptions of movement profiles in an automated fashion of hundred of thousands of mitochondria with a processing time of approximately one hour. We describe the calibration of the parameters of the tracking algorithms and demonstrate that they are capable of measuring the fast transport of a single mitochondrion. We then show that the methods are capable of reliably measuring the inhibition of fast mitochondria transport induced by the disruption of microtubules with the drug nocodazole in both hippocampal and cortical neurons. This work lays the foundation for future large-scale screens designed to identify compounds that modulate mitochondrial motility.

  20. Automated measurement of fast mitochondrial transport in neurons.

    Science.gov (United States)

    Miller, Kyle E; Liu, Xin-An; Puthanveettil, Sathyanarayanan V

    2015-01-01

    There is growing recognition that fast mitochondrial transport in neurons is disrupted in multiple neurological diseases and psychiatric disorders. However, a major constraint in identifying novel therapeutics based on mitochondrial transport is that the large-scale analysis of fast transport is time consuming. Here we describe methodologies for the automated analysis of fast mitochondrial transport from data acquired using a robotic microscope. We focused on addressing questions of measurement precision, speed, reliably, workflow ease, statistical processing, and presentation. We used optical flow and particle tracking algorithms, implemented in ImageJ, to measure mitochondrial movement in primary cultured cortical and hippocampal neurons. With it, we are able to generate complete descriptions of movement profiles in an automated fashion of hundreds of thousands of mitochondria with a processing time of approximately one hour. We describe the calibration of the parameters of the tracking algorithms and demonstrate that they are capable of measuring the fast transport of a single mitochondrion. We then show that the methods are capable of reliably measuring the inhibition of fast mitochondria transport induced by the disruption of microtubules with the drug nocodazole in both hippocampal and cortical neurons. This work lays the foundation for future large-scale screens designed to identify compounds that modulate mitochondrial motility.

  1. Axonal transport and neurodegenerative disease: vesicle-motor complex formation and their regulation

    Directory of Open Access Journals (Sweden)

    Anderson EN

    2014-03-01

    Full Text Available Eric N Anderson,* Joseph A White II,* Shermali GunawardenaDepartment of Biological Sciences, The State University of New York at Buffalo, Buffalo, NY, USA *These authors contributed equally to this work Abstract: The process of axonal transport serves to move components over very long distances on microtubule tracks in order to maintain neuronal viability. Molecular motors – kinesin and dynein – are essential for the movement of neuronal cargoes along these tracks; defects in this pathway have been implicated in the initiation or progression of some neurodegenerative diseases, suggesting that this process may be a key contributor in neuronal dysfunction. Recent work has led to the identification of some of the motor-cargo complexes, adaptor proteins, and their regulatory elements in the context of disease proteins. In this review, we focus on the assembly of the amyloid precursor protein, huntingtin, mitochondria, and the RNA-motor complexes and discuss how these may be regulated during long-distance transport in the context of neurodegenerative disease. As knowledge of these motor-cargo complexes and their involvement in axonal transport expands, insight into how defects in this pathway contribute to the development of neurodegenerative diseases becomes evident. Therefore, a better understanding of how this pathway normally functions has important implications for early diagnosis and treatment of diseases before the onset of disease pathology or behavior. Keywords: kinesin, dynein, amyloid precursor protein, huntingtin, microtubules

  2. Riluzole protects against glutamate-induced slowing of neurofilament axonal transport.

    LENUS (Irish Health Repository)

    Stevenson, Alison

    2009-04-24

    Riluzole is the only drug approved for the treatment of amyotrophic lateral sclerosis (ALS) but its precise mode of action is not properly understood. Damage to axonal transport of neurofilaments is believed to be part of the pathogenic mechanism in ALS and this has been linked to defective glutamate handling and increased phosphorylation of neurofilament side-arm domains. Here, we show that riluzole protects against glutamate-induced slowing of neurofilament transport. Protection is associated with decreased neurofilament side-arm phosphorylation and inhibition of the activities of two neurofilament kinases, ERK and p38 that are activated in ALS. Thus, the anti-glutamatergic properties of riluzole include protection against glutamate-induced changes to neurofilament phosphorylation and transport.

  3. Ndel1-derived peptides modulate bidirectional transport of injected beads in the squid giant axon

    Directory of Open Access Journals (Sweden)

    Michal Segal

    2012-01-01

    Bidirectional transport is a key issue in cellular biology. It requires coordination between microtubule-associated molecular motors that work in opposing directions. The major retrograde and anterograde motors involved in bidirectional transport are cytoplasmic dynein and conventional kinesin, respectively. It is clear that failures in molecular motor activity bear severe consequences, especially in the nervous system. Neuronal migration may be impaired during brain development, and impaired molecular motor activity in the adult is one of the hallmarks of neurodegenerative diseases leading to neuronal cell death. The mechanisms that regulate or coordinate kinesin and dynein activity to generate bidirectional transport of the same cargo are of utmost importance. We examined how Ndel1, a cytoplasmic dynein binding protein, may regulate non-vesicular bidirectional transport. Soluble Ndel1 protein, Ndel1-derived peptides or control proteins were mixed with fluorescent beads, injected into the squid giant axon, and the bead movements were recorded using time-lapse microscopy. Automated tracking allowed for extraction and unbiased analysis of a large data set. Beads moved in both directions with a clear bias to the anterograde direction. Velocities were distributed over a broad range and were typically slower than those associated with fast vesicle transport. Ironically, the main effect of Ndel1 and its derived peptides was an enhancement of anterograde motion. We propose that they may function primarily by inhibition of dynein-dependent resistance, which suggests that both dynein and kinesin motors may remain engaged with microtubules during bidirectional transport.

  4. Stress-Induced CDK5 Activation Disrupts Axonal Transport via Lis1/Ndel1/Dynein

    Directory of Open Access Journals (Sweden)

    Eva Klinman

    2015-07-01

    Full Text Available Axonal transport is essential for neuronal function, and defects in transport are associated with multiple neurodegenerative diseases. Aberrant cyclin-dependent kinase 5 (CDK5 activity, driven by the stress-induced activator p25, also is observed in these diseases. Here we show that elevated CDK5 activity increases the frequency of nonprocessive events for a range of organelles, including lysosomes, autophagosomes, mitochondria, and signaling endosomes. Transport disruption induced by aberrant CDK5 activation depends on the Lis1/Ndel1 complex, which directly regulates dynein activity. CDK5 phosphorylation of Ndel1 favors a high affinity Lis1/Ndel/dynein complex that blocks the ATP-dependent release of dynein from microtubules, inhibiting processive motility of dynein-driven cargo. Similar transport defects observed in neurons from a mouse model of amyotrophic lateral sclerosis are rescued by CDK5 inhibition. Together, these studies identify CDK5 as a Lis1/Ndel1-dependent regulator of transport in stressed neurons, and suggest that dysregulated CDK5 activity contributes to the transport deficits observed during neurodegeneration.

  5. Quantitative measurements and modeling of cargo-motor interactions during fast transport in the living axon

    Science.gov (United States)

    Seamster, Pamela E.; Loewenberg, Michael; Pascal, Jennifer; Chauviere, Arnaud; Gonzales, Aaron; Cristini, Vittorio; Bearer, Elaine L.

    2012-10-01

    The kinesins have long been known to drive microtubule-based transport of sub-cellular components, yet the mechanisms of their attachment to cargo remain a mystery. Several different cargo-receptors have been proposed based on their in vitro binding affinities to kinesin-1. Only two of these—phosphatidyl inositol, a negatively charged lipid, and the carboxyl terminus of the amyloid precursor protein (APP-C), a trans-membrane protein—have been reported to mediate motility in living systems. A major question is how these many different cargo, receptors and motors interact to produce the complex choreography of vesicular transport within living cells. Here we describe an experimental assay that identifies cargo-motor receptors by their ability to recruit active motors and drive transport of exogenous cargo towards the synapse in living axons. Cargo is engineered by derivatizing the surface of polystyrene fluorescent nanospheres (100 nm diameter) with charged residues or with synthetic peptides derived from candidate motor receptor proteins, all designed to display a terminal COOH group. After injection into the squid giant axon, particle movements are imaged by laser-scanning confocal time-lapse microscopy. In this report we compare the motility of negatively charged beads with APP-C beads in the presence of glycine-conjugated non-motile beads using new strategies to measure bead movements. The ensuing quantitative analysis of time-lapse digital sequences reveals detailed information about bead movements: instantaneous and maximum velocities, run lengths, pause frequencies and pause durations. These measurements provide parameters for a mathematical model that predicts the spatiotemporal evolution of distribution of the two different types of bead cargo in the axon. The results reveal that negatively charged beads differ from APP-C beads in velocity and dispersion, and predict that at long time points APP-C will achieve greater progress towards the presynaptic

  6. Failure of unilateral carotid artery ligation to affect pressure-induced interruption of rapid axonal transport in primate optic nerves.

    Science.gov (United States)

    Radius, R L; Schwartz, E L; Anderson, D R

    1980-02-01

    Previous experiments showed that optic nerve axonal transport can be blocked at the level of the lamina cribrosa by elevated intraocular pressure. In an effort to discover if this blockage might be secondary to pressure-induced ischemia, we studied the effect of unilateral common carotid artery ligation upont the pressure-induced interruption of axonal transport. In 13 owl monkeys (Aotus trivirgatus), the right common carotid artery was ligated within the anterior cervical triangle. Three days later, ophtalmodynomometry was performed on all experimental eyes. In nine of the 13 animals, this estimate of ophthalmic artery pressure was 10 to 20 mm Hg less in the right compared to the left eye. Optic nerve axonal transport was studied in right and left eyes during 5 hours of increased intraocular pressure (ocular pressure 35 mm Hg less than mean femoral artery blood pressure). No significant difference in the extent to which the transport mechanisms were interrupted could be demonstrated when comparing right and left eyes of the experimental animals. These observations fail to support a vascular mechanism for this pressure-induced interruption of axonal transport.

  7. Unc-51/ATG1 controls axonal and dendritic development via kinesin-mediated vesicle transport in the Drosophila brain.

    Directory of Open Access Journals (Sweden)

    Hiroaki Mochizuki

    Full Text Available BACKGROUND: Members of the evolutionary conserved Ser/Thr kinase Unc-51 family are key regulatory proteins that control neural development in both vertebrates and invertebrates. Previous studies have suggested diverse functions for the Unc-51 protein, including axonal elongation, growth cone guidance, and synaptic vesicle transport. METHODOLOGY/PRINCIPAL FINDINGS: In this work, we have investigated the functional significance of Unc-51-mediated vesicle transport in the development of complex brain structures in Drosophila. We show that Unc-51 preferentially accumulates in newly elongating axons of the mushroom body, a center of olfactory learning in flies. Mutations in unc-51 cause disintegration of the core of the developing mushroom body, with mislocalization of Fasciclin II (Fas II, an IgG-family cell adhesion molecule important for axonal guidance and fasciculation. In unc-51 mutants, Fas II accumulates in the cell bodies, calyx, and the proximal peduncle. Furthermore, we show that mutations in unc-51 cause aberrant overshooting of dendrites in the mushroom body and the antennal lobe. Loss of unc-51 function leads to marked accumulation of Rab5 and Golgi components, whereas the localization of dendrite-specific proteins, such as Down syndrome cell adhesion molecule (DSCAM and No distributive disjunction (Nod, remains unaltered. Genetic analyses of kinesin light chain (Klc and unc-51 double heterozygotes suggest the importance of kinesin-mediated membrane transport for axonal and dendritic development. Moreover, our data demonstrate that loss of Klc activity causes similar axonal and dendritic defects in mushroom body neurons, recapitulating the salient feature of the developmental abnormalities caused by unc-51 mutations. CONCLUSIONS/SIGNIFICANCE: Unc-51 plays pivotal roles in the axonal and dendritic development of the Drosophila brain. Unc-51-mediated membrane vesicle transport is important in targeted localization of guidance molecules

  8. Isolating the segment of the mitochondrial electron transport chain responsible for mitochondrial damage during cardiac ischemia

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qun; Yin, Guotian; Stewart, Sarah; Hu, Ying [Department of Medicine, Division of Cardiology, Case Western Reserve University, Cleveland, OH 44106 (United States); Lesnefsky, Edward J., E-mail: edward.lesnefsky@va.gov [Department of Medicine, Division of Cardiology, Case Western Reserve University, Cleveland, OH 44106 (United States); Medical Service, Louis Stokes Veterans Affairs Medical Center, Cleveland, OH 44106 (United States)

    2010-07-09

    Ischemia damages the mitochondrial electron transport chain (ETC), mediated in part by damage generated by the mitochondria themselves. Mitochondrial damage resulting from ischemia, in turn, leads to cardiac injury during reperfusion. The goal of the present study was to localize the segment of the ETC that produces the ischemic mitochondrial damage. We tested if blockade of the proximal ETC at complex I differed from blockade distal in the chain at cytochrome oxidase. Isolated rabbit hearts were perfused for 15 min followed by 30 min stop-flow ischemia at 37 {sup o}C. Amobarbital (2.5 mM) or azide (5 mM) was used to block proximal (complex I) or distal (cytochrome oxidase) sites in the ETC. Time control hearts were buffer-perfused for 45 min. Subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM) were isolated. Ischemia decreased cytochrome c content in SSM but not in IFM compared to time control. Blockade of electron transport at complex I preserved the cytochrome c content in SSM. In contrast, blockade of electron transport at cytochrome oxidase with azide did not retain cytochrome c in SSM during ischemia. Since blockade of electron transport at complex III also prevented cytochrome c loss during ischemia, the specific site that elicits mitochondrial damage during ischemia is likely located in the segment between complex III and cytochrome oxidase.

  9. Mitochondrial dynamics in visual cortex are limited in vivo and not affected by axonal structural plasticity.

    NARCIS (Netherlands)

    Smit-Rigter, L.A.; Rajendran, Rajeev; Silva, Catia A.P.; Spierenburg, Liselot; Groeneweg, Femke; Ruimschotel, E.; Van Versendaal, D.; van der Togt, C.; Eysel, Ulf T.; Heimel, J.A.; Lohmann, C.; Levelt, C.N.

    2016-01-01

    Mitochondria buffer intracellular Ca2+ and provide energy [1]. Because synaptic structures with high Ca2+ buffering [2–4] or energy demand [5] are often localized far away from the soma, mitochondria are actively transported to these sites [6–11]. Also, the removal and degradation of mitochondria ar

  10. Pressure-induced fast axonal transport abnormalities and the anatomy at the lamina cribrosa in primate eyes.

    Science.gov (United States)

    Radius, R L

    1983-03-01

    In ten owl monkey eyes (Aotus trivirgatus) the location of pressure-induced (perfusion pressure 35 mmHg) axonal transport abnormalities was determined by the examination of serial step cross-section tissue radio autographs from the optic nerve head. The degree of the local transport interruption did not correlate with the fiber bundle cross-section area, the shape of the laminar pores or the density of the inter-bundle septa in that region.

  11. Sensory neuropathy in progressive motor neuronopathy (pmn) mice is associated with defects in microtubule polymerization and axonal transport.

    Science.gov (United States)

    Schäfer, Michael K; Bellouze, Sarah; Jacquier, Arnaud; Schaller, Sébastien; Richard, Laurence; Mathis, Stéphane; Vallat, Jean-Michel; Haase, Georg

    2016-08-04

    Motor neuron diseases such as amyotrophic lateral sclerosis (ALS) are now recognized as multi-system disorders also involving various non-motor neuronal cell types. The precise extent and mechanistic basis of non-motor neuron damage in human ALS and ALS animal models remain however unclear. To address this, we here studied progressive motor neuronopathy (pmn) mice carrying a missense loss-of-function mutation in tubulin binding cofactor E (TBCE). These mice manifest a particularly aggressive form of motor axon dying back and display a microtubule loss, similar to that induced by human ALS-linked TUBA4A mutations. Using whole nerve confocal imaging of pmn × thy1.2-YFP16 fluorescent reporter mice and electron microscopy, we demonstrate axonal discontinuities, bead-like spheroids and ovoids in pmn suralis nerves indicating prominent sensory neuropathy. The axonal alterations qualitatively resemble those in phrenic motor nerves but do not culminate in the loss of myelinated fibers. We further show that the pmn mutation decreases the level of TBCE, impedes microtubule polymerization in dorsal root ganglion (DRG) neurons and causes progressive loss of microtubules in large and small caliber suralis axons. Live imaging of axonal transport using GFP-tagged tetanus toxin C-fragment (GFP-TTC) demonstrates defects in microtubule-based transport in pmn DRG neurons, providing a potential explanation for the axonal alterations in sensory nerves. This study unravels sensory neuropathy as a pathological feature of mouse pmn, and discusses the potential contribution of cytoskeletal defects to sensory neuropathy in human motor neuron disease.

  12. [Molecular genetic studies of mitochondrial ornithine transporter deficiency (HHH syndrome)].

    Science.gov (United States)

    Tsujino, S; Miyamoto, T; Kanazawa, N

    2001-11-01

    Mitochondrial ornithine transporter deficiency has been called HHH syndrome, because this disorder is characterized by three biochemical abnormalities; hyperornithinemia, hyperammonemia, and homocitrullinuria, and presents with various neurological symptoms; mental retardation, spastic paraparesis with pyramidal signs, cerebellar ataxia and episodic disturbance of consciousness or coma due to hyperammonemia. We identified four mutations in the mitochondrial ornithine transporter gene (ORNT1) of Japanese patients with HHH syndrome. These include a nonsense mutation (R179X), associated with exon skipping, missense mutations (G27E, P126R), and an insertion of AAC between codons 228 and 229, leading to an insertion of amino acid Asn. Especially, R179X was detected 4 of 7 Japanese patients (8 of 14 alleles), implying that this is a common mutation in Japanese population.

  13. Endosome-mediated retrograde axonal transport of P2X3 receptor signals in primary sensory neurons

    Institute of Scientific and Technical Information of China (English)

    Xu-Qiao Chen; BinWang; Chengbiao Wu; Jin Pan; Bo Yuan; Yuan-Yuan Su; Xing-Yu Jiang; Xu Zhang; Lan Bao

    2012-01-01

    Neurotrophins and their receptors adopt signaling endosomes to transmit retrograde signals.However,the mechanisms of retrograde signaling for other ligand/receptor systems are poorly understood.Here,we report that the signals of the purinergic (P)2X3 receptor,an ATP-gated ion channel are retrogradely transported in dorsal root ganglion (DRG) neuron axons.We found that Rab5,a small GTPase,controls the early sorting of P2X3 receptors into endosomes,while Rab7 mediates the fast retrograde transport of P2X3 receptors.Intraplantar injection and axonal application into the microfluidic chamber of α,β-methylene-ATP (α,β-MeATP),a P2X selective agonist,enhanced the endocytosis and retrograde transport of P2X3 receptors.The α,β-MeATP-induced Ca2+ influx activated a pathway comprised of protein kinase C,rat sarcoma viral oncogene and extracellular signal-regulated protein kinase (ERK),which associated with endocytic P2X3 receptors to form signaling endosomes.Disruption of the lipid rafts abolished the α,β-MeATP-induced ERK phosphorylation,endocytosis and retrograde transport of P2X3 receptors.Furthermore,treatment of peripheral axons with α,β-MeATP increased the activation level of ERK and cAMP response element-binding protein in the cell bodies of DRG neurons and enhanced neuronal excitability.Impairment of either microtubule-based axonal transport in vivo or dynein function in vitro blocked α,β-MeATP-induced retrograde signals.These results indicate that P2X3 receptor-activated signals are transmitted via retrogradely transported endosomes in primary sensory neurons and provide a novel signaling mechanism for ligand-gated channels.

  14. Limited trafficking of a neurotropic virus through inefficient retrograde axonal transport and the type I interferon response.

    Science.gov (United States)

    Lancaster, Karen Z; Pfeiffer, Julie K

    2010-03-05

    Poliovirus is an enteric virus that rarely invades the human central nervous system (CNS). To identify barriers limiting poliovirus spread from the periphery to CNS, we monitored trafficking of 10 marked viruses. After oral inoculation of susceptible mice, poliovirus was present in peripheral neurons, including vagus and sciatic nerves. To model viral trafficking in peripheral neurons, we intramuscularly injected mice with poliovirus, which follows a muscle-sciatic nerve-spinal cord-brain route. Only 20% of the poliovirus population successfully moved from muscle to brain, and three barriers limiting viral trafficking were identified. First, using light-sensitive viruses, we found limited viral replication in peripheral neurons. Second, retrograde axonal transport of poliovirus in peripheral neurons was inefficient; however, the efficiency was increased upon muscle damage, which also increased the transport efficiency of a non-viral neural tracer, wheat germ agglutinin. Third, using susceptible interferon (IFN) alpha/beta receptor knockout mice, we demonstrated that the IFN response limited viral movement from the periphery to the brain. Surprisingly, the retrograde axonal transport barrier was equivalent in strength to the IFN barrier. Illustrating the importance of barriers created by the IFN response and inefficient axonal transport, IFN alpha/beta receptor knockout mice with muscle damage permitted 80% of the viral population to access the brain, and succumbed to disease three times faster than mice with intact barriers. These results suggest that multiple separate barriers limit poliovirus trafficking from peripheral neurons to the CNS, possibly explaining the rare incidence of paralytic poliomyelitis. This study identifies inefficient axonal transport as a substantial barrier to poliovirus trafficking in peripheral neurons, which may limit CNS access for other viruses.

  15. Limited trafficking of a neurotropic virus through inefficient retrograde axonal transport and the type I interferon response.

    Directory of Open Access Journals (Sweden)

    Karen Z Lancaster

    2010-03-01

    Full Text Available Poliovirus is an enteric virus that rarely invades the human central nervous system (CNS. To identify barriers limiting poliovirus spread from the periphery to CNS, we monitored trafficking of 10 marked viruses. After oral inoculation of susceptible mice, poliovirus was present in peripheral neurons, including vagus and sciatic nerves. To model viral trafficking in peripheral neurons, we intramuscularly injected mice with poliovirus, which follows a muscle-sciatic nerve-spinal cord-brain route. Only 20% of the poliovirus population successfully moved from muscle to brain, and three barriers limiting viral trafficking were identified. First, using light-sensitive viruses, we found limited viral replication in peripheral neurons. Second, retrograde axonal transport of poliovirus in peripheral neurons was inefficient; however, the efficiency was increased upon muscle damage, which also increased the transport efficiency of a non-viral neural tracer, wheat germ agglutinin. Third, using susceptible interferon (IFN alpha/beta receptor knockout mice, we demonstrated that the IFN response limited viral movement from the periphery to the brain. Surprisingly, the retrograde axonal transport barrier was equivalent in strength to the IFN barrier. Illustrating the importance of barriers created by the IFN response and inefficient axonal transport, IFN alpha/beta receptor knockout mice with muscle damage permitted 80% of the viral population to access the brain, and succumbed to disease three times faster than mice with intact barriers. These results suggest that multiple separate barriers limit poliovirus trafficking from peripheral neurons to the CNS, possibly explaining the rare incidence of paralytic poliomyelitis. This study identifies inefficient axonal transport as a substantial barrier to poliovirus trafficking in peripheral neurons, which may limit CNS access for other viruses.

  16. Release of kinesin from vesicles by hsc70 and regulation of fast axonal transport

    Science.gov (United States)

    Tsai, M. Y.; Morfini, G.; Szebenyi, G.; Brady, S. T.

    2000-01-01

    The nature of kinesin interactions with membrane-bound organelles and mechanisms for regulation of kinesin-based motility have both been surprisingly difficult to define. Most kinesin is recovered in supernatants with standard protocols for purification of motor proteins, but kinesin recovered on membrane-bound organelles is tightly bound. Partitioning of kinesin between vesicle and cytosolic fractions is highly sensitive to buffer composition. Addition of either N-ethylmaleimide or EDTA to homogenization buffers significantly increased the fraction of kinesin bound to organelles. Given that an antibody against kinesin light chain tandem repeats also releases kinesin from vesicles, these observations indicated that specific cytoplasmic factors may regulate kinesin release from membranes. Kinesin light tandem repeats contain DnaJ-like motifs, so the effects of hsp70 chaperones were evaluated. Hsc70 released kinesin from vesicles in an MgATP-dependent and N-ethylmaleimide-sensitive manner. Recombinant kinesin light chains inhibited kinesin release by hsc70 and stimulated the hsc70 ATPase. Hsc70 actions may provide a mechanism to regulate kinesin function by releasing kinesin from cargo in specific subcellular domains, thereby effecting delivery of axonally transported materials.

  17. Mitochondrial fission protein Drp1 regulates mitochondrial transport and dendritic arborization in cerebellar Purkinje cells.

    Science.gov (United States)

    Fukumitsu, Kansai; Hatsukano, Tetsu; Yoshimura, Azumi; Heuser, John; Fujishima, Kazuto; Kengaku, Mineko

    2016-03-01

    Mitochondria dynamically change their shape by repeated fission and fusion in response to physiological and pathological conditions. Recent studies have uncovered significant roles of mitochondrial fission and fusion in neuronal functions, such as neurotransmission and spine formation. However, the contribution of mitochondrial fission to the development of dendrites remains controversial. We analyzed the function of the mitochondrial fission GTPase Drp1 in dendritic arborization in cerebellar Purkinje cells. Overexpression of a dominant-negative mutant of Drp1 in postmitotic Purkinje cells enlarged and clustered mitochondria, which failed to exit from the soma into the dendrites. The emerging dendrites lacking mitochondrial transport remained short and unstable in culture and in vivo. The dominant-negative Drp1 affected neither the basal respiratory function of mitochondria nor the survival of Purkinje cells. Enhanced ATP supply by creatine treatment, but not reduced ROS production by antioxidant treatment, restored the hypomorphic dendrites caused by inhibition of Drp1 function. Collectively, our results suggest that Drp1 is required for dendritic distribution of mitochondria and thereby regulates energy supply in growing dendritic branches in developing Purkinje cells.

  18. Vesicular acetylcholine transporter-immunoreactive axon terminals enriched in the pontine nuclei of the mouse.

    Science.gov (United States)

    Tsutsumi, T; Houtani, T; Toida, K; Kase, M; Yamashita, T; Ishimura, K; Sugimoto, T

    2007-06-08

    Information to the cerebellum enters via many afferent sources collectively known as precerebellar nuclei. We investigated the distribution of cholinergic terminal-like structures in the mouse precerebellar nuclei by immunohistochemistry for vesicular acetylcholine transporter (VAChT). VAChT is involved in acetylcholine transport into synaptic vesicles and is regarded as a reliable marker for cholinergic terminals and preterminal axons. In adult male mice, brains were perfusion-fixed. Polyclonal antibodies for VAChT, immunoglobulin G-peroxidase and diaminobenzidine were used for immunostaining. In the mouse brain, immunoreactivity was seen in almost all major cholinergic cell groups including brainstem motoneurons. In precerebellar nuclei, the signal could be detected as diffusely beaded terminal-like structures. It was seen heaviest in the pontine nuclei and moderate in the pontine reticulotegmental nucleus; however, it was seen less in the medial solitary nucleus, red nucleus, lateral reticular nucleus, inferior olivary nucleus, external cuneate nucleus and vestibular nuclear complex. In particular, VAChT-immunoreactive varicose fibers were so dense in the pontine nuclei that detailed distribution was studied using three-dimensional reconstruction of the pontine nuclei. VAChT-like immunoreactivity clustered predominantly in the medial and ventral regions suggesting a unique regional difference of the cholinergic input. Electron microscopic observation in the pontine nuclei disclosed ultrastructural features of VAChT-immunoreactive varicosities. The labeled bouton makes a symmetrical synapse with unlabeled dendrites and contains pleomorphic synaptic vesicles. To clarify the neurons of origin of VAChT-immunoreactive terminals, VAChT immunostaining combined with wheat germ agglutinin-conjugated horseradish peroxidase retrograde labeling was conducted by injecting a retrograde tracer into the right pontine nuclei. Double-labeled neurons were seen bilaterally in the

  19. R-Flurbiprofen Improves Axonal Transport in the Tg2576 Mouse Model of Alzheimer’s Disease as Determined by MEMRI

    Science.gov (United States)

    Smith, Karen D.B.; Paylor, Richard; Pautler, Robia G.

    2011-01-01

    Axonal pathology is a prevalent feature of Alzheimer’s disease (AD) and is thought to occur predominantly due to the accumulation of amyloid beta (Aβ). However, it remains unclear whether therapeutics geared towards reducing Aβ improves axonal deficits. We have previously used Manganese Enhanced MRI (MEMRI) to demonstrate that axonal transport deficits occur before plaque formation in the Tg2576 mouse model of AD. Here we tested whether axonal transport deficits in the Tg2576 mouse model improve in response to the Aβ42 selective lowering agent R-Flurbiprofen (R-F). We demonstrated that in young animals (before Aβ plaque formation), R-F treatment reduced Aβ42 levels and coincided with a significant improvement in axonal transport (p=0.0186) iHowever, in older animals (after plaque formation had occurred), we observed that R-F treatment did not reduce Aβ42 levels although we still observed a significant improvement in axonal transport as assessed with MEMRI (p=0.0329). We then determined that R-F treatment reduced tau hyper-phosphorylation in the older animals. These data indicate that both Aβ42 and tau comprise a role in axonal transport rate deficits in the Tg2576 models. PMID:21500269

  20. Targeting of herpesvirus capsid transport in axons is coupled to association with specific sets of tegument proteins

    OpenAIRE

    Luxton, G.W. Gant; Haverlock, Sarah; Coller, Kelly Elizabeth; Antinone, Sarah Elizabeth; Pincetic, Andrew; Smith, Gregory Allan

    2005-01-01

    The capsids of neurotropic herpesviruses have the remarkable ability to move in specific directions within axons. By modulating bidirectional capsid transport to favor either retrograde (minus-end) or anterograde (plus-end) motion, these viruses travel to sensory ganglia or peripheral tissue at specific stages of infection. By using correlative motion analysis to simultaneously monitor the trafficking of distinct viral proteins in living neurons, we demonstrate that viral “tegument” proteins ...

  1. HDAC6 Inhibitors Rescued the Defective Axonal Mitochondrial Movement in Motor Neurons Derived from the Induced Pluripotent Stem Cells of Peripheral Neuropathy Patients with HSPB1 Mutation.

    Science.gov (United States)

    Kim, Ji-Yon; Woo, So-Youn; Hong, Young Bin; Choi, Heesun; Kim, Jisoo; Choi, Hyunjung; Mook-Jung, Inhee; Ha, Nina; Kyung, Jangbeen; Koo, Soo Kyung; Jung, Sung-Chul; Choi, Byung-Ok

    2016-01-01

    The Charcot-Marie-Tooth disease 2F (CMT2F) and distal hereditary motor neuropathy 2B (dHMN2B) are caused by autosomal dominantly inherited mutations of the heat shock 27 kDa protein 1 (HSPB1) gene and there are no specific therapies available yet. Here, we assessed the potential therapeutic effect of HDAC6 inhibitors on peripheral neuropathy with HSPB1 mutation using in vitro model of motor neurons derived from induced pluripotent stem cells (iPSCs) of CMT2F and dHMN2B patients. The absolute velocity of mitochondrial movements and the percentage of moving mitochondria in axons were lower both in CMT2F-motor neurons and in dHMN2B-motor neurons than those in controls, and the severity of the defective mitochondrial movement was different between the two disease models. CMT2F-motor neurons and dHMN2B-motor neurons also showed reduced α-tubulin acetylation compared with controls. The newly developed HDAC6 inhibitors, CHEMICAL X4 and CHEMICAL X9, increased acetylation of α-tubulin and reversed axonal movement defects of mitochondria in CMT2F-motor neurons and dHMN2B-motor neurons. Our results suggest that the neurons derived from patient-specific iPSCs can be used in drug screening including HDAC6 inhibitors targeting peripheral neuropathy.

  2. HDAC6 Inhibitors Rescued the Defective Axonal Mitochondrial Movement in Motor Neurons Derived from the Induced Pluripotent Stem Cells of Peripheral Neuropathy Patients with HSPB1 Mutation

    Directory of Open Access Journals (Sweden)

    Ji-Yon Kim

    2016-01-01

    Full Text Available The Charcot-Marie-Tooth disease 2F (CMT2F and distal hereditary motor neuropathy 2B (dHMN2B are caused by autosomal dominantly inherited mutations of the heat shock 27 kDa protein 1 (HSPB1 gene and there are no specific therapies available yet. Here, we assessed the potential therapeutic effect of HDAC6 inhibitors on peripheral neuropathy with HSPB1 mutation using in vitro model of motor neurons derived from induced pluripotent stem cells (iPSCs of CMT2F and dHMN2B patients. The absolute velocity of mitochondrial movements and the percentage of moving mitochondria in axons were lower both in CMT2F-motor neurons and in dHMN2B-motor neurons than those in controls, and the severity of the defective mitochondrial movement was different between the two disease models. CMT2F-motor neurons and dHMN2B-motor neurons also showed reduced α-tubulin acetylation compared with controls. The newly developed HDAC6 inhibitors, CHEMICAL X4 and CHEMICAL X9, increased acetylation of α-tubulin and reversed axonal movement defects of mitochondria in CMT2F-motor neurons and dHMN2B-motor neurons. Our results suggest that the neurons derived from patient-specific iPSCs can be used in drug screening including HDAC6 inhibitors targeting peripheral neuropathy.

  3. Mitochondrial ROS Produced via Reverse Electron Transport Extend Animal Lifespan.

    Science.gov (United States)

    Scialò, Filippo; Sriram, Ashwin; Fernández-Ayala, Daniel; Gubina, Nina; Lõhmus, Madis; Nelson, Glyn; Logan, Angela; Cooper, Helen M; Navas, Plácido; Enríquez, Jose Antonio; Murphy, Michael P; Sanz, Alberto

    2016-04-12

    Increased production of reactive oxygen species (ROS) has long been considered a cause of aging. However, recent studies have implicated ROS as essential secondary messengers. Here we show that the site of ROS production significantly contributes to their apparent dual nature. We report that ROS increase with age as mitochondrial function deteriorates. However, we also demonstrate that increasing ROS production specifically through respiratory complex I reverse electron transport extends Drosophila lifespan. Reverse electron transport rescued pathogenesis induced by severe oxidative stress, highlighting the importance of the site of ROS production in signaling. Furthermore, preventing ubiquinone reduction, through knockdown of PINK1, shortens lifespan and accelerates aging; phenotypes that are rescued by increasing reverse electron transport. These results illustrate that the source of a ROS signal is vital in determining its effects on cellular physiology and establish that manipulation of ubiquinone redox state is a valid strategy to delay aging.

  4. A role for cyclin-dependent kinase(s) in the modulation of fast anterograde axonal transport: effects defined by olomoucine and the APC tumor suppressor protein

    Science.gov (United States)

    Ratner, N.; Bloom, G. S.; Brady, S. T.

    1998-01-01

    Proteins that interact with both cytoskeletal and membrane components are candidates to modulate membrane trafficking. The tumor suppressor proteins neurofibromin (NF1) and adenomatous polyposis coli (APC) both bind to microtubules and interact with membrane-associated proteins. The effects of recombinant NF1 and APC fragments on vesicle motility were evaluated by measuring fast axonal transport along microtubules in axoplasm from squid giant axons. APC4 (amino acids 1034-2844) reduced only anterograde movements, whereas APC2 (aa 1034-2130) or APC3 (aa 2130-2844) reduced both anterograde and retrograde transport. NF1 had no effect on organelle movement in either direction. Because APC contains multiple cyclin-dependent kinase (CDK) consensus phosphorylation motifs, the kinase inhibitor olomoucine was examined. At concentrations in which olomoucine is specific for cyclin-dependent kinases (5 microM), it reduced only anterograde transport, whereas anterograde and retrograde movement were both affected at concentrations at which other kinases are inhibited as well (50 microM). Both anterograde and retrograde transport also were inhibited by histone H1 and KSPXK peptides, substrates for proline-directed kinases, including CDKs. Our data suggest that CDK-like axonal kinases modulate fast anterograde transport and that other axonal kinases may be involved in modulating retrograde transport. The specific effect of APC4 on anterograde transport suggests a model in which the binding of APC to microtubules may limit the activity of axonal CDK kinase or kinases in restricted domains, thereby affecting organelle transport.

  5. Mitochondrial dynamics and inherited peripheral nerve diseases.

    Science.gov (United States)

    Pareyson, Davide; Saveri, Paola; Sagnelli, Anna; Piscosquito, Giuseppe

    2015-06-02

    Peripheral nerves have peculiar energetic requirements because of considerable length of axons and therefore correct mitochondria functioning and distribution along nerves is fundamental. Mitochondrial dynamics refers to the continuous change in size, shape, and position of mitochondria within cells. Abnormalities of mitochondrial dynamics produced by mutations in proteins involved in mitochondrial fusion (mitofusin-2, MFN2), fission (ganglioside-induced differentiation-associated protein-1, GDAP1), and mitochondrial axonal transport usually present with a Charcot-Marie-Tooth disease (CMT) phenotype. MFN2 mutations cause CMT type 2A by altering mitochondrial fusion and trafficking along the axonal microtubule system. CMT2A is an axonal autosomal dominant CMT type which in most cases is characterized by early onset and rather severe course. GDAP1 mutations also alter fission, fusion and transport of mitochondria and are associated either with recessive demyelinating (CMT4A) and axonal CMT (AR-CMT2K) and, less commonly, with dominant, milder, axonal CMT (CMT2K). OPA1 (Optic Atrophy-1) is involved in fusion of mitochondrial inner membrane, and its heterozygous mutations lead to early-onset and progressive dominant optic atrophy which may be complicated by other neurological symptoms including peripheral neuropathy. Mutations in several proteins fundamental for the axonal transport or forming the axonal cytoskeleton result in peripheral neuropathy, i.e., CMT, distal hereditary motor neuropathy (dHMN) or hereditary sensory and autonomic neuropathy (HSAN), as well as in hereditary spastic paraplegia. Indeed, mitochondrial transport involves directly or indirectly components of the kinesin superfamily (KIF5A, KIF1A, KIF1B), responsible of anterograde transport, and of the dynein complex and related proteins (DYNC1H1, dynactin, dynamin-2), implicated in retrograde flow. Microtubules, neurofilaments, and chaperones such as heat shock proteins (HSPs) also have a fundamental

  6. Overexpression of Mitochondrial Phosphate Transporter 3 Severely Hampers Plant Development through Regulating Mitochondrial Function in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Fengjuan Jia

    Full Text Available Mitochondria are abundant and important organelles present in nearly all eukaryotic cells, which maintain metabolic communication with the cytosol through mitochondrial carriers. The mitochondrial membrane localized phosphate transporter (MPT plays vital roles in diverse development and signaling processes, especially the ATP biosynthesis. Among the three MPT genes in Arabidopsis genome, AtMPT3 was proven to be a major member, and its overexpression gave rise to multiple developmental defects including curly leaves with deep color, dwarfed stature, and reduced fertility. Transcript profiles revealed that genes involved in plant metabolism, cellular redox homeostasis, alternative respiration pathway, and leaf and flower development were obviously altered in AtMPT3 overexpression (OEMPT3 plants. Moreover, OEMPT3 plants also accumulated higher ATP content, faster respiration rate and more reactive oxygen species (ROS than wild type plants. Overall, our studies showed that AtMPT3 was indispensable for Arabidopsis normal growth and development, and provided new sights to investigate its possible regulation mechanisms.

  7. Organophosphate-Related Alterations in Myelin and Axonal Transport in the Living Mammalian Brain

    Science.gov (United States)

    2014-10-01

    Rusyniak DE, Nanagas KA. 2004. Organophosphate poisoning . Sem Neurol.24:197–204. Silva AC, Lee JH, Aoki I, Koretsky AP. 2004. Manganese-enhanced...Sungurtekin H, Gurses E, Balci C. 2006. Evaluation of several clinical scoring tools in organophosphate poisoned patients. Clin. Toxicol (Phila) 44:121...1 AD_________________ Award Number: W81XWH-12-1-0536 TITLE: " Organophosphate -Related Alterations in Myelin and Axonal

  8. Dual-specificity phosphatase 26 (DUSP26) stimulates Aβ42 generation by promoting amyloid precursor protein axonal transport during hypoxia.

    Science.gov (United States)

    Jung, Sunmin; Nah, Jihoon; Han, Jonghee; Choi, Seon-Guk; Kim, Hyunjoo; Park, Jaesang; Pyo, Ha-Kyung; Jung, Yong-Keun

    2016-06-01

    Amyloid beta peptide (Aβ) is a pathological hallmark of Alzheimer's disease (AD) and is generated through the sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases. Hypoxia is a known risk factor for AD and stimulates Aβ generation by γ-secretase; however, the underlying mechanisms remain unclear. In this study, we showed that dual-specificity phosphatase 26 (DUSP26) regulates Aβ generation through changes in subcellular localization of the γ-secretase complex and its substrate C99 under hypoxic conditions. DUSP26 was identified as a novel γ-secretase regulator from a genome-wide functional screen using a cDNA expression library. The phosphatase activity of DUSP26 was required for the increase in Aβ42 generation through γ-secretase, but this regulation did not affect the amount of the γ-secretase complex. Interestingly, DUSP26 induced the accumulation of C99 in the axons by stimulating anterograde transport of C99-positive vesicles. Additionally, DUSP26 induced c-Jun N-terminal kinase (JNK) activation for APP processing and axonal transport of C99. Under hypoxic conditions, DUSP26 expression levels were elevated together with JNK activation, and treatment with JNK inhibitor SP600125, or the DUSP26 inhibitor NSC-87877, reduced hypoxia-induced Aβ generation by diminishing vesicle trafficking of C99 to the axons. Finally, we observed enhanced DUSP26 expression and JNK activation in the hippocampus of AD patients. Our results suggest that DUSP26 mediates hypoxia-induced Aβ generation through JNK activation, revealing a new regulator of γ-secretase-mediated APP processing under hypoxic conditions. We propose the role of phosphatase dual-specificity phosphatase 26 (DUSP26) in the selective regulation of Aβ42 production in neuronal cells under hypoxic stress. Induction of DUSP26 causes JNK-dependent shift in the subcellular localization of γ-secretase and C99 from the cell body to axons for Aβ42 generation. These findings provide a

  9. Axon degeneration and PGC-1α-mediated protection in a zebrafish model of α-synuclein toxicity

    Directory of Open Access Journals (Sweden)

    Kelley C. O’Donnell

    2014-05-01

    Full Text Available α-synuclein (aSyn expression is implicated in neurodegenerative processes, including Parkinson’s disease (PD and dementia with Lewy bodies (DLB. In animal models of these diseases, axon pathology often precedes cell death, raising the question of whether aSyn has compartment-specific toxic effects that could require early and/or independent therapeutic intervention. The relevance of axonal pathology to degeneration can only be addressed through longitudinal, in vivo monitoring of different neuronal compartments. With current imaging methods, dopaminergic neurons do not readily lend themselves to such a task in any vertebrate system. We therefore expressed human wild-type aSyn in zebrafish peripheral sensory neurons, which project elaborate superficial axons that can be continuously imaged in vivo. Axonal outgrowth was normal in these neurons but, by 2 days post-fertilization (dpf, many aSyn-expressing axons became dystrophic, with focal varicosities or diffuse beading. Approximately 20% of aSyn-expressing cells died by 3 dpf. Time-lapse imaging revealed that focal axonal swelling, but not overt fragmentation, usually preceded cell death. Co-expressing aSyn with a mitochondrial reporter revealed deficits in mitochondrial transport and morphology even when axons appeared overtly normal. The axon-protective protein Wallerian degeneration slow (WldS delayed axon degeneration but not cell death caused by aSyn. By contrast, the transcriptional coactivator PGC-1α, which has roles in the regulation of mitochondrial biogenesis and reactive-oxygen-species detoxification, abrogated aSyn toxicity in both the axon and the cell body. The rapid onset of axonal pathology in this system, and the relatively moderate degree of cell death, provide a new model for the study of aSyn toxicity and protection. Moreover, the accessibility of peripheral sensory axons will allow effects of aSyn to be studied in different neuronal compartments and might have utility in

  10. Distribution of pressure-induced fast axonal transport abnormalities in primate optic nerve. An autoradiographic study.

    Science.gov (United States)

    Radius, R L

    1981-07-01

    The distribution of transport abnormalities in primate optic nerve from eyes subjected to five hours of pressure elevation (perfusion pressure of 35 mm Hg) was studied. Tissue autoradiography and electron microscopy were used to localize regions of the lamina cribrosa with increased transport interruption. A preferential involvement by this transport abnormality involved the superior, temporal, and inferior portions, to the exclusion of the nasal portion, of the optic nerve head. This observation supports the hypothesis that transport interruption seen in this model may be pertinent to the study of clinical glaucomatous neuropathy.

  11. Glia to axon RNA transfer.

    Science.gov (United States)

    Sotelo, José Roberto; Canclini, Lucía; Kun, Alejandra; Sotelo-Silveira, José Roberto; Calliari, Aldo; Cal, Karina; Bresque, Mariana; Dipaolo, Andrés; Farias, Joaquina; Mercer, John A

    2014-03-01

    The existence of RNA in axons has been a matter of dispute for decades. Evidence for RNA and ribosomes has now accumulated to a point at which it is difficult to question, much of the disputes turned to the origin of these axonal RNAs. In this review, we focus on studies addressing the origin of axonal RNAs and ribosomes. The neuronal soma as the source of most axonal RNAs has been demonstrated and is indisputable. However, the surrounding glial cells may be a supplemental source of axonal RNAs, a matter scarcely investigated in the literature. Here, we review the few papers that have demonstrated that glial-to-axon RNA transfer is not only feasible, but likely. We describe this process in both invertebrate axons and vertebrate axons. Schwann cell to axon ribosomes transfer was conclusively demonstrated (Court et al. [2008]: J. Neurosci 28:11024-11029; Court et al. [2011]: Glia 59:1529-1539). However, mRNA transfer still remains to be demonstrated in a conclusive way. The intercellular transport of mRNA has interesting implications, particularly with respect to the integration of glial and axonal function. This evolving field is likely to impact our understanding of the cell biology of the axon in both normal and pathological conditions. Most importantly, if the synthesis of proteins in the axon can be controlled by interacting glia, the possibilities for clinical interventions in injury and neurodegeneration are greatly increased.

  12. Expression, transport, and axonal sorting of neuronal CCL21 in large dense-core vesicles

    NARCIS (Netherlands)

    de Jong, Eiko K.; Vinet, Jonathan; Stanulovic, Vesna S.; Meijer, Michel; Wesseling, Evelyn; Sjollema, Klaas; Boddeke, Hendrikus W. G. M.; Biber, Knut

    2008-01-01

    Neurons are highly polarized cells, and neuron-neuron communication is based on directed transport and release of neurotransmitters, neuropeptides, and neurotrophins. Directed communication may also be attributed to neuron-microglia signaling, since neuronal damage can induce a microglia reaction at

  13. Expression, transport, and axonal sorting of neuronal CCL21 in large dense-core vesicles.

    NARCIS (Netherlands)

    Jong, E.K. de; Vinet, J.; Stanulovic, V.S.; Meijer, Michel; Wesseling, E.; Sjollema, K.; Boddeke, H.W.; Biber, K.

    2008-01-01

    Neurons are highly polarized cells, and neuron-neuron communication is based on directed transport and release of neurotransmitters, neuropeptides, and neurotrophins. Directed communication may also be attributed to neuron-microglia signaling, since neuronal damage can induce a microglia reaction at

  14. Snapin Recruits Dynein to BDNF-TrkB Signaling Endosomes for Retrograde Axonal Transport and Is Essential for Dendrite Growth of Cortical Neurons

    Directory of Open Access Journals (Sweden)

    Bing Zhou

    2012-07-01

    Full Text Available Neurotrophin signaling is crucial for neuron growth. While the “signaling endosomes” hypothesis is one of the accepted models, the molecular machinery that drives retrograde axonal transport of TrkB signaling endosomes is largely unknown. In particular, mechanisms recruiting dynein to TrkB signaling endosomes have not been elucidated. Here, using snapin deficient mice and gene rescue experiments combined with compartmentalized cultures of live cortical neurons, we reveal that Snapin, as a dynein adaptor, mediates retrograde axonal transport of TrkB signaling endosomes. Such a role is essential for dendritic growth of cortical neurons. Deleting snapin or disrupting Snapin-dynein interaction abolishes TrkB retrograde transport, impairs BDNF-induced retrograde signaling from axonal terminals to the nucleus, and decreases dendritic growth. Such defects were rescued by reintroducing the snapin gene. Our study indicates that Snapin-dynein coupling is one of the primary mechanisms driving BDNF-TrkB retrograde transport, thus providing mechanistic insights into the regulation of neuronal growth and survival.

  15. Loss of Dendritic Complexity Precedes Neurodegeneration in a Mouse Model with Disrupted Mitochondrial Distribution in Mature Dendrites

    Directory of Open Access Journals (Sweden)

    Guillermo López-Doménech

    2016-10-01

    Full Text Available Correct mitochondrial distribution is critical for satisfying local energy demands and calcium buffering requirements and supporting key cellular processes. The mitochondrially targeted proteins Miro1 and Miro2 are important components of the mitochondrial transport machinery, but their specific roles in neuronal development, maintenance, and survival remain poorly understood. Using mouse knockout strategies, we demonstrate that Miro1, as opposed to Miro2, is the primary regulator of mitochondrial transport in both axons and dendrites. Miro1 deletion leads to depletion of mitochondria from distal dendrites but not axons, accompanied by a marked reduction in dendritic complexity. Disrupting postnatal mitochondrial distribution in vivo by deleting Miro1 in mature neurons causes a progressive loss of distal dendrites and compromises neuronal survival. Thus, the local availability of mitochondrial mass is critical for generating and sustaining dendritic arbors, and disruption of mitochondrial distribution in mature neurons is associated with neurodegeneration.

  16. JIP3 regulates neuronal radial migration by mediating TrkB axonal anterograde transport in the developing cerebral cortex.

    Science.gov (United States)

    Ma, Huixian; Yu, Hui; Li, Ting; Zhao, Yan; Hou, Ming; Chen, Zheyu; Wang, Yue; Sun, Tao

    2017-04-15

    Radial migration is essential for the precise lamination and the coordinated function of the cerebral cortex. However, the molecular mechanisms for neuronal radial migration are not clear. Here, we report that c-Jun NH2-terminal kinase (JNK)-interacting protein-3 (JIP3) is highly expressed in the brain of embryonic mice and essential for radial migration. Knocking down JIP3 by in utero electroporation specifically perturbs the radial migration of cortical neurons but has no effect on neurogenesis and neuronal differentiation. Furthermore, we illustrate that JIP3 knockdown delays but does not block the migration of cortical neurons by investigating the distribution of neurons with JIP3 knocked down in the embryo and postnatal mouse. Finally, we find that JIP3 regulates cortical neuronal migration by mediating TrkB axonal anterograde transport during brain development. These findings deepen our understanding of the regulation of neuronal development by JIP3 and provide us a novel view on the regulating mechanisms of neuronal radial migration.

  17. Sequence determinants of the Caenhorhabditis elegans dopamine transporter dictating in vivo axonal export and synaptic localization.

    Science.gov (United States)

    Robinson, Sarah B; Hardaway, J Andrew; Hardie, Shannon L; Wright, Jane; Glynn, Ryan M; Bermingham, Daniel P; Han, Qiao; Sturgeon, Sarah M; Freeman, Phyllis; Blakely, Randy D

    2017-01-01

    The monoamine neurotransmitter dopamine (DA) acts across phylogeny to modulate both simple and complex behaviors. The presynaptic DA transporter (DAT) is a major determinant of DA signaling capacity in ensuring efficient extracellular DA clearance. In humans, DAT is also a major target for prescribed and abused psychostimulants. Multiple structural determinants of DAT function and regulation have been defined, though largely these findings have arisen from heterologous expression or ex vivo cell culture studies. Loss of function mutations in the gene encoding the Caenhorhabditis elegans DAT (dat-1) produces rapid immobility when animals are placed in water, a phenotype termed swimming-induced paralysis (Swip). The ability of a DA neuron-expressed, GFP-tagged DAT-1 fusion protein (GFP::DAT-1) to localize to synapses and rescue Swip in these animals provides a facile approach to define sequences supporting DAT somatic export and function in vivo. In prior studies, we found that truncation of the last 25 amino acids of the DAT-1 C-terminus (Δ25) precludes Swip rescue, supported by a deficit in GFP::DAT-1 synaptic localization. Here, we further defined the elements within Δ25 required for DAT-1 export and function in vivo. We identified two conserved motifs ((584)KW(585) and (591)PYRKR(595)) where mutation results in a failure of GFP::DAT-1 to be efficiently exported to synapses and restore DAT-1 function. The (584)KW(585) motif conforms to a sequence proposed to support SEC24 binding, ER export from the endoplasmic reticulum (ER), and surface expression of mammalian DAT proteins, whereas the (591)PYRKR(595) sequence conforms to a 3R motif identified as a SEC24 binding site in vertebrate G-protein coupled receptors. Consistent with a potential role of SEC24 orthologs in DAT-1 export, we demonstrated DA neuron-specific expression of a sec-24.2 transcriptional reporter. Mutations of the orthologous C-terminal sequences in human DAT (hDAT) significantly reduced

  18. Effects of microwave radiation on microtubules and axonal transport. [Brain and vagus nerve of rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Paulsson, L.E.; Hamnerius, Y.; McLean, W.G.

    1977-04-01

    Microwave radiation is known to have a variety of effects on man and experimental animals. We have looked for a common factor in these effects and have suggested that the action of the radiation on the subcellular structure microtubules could be such a factor. We have therefore studied the effect of 3.1 GHz pulsed microwave radiation on the chemical and functional properties of microtubules in vitro. The biological materials were obtained from albino rabbits. We have investigated the binding of colchicine in brain extracts, the polymerization of microtubules in brain extracts, and the transport of proteins in the vagus nerve during microwave irradiation. The absorbed power density was carefully determined and the temperature was kept within permissible limits. No effect of the radiation could be detected at absorbed power densities lower than 4 x 10/sup 5/ W/m/sup 3/ (mean).

  19. Electron transport chain inhibitors induce microglia activation through enhancing mitochondrial reactive oxygen species production.

    Science.gov (United States)

    Ye, Junli; Jiang, Zhongxin; Chen, Xuehong; Liu, Mengyang; Li, Jing; Liu, Na

    2016-01-15

    Reactive oxygen species (ROS) are believed to be mediators of excessive microglial activation, yet the resources and mechanism are not fully understood. Here we stimulated murine microglial BV-2 cells and primary microglial cells with different inhibitors of electron transport chain (ETC), rotenone, thenoyltrifluoroacetone (TTFA), antimycin A, and NaN3 to induce mitochondrial ROS production and we observed the role of mitochondrial ROS in microglial activation. Our results showed that ETC inhibitors resulted in significant changes in cell viability, microglial morphology, cell cycle arrest and mitochondrial ROS production in a dose-dependent manner in both primary cultural microglia and BV-2 cell lines. Moreover, ETC inhibitors, especially rotenone and antimycin A stimulated secretion of interleukin 1β (IL-1β), interleukin 6 (IL-6), interleukin 12 (IL-12) and tumor necrosis factor α (TNF-α) by microglia with marked activation of mitogen-activated proteinkinases (MAPKs) and nuclear factor κB (NF-κB), which could be blocked by specific inhibitors of MAPK and NF-κB and mitochondrial antioxidants, Mito-TEMPO. Taken together, our results demonstrated that inhibition of mitochondrial respiratory chain in microglia led to production of mitochondrial ROS and therefore may activate MAPK/NF-кB dependent inflammatory cytokines release in microglia, which indicated that mitochondrial-derived ROS were contributed to microglial activation.

  20. Sites of inhibition of mitochondrial electron transport in macrophage-injured neoplastic cells.

    Science.gov (United States)

    Granger, D L; Lehninger, A L

    1982-11-01

    Previous work has shown that injury of neoplastic cells by cytotoxic macrophages (CM) in cell culture is accompanied by inhibition of mitochondrial respiration. We have investigated the nature of this inhibition by studying mitochondrial respiration in CM-injured leukemia L1210 cells permeabilized with digitonin. CM-induced injury affects the mitochondrial respiratory chain proper. Complex I (NADH-coenzyme Q reductase) and complex II (succinate-coenzyme Q reductase) are markedly inhibited. In addition a minor inhibition of cytochrome oxidase was found. Electron transport from alpha-glycerophosphate through the respiratory chain to oxygen is unaffected and permeabilized CM-injured L1210 cells oxidizing this substrate exhibit acceptor control. However, glycerophosphate shuttle activity was found not to occur within CM-injured or uninjured L1210 cells in culture hence, alpha-glycerophosphate is apparently unavailable for mitochondrial oxidation in the intact cell. It is concluded that the failure of respiration of intact neoplastic cells injured by CM is caused by the nearly complete inhibition of complexes I and II of the mitochondrial electron transport chain. The time courses of CM-induced electron transport inhibition and arrest of L1210 cell division are examined and the possible relationship between these phenomena is discussed.

  1. Insights into the mutation-induced HHH syndrome from modeling human mitochondrial ornithine transporter-1.

    Directory of Open Access Journals (Sweden)

    Jing-Fang Wang

    Full Text Available Human mitochondrial ornithine transporter-1 is reported in coupling with the hyperornithinemia-hyperammonemia-homocitrullinuria (HHH syndrome, which is a rare autosomal recessive disorder. For in-depth understanding of the molecular mechanism of the disease, it is crucially important to acquire the 3D structure of human mitochondrial ornithine transporter-1. Since no such structure is available in the current protein structure database, we have developed it via computational approaches based on the recent NMR structure of human mitochondrial uncoupling protein (Berardi MJ, Chou JJ, et al. Nature 2011, 476:109-113. Subsequently, we docked the ligand L-ornithine into the computational structure to search for the favorable binding mode. It was observed that the binding interaction for the most favorable binding mode is featured by six remarkable hydrogen bonds between the receptor and ligand, and that the most favorable binding mode shared the same ligand-binding site with most of the homologous mitochondrial carriers from different organisms, implying that the ligand-binding sites are quite conservative in the mitochondrial carriers family although their sequences similarity is very low with 20% or so. Moreover, according to our structural analysis, the relationship between the disease-causing mutations of human mitochondrial ornithine transporter-1 and the HHH syndrome can be classified into the following three categories: (i the mutation occurs in the pseudo-repeat regions so as to change the region of the protein closer to the mitochondrial matrix; (ii the mutation is directly affecting the substrate binding pocket so as to reduce the substrate binding affinity; (iii the mutation is located in the structural region closer to the intermembrane space that can significantly break the salt bridge networks of the protein. These findings may provide useful insights for in-depth understanding of the molecular mechanism of the HHH syndrome and

  2. Insights into the mutation-induced HHH syndrome from modeling human mitochondrial ornithine transporter-1.

    Science.gov (United States)

    Wang, Jing-Fang; Chou, Kuo-Chen

    2012-01-01

    Human mitochondrial ornithine transporter-1 is reported in coupling with the hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, which is a rare autosomal recessive disorder. For in-depth understanding of the molecular mechanism of the disease, it is crucially important to acquire the 3D structure of human mitochondrial ornithine transporter-1. Since no such structure is available in the current protein structure database, we have developed it via computational approaches based on the recent NMR structure of human mitochondrial uncoupling protein (Berardi MJ, Chou JJ, et al. Nature 2011, 476:109-113). Subsequently, we docked the ligand L-ornithine into the computational structure to search for the favorable binding mode. It was observed that the binding interaction for the most favorable binding mode is featured by six remarkable hydrogen bonds between the receptor and ligand, and that the most favorable binding mode shared the same ligand-binding site with most of the homologous mitochondrial carriers from different organisms, implying that the ligand-binding sites are quite conservative in the mitochondrial carriers family although their sequences similarity is very low with 20% or so. Moreover, according to our structural analysis, the relationship between the disease-causing mutations of human mitochondrial ornithine transporter-1 and the HHH syndrome can be classified into the following three categories: (i) the mutation occurs in the pseudo-repeat regions so as to change the region of the protein closer to the mitochondrial matrix; (ii) the mutation is directly affecting the substrate binding pocket so as to reduce the substrate binding affinity; (iii) the mutation is located in the structural region closer to the intermembrane space that can significantly break the salt bridge networks of the protein. These findings may provide useful insights for in-depth understanding of the molecular mechanism of the HHH syndrome and developing effective

  3. Measurement of mitochondrial Ca2+ transport mediated by three transport proteins: VDAC1, the Na+/Ca2+ exchanger, and the Ca2+ uniporter.

    Science.gov (United States)

    Ben-Hail, Danya; Palty, Raz; Shoshan-Barmatz, Varda

    2014-02-01

    Ca(2+) is a ubiquitous cellular signal, with changes in intracellular Ca(2+) concentration not only stimulating a number of intercellular events but also triggering cell death pathways, including apoptosis. Mitochondrial Ca(2+) uptake and release play pivotal roles in cellular physiology by regulating intracellular Ca(2+) signaling, energy metabolism and cell death. Ca(2+) transport across the inner and outer mitochondrial membranes is mediated by several proteins, including channels, antiporters, and a uniporter. In this article, we present the background to several methods now established for assaying mitochondrial Ca(2+) transport activity across both mitochondrial membranes. The first of these is Ca(2+) transport mediated by the outer mitochondrial protein, the voltage-dependent anion-selective channel protein 1 (VDAC1, also known as porin 1), both as a purified protein reconstituted into a planar lipid bilayer (PLB) or into liposomes and as a mitochondrial membrane-embedded protein. The second method involves isolated mitochondria for assaying the activity of an inner mitochondrial membrane transport protein, the mitochondrial Ca(2+) uniporter (MCU) that transports Ca(2+) and is powered by the steep mitochondrial membrane potential. In the event of Ca(2+) overload, this leads to opening of the mitochondrial permeability transition pore (MPTP) and cell death. The third method describes how Na(+)-dependent mitochondrial Ca(2+) efflux mediated by mitochondrial NCLX, a member of the Na(+)/Ca(2+) exchanger superfamily, can be assayed in digitonin-permeabilized HEK-293 cells. The Ca(2+)-transport assays can be performed under various conditions and in combination with inhibitors, allowing detailed characterization of the transport activity of interest.

  4. Post-translational modification by acetylation regulates the mitochondrial carnitine/acylcarnitine transport protein.

    Science.gov (United States)

    Giangregorio, Nicola; Tonazzi, Annamaria; Console, Lara; Indiveri, Cesare

    2017-02-01

    The carnitine/acylcarnitine transporter (CACT; SLC25A20) mediates an antiport reaction allowing entry of acyl moieties in the form of acylcarnitines into the mitochondrial matrix and exit of free carnitine. The transport function of CACT is crucial for the β-oxidation pathway. In this work, it has been found that CACT is partially acetylated in rat liver mitochondria as demonstrated by anti-acetyl-lys antibody immunostaining. Acetylation was reversed by the deacetylase Sirtuin 3 in the presence of NAD(+). After treatment of the mitochondrial extract with the deacetylase, the CACT activity, assayed in proteoliposomes, increased. The half-saturation constant of the CACT was not influenced, while the V max was increased by deacetylation. Sirtuin 3 was not able to deacetylate the CACT when incubation was performed in intact mitoplasts, indicating that the acetylation sites are located in the mitochondrial matrix. Prediction on the localization of acetylated residues by bioinformatics correlates well with the experimental data. Recombinant CACT treated with acetyl-CoA was partially acetylated by non-enzymatic mechanism with a corresponding decrease of transport activity. The experimental data indicate that acetylation of CACT inhibits its transport activity, and thus may contribute to the regulation of the mitochondrial β-oxidation pathway.

  5. IFPA meeting 2015 workshop report I: placental mitochondrial function, transport systems and epigenetics.

    Science.gov (United States)

    Bianco-Miotto, T; Blundell, C; Buckberry, S; Chamley, L; Chong, S; Cottrell, E; Dawson, P; Hanna, C; Holland, O; Lewis, R M; Moritz, K; Myatt, L; Perkins, A V; Powell, T; Saffery, R; Sferruzzi-Perri, A; Sibley, C; Simmons, D; O'Tierney-Ginn, P F

    2016-12-01

    Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialized topics. At IFPA meeting 2015 there were twelve themed workshops, three of which are summarized in this report. These workshops covered areas of placental regulation and nutrient handling: 1) placental epigenetics; 2) placental mitochondrial function; 3) placental transport systems.

  6. Biguanides sensitize leukemia cells to ABT-737-induced apoptosis by inhibiting mitochondrial electron transport

    Science.gov (United States)

    Velez, Juliana; Pan, Rongqing; Lee, Jason T.C.; Enciso, Leonardo; Suarez, Marta; Duque, Jorge Eduardo; Jaramillo, Daniel; Lopez, Catalina; Morales, Ludis; Bornmann, William; Konopleva, Marina; Krystal, Gerald; Andreeff, Michael; Samudio, Ismael

    2016-01-01

    Metformin displays antileukemic effects partly due to activation of AMPK and subsequent inhibition of mTOR signaling. Nevertheless, Metformin also inhibits mitochondrial electron transport at complex I in an AMPK-independent manner, Here we report that Metformin and rotenone inhibit mitochondrial electron transport and increase triglyceride levels in leukemia cell lines, suggesting impairment of fatty acid oxidation (FAO). We also report that, like other FAO inhibitors, both agents and the related biguanide, Phenformin, increase sensitivity to apoptosis induction by the bcl-2 inhibitor ABT-737 supporting the notion that electron transport antagonizes activation of the intrinsic apoptosis pathway in leukemia cells. Both biguanides and rotenone induce superoxide generation in leukemia cells, indicating that oxidative damage may sensitize toABT-737 induced apoptosis. In addition, we demonstrate that Metformin sensitizes leukemia cells to the oligomerization of Bak, suggesting that the observed synergy with ABT-737 is mediated, at least in part, by enhanced outer mitochondrial membrane permeabilization. Notably, Phenformin was at least 10-fold more potent than Metformin in abrogating electron transport and increasing sensitivity to ABT-737, suggesting that this agent may be better suited for targeting hematological malignancies. Taken together, our results suggest that inhibition of mitochondrial metabolism by Metformin or Phenformin is associated with increased leukemia cell susceptibility to induction of intrinsic apoptosis, and provide a rationale for clinical studies exploring the efficacy of combining biguanides with the orally bioavailable derivative of ABT-737, Venetoclax. PMID:27283492

  7. Relationship between mitochondrial electron transport chain dysfunction, development, and life extension in Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Shane L Rea

    2007-10-01

    Full Text Available Prior studies have shown that disruption of mitochondrial electron transport chain (ETC function in the nematode Caenorhabditis elegans can result in life extension. Counter to these findings, many mutations that disrupt ETC function in humans are known to be pathologically life-shortening. In this study, we have undertaken the first formal investigation of the role of partial mitochondrial ETC inhibition and its contribution to the life-extension phenotype of C. elegans. We have developed a novel RNA interference (RNAi dilution strategy to incrementally reduce the expression level of five genes encoding mitochondrial proteins in C. elegans: atp-3, nuo-2, isp-1, cco-1, and frataxin (frh-1. We observed that each RNAi treatment led to marked alterations in multiple ETC components. Using this dilution technique, we observed a consistent, three-phase lifespan response to increasingly greater inhibition by RNAi: at low levels of inhibition, there was no response, then as inhibition increased, lifespan responded by monotonically lengthening. Finally, at the highest levels of RNAi inhibition, lifespan began to shorten. Indirect measurements of whole-animal oxidative stress showed no correlation with life extension. Instead, larval development, fertility, and adult size all became coordinately affected at the same point at which lifespan began to increase. We show that a specific signal, initiated during the L3/L4 larval stage of development, is sufficient for initiating mitochondrial dysfunction-dependent life extension in C. elegans. This stage of development is characterized by the last somatic cell divisions normally undertaken by C. elegans and also by massive mitochondrial DNA expansion. The coordinate effects of mitochondrial dysfunction on several cell cycle-dependent phenotypes, coupled with recent findings directly linking cell cycle progression with mitochondrial activity in C. elegans, lead us to propose that cell cycle checkpoint control

  8. Calpain-mediated cleavage of collapsin response mediator protein-2 drives acute axonal degeneration

    Science.gov (United States)

    Zhang, Jian-Nan; Michel, Uwe; Lenz, Christof; Friedel, Caroline C.; Köster, Sarah; d’Hedouville, Zara; Tönges, Lars; Urlaub, Henning; Bähr, Mathias; Lingor, Paul; Koch, Jan C.

    2016-01-01

    Axonal degeneration is a key initiating event in many neurological diseases. Focal lesions to axons result in a rapid disintegration of the perilesional axon by acute axonal degeneration (AAD) within several hours. However, the underlying molecular mechanisms of AAD are only incompletely understood. Here, we studied AAD in vivo through live-imaging of the rat optic nerve and in vitro in primary rat cortical neurons in microfluidic chambers. We found that calpain is activated early during AAD of the optic nerve and that calpain inhibition completely inhibits axonal fragmentation on the proximal side of the crush while it attenuates AAD on the distal side. A screening of calpain targets revealed that collapsin response mediator protein-2 (CRMP2) is a main downstream target of calpain activation in AAD. CRMP2-overexpression delayed bulb formation and rescued impairment of axonal mitochondrial transport after axotomy in vitro. In vivo, CRMP2-overexpression effectively protected the proximal axon from fragmentation within 6 hours after crush. Finally, a proteomic analysis of the optic nerve was performed at 6 hours after crush, which identified further proteins regulated during AAD, including several interactors of CRMP2. These findings reveal CRMP2 as an important mediator of AAD and define it as a putative therapeutic target. PMID:27845394

  9. Evidence for several cysteine transport mechanisms in the mitochondrial membranes of Arabidopsis thaliana.

    Science.gov (United States)

    Lee, Chun Pong; Wirtz, Markus; Hell, Rüdiger

    2014-01-01

    Cysteine is essential for many mitochondrial processes in plants, including translation, iron-sulfur cluster biogenesis and cyanide detoxification. Its biosynthesis is carried out by serine acetyltransferase (SAT) and O-acetylserine (thiol) lyase (OAS-TL) which can be found in the cytosol, plastids and mitochondria. Mutants lacking one compartment-specific OAS-TL isoform show viable phenotypes, leading to the hypothesis that the organellar membranes are permeable to substrates and products of the cysteine biosynthetic pathway. In this report, we show that exogenouslly supplied [(35)S]cysteine accumulates in the mitochondrial fraction and is taken up into isolated mitochondria for in organello protein synthesis. Analysis of cysteine uptake by isolated mitochondria and mitoplasts indicates that cysteine is transported by multiple facilitated mechanisms that operate in a concentration gradient-dependent manner. In addition, cysteine uptake is dependent mainly on the ΔpH across the inner membrane. The rates of mitochondrial cysteine transport can be mildly altered by specific metabolites in the cyanide detoxification-linked sulfide oxidation, but not by most substrates and products of the cysteine biosynthetic pathway. Based on these results, we propose that the transport of cysteine plays a pivotal role in regulating cellular cysteine biosynthesis as well as modulating the availability of sulfur for mitochondrial metabolism.

  10. Plasma membrane electron transport in Saccharomyces cerevisiae depends on the presence of mitochondrial respiratory subunits.

    Science.gov (United States)

    Herst, Patries M; Perrone, Gabriel G; Dawes, Ian W; Bircham, Peter W; Berridge, Michael V

    2008-09-01

    Most investigations into plasma membrane electron transport (PMET) in Saccharomyces cerevisiae have focused on the inducible ferric reductase responsible for iron uptake under iron/copper-limiting conditions. In this paper, we describe a PMET system, distinct from ferric reductase, which reduces the cell-impermeable water-soluble tetrazolium dye, 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulphophenyl)-2H-tetrazolium monosodium salt (WST-1), under normal iron/copper conditions. WST-1/1-methoxy-phenazine methosulphate reduction was unaffected by anoxia and relatively insensitive to diphenyleneiodonium. Dye reduction was increased when intracellular NADH levels were high, which, in S. cerevisiae, required deletion of numerous genes associated with NADH recycling. Genome-wide screening of all viable nuclear gene-deletion mutants of S. cerevisiae revealed that, although mitochondrial electron transport per se was not required, the presence of several nuclear and mitochondrially encoded subunits of respiratory complexes III and IV was mandatory for PMET. This suggests some form of interaction between components of mitochondrial and plasma membrane electron transport. In support of this, mitochondrial tubular networks in S. cerevisiae were shown to be located in close proximity to the plasma membrane using confocal microscopy.

  11. Hydrogen sulfide-mediated stimulation of mitochondrial electron transport involves inhibition of the mitochondrial phosphodiesterase 2A, elevation of cAMP and activation of protein kinase A.

    Science.gov (United States)

    Módis, Katalin; Panopoulos, Panagiotis; Coletta, Ciro; Papapetropoulos, Andreas; Szabo, Csaba

    2013-11-01

    Although hydrogen sulfide (H₂S) is generally known as a mitochondrial poison, recent studies show that lower concentrations of H₂S play a physiological role in the stimulation of mitochondrial electron transport and cellular bioenergetics. This effect involves electron donation at Complex II. Other lines of recent studies demonstrated that one of the biological actions of H₂S involves inhibition of cAMP and cGMP phosphodiesterases (PDEs). Given the emerging functional role of the mitochondrial isoform of cAMP PDE (PDE2A) in the regulation of mitochondrial function the current study investigated whether cAMP-dependent mechanisms participate in the stimulatory effect of NaHS on mitochondrial function. In isolated rat liver mitochondria, partial digestion studies localized PDE2A into the mitochondrial matrix. NaHS exerted a concentration-dependent inhibitory effect on recombinant PDE2A enzyme in vitro. Moreover, NaHS induced an elevation of cAMP levels when added to isolated mitochondria and stimulated the mitochondrial electron transport. The latter effect was inhibited by Rp-cAMP, an inhibitor of the cAMP-dependent protein kinase (PKA). The current findings suggest that the direct electron donating effect of NaHS is amplified by an intramitochondrial cAMP system, which may involve the inhibition of PDE2A and subsequent, cAMP-mediated stimulation of PKA.

  12. A Trypanosomatid Iron Transporter that Regulates Mitochondrial Function Is Required for Leishmania amazonensis Virulence.

    Directory of Open Access Journals (Sweden)

    Bidyottam Mittra

    2016-01-01

    Full Text Available Iron, an essential co-factor of respiratory chain proteins, is critical for mitochondrial function and maintenance of its redox balance. We previously reported a role for iron uptake in differentiation of Leishmania amazonensis into virulent amastigotes, by a mechanism that involves reactive oxygen species (ROS production and is independent of the classical pH and temperature cues. Iron import into mitochondria was proposed to be essential for this process, but evidence supporting this hypothesis was lacking because the Leishmania mitochondrial iron transporter was unknown. Here we describe MIT1, a homolog of the mitochondrial iron importer genes mrs3 (yeast and mitoferrin-1 (human that is highly conserved among trypanosomatids. MIT1 expression was essential for the survival of Trypanosoma brucei procyclic but not bloodstream forms, which lack functional respiratory complexes. L. amazonensis LMIT1 null mutants could not be generated, suggesting that this mitochondrial iron importer is essential for promastigote viability. Promastigotes lacking one LMIT1 allele (LMIT1/Δlmit1 showed growth defects and were more susceptible to ROS toxicity, consistent with the role of iron as the essential co-factor of trypanosomatid mitochondrial superoxide dismutases. LMIT1/Δlmit1 metacyclic promastigotes were unable to replicate as intracellular amastigotes after infecting macrophages or cause cutaneous lesions in mice. When induced to differentiate axenically into amastigotes, LMIT1/Δlmit1 showed strong defects in iron content and function of mitochondria, were unable to upregulate the ROS-regulatory enzyme FeSOD, and showed mitochondrial changes suggestive of redox imbalance. Our results demonstrate the importance of mitochondrial iron uptake in trypanosomatid parasites, and highlight the role of LMIT1 in the iron-regulated process that orchestrates differentiation of L. amazonensis into infective amastigotes.

  13. Glutamate transport decreases mitochondrial pH and modulates oxidative metabolism in astrocytes.

    Science.gov (United States)

    Azarias, Guillaume; Perreten, Hélène; Lengacher, Sylvain; Poburko, Damon; Demaurex, Nicolas; Magistretti, Pierre J; Chatton, Jean-Yves

    2011-03-09

    During synaptic activity, the clearance of neuronally released glutamate leads to an intracellular sodium concentration increase in astrocytes that is associated with significant metabolic cost. The proximity of mitochondria at glutamate uptake sites in astrocytes raises the question of the ability of mitochondria to respond to these energy demands. We used dynamic fluorescence imaging to investigate the impact of glutamatergic transmission on mitochondria in intact astrocytes. Neuronal release of glutamate induced an intracellular acidification in astrocytes, via glutamate transporters, that spread over the mitochondrial matrix. The glutamate-induced mitochondrial matrix acidification exceeded cytosolic acidification and abrogated cytosol-to-mitochondrial matrix pH gradient. By decoupling glutamate uptake from cellular acidification, we found that glutamate induced a pH-mediated decrease in mitochondrial metabolism that surpasses the Ca(2+)-mediated stimulatory effects. These findings suggest a model in which excitatory neurotransmission dynamically regulates astrocyte energy metabolism by limiting the contribution of mitochondria to the metabolic response, thereby increasing the local oxygen availability and preventing excessive mitochondrial reactive oxygen species production.

  14. Mitochondrial Dynamics in Mitochondrial Diseases

    Directory of Open Access Journals (Sweden)

    Juan M. Suárez-Rivero

    2016-12-01

    Full Text Available Mitochondria are very versatile organelles in continuous fusion and fission processes in response to various cellular signals. Mitochondrial dynamics, including mitochondrial fission/fusion, movements and turnover, are essential for the mitochondrial network quality control. Alterations in mitochondrial dynamics can cause neuropathies such as Charcot-Marie-Tooth disease in which mitochondrial fusion and transport are impaired, or dominant optic atrophy which is caused by a reduced mitochondrial fusion. On the other hand, mitochondrial dysfunction in primary mitochondrial diseases promotes reactive oxygen species production that impairs its own function and dynamics, causing a continuous vicious cycle that aggravates the pathological phenotype. Mitochondrial dynamics provides a new way to understand the pathophysiology of mitochondrial disorders and other diseases related to mitochondria dysfunction such as diabetes, heart failure, or Hungtinton’s disease. The knowledge about mitochondrial dynamics also offers new therapeutics targets in mitochondrial diseases.

  15. Deficiency of the mitochondrial electron transport chain in muscle does not cause insulin resistance.

    Directory of Open Access Journals (Sweden)

    Dong-Ho Han

    Full Text Available BACKGROUND: It has been proposed that muscle insulin resistance in type 2 diabetes is due to a selective decrease in the components of the mitochondrial electron transport chain and results from accumulation of toxic products of incomplete fat oxidation. The purpose of the present study was to test this hypothesis. METHODOLOGY/PRINCIPAL FINDINGS: Rats were made severely iron deficient, by means of an iron-deficient diet. Iron deficiency results in decreases of the iron containing mitochondrial respiratory chain proteins without affecting the enzymes of the fatty acid oxidation pathway. Insulin resistance was induced by feeding iron-deficient and control rats a high fat diet. Skeletal muscle insulin resistance was evaluated by measuring glucose transport activity in soleus muscle strips. Mitochondrial proteins were measured by Western blot. Iron deficiency resulted in a decrease in expression of iron containing proteins of the mitochondrial respiratory chain in muscle. Citrate synthase, a non-iron containing citrate cycle enzyme, and long chain acyl-CoA dehydrogenase (LCAD, used as a marker for the fatty acid oxidation pathway, were unaffected by the iron deficiency. Oleate oxidation by muscle homogenates was increased by high fat feeding and decreased by iron deficiency despite high fat feeding. The high fat diet caused severe insulin resistance of muscle glucose transport. Iron deficiency completely protected against the high fat diet-induced muscle insulin resistance. CONCLUSIONS/SIGNIFICANCE: The results of the study argue against the hypothesis that a deficiency of the electron transport chain (ETC, and imbalance between the ETC and β-oxidation pathways, causes muscle insulin resistance.

  16. Axonal transport of muscarinic cholinergic receptors in rat vagus nerve: high and low affinity agonist receptors move in opposite directions and differ in nucleotide sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Zarbin, M.A.; Wamsley, J.K.; Kuhar, M.J.

    1982-07-01

    The presence and transport of muscarinic cholinergic binding sites have been detected in the rat vagus nerve. These binding sites accumulate both proximal and distal to ligatures in a time-dependent manner. The results of double ligature and colchicine experiments are compatible with the notion that the anterogradely transported binding sites move by fast transport. Most of the sites accumulating proximal to ligatures bind the agonist carbachol with high affinity, while most of the sites accumulating distally bind carbachol with a low affinity. Also, the receptors transported in the anterograde direction are affected by a guanine nucleotide analogue (GppNHp), while those transported in the retrograde direction are less, or not, affected. The bulk of the sites along the unligated nerve trunk bind carbachol with a low affinity and are less sensitive to GppNHp modulation than the anterogradely transported sites. These results suggest that some receptors in the vagus may undergo axonal transport in association with regulatory proteins and that receptor molecules undergo changes in their binding and regulatory properties during their life cycle. These data also support the notion that the high and low affinity agonist form of the muscarinic receptor represent different modulated forms of a single receptor molecule.

  17. UNC-16 (JIP3) Acts Through Synapse-Assembly Proteins to Inhibit the Active Transport of Cell Soma Organelles to Caenorhabditis elegans Motor Neuron Axons.

    Science.gov (United States)

    Edwards, Stacey L; Morrison, Logan M; Yorks, Rosalina M; Hoover, Christopher M; Boominathan, Soorajnath; Miller, Kenneth G

    2015-09-01

    The conserved protein UNC-16 (JIP3) inhibits the active transport of some cell soma organelles, such as lysosomes, early endosomes, and Golgi, to the synaptic region of axons. However, little is known about UNC-16's organelle transport regulatory function, which is distinct from its Kinesin-1 adaptor function. We used an unc-16 suppressor screen in Caenorhabditis elegans to discover that UNC-16 acts through CDK-5 (Cdk5) and two conserved synapse assembly proteins: SAD-1 (SAD-A Kinase), and SYD-2 (Liprin-α). Genetic analysis of all combinations of double and triple mutants in unc-16(+) and unc-16(-) backgrounds showed that the three proteins (CDK-5, SAD-1, and SYD-2) are all part of the same organelle transport regulatory system, which we named the CSS system based on its founder proteins. Further genetic analysis revealed roles for SYD-1 (another synapse assembly protein) and STRADα (a SAD-1-interacting protein) in the CSS system. In an unc-16(-) background, loss of the CSS system improved the sluggish locomotion of unc-16 mutants, inhibited axonal lysosome accumulation, and led to the dynein-dependent accumulation of lysosomes in dendrites. Time-lapse imaging of lysosomes in CSS system mutants in unc-16(+) and unc-16(-) backgrounds revealed active transport defects consistent with the steady-state distributions of lysosomes. UNC-16 also uses the CSS system to regulate the distribution of early endosomes in neurons and, to a lesser extent, Golgi. The data reveal a new and unprecedented role for synapse assembly proteins, acting as part of the newly defined CSS system, in mediating UNC-16's organelle transport regulatory function.

  18. Mitochondrial H2O2 generated from electron transport chain complex 1 stimulates muscle differentiation

    Institute of Scientific and Technical Information of China (English)

    Seonmin Lee; Eunyoung Tak; Jisun Lee; MA Rashid; Michael P Murphy; Joohun Ha; Sung Soo Kim

    2011-01-01

    Mitochondrial reactive oxygen species(mROS)have been considered detrimental to cells. However, their physiological roles as signaling mediators have not been thoroughly explored. Here, we investigated whether mROS generated from mitochondrial electron transport chain(mETC)complex I stimulated muscle differentiation. Our results showed that the quantity of mROS was increased and that manganese superoxide dismutase(MnSOD)was induced via NF-KB activation during muscle differentiation. Mitochondria-targeted antioxidants(MitoQ and MitoTEMPOL)and mitochondria-targeted catalase decreased mROS quantity and suppressed muscle differentiation without affecting the amount of ATP Mitochondrial alterations, including the induction of mitochondrial transcription factor A and an increase in the number and size of mitochondria, and functional activations were observed during muscle differentiation. In particular, increased expression levels of mETC complex I subunits and a higher activity of complex I than other complexes were observed. Rotenone, an inhibitor of mETC complex I, decreased the mitochondrial NADH/NAD+ ratio and mROS levels during muscle differentiation. The inhibition of complex I using small interfering RNAs and rotenone reduced mROS levels, suppressed muscle differentiation, and depleted ATP levels with a concomitant increase in glycolysis. From these results, we conclude that complex I-derived O2, produced through reverse electron transport due to enhanced metabolism and a high activity of complex I, was dismutated into H2O2 by MnSOD induced via NF-KB activation and that the dismutated mH202 stimulated muscle differentiation as a signaling messenger.

  19. Disruption of the MAP1B-related Protein FUTSCH Leads to Changes in the Neuronal Cytoskeleton, Axonal Transport Defects, and Progressive Neurodegeneration in DrosophilaD⃞V⃞

    Science.gov (United States)

    da Cruz, Alexandre Bettencourt; Schwärzel, Martin; Schulze, Sabine; Niyyati, Mahtab; Heisenberg, Martin; Kretzschmar, Doris

    2005-01-01

    The elaboration of neuronal axons and dendrites is dependent on a functional cytoskeleton. Cytoskeletal components have been shown to play a major role in the maintenance of the nervous system through adulthood, and changes in neurofilaments and microtubule-associated proteins (MAPs) have been linked to a variety of neurodegenerative diseases. Here we show that Futsch, the fly homolog of MAP1B, is involved in progressive neurodegeneration. Although Futsch is widely expressed throughout the CNS, degeneration in futscholk primarily occurs in the olfactory system and mushroom bodies. Consistent with the predicted function of Futsch, we find abnormalities in the microtubule network and defects in axonal transport. Degeneration in the adult brain is preceded by learning deficits, revealing a neuronal dysfunction before detectable levels of cell death. Futsch is negatively regulated by the Drosophila Fragile X mental retardation gene, and a mutation in this gene delays the onset of neurodegeneration in futscholk. A similar effect is obtained by expression of either fly or bovine tau, suggesting a certain degree of functional redundancy of MAPs. The futscholk mutants exhibit several characteristics of human neurodegenerative diseases, providing an opportunity to study the role of MAPs in progressive neurodegeneration within an experimentally accessible, in vivo model system. PMID:15772149

  20. Disruption of the MAP1B-related protein FUTSCH leads to changes in the neuronal cytoskeleton, axonal transport defects, and progressive neurodegeneration in Drosophila.

    Science.gov (United States)

    Bettencourt da Cruz, Alexandre; Schwärzel, Martin; Schulze, Sabine; Niyyati, Mahtab; Heisenberg, Martin; Kretzschmar, Doris

    2005-05-01

    The elaboration of neuronal axons and dendrites is dependent on a functional cytoskeleton. Cytoskeletal components have been shown to play a major role in the maintenance of the nervous system through adulthood, and changes in neurofilaments and microtubule-associated proteins (MAPs) have been linked to a variety of neurodegenerative diseases. Here we show that Futsch, the fly homolog of MAP1B, is involved in progressive neurodegeneration. Although Futsch is widely expressed throughout the CNS, degeneration in futsch(olk) primarily occurs in the olfactory system and mushroom bodies. Consistent with the predicted function of Futsch, we find abnormalities in the microtubule network and defects in axonal transport. Degeneration in the adult brain is preceded by learning deficits, revealing a neuronal dysfunction before detectable levels of cell death. Futsch is negatively regulated by the Drosophila Fragile X mental retardation gene, and a mutation in this gene delays the onset of neurodegeneration in futsch(olk). A similar effect is obtained by expression of either fly or bovine tau, suggesting a certain degree of functional redundancy of MAPs. The futsch(olk) mutants exhibit several characteristics of human neurodegenerative diseases, providing an opportunity to study the role of MAPs in progressive neurodegeneration within an experimentally accessible, in vivo model system.

  1. Loss of the Coffin-Lowry syndrome-associated gene RSK2 alters ERK activity, synaptic function and axonal transport in Drosophila motoneurons

    Directory of Open Access Journals (Sweden)

    Katherina Beck

    2015-11-01

    Full Text Available Plastic changes in synaptic properties are considered as fundamental for adaptive behaviors. Extracellular-signal-regulated kinase (ERK-mediated signaling has been implicated in regulation of synaptic plasticity. Ribosomal S6 kinase 2 (RSK2 acts as a regulator and downstream effector of ERK. In the brain, RSK2 is predominantly expressed in regions required for learning and memory. Loss-of-function mutations in human RSK2 cause Coffin-Lowry syndrome, which is characterized by severe mental retardation and low IQ scores in affected males. Knockout of RSK2 in mice or the RSK ortholog in Drosophila results in a variety of learning and memory defects. However, overall brain structure in these animals is not affected, leaving open the question of the pathophysiological consequences. Using the fly neuromuscular system as a model for excitatory glutamatergic synapses, we show that removal of RSK function causes distinct defects in motoneurons and at the neuromuscular junction. Based on histochemical and electrophysiological analyses, we conclude that RSK is required for normal synaptic morphology and function. Furthermore, loss of RSK function interferes with ERK signaling at different levels. Elevated ERK activity was evident in the somata of motoneurons, whereas decreased ERK activity was observed in axons and the presynapse. In addition, we uncovered a novel function of RSK in anterograde axonal transport. Our results emphasize the importance of fine-tuning ERK activity in neuronal processes underlying higher brain functions. In this context, RSK acts as a modulator of ERK signaling.

  2. Loss of the Coffin-Lowry syndrome-associated gene RSK2 alters ERK activity, synaptic function and axonal transport in Drosophila motoneurons.

    Science.gov (United States)

    Beck, Katherina; Ehmann, Nadine; Andlauer, Till F M; Ljaschenko, Dmitrij; Strecker, Katrin; Fischer, Matthias; Kittel, Robert J; Raabe, Thomas

    2015-11-01

    Plastic changes in synaptic properties are considered as fundamental for adaptive behaviors. Extracellular-signal-regulated kinase (ERK)-mediated signaling has been implicated in regulation of synaptic plasticity. Ribosomal S6 kinase 2 (RSK2) acts as a regulator and downstream effector of ERK. In the brain, RSK2 is predominantly expressed in regions required for learning and memory. Loss-of-function mutations in human RSK2 cause Coffin-Lowry syndrome, which is characterized by severe mental retardation and low IQ scores in affected males. Knockout of RSK2 in mice or the RSK ortholog in Drosophila results in a variety of learning and memory defects. However, overall brain structure in these animals is not affected, leaving open the question of the pathophysiological consequences. Using the fly neuromuscular system as a model for excitatory glutamatergic synapses, we show that removal of RSK function causes distinct defects in motoneurons and at the neuromuscular junction. Based on histochemical and electrophysiological analyses, we conclude that RSK is required for normal synaptic morphology and function. Furthermore, loss of RSK function interferes with ERK signaling at different levels. Elevated ERK activity was evident in the somata of motoneurons, whereas decreased ERK activity was observed in axons and the presynapse. In addition, we uncovered a novel function of RSK in anterograde axonal transport. Our results emphasize the importance of fine-tuning ERK activity in neuronal processes underlying higher brain functions. In this context, RSK acts as a modulator of ERK signaling.

  3. Tumor cell death induced by the inhibition of mitochondrial electron transport: The effect of 3-hydroxybakuchiol

    Energy Technology Data Exchange (ETDEWEB)

    Jaña, Fabián [Clinical and Molecular Pharmacology Program, University of Chile, Santiago (Chile); Faini, Francesca [Department of Chemistry, Faculty of Sciences, University of Chile, Santiago (Chile); Lapier, Michel; Pavani, Mario [Clinical and Molecular Pharmacology Program, University of Chile, Santiago (Chile); Kemmerling, Ulrike [Anatomy and Developmental Biology Program, ICBM, Faculty of Medicine, University of Chile, Santiago (Chile); Morello, Antonio; Maya, Juan Diego; Jara, José [Clinical and Molecular Pharmacology Program, University of Chile, Santiago (Chile); Parra, Eduardo [Laboratory of Experimental Biomedicine, University of Tarapaca, Campus Esmeralda, Iquique (Chile); Ferreira, Jorge, E-mail: jferreir@med.uchile.cl [Clinical and Molecular Pharmacology Program, University of Chile, Santiago (Chile)

    2013-10-15

    Changes in mitochondrial ATP synthesis can affect the function of tumor cells due to the dependence of the first step of glycolysis on mitochondrial ATP. The oxidative phosphorylation (OXPHOS) system is responsible for the synthesis of approximately 90% of the ATP in normal cells and up to 50% in most glycolytic cancers; therefore, inhibition of the electron transport chain (ETC) emerges as an attractive therapeutic target. We studied the effect of a lipophilic isoprenylated catechol, 3-hydroxybakuchiol (3-OHbk), a putative ETC inhibitor isolated from Psoralea glandulosa. 3-OHbk exerted cytotoxic and anti-proliferative effects on the TA3/Ha mouse mammary adenocarcinoma cell line and induced a decrease in the mitochondrial transmembrane potential, the activation of caspase-3, the opening of the mitochondrial permeability transport pore (MPTP) and nuclear DNA fragmentation. Additionally, 3-OHbk inhibited oxygen consumption, an effect that was completely reversed by succinate (an electron donor for Complex II) and duroquinol (electron donor for Complex III), suggesting that 3-OHbk disrupted the electron flow at the level of Complex I. The inhibition of OXPHOS did not increase the level of reactive oxygen species (ROS) but caused a large decrease in the intracellular ATP level. ETC inhibitors have been shown to induce cell death through necrosis and apoptosis by increasing ROS generation. Nevertheless, we demonstrated that 3-OHbk inhibited the ETC and induced apoptosis through an interaction with Complex I. By delivering electrons directly to Complex III with duroquinol, cell death was almost completely abrogated. These results suggest that 3-OHbk has antitumor activity resulting from interactions with the ETC, a system that is already deficient in cancer cells. - Highlights: • We studied the anticancer activity of a natural compound, 3-OHbk, on TA3/Ha cells. • 3-OHbk inhibited mitochondrial electron flow by interacting with Complex I. • Complex I inhibition did

  4. Green tea polyphenols require the mitochondrial iron transporter, mitoferrin, for lifespan extension in Drosophila melanogaster.

    Science.gov (United States)

    Lopez, Terry E; Pham, Hoang M; Nguyen, Benjamin V; Tahmasian, Yerazik; Ramsden, Shannon; Coskun, Volkan; Schriner, Samuel E; Jafari, Mahtab

    2016-12-01

    Green tea has been found to increase the lifespan of various experimental animal models including the fruit fly, Drosophila melanogaster. High in polyphenolic content, green tea has been shown to reduce oxidative stress in part by its ability to bind free iron, a micronutrient that is both essential for and toxic to all living organisms. Due to green tea's iron-binding properties, we questioned whether green tea acts to increase the lifespan of the fruit fly by modulating iron regulators, specifically, mitoferrin, a mitochondrial iron transporter, and transferrin, found in the hemolymph of flies. Publicly available hypomorph mutants for these iron regulators were utilized to investigate the effect of green tea on lifespan and fertility. We identified that green tea could not increase the lifespan of mitoferrin mutants but did rescue the reduced male fertility phenotype. The effect of green tea on transferrin mutant lifespan and fertility were comparable to w(1118) flies, as observed in our previous studies, in which green tea increased male fly lifespan and reduced male fertility. Expression levels in both w(1118) flies and mutant flies, supplemented with green tea, showed an upregulation of mitoferrin but not transferrin. Total body and mitochondrial iron levels were significantly reduced by green tea supplementation in w(1118) and mitoferrin mutants but not transferrin mutant flies. Our results demonstrate that green tea may act to increase the lifespan of Drosophila in part by the regulation of mitoferrin and reduction of mitochondrial iron.

  5. Evolution of interacting proteins in the mitochondrial electron transport system in a marine copepod.

    Science.gov (United States)

    Willett, Christopher S; Burton, Ronald S

    2004-03-01

    The extensive interaction between mitochondrial-encoded and nuclear-encoded subunits of electron transport system (ETS) enzymes in mitochondria is expected to lead to intergenomic coadaptation. Whether this coadaptation results from adaptation to the environment or from fixation of deleterious mtDNA mutations followed by compensatory nuclear gene evolution is unknown. The intertidal copepod Tigriopus californicus shows extreme divergence in mtDNA sequence and provides an excellent model system for study of intergenomic coadaptation. Here, we examine genes encoding subunits of complex III of the ETS, including the mtDNA-encoded cytochrome b (CYTB), the nuclear-encoded rieske iron-sulfur protein (RISP), and cytochrome c(1) (CYC1). We compare levels of polymorphism within populations and divergence between populations in these genes to begin to untangle the selective forces that have shaped evolution in these genes. CYTB displays dramatic divergence between populations, but sequence analysis shows no evidence for positive selection driving this divergence. CYC1 and RISP have lower levels of sequence divergence between populations than CYTB, but, again, sequence analysis gives no evidence for positive selection acting on them. However, an examination of variation at cytochrome c (CYC), a nuclear-encoded protein that transfers electrons between complex III and complex IV provides evidence for selective divergence. Hence, it appears that rapid evolution in mitochondrial-encoded subunits is not always associated with rapid divergence in interacting subunits (CYC1 and RISP), but can be in some cases (CYC). Finally, a comparison of nuclear-encoded and mitochondrial-encoded genes from T. californicus suggests that substitution rates in the mitochondrial-encoded genes are dramatically increased relative to nuclear genes.

  6. Mitochondrial Electron Transport Chain in Heavy Metal-Induced Neurotoxicity: Effects of Cadmium, Mercury, and Copper

    Directory of Open Access Journals (Sweden)

    Elena A. Belyaeva

    2012-01-01

    Full Text Available To clarify the role of mitochondrial electron transport chain (mtETC in heavy-metal-induced neurotoxicity, we studied action of Cd2+, Hg2+, and Cu2+ on cell viability, intracellular reactive oxygen species formation, respiratory function, and mitochondrial membrane potential of rat cell line PC12. As found, the metals produced, although in a different way, dose- and time-dependent changes of all these parameters. Importantly, Cd2+ beginning from 10 [mu]M and already at short incubation time (3 h significantly inhibited the FCCP-uncoupled cell respiration; besides, practically the complete inhibition of the respiration was reached after 3 h incubation with 50 [mu]M Hg2+ or 500 [mu]M Cd2+, whereas even after 48 h exposure with 500 [mu]M Cu2+, only a 50% inhibition of the respiration occurred. Against the Cd2+-induced cell injury, not only different antioxidants and mitochondrial permeability transition pore inhibitors were protective but also such mtETC effectors as FCCP and stigmatellin (complex III inhibitor. However, all mtETC effectors used did not protect against the Hg2+- or Cu2+-induced cell damage. Notably, stigmatellin was shown to be one of the strongest protectors against the Cd2+-induced cell damage, producing a 15–20% increase in the cell viability. The mechanisms of the mtETC involvement in the heavy-metal-induced mitochondrial membrane permeabilization and cell death are discussed.

  7. Mitochondrial ascorbic acid transport is mediated by a low-affinity form of the sodium-coupled ascorbic acid transporter-2.

    Science.gov (United States)

    Muñoz-Montesino, Carola; Roa, Francisco J; Peña, Eduardo; González, Mauricio; Sotomayor, Kirsty; Inostroza, Eveling; Muñoz, Carolina A; González, Iván; Maldonado, Mafalda; Soliz, Carlos; Reyes, Alejandro M; Vera, Juan Carlos; Rivas, Coralia I

    2014-05-01

    Despite the fundamental importance of the redox metabolism of mitochondria under normal and pathological conditions, our knowledge regarding the transport of vitamin C across mitochondrial membranes remains far from complete. We report here that human HEK-293 cells express a mitochondrial low-affinity ascorbic acid transporter that molecularly corresponds to SVCT2, a member of the sodium-coupled ascorbic acid transporter family 2. The transporter SVCT1 is absent from HEK-293 cells. Confocal colocalization experiments with anti-SVCT2 and anti-organelle protein markers revealed that most of the SVCT2 immunoreactivity was associated with mitochondria, with minor colocalization at the endoplasmic reticulum and very low immunoreactivity at the plasma membrane. Immunoblotting of proteins extracted from highly purified mitochondrial fractions confirmed that SVCT2 protein was associated with mitochondria, and transport analysis revealed a sigmoidal ascorbic acid concentration curve with an apparent ascorbic acid transport Km of 0.6mM. Use of SVCT2 siRNA for silencing SVCT2 expression produced a major decrease in mitochondrial SVCT2 immunoreactivity, and immunoblotting revealed decreased SVCT2 protein expression by approximately 75%. Most importantly, the decreased protein expression was accompanied by a concomitant decrease in the mitochondrial ascorbic acid transport rate. Further studies using HEK-293 cells overexpressing SVCT2 at the plasma membrane revealed that the altered kinetic properties of mitochondrial SVCT2 are due to the ionic intracellular microenvironment (low in sodium and high in potassium), with potassium acting as a concentration-dependent inhibitor of SVCT2. We discarded the participation of two glucose transporters previously described as mitochondrial dehydroascorbic acid transporters; GLUT1 is absent from mitochondria and GLUT10 is not expressed in HEK-293 cells. Overall, our data indicate that intracellular SVCT2 is localized in mitochondria, is

  8. Steroidogenic acute regulatory protein (StAR), a novel mitochondrial cholesterol transporter.

    Science.gov (United States)

    Miller, Walter L

    2007-06-01

    Cholesterol is a vital component of cellular membranes, and is the substrate for biosynthesis of steroids, oxysterols and bile acids. The mechanisms directing the intracellular trafficking of this nearly insoluble molecule have received increased attention through the discovery of the steroidogenic acute regulatory protein (StAR) and similar proteins containing StAR-related lipid transfer (START) domains. StAR can transfer cholesterol between synthetic liposomes in vitro, an activity which appears to correspond to the trans-cytoplasmic transport of cholesterol to mitochondria. However, trans-cytoplasmic cholesterol transport in vivo appears to involve the recently-described protein StarD4, which is expressed in most cells. Steroidogenic cells must also move large amounts of cholesterol from the outer mitochondrial membrane to the first steroidogenic enzyme, which lies on the matrix side of the inner membrane; this action requires StAR. Congenital lipoid adrenal hyperplasia, a rare and severe disorder of human steroidogenesis, results from mutations in StAR, providing a StAR knockout of nature that has provided key insights into its activity. Cell biology experiments show that StAR moves large amounts of cholesterol from the outer to inner mitochondrial membrane, but acts exclusively on the outer membrane. Biophysical data show that only the carboxyl-terminal alpha-helix of StAR interacts with the outer membrane. Spectroscopic data and molecular dynamics simulations show that StAR's interactions with protonated phospholipid head groups on the outer mitochondrial membrane induce a conformational change (molten globule transition) needed for StAR's activity. StAR appears to act in concert with the peripheral benzodiazepine receptor, but the precise itinerary of a cholesterol molecule entering the mitochondrion remains unclear.

  9. Evaluation of the H+/site ratio of mitochondrial electron transport from rate measurements.

    Science.gov (United States)

    Reynafarje, B; Brand, M D; Lehninger, A L

    1976-12-10

    The mitochondrial H+/site ratio (i.e. the number of protons ejected per pair of electrons traversing each of the energy-conserving sites of the respiratory chain) has been evaluated employing a new experimental approach. In this method the rates of oxygen uptake and H+ ejection were measured simultaneously during the initial period of respiration evoked by addition of succinate to aerobic, rotenone-inhibited, de-energized mitochondria. Either K+, in the presence of valinomycin, or Ca2+, was used as mobile cation to dissipate the membrane potential and allow quantitative H+ ejection into the medium. The H+/site ratio observed with this method in the absence of precautions to inhibit the uptake of phosphate was close to 2.0, in agreement with values obtained using the oxygen pulse technique (Mitchell, P. and Moyle, J. (1967) Biochem. J. 105, 1147-1162). However, when phosphate movements were eliminated either by inhibition of the phosphate-hydroxide antiporter with N-ethylamaleimide or by depleting the mitochondria of their endogenous phosphate content, H+/site ratios close to 4.0 were consistently observed. This ratio was independent of the concentration of succinate, of mitochondrial protein, of pH between 6 and 8, and of ionic composition of the medium, provided that sufficient K+ (plus valinomycin) or Ca2+ were present. Specific inhibitors of the hydrolysis of endogenous ATP or transport of other ions (adenine nucleotides, tricarboxylates, HCO3-, etc.) were shown not to affect the observed H+/site ratio. Furthermore, the replacement of succinate by alpha-glycerol phosphate, a substrate which is oxidized on the outer surface of the inner membrane and thus does not need to enter the matrix, gave the same H+/site ratios as did succinate. It is concluded that the H+/site ratio of mitochondrial electron transport, when phosphate movements are eliminated, may be close to 4.0.

  10. A conserved mitochondrial ATP-binding cassette transporter exports glutathione polysulfide for cytosolic metal cofactor assembly.

    Science.gov (United States)

    Schaedler, Theresia A; Thornton, Jeremy D; Kruse, Inga; Schwarzländer, Markus; Meyer, Andreas J; van Veen, Hendrik W; Balk, Janneke

    2014-08-22

    An ATP-binding cassette transporter located in the inner mitochondrial membrane is involved in iron-sulfur cluster and molybdenum cofactor assembly in the cytosol, but the transported substrate is unknown. ATM3 (ABCB25) from Arabidopsis thaliana and its functional orthologue Atm1 from Saccharomyces cerevisiae were expressed in Lactococcus lactis and studied in inside-out membrane vesicles and in purified form. Both proteins selectively transported glutathione disulfide (GSSG) but not reduced glutathione in agreement with a 3-fold stimulation of ATPase activity by GSSG. By contrast, Fe(2+) alone or in combination with glutathione did not stimulate ATPase activity. Arabidopsis atm3 mutants were hypersensitive to an inhibitor of glutathione biosynthesis and accumulated GSSG in the mitochondria. The growth phenotype of atm3-1 was strongly enhanced by depletion of the mitochondrion-localized, GSH-dependent persulfide oxygenase ETHE1, suggesting that the physiological substrate of ATM3 contains persulfide in addition to glutathione. Consistent with this idea, a transportomics approach using mass spectrometry showed that glutathione trisulfide (GS-S-SG) was transported by Atm1. We propose that mitochondria export glutathione polysulfide, containing glutathione and persulfide, for iron-sulfur cluster assembly in the cytosol.

  11. Biphasic modulation of the mitochondrial electron transport chain in myocardial ischemia and reperfusion.

    Science.gov (United States)

    Lee, Hsin-Ling; Chen, Chwen-Lih; Yeh, Steve T; Zweier, Jay L; Chen, Yeong-Renn

    2012-04-01

    Mitochondrial electron transport chain (ETC) is the major source of reactive oxygen species during myocardial ischemia-reperfusion (I/R) injury. Ischemic defect and reperfusion-induced injury to ETC are critical in the disease pathogenesis of postischemic heart. The properties of ETC were investigated in an isolated heart model of global I/R. Rat hearts were subjected to ischemia for 30 min followed by reperfusion for 1 h. Studies of mitochondrial function indicated a biphasic modulation of electron transfer activity (ETA) and ETC protein expression during I/R. Analysis of ETAs in the isolated mitochondria indicated that complexes I, II, III, and IV activities were diminished after 30 min of ischemia but increased upon restoration of flow. Immunoblotting analysis and ultrastructural analysis with transmission electron microscopy further revealed marked downregulation of ETC in the ischemic heart and then upregulation of ETC upon reperfusion. No significant difference in the mRNA expression level of ETC was detected between ischemic and postischemic hearts. However, reperfusion-induced ETC biosynthesis in myocardium can be inhibited by cycloheximide, indicating the involvement of translational control. Immunoblotting analysis of tissue homogenates revealed a similar profile in peroxisome proliferator-activated receptor-γ coactivator-1α expression, suggesting its essential role as an upstream regulator in controlling ETC biosynthesis during I/R. Significant impairment caused by ischemic and postischemic injury was observed in the complexes I- III. Analysis of NADH ferricyanide reductase activity indicated that injury of flavoprotein subcomplex accounts for 50% decline of intact complex I activity from ischemic heart. Taken together, our findings provide a new insight into the molecular mechanism of I/R-induced mitochondrial dysfunction.

  12. AmcA - a putative mitochondrial ornithine transporter supporting fungal siderophore biosynthesis

    Directory of Open Access Journals (Sweden)

    Lukas eSchafferer

    2015-04-01

    Full Text Available Iron is an essential nutrient required for a wide range of cellular processes. The opportunistic fungal pathogen Aspergillus fumigatus employs low-molecular mass iron-specific chelators, termed siderophores, for uptake, storage and intracellular iron distribution, which play a crucial role in the pathogenicity of this fungus. Siderophore biosynthesis depends on coordination with the supply of its precursor ornithine, produced mitochondrially from glutamate or cytosolically via hydrolysis of arginine. In this study, we demonstrate a role of the putative mitochondrial transporter AmcA (AFUA_8G02760 in siderophore biosynthesis of A. fumigatus.Consistent with a role in cellular ornithine handling, AmcA-deficiency resulted in decreased cellular ornithine and arginine contents as well as decreased siderophore production on medium containing glutamine as the sole nitrogen source. In support, arginine and ornithine as nitrogen sources did not impact siderophore biosynthesis due to cytosolic ornithine availability. As revealed by Northern blot analysis, transcript levels of siderophore biosynthetic genes were unresponsive to the cellular ornithine level. In contrast to siderophore production, AmcA deficiency did only mildly decrease the cellular polyamine content, demonstrating cellular prioritization of ornithine use. Nevertheless, AmcA-deficiency increased the susceptibility of A. fumigatus to the polyamine biosynthesis inhibitor eflornithine, most likely due to the decreased ornithine pool. AmcA-deficiency decreased the growth rate particularly on ornithine as the sole nitrogen source during iron starvation and sufficiency, indicating an additional role in the metabolism and fitness of A. fumigatus, possibly in mitochondrial ornithine import. In the Galleria mellonella infection model, AmcA-deficiency did not affect virulence of A. fumigatus, most likely due to the residual siderophore production and arginine availability in this host niche.

  13. Interactive Effects of Dietary Lipid and Phenotypic Feed Efficiency on the Expression of Nuclear and Mitochondrial Genes Involved in the Mitochondrial Electron Transport Chain in Rainbow Trout

    Directory of Open Access Journals (Sweden)

    Jonathan C. Eya

    2015-04-01

    Full Text Available A 2 × 3 factorial study was conducted to evaluate the effects of dietary lipid level on the expression of mitochondrial and nuclear genes involved in electron transport chain in all-female rainbow trout Oncorhynchus mykiss. Three practical diets with a fixed crude protein content of 40%, formulated to contain 10% (40/10, 20% (40/20 and 30% (40/30 dietary lipid, were fed to apparent satiety to triplicate groups of either low-feed efficient (F120; 217.66 ± 2.24 g initial average mass or high-feed efficient (F136; 205.47 ± 1.27 g full-sib families of fish, twice per day, for 90 days. At the end of the experiment, the results showed that there is an interactive effect of the dietary lipid levels and the phenotypic feed efficiency (growth rate and feed efficiency on the expression of the mitochondrial genes nd1 (NADH dehydrogenase subunit 1, cytb (Cytochrome b, cox1 (Cytochrome c oxidase subunits 1, cox2 (Cytochrome c oxidase subunits 2 and atp6 (ATP synthase subunit 6 and nuclear genes ucp2α (uncoupling proteins 2 alpha, ucp2β (uncoupling proteins 2 beta, pparα (peroxisome proliferator-activated receptor alpha, pparβ (peroxisome proliferatoractivated receptor beta and ppargc1α (proliferator-activated receptor gamma coactivator 1 alpha in fish liver, intestine and muscle, except on ppargc1α in the muscle which was affected by the diet and the family separately. Also, the results revealed that the expression of mitochondrial genes is associated with that of nuclear genes involved in electron transport chain in fish liver, intestine and muscle. Furthermore, this work showed that the expression of mitochondrial genes parallels with the expression of genes encoding uncoupling proteins (UCP in the liver and the intestine of rainbow trout. This study for the first time presents the molecular basis of the effects of dietary lipid level on mitochondrial and nuclear genes involved in mitochondrial electron transport chain in fish.

  14. Altered expression of mitochondrial electron transport chain proteins and improved myocardial energetic state during late ischemic preconditioning

    NARCIS (Netherlands)

    J.A. Cabrera (Jesús); E.A. Ziemba (Elizabeth); L.H. Colbert (Lisa); L.B. Anderson (Lorraine); W.J. Sluiter (Wim); D.J.G.M. Duncker (Dirk); T.A. Butterick (Tammy); J. Sikora (Joseph); H.B. Ward (Herbert B.); R.F. Kelly (Rosemary); E.O. McFalls (Edward)

    2012-01-01

    textabstractAltered expression of mitochondrial electron transport proteins has been shown in early preconditioned myocardial tissue. We wished to determine whether these alterations persist in the Second Window of Protection (SWOP) and if so, whether a favorable energetic state is facilitated durin

  15. Protective role of mitochondrial K-ATP channel and mitochondrial membrane transport pore in rat kidney ischemic postconditioning

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei-liang; ZHAO Yan-li; LIU Xiao-ming; CHEN Jing; ZHANG Dong

    2011-01-01

    Background Previous studies suggested that mechanical intervention during early reperfusion, or ischemia postconditioning (Ipo), could protect kidneys against renal ischemia reperfusion injury (RIRI). However, the mechanisms responsible for this protection remain unclear. This study therefore investigated the protection afforded by Ipo in rat kidneys in vivo, and the roles of mitochondrial KATP channels (mitOKATP) and mitochondrial permeability transition pores (MPTPs), by inhibiting mitOKATP with 5-hydroxydecanoate (5-HD), and by directly detecting open MPTPs using calcein-AM and CoCl2.Methods Thirty-five male Sprague-Dawley rats were randomly assigned to sham-operation (S), ischemia-reperfusion (I/R),Ipo, ischemia reperfusion with 5-HD (I/R+5-HD), or Ipo with 5-HD (Ipo +5-HD) groups. Rats in each group were sacrificed after 6 hours of reperfusion by heart exsanguination or cervical dislocation under anesthesia. RIRI was assessed by determination of creatinine and blood urea nitrogen (BUN), and by examination of histologic sections. The roles of mitoKATP and MPTP were investigated by analyzing fluorescence intensities of mitochondria, mitochondrial membrane potential,intracellular reactive oxygen species (ROS) and intracellular calcium, using appropriate fluorescent markers. The relationship between apoptosis and RIRI was assessed by determining the apoptotic index (Al) of kidney tubular epithelial cells.Results The RIRI model was shown to be successful. Significantly higher levels of creatinine and BUN, and abnormal pathology of histologic sections, were observed in group I/R, compared with group S. 5-HD eliminated the renoprotective effects of Ipo. Mitochondrial and mitochondrial membrane potential fluorescence intensities increased, and intracellular calcium, ROS fluorescence intensities and AI decreased in group Ipo, compared with group I/R. However, mitochondrial and mitochondrial membrane potential fluorescence intensities decreased, and intracellular

  16. The mitochondrial connection in auditory neuropathy.

    Science.gov (United States)

    Cacace, Anthony T; Pinheiro, Joaquim M B

    2011-01-01

    'Auditory neuropathy' (AN), the term used to codify a primary degeneration of the auditory nerve, can be linked directly or indirectly to mitochondrial dysfunction. These observations are based on the expression of AN in known mitochondrial-based neurological diseases (Friedreich's ataxia, Mohr-Tranebjærg syndrome), in conditions where defects in axonal transport, protein trafficking, and fusion processes perturb and/or disrupt mitochondrial dynamics (Charcot-Marie-Tooth disease, autosomal dominant optic atrophy), in a common neonatal condition known to be toxic to mitochondria (hyperbilirubinemia), and where respiratory chain deficiencies produce reductions in oxidative phosphorylation that adversely affect peripheral auditory mechanisms. This body of evidence is solidified by data derived from temporal bone and genetic studies, biochemical, molecular biologic, behavioral, electroacoustic, and electrophysiological investigations.

  17. Targeting the mitochondrial electron transport chain in autism, a systematic review and synthesis of a novel therapeutic approach.

    Science.gov (United States)

    Ghanizadeh, Ahmad; Berk, Michael; Farrashbandi, Hassan; Alavi Shoushtari, Ali; Villagonzalo, Kristi-Ann

    2013-09-01

    Autism is a complex developmental disorder with an unknown etiology and without any curative treatment. The mitochondrial electron transfer chains play a major role in the production of ATP, and the generation and management of reactive oxidative stress (ROS). This paper is a systematic review of the role of the mitochondrial electron transport chain in autism, and a consequent hypothesis for treating autism is synthesized. An electronic search with pre-specified inclusion criteria was conducted in order to retrieve all the published articles about the mitochondrial electron transport chain in autism. The two databases of PUBMED and Google Scholar were searched. From one hundred twenty five retrieved titles, 12 (three case control study and 9 case reports) articles met inclusion criteria. All of the included studies indicated dysfunction of electron transport chain in autism. The mitochondrial electron transfer chain seems impaired in some children with autism and ROS production is additionally enhanced. It is hypothesized that interventions involving alternative electron shuttling may improve autism through lowering the production of ROS. In addition, it is expected that this alternative electron shuttling to cytochrome c might enhance the production of ATP which is impaired in the disorder.

  18. Computing along the axon

    Institute of Scientific and Technical Information of China (English)

    Chen Haiming; Tseren-Onolt Ishdorj; Gheorghe Pǎun

    2007-01-01

    A special form of spiking neural P systems, called axon P systems, corresponding to the activity of Ranvier nodes of neuron axon, is considered and a class of SN-like P systems where the computation is done along the axon is introduced and their language generative power is investigated.

  19. Changes of proton transportation across the inner mitochondrial membrane and H+-ATPase in endotoxic shock rats

    Institute of Scientific and Technical Information of China (English)

    LU Song-min 陆松敏; SONG Shuang-ming 宋双明; LIU Jian-cang 刘建仓; YANG He-ming 杨鹤鸣; LI Ping 李萍; WANG Zheng-guo 王正国

    2003-01-01

    Objective: To investigate the changes of proton transportation across the inner mitochondrial membrane (IMM) and H+-ATPase of hepatocytes in endotoxic shock rats.Methods: Endotoxin from E.Coil of 5.0 mg/kg or saline of 1 ml/kg was injected into the femoral vein.The rats were sacrificed pre-injection and 1, 3, 5, 8 hours after injection, and plasma and liver tissue samples were collected respectively.The liver tissue samples were used for preparation of mitochondria and submitochondrial particles (SMPs).The proton-translocation of SMPs and H+-ATPase, phospholipase A2 (PLA2) activities and malondialdehyde (MDA) content, membrane fluidities of different level of mitochondria membrane and plasma MDA content were assayed.Results: (1) Five hours after E.Coli.O111B4 injection, the maximum fluorescence quenching ACMA after adding ATP, nicotinamide adenin dinucleoacid hydrogen (NADH), and the succinate were significantly decreased (P<0.05).The time of maximum fluorescent quenching and the half time of fluorescent quenching were significantly prolonged (P<0.01), especially when NADH was used as a substrate.(2) The mitochondrial H+-ATPase activity was significantly increased at early stage of endotoxic shock (P<0.05), and significantly decreased at late stage of endotoxic shock (P<0.01).(3) The mitochondrial membrane bound PLA2 activity, plasmal and mitochondrial MDA content were significantly increased and succinate dehydrogenase (SDH) activity of mitochondria decreased markedly in endotoxic shock rats (P<0.05).(4) The mitochondrial membrane fluidity of different lipid regions was decreased, especially in the head of phospholipid.Conclusions: Proton transportation across IMM and mitochondrial H+-ATPase activity are significantly decreased in endotoxic shock.

  20. The Protective Effect of Icariin on Mitochondrial Transport and Distribution in Primary Hippocampal Neurons from 3× Tg-AD Mice.

    Science.gov (United States)

    Chen, Yijing; Han, Shuangxue; Huang, Xiuxian; Ni, Jiazuan; He, Xiaoyang

    2016-01-27

    Icariin, a pharmacologically active component isolated from the Chinese herb Epimedium, has been shown to improve spatial learning and memory abilities in Alzheimer's disease (AD) rats through inhibition of Aβ production and tau protein hyperphosphorylation. However, the potential mechanism of icariin-induced protective effects against mitochondrial dysfunctions in AD still remains unclear. In the present study, we investigated the effect of icariin on the modulation of mitochondrial transport and distribution in primary hippocampal cultures from triple-transgenic (3× Tg) AD mice. The results showed that icariin enhanced mitochondrial motility and increased mitochondrial index and mitochondrial length and size in the diseased neurons. Additionally, the expression of the key mitochondrial enzyme, pyruvate dehydrogenase-E1α (PDHE1α), and the post synaptic density protein 95 (PSD95), was preserved in AD neurons after icariin treatment, accompanied by a downregulation of Aβ and phosphorylated tau expression in the corresponding areas. Further study showed that icariin treatment resulted in a decrease in mitochondrial fission protein dynamin-related protein 1 (Drp1) and an increase in fusion protein Mitofusin 2 (Mfn2). These data indicate that icariin can promote mitochondrial transport, protect mitochondria against fragmentation and preserve the expression of mitochondrial and synaptic functional proteins in AD neurons. Thus, icariin may be a potential therapeutic complement for AD and other mitochondrial malfunction-related neuronal degenerative diseases.

  1. The Protective Effect of Icariin on Mitochondrial Transport and Distribution in Primary Hippocampal Neurons from 3× Tg-AD Mice

    Directory of Open Access Journals (Sweden)

    Yijing Chen

    2016-01-01

    Full Text Available Icariin, a pharmacologically active component isolated from the Chinese herb Epimedium, has been shown to improve spatial learning and memory abilities in Alzheimer’s disease (AD rats through inhibition of Aβ production and tau protein hyperphosphorylation. However, the potential mechanism of icariin-induced protective effects against mitochondrial dysfunctions in AD still remains unclear. In the present study, we investigated the effect of icariin on the modulation of mitochondrial transport and distribution in primary hippocampal cultures from triple-transgenic (3× Tg AD mice. The results showed that icariin enhanced mitochondrial motility and increased mitochondrial index and mitochondrial length and size in the diseased neurons. Additionally, the expression of the key mitochondrial enzyme, pyruvate dehydrogenase-E1α (PDHE1α, and the post synaptic density protein 95 (PSD95, was preserved in AD neurons after icariin treatment, accompanied by a downregulation of Aβ and phosphorylated tau expression in the corresponding areas. Further study showed that icariin treatment resulted in a decrease in mitochondrial fission protein dynamin-related protein 1 (Drp1 and an increase in fusion protein Mitofusin 2 (Mfn2. These data indicate that icariin can promote mitochondrial transport, protect mitochondria against fragmentation and preserve the expression of mitochondrial and synaptic functional proteins in AD neurons. Thus, icariin may be a potential therapeutic complement for AD and other mitochondrial malfunction-related neuronal degenerative diseases.

  2. Variation in molybdenum content across broadly distributed populations of Arabidopsis thaliana is controlled by a mitochondrial molybdenum transporter (MOT1.

    Directory of Open Access Journals (Sweden)

    Ivan Baxter

    2008-02-01

    Full Text Available Molybdenum (Mo is an essential micronutrient for plants, serving as a cofactor for enzymes involved in nitrate assimilation, sulfite detoxification, abscisic acid biosynthesis, and purine degradation. Here we show that natural variation in shoot Mo content across 92 Arabidopsis thaliana accessions is controlled by variation in a mitochondrially localized transporter (Molybdenum Transporter 1 - MOT1 that belongs to the sulfate transporter superfamily. A deletion in the MOT1 promoter is strongly associated with low shoot Mo, occurring in seven of the accessions with the lowest shoot content of Mo. Consistent with the low Mo phenotype, MOT1 expression in low Mo accessions is reduced. Reciprocal grafting experiments demonstrate that the roots of Ler-0 are responsible for the low Mo accumulation in shoot, and GUS localization demonstrates that MOT1 is expressed strongly in the roots. MOT1 contains an N-terminal mitochondrial targeting sequence and expression of MOT1 tagged with GFP in protoplasts and transgenic plants, establishing the mitochondrial localization of this protein. Furthermore, expression of MOT1 specifically enhances Mo accumulation in yeast by 5-fold, consistent with MOT1 functioning as a molybdate transporter. This work provides the first molecular insight into the processes that regulate Mo accumulation in plants and shows that novel loci can be detected by association mapping.

  3. A mild impairment of mitochondrial electron transport has sex-specific effects on lifespan and aging in mice.

    Directory of Open Access Journals (Sweden)

    Bryan G Hughes

    Full Text Available Impairments of various aspects of mitochondrial function have been associated with increased lifespan in various model organisms ranging from Caenorhabditis elegans to mice. For example, disruption of the function of the 'Rieske' iron-sulfur protein (RISP of complex III of the mitochondrial electron transport chain can result in increased lifespan in the nematode worm C. elegans. However, the mechanisms by which impaired mitochondrial function affects aging remain under investigation, including whether or not they require decreased electron transport. We have generated knock-in mice with a loss-of-function Risp mutation that is homozygous lethal. However, heterozygotes (Risp(+/P224S were viable and had decreased levels of RISP protein and complex III enzymatic activity. This decrease was sufficient to impair mitochondrial respiration and to decrease overall metabolic rate in males, but not females. These defects did not appear to exert an overtly deleterious effect on the health of the mutants, since young Risp(+/P224S mice are outwardly normal, with unaffected performance and fertility. Furthermore, biomarkers of oxidative stress were unaffected in both young and aged animals. Despite this, the average lifespan of male Risp(+/P224S mice was shortened and aged Risp(+/P224S males showed signs of more rapidly deteriorating health. In spite of these differences, analysis of Gompertz mortality parameters showed that Risp heterozygosity decreased the rate of increase of mortality with age and increased the intrinsic vulnerability to death in both sexes. However, the intrinsic vulnerability was increased more dramatically in males, which resulted in their shortened lifespan. For females, the slower acceleration of age-dependent mortality results in significantly increased survival of Risp(+/P224S mice in the second half of lifespan. These results demonstrate that even relatively small perturbations of the mitochondrial electron transport chain can

  4. Expression of the Bcl-2 family genes and complexes involved in the mitochondrial transport in prostate cancer cells.

    Science.gov (United States)

    Asmarinah, Asmarinah; Paradowska-Dogan, Agnieszka; Kodariah, Ria; Tanuhardja, Budiana; Waliszewski, Przemyslaw; Mochtar, Chaidir Arif; Weidner, Wolfgang; Hinsch, Elvira

    2014-10-01

    Alteration of molecular pathways triggering apoptosis gives raise to various pathological tissue processes, such as tumorigenesis. The mitochondrial pathway is regulated by both the genes of the Bcl-2 family and the genes encoding mitochondrial transport molecules. Those proteins allow a release of cyctochrome c through the outer mitochondrial membrane. This release activates the caspase cascade resulting in death of cells. There are at least two main transport systems associated with the family of Bcl-2 proteins that are involved in transport of molecules through the outer mitochondrial membrane, i.e., the voltage dependent anion channels (VDACs) and translocases of the outer mitochondrial membrane proteins (TOMs). We investigated the expression of genes of the Bcl-2 family, i.e., pro-apoptotic Bak and Bid, and anti-apoptotic Bcl-2; VDAC gene, i.e., VDAC1, VDAC2 and VDAC3; and TOMM genes, i.e., TOMM20, TOMM22 and TOMM40. This study was performed at the mRNA and the protein level. Fourteen paraffin embedded prostate cancer tissues and five normal prostate tissues were analyzed by the quantitative PCR array and immunohistochemistry. We found a significant increase in both mRNA expression of the anti-apoptotic Bcl-2 gene and VDAC1 gene in prostate cancer tissue in comparison with their normal counterparts. Translation of the anti-apoptotic Bcl-2 and VDAC1 genes in prostate cancer tissue was slightly increased. We observed no significant differences in the mRNA expression of the pro-apoptotic Bak and Bid genes, VDAC2 or VDAC3 genes or the three TOMM genes in these tissues. The pro-apoptotic Bax protein was downtranslated significantly in secretory cells of prostate cancer as compared to normal prostate. We suggest that this protein is a good candidate as biomarker for prostate cancer.

  5. Impaired mitochondrial energy production and ABC transporter function-A crucial interconnection in dementing proteopathies of the brain.

    Science.gov (United States)

    Pahnke, Jens; Fröhlich, Christina; Krohn, Markus; Schumacher, Toni; Paarmann, Kristin

    2013-10-01

    Ageing is the main risk factor for the development of dementing neurodegenerative diseases (NDs) and it is accompanied by the accumulation of variations in mitochondrial DNA. The resulting tissue-specific alterations in ATP production and availability cause deteriorations of cerebral clearance mechanisms that are important for the removal of toxic peptides and its aggregates. ABC transporters were shown to be the most important exporter superfamily for toxic peptides, e.g. β-amyloid and α-synuclein. Their activity is highly dependent on the availability of ATP and forms a directed energy-exporter network, linking decreased mitochondrial function with highly impaired ABC transporter activity and disease progression. In this paper, we describe a network based on interactions between ageing, energy metabolism, regeneration, accumulation of toxic peptides and the development of proteopathies of the brain with a focus on Alzheimer's disease (AD). Additionally, we provide new experimental evidence for interactions within this network in regenerative processes in AD.

  6. Composition of the mitochondrial electron transport chain in acanthamoeba castellanii: structural and evolutionary insights.

    Science.gov (United States)

    Gawryluk, Ryan M R; Chisholm, Kenneth A; Pinto, Devanand M; Gray, Michael W

    2012-11-01

    The mitochondrion, derived in evolution from an α-proteobacterial progenitor, plays a key metabolic role in eukaryotes. Mitochondria house the electron transport chain (ETC) that couples oxidation of organic substrates and electron transfer to proton pumping and synthesis of ATP. The ETC comprises several multiprotein enzyme complexes, all of which have counterparts in bacteria. However, mitochondrial ETC assemblies from animals, plants and fungi are generally more complex than their bacterial counterparts, with a number of 'supernumerary' subunits appearing early in eukaryotic evolution. Little is known, however, about the ETC of unicellular eukaryotes (protists), which are key to understanding the evolution of mitochondria and the ETC. We present an analysis of the ETC proteome from Acanthamoeba castellanii, an ecologically, medically and evolutionarily important member of Amoebozoa (sister to Opisthokonta). Data obtained from tandem mass spectrometric (MS/MS) analyses of purified mitochondria as well as ETC complexes isolated via blue native polyacrylamide gel electrophoresis are combined with the results of bioinformatic queries of sequence databases. Our bioinformatic analyses have identified most of the ETC subunits found in other eukaryotes, confirming and extending previous observations. The assignment of proteins as ETC subunits by MS/MS provides important insights into the primary structures of ETC proteins and makes possible, through the use of sensitive profile-based similarity searches, the identification of novel constituents of the ETC along with the annotation of highly divergent but phylogenetically conserved ETC subunits.

  7. Kalkitoxin Inhibits Angiogenesis, Disrupts Cellular Hypoxic Signaling, and Blocks Mitochondrial Electron Transport in Tumor Cells

    Directory of Open Access Journals (Sweden)

    J. Brian Morgan

    2015-03-01

    Full Text Available The biologically active lipopeptide kalkitoxin was previously isolated from the marine cyanobacterium Moorea producens (Lyngbya majuscula. Kalkitoxin exhibited N-methyl-d-aspartate (NMDA-mediated neurotoxicity and acted as an inhibitory ligand for voltage-sensitive sodium channels in cultured rat cerebellar granule neurons. Subsequent studies revealed that kalkitoxin generated a delayed form of colon tumor cell cytotoxicity in 7-day clonogenic cell survival assays. Cell line- and exposure time-dependent cytostatic/cytotoxic effects were previously observed with mitochondria-targeted inhibitors of hypoxia-inducible factor-1 (HIF-1. The transcription factor HIF-1 functions as a key regulator of oxygen homeostasis. Therefore, we investigated the ability of kalkitoxin to inhibit hypoxic signaling in human tumor cell lines. Kalkitoxin potently and selectively inhibited hypoxia-induced activation of HIF-1 in T47D breast tumor cells (IC50 5.6 nM. Mechanistic studies revealed that kalkitoxin inhibits HIF-1 activation by suppressing mitochondrial oxygen consumption at electron transport chain (ETC complex I (NADH-ubiquinone oxidoreductase. Further studies indicate that kalkitoxin targets tumor angiogenesis by blocking the induction of angiogenic factors (i.e., VEGF in tumor cells.

  8. Cannabinoid receptor 1 signalling dampens activity and mitochondrial transport in networks of enteric neurones.

    Science.gov (United States)

    Boesmans, W; Ameloot, K; van den Abbeel, V; Tack, J; Vanden Berghe, P

    2009-09-01

    Cannabinoid (CB) receptors are expressed in the enteric nervous system (ENS) and CB(1) receptor activity slows down motility and delays gastric emptying. This receptor system has become an important target for GI-related drug development such as in obesity treatment. The aim of the study was to investigate how CB(1) ligands and antagonists affect ongoing activity in enteric neurone networks, modulate synaptic vesicle cycling and influence mitochondrial transport in nerve processes. Primary cultures of guinea-pig myenteric neurones were loaded with different fluorescent markers: Fluo-4 to measure network activity, FM1-43 to image synaptic vesicles and Mitotracker green to label mitochondria. Synaptic vesicle cluster density was assessed by immunohistochemistry and expression of CB(1) receptors was confirmed by RT-PCR. Spontaneous network activity, displayed by both excitatory and inhibitory neurones, was significantly increased by CB(1) receptor antagonists (AM-251 and SR141716), abolished by CB(1) activation (methanandamide, mAEA) and reduced by two different inhibitors (arachidonylamide serotonin, AA-5HT and URB597) of fatty acid amide hydrolase. Antagonists reduced the number of synaptic vesicles that were recycled during an electrical stimulus. CB(1) agonists (mAEA and WIN55,212) reduced and antagonists enhanced the fraction of transported mitochondria in enteric nerve fibres. We found immunohistochemical evidence for an enhancement of synaptophysin-positive release sites with SR141716, while WIN55,212 caused a reduction. The opposite effects of agonists and antagonists suggest that enteric nerve signalling is under the permanent control of CB(1) receptor activity. Using inhibitors of the endocannabinoid degrading enzyme, we were able to show there is endogenous production of a CB ligand in the ENS.

  9. Nutritional and Hormonal Regulation of Citrate and Carnitine/Acylcarnitine Transporters: Two Mitochondrial Carriers Involved in Fatty Acid Metabolism

    Directory of Open Access Journals (Sweden)

    Anna M. Giudetti

    2016-05-01

    Full Text Available The transport of solutes across the inner mitochondrial membrane is catalyzed by a family of nuclear-encoded membrane-embedded proteins called mitochondrial carriers (MCs. The citrate carrier (CiC and the carnitine/acylcarnitine transporter (CACT are two members of the MCs family involved in fatty acid metabolism. By conveying acetyl-coenzyme A, in the form of citrate, from the mitochondria to the cytosol, CiC contributes to fatty acid and cholesterol synthesis; CACT allows fatty acid oxidation, transporting cytosolic fatty acids, in the form of acylcarnitines, into the mitochondrial matrix. Fatty acid synthesis and oxidation are inversely regulated so that when fatty acid synthesis is activated, the catabolism of fatty acids is turned-off. Malonyl-CoA, produced by acetyl-coenzyme A carboxylase, a key enzyme of cytosolic fatty acid synthesis, represents a regulator of both metabolic pathways. CiC and CACT activity and expression are regulated by different nutritional and hormonal conditions. Defects in the corresponding genes have been directly linked to various human diseases. This review will assess the current understanding of CiC and CACT regulation; underlining their roles in physio-pathological conditions. Emphasis will be placed on the molecular basis of the regulation of CiC and CACT associated with fatty acid metabolism.

  10. The homeobox protein CEH-23 mediates prolonged longevity in response to impaired mitochondrial electron transport chain in C. elegans.

    Directory of Open Access Journals (Sweden)

    Ludivine Walter

    2011-06-01

    Full Text Available Recent findings indicate that perturbations of the mitochondrial electron transport chain (METC can cause extended longevity in evolutionarily diverse organisms. To uncover the molecular basis of how altered METC increases lifespan in C. elegans, we performed an RNAi screen and revealed that three predicted transcription factors are specifically required for the extended longevity of mitochondrial mutants. In particular, we demonstrated that the nuclear homeobox protein CEH-23 uniquely mediates the longevity but not the slow development, reduced brood size, or resistance to oxidative stress associated with mitochondrial mutations. Furthermore, we showed that ceh-23 expression levels are responsive to altered METC, and enforced overexpression of ceh-23 is sufficient to extend lifespan in wild-type background. Our data point to mitochondria-to-nucleus communications to be key for longevity determination and highlight CEH-23 as a novel longevity factor capable of responding to mitochondrial perturbations. These findings provide a new paradigm for how mitochondria impact aging and age-dependent diseases.

  11. Present status of studies on diffuse axonal injury

    Institute of Scientific and Technical Information of China (English)

    Jie Ma; Chonggong Zhang; Yi Li

    2006-01-01

    OBJECTIVE: To explain the present status of study on diffuse axonal injury,investigate its pathogenesis and pathophysiological changes ,and suggest principles for the diagnosis and treatment.DATA SOURCES: Articles about diffuse axonal injury published in English from January 1994 to October 2006 were searched in Pubmed database using the keywords of "diffuse axonal injury,pathogenesis,therapy".STUDY SELECTION: The collected articles were primarily screened to select those associated with diffuse axonal injury,the obviously irrelated articles were excluded,and the rest ones were retrieved manually,and the full-texes were searched.DATA EXTRACTION: Totally 98 articles were collected,41 of them were involved.and the other 57 were excluded.DATA SYNTHESIS: Diffuse axonal injury is mainly caused by acceleratory or deceleratory injury,and its pathophysiological change is a progressive duration,local axonal injury finally develops to axonal breakage,mainly includes inactivation of natrium channel,intracellular Ca2+ overloading,activation of calcium protease,caspase etc.,and mitochondrial injury.At present,there is still lack of effective therapeutic methods for diffuse axonal injury,so we should actively explore more effective methods to relieve the pain of patients and improve their prognosis.CONCLUSION: At present,diffuse axonal injury has not attracted enough attentions in China,the mechanisms for its diagnosis and attack are still unclear,and the treatments are mainly aiming at the symptoms.

  12. The central role of mitochondria in axonal degeneration in multiple sclerosis.

    Science.gov (United States)

    Campbell, Graham R; Worrall, Joseph T; Mahad, Don J

    2014-12-01

    Neurodegeneration in multiple sclerosis (MS) is related to inflammation and demyelination. In acute MS lesions and experimental autoimmune encephalomyelitis focal immune attacks damage axons by injuring axonal mitochondria. In progressive MS, however, axonal damage occurs in chronically demyelinated regions, myelinated regions and also at the active edge of slowly expanding chronic lesions. How axonal energy failure occurs in progressive MS is incompletely understood. Recent studies show that oligodendrocytes supply lactate to myelinated axons as a metabolic substrate for mitochondria to generate ATP, a process which will be altered upon demyelination. In addition, a number of studies have identified mitochondrial abnormalities within neuronal cell bodies in progressive MS, leading to a deficiency of mitochondrial respiratory chain complexes or enzymes. Here, we summarise the mitochondrial abnormalities evident within neurons and discuss how these grey matter mitochondrial abnormalities may increase the vulnerability of axons to degeneration in progressive MS. Although neuronal mitochondrial abnormalities will culminate in axonal degeneration, understanding the different contributions of mitochondria to the degeneration of myelinated and demyelinated axons is an important step towards identifying potential therapeutic targets for progressive MS.

  13. Axonal GABAA receptors.

    Science.gov (United States)

    Trigo, Federico F; Marty, Alain; Stell, Brandon M

    2008-09-01

    Type A GABA receptors (GABA(A)Rs) are well established as the main inhibitory receptors in the mature mammalian forebrain. In recent years, evidence has accumulated showing that GABA(A)Rs are prevalent not only in the somatodendritic compartment of CNS neurons, but also in their axonal compartment. Evidence for axonal GABA(A)Rs includes new immunohistochemical and immunogold data: direct recording from single axonal terminals; and effects of local applications of GABA(A)R modulators on action potential generation, on axonal calcium signalling, and on neurotransmitter release. Strikingly, whereas presynaptic GABA(A)Rs have long been considered inhibitory, the new studies in the mammalian brain mostly indicate an excitatory action. Depending on the neuron that is under study, axonal GABA(A)Rs can be activated by ambient GABA, by GABA spillover, or by an autocrine action, to increase either action potential firing and/or transmitter release. In certain neurons, the excitatory effects of axonal GABA(A)Rs persist into adulthood. Altogether, axonal GABA(A)Rs appear as potent neuronal modulators of the mammalian CNS.

  14. Atomic Force Microscopy Reveals Important Differences in Axonal Resistance to Injury

    Science.gov (United States)

    Magdesian, Margaret H.; Sanchez, Fernando S.; Lopez, Monserratt; Thostrup, Peter; Durisic, Nela; Belkaid, Wiam; Liazoghli, Dalinda; Grütter, Peter; Colman, David R.

    2012-01-01

    Axonal degeneration after traumatic brain injury and nerve compression is considered a common underlying cause of temporary as well as permanent disability. Because a proper functioning of neural network requires phase coherence of all components, even subtle changes in circuitry may lead to network failure. However, it is still not possible to determine which axons will recover or degenerate after injury. Several groups have studied the pressure threshold for axonal injury within a nerve, but difficulty accessing the injured region; insufficient imaging methods and the extremely small dimensions involved have prevented the evaluation of the response of individual axons to injury. We combined microfluidics with atomic force microscopy and in vivo imaging to estimate the threshold force required to 1), uncouple axonal transport without impairing axonal survival, and 2), compromise axonal survival in both individual and bundled axons. We found that rat hippocampal axons completely recover axonal transport with no detectable axonal loss when compressed with pressures up to 65 ± 30 Pa for 10 min, while dorsal root ganglia axons can resist to pressures up to 540 ± 220 Pa. We investigated the reasons for the differential susceptibility of hippocampal and DRG axons to mechanical injury and estimated the elasticity of live axons. We found that dorsal root ganglia axons have a 20% lower elastic modulus than hippocampal axons. Our results emphasize the importance of the integrity of the axonal cytoskeleton in deciding the axonal fate after damage and open up new avenues to improve injury diagnosis and to identify ways to protect axons. PMID:22947856

  15. Axons take a dive

    Science.gov (United States)

    Tong, Cheuk Ka; Cebrián-Silla, Arantxa; Paredes, Mercedes F; Huang, Eric J; García-Verdugo, Jose Manuel; Alvarez-Buylla, Arturo

    2015-01-01

    In the walls of the lateral ventricles of the adult mammalian brain, neural stem cells (NSCs) and ependymal (E1) cells share the apical surface of the ventricular–subventricular zone (V–SVZ). In a recent article, we show that supraependymal serotonergic (5HT) axons originating from the raphe nuclei in mice form an extensive plexus on the walls of the lateral ventricles where they contact E1 cells and NSCs. Here we further characterize the contacts between 5HT supraependymal axons and E1 cells in mice, and show that suprependymal axons tightly associated to E1 cells are also present in the walls of the human lateral ventricles. These observations raise interesting questions about the function of supraependymal axons in the regulation of E1 cells. PMID:26413556

  16. Inactivation of brain mitochondrial Lon protease by peroxynitrite precedes electron transport chain dysfunction

    DEFF Research Database (Denmark)

    Stanyer, Lee; Jørgensen, Wenche; Hori, Osamu;

    2008-01-01

    more sensitive than basal Lon protease activity. Furthermore, supplementation of mitochondrial matrix extracts with reduced glutathione, following ONOO(-) exposure, resulted in partial restoration of basal and ATP-stimulated activity, thus suggesting possible redox regulation of this enzyme complex....... Taken together these findings suggest that Lon protease may be particularly vulnerable to inactivation in conditions associated with GSH depletion and elevated oxidative stress....

  17. TGFβ1 downregulates neurite outgrowth, expression of Ca2+ transporters, and mitochondrial dynamics of in vitro cerebellar granule cells.

    Science.gov (United States)

    Jaskova, Katarina; Pavlovicova, Michaela; Cagalinec, Michal; Lacinova, Lubica; Jurkovicova, Dana

    2014-03-26

    Acute injury to central nervous system (CNS) triggers neurodegenerative processes that can result in serious damage or complete loss of function. After injury, production of transforming growth factor β1 (TGFβ1) increases and initiates creation of a fibrotic scar that prevents normal growth, plasticity, and recovery of damaged neurons. Administration of TGFβ1 antagonists can prevent its pathological effects. To define consequences of increased TGFβ1 release on calcium signaling, neuronal plasticity, excitability, and mitochondrial dynamics in CNS neurons we directly exposed a rat primary culture of cerebellar granule neurons to TGFβ1. We focused on changes in expression of intracellular calcium transporters, especially inositol-1,4,5-trisphosphate receptor (IP3R) type 1, mitochondrial dynamics, and membrane excitability. TGFβ1 significantly decreased the gene and protein expression of inositol-1,4,5-trisphosphate receptor type 1 and the gene expression of additional intracellular Ca transporters such as IP3R2, ryanodine receptor type 1 (RyR1), RyR2, and SERCA2. Altered calcium signaling suppressed neurite outgrowth and significantly decreased the length of the mitochondria and the frequency of mitochondrial fusion. The resting membrane potential of cerebellar granule neurons was hyperpolarized and slow after depolarization of single action potential was suppressed. LY364947, a blocker of TGFβ1 receptor I, prevented these effects, and IP3 receptor blocker 2-aminoethoxydiphenyl borate (2APB) mimicked them. After CNS injury TGFβ1 downregulates intracellular Ca levels and alters Ca signaling within injured neurons. We suggest that in our model TGFβ1 may trigger both neurodegenerative and neuroprotective events through IP3-induced Ca signaling.

  18. Axonal bleb recording

    Institute of Scientific and Technical Information of China (English)

    Wenqin Hu; Yousheng Shu

    2012-01-01

    Patch-clamp recording requires direct accessibility of the cell membrane to patch pipettes and allows the investigation of ion channel properties and functions in specific cellular compartments.The cell body and relatively thick dendrites are the most accessible compartments of a neuron,due to their large diameters and therefore great membrane surface areas.However,axons are normally inaccessible to patch pipettes because of their thin structure; thus studies of axon physiology have long been hampered by the lack of axon recording methods.Recently,a new method of patchclamp recording has been developed,enabling direct and tight-seal recording from cortical axons.These recordings are performed at the enlarged structure (axonal bleb) formed at the cut end of an axon after slicing procedures.This method has facilitated studies of the mechanisms underlying the generation and propagation of the main output signal,the action potential,and led to the finding that cortical neurons communicate not only in action potential-mediated digital mode but also in membrane potential-dependent analog mode.

  19. Sodium Channels, Mitochondria, and Axonal Degeneration in Peripheral Neuropathy.

    Science.gov (United States)

    Persson, Anna-Karin; Hoeijmakers, Janneke G J; Estacion, Mark; Black, Joel A; Waxman, Stephen G

    2016-05-01

    Peripheral neuropathy results from damage to peripheral nerves and is often accompanied by pain in affected limbs. Treatment represents an unmet medical need and a thorough understanding of the mechanisms underlying axonal injury is needed. Longer nerve fibers tend to degenerate first (length-dependence), and patients carrying pathogenic mutations throughout life usually become symptomatic in mid- or late-life (time-dependence). The activity of voltage-gated sodium channels can contribute to axonal injury and sodium channel gain-of-function mutations have been linked to peripheral neuropathy. Recent studies have implicated sodium channel activity, mitochondrial compromise, and reverse-mode Na(+)/Ca(2+) exchange in time- and length-dependent axonal injury. Elucidation of molecular mechanisms underlying axonal injury in peripheral neuropathy may provide new therapeutic strategies for this painful and debilitating condition.

  20. Mitochondrial electron transport chain dysfunction during development does not extend lifespan in Drosophila melanogaster.

    Science.gov (United States)

    Rera, Michael; Monnier, Véronique; Tricoire, Hervé

    2010-02-01

    Since the initial identification of reactive oxygen species (ROS) as the major factor in aging, many studies have provided evidence for the central role of mitochondria in longevity. A few years ago, an unexpected finding showed that the inactivation of the mitochondrial respiratory chain (MRC) in Caenorhabditis elegans, during the developmental stages only, extended lifespan. Activation of this mitochondrial pathway affecting aging (MIT) is associated with several phenotypic features: increased longevity, increased time of development, decreased fertility/fecundity and reduced adult size. Here, we investigated this pathway in another model organism, Drosophila melanogaster. To assess the role of mitochondrial activity in the Drosophila aging process, we partially inactivated the MRC using RNA interference (RNAi) during larval stages. Developmental perturbation of the respiratory process prolonged development, increased lethality during developmental stage, reduced both fecundity and fertility and slightly reduced individual weight. However, in contrast to the nematode, this genetic intervention either shortened or had no effect on lifespan, depending on the level of gene inactivation. Thus, the effects of MRC disruption during development on aging differ between species. We discuss the possible origins of such differences.

  1. The human and mouse SLC25A29 mitochondrial transporters rescue the deficient ornithine metabolism in fibroblasts of patients with the hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome.

    Science.gov (United States)

    Camacho, José A; Rioseco-Camacho, Natalia

    2009-07-01

    The hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a disorder of the urea cycle (UCD) and ornithine degradation pathway caused by mutations in the mitochondrial ornithine transporter (ORNT1). Unlike other UCDs, HHH syndrome is characterized by a less severe and variable phenotype that we believe may, in part, be due to genes with redundant function to ORNT1, such as the previously characterized ORNT2 gene. We reasoned that SLC25A29, a member of the same subfamily of mitochondrial carrier proteins as ORNT1 and ORNT2, might also have overlapping function with ORNT1. Here, we report that both the human and mouse SLC25A29, previously identified as mitochondrial carnitine/acyl-carnitine transporter-like, when overexpressed transiently also rescues the impaired ornithine transport in cultured HHH fibroblasts. Moreover, we observed that, in the mouse, the Slc25a29 message is more significantly expressed in the CNS and cultured astrocytes when compared with the liver and kidney. These results suggest a potential physiologic role for the SLC25A29 transporter in the oxidation of fatty acids, ornithine degradation pathway, and possibly the urea cycle. Our results show that SLC25A29 is the third human mitochondrial ornithine transporter, designated as ORNT3, which may contribute to the milder and variable phenotype seen in patients with HHH syndrome.

  2. Protein phosphorylation: Localization in regenerating optic axons

    Energy Technology Data Exchange (ETDEWEB)

    Larrivee, D. (Cornell Univ. Medical College, New York, NY (USA))

    1990-09-01

    A number of axonal proteins display changes in phosphorylation during goldfish optic nerve regeneration. (1) To determine whether the phosphorylation of these proteins was closely linked to their synthesis in the retinal ganglion cell body, cycloheximide was injected intraocularly into goldfish whose optic nerves had been regenerating for 3 weeks. Cycloheximide reduced the incorporation of (3H)proline and 32P orthophosphate into total nerve protein by 84% and 46%, respectively. Of the 20 individual proteins examined, 17 contained less than 15% of the (3H)proline label measured in corresponding controls, whereas 18 proteins contained 50% or more of the 32P label, suggesting that phosphorylation was largely independent of synthesis. (2) To determine whether the proteins were phosphorylated in the ganglion cell axons, axonal transport of proteins was blocked by intraocular injection of vincristine. Vincristine reduced (3H)proline labeling of total protein by 88% and 32P labeling by 49%. Among the individual proteins (3H)proline labeling was reduced by 90% or more in 18 cases but 32P labeling was reduced only by 50% or less. (3) When 32P was injected into the cranial cavity near the ends of the optic axons, all of the phosphoproteins were labeled more intensely in the optic tract than in the optic nerve. These results suggest that most of the major phosphoproteins that undergo changes in phosphorylation in the course of regeneration are phosphorylated in the optic axons.

  3. KLP6: a newly identified kinesin that regulates the morphology and transport of mitochondria in neuronal cells.

    Science.gov (United States)

    Tanaka, Kousuke; Sugiura, Yoshimi; Ichishita, Ryohei; Mihara, Katsuyoshi; Oka, Toshihiko

    2011-07-15

    Mitochondria utilize diverse cytoskeleton-based mechanisms to control their functions and morphology. Here, we report a role for kinesin-like protein KLP6, a newly identified member of the kinesin family, in mitochondrial morphology and dynamics. An RNA interference screen using Caenorhabditis elegans led us to identify a C. elegans KLP-6 involved in maintaining mitochondrial morphology. We cloned a cDNA coding for a rat homolog of C. elegans KLP-6, which is an uncharacterized kinesin in vertebrates. A rat KLP6 mutant protein lacking the motor domain induced changes in mitochondrial morphology and significantly decreased mitochondrial motility in HeLa cells, but did not affect the morphology of other organelles. In addition, the KLP6 mutant inhibited transport of mitochondria during anterograde movement in differentiated neuro 2a cells. To date, two kinesins, KIF1Bα and kinesin heavy chain (KHC; also known as KIF5) have been shown to be involved in the distribution of mitochondria in neurons. Expression of the kinesin heavy chain/KIF5 mutant prevented mitochondria from entering into neurites, whereas both the KLP6 and KIF1Bα mutants decreased mitochondrial transport in axonal neurites. Furthermore, both KLP6 and KIF1Bα bind to KBP, a KIF1-binding protein required for axonal outgrowth and mitochondrial distribution. Thus, KLP6 is a newly identified kinesin family member that regulates mitochondrial morphology and transport.

  4. Aspergillus fumigatus mitochondrial electron transport chain mediates oxidative stress homeostasis, hypoxia responses, and fungal pathogenesis

    Science.gov (United States)

    Grahl, Nora; Dinamarco, Taisa Magnani; Willger, Sven D.; Goldman, Gustavo H.; Cramer, Robert A.

    2012-01-01

    Summary We previously observed that hypoxia is an important component of host microenvironments during pulmonary fungal infections. However, mechanisms of fungal growth in these in vivo hypoxic conditions are poorly understood. Here, we report that mitochondrial respiration is active in hypoxia (1% oxygen) and critical for fungal pathogenesis. We generated Aspergillus fumigatus alternative oxidase (aoxA) and cytochrome C (cycA) null mutants and assessed their ability to tolerate hypoxia, macrophage killing, and virulence. In contrast to ΔaoxA, ΔcycA was found to be significantly impaired in conidia germination, growth in normoxia and hypoxia, and displayed attenuated virulence. Intriguingly, loss of cycA results in increased levels of AoxA activity, which results in increased resistance to oxidative stress, macrophage killing, and long-term persistence in murine lungs. Thus, our results demonstrate a previously unidentified role for fungal mitochondrial respiration in the pathogenesis of aspergillosis, and lay the foundation for future research into its role in hypoxia signaling and adaptation. PMID:22443190

  5. Elevated mRNA-levels of distinct mitochondrial and plasma membrane Ca2+ transporters in individual hypoglossal motor neurons of endstage SOD1 transgenic mice.

    Directory of Open Access Journals (Sweden)

    Tobias eMühling

    2014-11-01

    Full Text Available Disturbances in Ca2+ homeostasis and mitochondrial dysfunction have emerged as major pathogenic features in familial and sporadic forms of Amyotrophic Lateral Sclerosis (ALS, a fatal degenerative motor neuron disease. However, the distinct molecular ALS-pathology remains unclear. Recently, an activity-dependent Ca2+ homeostasis deficit, selectively in highly vulnerable cholinergic motor neurons in the hypoglossal nucleus (hMNs from a common ALS mouse model, endstage superoxide dismutase SOD1G93A transgenic mice, was described. This functional deficit was defined by a reduced hMN mitochondrial Ca2+ uptake capacity and elevated Ca2+ extrusion across the plasma membrane. To address the underlying molecular mechanisms, here we quantified mRNA-levels of respective potential mitochondrial and plasma membrane Ca2+ transporters in individual, choline-acetyltransferase (ChAT positive hMNs from wildtype (WT and endstage SOD1G93A mice, by combining UV laser microdissection with RT-qPCR techniques, and specific data normalization. As ChAT cDNA levels as well as cDNA and genomic DNA levels of the mitochondrially encoded NADH dehydrogenase ND1 were not different between hMNs from WT and endstage SOD1G93A mice, these genes were used to normalize hMN-specific mRNA-levels of plasma membrane and mitochondrial Ca2+ transporters, respectively. We detected about 2-fold higher levels of the mitochondrial Ca2+ transporters MCU/MICU1, Letm1 and UCP2 in remaining hMNs from endstage SOD1G93A mice. These higher expression-levels of mitochondrial Ca2+ transporters in individual hMNs were not associated with a respective increase in number of mitochondrial genomes, as evident from hMN specific ND1 DNA quantification. Normalized mRNA-levels for the plasma membrane Na2+/Ca2+exchanger NCX1 was also about 2-fold higher in hMNs from SOD1G93A mice. Thus, pharmacological stimulation of Ca2+ transporters in highly vulnerable hMNs might offer a novel neuroprotective strategy for ALS.

  6. Supercomplex assembly determines electron flux in the mitochondrial electron transport chain.

    Science.gov (United States)

    Lapuente-Brun, Esther; Moreno-Loshuertos, Raquel; Acín-Pérez, Rebeca; Latorre-Pellicer, Ana; Colás, Carmen; Balsa, Eduardo; Perales-Clemente, Ester; Quirós, Pedro M; Calvo, Enrique; Rodríguez-Hernández, M A; Navas, Plácido; Cruz, Raquel; Carracedo, Ángel; López-Otín, Carlos; Pérez-Martos, Acisclo; Fernández-Silva, Patricio; Fernández-Vizarra, Erika; Enríquez, José Antonio

    2013-06-28

    The textbook description of mitochondrial respiratory complexes (RCs) views them as free-moving entities linked by the mobile carriers coenzyme Q (CoQ) and cytochrome c (cyt c). This model (known as the fluid model) is challenged by the proposal that all RCs except complex II can associate in supercomplexes (SCs). The proposed SCs are the respirasome (complexes I, III, and IV), complexes I and III, and complexes III and IV. The role of SCs is unclear, and their existence is debated. By genetic modulation of interactions between complexes I and III and III and IV, we show that these associations define dedicated CoQ and cyt c pools and that SC assembly is dynamic and organizes electron flux to optimize the use of available substrates.

  7. Brain-derived neurotrophic factor (BDNF)-induced mitochondrial motility arrest and presynaptic docking contribute to BDNF-enhanced synaptic transmission.

    Science.gov (United States)

    Su, Bo; Ji, Yun-Song; Sun, Xu-lu; Liu, Xiang-Hua; Chen, Zhe-Yu

    2014-01-17

    Appropriate mitochondrial transport and distribution are essential for neurons because of the high energy and Ca(2+) buffering requirements at synapses. Brain-derived neurotrophic factor (BDNF) plays an essential role in regulating synaptic transmission and plasticity. However, whether and how BDNF can regulate mitochondrial transport and distribution are still unclear. Here, we find that in cultured hippocampal neurons, application of BDNF for 15 min decreased the percentage of moving mitochondria in axons, a process dependent on the activation of the TrkB receptor and its downstream PI3K and phospholipase-Cγ signaling pathways. Moreover, the BDNF-induced mitochondrial stopping requires the activation of transient receptor potential canonical 3 and 6 (TRPC3 and TRPC6) channels and elevated intracellular Ca(2+) levels. The Ca(2+) sensor Miro1 plays an important role in this process. Finally, the BDNF-induced mitochondrial stopping leads to the accumulation of more mitochondria at presynaptic sites. Mutant Miro1 lacking the ability to bind Ca(2+) prevents BDNF-induced mitochondrial presynaptic accumulation and synaptic transmission, suggesting that Miro1-mediated mitochondrial motility is involved in BDNF-induced mitochondrial presynaptic docking and neurotransmission. Together, these data suggest that mitochondrial transport and distribution play essential roles in BDNF-mediated synaptic transmission.

  8. Gem1 and ERMES Do Not Directly Affect Phosphatidylserine Transport from ER to Mitochondria or Mitochondrial Inheritance

    DEFF Research Database (Denmark)

    Nguyen, Tammy T; Lewandowska, Agnieszka; Choi, Jae-Yeon;

    2012-01-01

    a primary role for ERMES in mitochondrial association with actin and mitochondrial movement. Finally, we show that ERMES complexes are long-lived, and do not depend on the presence of Gem1. Our findings suggest that the ERMES complex may have primarily a structural role in maintaining mitochondrial...

  9. Delphinidin-3-glucoside protects against oxidized low-density lipoprotein-induced mitochondrial dysfunction in vascular endothelial cells via the sodium-dependent glucose transporter SGLT1.

    Directory of Open Access Journals (Sweden)

    Xin Jin

    Full Text Available Delphinidin-3-glucoside (Dp is a member of a family of bioactive compounds known as anthocyanins that occur naturally in pigmented plants and are known to ameliorate oxidative stress. Previous studies have showed that Dp decreased oxidative stress in vascular endothelial cells, however, the underlying mechanisms remain largely unknown. In the present study, we showed that pretreatment with Dp significantly suppressed oxidized low-density lipoprotein (oxLDL-induced cell proliferation inhibition and apoptosis in primary human umbilical vein endothelial cells (HUVECs. Also, Dp pretreatment attenuated oxLDL-induced mitochondrial dysfunction via decreased reactive oxygen species (ROS and superoxide anion generation, thereby repressing mitochondrial membrane potential and closing mitochondrial permeability transition pore. Furthermore, in vitro and in vivo data showed that Dp was transported into endothelial cells in a temperature, concentration, and time-dependent manner via the sodium-dependent glucose transporter (SGLT1. Suppression of SGLT1 by its substrate glucose, its inhibitor phlorizin or SGLT1 siRNA blocked Dp transportation. Repression of SGLT1 significantly inhibited Dp function of ameliorating mitochondrial dysfunction induced by pro-apoptotic factors (Apoptosis-inducing factor, Cytochrome c, Caspase-3 and Bax/Bcl-2 ratio. Taken together, our data indicate that Dp protects VECs via the SGLT1-ROS-mitochodria pathway. This new insight may help to elucidate the molecular mechanisms underlying the vascular protection afforded by Dp, and anthocyanins in general, in the context of prevention of endothelial dysfunction and atherosclerosis.

  10. Partial mitochondrial complex I inhibition induces oxidative damage and perturbs glutamate transport in primary retinal cultures. Relevance to Leber Hereditary Optic Neuropathy (LHON).

    Science.gov (United States)

    Beretta, Simone; Wood, John P M; Derham, Barry; Sala, Gessica; Tremolizzo, Lucio; Ferrarese, Carlo; Osborne, Neville N

    2006-11-01

    Leber Hereditary Optic Neuropathy (LHON) is a maternally inherited form of visual loss, due to selective degeneration of retinal ganglion cells. Despite the established aetiological association between LHON and mitochondrial DNA mutations affecting complex I of the electron transport chain, the pathophysiology of this disorder remains obscure. Primary rat retinal cultures were exposed to increasing concentrations of rotenone to titrate complex I inhibition. Neural cells were more sensitive than Müller glial cells to rotenone toxicity. Rotenone induced an increase in mitochondrial-derived free radicals and lipid peroxidation. Sodium-dependent glutamate uptake, which is mostly mediated by the glutamate transporter GLAST expressed by Müller glial cells, was reduced dose-dependently by rotenone with no changes in GLAST expression. Our findings suggest that complex I-derived free radicals and disruption of glutamate transport might represent key elements for explaining the selective retinal ganglion cell death in LHON.

  11. Evaluation of the electron transport chain inhibition and uncoupling of mitochondrial bioelectrocatalysis with antibiotics and nitro-based compounds

    Energy Technology Data Exchange (ETDEWEB)

    Arechederra, Marguerite N.; Fischer, Caitlin N.; Wetzel, David J. [Department of Chemistry, Saint Louis University, 3501 Laclede Ave., St. Louis, MO (United States); Minteer, Shelley D., E-mail: minteers@slu.ed [Department of Chemistry, Saint Louis University, 3501 Laclede Ave., St. Louis, MO (United States)

    2010-12-30

    Mitochondrial bioelectrocatalysis can be useful for sensing applications due to the unique metabolic pathways than can be selectively inhibited and uncoupled in mitochondria. This paper details the comparison of different inhibitors and nitro-containing explosive uncouplers in a mitochondria-catalyzed biofuel cell for self-powered explosive sensing. Previous research has reported inhibition of pyruvate oxidation at a mitochondria-modified electrode followed by nitroaromatic uncoupling of current and power. We have previously used oligomycin as the antibiotic and nitrobenzene as the uncoupler of the membrane in the mitochondria-catalyzed biofuel cell, but no comprehensive comparison of various mitochondria inhibitors or explosives has been performed. Results are discussed here for inhibitors targeting complex I, complex III, ATP synthases, adenine nucleotide transport and monocarboxylic acid transport. Reactivation with nitrobenzene was possible in the presence of these inhibitors: oligomycin, 3,3'-diindolylmethane, atractyloside, rotenone, {alpha}-cyano-4-hydroxy cinnamic acid and antimycin A. All eleven explosives studied, including: 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), caused uncoupling of the mitochondria function and could be detected by the biosensor.

  12. CEP-1, the Caenorhabditis elegans p53 homolog, mediates opposing longevity outcomes in mitochondrial electron transport chain mutants.

    Directory of Open Access Journals (Sweden)

    Aiswarya Baruah

    2014-02-01

    Full Text Available Caenorhabditis elegans CEP-1 and its mammalian homolog p53 are critical for responding to diverse stress signals. In this study, we found that cep-1 inactivation suppressed the prolonged lifespan of electron transport chain (ETC mutants, such as isp-1 and nuo-6, but rescued the shortened lifespan of other ETC mutants, such as mev-1 and gas-1. We compared the CEP-1-regulated transcriptional profiles of the long-lived isp-1 and the short-lived mev-1 mutants and, to our surprise, found that CEP-1 regulated largely similar sets of target genes in the two mutants despite exerting opposing effects on their longevity. Further analyses identified a small subset of CEP-1-regulated genes that displayed distinct expression changes between the isp-1 and mev-1 mutants. Interestingly, this small group of differentially regulated genes are enriched for the "aging" Gene Ontology term, consistent with the hypothesis that they might be particularly important for mediating the distinct longevity effects of CEP-1 in isp-1 and mev-1 mutants. We further focused on one of these differentially regulated genes, ftn-1, which encodes ferritin in C. elegans, and demonstrated that it specifically contributed to the extended lifespan of isp-1 mutant worms but did not affect the mev-1 mutant lifespan. We propose that CEP-1 responds to different mitochondrial ETC stress by mounting distinct compensatory responses accordingly to modulate animal physiology and longevity. Our findings provide insights into how mammalian p53 might respond to distinct mitochondrial stressors to influence cellular and organismal responses.

  13. Chromophore-Assisted Light Inactivation of Mitochondrial Electron Transport Chain Complex II in Caenorhabditis elegans

    Science.gov (United States)

    Wojtovich, Andrew P.; Wei, Alicia Y.; Sherman, Teresa A.; Foster, Thomas H.; Nehrke, Keith

    2016-01-01

    Mitochondria play critical roles in meeting cellular energy demand, in cell death, and in reactive oxygen species (ROS) and stress signaling. Most Caenorhabditis elegans loss-of-function (lf) mutants in nuclear-encoded components of the respiratory chain are non-viable, emphasizing the importance of respiratory function. Chromophore-Assisted Light Inactivation (CALI) using genetically-encoded photosensitizers provides an opportunity to determine how individual respiratory chain components contribute to physiology following acute lf. As proof-of-concept, we expressed the ‘singlet oxygen generator’ miniSOG as a fusion with the SDHC subunit of respiratory complex II, encoded by mev-1 in C. elegans, using Mos1-mediated Single Copy Insertion. The resulting mev-1::miniSOG transgene complemented mev-1 mutant phenotypes in kn1 missense and tm1081(lf) deletion mutants. Complex II activity was inactivated by blue light in mitochondria from strains expressing active miniSOG fusions, but not those from inactive fusions. Moreover, light-inducible phenotypes in vivo demonstrated that complex II activity is important under conditions of high energy demand, and that specific cell types are uniquely susceptible to loss of complex II. In conclusion, miniSOG-mediated CALI is a novel genetic platform for acute inactivation of respiratory chain components. Spatio-temporally controlled ROS generation will expand our understanding of how the respiratory chain and mitochondrial ROS influence whole organism physiology. PMID:27440050

  14. Alterations in mitochondrial electron transport system activity in response to warm acclimation, hypoxia-reoxygenation and copper in rainbow trout, Oncorhynchus mykiss

    Energy Technology Data Exchange (ETDEWEB)

    Sappal, Ravinder [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3 (Canada); Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3 (Canada); MacDougald, Michelle [Faculty of Medicine, Memorial University of Newfoundland, Health Sciences Centre, Prince Philip Drive, St. John’s, NL, A1B 3V6 (Canada); Fast, Mark [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3 (Canada); Stevens, Don [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3 (Canada); Kibenge, Fred [Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3 (Canada); Siah, Ahmed [British Columbia Centre for Aquatic Health Sciences, 871A Island Highway, Campbell River, BC, V9W 2C2 (Canada); Kamunde, Collins, E-mail: ckamunde@upei.ca [Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3 (Canada)

    2015-08-15

    Highlights: • Sequential inhibition and activation allows assessment of multiple segments of the electron transport system. • Warm acclimation and hypoxia-reoxygenation have global effects on the electron transport system. • Warm acclimation and hypoxia-reoxygenation sensitize the electron transport system to copper. • Thermal stress, hypoxia-reoxygenation and copper act additively to impair mitochondrial function. - Abstract: Fish expend significant amounts of energy to handle the numerous potentially stressful biotic and abiotic factors that they commonly encounter in aquatic environments. This universal requirement for energy singularizes mitochondria, the primary cellular energy transformers, as fundamental drivers of responses to environmental change. Our study probed the interacting effects of thermal stress, hypoxia-reoxygenation (HRO) and copper (Cu) exposure in rainbow trout to test the prediction that they act jointly to impair mitochondrial function. Rainbow trout were acclimated to 11 (controls) or 20 °C for 2 months. Liver mitochondria were then isolated and their responses in vitro to Cu (0–20 μM) without and with HRO were assessed. Sequential inhibition and activation of mitochondrial electron transport system (ETS) enzyme complexes permitted the measurement of respiratory activities supported by complex I–IV (CI–IV) in one run. The results showed that warm acclimation reduced fish and liver weights but increased mitochondrial protein indicating impairment of energy metabolism, increased synthesis of defense proteins and/or reduced liver water content. Whereas acute rise (11 → 20 °C) in temperature increased mitochondrial oxidation rates supported by CI–IV, warm acclimation reduced the maximal (state 3) and increased the basal (state 4) respiration leading to global uncoupling of oxidative phosphorylation (OXPHOS). HRO profoundly inhibited both maximal and basal respiration rates supported by CI–IV, reduced RCR for all except

  15. MDMA impairs mitochondrial neuronal trafficking in a Tau- and Mitofusin2/Drp1-dependent manner.

    Science.gov (United States)

    Barbosa, Daniel José; Serrat, Román; Mirra, Serena; Quevedo, Martí; Gómez de Barreda, Elena; Avila, Jesús; Fernandes, Eduarda; Bastos, Maria de Lourdes; Capela, João Paulo; Carvalho, Félix; Soriano, Eduardo

    2014-08-01

    Identification of the mechanisms by which drugs of abuse cause neuronal dysfunction is essential for understanding the biological bases of their acute and long-lasting effects in the brain. Here, we performed real-time functional experiments of axonal transport of mitochondria to explore the role of in situ mitochondrial dysfunction in 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy")-related brain actions. We showed that MDMA dramatically reduced mitochondrial trafficking in hippocampal neurons in a Tau-dependent manner, in which glycogen synthase kinase 3β activity was implicated. Furthermore, we found that these trafficking abnormalities were rescued by over-expression of Mitofusin2 and dynamin-related protein 1, but not of Miro1. Given the relevance of mitochondrial targeting for neuronal function and neurotransmission, our data underscore a novel mechanism of action of MDMA that may contribute to our understanding of how this drug of abuse alters neuronal functioning.

  16. Changes in microtubule stability and density in myelin-deficient shiverer mouse CNS axons

    Science.gov (United States)

    Kirkpatrick, L. L.; Witt, A. S.; Payne, H. R.; Shine, H. D.; Brady, S. T.

    2001-01-01

    Altered axon-Schwann cell interactions in PNS myelin-deficient Trembler mice result in changed axonal transport rates, neurofilament and microtubule-associated protein phosphorylation, neurofilament density, and microtubule stability. To determine whether PNS and CNS myelination have equivalent effects on axons, neurofilaments, and microtubules in CNS, myelin-deficient shiverer axons were examined. The genetic defect in shiverer is a deletion in the myelin basic protein (MBP) gene, an essential component of CNS myelin. As a result, shiverer mice have little or no compact CNS myelin. Slow axonal transport rates in shiverer CNS axons were significantly increased, in contrast to the slowing in demyelinated PNS nerves. Even more striking were substantial changes in the composition and properties of microtubules in shiverer CNS axons. The density of axonal microtubules is increased, reflecting increased expression of tubulin in shiverer, and the stability of microtubules is drastically reduced in shiverer axons. Shiverer transgenic mice with two copies of a wild-type myelin basic protein transgene have an intermediate level of compact myelin, making it possible to determine whether the actual level of compact myelin is an important regulator of axonal microtubules. Both increased microtubule density and reduced microtubule stability were still observed in transgenic mouse nerves, indicating that signals beyond synaptogenesis and the mere presence of compact myelin are required for normal regulation of the axonal microtubule cytoskeleton.

  17. Antiretroviral Therapy-Associated Acute Motor and Sensory Axonal Neuropathy

    Directory of Open Access Journals (Sweden)

    Kimberly N. Capers

    2011-01-01

    Full Text Available Guillain-Barré syndrome (GBS has been reported in HIV-infected patients in association with the immune reconstitution syndrome whose symptoms can be mimicked by highly active antiretroviral therapy (HAART-mediated mitochondrial toxicity. We report a case of a 17-year-old, HIV-infected patient on HAART with a normal CD4 count and undetectable viral load, presenting with acute lower extremity weakness associated with lactatemia. Electromyography/nerve conduction studies revealed absent sensory potentials and decreased compound muscle action potentials, consistent with a diagnosis of acute motor and sensory axonal neuropathy. Lactatemia resolved following cessation of HAART; however, neurological deficits minimally improved over several months in spite of immune modulatory therapy. This case highlights the potential association between HAART, mitochondrial toxicity and acute axonal neuropathies in HIV-infected patients, distinct from the immune reconstitution syndrome.

  18. An epidemiologic study of mitochondrial membrane transporter protein gene polymorphism and risk factors for neural tube defects in Shanxi, China

    Institute of Scientific and Technical Information of China (English)

    Zhizhen Liu; Jun Xie; Tiane Luo; Tao Zhang; Xia Zhao; Hong Zhao; Peizhen Li

    2012-01-01

    The present study involved a questionnaire survey of 156 mothers that gave birth to children with neural tube defects or had a history of pregnancy resulting in children with neural tube defects (case group) and 156 control mothers with concurrent healthy children (control group) as well as detection of mitochondrial membrane transporter protein gene [uncoupling protein 2 (UCP2)] polymorphism. The maternal UCP2 3' untranslated region (UTR) D/D genotype and D allele frequency were significantly higher in the case group compared with the control group (odds ratio (OR) 3.233; 95% confidence interval (CI) 1.103-9.476; P = 0.040; OR: 3.484; 95% CI: for neural tube defects 2.109-5.753; P < 0.001). Univariate and multivariate logistic regression analysis of risk factors for neural tube defects showed that a maternal UCP2 3' UTR D/D genotype was negatively interacted with the mothers'consumption of frequent fresh fruit and vegetables (S = 0.007), positively interacted with the mothers'frequency of germinated potato consumption (S = 2.15) and positively interacted with the mothers' body mass index (S = 3.50). These findings suggest that maternal UCP2 3' UTR gene polymorphism, pregnancy time, consumption of germinated potatoes and body mass index are associated with an increased risk for neural tube defects in children from mothers living in Shanxi province, China. Moreover, there is an apparent gene-environment interaction involved in the development of neural tube defects in offspring.

  19. [F-18]Fluorodihydrorotenone: Synthesis and evaluation of a mitochondrial electron transport chain (ETC) complex I probe for PET

    Energy Technology Data Exchange (ETDEWEB)

    VanBrocklin, H.F.; Enas, J.D.; Hanrahan, S.M. [Lawrence Berkeley Lab., CA (United States)] [and others

    1994-05-01

    The mitochondrial electron transport chain (ETC) consists of five enzyme complexes (I-V) which participate in the transfer of electrons to oxygen and phosphorylation of ADP (oxidative phosphorylation). ETC dysfunction has been linked to several genetic neurological diseases as well as implicated in Parkinson`s (complex I) and Huntington`s (complex I) disease and normal aging processes. Dihydrorotenone (DHR) is a specific high affinity inhibitor of complex I. In order to develop a PET tracer for complex I, we have labeled DHR with fluorine-18. The tosylate precursor was produced in three steps from commercially available rotenone. Fluorine-18 was introduced by nucleophilic displacement of the tosylate using tetrabutyl-ammonium fluoride. Subsequent oxidation with MnO{sub 2} and HPLC purification gave the desired [{sup 18}F]fluoro-DHR. Initial biodistribution studies were carried out in {approximately}200 g male Sprague-Dawley rats. The tracer was taken up rapidly in the heart, an organ highly enriched with mitochondria, (5.5-6% injected dose (ID)/g at 30 minutes) and in the brain ({approximately}1.5% ID/g at 1 hour).

  20. The involvement of mitochondrial phosphate transporter in accelerating bud dormancy release during chilling treatment of tree peony (Paeonia suffruticosa).

    Science.gov (United States)

    Huang, Xin; Zhu, Wei; Dai, Silan; Gai, Shupeng; Zheng, Guosheng; Zheng, Chengchao

    2008-09-01

    A cDNA clone was isolated from tree peony (Paeonia suffruticosa) subtractive cDNA library of burst buds and characterized with regard to its sequence, expression in response to chilling treatment during the release of bud dormancy, and its function in transgenic Arabidopsis thaliana. The clone, designated as PsMPT, contains 1,615 nucleotides with an open reading frame of 1,119 nucleotides, and the deduced amino acid sequence shows high homology with mitochondrial phosphate transporters (MPTs) from various organisms. The mRNA accumulation of PsMPT in tree peony was strongly induced by chilling treatment during the release of bud dormancy. When the treated plants were transferred to normal growth conditions, the level of PsMPT transcripts induced by sufficient chilling could be maintained high, whereas that induced by insufficient chilling decreased sharply. The transgenic Arabidopsis plants that overexpress PsMPT showed rapid growth and earlier flowering than wild-type plants. ATP contents in the transgenic plants were much higher than that in wild-type plants through various developmental stages. Together, these results suggest that the product of PsMPT is a MPT and might play an important role during the release of bud dormancy in tree peony.

  1. Motor neuron synapse and axon defects in a C. elegans alpha-tubulin mutant.

    Directory of Open Access Journals (Sweden)

    Renee Baran

    Full Text Available Regulation of microtubule dynamics underlies many fundamental cellular mechanisms including cell division, cell motility, and transport. In neurons, microtubules play key roles in cell migration, axon outgrowth, control of axon and synapse growth, and the regulated transport of vesicles and structural components of synapses. Loss of synapse and axon integrity and disruption of axon transport characterize many neurodegenerative diseases. Recently, mutations that specifically alter the assembly or stability of microtubules have been found to directly cause neurodevelopmental defects or neurodegeneration in vertebrates. We report here the characterization of a missense mutation in the C-terminal domain of C. elegans alpha-tubulin, tba-1(ju89, that disrupts motor neuron synapse and axon development. Mutant ju89 animals exhibit reduction in the number and size of neuromuscular synapses, altered locomotion, and defects in axon extension. Although null mutations of tba-1 show a nearly wild-type pattern, similar axon outgrowth defects were observed in animals lacking the beta-tubulin TBB-2. Genetic analysis reveals that tba-1(ju89 affects synapse development independent of its role in axon outgrowth. tba-1(ju89 is an altered function allele that most likely perturbs interactions between TBA-1 and specific microtubule-associated proteins that control microtubule dynamics and transport of components needed for synapse and axon growth.

  2. Genetic dysfunction of MT-ATP6 causes axonal Charcot-Marie-Tooth disease.

    LENUS (Irish Health Repository)

    Pitceathly, Robert D S

    2012-09-11

    Charcot-Marie-Tooth (CMT) disease is the most common inherited neuromuscular disorder, affecting 1 in 2,500 individuals. Mitochondrial DNA (mtDNA) mutations are not generally considered within the differential diagnosis of patients with uncomplicated inherited neuropathy, despite the essential requirement of ATP for axonal function. We identified the mtDNA mutation m.9185T>C in MT-ATP6, encoding the ATP6 subunit of the mitochondrial ATP synthase (OXPHOS complex V), at homoplasmic levels in a family with mitochondrial disease in whom a severe motor axonal neuropathy was a striking feature. This led us to hypothesize that mutations in the 2 mtDNA complex V subunit encoding genes, MT-ATP6 and MT-ATP8, might be an unrecognized cause of isolated axonal CMT and distal hereditary motor neuropathy (dHMN).

  3. Re-evaluation of the H+/site ratio of mitochondrial electron transport with the oxygen pulse technique.

    Science.gov (United States)

    Brand, M D; Reynafarje, B; Lehninger, A L

    1976-09-25

    The number of protons ejected per pair of electrons passing each energy-conserving site in the electron transport chain (the H+/site ratio) has been investigated in rat liver mitochondria by means of the oxygen pulse technique introduced by Mitchell and Moyle (1967) (Biochem. J. 105, 1147-1162). The usual H+/site values of 2.0 observed by this method were found to be substantially underestimated as a result of the influx of phosphate into the mitochondria. This was shown by three different kinds of experiments. 1. Addition of N-ethylmaleimide or mersalyl, inhibitors of mitochondrial phosphate transport, increased the H+/site ratio from 2.0 to 3.0. The dependence of this effect on the concentration of either inhibitor was identical with that for inhibition of phosphate transport. Added phosphate diminished the H+/site ratio to values below 2.0 in the absence of N-ethylmaleimide. N-Ethylmaleimide protected the elevated H+/site ratio of 3.0 against the deleterious effect of added phosphate, but did not prevent a lowering effect of weak acid anions such as 3-hydroxybutyrate. 2. Prior washing of mitochondria to remove the endogenous phosphate that leaks out during the anaerobic preincubation led to H+/site ratios near 3.0, which were not increased by N-ethylmaleimide. Addition of low concentrations of phosphate to such phosphate-depleted mitochondria decreased the H+/site ratio to 2.0; addition of N-ethylmaleimide returned the ratio to 3.0. 3. Lowering the temperature to 5 degrees, which slows down phosphate transport, led to H+/site values of 3.0 even in the absence of N-ethylmaleimide. The H+/site ratio of 3.0 observed in the absence of phosphate movements was not dependent on any narrowly limited set of experimental conditions. It occurred with either Ca2+ or K+ (in the presence of valinomycin) as mobile permeant cation. It was independent of the concentration of succinate, oxygen, mitochondria, or rotenone, additions of Ca2+, Li+, or Na+ and was independent of

  4. Bypasses of the antimycin a block of mitochondrial electron transport in relation to ubisemiquinone function.

    Science.gov (United States)

    Alexandre, A; Lehninger, A L

    1984-10-26

    Two different bypasses around the antimycin block of electron transport from succinate to cytochrome c via the ubiquinol-cytochrome c oxidoreductase of intact rat liver mitochondria were analyzed, one promoted by N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and the other by 2,6-dichlorophenolindophenol (DCIP). Both bypasses are inhibited by myxothiazol, which blocks electron flow from ubiquinol to the Rieske iron-sulfur center, and by 2-hydroxy-3-undecyl-1,4-naphthoquinone, which inhibits electron flow from the iron-sulfur center to cytochrome c1. In the bypass promoted by TMPD its oxidized form (Wurster's blue) acts as an electron acceptor from some reduced component prior to the antimycin block, which by exclusion of other possibilities is ubisemiquinone. In the DCIP bypass its reduced form acts as an electron donor, by reducing ubisemiquinone to ubiquinol; reduced DCIP is regenerated again at the expense of either succinate or ascorbate. The observations described are consistent with and support current models of the Q cycle. Bypasses promoted by artificial electron carriers provide an independent approach to analysis of electron flow through ubiquinol-cytochrome c oxidoreductase.

  5. The K+/site and H+/site stoichiometry of mitochondrial electron transport.

    Science.gov (United States)

    Reynafarje, B; Lehninger, A L

    1978-09-25

    Electrode measurements of the average number of H+ ejected and K+ taken up (in the presence of valinomycin) per pair of electrons passing the energy-conserving sites of the respiratory chain of rat liver and rat heart mitochondria have given identical values of the H+/site and 5+/site ratios very close to 4 in the presence of N-ethylmaleimide, an inhibitor of interfering respiration-coupled uptake of H+ + H2PO4-. The K+/site uptake ratio of 4 not only shows that inward movement of K+ provides quantitative charge-compensation for the 4 H+ ejected, but also confirms that 4 charges are separated per pair of electrons per site. When N-ethylmaleimide is omitted, the H+/site ejection ratio is depressed, because of the interfering secondary uptake of H/+ with H2PO4- on the phosphate carrier, but the K+/site uptake ratio remains at 4.0. Addition of phosphate or acetate, which can carry H+ into respiring mitochondria, further depresses the H+/site ratio, but does not affect the K+/site ratio, which remains at 4.0. These and other considerations thus confirm our earlier stoichiometric measurements that the average H+/site ratio is 4.0 and also show that the K+/site uptake ratio can be used as a measure of the intrinsic H+/site ratio, regardless of the presence of phosphate in the medium and without the necessity of adding N-ethylmaleimide or other inhibitors of H+ + H2PO4- transport.

  6. ATP7A (Menkes Protein) functions in Axonal Targeting and Synaptogenesis

    OpenAIRE

    Meskini, Rajaâ El; Crabtree, Kelli L.; Cline, Laura B.; Mains, Richard E.; Eipper, Betty A.; Ronnett, Gabriele V.

    2007-01-01

    Menkes Disease (MD) is a neurodegenerative disorder caused by mutations in the copper transporter, ATP7A, a P-type ATPase. We previously used the olfactory system to demonstrate that ATP7A expression is developmentally, not constitutive, regulated, peaking during synaptogenesis when it is highly expressed in extending axons in a copper-independent manner. Although not known to be associated with axonal functions, we explored the possibility that the inability of mutant ATP7A to support axon o...

  7. On the location of the H+-extruding steps in site 2 of the mitochondrial electron transport chain.

    Science.gov (United States)

    Alexandre, A; Galiazzo, F; Lehninger, A L

    1980-11-25

    The location of the H+-translocating reactions within energy-conserving Site 2 of the mitochondrial electron transport chain was evaluated from two sets of data. In the first, the H+/2e- ejection ratios and Ca2+/2e- uptake ratios were compared for electron flow from succinate dehydrogenase, whose active site is on the matrix side of the inner membrane and from glycerol phosphate dehydrogenase, whose active site is on the cytosolic side. In intact rat liver mitochondria both substrates yielded H+/2e- ejection ratios close to 4.0 and Ca2+/2e- uptake ratios close to 1.0 during antimycin-sensitive reduction of ferricyanide. With rat liver mitoplasts and ferricytochrome c as electron acceptor, both substrates again gave the same stoichiometric ratios. The second approach involved determination of the sidedness of H+ formation during electron flow from succinate to ferricyanide via bypass of the antimycin block of the cytochrome b.c1 complex provided by N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), under conditions in which the TMPD-TMPD+ couple does not act as a membrane-penetrating protonophore. Electron flow in this system was inhibited by 2-then-oyltrifluoroacetone, indicating that TMPD probably accepts electrons from ubiquinol. The 2 H+ formed in this system were not delivered into the matrix but appeared directly in the medium in the absence of a protonophore. To accommodate the available evidence on Site 2 substrates, it is concluded that the substrate hydrogens are first transferred to ubiquinone, 2 H+ per 2e then appear in the medium by protolytic dehydrogenation of a species of ubiquinol or ubiquinol-protein having the appropriate sidedness (designated Site 2A), and the other 2 H+ are translocated from the matrix to the medium on passage of 2e- through the cytochrome b x c1 complex (designated Site 2B).

  8. Axon-glia interaction and membrane traffic in myelin formation.

    Science.gov (United States)

    White, Robin; Krämer-Albers, Eva-Maria

    2014-01-06

    In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialized glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarization followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is established. Continuous communication between neurons and glial cells is essential for myelin maintenance and axonal integrity. A diverse group of diseases, from multiple sclerosis to schizophrenia, have been linked to malfunction of myelinating cells reflecting the physiological importance of the axon-glial unit. This review describes the mechanisms of axonal signal integration by oligodendrocytes emphasizing the central role of the Src-family kinase Fyn during central nervous system (CNS) myelination. Furthermore, we discuss myelin membrane trafficking with particular focus on endocytic recycling and the control of proteolipid protein (PLP) transport by soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. Finally, PLP mistrafficking is considered in the context of myelin diseases.

  9. Axon-glia interaction and membrane traffic in myelin formation

    Directory of Open Access Journals (Sweden)

    Robin eWhite

    2014-01-01

    Full Text Available In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialised glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarisation followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is established. Continuous communication between neurons and glial cells is essential for myelin maintenance and axonal integrity. A diverse group of diseases, from multiple sclerosis to schizophrenia, have been linked to malfunction of myelinating cells reflecting the physiological importance of the axon-glial unit. This review describes the mechanisms of axonal signal integration by oligodendrocytes emphasising the central role of the Src-family kinase Fyn during CNS myelination. Furthermore, we discuss myelin membrane trafficking with particular focus on endocytic recycling and the control of PLP (proteolipid protein transport by SNARE proteins. Finally, PLP mistrafficking is considered in the context of myelin diseases.

  10. Abnormal morphology of myelin and axon pathology in murine models of multiple sclerosis.

    Science.gov (United States)

    Bando, Yoshio; Nomura, Taichi; Bochimoto, Hiroki; Murakami, Koichi; Tanaka, Tatsuhide; Watanabe, Tsuyoshi; Yoshida, Shigetaka

    2015-02-01

    Demyelination and axonal damage are responsible for neurological deficits in multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system. However, the pathology of axonal damage in MS is not fully understood. In this study, histological analysis of morphological changes of axonal organelles during demyelination in murine models was investigated by scanning electron microscopy (SEM) using an osmium-maceration method. In cuprizone-induced demyelination, SEM showed typical morphology of demyelination in the corpus callosum of mouse brain. In contrast, SEM displayed variations in ultrastructural abnormalities of myelin structures and axonal organelles in spinal cord white matter of experimental autoimmune encephalomyelitis (EAE) mice, an animal model of MS. Myelin detachment and excessive myelin formation were observed as typical morphological myelin abnormalities in EAE. In addition, well-developed axoplasmic reticulum-like structures and accumulated mitochondria were observed in tortuous degenerating/degenerated axons and the length of mitochondria in axons of EAE spinal cord was shorter compared with naïve spinal cord. Immunohistochemistry also revealed dysfunction of mitochondrial fusion/fission machinery in EAE spinal cord axons. Moreover, the number of Y-shaped mitochondria was significantly increased in axons of the EAE spinal cord. Axonal morphologies in myelin basic protein-deficient shiverer mice were similar to those in EAE. However, shiverer mice had "tortuous" (S-curve shaped mitochondria) and larger mitochondria compared with wild-type and EAE mice. Lastly, analysis of human MS patient autopsied brains also demonstrated abnormal myelin structures in demyelinating lesions. These results indicate that morphological abnormalities of myelin and axonal organelles play important role on the pathogenesis of axonal injury in demyelinating diseases.

  11. Abnormal mitochondrial dynamics, mitochondrial loss and mutant huntingtin oligomers in Huntington's disease: implications for selective neuronal damage.

    Science.gov (United States)

    Shirendeb, Ulziibat; Reddy, Arubala P; Manczak, Maria; Calkins, Marcus J; Mao, Peizhong; Tagle, Danilo A; Reddy, P Hemachandra

    2011-04-01

    oligomers in the nucleus of HD neurons and in mitochondria may disrupt neuronal functions. Based on these findings, we propose that mutant Htt in association with mitochondria imbalance and mitochondrial dynamics impairs axonal transport of mitochondria, decreases mitochondrial function and damages neurons in affected brain regions of HD patients.

  12. Intra-axonal protein synthesis - a new target for neural repair?

    Directory of Open Access Journals (Sweden)

    Jeffery L Twiss

    2016-01-01

    Full Text Available Although initially argued to be a feature of immature neurons with incomplete polarization, there is clear evidence that neurons in the peripheral nervous system retain the capacity for intra-axonal protein synthesis well into adulthood. This localized protein synthesis has been shown to contribute to injury signaling and axon regeneration in peripheral nerves. Recent works point to potential for protein synthesis in axons of the vertebrate central nervous system. mRNAs and protein synthesis machinery have now been documented in lamprey, mouse, and rat spinal cord axons. Intra-axonal protein synthesis appears to be activated in adult vertebrate spinal cord axons when they are regeneration-competent. Rat spinal cord axons regenerating into a peripheral nerve graft contain mRNAs and markers of activated translational machinery. Indeed, levels of some growth-associated mRNAs in these spinal cord axons are comparable to the regenerating sciatic nerve. Markers of active translation tend to decrease when these axons stop growing, but can be reactivated by a second axotomy. These emerging observations raise the possibility that mRNA transport into and translation within axons could be targeted to facilitate regeneration in both the peripheral and central nervous systems.

  13. Intra-axonal protein synthesis - a new target for neural repair?

    Science.gov (United States)

    Twiss, Jeffery L; Kalinski, Ashley L; Sachdeva, Rahul; Houle, John D

    2016-09-01

    Although initially argued to be a feature of immature neurons with incomplete polarization, there is clear evidence that neurons in the peripheral nervous system retain the capacity for intra-axonal protein synthesis well into adulthood. This localized protein synthesis has been shown to contribute to injury signaling and axon regeneration in peripheral nerves. Recent works point to potential for protein synthesis in axons of the vertebrate central nervous system. mRNAs and protein synthesis machinery have now been documented in lamprey, mouse, and rat spinal cord axons. Intra-axonal protein synthesis appears to be activated in adult vertebrate spinal cord axons when they are regeneration-competent. Rat spinal cord axons regenerating into a peripheral nerve graft contain mRNAs and markers of activated translational machinery. Indeed, levels of some growth-associated mRNAs in these spinal cord axons are comparable to the regenerating sciatic nerve. Markers of active translation tend to decrease when these axons stop growing, but can be reactivated by a second axotomy. These emerging observations raise the possibility that mRNA transport into and translation within axons could be targeted to facilitate regeneration in both the peripheral and central nervous systems.

  14. Intra-axonal protein synthesis - a new target for neural repair?

    Institute of Scientific and Technical Information of China (English)

    Jeffery L Twiss; Ashley L Kalinski; Rahul Sachdeva; John D Houle

    2016-01-01

    Although initially argued to be a feature of immature neurons with incomplete polarization, there is clear evidence that neurons in the peripheral nervous system retain the capacity for intra-axonal protein synthe-sis well into adulthood. This localized protein synthesis has been shown to contribute to injury signaling and axon regeneration in peripheral nerves. Recent works point to potential for protein synthesis in axons of the vertebrate central nervous system. mRNAs and protein synthesis machinery have now been docu-mented in lamprey, mouse, and rat spinal cord axons. Intra-axonal protein synthesis appears to be activated in adult vertebrate spinal cord axons when they are regeneration-competent. Rat spinal cord axons regen-erating into a peripheral nerve graft contain mRNAs and markers of activated translational machinery. Indeed, levels of some growth-associated mRNAs in these spinal cord axons are comparable to the regen-erating sciatic nerve. Markers of active translation tend to decrease when these axons stop growing, but can be reactivated by a second axotomy. These emerging observations raise the possibility that mRNA transport into and translation within axons could be targeted to facilitate regeneration in both the peripheral and central nervous systems.

  15. Role of calpains in the injury-induced dysfunction and degeneration of the mammalian axon.

    Science.gov (United States)

    Ma, Marek

    2013-12-01

    Axonal injury and degeneration, whether primary or secondary, contribute to the morbidity and mortality seen in many acquired and inherited central nervous system (CNS) and peripheral nervous system (PNS) disorders, such as traumatic brain injury, spinal cord injury, cerebral ischemia, neurodegenerative diseases, and peripheral neuropathies. The calpain family of proteases has been mechanistically linked to the dysfunction and degeneration of axons. While the direct mechanisms by which transection, mechanical strain, ischemia, or complement activation trigger intra-axonal calpain activity are likely different, the downstream effects of unregulated calpain activity may be similar in seemingly disparate diseases. In this review, a brief examination of axonal structure is followed by a focused overview of the calpain family. Finally, the mechanisms by which calpains may disrupt the axonal cytoskeleton, transport, and specialized domains (axon initial segment, nodes, and terminals) are discussed.

  16. Iron deficiency induces changes in riboflavin secretion and the mitochondrial electron transport chain in hairy roots of Hyoscyamus albus.

    Science.gov (United States)

    Higa, Ataru; Mori, Yuko; Kitamura, Yoshie

    2010-07-15

    Hyoscyamus albus hairy roots secrete riboflavin under Fe-deficient conditions. To determine whether this secretion was linked to an enhancement of respiration, both riboflavin secretion and the reduction of 2,3,5-triphenyltetrazolium chloride (TTC), as a measure of respiration activity, were determined in hairy roots cultured under Fe-deficient and Fe-replete conditions, with or without aeration. Appreciable TTC-reducing activity was detected at the root tips, at the bases of lateral roots and in internal tissues, notably the vascular system. TTC-reducing activity increased under Fe deficiency and this increase occurred in concert with riboflavin secretion and was more apparent under aeration. Riboflavin secretion was not apparent under Fe-replete conditions. In order to examine which elements of the mitochondrial electron transport chain might be involved, the effects of the respiratory inhibitors, barbiturate, dicoumarol, malonic acid, antimycin, KCN and salicylhydroxamic acid (SHAM) were investigated. Under Fe-deficient conditions, malonic acid affected neither root growth, TTC-reducing activity nor riboflavin secretion, whereas barbiturate and SHAM inhibited only root growth and TTC-reducing activity, respectively, and the other compounds variously inhibited growth and TTC-reducing activity. Riboflavin secretion was decreased, in concert with TTC-reducing activity, by dicoumarol, antimycin and KCN, but not by SHAM. In Fe-replete roots, all inhibitors which reduced riboflavin secretion in Fe-deficient roots showed somewhat different effects: notably, antimycin and KCN did not significantly inhibit TTC-reducing activity and the inhibition by dicoumarol was much weaker in Fe-replete roots. Combined treatment with KCN and SHAM also revealed that Fe-deficient and Fe-replete roots reduced TTC in different ways. A decrease in the Fe content of mitochondria in Fe-deficient roots was confirmed. Overall, the results suggest that, under conditions of Fe deficiency in H

  17. Impact of repeated stress on traumatic brain injury-induced mitochondrial electron transport chain expression and behavioral responses in rats

    Directory of Open Access Journals (Sweden)

    Guoqiang eXing

    2013-12-01

    Full Text Available A significant proportion of the military personnel returning from Iraq and Afghanistan conflicts have suffered from both mild traumatic brain injury (mTBI and post-traumatic stress disorder (PTSD. The mechanisms are unknown. We used a rat model of repeated stress and mTBI to examine brain activity and behavioral function. Adult male Sprague-Dawley rats were divided into 4 groups: Naïve; 3 days repeated tail-shock stress; lateral fluid percussion mTBI; and repeated stress followed by mTBI (S-mTBI. Open field activity, sensorimotor responses, and acoustic startle responses were measured after mTBI. The protein expression of mitochondrial electron transport chain (ETC complex subunits (CI-V and pyruvate dehydrogenase (PDHE1α1 were determined in 4 brain regions at day 7 post mTBI. Compared to Naïves, repeated stress decreased horizontal activity; repeated stress and mTBI both decreased vertical activity; and the mTBI and S-mTBI groups were impaired in sensorimotor and acoustic startle responses. Repeated stress significantly increased CI, CII, and CIII protein levels in the prefrontal cortex (PFC, but decreased PDHE1α1 protein in the PFC and cerebellum, and decreased CIV protein in the hippocampus. The mTBI treatment decreased CV protein levels in the ipsilateral hippocampus. The S-mTBI treatment resulted in increased CII, CIII, CIV, and CV protein levels in the PFC, increased CI level in the cerebellum, and increased CIII and CV levels in the cerebral cortex, but decreased CI, CII, CIV, and PDHE1α1 protein levels in the hippocampus. Thus, repeated stress or mTBI alone differentially altered ETC expression in heterogeneous brain regions. Repeated stress followed by mTBI had synergistic effects on brain ETC expression, and resulted in more severe behavioral deficits. These results suggest that repeated stress could have contributed to the high incidence of long-term neurologic and neuropsychiatric morbidity in military personnel with or without

  18. Oxidative stress in duckweed (Lemna minor L.) induced by glyphosate: Is the mitochondrial electron transport chain a target of this herbicide?

    Science.gov (United States)

    Gomes, Marcelo Pedrosa; Juneau, Philippe

    2016-11-01

    We investigated the physiological responses of Lemna minor plants exposed to glyphosate. The deleterious effects of this herbicide on photosynthesis, respiration, and pigment concentrations were related to glyphosate-induced oxidative stress through hydrogen peroxide (H2O2) accumulation. By using photosynthetic and respiratory electron transport chain (ETC) inhibitors we located the primary site of reactive oxygen species (ROS) production in plants exposed to 500 mg glyphosate l(-1). Inhibition of mitochondrial ETC Complex I by rotenone reduced H2O2 concentrations in glyphosate-treated plants. Complex III activity was very sensitive to glyphosate which appears to act much like antimycin A (an inhibitor of mitochondrial ETC Complex III) by shunting electrons from semiquinone to oxygen, with resulting ROS formation. Confocal evaluations for ROS localization showed that ROS are initially produced outside of the chloroplasts upon initial glyphosate exposure. Our results indicate that in addition to interfering with the shikimate pathway, glyphosate can induce oxidative stress in plants through H2O2 formation by targeting the mitochondrial ETC, which would explain its observed effects on non-target organisms.

  19. Developmental and hormone-induced changes of mitochondrial electron transport chain enzyme activities during the last instar larval development of maize stem borer, Chilo partellus (Lepidoptera: Crambidae).

    Science.gov (United States)

    VenkatRao, V; Chaitanya, R K; Naresh Kumar, D; Bramhaiah, M; Dutta-Gupta, A

    2016-12-01

    The energy demand for structural remodelling in holometabolous insects is met by cellular mitochondria. Developmental and hormone-induced changes in the mitochondrial respiratory activity during insect metamorphosis are not well documented. The present study investigates activities of enzymes of mitochondrial electron transport chain (ETC) namely, NADH:ubiquinone oxidoreductase or complex I, Succinate: ubiquinone oxidoreductase or complex II, Ubiquinol:ferricytochrome c oxidoreductase or complex III, cytochrome c oxidase or complex IV and F1F0ATPase (ATPase), during Chilo partellus development. Further, the effect of juvenile hormone (JH) analog, methoprene, and brain and corpora-allata-corpora-cardiaca (CC-CA) homogenates that represent neurohormones, on the ETC enzyme activities was monitored. The enzymatic activities increased from penultimate to last larval stage and thereafter declined during pupal development with an exception of ATPase which showed high enzyme activity during last larval and pupal stages compared to the penultimate stage. JH analog, methoprene differentially modulated ETC enzyme activities. It stimulated complex I and IV enzyme activities, but did not alter the activities of complex II, III and ATPase. On the other hand, brain homogenate declined the ATPase activity while the injected CC-CA homogenate stimulated complex I and IV enzyme activities. Cumulatively, the present study is the first to show that mitochondrial ETC enzyme system is under hormone control, particularly of JH and neurohormones during insect development.

  20. AIFM1 mutation presenting with fatal encephalomyopathy and mitochondrial disease in an infant

    Science.gov (United States)

    Morton, Sarah U.; Prabhu, Sanjay P.; Lidov, Hart G.W.; Shi, Jiahai; Anselm, Irina; Brownstein, Catherine A.; Bainbridge, Matthew N.; Beggs, Alan H.; Vargas, Sara O.; Agrawal, Pankaj B.

    2017-01-01

    Apoptosis-inducing factor mitochondrion-associated 1 (AIFM1), encoded by the gene AIFM1, has roles in electron transport, apoptosis, ferredoxin metabolism, reactive oxygen species generation, and immune system regulation. Here we describe a patient with a novel AIFM1 variant presenting unusually early in life with mitochondrial disease, rapid deterioration, and death. Autopsy, at the age of 4 mo, revealed features of mitochondrial encephalopathy, myopathy, and involvement of peripheral nerves with axonal degeneration. In addition, there was microvesicular steatosis in the liver, thymic noninvolution, follicular bronchiolitis, and pulmonary arterial medial hypertrophy. This report adds to the clinical and pathological spectrum of disease related to AIFM1 mutations and provides insights into the role of AIFM1 in cellular function. PMID:28299359

  1. Glutamate excitotoxicity and Ca2+-regulation of respiration: Role of the Ca2+ activated mitochondrial transporters (CaMCs).

    Science.gov (United States)

    Rueda, Carlos B; Llorente-Folch, Irene; Traba, Javier; Amigo, Ignacio; Gonzalez-Sanchez, Paloma; Contreras, Laura; Juaristi, Inés; Martinez-Valero, Paula; Pardo, Beatriz; Del Arco, Araceli; Satrustegui, Jorgina

    2016-08-01

    Glutamate elicits Ca(2+) signals and workloads that regulate neuronal fate both in physiological and pathological circumstances. Oxidative phosphorylation is required in order to respond to the metabolic challenge caused by glutamate. In response to physiological glutamate signals, cytosolic Ca(2+) activates respiration by stimulation of the NADH malate-aspartate shuttle through Ca(2+)-binding to the mitochondrial aspartate/glutamate carrier (Aralar/AGC1/Slc25a12), and by stimulation of adenine nucleotide uptake through Ca(2+) binding to the mitochondrial ATP-Mg/Pi carrier (SCaMC-3/Slc25a23). In addition, after Ca(2+) entry into the matrix through the mitochondrial Ca(2+) uniporter (MCU), it activates mitochondrial dehydrogenases. In response to pathological glutamate stimulation during excitotoxicity, Ca(2+) overload, reactive oxygen species (ROS), mitochondrial dysfunction and delayed Ca(2+) deregulation (DCD) lead to neuronal death. Glutamate-induced respiratory stimulation is rapidly inactivated through a mechanism involving Poly (ADP-ribose) Polymerase-1 (PARP-1) activation, consumption of cytosolic NAD(+), a decrease in matrix ATP and restricted substrate supply. Glutamate-induced Ca(2+)-activation of SCaMC-3 imports adenine nucleotides into mitochondria, counteracting the depletion of matrix ATP and the impaired respiration, while Aralar-dependent lactate metabolism prevents substrate exhaustion. A second mechanism induced by excitotoxic glutamate is permeability transition pore (PTP) opening, which critically depends on ROS production and matrix Ca(2+) entry through the MCU. By increasing matrix content of adenine nucleotides, SCaMC-3 activity protects against glutamate-induced PTP opening and lowers matrix free Ca(2+), resulting in protracted appearance of DCD and protection against excitotoxicity in vitro and in vivo, while the lack of lactate protection during in vivo excitotoxicity explains increased vulnerability to kainite-induced toxicity in Aralar

  2. The Microtubule Regulatory Protein Stathmin Is Required to Maintain the Integrity of Axonal Microtubules in Drosophila.

    Directory of Open Access Journals (Sweden)

    Jason E Duncan

    Full Text Available Axonal transport, a form of long-distance, bi-directional intracellular transport that occurs between the cell body and synaptic terminal, is critical in maintaining the function and viability of neurons. We have identified a requirement for the stathmin (stai gene in the maintenance of axonal microtubules and regulation of axonal transport in Drosophila. The stai gene encodes a cytosolic phosphoprotein that regulates microtubule dynamics by partitioning tubulin dimers between pools of soluble tubulin and polymerized microtubules, and by directly binding to microtubules and promoting depolymerization. Analysis of stai function in Drosophila, which has a single stai gene, circumvents potential complications with studies performed in vertebrate systems in which mutant phenotypes may be compensated by genetic redundancy of other members of the stai gene family. This has allowed us to identify an essential function for stai in the maintenance of the integrity of axonal microtubules. In addition to the severe disruption in the abundance and architecture of microtubules in the axons of stai mutant Drosophila, we also observe additional neurological phenotypes associated with loss of stai function including a posterior paralysis and tail-flip phenotype in third instar larvae, aberrant accumulation of transported membranous organelles in stai deficient axons, a progressive bang-sensitive response to mechanical stimulation reminiscent of the class of Drosophila mutants used to model human epileptic seizures, and a reduced adult lifespan. Reductions in the levels of Kinesin-1, the primary anterograde motor in axonal transport, enhance these phenotypes. Collectively, our results indicate that stai has an important role in neuronal function, likely through the maintenance of microtubule integrity in the axons of nerves of the peripheral nervous system necessary to support and sustain long-distance axonal transport.

  3. Thiazolidinediones Promote Axonal Growth through the Activation of the JNK Pathway

    Science.gov (United States)

    Quintanilla, Rodrigo A.; Godoy, Juan A.; Alfaro, Ivan; Cabezas, Deny; von Bernhardi, Rommy; Bronfman, Miguel; Inestrosa, Nibaldo C.

    2013-01-01

    The axon is a neuronal process involved in protein transport, synaptic plasticity, and neural regeneration. It has been suggested that their structure and function are profoundly impaired in neurodegenerative diseases. Previous evidence suggest that Peroxisome Proliferator-Activated Receptors-γ (PPARγ promote neuronal differentiation on various neuronal cell types. In addition, we demonstrated that activation of PPARγby thiazolidinediones (TZDs) drugs that selectively activate PPARγ prevent neurite loss and axonal damage induced by amyloid-β (Aβ). However, the potential role of TZDs in axonal elongation and neuronal polarity has not been explored. We report here that the activation of PPARγ by TZDs promoted axon elongation in primary hippocampal neurons. Treatments with different TZDs significantly increased axonal growth and branching area, but no significant effects were observed in neurite elongation compared to untreated neurons. Treatment with PPARγ antagonist (GW 9662) prevented TZDs-induced axonal growth. Recently, it has been suggested that the c-Jun N-terminal kinase (JNK) plays an important role regulating axonal growth and neuronal polarity. Interestingly, in our studies, treatment with TZDs induced activation of the JNK pathway, and the pharmacological blockage of this pathway prevented axon elongation induced by TZDs. Altogether, these results indicate that activation of JNK induced by PPARγactivators stimulates axonal growth and accelerates neuronal polarity. These novel findings may contribute to the understanding of the effects of PPARγ on neuronal differentiation and validate the use of PPARγ activators as therapeutic agents in neurodegenerative diseases. PMID:23741474

  4. Bicyclic-Capped Histone Deacetylase 6 Inhibitors with Improved Activity in a Model of Axonal Charcot-Marie-Tooth Disease.

    Science.gov (United States)

    Shen, Sida; Benoy, Veronick; Bergman, Joel A; Kalin, Jay H; Frojuello, Mariana; Vistoli, Giulio; Haeck, Wanda; Van Den Bosch, Ludo; Kozikowski, Alan P

    2016-02-17

    Charcot-Marie-Tooth (CMT) disease is a disorder of the peripheral nervous system where progressive degeneration of motor and sensory nerves leads to motor problems and sensory loss and for which no pharmacological treatment is available. Recently, it has been shown in a model for the axonal form of CMT that histone deacetylase 6 (HDAC6) can serve as a target for the development of a pharmacological therapy. Therefore, we aimed at developing new selective and activity-specific HDAC6 inhibitors with improved biochemical properties. By utilizing a bicyclic cap as the structural scaffold from which to build upon, we developed several analogues that showed improved potency compared to tubastatin A while maintaining excellent selectivity compared to HDAC1. Further screening in N2a cells examining both the acetylation of α-tubulin and histones narrowed down the library of compounds to three potent and selective HDAC6 inhibitors. In mutant HSPB1-expressing DRG neurons, serving as an in vitro model for CMT2, these inhibitors were able to restore the mitochondrial axonal transport deficits. Combining structure-based development of HDAC6 inhibitors, screening in N2a cells and in a neuronal model for CMT2F, and preliminary ADMET and pharmacokinetic profiles, resulted in the selection of compound 23d that possesses improved biochemical, functional, and druglike properties compared to tubastatin A.

  5. Transcellular degradation of axonal mitochondria.

    Science.gov (United States)

    Davis, Chung-ha O; Kim, Keun-Young; Bushong, Eric A; Mills, Elizabeth A; Boassa, Daniela; Shih, Tiffany; Kinebuchi, Mira; Phan, Sebastien; Zhou, Yi; Bihlmeyer, Nathan A; Nguyen, Judy V; Jin, Yunju; Ellisman, Mark H; Marsh-Armstrong, Nicholas

    2014-07-01

    It is generally accepted that healthy cells degrade their own mitochondria. Here, we report that retinal ganglion cell axons of WT mice shed mitochondria at the optic nerve head (ONH), and that these mitochondria are internalized and degraded by adjacent astrocytes. EM demonstrates that mitochondria are shed through formation of large protrusions that originate from otherwise healthy axons. A virally introduced tandem fluorophore protein reporter of acidified mitochondria reveals that acidified axonal mitochondria originating from the retinal ganglion cell are associated with lysosomes within columns of astrocytes in the ONH. According to this reporter, a greater proportion of retinal ganglion cell mitochondria are degraded at the ONH than in the ganglion cell soma. Consistently, analyses of degrading DNA reveal extensive mtDNA degradation within the optic nerve astrocytes, some of which comes from retinal ganglion cell axons. Together, these results demonstrate that surprisingly large proportions of retinal ganglion cell axonal mitochondria are normally degraded by the astrocytes of the ONH. This transcellular degradation of mitochondria, or transmitophagy, likely occurs elsewhere in the CNS, because structurally similar accumulations of degrading mitochondria are also found along neurites in superficial layers of the cerebral cortex. Thus, the general assumption that neurons or other cells necessarily degrade their own mitochondria should be reconsidered.

  6. Pyrroloquinoline Quinone Resists Denervation-Induced Skeletal Muscle Atrophy by Activating PGC-1α and Integrating Mitochondrial Electron Transport Chain Complexes.

    Directory of Open Access Journals (Sweden)

    Yung-Ting Kuo

    Full Text Available Denervation-mediated skeletal muscle atrophy results from the loss of electric stimulation and leads to protein degradation, which is critically regulated by the well-confirmed transcriptional co-activator peroxisome proliferator co-activator 1 alpha (PGC-1α. No adequate treatments of muscle wasting are available. Pyrroloquinoline quinone (PQQ, a naturally occurring antioxidant component with multiple functions including mitochondrial modulation, demonstrates the ability to protect against muscle dysfunction. However, it remains unclear whether PQQ enhances PGC-1α activation and resists skeletal muscle atrophy in mice subjected to a denervation operation. This work investigates the expression of PGC-1α and mitochondrial function in the skeletal muscle of denervated mice administered PQQ. The C57BL6/J mouse was subjected to a hindlimb sciatic axotomy. A PQQ-containing ALZET® osmotic pump (equivalent to 4.5 mg/day/kg b.w. was implanted subcutaneously into the right lower abdomen of the mouse. In the time course study, the mouse was sacrificed and the gastrocnemius muscle was prepared for further myopathological staining, energy metabolism analysis, western blotting, and real-time quantitative PCR studies. We observed that PQQ administration abolished the denervation-induced decrease in muscle mass and reduced mitochondrial activities, as evidenced by the reduced fiber size and the decreased expression of cytochrome c oxidase and NADH-tetrazolium reductase. Bioenergetic analysis demonstrated that PQQ reprogrammed the denervation-induced increase in the mitochondrial oxygen consumption rate (OCR and led to an increase in the extracellular acidification rate (ECAR, a measurement of the glycolytic metabolism. The protein levels of PGC-1α and the electron transport chain (ETC complexes were also increased by treatment with PQQ. Furthermore, PQQ administration highly enhanced the expression of oxidative fibers and maintained the type II glycolytic

  7. A Putative Mitochondrial Iron Transporter MrsA in Aspergillus fumigatus Plays Important Roles in Azole-, Oxidative Stress Responses and Virulence.

    Science.gov (United States)

    Long, Nanbiao; Xu, Xiaoling; Qian, Hui; Zhang, Shizhu; Lu, Ling

    2016-01-01

    Iron is an essential nutrient and enzyme co-factor required for a wide range of cellular processes, especially for the function of mitochondria. For the opportunistic fungal pathogen Aspergillus fumigatus, the ability to obtain iron is required for growth and virulence during the infection process. However, knowledge of how mitochondria are involved in iron regulation is still limited. Here, we show that a mitochondrial iron transporter, MrsA, a homolog of yeast Mrs4p, is critical for adaptation to iron-limited or iron-excess conditions in A. fumigatus. Deletion of mrsA leads to disruption of iron homeostasis with a decreased sreA expression, resulted in activated reductive iron assimilation (RIA) and siderophore-mediated iron acquisition (SIA). Furthermore, deletion of mrsA induces hypersusceptibility to azole and oxidative stresses. An assay for cellular ROS content in ΔmrsA combined with rescue from the mrsA-defective phenotype by the antioxidant reagent L-ascorbic acid indicates that the increased sensitivity of ΔmrsA to the azole itraconazole and to oxidative stress is mainly the result of abnormal ROS accumulation. Moreover, site-directed mutation experiments verified that three conserved histidine residues related to iron transport in MrsA are required for responses to oxidative and azole stresses. Importantly, ΔmrsA causes significant attenuation of virulence in an immunocompromised murine model of aspergillosis. Collectively, our results show that the putative mitochondrial iron transporter MrsA plays important roles in azole- and oxidative-stress responses and virulence by regulating the balance of cellular iron in A. fumigatus.

  8. A putative mitochondrial iron transporter MrsA in Aspergillus fumigatus plays important roles in azole-, oxidative stress responses and virulence

    Directory of Open Access Journals (Sweden)

    Nanbiao eLong

    2016-05-01

    Full Text Available Iron is an essential nutrient and enzyme co-factor required for a wide range of cellular processes, especially for the function of mitochondria. For the opportunistic fungal pathogen Aspergillus fumigatus, the ability to obtain iron is required for growth and virulence during the infection process. However, knowledge of how mitochondria are involved in iron regulation is still limited. Here, we show that a mitochondrial iron transporter, MrsA, a homolog of yeast Mrs4p, is critical for adaptation to iron-limited or iron-excess conditions in A. fumigatus. Deletion of mrsA leads to disruption of iron homeostasis with a decreased sreA expression, resulted in activated reductive iron assimilation (RIA and siderophore-mediated iron acquisition (SIA. Furthermore, deletion of mrsA induces hypersusceptibility to azole and oxidative stresses. An assay for cellular ROS content in ΔmrsA combined with rescue from the mrsA-defective phenotype by the antioxidant reagent L-ascorbic acid indicates that the increased sensitivity of ΔmrsA to the azole itraconazole and to oxidative stress is mainly the result of abnormal ROS accumulation. Moreover, site-directed mutation experiments verified that three conserved histidine residues related to iron transport in MrsA are required for responses to oxidative and azole stresses. Importantly, ΔmrsA causes significant attenuation of virulence in an immunocompromised murine model of aspergillosis. Collectively, our results show that the putative mitochondrial iron transporter MrsA plays important roles in azole- and oxidative-stress responses and virulence by regulating the balance of cellular iron in A. fumigatus.

  9. Computational modeling analysis of mitochondrial superoxide production under varying substrate conditions and upon inhibition of different segments of the electron transport chain.

    Science.gov (United States)

    Markevich, Nikolai I; Hoek, Jan B

    2015-01-01

    A computational mechanistic model of superoxide (O2•-) formation in the mitochondrial electron transport chain (ETC) was developed to facilitate the quantitative analysis of factors controlling mitochondrial O2•- production and assist in the interpretation of experimental studies. The model takes into account all individual electron transfer reactions in Complexes I and III. The model accounts for multiple, often seemingly contradictory observations on the effects of ΔΨ and ΔpH, and for the effects of multiple substrate and inhibitor conditions, including differential effects of Complex III inhibitors antimycin A, myxothiazol and stigmatellin. Simulation results confirm that, in addition to O2•- formation in Complex III and at the flavin site of Complex I, the quinone binding site of Complex I is an additional superoxide generating site that accounts for experimental observations on O2•- production during reverse electron transfer. However, our simulation results predict that, when cytochrome c oxidase is inhibited during oxidation of succinate, ROS production at this site is eliminated and almost all superoxide in Complex I is generated by reduced FMN, even when the redox pressure for reverse electron transfer from succinate is strong. In addition, the model indicates that conflicting literature data on the kinetics of electron transfer in Complex III involving the iron-sulfur protein-cytochrome bL complex can be resolved in favor of a dissociation of the protein only after electron transfer to cytochrome bH. The model predictions can be helpful in understanding factors driving mitochondrial superoxide formation in intact cells and tissues.

  10. Suppression of NDA-type alternative mitochondrial NAD(P)H dehydrogenases in arabidopsis thaliana modifies growth and metabolism, but not high light stimulation of mitochondrial electron transport.

    Science.gov (United States)

    Wallström, Sabá V; Florez-Sarasa, Igor; Araújo, Wagner L; Escobar, Matthew A; Geisler, Daniela A; Aidemark, Mari; Lager, Ida; Fernie, Alisdair R; Ribas-Carbó, Miquel; Rasmusson, Allan G

    2014-05-01

    The plant respiratory chain contains several pathways which bypass the energy-conserving electron transport complexes I, III and IV. These energy bypasses, including type II NAD(P)H dehydrogenases and the alternative oxidase (AOX), may have a role in redox stabilization and regulation, but current evidence is inconclusive. Using RNA interference, we generated Arabidopsis thaliana plants simultaneously suppressing the type II NAD(P)H dehydrogenase genes NDA1 and NDA2. Leaf mitochondria contained substantially reduced levels of both proteins. In sterile culture in the light, the transgenic lines displayed a slow growth phenotype, which was more severe when the complex I inhibitor rotenone was present. Slower growth was also observed in soil. In rosette leaves, a higher NAD(P)H/NAD(P)⁺ ratio and elevated levels of lactate relative to sugars and citric acid cycle metabolites were observed. However, photosynthetic performance was unaffected and microarray analyses indicated few transcriptional changes. A high light treatment increased AOX1a mRNA levels, in vivo AOX and cytochrome oxidase activities, and levels of citric acid cycle intermediates and hexoses in all genotypes. However, NDA-suppressing plants deviated from the wild type merely by having higher levels of several amino acids. These results suggest that NDA suppression restricts citric acid cycle reactions, inducing a shift towards increased levels of fermentation products, but do not support a direct association between photosynthesis and NDA proteins.

  11. Significance of transcytosis in Alzheimer's disease: BACE1 takes the scenic route to axons.

    Science.gov (United States)

    Buggia-Prévot, Virginie; Thinakaran, Gopal

    2015-08-01

    Neurons have developed elaborate mechanisms for sorting of proteins to their destination in dendrites and axons as well as dynamic local trafficking. Recent evidence suggests that polarized axonal sorting of β-site converting enzyme 1 (BACE1), a type I transmembrane aspartyl protease involved in Alzheimer's disease (AD) pathogenesis, entails an unusual journey. In hippocampal neurons, BACE1 internalized from dendrites is conveyed in recycling endosomes via unidirectional retrograde transport towards the soma and sorted to axons where BACE1 becomes enriched. In comparison to other transmembrane proteins that undergo transcytosis or elimination in somatodendritic compartment, vectorial transport of internalized BACE1 in dendrites is unique and intriguing. Dysfunction of protein transport contributes to pathogenesis of AD and other neurodegenerative diseases. Therefore, characterization of BACE1 transcytosis is an important addition to the multiple lines of evidence that highlight the crucial role played by endosomal trafficking pathway as well as axonal sorting mechanisms in AD pathogenesis.

  12. Action-potential modulation during axonal conduction.

    Science.gov (United States)

    Sasaki, Takuya; Matsuki, Norio; Ikegaya, Yuji

    2011-02-04

    Once initiated near the soma, an action potential (AP) is thought to propagate autoregeneratively and distribute uniformly over axonal arbors. We challenge this classic view by showing that APs are subject to waveform modulation while they travel down axons. Using fluorescent patch-clamp pipettes, we recorded APs from axon branches of hippocampal CA3 pyramidal neurons ex vivo. The waveforms of axonal APs increased in width in response to the local application of glutamate and an adenosine A(1) receptor antagonist to the axon shafts, but not to other unrelated axon branches. Uncaging of calcium in periaxonal astrocytes caused AP broadening through ionotropic glutamate receptor activation. The broadened APs triggered larger calcium elevations in presynaptic boutons and facilitated synaptic transmission to postsynaptic neurons. This local AP modification may enable axonal computation through the geometry of axon wiring.

  13. The Arabidopsis thaliana RNA Editing FactorSLO2, which Affects the Mitochondrial ElectronTransport Chain, Participates in Multiple Stressand Hormone Resoonses

    Institute of Scientific and Technical Information of China (English)

    2014-01-01

    Recently, we reported that the novel mitochondrial RNA editing factor SLO2 is essential for mitochondrialelectron transport, and vital for plant growth through regulation of carbon and energy metabolism. Here, we show thatmutation in SL02 causes hypersensitivity to ABA and insensitivity to ethylene, suggesting a link with stress responses.Indeed, slo2 mutants are hypersensitive to salt and osmotic stress during the germination stage, while adult plantsshow increased drought and salt tolerance. Moreover, slo2 mutants are more susceptible to Botrytis cinerea infection.An increased expression of nuclear-encoded stress-responsive genes, as well as mitochondrial-encoded NAD genes ofcomplex I and genes of the alternative respiratory pathway, was observed in slo2 mutants, further enhanced by ABAtreatment. In addition, H202 accumulation and altered amino acid levels were recorded in slo2 mutants. We conclude thatSLO2 is required for plant sensitivity to ABA, ethylene, biotic, and abiotic stress. Although two stress-related RNA editingfactors were reported very recently, this study demonstrates a unique role of SLO2, and further supports a link betweenmitochondrial RNA editing events and stress response.

  14. H2O2 generated from mitochondrial electron transport chain in thoracic perivascular adipose tissue is crucial for modulation of vascular smooth muscle contraction.

    Science.gov (United States)

    Costa, Rafael M; Filgueira, Fernando P; Tostes, Rita C; Carvalho, Maria Helena C; Akamine, Eliana H; Lobato, Nubia S

    2016-09-01

    The perivascular adipose tissue (PVAT) releases a variety of factors that affect vascular function. PVAT in the thoracic aorta shares characteristics with the brown adipose tissue, including a large amount of mitochondria. PVAT-derived factors influence both endothelial and smooth muscle function via several signaling mechanisms including the release/generation of reactive nitrogen and oxygen species. Considering the importance of reactive oxygen species (ROS) on vascular function and that mitochondria are an important source of ROS, we hypothesized that mitochondria-derived ROS in the PVAT modulates vascular reactivity. Vascular reactivity to norephinephrine (NE) was evaluated in thoracic aortic rings, with or without endothelium and/or PVAT, from male Wistar rats. Mitochondrial uncoupling, as well as hydrogen peroxide (H2O2) removal, increased the contraction in vessels surrounded by PVAT. PVAT stimulated with NE exhibited increased protein expression, determined by Western blot analysis, of manganese superoxide dismutase (Mn-SOD) and decreased protein expression of catalase. Ultimately, NE increased superoxide anion (O2(-)) generation in PVAT via increases in intracellular calcium. These results clearly demonstrate that mitochondrial electron transport chain (mETC) in PVAT contributes to modulation of aortic muscle contraction by generating higher amounts of O2(-) that is, in turn, dismutated to hydrogen peroxide, which then acts as a pivotal signaling molecule regulating vascular smooth muscle contraction.

  15. Mitochondrial phospholipids: role in mitochondrial function.

    Science.gov (United States)

    Mejia, Edgard M; Hatch, Grant M

    2016-04-01

    Mitochondria are essential components of eukaryotic cells and are involved in a diverse set of cellular processes that include ATP production, cellular signalling, apoptosis and cell growth. These organelles are thought to have originated from a symbiotic relationship between prokaryotic cells in an effort to provide a bioenergetic jump and thus, the greater complexity observed in eukaryotes (Lane and Martin 2010). Mitochondrial processes are required not only for the maintenance of cellular homeostasis, but also allow cell to cell and tissue to tissue communication (Nunnari and Suomalainen 2012). Mitochondrial phospholipids are important components of this system. Phospholipids make up the characteristic outer and inner membranes that give mitochondria their shape. In addition, these membranes house sterols, sphingolipids and a wide variety of proteins. It is the phospholipids that also give rise to other characteristic mitochondrial structures such as cristae (formed from the invaginations of the inner mitochondrial membrane), the matrix (area within cristae) and the intermembrane space (IMS) which separates the outer mitochondrial membrane (OMM) and inner mitochondrial membrane (IMM). Phospholipids are the building blocks that make up these structures. However, the phospholipid composition of the OMM and IMM is unique in each membrane. Mitochondria are able to synthesize some of the phospholipids it requires, but the majority of cellular lipid biosynthesis takes place in the endoplasmic reticulum (ER) in conjunction with the Golgi apparatus (Fagone and Jackowski 2009). In this review, we will focus on the role that mitochondrial phospholipids play in specific cellular functions and discuss their biosynthesis, metabolism and transport as well as the differences between the OMM and IMM phospholipid composition. Finally, we will focus on the human diseases that result from disturbances to mitochondrial phospholipids and the current research being performed to help

  16. The mixture of "ecstasy" and its metabolites impairs mitochondrial fusion/fission equilibrium and trafficking in hippocampal neurons, at in vivo relevant concentrations.

    Science.gov (United States)

    Barbosa, Daniel José; Serrat, Romàn; Mirra, Serena; Quevedo, Martí; de Barreda, Elena Goméz; Àvila, Jesús; Ferreira, Luísa Maria; Branco, Paula Sério; Fernandes, Eduarda; Lourdes Bastos, Maria de; Capela, João Paulo; Soriano, Eduardo; Carvalho, Félix

    2014-06-01

    3,4-Methylenedioxymethamphetamine (MDMA; "ecstasy") is a potentially neurotoxic recreational drug of abuse. Though the mechanisms involved are still not completely understood, formation of reactive metabolites and mitochondrial dysfunction contribute to MDMA-related neurotoxicity. Neuronal mitochondrial trafficking, and their targeting to synapses, is essential for proper neuronal function and survival, rendering neurons particularly vulnerable to mitochondrial dysfunction. Indeed, MDMA-associated disruption of Ca(2+) homeostasis and ATP depletion have been described in neurons, thus suggesting possible MDMA interference on mitochondrial dynamics. In this study, we performed real-time functional experiments of mitochondrial trafficking to explore the role of in situ mitochondrial dysfunction in MDMA's neurotoxic actions. We show that the mixture of MDMA and six of its major in vivo metabolites, each compound at 10μM, impaired mitochondrial trafficking and increased the fragmentation of axonal mitochondria in cultured hippocampal neurons. Furthermore, the overexpression of mitofusin 2 (Mfn2) or dynamin-related protein 1 (Drp1) K38A constructs almost completely rescued the trafficking deficits caused by this mixture. Finally, in hippocampal neurons overexpressing a Mfn2 mutant, Mfn2 R94Q, with impaired fusion and transport properties, it was confirmed that a dysregulation of mitochondrial fission/fusion events greatly contributed to the reported trafficking phenotype. In conclusion, our study demonstrated, for the first time, that the mixture of MDMA and its metabolites, at concentrations relevant to the in vivo scenario, impaired mitochondrial trafficking and increased mitochondrial fragmentation in hippocampal neurons, thus providing a new insight in the context of "ecstasy"-induced neuronal injury.

  17. Galectin-3 silencing inhibits epirubicin-induced ATP binding cassette transporters and activates the mitochondrial apoptosis pathway via β-catenin/GSK-3β modulation in colorectal carcinoma.

    Directory of Open Access Journals (Sweden)

    Yung-Kuo Lee

    Full Text Available Multidrug resistance (MDR, an unfavorable factor compromising the treatment efficacy of anticancer drugs, involves the upregulation of ATP binding cassette (ABC transporters and induction of galectin-3 signaling. Galectin-3 plays an anti-apoptotic role in many cancer cells and regulates various pathways to activate MDR. Thus, the inhibition of galectin-3 has the potential to enhance the efficacy of the anticancer drug epirubicin. In this study, we examined the effects and mechanisms of silencing galectin-3 via RNA interference (RNAi on the β-catenin/GSK-3β pathway in human colon adenocarcinoma Caco-2 cells. Galectin-3 knockdown increased the intracellular accumulation of epirubicin in Caco-2 cells; suppressed the mRNA expression of galectin-3, β-catenin, cyclin D1, c-myc, P-glycoprotein (P-gp, MDR-associated protein (MRP 1, and MRP2; and downregulated the protein expression of P-gp, cyclin D1, galectin-3, β-catenin, c-Myc, and Bcl-2. Moreover, galectin-3 RNAi treatment significantly increased the mRNA level of GSK-3β, Bax, caspase-3, and caspase-9; remarkably increased the Bax-to-Bcl-2 ratio; and upregulated the GSK-3β and Bax protein expressions. Apoptosis was induced by galectin-3 RNAi and/or epirubicin as demonstrated by chromatin condensation, a higher sub-G1 phase proportion, and increased caspase-3 and caspase-9 activity, indicating an intrinsic/mitochondrial apoptosis pathway. Epirubicin-mediated resistance was effectively inhibited via galectin-3 RNAi treatment. However, these phenomena could be rescued after galectin-3 overexpression. We show for the first time that the silencing of galectin-3 sensitizes MDR cells to epirubicin by inhibiting ABC transporters and activating the mitochondrial pathway of apoptosis through modulation of the β-catenin/GSK-3β pathway in human colon cancer cells.

  18. Mitochondrial Diseases

    Science.gov (United States)

    ... disorder, something goes wrong with this process. Mitochondrial diseases are a group of metabolic disorders. Mitochondria are ... cells and cause damage. The symptoms of mitochondrial disease can vary. It depends on how many mitochondria ...

  19. Mitochondrial Myopathies

    Science.gov (United States)

    ... which stimulates normal beating of the heart. Cardiac muscle damage also may occur. People with mitochondrial disorders may need to have regular examina- tions by a cardiologist. Other potential health issues Some people with mitochondrial disease experience ...

  20. Mitochondrial haplogroups

    DEFF Research Database (Denmark)

    Benn, Marianne; Schwartz, Marianne; Nordestgaard, Børge G;

    2008-01-01

    Rare mutations in the mitochondrial genome may cause disease. Mitochondrial haplogroups defined by common polymorphisms have been associated with risk of disease and longevity. We tested the hypothesis that common haplogroups predict risk of ischemic cardiovascular disease, morbidity from other...

  1. Salicylic acid binding of mitochondrial alpha-ketoglutarate dehydrogenase E2 affects mitochondrial oxidative phosphorylation and electron transport chain components and plays a role in basal defense against tobacco mosaic virus in tomato.

    Science.gov (United States)

    Liao, Yangwenke; Tian, Miaoying; Zhang, Huan; Li, Xin; Wang, Yu; Xia, Xiaojian; Zhou, Jie; Zhou, Yanhong; Yu, Jingquan; Shi, Kai; Klessig, Daniel F

    2015-02-01

    Salicylic acid (SA) plays a critical role in plant defense against pathogen invasion. SA-induced viral defense in plants is distinct from the pathways mediating bacterial and fungal defense and involves a specific pathway mediated by mitochondria; however, the underlying mechanisms remain largely unknown. The SA-binding activity of the recombinant tomato (Solanum lycopersicum) alpha-ketoglutarate dehydrogenase (Slα-kGDH) E2 subunit of the tricarboxylic acid (TCA) cycle was characterized. The biological role of this binding in plant defenses against tobacco mosaic virus (TMV) was further investigated via Slα-kGDH E2 silencing and transient overexpression in plants. Slα-kGDH E2 was found to bind SA in two independent assays. SA treatment, as well as Slα-kGDH E2 silencing, increased resistance to TMV. SA did not further enhance TMV defense in Slα-kGDH E2-silenced tomato plants but did reduce TMV susceptibility in Nicotiana benthamiana plants transiently overexpressing Slα-kGDH E2. Furthermore, Slα-kGDH E2-silencing-induced TMV resistance was fully blocked by bongkrekic acid application and alternative oxidase 1a silencing. These results indicated that binding by Slα-kGDH E2 of SA acts upstream of and affects the mitochondrial electron transport chain, which plays an important role in basal defense against TMV. The findings of this study help to elucidate the mechanisms of SA-induced viral defense.

  2. Mitochondrial genetics

    OpenAIRE

    Chinnery, Patrick Francis; Hudson, Gavin

    2013-01-01

    Introduction In the last 10 years the field of mitochondrial genetics has widened, shifting the focus from rare sporadic, metabolic disease to the effects of mitochondrial DNA (mtDNA) variation in a growing spectrum of human disease. The aim of this review is to guide the reader through some key concepts regarding mitochondria before introducing both classic and emerging mitochondrial disorders. Sources of data In this article, a review of the current mitochondrial genetics literature was con...

  3. Quantitative analysis of microtubule transport in growing nerve processes

    DEFF Research Database (Denmark)

    Ma*, Ytao; Shakiryanova*, Dinara; Vardya, Irina;

    2004-01-01

    the translocation of MT plus ends in the axonal shaft by expressing GFP-EB1 in Xenopus embryo neurons in culture. Formal quantitative analysis of MT assembly/disassembly indicated that none of the MTs in the axonal shaft were rapidly transported. Our results suggest that transport of axonal MTs is not required...

  4. Quantifying mechanical force in axonal growth and guidance

    Directory of Open Access Journals (Sweden)

    Ahmad Ibrahim Mahmoud Athamneh

    2015-09-01

    Full Text Available Mechanical force plays a fundamental role in neuronal development, physiology, and regeneration. In particular, research has shown that force is involved in growth cone-mediated axonal growth and guidance as well as stretch-induced elongation when an organism increases in size after forming initial synaptic connections. However, much of the details about the exact role of force in these fundamental processes remain unknown. In this review, we highlight (1 standing questions concerning the role of mechanical force in axonal growth and guidance and (2 different experimental techniques used to quantify forces in axons and growth cones. We believe that satisfying answers to these questions will require quantitative information about the relationship between elongation, forces, cytoskeletal dynamics, axonal transport, signaling, substrate adhesion, and stiffness contributing to directional growth advance. Furthermore, we address why a wide range of force values have been reported in the literature, and what these values mean in the context of neuronal mechanics. We hope that this review will provide a guide for those interested in studying the role of force in development and regeneration of neuronal networks.

  5. A Stochastic Multiscale Model That Explains the Segregation of Axonal Microtubules and Neurofilaments in Neurological Diseases.

    Directory of Open Access Journals (Sweden)

    Chuan Xue

    2015-08-01

    Full Text Available The organization of the axonal cytoskeleton is a key determinant of the normal function of an axon, which is a long thin projection of a neuron. Under normal conditions two axonal cytoskeletal polymers, microtubules and neurofilaments, align longitudinally in axons and are interspersed in axonal cross-sections. However, in many neurotoxic and neurodegenerative disorders, microtubules and neurofilaments segregate apart from each other, with microtubules and membranous organelles clustered centrally and neurofilaments displaced to the periphery. This striking segregation precedes the abnormal and excessive neurofilament accumulation in these diseases, which in turn leads to focal axonal swellings. While neurofilament accumulation suggests an impairment of neurofilament transport along axons, the underlying mechanism of their segregation from microtubules remains poorly understood for over 30 years. To address this question, we developed a stochastic multiscale model for the cross-sectional distribution of microtubules and neurofilaments in axons. The model describes microtubules, neurofilaments and organelles as interacting particles in a 2D cross-section, and is built upon molecular processes that occur on a time scale of seconds or shorter. It incorporates the longitudinal transport of neurofilaments and organelles through this domain by allowing stochastic arrival and departure of these cargoes, and integrates the dynamic interactions of these cargoes with microtubules mediated by molecular motors. Simulations of the model demonstrate that organelles can pull nearby microtubules together, and in the absence of neurofilament transport, this mechanism gradually segregates microtubules from neurofilaments on a time scale of hours, similar to that observed in toxic neuropathies. This suggests that the microtubule-neurofilament segregation can be a consequence of the selective impairment of neurofilament transport. The model generates the

  6. Oligodendroglial MCT1 and Metabolic Support of Axons in Multiple Sclerosis

    Science.gov (United States)

    2015-10-01

    transporter-- and hypothesize that loss of, or injury to, oligodendroglia in MS may produce axon damage through a failure of energy supply via loss of...function of this critical oligodendroglial protein. The successful completion of the Aims in this grant will not only further our understanding of axon...term, independent of this proposal- new innovative approaches toward enhancing this oligodendroglial pathway may provide one day – a powerful means

  7. Formation and Regulation of Mitochondrial Membranes

    Directory of Open Access Journals (Sweden)

    Laila Cigana Schenkel

    2014-01-01

    Full Text Available Mitochondrial membrane phospholipids are essential for the mitochondrial architecture, the activity of respiratory proteins, and the transport of proteins into the mitochondria. The accumulation of phospholipids within mitochondria depends on a coordinate synthesis, degradation, and trafficking of phospholipids between the endoplasmic reticulum (ER and mitochondria as well as intramitochondrial lipid trafficking. Several studies highlight the contribution of dietary fatty acids to the remodeling of phospholipids and mitochondrial membrane homeostasis. Understanding the role of phospholipids in the mitochondrial membrane and their metabolism will shed light on the molecular mechanisms involved in the regulation of mitochondrial function and in the mitochondrial-related diseases.

  8. Sonic Hedgehog Guides Axons via Zipcode Binding Protein 1-Mediated Local Translation.

    Science.gov (United States)

    Lepelletier, Léa; Langlois, Sébastien D; Kent, Christopher B; Welshhans, Kristy; Morin, Steves; Bassell, Gary J; Yam, Patricia T; Charron, Frédéric

    2017-02-15

    Sonic hedgehog (Shh) attracts spinal cord commissural axons toward the floorplate. How Shh elicits changes in the growth cone cytoskeleton that drive growth cone turning is unknown. We find that the turning of rat commissural axons up a Shh gradient requires protein synthesis. In particular, Shh stimulation increases β-actin protein at the growth cone even when the cell bodies have been removed. Therefore, Shh induces the local translation of β-actin at the growth cone. We hypothesized that this requires zipcode binding protein 1 (ZBP1), an mRNA-binding protein that transports β-actin mRNA and releases it for local translation upon phosphorylation. We found that Shh stimulation increases phospho-ZBP1 levels in the growth cone. Disruption of ZBP1 phosphorylation in vitro abolished the turning of commissural axons toward a Shh gradient. Disruption of ZBP1 function in vivo in mouse and chick resulted in commissural axon guidance errors. Therefore, ZBP1 is required for Shh to guide commissural axons. This identifies ZBP1 as a new mediator of noncanonical Shh signaling in axon guidance.SIGNIFICANCE STATEMENT Sonic hedgehog (Shh) guides axons via a noncanonical signaling pathway that is distinct from the canonical Hedgehog signaling pathway that specifies cell fate and morphogenesis. Axon guidance is driven by changes in the growth cone in response to gradients of guidance molecules. Little is known about the molecular mechanism of how Shh orchestrates changes in the growth cone cytoskeleton that are required for growth cone turning. Here, we show that the guidance of axons by Shh requires protein synthesis. Zipcode binding protein 1 (ZBP1) is an mRNA-binding protein that regulates the local translation of proteins, including actin, in the growth cone. We demonstrate that ZBP1 is required for Shh-mediated axon guidance, identifying a new member of the noncanonical Shh signaling pathway.

  9. Effects of TAT-conjugated platinum nanoparticles on lifespan of mitochondrial electron transport complex I-deficient Caenorhabditis elegans, nuo-1.

    Science.gov (United States)

    Sakaue, Yuri; Kim, Juewon; Miyamoto, Yusei

    2010-09-20

    Platinum nanoparticle (Pt-np) species are superoxide dismutase/catalase mimetics and also have an activity similar to that of mitochondrial electron transport complex I. To examine if this complex I-like activity functions in vivo, we studied the effects of Pt-nps on the lifespan of a mitochondrial complex I-deficient Caenorhabditis elegans mutant, nuo-1 (LB25) compared with wild-type N2. We synthesized a fusion protein of a cell-penetrating peptide, human immunodeficiency virus-1 TAT (48-60), C-terminally linked to a peptide with a high affinity to platinum (GRKKRRQRRRPPQ-DRTSTWR). Pt-nps were functionalized by conjugation with this fusion protein at a 1:1 ratio of TAT-PtBP to Pt atoms. Adult worms were treated with conjugated Pt-nps for 10 days. The mean lifespan of untreated N2 and LB25 was 19.6 ± 0.4 and 11.8 ± 0.3 days, respectively. Using 5 μM of conjugated Pt-nps, the lifespan of N2 and LB25 was maximally extended. This maximal lifespan extension of LB25 was 31.9 ± 2.6%, which was significantly greater than that of N2 (21.1 ± 1.7%, P < 0.05 by Student's t-test). Internalization of Pt into the whole body and mitochondria was similar between these two strains. Excessive accumulation of reactive oxygen species was not observed in the cytosol or mitochondria of untreated LB25. Treatment for five days with 5 μM conjugated Pt-nps decreased cytosolic and mitochondrial reactive oxygen species in N2 and LB25 to a similar extent. The ratio of [NAD(+)]/[NADH] was very low in the whole body and mitochondria of control LB25. After five days of treatment with 5 μM conjugated Pt-nps, the ratio of [NAD(+)]/[NADH] was increased in N2 and LB25. However, the degree of the increase was much higher in LB25 than in N2. Pt-nps function as NADH oxidase and recover the [NAD(+)]/[NADH] ratio in LB25, leading to effective extension of the lifespan of LB25.

  10. Mitochondrial cholesterol: mechanisms of import and effects on mitochondrial function.

    Science.gov (United States)

    Martin, Laura A; Kennedy, Barry E; Karten, Barbara

    2016-04-01

    Mitochondria require cholesterol for biogenesis and membrane maintenance, and for the synthesis of steroids, oxysterols and hepatic bile acids. Multiple pathways mediate the transport of cholesterol from different subcellular pools to mitochondria. In steroidogenic cells, the steroidogenic acute regulatory protein (StAR) interacts with a mitochondrial protein complex to mediate cholesterol delivery to the inner mitochondrial membrane for conversion to pregnenolone. In non-steroidogenic cells, several members of a protein family defined by the presence of a StAR-related lipid transfer (START) domain play key roles in the delivery of cholesterol to mitochondrial membranes. Subdomains of the endoplasmic reticulum (ER), termed mitochondria-associated ER membranes (MAM), form membrane contact sites with mitochondria and may contribute to the transport of ER cholesterol to mitochondria, either independently or in conjunction with lipid-transfer proteins. Model systems of mitochondria enriched with cholesterol in vitro and mitochondria isolated from cells with (patho)physiological mitochondrial cholesterol accumulation clearly demonstrate that mitochondrial cholesterol levels affect mitochondrial function. Increased mitochondrial cholesterol levels have been observed in several diseases, including cancer, ischemia, steatohepatitis and neurodegenerative diseases, and influence disease pathology. Hence, a deeper understanding of the mechanisms maintaining mitochondrial cholesterol homeostasis may reveal additional targets for therapeutic intervention. Here we give a brief overview of mitochondrial cholesterol import in steroidogenic cells, and then focus on cholesterol trafficking pathways that deliver cholesterol to mitochondrial membranes in non-steroidogenic cells. We also briefly discuss the consequences of increased mitochondrial cholesterol levels on mitochondrial function and their potential role in disease pathology.

  11. Mitochondrial vasculopathy

    Institute of Scientific and Technical Information of China (English)

    Josef Finsterer; Sinda Zarrouk-Mahjoub

    2016-01-01

    Mitochondrial disorders(MIDs)are usually multisystem disorders(mitochondrial multiorgan disorder syndrome)either on from onset or starting at a point during the disease course.Most frequently affected tissues are those with a high oxygen demand such as the central nervous system,the muscle,endocrine glands,or the myocardium.Recently,it has been shown that rarely alsothe arteries may be affected(mitochondrial arteriopathy).This review focuses on the type,diagnosis,and treat-ment of mitochondrial vasculopathy in MID patients.A literature search using appropriate search terms was carried out.Mitochondrial vasculopathy manifests as either microangiopathy or macroangiopathy.Clinical manifestations of mitochondrial microangiopathy include leukoencephalopathy,migraine-like headache,stroke-like episodes,or peripheral retinopathy.Mitochondrial macroangiopathy manifests as atherosclerosis,ectasia of arteries,aneurysm formation,dissection,or spontan-eous rupture of arteries.The diagnosis relies on the documentation and confirmation of the mitochondrial metabolic defect or the genetic cause after exclusion of non-MID causes.Treatment is not at variance compared to treatment of vasculopathy due to non-MID causes.Mitochondrial vasculopathy exists and manifests as micro-or macroangiopathy.Diagnosing mitochondrial vasculopathy is crucial since appropriate treatment may prevent from severe complications.

  12. The use of proteomic analysis to study trafficking defects in axons.

    Science.gov (United States)

    Fu, Xiaoqin; Brown, Kristy J; Rayavarapu, Sree; Nagaraju, Kanneboyina; Liu, Judy S

    2016-01-01

    Mutations in microtubule subunits and microtubule-associated proteins are the causes of many neurological disorders. These human conditions are usually associated with axonal tract defects or degeneration. The molecular mechanisms of these axonal dysfunction are still largely unknown. Conventional methods may not yield a complete analysis of downstream molecules related to axonal dysfunctions. Therefore, we devised a simple unbiased method to screen molecular motors and axonal molecules, which might be involved in axonal defects. We performed our analysis in the mouse with a targeted deletion in the doublecortin (Dcx) gene. Dcx is a microtubule-associated protein with direct effects on microtubule motors. Furthermore, the knockout of Dcx and its functionally redundant structurally similar paralog, doublecortin-like kinase 1 (Dclk1), in mouse results in thinner or absent axon tracts, including the corpus callosum and anterior commissures. We compared protein profiles of corpus callosum from Dcx knockout and wild-type mouse of P0-P2 using mass spectrometry. This strategy allowed us to identify novel candidates downstream of Dcx involved in axon transport.

  13. Electron Transport Disturbances and Neurodegeneration: From Albert Szent-Györgyi's Concept (Szeged) till Novel Approaches to Boost Mitochondrial Bioenergetics

    OpenAIRE

    Levente Szalárdy; Dénes Zádori; Péter Klivényi; József Toldi; László Vécsei

    2015-01-01

    Impaired function of certain mitochondrial respiratory complexes has long been linked to the pathogenesis of chronic neurodegenerative disorders such as Parkinson’s and Huntington’s diseases. Furthermore, genetic alterations of mitochondrial genome or nuclear genes encoding proteins playing essential roles in maintaining proper mitochondrial function can lead to the development of severe systemic diseases associated with neurodegeneration and vacuolar myelinopathy. At present, all of these di...

  14. AxonSeg: Open Source Software for Axon and Myelin Segmentation and Morphometric Analysis.

    Science.gov (United States)

    Zaimi, Aldo; Duval, Tanguy; Gasecka, Alicja; Côté, Daniel; Stikov, Nikola; Cohen-Adad, Julien

    2016-01-01

    Segmenting axon and myelin from microscopic images is relevant for studying the peripheral and central nervous system and for validating new MRI techniques that aim at quantifying tissue microstructure. While several software packages have been proposed, their interface is sometimes limited and/or they are designed to work with a specific modality (e.g., scanning electron microscopy (SEM) only). Here we introduce AxonSeg, which allows to perform automatic axon and myelin segmentation on histology images, and to extract relevant morphometric information, such as axon diameter distribution, axon density and the myelin g-ratio. AxonSeg includes a simple and intuitive MATLAB-based graphical user interface (GUI) and can easily be adapted to a variety of imaging modalities. The main steps of AxonSeg consist of: (i) image pre-processing; (ii) pre-segmentation of axons over a cropped image and discriminant analysis (DA) to select the best parameters based on axon shape and intensity information; (iii) automatic axon and myelin segmentation over the full image; and (iv) atlas-based statistics to extract morphometric information. Segmentation results from standard optical microscopy (OM), SEM and coherent anti-Stokes Raman scattering (CARS) microscopy are presented, along with validation against manual segmentations. Being fully-automatic after a quick manual intervention on a cropped image, we believe AxonSeg will be useful to researchers interested in large throughput histology. AxonSeg is open source and freely available at: https://github.com/neuropoly/axonseg.

  15. The Mitochondrial Metallochaperone SCO1 Is Required to Sustain Expression of the High-Affinity Copper Transporter CTR1 and Preserve Copper Homeostasis

    Directory of Open Access Journals (Sweden)

    Christopher J. Hlynialuk

    2015-02-01

    Full Text Available Human SCO1 fulfills essential roles in cytochrome c oxidase (COX assembly and the regulation of copper (Cu homeostasis, yet it remains unclear why pathogenic mutations in this gene cause such clinically heterogeneous forms of disease. Here, we establish a Sco1 mouse model of human disease and show that ablation of Sco1 expression in the liver is lethal owing to severe COX and Cu deficiencies. We further demonstrate that the Cu deficiency is explained by a functional connection between SCO1 and CTR1, the high-affinity transporter that imports Cu into the cell. CTR1 is rapidly degraded in the absence of SCO1 protein, and we show that its levels are restored in Sco1−/− mouse embryonic fibroblasts upon inhibition of the proteasome. These data suggest that mitochondrial signaling through SCO1 provides a post-translational mechanism to regulate CTR1-dependent Cu import into the cell, and they further underpin the importance of mitochondria in cellular Cu homeostasis.

  16. Axonal interferon responses and alphaherpesvirus neuroinvasion

    Science.gov (United States)

    Song, Ren

    Infection by alphaherpesviruses, including herpes simplex virus (HSV) and pseudorabies virus (PRV), typically begins at a peripheral epithelial surface and continues into the peripheral nervous system (PNS) that innervates this tissue. Inflammatory responses are induced at the infected peripheral site prior to viral invasion of the PNS. PNS neurons are highly polarized cells with long axonal processes that connect to distant targets. When the peripheral tissue is first infected, only the innervating axons are exposed to this inflammatory milieu, which include type I interferon (e.g. IFNbeta) and type II interferon (i.e. IFNgamma). IFNbeta can be produced by all types of cells, while IFNgamma is secreted by some specific types of immune cells. And both types of IFN induce antiviral responses in surrounding cells that express the IFN receptors. The fundamental question is how do PNS neurons respond to the inflammatory milieu experienced only by their axons. Axons must act as potential front-line barriers to prevent PNS infection and damage. Using compartmented cultures that physically separate neuron axons from cell bodies, I found that pretreating isolated axons with IFNbeta or IFNgamma significantly diminished the number of HSV-1 and PRV particles moving from axons to the cell bodies in an IFN receptor-dependent manner. Furthermore, I found the responses in axons are activated differentially by the two types of IFNs. The response to IFNbeta is a rapid, axon-only response, while the response to IFNgamma involves long distance signaling to the PNS cell body. For example, exposing axons to IFNbeta induced STAT1 phosphorylation (p-STAT1) only in axons, while exposure of axons to IFNgamma induced p-STAT1 accumulation in distant cell body nuclei. Blocking transcription in cell bodies eliminated IFNgamma-, but not IFNbeta-mediated antiviral effects. Proteomic analysis of IFNbeta- or IFNgamma-treated axons identified several differentially regulated proteins. Therefore

  17. Cable energy function of cortical axons.

    Science.gov (United States)

    Ju, Huiwen; Hines, Michael L; Yu, Yuguo

    2016-01-01

    Accurate estimation of action potential (AP)-related metabolic cost is essential for understanding energetic constraints on brain connections and signaling processes. Most previous energy estimates of the AP were obtained using the Na(+)-counting method, which seriously limits accurate assessment of metabolic cost of ionic currents that underlie AP conduction along the axon. Here, we first derive a full cable energy function for cortical axons based on classic Hodgkin-Huxley (HH) neuronal equations and then apply the cable energy function to precisely estimate the energy consumption of AP conduction along axons with different geometric shapes. Our analytical approach predicts an inhomogeneous distribution of metabolic cost along an axon with either uniformly or nonuniformly distributed ion channels. The results show that the Na(+)-counting method severely underestimates energy cost in the cable model by 20-70%. AP propagation along axons that differ in length may require over 15% more energy per unit of axon area than that required by a point model. However, actual energy cost can vary greatly depending on axonal branching complexity, ion channel density distributions, and AP conduction states. We also infer that the metabolic rate (i.e. energy consumption rate) of cortical axonal branches as a function of spatial volume exhibits a 3/4 power law relationship.

  18. Motor axon excitability during Wallerian degeneration

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Alvarez, Susana; Krarup, Christian

    2008-01-01

    , action potential propagation and structural integrity of the distal segment are maintained. The aim of this study was to investigate in vivo the changes in membrane function of motor axons during the 'latent' phase of Wallerian degeneration. Multiple indices of axonal excitability of the tibial nerve...

  19. Commissural axons of the mouse cochlear nucleus.

    Science.gov (United States)

    Brown, M Christian; Drottar, Marie; Benson, Thane E; Darrow, Keith

    2013-05-01

    The axons of commissural neurons that project from one cochlear nucleus to the other were studied after labeling with anterograde tracer. Injections were made into the dorsal subdivision of the cochlear nucleus in order to restrict labeling only to the group of commissural neurons that gave off collaterals to, or were located in, this subdivision. The number of labeled commissural axons in each injection was correlated with the number of labeled radiate multipolar neurons, suggesting radiate neurons as the predominant origin of the axons. The radiate commissural axons are thick and myelinated, and they exit the dorsal acoustic stria of the injected cochlear nucleus to cross the brainstem in the dorsal half, near the crossing position of the olivocochlear bundle. They enter the opposite cochlear nucleus via the dorsal and ventral acoustic stria and at its medial border. Reconstructions of single axons demonstrate that terminations are mostly in the core and typically within a single subdivision of the cochlear nucleus. Extents of termination range from narrow to broad along both the dorsoventral (i.e., tonotopic) and the rostrocaudal dimensions. In the electron microscope, labeled swellings form synapses that are symmetric (in that there is little postsynaptic density), a characteristic of inhibitory synapses. Our labeled axons do not appear to include excitatory commissural axons that end in edge regions of the nucleus. Radiate commissural axons could mediate the broadband inhibition observed in responses to contralateral sound, and they may balance input from the two ears with a quick time course.

  20. Ascending Midbrain Dopaminergic Axons Require Descending GAD65 Axon Fascicles for Normal Pathfinding

    Directory of Open Access Journals (Sweden)

    Claudia Marcela Garcia-Peña

    2014-06-01

    Full Text Available The Nigrostriatal pathway (NSP is formed by dopaminergic axons that project from the ventral midbrain to the dorsolateral striatum as part of the medial forebrain bundle. Previous studies have implicated chemotropic proteins in the formation of the NSP during development but little is known of the role of substrate-anchored signals in this process. We observed in mouse and rat embryos that midbrain dopaminergic axons ascend in close apposition to descending GAD65-positive axon bundles throughout their trajectory to the striatum. To test whether such interaction is important for dopaminergic axon pathfinding, we analyzed transgenic mouse embryos in which the GAD65 axon bundle was reduced by the conditional expression of the diphtheria toxin. In these embryos we observed dopaminergic misprojection into the hypothalamic region and abnormal projection in the striatum. In addition, analysis of Robo1/2 and Slit1/2 knockout embryos revealed that the previously described dopaminergic misprojection in these embryos is accompanied by severe alterations in the GAD65 axon scaffold. Additional studies with cultured dopaminergic neurons and whole embryos suggest that NCAM and Robo proteins are involved in the interaction of GAD65 and dopaminergic axons. These results indicate that the fasciculation between descending GAD65 axon bundles and ascending dopaminergic axons is required for the stereotypical NSP formation during brain development and that known guidance cues may determine this projection indirectly by instructing the pathfinding of the axons that are part of the GAD65 axon scaffold.

  1. Early events in axon/dendrite polarization.

    Science.gov (United States)

    Cheng, Pei-lin; Poo, Mu-ming

    2012-01-01

    Differentiation of axons and dendrites is a critical step in neuronal development. Here we review the evidence that axon/dendrite formation during neuronal polarization depends on the intrinsic cytoplasmic asymmetry inherited by the postmitotic neuron, the exposure of the neuron to extracellular chemical factors, and the action of anisotropic mechanical forces imposed by the environment. To better delineate the functions of early signals among a myriad of cellular components that were shown to influence axon/dendrite formation, we discuss their functions by distinguishing their roles as determinants, mediators, or modulators and consider selective degradation of these components as a potential mechanism for axon/dendrite polarization. Finally, we examine whether these early events of axon/dendrite formation involve local autocatalytic activation and long-range inhibition, as postulated by Alan Turing for the morphogenesis of patterned biological structure.

  2. A macroscopic model of traffic jams in axons.

    Science.gov (United States)

    Kuznetsov, A V; Avramenko, A A

    2009-04-01

    The purpose of this paper is to develop a minimal macroscopic model capable of explaining the formation of traffic jams in fast axonal transport. The model accounts for the decrease of the number density of positively (and negatively) oriented microtubules near the location of the traffic jam due to formation of microtubule swirls; the model also accounts for the reduction of the effective velocity of organelle transport in the traffic jam region due to organelles falling off microtubule tracks more often in the swirl region. The model is based on molecular-motor-assisted transport equations and the hydrodynamic model of traffic jams in highway traffic. Parametric analyses of the model's predictions for various values of viscosity of the traffic flow, variance of the velocity distribution, diffusivity of microtubule-bound and free organelles, rate constants for binding to and detachment from microtubules, relaxation time, and average motor velocities of the retrograde and anterograde transport, are carried out.

  3. Mitochondrial Dysfunction in Parkinson's Disease

    Directory of Open Access Journals (Sweden)

    P. C. Keane

    2011-01-01

    Full Text Available Parkinson's disease (PD is a progressive, neurodegenerative condition that has increasingly been linked with mitochondrial dysfunction and inhibition of the electron transport chain. This inhibition leads to the generation of reactive oxygen species and depletion of cellular energy levels, which can consequently cause cellular damage and death mediated by oxidative stress and excitotoxicity. A number of genes that have been shown to have links with inherited forms of PD encode mitochondrial proteins or proteins implicated in mitochondrial dysfunction, supporting the central involvement of mitochondria in PD. This involvement is corroborated by reports that environmental toxins that inhibit the mitochondrial respiratory chain have been shown to be associated with PD. This paper aims to illustrate the considerable body of evidence linking mitochondrial dysfunction with neuronal cell death in the substantia nigra pars compacta (SNpc of PD patients and to highlight the important need for further research in this area.

  4. OXPHOS-Dependent Cells Identify Environmental Disruptors of Mitochondrial Function

    Science.gov (United States)

    Mitochondrial dysfunction is associated with numerous chronic diseases including metabolic syndrome. Environmental chemicals can impair mitochondrial function through numerous mechanisms such as membrane disruption, complex inhibition and electron transport chain uncoupling. Curr...

  5. Mdivi-1 inhibits astrocyte activation and astroglial scar formation and enhances axonal regeneration after spinal cord injury in rats

    Directory of Open Access Journals (Sweden)

    gang li

    2016-10-01

    Full Text Available After spinal cord injury (SCI, astrocytes become hypertrophic and proliferative, forming a dense network of astroglial processes at the site of the lesion. This constitutes a physical and biochemical barrier to axonal regeneration. Mitochondrial fission regulates cell cycle progression; inhibiting the cell cycle of astrocytes can reduce expression levels of axon growth-inhibitory molecules as well as astroglial scar formation after SCI. We therefore investigated how an inhibitor of mitochondrial fission, Mdivi-1, would affect astrocyte proliferation, astroglial scar formation, and axonal regeneration following SCI in rats. Western blot and immunofluorescent double-labeling showed that Mdivi-1 markedly reduced the expression of the astrocyte marker glial fibrillary acidic protein (GFAP, and a cell proliferation marker, proliferating cell nuclear antigen, in astrocytes 3 days after SCI. Moreover, Mdivi-1 decreased the expression of GFAP and neurocan, a chondroitin sulfate proteoglycan. Notably, immunofluorescent labeling and Nissl staining showed that Mdivi-1 elevated the production of growth-associated protein-43 and increased neuronal survival at 4 weeks after SCI. Finally, hematoxylin-eosin staining and behavioral evaluation of motor function indicated that Mdivi-1 also reduced cavity formation and improved motor function 4 weeks after SCI. Our results confirm that Mdivi-1 promotes motor function after SCI, and indicate that inhibiting mitochondrial fission using Mdivi-1 can inhibit astrocyte activation and astroglial scar formation and contribute to axonal regeneration after SCI in rats.

  6. Characterization of axo-axonic synapses in the piriform cortex of Mus musculus.

    Science.gov (United States)

    Wang, Xinjun; Sun, Qian-Quan

    2012-03-01

    Previous anatomical and physiological studies have established major glutamatergic and GABAergic neuronal subtypes within the piriform cortical circuits. However, quantitative information regarding axo-axonic inhibitory synapses mediated by chandelier cells across major cortical subdivisions of piriform cortex is lacking. Therefore, we examined the properties of these synapses across the entire piriform cortex. Our results show the following. 1) γ-Aminobutyric acid membrane transporter 1-positive varicosities, whose appearance resembles chandelier cartridges, are found around the initial segments of axons of glutamatergic cells across layers II and III. 2) Both the density of axo-axonic cartridges and the degree of γ-aminobutyric acid membrane transporter 1 innervation in each axo-axonic synapse are significantly higher in the piriform cortex than in the neocortex. 3) Glutamate decarboxylase 67, vesicular GABA transporter, and parvalbumin, but not calbindin, are colocalized with the presynaptic varicosities, whereas gephyrin, Na-K-2Cl cotransporter 1, and GABA(A) receptor α1 subunit, but not K-Cl cotransporter 2, are colocalized at the presumed postsynaptic sites. 4) The axo-axonic cartridges innervate the majority of excitatory neurons and are distributed more frequently in putative centrifugal cells and posterior piriform cortex. We further describe the morphology of chandelier cells by using parvalbumin-immunoreactivity and single-cell labeling. In summary, our results demonstrate that a small population of chandelier cells mediates abundant axo-axonic synapses across the entire piriform cortex. Because of the critical location of these inhibitory synapses in relation to action potential regulation, our results highlight a critical role of axo-axonic synapses in regulating information flow and olfactory-related oscillations within the piriform cortex in vivo.

  7. Mitochondrial disorders.

    Science.gov (United States)

    Zeviani, M; Tiranti, V; Piantadosi, C

    1998-01-01

    Mitochondrial respiration, the most efficient metabolic pathway devoted to energy production, is at the crosspoint of 2 quite different genetic systems, the nuclear genome and the mitochondrial genome (mitochondrial DNA, mtDNA). The latter encodes a few essential components of the mitochondrial respiratory chain and has unique molecular and genetic properties that account for some of the peculiar features of mitochondrial disorders. However, the perpetuation, propagation, and expression of mtDNA, the majority of the subunits of the respiratory complexes, as well as a number of genes involved in their assembly and turnover, are contained in the nuclear genome. Although mitochondrial disorders have been known for more than 30 years, a major breakthrough in their understanding has come much later, with the discovery of an impressive, ever-increasing number of mutations of mitochondrial DNA. Partial deletions or duplications of mtDNA, or maternally inherited point mutations, have been associated with well-defined clinical syndromes. However, phenotypes transmitted as mendelian traits have also been identified. These include clinical entities defined on the basis of specific biochemical defects, and also a few autosomal dominant or recessive syndromes associated with multiple deletions or tissue-specific depletion of mtDNA. Given the complexity of mitochondrial genetics and biochemistry, the clinical manifestations of mitochondrial disorders are extremely heterogenous. They range from lesions of single tissues or structures, such as the optic nerve in Leber hereditary optic neuropathy or the cochlea in maternally inherited nonsyndromic deafness, to more widespread lesions including myopathies, encephalomyopathies, cardiopathies, or complex multisystem syndromes. The recent advances in genetic studies provide both diagnostic tools and new pathogenetic insights in this rapidly expanding area of human pathology.

  8. Efficient simulations of tubulin-driven axonal growth.

    Science.gov (United States)

    Diehl, Stefan; Henningsson, Erik; Heyden, Anders

    2016-08-01

    This work concerns efficient and reliable numerical simulations of the dynamic behaviour of a moving-boundary model for tubulin-driven axonal growth. The model is nonlinear and consists of a coupled set of a partial differential equation (PDE) and two ordinary differential equations. The PDE is defined on a computational domain with a moving boundary, which is part of the solution. Numerical simulations based on standard explicit time-stepping methods are too time consuming due to the small time steps required for numerical stability. On the other hand standard implicit schemes are too complex due to the nonlinear equations that needs to be solved in each step. Instead, we propose to use the Peaceman-Rachford splitting scheme combined with temporal and spatial scalings of the model. Simulations based on this scheme have shown to be efficient, accurate, and reliable which makes it possible to evaluate the model, e.g. its dependency on biological and physical model parameters. These evaluations show among other things that the initial axon growth is very fast, that the active transport is the dominant reason over diffusion for the growth velocity, and that the polymerization rate in the growth cone does not affect the final axon length.

  9. Capsazepine抑制培养海马神经元网络线粒体转运%Capsazepine inhibits mitochondrial transport in cultured hippocampal neuronal networks of rat

    Institute of Scientific and Technical Information of China (English)

    付敏; 潘丽洁; 孙朝晖; 左焕琮; 谢佐平

    2009-01-01

    capsazepine(CZP)是辣椒素的合成类似物,也是野香草型瞬时感受器电位通道1(TRPV1)的选择性抑制剂.TRPV1在体内有广泛的表达谱,使CZP有广泛的作用位点.除此之外,以往的研究结果表明CZP除了作用于TRPVI外还有更复杂的信号通路.本课题研究了CZP对体外培养的大鼠海马神经元网络内线粒体转运的作用并分析其可能机制.结果显示:20 μmol/L的CZP可有效抑制原代培养海马神经元网络中的线粒体转运.CZP急性作用不引起胞内钙离子浓度的升高,也不引起细胞的凋亡.胞外更换为无外钙记录液,或者将GSK3g抑制剂SB415286与CZP共孵育,均不影响CZP对线粒体转运的抑制作用.然而,将BAPTA-AM与CZP共孵育,抑制了CZP对线粒体转运的抑制作用.本研究结果表明,CZP直接通过胞内钙信号通路影响神经元的线粒体转运,与胞外钙流或转运蛋白的磷酸化无关.%Capsazepine is a ByntlIetic analogue of capsaicin and a selective inhibitor of transient receptor potential vanilloid 1 channel (TRPV1).TRPV1 has wide expression profile,providing extensive targets for capsazepine.Evidence from previous studies showed that capsazepine acted more complex effects through other than TRPV1 signal pathway.In this study.we examined its effect and underlying mechanisms on mitochondrial transport of cultured hippecampal neurons in rats.The data showed that the number of the moving mitochondria in primarily cultured hippocampal neurons was remarkably decreased by 20 μmol/L capsazepine.Contradicted to previous study,the intracellular calcium concentration was not elevated.Capsazepine did not induce cell death in acute incubation.The inhibitory effect of capsasepine was not prevented by co-application of SB415286,the inhibitor of GSK313 or by replacing extracellular recording solution to calcium-free saline,but prevented by co-application of BAPTA-AM.These results indicated that capsazepine inhibited mitochondrial trans

  10. Electron Transport Disturbances and Neurodegeneration: From Albert Szent-Györgyi’s Concept (Szeged till Novel Approaches to Boost Mitochondrial Bioenergetics

    Directory of Open Access Journals (Sweden)

    Levente Szalárdy

    2015-01-01

    Full Text Available Impaired function of certain mitochondrial respiratory complexes has long been linked to the pathogenesis of chronic neurodegenerative disorders such as Parkinson’s and Huntington’s diseases. Furthermore, genetic alterations of mitochondrial genome or nuclear genes encoding proteins playing essential roles in maintaining proper mitochondrial function can lead to the development of severe systemic diseases associated with neurodegeneration and vacuolar myelinopathy. At present, all of these diseases lack effective disease modifying therapy. Following a brief commemoration of Professor Albert Szent-Györgyi, a Nobel Prize laureate who pioneered in the field of cellular respiration, antioxidant processes, and the roles of free radicals in health and disease, the present paper overviews the current knowledge on the involvement of mitochondrial dysfunction in central nervous system diseases associated with neurodegeneration including Parkinson’s and Huntington’s disease as well as mitochondrial encephalopathies. The review puts special focus on the involvement and the potential therapeutic relevance of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α, a nuclear-encoded master regulator of mitochondrial biogenesis and antioxidant responses in these disorders, the transcriptional activation of which may hold novel therapeutic value as a more system-based approach aiming to restore mitochondrial functions in neurodegenerative processes.

  11. Electron Transport Disturbances and Neurodegeneration: From Albert Szent-Györgyi's Concept (Szeged) till Novel Approaches to Boost Mitochondrial Bioenergetics.

    Science.gov (United States)

    Szalárdy, Levente; Zádori, Dénes; Klivényi, Péter; Toldi, József; Vécsei, László

    2015-01-01

    Impaired function of certain mitochondrial respiratory complexes has long been linked to the pathogenesis of chronic neurodegenerative disorders such as Parkinson's and Huntington's diseases. Furthermore, genetic alterations of mitochondrial genome or nuclear genes encoding proteins playing essential roles in maintaining proper mitochondrial function can lead to the development of severe systemic diseases associated with neurodegeneration and vacuolar myelinopathy. At present, all of these diseases lack effective disease modifying therapy. Following a brief commemoration of Professor Albert Szent-Györgyi, a Nobel Prize laureate who pioneered in the field of cellular respiration, antioxidant processes, and the roles of free radicals in health and disease, the present paper overviews the current knowledge on the involvement of mitochondrial dysfunction in central nervous system diseases associated with neurodegeneration including Parkinson's and Huntington's disease as well as mitochondrial encephalopathies. The review puts special focus on the involvement and the potential therapeutic relevance of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α), a nuclear-encoded master regulator of mitochondrial biogenesis and antioxidant responses in these disorders, the transcriptional activation of which may hold novel therapeutic value as a more system-based approach aiming to restore mitochondrial functions in neurodegenerative processes.

  12. Repositioning of Verrucosidin, a purported inhibitor of chaperone protein GRP78, as an inhibitor of mitochondrial electron transport chain complex I.

    Directory of Open Access Journals (Sweden)

    Simmy Thomas

    Full Text Available Verrucosidin (VCD belongs to a group of fungal metabolites that were identified in screening programs to detect molecules that preferentially kill cancer cells under glucose-deprived conditions. Its mode of action was proposed to involve inhibition of increased GRP78 (glucose regulated protein 78 expression during hypoglycemia. Because GRP78 plays an important role in tumorigenesis, inhibitors such as VCD might harbor cancer therapeutic potential. We therefore sought to characterize VCD's anticancer activity in vitro. Triple-negative breast cancer cell lines MDA-MB-231 and MDA-MB-468 were treated with VCD under different conditions known to trigger increased expression of GRP78, and a variety of cellular processes were analyzed. We show that VCD was highly cytotoxic only under hypoglycemic conditions, but not in the presence of normal glucose levels, and VCD blocked GRP78 expression only when glycolysis was impaired (due to hypoglycemia or the presence of the glycolysis inhibitor 2-deoxyglucose, but not when GRP78 was induced by other means (hypoxia, thapsigargin, tunicamycin. However, VCD's strictly hypoglycemia-specific toxicity was not due to the inhibition of GRP78. Rather, VCD blocked mitochondrial energy production via inhibition of complex I of the electron transport chain. As a result, cellular ATP levels were quickly depleted under hypoglycemic conditions, and common cellular functions, including general protein synthesis, deteriorated and resulted in cell death. Altogether, our study identifies mitochondria as the primary target of VCD. The possibility that other purported GRP78 inhibitors (arctigenin, biguanides, deoxyverrucosidin, efrapeptin, JBIR, piericidin, prunustatin, pyrvinium, rottlerin, valinomycin, versipelostatin might act in a similar GRP78-independent fashion will be discussed.

  13. Mitochondrial genome depletion dysregulates bile acid- and paracetamol-induced expression of the transporters Mdr1, Mrp1 and Mrp4 in liver cells

    Science.gov (United States)

    Perez, MJ; Gonzalez-Sanchez, E; Gonzalez-Loyola, A; Gonzalez-Buitrago, JM; Marin, JJG

    2011-01-01

    BACKGROUND AND PURPOSE Mitochondria are involved in the toxicity of several compounds, retro-control of gene expression and apoptosis activation. The effect of mitochondrial genome (mtDNA) depletion on changes in ABC transporter protein expression in response to bile acids and paracetamol was investigated. EXPERIMENTAL APPROACH Hepa 1-6 mouse hepatoma cells with 70% decrease in 16S/18S rRNA ratio (Rho cells) were obtained by long-term treatment with ethidium bromide. KEY RESULTS Spontaneous apoptosis and reactive oxygen species (ROS) generation were decreased in Rho cells. Following glycochenodeoxycholic acid (GCDCA) or paracetamol, Rho cells generated less ROS and were more resistant to cell death. Apoptosis induced by GCDCA and Fas was also reduced. The basal expression of Mdr1 was significantly enhanced, but this was not further stimulated by GCDCA or paracetamol, as observed in wild-type (WT) cells. Basal expression of Mrp1 and Mrp4 was similar in WT and Rho cells, whereas they were up-regulated only in WT cells after GCDCA or paracetamol, along with the transcription factors Shp and Nrf2, but not Fxr or Pxr. Increased expression of Nrf2 was accompanied by its enhanced nuclear translocation. Glycoursodeoxycholic acid failed to cause any of the effects observed for GCDCA or paracetamol. CONCLUSIONS AND IMPLICATIONS The Nrf2-mediated pathway is partly independent of ROS production. Nuclear translocation of Nrf2 is insufficient to up-regulate Mdr1, Mrp1 and Mrp4, which requires the participation of other regulatory element(s) whose activation in response to GCDCA and paracetamol is impaired in Rho cells and hence probably sensitive to ROS. PMID:21175587

  14. Laser-based single-axon transection for high-content axon injury and regeneration studies.

    Directory of Open Access Journals (Sweden)

    Darío Kunik

    Full Text Available The investigation of the regenerative response of the neurons to axonal injury is essential to the development of new axoprotective therapies. Here we study the retinal neuronal RGC-5 cell line after laser transection, demonstrating that the ability of these cells to initiate a regenerative response correlates with axon length and cell motility after injury. We show that low energy picosecond laser pulses can achieve transection of unlabeled single axons in vitro and precisely induce damage with micron precision. We established the conditions to achieve axon transection, and characterized RGC-5 axon regeneration and cell body response using time-lapse microscopy. We developed an algorithm to analyze cell trajectories and established correlations between cell motility after injury, axon length, and the initiation of the regeneration response. The characterization of the motile response of axotomized RGC-5 cells showed that cells that were capable of repair or regrowth of damaged axons migrated more slowly than cells that could not. Moreover, we established that RGC-5 cells with long axons could not recover their injured axons, and such cells were much more motile. The platform we describe allows highly controlled axonal damage with subcellular resolution and the performance of high-content screening in cell cultures.

  15. Extra-neurohypophyseal axonal projections from individual vasopressin-containing magnocellular neurons in rat hypothalamus

    Directory of Open Access Journals (Sweden)

    Vito Salvador Hernandez

    2015-10-01

    Full Text Available Conventional neuroanatomical, immunohistochemical techniques and electrophysiological recording, as well as in vitro labeling methods may fail to detect long range extra-neurohypophyseal-projecting axons from vasopressin (AVP-containing magnocellular neurons (magnocells in the hypothalamic paraventricular nucleus (PVN. Here, we used in vivo extracellular recording, juxtacellular labeling, post hoc anatomo-immunohistochemical analysis and camera lucida reconstruction to address this question. We demonstrate that all well-labeled AVP immunopositive neurons inside the PVN possess main axons joining the tract of Greving and multi-axon-like processes, as well as axonal collaterals branching very near to the somata, which project to extra-neurohypophyseal regions. The detected regions in this study include the medial and lateral preoptical area, suprachiasmatic nucleus, lateral habenula, medial and central amygdala and the conducting systems, such as stria medullaris, the fornix and the internal capsule. Expression of vesicular glutamate transporter 2 was observed in axon-collaterals. These results, in congruency with several previous reports in the literature, provided unequivocal evidence that AVP magnocells have an uncommon feature of possessing multiple axon-like processes emanating from somata or proximal dendrites. Furthermore, the long-range non-neurohypophyseal projections are more common than an occasional phenomenon as previously thought.

  16. Exportability of the mitochondrial oxidative phosphorylation machinery into myelin sheath.

    Science.gov (United States)

    Morelli, Alessandro; Ravera, Silvia; Calzia, Daniela; Panfoli, Isabella

    2011-01-01

    White matter comprises over half of the brain, and its role in axonal survival is being reconsidered, consistently with the observation that axonal degeneration follows demyelination. The recent evidence of an extra-mitochondrial aerobic ATP production in isolated myelin vesicles, thanks to the expression therein of the mitochondrial Oxydative Phosphorylation (OXPHOS) machinery, stands in for myelin playing a functional bioenergetic role in ATP supply for the axon. The observation that subunits of the OXPHOS encoded by the mitochondrial genome are expressed in myelin, suggests that they can be the same as those of the inner mitochondrial membrane. This would mean that the OXPHOS is exportable. Here the hypothesis is exposed that the mitochondrion is the unique site of the assembly of the OXPHOS, so that this is exported to those sub cellular districts displaying high energy demand, such as myelin sheath. There the OXPHOS would display a higher efficiency in oxidative ATP production than inside the mitochondrion itself In this respect, the role of the glia in the nervous conduction is shed new light and the oligodendrocyte mitochondrial OXPHOS are hypothesized to be delivered to nascent myelin.

  17. Axon initial segment Kv1 channels control axonal action potential waveform and synaptic efficacy.

    Science.gov (United States)

    Kole, Maarten H P; Letzkus, Johannes J; Stuart, Greg J

    2007-08-16

    Action potentials are binary signals that transmit information via their rate and temporal pattern. In this context, the axon is thought of as a transmission line, devoid of a role in neuronal computation. Here, we show a highly localized role of axonal Kv1 potassium channels in shaping the action potential waveform in the axon initial segment (AIS) of layer 5 pyramidal neurons independent of the soma. Cell-attached recordings revealed a 10-fold increase in Kv1 channel density over the first 50 microm of the AIS. Inactivation of AIS and proximal axonal Kv1 channels, as occurs during slow subthreshold somatodendritic depolarizations, led to a distance-dependent broadening of axonal action potentials, as well as an increase in synaptic strength at proximal axonal terminals. Thus, Kv1 channels are strategically positioned to integrate slow subthreshold signals, providing control of the presynaptic action potential waveform and synaptic coupling in local cortical circuits.

  18. The developmentally regulated expression of Menkes protein ATP7A suggests a role in axon extension and synaptogenesis.

    Science.gov (United States)

    El Meskini, Rajaâ; Cline, Laura B; Eipper, Betty A; Ronnett, Gabriele V

    2005-01-01

    Menkes disease (MD) is a neurodegenerative disorder caused by mutation of the copper transporter ATP7A. While several enzymes expressed in mature neurons require copper, MD neurodegenerative changes cannot be explained by known requirements for ATP7A in neuronal development. To investigate additional roles for ATP7A during development, we characterized its pattern of expression using the olfactory system as a neurodevelopmental model. ATP7A expression in neurons was developmentally regulated rather than constitutively. Initially expressed in the cell bodies of developing neurons, ATP7A protein later shifted to extending axons, peaking prior to synaptogenesis. Similarly, after injury-stimulated neurogenesis, ATP7A expression increased in neurons and axons preceding synaptogenesis. Interestingly, copper-transport-deficient ATP7A still exhibits axonal localization. These results support a role for ATP7A in axon extension, which may contribute to the severe neurodegeneration characteristic of MD.

  19. The effect of mitochondrial calcium uniporter on mitochondrial fission in hippocampus cells ischemia/reperfusion injury

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Lantao; Li, Shuhong; Wang, Shilei, E-mail: wshlei@aliyun.com; Yu, Ning; Liu, Jia

    2015-06-05

    The mitochondrial calcium uniporter (MCU) transports free Ca{sup 2+} into the mitochondrial matrix, maintaining Ca{sup 2+} homeostasis, thus regulates the mitochondrial morphology. Previous studies have indicated that there was closely crosstalk between MCU and mitochondrial fission during the process of ischemia/reperfusion injury. This study constructed a hypoxia reoxygenation model using primary hippocampus neurons to mimic the cerebral ischemia/reperfusion injury and aims to explore the exactly effect of MCU on the mitochondrial fission during the process of ischemia/reperfusion injury and so as the mechanisms. Our results found that the inhibitor of the MCU, Ru360, decreased mitochondrial Ca{sup 2+} concentration, suppressed the expression of mitochondrial fission protein Drp1, MIEF1 and Fis1, and thus improved mitochondrial morphology significantly. Whereas spermine, the agonist of the MCU, had no significant impact compared to the I/R group. This study demonstrated that the MCU regulates the process of mitochondrial fission by controlling the Ca{sup 2+} transport, directly upregulating mitochondrial fission proteins Drp1, Fis1 and indirectly reversing the MIEF1-induced mitochondrial fusion. It also provides new targets for brain protection during ischemia/reperfusion injury. - Highlights: • We study MCU with primary neuron culture. • MCU induces mitochondrial fission. • MCU reverses MIEF1 effect.

  20. Genetics Home Reference: giant axonal neuropathy

    Science.gov (United States)

    ... R. Proteomic analysis in giant axonal neuropathy: new insights into disease mechanisms. Muscle Nerve. 2012 Aug;46( ... healthcare professional . About Genetics Home Reference Site Map Customer Support Selection Criteria for Links USA.gov Copyright ...

  1. Genetic dissection of myelinated axons in zebrafish

    OpenAIRE

    2009-01-01

    In the vertebrate nervous system, the myelin sheath allows for rapid and efficient conduction of action potentials along axons. Despite the essential function of myelin, many questions remain unanswered about the mechanisms that govern the development of myelinated axons. The fundamental properties of myelin are widely shared among vertebrates, and the zebrafish has emerged as a powerful system to study myelination in vivo. This review will highlight recent advances from genetic screens in ze...

  2. SOD1 targeted to the mitochondrial intermembrane space prevents motor neuropathy in the Sod1 knockout mouse.

    Science.gov (United States)

    Fischer, Lindsey R; Igoudjil, Anissa; Magrané, Jordi; Li, Yingjie; Hansen, Jason M; Manfredi, Giovanni; Glass, Jonathan D

    2011-01-01

    Motor axon degeneration is a critical but poorly understood event leading to weakness and muscle atrophy in motor neuron diseases. Here, we investigated oxidative stress-mediated axonal degeneration in mice lacking the antioxidant enzyme, Cu,Zn superoxide dismutase (SOD1). We demonstrate a progressive motor axonopathy in these mice and show that Sod1(-/-) primary motor neurons extend short axons in vitro with reduced mitochondrial density. Sod1(-/-) neurons also show oxidation of mitochondrial--but not cytosolic--thioredoxin, suggesting that loss of SOD1 causes preferential oxidative stress in mitochondria, a primary source of superoxide in cells. SOD1 is widely regarded as the cytosolic isoform of superoxide dismutase, but is also found in the mitochondrial intermembrane space. The functional significance of SOD1 in the intermembrane space is unknown. We used a transgenic approach to express SOD1 exclusively in the intermembrane space and found that mitochondrial SOD1 is sufficient to prevent biochemical and morphological defects in the Sod1(-/-) model, and to rescue the motor phenotype of these mice when followed to 12 months of age. These results suggest that SOD1 in the mitochondrial intermembrane space is fundamental for motor axon maintenance, and implicate oxidative damage initiated at mitochondrial sites in the pathogenesis of motor axon degeneration.

  3. Crossing axons in the third nerve nucleus.

    Science.gov (United States)

    Bienfang, D C

    1975-12-01

    The research presented in this paper studied the pathway taken by the crossed fibers of the third nerve nucleus in an animal whose nucleus has been well mapped and found to correlate well with higher mammals and man. Autoradiography using tritiated amino acid labeled the cell bodies an axons of the left side of the oculomotor nucleus of the cat. Axons so labeled could be seen emerging from the ventral portion of the left nucleus through the median longitudinal fasciculus (mlf) to join the left oculomotor nerve. Labeled axons were also seen to emerge from the medial border of the caudal left nucleus, cross the midline, and pass through the right nucleus and the right mlf to join the right oculomotor nerve. These latter axons must be the crossed axons of the superior rectus and levator palpebrae subnuclei. Since the path of these crossed axons is through the caudal portion of the nucleus of the opposite side, the destruction of one lateral half of the oculomotor nucleus would result in a bilateral palsy of the crossed subnuclei. Bilateral palsy of the superior rectus and bilateral assymetrical palsy of the levator palpebrae muscles would result.

  4. Melatonin mitigates mitochondrial malfunction.

    Science.gov (United States)

    León, Josefa; Acuña-Castroviejo, Darío; Escames, Germane; Tan, Dun-Xian; Reiter, Russel J

    2005-01-01

    Melatonin, or N-acetyl-5-methoxytryptamine, is a compound derived from tryptophan that is found in all organisms from unicells to vertebrates. This indoleamine may act as a protective agent in disease conditions such as Parkinson's, Alzheimer's, aging, sepsis and other disorders including ischemia/reperfusion. In addition, melatonin has been proposed as a drug for the treatment of cancer. These disorders have in common a dysfunction of the apoptotic program. Thus, while defects which reduce apoptotic processes can exaggerate cancer, neurodegenerative disorders and ischemic conditions are made worse by enhanced apoptosis. The mechanism by which melatonin controls cell death is not entirely known. Recently, mitochondria, which are implicated in the intrinsic pathway of apoptosis, have been identified as a target for melatonin actions. It is known that melatonin scavenges oxygen and nitrogen-based reactants generated in mitochondria. This limits the loss of the intramitochondrial glutathione and lowers mitochondrial protein damage, improving electron transport chain (ETC) activity and reducing mtDNA damage. Melatonin also increases the activity of the complex I and complex IV of the ETC, thereby improving mitochondrial respiration and increasing ATP synthesis under normal and stressful conditions. These effects reflect the ability of melatonin to reduce the harmful reduction in the mitochondrial membrane potential that may trigger mitochondrial transition pore (MTP) opening and the apoptotic cascade. In addition, a reported direct action of melatonin in the control of currents through the MTP opens a new perspective in the understanding of the regulation of apoptotic cell death by the indoleamine.

  5. Mitochondrial dysfunction in heart failure.

    Science.gov (United States)

    Rosca, Mariana G; Hoppel, Charles L

    2013-09-01

    Heart failure (HF) is a complex chronic clinical syndrome. Energy deficit is considered to be a key contributor to the development of both cardiac and skeletal myopathy. In HF, several components of cardiac and skeletal muscle bioenergetics are altered, such as oxygen availability, substrate oxidation, mitochondrial ATP production, and ATP transfer to the contractile apparatus via the creatine kinase shuttle. This review focuses on alterations in mitochondrial biogenesis and respirasome organization, substrate oxidation coupled with ATP synthesis in the context of their contribution to the chronic energy deficit, and mechanical dysfunction of the cardiac and skeletal muscle in HF. We conclude that HF is associated with decreased mitochondrial biogenesis and function in both heart and skeletal muscle, supporting the concept of a systemic mitochondrial cytopathy. The sites of mitochondrial defects are located within the electron transport and phosphorylation apparatus and differ with the etiology and progression of HF in the two mitochondrial populations (subsarcolemmal and interfibrillar) of cardiac and skeletal muscle. The roles of adrenergic stimulation, the renin-angiotensin system, and cytokines are evaluated as factors responsible for the systemic energy deficit. We propose a cyclic AMP-mediated mechanism by which increased adrenergic stimulation contributes to the mitochondrial dysfunction.

  6. MitoTimer probe reveals the impact of autophagy, fusion, and motility on subcellular distribution of young and old mitochondrial protein and on relative mitochondrial protein age.

    Science.gov (United States)

    Ferree, Andrew W; Trudeau, Kyle; Zik, Eden; Benador, Ilan Y; Twig, Gilad; Gottlieb, Roberta A; Shirihai, Orian S

    2013-11-01

    To study mitochondrial protein age dynamics, we targeted a time-sensitive fluorescent protein, MitoTimer, to the mitochondrial matrix. Mitochondrial age was revealed by the integrated portions of young (green) and old (red) MitoTimer protein. Mitochondrial protein age was dependent on turnover rates as pulsed synthesis, decreased import, or autophagic inhibition all increased the proportion of aged MitoTimer protein. Mitochondrial fusion promotes the distribution of young mitochondrial protein across the mitochondrial network as cells lacking essential fusion genes Mfn1 and Mfn2 displayed increased heterogeneity in mitochondrial protein age. Experiments in hippocampal neurons illustrate that the distribution of older and younger mitochondrial protein within the cell is determined by subcellular spatial organization and compartmentalization of mitochondria into neurites and soma. This effect was altered by overexpression of mitochondrial transport protein, RHOT1/MIRO1. Collectively our data show that distribution of young and old protein in the mitochondrial network is dependent on turnover, fusion, and transport.

  7. Axon injury triggers EFA-6 mediated destabilization of axonal microtubules via TACC and doublecortin like kinase.

    Science.gov (United States)

    Chen, Lizhen; Chuang, Marian; Koorman, Thijs; Boxem, Mike; Jin, Yishi; Chisholm, Andrew D

    2015-09-04

    Axon injury triggers a series of changes in the axonal cytoskeleton that are prerequisites for effective axon regeneration. In Caenorhabditis elegans the signaling protein Exchange Factor for ARF-6 (EFA-6) is a potent intrinsic inhibitor of axon regrowth. Here we show that axon injury triggers rapid EFA-6-dependent inhibition of axonal microtubule (MT) dynamics, concomitant with relocalization of EFA-6. EFA-6 relocalization and axon regrowth inhibition require a conserved 18-aa motif in its otherwise intrinsically disordered N-terminal domain. The EFA-6 N-terminus binds the MT-associated proteins TAC-1/Transforming-Acidic-Coiled-Coil, and ZYG-8/Doublecortin-Like-Kinase, both of which are required for regenerative growth cone formation, and which act downstream of EFA-6. After injury TAC-1 and EFA-6 transiently relocalize to sites marked by the MT minus end binding protein PTRN-1/Patronin. We propose that EFA-6 acts as a bifunctional injury-responsive regulator of axonal MT dynamics, acting at the cell cortex in the steady state and at MT minus ends after injury.

  8. The effect of mitochondrial calcium uniporter on mitochondrial fission in hippocampus cells ischemia/reperfusion injury.

    Science.gov (United States)

    Zhao, Lantao; Li, Shuhong; Wang, Shilei; Yu, Ning; Liu, Jia

    2015-06-01

    The mitochondrial calcium uniporter (MCU) transports free Ca(2+) into the mitochondrial matrix, maintaining Ca(2+) homeostasis, thus regulates the mitochondrial morphology. Previous studies have indicated that there was closely crosstalk between MCU and mitochondrial fission during the process of ischemia/reperfusion injury. This study constructed a hypoxia reoxygenation model using primary hippocampus neurons to mimic the cerebral ischemia/reperfusion injury and aims to explore the exactly effect of MCU on the mitochondrial fission during the process of ischemia/reperfusion injury and so as the mechanisms. Our results found that the inhibitor of the MCU, Ru360, decreased mitochondrial Ca(2+) concentration, suppressed the expression of mitochondrial fission protein Drp1, MIEF1 and Fis1, and thus improved mitochondrial morphology significantly. Whereas spermine, the agonist of the MCU, had no significant impact compared to the I/R group. This study demonstrated that the MCU regulates the process of mitochondrial fission by controlling the Ca(2+) transport, directly upregulating mitochondrial fission proteins Drp1, Fis1 and indirectly reversing the MIEF1-induced mitochondrial fusion. It also provides new targets for brain protection during ischemia/reperfusion injury.

  9. Mitochondrial Myopathy

    Science.gov (United States)

    ... diseases are caused by CoQ10 deficiency, and CoQ10 supplementation is clearly beneficial in these cases. It might provide some relief from other mitochondrial diseases. Creatine, L-carnitine, and CoQ10 supplements often are combined into a “ ...

  10. Mitochondrial dysfunctions in neurodegenerative diseases: relevance to Alzheimer's disease.

    Science.gov (United States)

    Hroudová, Jana; Singh, Namrata; Fišar, Zdeněk

    2014-01-01

    Mitochondrial dysfunctions are supposed to be responsible for many neurodegenerative diseases dominating in Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). A growing body of evidence suggests that defects in mitochondrial metabolism and particularly of electron transport chain may play a role in pathogenesis of AD. Structurally and functionally damaged mitochondria do not produce sufficient ATP and are more prominent in producing proapoptotic factors and reactive oxygen species (ROS), and this can be an early stage of several mitochondrial disorders, including neurodegenerative diseases. Mitochondrial dysfunctions may be caused by both mutations in mitochondrial or nuclear DNA that code mitochondrial components and by environmental causes. In the following review, common aspects of mitochondrial impairment concerned about neurodegenerative diseases are summarized including ROS production, impaired mitochondrial dynamics, and apoptosis. Also, damaged function of electron transport chain complexes and interactions between pathological proteins and mitochondria are described for AD particularly and marginally for PD and HD.

  11. How Schwann Cells Sort Axons: New Concepts.

    Science.gov (United States)

    Feltri, M Laura; Poitelon, Yannick; Previtali, Stefano Carlo

    2016-06-01

    Peripheral nerves contain large myelinated and small unmyelinated (Remak) fibers that perform different functions. The choice to myelinate or not is dictated to Schwann cells by the axon itself, based on the amount of neuregulin I-type III exposed on its membrane. Peripheral axons are more important in determining the final myelination fate than central axons, and the implications for this difference in Schwann cells and oligodendrocytes are discussed. Interestingly, this choice is reversible during pathology, accounting for the remarkable plasticity of Schwann cells, and contributing to the regenerative potential of the peripheral nervous system. Radial sorting is the process by which Schwann cells choose larger axons to myelinate during development. This crucial morphogenetic step is a prerequisite for myelination and for differentiation of Remak fibers, and is arrested in human diseases due to mutations in genes coding for extracellular matrix and linkage molecules. In this review we will summarize progresses made in the last years by a flurry of reverse genetic experiments in mice and fish. This work revealed novel molecules that control radial sorting, and contributed unexpected ideas to our understanding of the cellular and molecular mechanisms that control radial sorting of axons.

  12. Three-dimensional structure of axonal mitochondria reflects the age of drosophila

    Institute of Scientific and Technical Information of China (English)

    Honglian Zhu; Xiaojiang Sun

    2013-01-01

    This study aimed to reconstruct a three-dimensional map of axonal mitochondria using Fiji and Neurolucida software, and to observe directly the morphology and distribution of mitochondria in axons of motor neurons in dorsal longitudinal flight muscles of drosophila aged 5 days and 20 days, using electron microscopy. Results indicated that there was no difference in the total area and volume of mitochondria between 5-day-old drosophila and 20-day-old drosophila in all sections, but the ratio of mitochondrial total areas to axon total areas, as well as mitochondrial density of 20-day-old drosophila, was lower than that of 5-day-old drosophila. The number of mitochondria, whose volume was less than 1 000 000 μm3, and between 1 000 000 μm3 and 10 000 000 μm3, was higher in 20-day-old drosophila than that in 5-day-old drosophila. The number of mitochondria with a volume between 1 000 000 μm3 and 100 000 000 μm3 was apparently higher than those with a volume less than 1 000 000 μm3 or larger than 100 000 000 μm3. In addition, the number of mitochondria with a volume more than 100 000 000 μm3 was small; however, the volume was nearly 70% of the total volume in both 5-day-old and 20-day-old drosophila. In contrast, the number of mitochondria with a volume between 1 000 000 μm3 and 10 000 000 μm3 was large, but the volume was less than 30% of the total volume. These experimental findings suggest that changes in mitochondrial morphology and number in motor neurons from the dorsal longitudinal muscle of drosophila are present during different ages.

  13. Imaging axonal degeneration and repair in pre-clinical animal models of multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Soumya S Yandamuri

    2016-05-01

    Full Text Available Multiple sclerosis (MS is a central nervous system (CNS disease characterized by chronic neuroinflammation, demyelination, and axonal damage. Infiltration of activated lymphocytes and myeloid cells are thought to be primarily responsible for white matter damage and axonopathy. Over time, this neurologic damage manifests clinically as debilitating motor and cognitive symptoms. Existing MS therapies focus on symptom relief and delay of disease progression through reduction of neuroinflammation. However, long-term strategies to remyelinate, protect, or regenerate axons have remained elusive, posing a challenge to treating progressive forms of MS. Preclinical mouse models and techniques such as immunohistochemistry, flow cytometry, and genomic and proteomic analysis have provided advances in our understanding of discrete time-points of pathology following disease induction. More recently, in vivo and in situ two-photon microscopy (2P has made it possible to visualize continuous real-time cellular behavior and structural changes occurring within the CNS during neuropathology. Research utilizing 2P imaging to study axonopathy in neuroinflammatory demyelinating disease has focused on five areas: (1 axonal morphologic changes (2 organelle transport and health, (3 relationship to inflammation, (4 neuronal excitotoxicity, and (5 regenerative therapies. 2P imaging may also be used to identify novel therapeutic targets via identification and clarification of dynamic cellular and molecular mechanisms of axonal regeneration and remyelination. Here, we review tools that have made 2P accessible for imaging neuropathologies and advances in our understanding of axonal degeneration and repair in preclinical models of demyelinating diseases.

  14. ATP7A (Menkes protein) functions in axonal targeting and synaptogenesis.

    Science.gov (United States)

    El Meskini, Rajaâ; Crabtree, Kelli L; Cline, Laura B; Mains, Richard E; Eipper, Betty A; Ronnett, Gabriele V

    2007-03-01

    Menkes disease (MD) is a neurodegenerative disorder caused by mutations in the copper transporter, ATP7A, a P-type ATPase. We previously used the olfactory system to demonstrate that ATP7A expression is developmentally, not constitutive, regulated, peaking during synaptogenesis when it is highly expressed in extending axons in a copper-independent manner. Although not known to be associated with axonal functions, we explored the possibility that the inability of mutant ATP7A to support axon outgrowth contributes to the neurodegeneration seen in MD. In vivo analysis of the olfactory system in mottled brindled (Atp7aMobr) mice, a rodent model for MD, demonstrates that ATP7A deficiency affects olfactory sensory neuron (OSN) maturation. Disrupted OSN axonal projections and mitral/tufted cell dendritic growth lead to altered synapse integrity and glomerular disorganization in the olfactory bulbs of Atp7aMobr mice. Our data indicate that the neuronal abnormalities observed in MD are a result of specific age-dependent developmental defects. This study demonstrates a role for ATP7A and/or copper in axon outgrowth and synaptogenesis, and will further help identify the cause of the neuropathology that characterizes MD.

  15. Role of mitochondrial calcium uniporter in regulating mitochondrial fission in the cerebral cortexes of living rats.

    Science.gov (United States)

    Liang, Nan; Wang, Peng; Wang, Shilei; Li, Shuhong; Li, Yu; Wang, Jinying; Wang, Min

    2014-06-01

    The mitochondrial calcium uniporter (MCU) transports Ca2+ from the cytoplasm to the mitochondrial matrix and thus maintains Ca2+ homeostasis. Previous studies have reported that inhibition of MCU by ruthenium red (RR) protects the brain from ischemia/reperfusion (I/R) injury and that mitochondrial fission plays an important role in I/R injury. However, it is still not known whether MCU affects mitochondrial fission. In the present study, treatment with RR was found to decrease the concentration of free calcium in the mitochondria, calcineurin enzyme activity and dynamin-related protein 1 expression, and treatment with spermine was found to have the opposite effect in organisms subjected to occlusion of the middle cerebral artery lasting 2 h followed by 24 h reperfusion. These results indicate that MCU may be related to mitochondrial fission via modulating mitochondrial Ca2+ uptake and this relationship between MCU and mitochondrial fission may protect the brain from I/R injury.

  16. Automated Axon Counting in Rodent Optic Nerve Sections with AxonJ

    Science.gov (United States)

    Zarei, Kasra; Scheetz, Todd E.; Christopher, Mark; Miller, Kathy; Hedberg-Buenz, Adam; Tandon, Anamika; Anderson, Michael G.; Fingert, John H.; Abràmoff, Michael David

    2016-05-01

    We have developed a publicly available tool, AxonJ, which quantifies the axons in optic nerve sections of rodents stained with paraphenylenediamine (PPD). In this study, we compare AxonJ’s performance to human experts on 100x and 40x images of optic nerve sections obtained from multiple strains of mice, including mice with defects relevant to glaucoma. AxonJ produced reliable axon counts with high sensitivity of 0.959 and high precision of 0.907, high repeatability of 0.95 when compared to a gold-standard of manual assessments and high correlation of 0.882 to the glaucoma damage staging of a previously published dataset. AxonJ allows analyses that are quantitative, consistent, fully-automated, parameter-free, and rapid on whole optic nerve sections at 40x. As a freely available ImageJ plugin that requires no highly specialized equipment to utilize, AxonJ represents a powerful new community resource augmenting studies of the optic nerve using mice.

  17. Diverse modes of axon elaboration in the developing neocortex.

    Directory of Open Access Journals (Sweden)

    2005-08-01

    Full Text Available The development of axonal arbors is a critical step in the establishment of precise neural circuits, but relatively little is known about the mechanisms of axonal elaboration in the neocortex. We used in vivo two-photon time-lapse microscopy to image axons in the neocortex of green fluorescent protein-transgenic mice over the first 3 wk of postnatal development. This period spans the elaboration of thalamocortical (TC and Cajal-Retzius (CR axons and cortical synaptogenesis. Layer 1 collaterals of TC and CR axons were imaged repeatedly over time scales ranging from minutes up to days, and their growth and pruning were analyzed. The structure and dynamics of TC and CR axons differed profoundly. Branches of TC axons terminated in small, bulbous growth cones, while CR axon branch tips had large growth cones with numerous long filopodia. TC axons grew rapidly in straight paths, with frequent interstitial branch additions, while CR axons grew more slowly along tortuous paths. For both types of axon, new branches appeared at interstitial sites along the axon shaft and did not involve growth cone splitting. Pruning occurred via retraction of small axon branches (tens of microns, at both CR and TC axons or degeneration of large portions of the arbor (hundreds of microns, for TC axons only. The balance between growth and retraction favored overall growth, but only by a slight margin. Given the identical layer 1 territory upon which CR and TC axons grow, the differences in their structure and dynamics likely reflect distinct intrinsic growth programs for axons of long projection neurons versus local interneurons.

  18. Neural Progenitor Cells Promote Axonal Growth and Alter Axonal mRNA Localization in Adult Neurons

    Science.gov (United States)

    Merianda, Tanuja T.; Jin, Ying

    2017-01-01

    Abstract The inhibitory environment of the spinal cord and the intrinsic properties of neurons prevent regeneration of axons following CNS injury. However, both ascending and descending axons of the injured spinal cord have been shown to regenerate into grafts of embryonic neural progenitor cells (NPCs). Previous studies have shown that grafts composed of glial-restricted progenitors (GRPs) and neural-restricted progenitors (NRPs) can provide a permissive microenvironment for axon growth. We have used cocultures of adult rat dorsal root ganglion (DRG) neurons together with NPCs, which have shown significant enhancement of axon growth by embryonic rat GRP and GRPs/NRPs, both in coculture conditions and when DRGs are exposed to conditioned medium from the NPC cultures. This growth-promoting effect of NPC-conditioned medium was also seen in injury-conditioned neurons. DRGs cocultured with GRPs/NRPs showed altered expression of regeneration-associated genes at transcriptional and post-transcriptional levels. We found that levels of GAP-43 mRNA increased in DRG cell bodies and axons. However, hepcidin antimicrobial peptide (HAMP) mRNA decreased in the cell bodies of DRGs cocultured with GRPs/NRPs, which is distinct from the increase in cell body HAMP mRNA levels seen in DRGs after injury conditioning. Endogenous GAP-43 and β-actin mRNAs as well as reporter RNAs carrying axonally localizing 3'UTRs of these transcripts showed significantly increased levels in distal axons in the DRGs cocultured with GRPs/NRPs. These results indicate that axon growth promoted by NPCs is associated not only with enhanced transcription of growth-associated genes but also can increase localization of some mRNAs into growing axons. PMID:28197547

  19. Myelin-associated glycoprotein and its axonal receptors.

    Science.gov (United States)

    Schnaar, Ronald L; Lopez, Pablo H H

    2009-11-15

    Myelin-associated glycoprotein (MAG) is expressed on the innermost myelin membrane wrap, directly apposed to the axon surface. Although it is not required for myelination, MAG enhances long-term axon-myelin stability, helps to structure nodes of Ranvier, and regulates the axon cytoskeleton. In addition to its role in axon-myelin stabilization, MAG inhibits axon regeneration after injury; MAG and a discrete set of other molecules on residual myelin membranes at injury sites actively signal axons to halt elongation. Both the stabilizing and the axon outgrowth inhibitory effects of MAG are mediated by complementary MAG receptors on the axon surface. Two MAG receptor families have been described, sialoglycans (specifically gangliosides GD1a and GT1b) and Nogo receptors (NgRs). Controversies remain about which receptor(s) mediates which of MAG's biological effects. Here we review the findings and challenges in associating MAG's biological effects with specific receptors.

  20. Dopaminergic and glutamatergic microdomains in a subset of rodent mesoaccumbens axons.

    Science.gov (United States)

    Zhang, Shiliang; Qi, Jia; Li, Xueping; Wang, Hui-Ling; Britt, Jonathan P; Hoffman, Alexander F; Bonci, Antonello; Lupica, Carl R; Morales, Marisela

    2015-03-01

    Mesoaccumbens fibers are thought to co-release dopamine and glutamate. However, the mechanism is unclear, and co-release by mesoaccumbens fibers has not been documented. Using electron microcopy, we found that some mesoaccumbens fibers have vesicular transporters for dopamine (VMAT2) in axon segments that are continuous with axon terminals that lack VMAT2, but contain vesicular glutamate transporters type 2 (VGluT2). In vivo overexpression of VMAT2 did not change the segregation of the two vesicular types, suggesting the existence of highly regulated mechanisms for maintaining this segregation. The mesoaccumbens axon terminals containing VGluT2 vesicles make asymmetric synapses, commonly associated with excitatory signaling. Using optogenetics, we found that dopamine and glutamate were released from the same mesoaccumbens fibers. These findings reveal a complex type of signaling by mesoaccumbens fibers in which dopamine and glutamate can be released from the same axons, but are not normally released at the same site or from the same synaptic vesicles.

  1. A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones

    Science.gov (United States)

    Siebert, Matthias; Böhme, Mathias A; Driller, Jan H; Babikir, Husam; Mampell, Malou M; Rey, Ulises; Ramesh, Niraja; Matkovic, Tanja; Holton, Nicole; Reddy-Alla, Suneel; Göttfert, Fabian; Kamin, Dirk; Quentin, Christine; Klinedinst, Susan; Andlauer, Till FM; Hell, Stefan W; Collins, Catherine A; Wahl, Markus C; Loll, Bernhard; Sigrist, Stephan J

    2015-01-01

    Synaptic vesicles (SVs) fuse at active zones (AZs) covered by a protein scaffold, at Drosophila synapses comprised of ELKS family member Bruchpilot (BRP) and RIM-binding protein (RBP). We here demonstrate axonal co-transport of BRP and RBP using intravital live imaging, with both proteins co-accumulating in axonal aggregates of several transport mutants. RBP, via its C-terminal Src-homology 3 (SH3) domains, binds Aplip1/JIP1, a transport adaptor involved in kinesin-dependent SV transport. We show in atomic detail that RBP C-terminal SH3 domains bind a proline-rich (PxxP) motif of Aplip1/JIP1 with submicromolar affinity. Pointmutating this PxxP motif provoked formation of ectopic AZ-like structures at axonal membranes. Direct interactions between AZ proteins and transport adaptors seem to provide complex avidity and shield synaptic interaction surfaces of pre-assembled scaffold protein transport complexes, thus, favouring physiological synaptic AZ assembly over premature assembly at axonal membranes. DOI: http://dx.doi.org/10.7554/eLife.06935.001 PMID:26274777

  2. Modeling molecular mechanisms in the axon

    Science.gov (United States)

    de Rooij, R.; Miller, K. E.; Kuhl, E.

    2017-03-01

    Axons are living systems that display highly dynamic changes in stiffness, viscosity, and internal stress. However, the mechanistic origin of these phenomenological properties remains elusive. Here we establish a computational mechanics model that interprets cellular-level characteristics as emergent properties from molecular-level events. We create an axon model of discrete microtubules, which are connected to neighboring microtubules via discrete crosslinking mechanisms that obey a set of simple rules. We explore two types of mechanisms: passive and active crosslinking. Our passive and active simulations suggest that the stiffness and viscosity of the axon increase linearly with the crosslink density, and that both are highly sensitive to the crosslink detachment and reattachment times. Our model explains how active crosslinking with dynein motors generates internal stresses and actively drives axon elongation. We anticipate that our model will allow us to probe a wide variety of molecular phenomena—both in isolation and in interaction—to explore emergent cellular-level features under physiological and pathological conditions.

  3. A Microfluidics Approach to Investigate Axon Guidance

    Science.gov (United States)

    2007-03-26

    coat the substrate with PLL. The cells of one dissociated embryonic spinal cord was re-suspended in 3 µl of freshly-prepared Modified Frog Ringer’s...Surround repulsion of spinal sensory axons in higher vertebrate embryos . Neuron 18, 889-897 (1997). 8. Colamarino, S. & Tessier-Lavigne, M. The

  4. Speciifc effects of c-Jun NH2-terminal kinase-interacting protein 1 in neuronal axons

    Institute of Scientific and Technical Information of China (English)

    Shu Tang; Qiang Wen; Xiao-jian Zhang; Quan-cheng Kan

    2016-01-01

    c-Jun NH2-terminal kinase (JNK)-interacting protein 3 plays an important role in brain-derived neurotrophic factor/tropomyosin-related kinase B (TrkB) anterograde axonal transport. It remains unclear whether JNK-interacting protein 1 mediates similar effects, or whether JNK-interacting protein 1 affects the regulation of TrkB anterograde axonal transport. In this study, we isolated rat embryonic hippocampus and cultured hippocampal neuronsin vitro. Coimmunoprecipitation results demonstrated that JNK-interacting protein 1 formed TrkB com-plexesin vitro andin vivo. Immunocytochemistry results showed that when JNK-interacting protein 1 was highly expressed, the distribution of TrkB gradually increased in axon terminals. However, the distribution of TrkB reduced in axon terminals after knocking out JNK-interact-ing protein 1. In addition, there were differences in distribution of TrkB after JNK-interacting protein 1 was knocked out compared with not. However, knockout of JNK-interacting protein 1 did not affect the distribution of TrkB in dendrites. These ifndings conifrm that JNK-inter-acting protein 1 can interact with TrkB in neuronal cells, and can regulate the transport of TrkB in axons, but not in dendrites.

  5. Disruption of mitochondrial function in interpopulation hybrids of Tigriopus californicus.

    Science.gov (United States)

    Ellison, Christopher K; Burton, Ronald S

    2006-07-01

    Electron transport system (ETS) function in mitochondria is essential for the aerobic production of energy. Because ETS function requires extensive interactions between mitochondrial and nuclear gene products, coadaptation between mitochondrial and nuclear genomes may evolve within populations. Hybridization between allopatric populations may then expose functional incompatibilities between genomes that have not coevolved. The intertidal copepod Tigriopus californicus has high levels of nucleotide divergence among populations at mitochondrial loci and suffers F2 hybrid breakdown in interpopulation hybrids. We hypothesize that hybridization results in incompatibilities among subunits in ETS enzyme complexes and that these incompatibilities result in diminished mitochondrial function and fitness. To test this hypothesis, we measured fitness, mitochondrial function, and ETS enzyme activity in inbred recombinant hybrid lines of Tigriopus californicus. We found that (1) both fitness and mitochondrial function are reduced in hybrid lines, (2) only those ETS enzymes with both nuclear and mitochondrial subunits show a loss of activity in hybrid lines, and (3) positive relationships exist between ETS enzyme activity and mitochondrial function and between mitochondrial function and fitness. We also present evidence that hybrid lines harboring mitochondrial DNA (mtDNA) and mitochondrial RNA polymerase (mtRPOL) from the same parental source population have higher fitness than those with mtDNA and mtRPOL from different populations, suggesting that mitochondrial gene regulation may play a role in disruption of mitochondrial performance and fitness of hybrids. These results suggest that disruption of coadaptation between nuclear and mitochondrial genes contributes to the phenomenon of hybrid breakdown.

  6. Mechanisms of axon degeneration: from development to disease.

    Science.gov (United States)

    Saxena, Smita; Caroni, Pico

    2007-10-01

    Axon degeneration is an active, tightly controlled and versatile process of axon segment self-destruction. Although not involving cell death, it resembles apoptosis in its logics. It involves three distinct steps: induction of competence in specific neurons, triggering of degeneration at defined axon segments of competent neurons, and rapid fragmentation and removal of the segments. The mechanisms that initiate degeneration are specific to individual settings, but the final pathway of pruning is shared; it involves microtubule disassembly, axon swellings, axon fragmentation, and removal of the remnants by locally recruited phagocytes. The tight regulatory properties of axon degeneration distinguish it from passive loss phenomena, and confer significance to processes that involve it. Axon degeneration has prominent roles in development, upon lesions and in disease. In development, it couples the progressive specification of neurons and circuits to the removal of defined axon branches. Competence might involve transcriptional switches, and local triggering can involve axon guidance molecules and synaptic activity patterns. Lesion-induced Wallerian degeneration is inhibited in the presence of Wld(S) fusion protein in neurons; it involves early local, and later, distal degeneration. It has recently become clear that like in other settings, axon degeneration in disease is a rapid and specific process, which should not be confused with a variety of disease-related pathologies. Elucidating the specific mechanisms that initiate axon degeneration should open up new avenues to investigate principles of circuit assembly and plasticity, to uncover mechanisms of disease progression, and to identify ways of protecting synapses and axons in disease.

  7. Morphometry of Axons in Optic Nerves of Siamese's Twins

    Institute of Scientific and Technical Information of China (English)

    Xinzu Gu; Zhenping Zhang; Qi Lin; Jiongji Liang; Wenyu Lu; Xiulan Ye; A A Sadun

    2002-01-01

    Purpose: To observe the development of optic nerve, we examined four optic nerves from Siameses Twins by absolute counts of axons.Methods: Mean axon diameter, mean axon density, totally axonal population and optic nerve area were noted for each optic nerve. The mean axon diameter and the mean axon density were compared between paraxial (inner sectors)and cortical (outer sectors)areas of the nerves.Results: More myelinated axons were seen in the inner sectors as compared to the outer sectors(average 11 axons/1 000 μm2 in inner sectors and 34 axons/l 000 μm2 in outer sectors( P=0. 036) . The myelinated fibers were also smaller(63 microns) in the outer sectors as compared to the inner sectors(72 microns) ( P = 0. 001 ). The average cross sectors area for the four 40 week stage optical nerves of Siamese Twins was 3.32 × 103 as compared to 1 million axons for 32-week-old normals.Conclusion: Our finding of fewer axonal number and small myelinated fibers in the Siamese Twins suggests hypoplasia. Myelination was more abnormal in the paraxial optic nerve than that in the peripheral sectors, suggesting anomalous development of optic nerve peripherally and delayed developnent centrally. Axonal density is higher in inner sectors than that in outer sectors, suggesting delayed development of the outer nerve sector.

  8. What Is Mitochondrial DNA?

    Science.gov (United States)

    ... DNA What is mitochondrial DNA? What is mitochondrial DNA? Although most DNA is packaged in chromosomes within ... proteins. For more information about mitochondria and mitochondrial DNA: Molecular Expressions, a web site from the Florida ...

  9. MAPK signaling promotes axonal degeneration by speeding the turnover of the axonal maintenance factor NMNAT2

    Science.gov (United States)

    Walker, Lauren J; Summers, Daniel W; Sasaki, Yo; Brace, EJ; Milbrandt, Jeffrey; DiAntonio, Aaron

    2017-01-01

    Injury-induced (Wallerian) axonal degeneration is regulated via the opposing actions of pro-degenerative factors such as SARM1 and a MAPK signal and pro-survival factors, the most important of which is the NAD+ biosynthetic enzyme NMNAT2 that inhibits activation of the SARM1 pathway. Here we investigate the mechanism by which MAPK signaling facilitates axonal degeneration. We show that MAPK signaling promotes the turnover of the axonal survival factor NMNAT2 in cultured mammalian neurons as well as the Drosophila ortholog dNMNAT in motoneurons. The increased levels of NMNAT2 are required for the axonal protection caused by loss of MAPK signaling. Regulation of NMNAT2 by MAPK signaling does not require SARM1, and so cannot be downstream of SARM1. Hence, pro-degenerative MAPK signaling functions upstream of SARM1 by limiting the levels of the essential axonal survival factor NMNAT2 to promote injury-dependent SARM1 activation. These findings are consistent with a linear molecular pathway for the axonal degeneration program. DOI: http://dx.doi.org/10.7554/eLife.22540.001 PMID:28095293

  10. Depletion of Mitofusin-2 Causes Mitochondrial Damage in Cisplatin-Induced Neuropathy.

    Science.gov (United States)

    Bobylev, Ilja; Joshi, Abhijeet R; Barham, Mohammed; Neiss, Wolfram F; Lehmann, Helmar C

    2017-01-21

    Sensory neuropathy is a relevant side effect of the antineoplastic agent cisplatin. Mitochondrial damage is assumed to play a critical role in cisplatin-induced peripheral neuropathy, but the pathomechanisms underlying cisplatin-induced mitotoxicity and neurodegeneration are incompletely understood. In an animal model of cisplatin-induced neuropathy, we determined in detail the extent and spatial distribution of mitochondrial damage during cisplatin treatment. Changes in the total number of axonal mitochondria during cisplatin treatment were assessed in intercostal nerves from transgenic mice that express cyan fluorescent protein. Further, we explored the impact of cisplatin on the expression of nuclear encoded molecules of mitochondrial fusion and fission, including mitofusin-2 (MFN2), optic atrophy 1 (OPA1), and dynamin-related protein 1 (DRP1). Cisplatin treatment resulted in a loss of total mitochondrial mass in axons and in an abnormal mitochondrial morphology including atypical enlargement, increased vacuolization, and loss of cristae. These changes were observed in distal and proximal nerve segments and were more prominent in axons than in Schwann cells. Transcripts of fusion and fission proteins were reduced in distal nerve segments. Significant reduced expression levels of the fusion protein MFN2 was detected in nerves of cisplatin-exposed animals. In summary, we provide for the first time an evidence that cisplatin alters mitochondrial dynamics in peripheral nerves. Loss of MFN2, previously implicated in the pathogenesis of other neurodegenerative diseases, also contributes to the pathogenesis in cisplatin-induced neuropathy.

  11. AxonQuant: A Microfluidic Chamber Culture-Coupled Algorithm That Allows High-Throughput Quantification of Axonal Damage

    Directory of Open Access Journals (Sweden)

    Yang Li

    2014-02-01

    Full Text Available Published methods for imaging and quantitatively analyzing morphological changes in neuronal axons have serious limitations because of their small sample sizes, and their time-consuming and nonobjective nature. Here we present an improved microfluidic chamber design suitable for fast and high-throughput imaging of neuronal axons. We developed the AxonQuant algorithm, which is suitable for automatic processing of axonal imaging data. This microfluidic chamber-coupled algorithm allows calculation of an ‘axonal continuity index' that quantitatively measures axonal health status in a manner independent of neuronal or axonal density. This method allows quantitative analysis of axonal morphology in an automatic and nonbiased manner. Our method will facilitate large-scale high-throughput screening for genes or therapeutic compounds for neurodegenerative diseases involving axonal damage. When combined with imaging technologies utilizing different gene markers, this method will provide new insights into the mechanistic basis for axon degeneration. Our microfluidic chamber culture-coupled AxonQuant algorithm will be widely useful for studying axonal biology and neurodegenerative disorders. © 2014 S. Karger AG, Basel

  12. Impaired mitochondrial oxidative phosphorylation in the peroxisomal disease X-linked adrenoleukodystrophy.

    Science.gov (United States)

    López-Erauskin, J; Galino, J; Ruiz, M; Cuezva, J M; Fabregat, I; Cacabelos, D; Boada, J; Martínez, J; Ferrer, I; Pamplona, R; Villarroya, F; Portero-Otín, M; Fourcade, S; Pujol, A

    2013-08-15

    X-linked adrenoleukodystrophy (X-ALD) is an inherited metabolic disorder of the nervous system characterized by axonopathy in spinal cords and/or cerebral demyelination, adrenal insufficiency and accumulation of very long-chain fatty acids (VLCFAs) in plasma and tissues. The disease is caused by malfunction of the ABCD1 gene, which encodes a peroxisomal transporter of VLCFAs or VLCFA-CoA. In the mouse, Abcd1 loss causes late onset axonal degeneration in the spinal cord, associated with locomotor disability resembling the most common phenotype in patients, adrenomyeloneuropathy. We have formerly shown that an excess of the VLCFA C26:0 induces oxidative damage, which underlies the axonal degeneration exhibited by the Abcd1(-) mice. In the present study, we sought to investigate the noxious effects of C26:0 on mitochondria function. Our data indicate that in X-ALD patients' fibroblasts, excess of C26:0 generates mtDNA oxidation and specifically impairs oxidative phosphorylation (OXPHOS) triggering mitochondrial ROS production from electron transport chain complexes. This correlates with impaired complex V phosphorylative activity, as visualized by high-resolution respirometry on spinal cord slices of Abcd1(-) mice. Further, we identified a marked oxidation of key OXPHOS system subunits in Abcd1(-) mouse spinal cords at presymptomatic stages. Altogether, our results illustrate some of the mechanistic intricacies by which the excess of a fatty acid targeted to peroxisomes activates a deleterious process of oxidative damage to mitochondria, leading to a multifaceted dysfunction of this organelle. These findings may be of relevance for patient management while unveiling novel therapeutic targets for X-ALD.

  13. Motor and dorsal root ganglion axons serve as choice points for the ipsilateral turning of dI3 axons.

    Science.gov (United States)

    Avraham, Oshri; Hadas, Yoav; Vald, Lilach; Hong, Seulgi; Song, Mi-Ryoung; Klar, Avihu

    2010-11-17

    The axons of the spinal intersegmental interneurons are projected longitudinally along various funiculi arrayed along the dorsal-ventral axis of the spinal cord. The roof plate and the floor plate have a profound role in patterning their initial axonal trajectory. However, other positional cues may guide the final architecture of interneuron tracks in the spinal cord. To gain more insight into the organization of specific axonal tracks in the spinal cord, we focused on the trajectory pattern of a genetically defined neuronal population, dI3 neurons, in the chick spinal cord. Exploitation of newly characterized enhancer elements allowed specific labeling of dI3 neurons and axons. dI3 axons are projected ipsilaterally along two longitudinal fascicules at the ventral lateral funiculus (VLF) and the dorsal funiculus (DF). dI3 axons change their trajectory plane from the transverse to the longitudinal axis at two novel checkpoints. The axons that elongate at the DF turn at the dorsal root entry zone, along the axons of the dorsal root ganglion (DRG) neurons, and the axons that elongate at the VLF turn along the axons of motor neurons. Loss and gain of function of the Lim-HD protein Isl1 demonstrate that Isl1 is not required for dI3 cell fate. However, Isl1 is sufficient to impose ipsilateral turning along the motor axons when expressed ectopically in the commissural dI1 neurons. The axonal patterning of dI3 neurons, revealed in this study, highlights the role of established axonal cues-the DRG and motor axons-as intermediate guidepost cues for dI3 axons.

  14. Axon Membrane Skeleton Structure is Optimized for Coordinated Sodium Propagation

    CERN Document Server

    Zhang, Yihao; Li, He; Tzingounis, Anastasios V; Lykotrafitis, George

    2016-01-01

    Axons transmit action potentials with high fidelity and minimal jitter. This unique capability is likely the result of the spatiotemporal arrangement of sodium channels along the axon. Super-resolution microscopy recently revealed that the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under entropic tension. Sodium channels also exhibit a periodic distribution pattern, as they bind to ankyrin G, which associates with spectrin. Here, we elucidate the relationship between the axon membrane skeleton structure and the function of the axon. By combining cytoskeletal dynamics and continuum diffusion modeling, we show that spectrin filaments under tension minimize the thermal fluctuations of sodium channels and prevent overlap of neighboring channel trajectories. Importantly, this axon skeletal arrangement allows for a highly reproducible band-like activation of sodium channels leading to coordinated sodium propagation along the axon.

  15. Motor axon synapses on renshaw cells contain higher levels of aspartate than glutamate.

    Directory of Open Access Journals (Sweden)

    Dannette S Richards

    Full Text Available Motoneuron synapses on spinal cord interneurons known as Renshaw cells activate nicotinic, AMPA and NMDA receptors consistent with co-release of acetylcholine and excitatory amino acids (EAA. However, whether these synapses express vesicular glutamate transporters (VGLUTs capable of accumulating glutamate into synaptic vesicles is controversial. An alternative possibility is that these synapses release other EAAs, like aspartate, not dependent on VGLUTs. To clarify the exact EAA concentrated at motor axon synapses we performed a quantitative postembedding colloidal gold immunoelectron analysis for aspartate and glutamate on motor axon synapses (identified by immunoreactivity to the vesicular acetylcholine transporter; VAChT contacting calbindin-immunoreactive (-IR Renshaw cell dendrites. The results show that 71% to 80% of motor axon synaptic boutons on Renshaw cells contained aspartate immunolabeling two standard deviations above average neuropil labeling. Moreover, VAChT-IR synapses on Renshaw cells contained, on average, aspartate immunolabeling at 2.5 to 2.8 times above the average neuropil level. In contrast, glutamate enrichment was lower; 21% to 44% of VAChT-IR synapses showed glutamate-IR two standard deviations above average neuropil labeling and average glutamate immunogold density was 1.7 to 2.0 times the neuropil level. The results were not influenced by antibody affinities because glutamate antibodies detected glutamate-enriched brain homogenates more efficiently than aspartate antibodies detecting aspartate-enriched brain homogenates. Furthermore, synaptic boutons with ultrastructural features of Type I excitatory synapses were always labeled by glutamate antibodies at higher density than motor axon synapses. We conclude that motor axon synapses co-express aspartate and glutamate, but aspartate is concentrated at higher levels than glutamate.

  16. Time-Dependent Progression of Demyelination and Axonal Pathology in MP4-Induced Experimental Autoimmune Encephalomyelitis.

    Directory of Open Access Journals (Sweden)

    Johanna Prinz

    Full Text Available Multiple sclerosis (MS is an autoimmune disease of the central nervous system (CNS characterized by inflammation, demyelination and axonal pathology. Myelin basic protein/proteolipid protein (MBP-PLP fusion protein MP4 is capable of inducing chronic experimental autoimmune encephalomyelitis (EAE in susceptible mouse strains mirroring diverse histopathological and immunological hallmarks of MS. Lack of human tissue underscores the importance of animal models to study the pathology of MS.Twenty-two female C57BL/6 (B6 mice were immunized with MP4 and the clinical development of experimental autoimmune encephalomyelitis (EAE was observed. Methylene blue-stained semi-thin and ultra-thin sections of the lumbar spinal cord were assessed at the peak of acute EAE, three months (chronic EAE and six months after onset of EAE (long-term EAE. The extent of lesional area and inflammation were analyzed in semi-thin sections on a light microscopic level. The magnitude of demyelination and axonal damage were determined using electron microscopy. Emphasis was put on the ventrolateral tract (VLT of the spinal cord.B6 mice demonstrated increasing demyelination and severe axonal pathology in the course of MP4-induced EAE. Additionally, mitochondrial swelling and a decrease in the nearest neighbor neurofilament distance (NNND as early signs of axonal damage were evident with the onset of EAE. In semi-thin sections we observed the maximum of lesional area in the chronic state of EAE while inflammation was found to a similar extent in acute and chronic EAE. In contrast to the well-established myelin oligodendrocyte glycoprotein (MOG model, disease stages of MP4-induced EAE could not be distinguished by assessing the extent of parenchymal edema or the grade of inflammation.Our results complement our previous ultrastructural studies of B6 EAE models and suggest that B6 mice immunized with different antigens constitute useful instruments to study the diverse

  17. Characterization of Axo-Axonic Synapses in the Piriform Cortex of Mus musculus

    OpenAIRE

    Wang, Xinjun; Sun, Qian-Quan

    2012-01-01

    Previous anatomical and physiological studies have established major glutamatergic and GABAergic neuronal subtypes within the piriform cortical circuits. However, quantitative information regarding axo-axonic inhibitory synapses mediated by chandelier cells across major cortical subdivisions of piriform cortex is lacking. Therefore, we examined the properties of these synapses across the entire piriform cortex. Our results show the following. 1) γ-Aminobutyric acid membrane transporter 1-posi...

  18. Axonal BACE1 dynamics and targeting in hippocampal neurons: a role for Rab11 GTPase

    OpenAIRE

    Buggia-Prévot, Virginie; Fernandez, Celia G; Riordan, Sean; Vetrivel, Kulandaivelu S.; Roseman, Jelita; Waters, Jack; Bindokas, Vytautas P.; Vassar, Robert; Thinakaran, Gopal

    2014-01-01

    Background BACE1 is one of the two enzymes that cleave amyloid precursor protein to generate Alzheimer's disease (AD) beta amyloid peptides. It is widely believed that BACE1 initiates APP processing in endosomes, and in the brain this cleavage is known to occur during axonal transport of APP. In addition, BACE1 accumulates in dystrophic neurites surrounding brain senile plaques in individuals with AD, suggesting that abnormal accumulation of BACE1 at presynaptic terminals contributes to patho...

  19. Schwann cells-axon interaction in myelination.

    Science.gov (United States)

    Taveggia, Carla

    2016-08-01

    The remarkable interaction between glial cells and axons is crucial for nervous system development and homeostasis. Alterations in this continuous communication can cause severe pathologies that can compromise the integrity of the nervous system. The most dramatic consequence of this interaction is the generation of the myelin sheath, made by myelinating glial cells: Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system. In this review I will focus on signals coming from axons in the first part and then on those from Schwann cells that promote the formation and the maintenance of peripheral myelin. I will discuss their inter-relationship together with seminal and important advances recently made.

  20. Multifunctional Silk Nerve Guides for Axon Outgrowth

    Science.gov (United States)

    Tupaj, Marie C.

    Peripheral nerve regeneration is a critical issue as 2.8% of trauma patients present with this type of injury, estimating a total of 200,000 nerve repair procedures yearly in the United States. While the peripheral nervous system exhibits slow regeneration, at a rate of 0.5 mm -- 9 mm/day following trauma, this regenerative ability is only possible under certain conditions. Clinical repairs have changed slightly in the last 30 years and standard methods of treatment include suturing damaged nerve ends, allografting, and autografting, with the autograft the gold standard of these approaches. Unfortunately, the use of autografts requires a second surgery and there is a shortage of nerves available for grafting. Allografts are a second option however allografts have lower success rates and are accompanied by the need of immunosuppressant drugs. Recently there has been a focus on developing nerve guides as an "off the shelf" approach. Although some natural and synthetic guidance channels have been approved by the FDA, these nerve guides are unfunctionalized and repair only short gaps, less than 3 cm in length. The goal of this project was to identify strategies for functionalizing peripheral nerve conduits for the outgrowth of neuron axons in vitro . To accomplish this, two strategies (bioelectrical and biophysical) were indentified for increasing axon outgrowth and promoting axon guidance. Bioelectrical strategies exploited electrical stimulation for increasing neurite outgrowth. Biophysical strategies tested a range of surface topographies for axon guidance. Novel methods were developed for integrating electrical and biophysical strategies into silk films in 2D. Finally, a functionalized nerve conduit system was developed that integrated all strategies for the purpose of attaching, elongating, and guiding nervous tissue in vitro. Future directions of this work include silk conduit translation into a rat sciatic nerve model in vivo for the purpose of repairing long

  1. Interspecies variation in axon-myelin relationships.

    Science.gov (United States)

    Fraher, J P; O'Sullivan, A W

    2000-01-01

    The primary objective of this paper was to determine the extent and nature of interspecies differences in axon calibre and myelin sheath thickness and in the various relationships between these. Morphometric analysis of the axon perimeter-myelin sheath thickness relationship was performed on an equivalent nerve fibre population in a mammal, the rat, a bird, the chicken, an amphibian, the frog, a bony fish, the trout, and a cartilaginous fish, the dogfish. The abducent nerve was studied. It is especially suitable for this purpose because its fibres are closely similar in type and in peripheral distribution across the species studied. The relationship differed substantially between species. Differences were present in its setting, as described by the positions of the scatterplots, in the g ratio and in the regression and correlation data relating the parameters. Both parameters were markedly larger in the fish species than in all of the others. In addition, in rat, chicken, frog and trout, where large and small fibre classes could be differentiated clearly, the setting of the relationship between the two parameters was different for the two classes. In the main, variation in each of the parameters was greater between than within species. The larger fibres in the fish species were closely similar in axon perimeter and sheath thickness despite their long evolutionary separation. From this study and from others in the series, it may be concluded that there is no fixed or constant relationship between axon calibre and the thickness of the surrounding myelin sheath. Each nerve tends to have its own particular relationship and this differs between species.

  2. Mitochondrial DNA Alterations and Reduced Mitochondrial Function in Aging

    OpenAIRE

    Hebert, Sadie L.; Lanza, Ian R.; Nair, K. Sreekumaran

    2010-01-01

    Oxidative damage to mitochondrial DNA increases with aging. This damage has the potential to affect mitochondrial DNA replication and transcription which could alter the abundance or functionality of mitochondrial proteins. This review describes mitochondrial DNA alterations and changes in mitochondrial function that occur with aging. Age-related alterations in mitochondrial DNA as a possible contributor to the reduction in mitochondrial function are discussed.

  3. Retinoic acid signaling in axonal regeneration

    Directory of Open Access Journals (Sweden)

    Radhika ePuttagunta

    2012-01-01

    Full Text Available Following an acute central nervous system injury, axonal regeneration and functional recovery are extremely limited. This is due to an extrinsic inhibitory growth environment and the lack of intrinsic growth competence. Retinoic acid (RA signaling, essential in developmental dorsoventral patterning and specification of spinal motor neurons, has been shown through its receptor, the transcription factor RA receptor β2 (RARß2, to induce axonal regeneration following spinal cord injury (SCI. Recently, it has been shown that in dorsal root ganglia neurons, cAMP levels were greatly increased by lentiviral RARβ2 expression and contributed to neurite outgrowth. Moreover, RARβ agonists, in cerebellar granule neurons and in the brain in vivo, induced phosphoinositide 3-kinase dependent phosphorylation of AKT that was involved in RARβ-dependent neurite outgrowth. More recently, RA-RARß pathways were shown to directly transcriptionally repress a member of the inhibitory Nogo receptor complex, Lingo-1, under an axonal growth inhibitory environment in vitro as well as following spinal injury in vivo. This perspective focuses on these newly discovered molecular mechanisms and future directions in the field.

  4. MRI of the diffuse axonal injury

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Yang Gu; Woo, Young Hoon; Suh, Soo Jhi [Keimyung University School of Medicine, Daegu (Korea, Republic of)

    1992-01-15

    CT has facilitated early recognition and treatment of focal brain injuries in patients with head trauma. However, CT shows relatively low sensitivity in identifying non hemorrhage contusion and injuries of white matter. MR is known to be superior to CT in detection of white matter injuries, such as diffuse axonal injury. MR imaging in 14 cases of diffuse axonal injury on 2.0T was studied. The corpus callosum, especially the body portion, was the most commonly involved site. The lesions ranged from 5 to 20mm in size with ovoid to elliptical shape. T2WI was the most sensitive pulse sequence in detecting lesions such as white matter degeneration, hemorrhagic and non hemorrhagic contusion. The lesions were nonspecific as high and low signal intensities on T2WI and T1WI respectively. CT showed white matter abnormality in only 1 case of 14 cases. We propose MR imaging as the primary imaging procedure for the detection of diffuse axonal injury because of its multiplanar capabilities and higher sensitivity.

  5. Shh goes multidirectional in axon guidance

    Institute of Scientific and Technical Information of China (English)

    Paola Bovolenta; Luisa Sanchez-Arrones

    2012-01-01

    Shh and Wnts,secreted by the floor and roof plate of the spinal cord,direct longitudinal growth of the axons from the adjacent ventral funiculus and cortico-spinal tract.Whether these midline cues influencethe directionality of axons elongating in more lateral positions of the spinal cord is unexplored.Song and colleagues investigate this possibility and demonstrate that the location of descending raphe-spinal tract in the ventrolateral spinal cord is dictated by the simultaneous repellent activity of Shh gradients in both the anteriorto-posterior (A-P) and medial-tolateral (M-L) axis. The spinal cord is the main pathway for exchange of information between the brain and the rest of the body.Sensory information collected in the body periphery is conveyed to the brain by axonal tracts that ascend along the spinal cord whereas motor information travels from the brain to the periphery in descending tracts.Precise spatial organization of these fiber tracts is thus essential for animal behavior and survival.

  6. Axon-glial relations during regeneration of axons in the adult rat anterior medullary velum.

    Science.gov (United States)

    Berry, M; Hunter, A S; Duncan, A; Lordan, J; Kirvell, S; Tsang, W L; Butt, A M

    1998-12-01

    The anterior medullary velum (AMV) of adult Wistar rats was lesioned in the midsagittal plane, transecting all decussating axons including those of the central projection of the IVth nerve. At selected times up to 200 days after transection, the degenerative and regenerative responses of axons and glia were analyzed using transmission and scanning electron microscopy and immunohistochemistry. In particular, both the capacity of oligodendrocytes to remyelinate regenerated fibers and the stability of the CNS/PNS junctional zone of the IVth nerve rootlet were documented. Transected central AMV axons exhibited four patterns of fiber regeneration in which fibers grew: rostrocaudally in the reactive paralesion neuropil (Group 1); randomly within the AMV (Group 2); into the ipsilateral IVth nerve rootlet, after turning at the lesion edge and growing recurrently through the old degenerated contralateral central trochlear nerve trajectory (Group 3); and ectopically through paralesion tears in the ependyma onto the surface of the IVth ventricle (Group 4). Group 1-3 axons regenerated unperturbed through degenerating central myelin, reactive astrocytes, oligodendrocytes, microglia, and large accumulations of hematogenous macrophages. Only Group 3 axons survived long term in significant numbers, and all became myelinated by oligodendrocytes, ultimately establishing thin sheaths with relatively normal nodal gaps and intersegmental myelin sheath lengths. Schwann cells at the CNS/PNS junction of the IVth nerve rootlet did not invade the CNS, but astrocyte processes grew across the junction into the PNS portion of the IVth nerve. The basal lamina of the junctional glia limitans remained stable throughout the experimental period.

  7. Peripheral neuropathy associated with mitochondrial disease in children.

    Science.gov (United States)

    Menezes, Manoj P; Ouvrier, Robert A

    2012-05-01

    Mitochondrial diseases in children are often associated with a peripheral neuropathy but the presence of the neuropathy is under-recognized because of the overwhelming involvement of the central nervous system (CNS). These mitochondrial neuropathies are heterogeneous in their clinical, neurophysiological, and histopathological characteristics. In this article, we provide a comprehensive review of childhood mitochondrial neuropathy. Early recognition of neuropathy may help with the identification of the mitochondrial syndrome. While it is not definite that the characteristics of the neuropathy would help in directing genetic testing without the requirement for invasive skin, muscle or liver biopsies, there appears to be some evidence for this hypothesis in Leigh syndrome, in which nuclear SURF1 mutations cause a demyelinating neuropathy and mitochondrial DNA MTATP6 mutations cause an axonal neuropathy. POLG1 mutations, especially when associated with late-onset phenotypes, appear to cause a predominantly sensory neuropathy with prominent ataxia. The identification of the peripheral neuropathy also helps to target genetic testing in the mitochondrial optic neuropathies. Although often subclinical, the peripheral neuropathy may occasionally be symptomatic and cause significant disability. Where it is symptomatic, recognition of the neuropathy will help the early institution of rehabilitative therapy. We therefore suggest that nerve conduction studies should be a part of the early evaluation of children with suspected mitochondrial disease.

  8. DGAT2 Mutation in a Family with Autosomal-Dominant Early-Onset Axonal Charcot-Marie-Tooth Disease.

    Science.gov (United States)

    Hong, Young Bin; Kang, Junghee; Kim, Ji Hyun; Lee, Jinho; Kwak, Geon; Hyun, Young Se; Nam, Soo Hyun; Hong, Hyun Dae; Choi, Yu-Ri; Jung, Sung-Chul; Koo, Heasoo; Lee, Ji Eun; Choi, Byung-Ok; Chung, Ki Wha

    2016-05-01

    Charcot-Marie-Tooth disease (CMT) is the most common inherited peripheral neuropathy and is a genetically and clinically heterogeneous disorder. We examined a Korean family in which two individuals had an autosomal-dominant axonal CMT with early-onset, sensory ataxia, tremor, and slow disease progression. Pedigree analysis and exome sequencing identified a de novo missense mutation (p.Y223H) in the diacylglycerol O-acyltransferase 2 (DGAT2) gene. DGAT2 encodes an endoplasmic reticulum-mitochondrial-associated membrane protein, acyl-CoA:diacylglycerol acyltransferase, which catalyzes the final step of the triglyceride (TG) biosynthesis pathway. The patient showed consistently decreased serum TG levels, and overexpression of the mutant DGAT2 significantly inhibited the proliferation of mouse motor neuron cells. Moreover, the variant form of human DGAT2 inhibited the axonal branching in the peripheral nervous system of zebrafish. We suggest that mutation of DGAT2 is the novel underlying cause of an autosomal-dominant axonal CMT2 neuropathy. This study will help provide a better understanding of the pathophysiology of axonal CMT and contribute to the molecular diagnostics of peripheral neuropathies.

  9. Melatonin in Mitochondrial Dysfunction and Related Disorders

    Directory of Open Access Journals (Sweden)

    Venkatramanujam Srinivasan

    2011-01-01

    Full Text Available Mitochondrial dysfunction is considered one of the major causative factors in the aging process, ischemia/reperfusion (I/R, septic shock, and neurodegenerative disorders like Parkinson's disease (PD, Alzheimer's disease (AD, and Huntington's disease (HD. Increased free radical generation, enhanced mitochondrial inducible nitric oxide (NO synthase activity, enhanced NO production, decreased respiratory complex activity, impaired electron transport system, and opening of mitochondrial permeability transition pore all have been suggested as factors responsible for impaired mitochondrial function. Melatonin, the major hormone of the pineal gland, also acts as an antioxidant and as a regulator of mitochondrial bioenergetic function. Both in vitro and in vivo, melatonin was effective for preventing oxidative stress/nitrosative stress-induced mitochondrial dysfunction seen in experimental models of PD, AD, and HD. In addition, melatonin is known to retard aging and to inhibit the lethal effects of septic shock or I/R lesions by maintaining respiratory complex activities, electron transport chain, and ATP production in mitochondria. Melatonin is selectively taken up by mitochondrial membranes, a function not shared by other antioxidants. Melatonin has thus emerged as a major potential therapeutic tool for treating neurodegenerative disorders such as PD or AD, and for preventing the lethal effects of septic shock or I/R.

  10. The C-terminal domains of NF-H and NF-M subunits maintain axonal neurofilament content by blocking turnover of the stationary neurofilament network.

    Directory of Open Access Journals (Sweden)

    Mala V Rao

    Full Text Available Newly synthesized neurofilaments or protofilaments are incorporated into a highly stable stationary cytoskeleton network as they are transported along axons. Although the heavily phosphorylated carboxyl-terminal tail domains of the heavy and medium neurofilament (NF subunits have been proposed to contribute to this process and particularly to stability of this structure, their function is still obscure. Here we show in NF-H/M tail deletion [NF-(H/M(tailΔ] mice that the deletion of both of these domains selectively lowers NF levels 3-6 fold along optic axons without altering either rates of subunit synthesis or the rate of slow axonal transport of NF. Pulse labeling studies carried out over 90 days revealed a significantly faster rate of disappearance of NF from the stationary NF network of optic axons in NF-(H/M(tailΔ mice. Faster NF disappearance was accompanied by elevated levels of NF-L proteolytic fragments in NF-(H/M(tailΔ axons. We conclude that NF-H and NF-M C-terminal domains do not normally regulate NF transport rates as previously proposed, but instead increase the proteolytic resistance of NF, thereby stabilizing the stationary neurofilament cytoskeleton along axons.

  11. NFU1 gene mutation and mitochondrial disorders

    Directory of Open Access Journals (Sweden)

    Yasemin G Kurt

    2016-01-01

    Full Text Available Mitochondrial respiratory chains consist of approximately 100 structural proteins. Thirteen of these structural proteins are encoded by mitochondrial DNA (mtDNA, and the others by nuclear DNA (nDNA. Mutation in any of the mitochondrial structural-protein related genes, regardless of whether they are in the nDNA or mtDNA, might cause mitochondrial disorders. In the recent past, new nuclear genes required for assembly, maintenance, and translation of respiratory chain proteins have been found. Mutation in these genes might also cause mitochondrial disorders (MD. NFU1 gene is one of such genes and has a role in the assembly of iron–sulfur cluster (ISC. ISCs are included in a variety of metalloproteins, such as the ferredoxins, as well as in enzymatic reactions and have been first identified in the oxidation-reduction reactions of mitochondrial electron transport. It is important to be aware of NFU1 gene mutations that may cause severe mitochondrial respiratory chain defects, mitochondrial encephalomyopathies and death, early in life.

  12. Dynamics of axon fasciculation in the presence of neuronal turnover

    CERN Document Server

    Chaudhuri, Debasish; Mohanty, P K; Zapotocky, Martin

    2008-01-01

    We formulate and characterize a model aiming to describe the formation of fascicles of axons mediated by contact axon-axon interactions. The growing axons are represented as interacting directed random walks in two spatial dimensions. To mimic axonal turnover in the mammalian olfactory system, the random walkers are injected and removed at specified rates. In the dynamical steady state, the position-dependent distribution of fascicle sizes obeys a scaling law. We identify several distinct time scales that emerge from the dynamics, are sensitive functions of the microscopic parameters of the model, and can exceed the average axonal lifetime by orders of magnitude. We discuss our findings in terms of an analytically tractable, effective model of fascicle dynamics.

  13. Mitochondrial Morphology and Fundamental Parameters of the Mitochondrial Respiratory Chain Are Altered in Caenorhabditis elegans Strains Deficient in Mitochondrial Dynamics and Homeostasis Processes.

    Science.gov (United States)

    Luz, Anthony L; Rooney, John P; Kubik, Laura L; Gonzalez, Claudia P; Song, Dong Hoon; Meyer, Joel N

    2015-01-01

    Mitochondrial dysfunction has been linked to myriad human diseases and toxicant exposures, highlighting the need for assays capable of rapidly assessing mitochondrial health in vivo. Here, using the Seahorse XFe24 Analyzer and the pharmacological inhibitors dicyclohexylcarbodiimide and oligomycin (ATP-synthase inhibitors), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (mitochondrial uncoupler) and sodium azide (cytochrome c oxidase inhibitor), we measured the fundamental parameters of mitochondrial respiratory chain function: basal oxygen consumption, ATP-linked respiration, maximal respiratory capacity, spare respiratory capacity and proton leak in the model organism Caenhorhabditis elegans. Since mutations in mitochondrial homeostasis genes cause mitochondrial dysfunction and have been linked to human disease, we measured mitochondrial respiratory function in mitochondrial fission (drp-1)-, fusion (fzo-1)-, mitophagy (pdr-1, pink-1)-, and electron transport chain complex III (isp-1)-deficient C. elegans. All showed altered function, but the nature of the alterations varied between the tested strains. We report increased basal oxygen consumption in drp-1; reduced maximal respiration in drp-1, fzo-1, and isp-1; reduced spare respiratory capacity in drp-1 and fzo-1; reduced proton leak in fzo-1 and isp-1; and increased proton leak in pink-1 nematodes. As mitochondrial morphology can play a role in mitochondrial energetics, we also quantified the mitochondrial aspect ratio for each mutant strain using a novel method, and for the first time report increased aspect ratios in pdr-1- and pink-1-deficient nematodes.

  14. KSRP modulation of GAP-43 mRNA stability restricts axonal outgrowth in embryonic hippocampal neurons.

    Directory of Open Access Journals (Sweden)

    Clark W Bird

    Full Text Available The KH-type splicing regulatory protein (KSRP promotes the decay of AU-rich element (ARE-containing mRNAs. Although KSRP is expressed in the nervous system, very little is known about its role in neurons. In this study, we examined whether KSRP regulates the stability of the ARE-containing GAP-43 mRNA. We found that KSRP destabilizes this mRNA by binding to its ARE, a process that requires the presence of its fourth KH domain (KH4. Furthermore, KSRP competed with the stabilizing factor HuD for binding to these sequences. We also examined the functional consequences of KSRP overexpression and knockdown on the differentiation of primary hippocampal neurons in culture. Overexpression of full length KSRP or KSRP without its nuclear localization signal hindered axonal outgrowth in these cultures, while overexpression of a mutant protein without the KH4 domain that has less affinity for binding to GAP-43's ARE had no effect. In contrast, depletion of KSRP led to a rise in GAP-43 mRNA levels and a dramatic increase in axonal length, both in KSRP shRNA transfected cells and neurons cultured from Ksrp(+/- and Ksrp(-/- embryos. Finally we found that overexpression of GAP-43 rescued the axonal outgrowth deficits seen with KSRP overexpression, but only when cells were transfected with GAP-43 constructs containing 3' UTR sequences targeting the transport of this mRNA to axons. Together, our results suggest that KSRP is an important regulator of mRNA stability and axonal length that works in direct opposition to HuD to regulate the levels of GAP-43 and other ARE-containing neuronal mRNAs.

  15. Towards a functional definition of the mitochondrial human proteome

    Directory of Open Access Journals (Sweden)

    Mauro Fasano

    2016-03-01

    Full Text Available The mitochondrial human proteome project (mt-HPP was initiated by the Italian HPP group as a part of both the chromosome-centric initiative (C-HPP and the “biology and disease driven” initiative (B/D-HPP. In recent years several reports highlighted how mitochondrial biology and disease are regulated by specific interactions with non-mitochondrial proteins. Thus, it is of great relevance to extend our present view of the mitochondrial proteome not only to those proteins that are encoded by or transported to mitochondria, but also to their interactors that take part in mitochondria functionality. Here, we propose a graphical representation of the functional mitochondrial proteome by retrieving mitochondrial proteins from the NeXtProt database and adding to the network their interactors as annotated in the IntAct database. Notably, the network may represent a reference to map all the proteins that are currently being identified in mitochondrial proteomics studies.

  16. Chlorpyrifos-Oxon Disrupts Zebrafish Axonal Growth and Motor Behavior

    OpenAIRE

    Yang, Dongren; Lauridsen, Holly; Buels, Kalmia; Chi, Lai-Har; La Du, Jane; Bruun, Donald A.; Olson, James R.; Tanguay, Robert L.; Lein, Pamela J.

    2011-01-01

    Axonal morphology is a critical determinant of neuronal connectivity, and perturbation of the rate or extent of axonal growth during development has been linked to neurobehavioral deficits in animal models and humans. We previously demonstrated that the organophosphorus pesticide (OP) chlorpyrifos (CPF) inhibits axonal growth in cultured neurons. In this study, we used a zebrafish model to determine whether CPF, its oxon metabolite (CPFO), or the excreted metabolite trichloro-2-pyridinol (TCP...

  17. A unified cell biological perspective on axon-myelin injury

    OpenAIRE

    Simons, Mikael; Misgeld, Thomas; Kerschensteiner, Martin

    2014-01-01

    Demyelination and axon loss are pathological hallmarks of the neuroinflammatory disorder multiple sclerosis (MS). Although we have an increasingly detailed understanding of how immune cells can damage axons and myelin individually, we lack a unified view of how the axon–myelin unit as a whole is affected by immune-mediated attack. In this review, we propose that as a result of the tight cell biological interconnection of axons and myelin, damage to either can spread, which might convert a loc...

  18. Axon-glia interaction and membrane traffic in myelin formation

    OpenAIRE

    2014-01-01

    In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialized glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarization followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is...

  19. Characteristics of mitochondrial calpains.

    Science.gov (United States)

    Ozaki, Taku; Tomita, Hiroshi; Tamai, Makoto; Ishiguro, Sei-Ichi

    2007-09-01

    Calpains are considered to be cytoplasmic enzymes, although several studies have shown that calpain-like protease activities also exist in mitochondria. We partially purified mitochondrial calpain from swine liver mitochondria and characterized. Only one type of mitochondrial calpain was detected by the column chromatographies. The mitochondrial calpain was stained with anti-mu-calpain and calpain small subunit antibodies. The susceptibility of mitochondrial calpain to calpain inhibitors and the optimum pH differ from those of cytosolic mu- and m-calpains. The Ca(2+)-dependency of mitochondrial calpain was similar to that of cytosolic mu-calpain. Therefore, we named the protease mitochondrial mu-like calpain. In zymogram analysis, two types of caseinolytic enzymes existed in mitochondria and showed different mobilities from cytosolic mu- and m-calpains. The upper major band was stained with anti-mu-calpain and calpain small subunit antibodies (mitochondrial calpain I, mitochondrial mu-like calpain). The lower band was stained only with anti-calpain small subunit antibody (mitochondrial calpain II, unknown mitochondrial calpain). Calpastatin was not detected in mitochondrial compartments. The mitochondrial calpain processed apoptosis-inducing factor (AIF) to truncated AIF (tAIF), releasing tAIF into the intermembrane space. These results indicate that mitochondrial calpain, which differs from mu- and m-calpains, seems to be a ubiquitous calpain and may play a role in mitochondrial apoptotic signalling.

  20. Modulation of the matrix redox signaling by mitochondrial Ca(2.).

    Science.gov (United States)

    Santo-Domingo, Jaime; Wiederkehr, Andreas; De Marchi, Umberto

    2015-11-26

    Mitochondria sense, shape and integrate signals, and thus function as central players in cellular signal transduction. Ca(2+) waves and redox reactions are two such intracellular signals modulated by mitochondria. Mitochondrial Ca(2+) transport is of utmost physio-pathological relevance with a strong impact on metabolism and cell fate. Despite its importance, the molecular nature of the proteins involved in mitochondrial Ca(2+) transport has been revealed only recently. Mitochondrial Ca(2+) promotes energy metabolism through the activation of matrix dehydrogenases and down-stream stimulation of the respiratory chain. These changes also alter the mitochondrial NAD(P)H/NAD(P)(+) ratio, but at the same time will increase reactive oxygen species (ROS) production. Reducing equivalents and ROS are having opposite effects on the mitochondrial redox state, which are hard to dissect. With the recent development of genetically encoded mitochondrial-targeted redox-sensitive sensors, real-time monitoring of matrix thiol redox dynamics has become possible. The discoveries of the molecular nature of mitochondrial transporters of Ca(2+) combined with the utilization of the novel redox sensors is shedding light on the complex relation between mitochondrial Ca(2+) and redox signals and their impact on cell function. In this review, we describe mitochondrial Ca(2+) handling, focusing on a number of newly identified proteins involved in mitochondrial Ca(2+) uptake and release. We further discuss our recent findings, revealing how mitochondrial Ca(2+) influences the matrix redox state. As a result, mitochondrial Ca(2+) is able to modulate the many mitochondrial redox-regulated processes linked to normal physiology and disease.

  1. Modulation of the matrix redox signaling by mitochondrial Ca2+

    Institute of Scientific and Technical Information of China (English)

    Jaime; Santo-Domingo; Andreas; Wiederkehr; Umberto; De; Marchi

    2015-01-01

    Mitochondria sense,shape and integrate signals,and thus function as central players in cellular signal transduction. Ca2+ waves and redox reactions are two such intracellular signals modulated by mitochondria. Mitochondrial Ca2+ transport is of utmost physio-pathological relevance with a strong impact on metabolism and cell fate. Despite its importance,the molecular nature of the proteins involvedin mitochondrial Ca2+ transport has been revealed only recently. Mitochondrial Ca2+ promotes energy metabolism through the activation of matrix dehydrogenases and downstream stimulation of the respiratory chain. These changes also alter the mitochondrial NAD(P)H/NAD(P)+ ratio,but at the same time will increase reactive oxygen species(ROS) production. Reducing equivalents and ROS are having opposite effects on the mitochondrial redox state,which are hard to dissect. With the recent development of genetically encoded mitochondrial-targeted redoxsensitive sensors,real-time monitoring of matrix thiol redox dynamics has become possible. The discoveries of the molecular nature of mitochondrial transporters of Ca2+ combined with the utilization of the novel redox sensors is shedding light on the complex relation between mitochondrial Ca2+ and redox signals and their impact on cell function. In this review,we describe mitochondrial Ca2+ handling,focusing on a number of newly identified proteins involved in mitochondrial Ca2+ uptake and release. We further discuss our recent findings,revealing how mitochondrial Ca2+ influences the matrix redox state. As a result,mitochondrial Ca2+ is able to modulate the many mitochondrial redox-regulated processes linked to normal physiology and disease.

  2. Single rodent mesohabenular axons release glutamate and GABA

    Science.gov (United States)

    Root, David H.; Mejias-Aponte, Carlos; Zhang, Shiliang; Wang, Huiling; Hoffman, Alexander F.; Lupica, Carl R.; Morales, Marisela

    2016-01-01

    The lateral habenula (LHb) is involved in reward, aversion, addiction, and depression, through descending interactions with several brain structures, including the ventral tegmental area (VTA). VTA provides reciprocal inputs to LHb, but their actions are unclear. Here we show that the majority of rat and mouse VTA neurons innervating LHb co-express markers for both glutamate-signaling (vesicular glutamate transporter 2, VGluT2) and GABA-signaling (glutamate decarboxylase, GAD; and vesicular GABA transporter, VGaT). A single axon from these mesohabenular neurons co-expresses VGluT2-protein and VGaT-protein, and surprisingly establishes symmetric and asymmetric synapses on LHb neurons. In LHb slices, light activation of mesohabenular fibers expressing channelrhodopsin-2 (ChR2) driven by VGluT2 or VGaT promoters elicits release of both glutamate and GABA onto single LHb neurons. In vivo light-activation of mesohabenular terminals inhibits or excites LHb neurons. Our findings reveal an unanticipated type of VTA neuron that co-transmits glutamate and GABA, and provides the majority of mesohabenular inputs. PMID:25242304

  3. Corticostriatal combinatorics: the implications of corticostriatal axonal arborizations.

    Science.gov (United States)

    Zheng, T; Wilson, C J

    2002-02-01

    The complete striatal axonal arborizations of 16 juxtacellularly stained cortical pyramidal cells were analyzed. Corticostriatal neurons were located in the medial agranular or anterior cingulate cortex of rats. All axons were of the extended type and formed synaptic contacts in both the striosomal and matrix compartments as determined by counterstaining for the mu-opiate receptor. Six axonal arborizations were from collaterals of brain stem-projecting cells and the other 10 from bilaterally projecting cells with no brain stem projections. The distribution of synaptic boutons along the axons were convolved with the average dendritic tree volume of spiny projection neurons to obtain an axonal innervation volume and innervation density map for each axon. Innervation volumes varied widely, with single axons occupying between 0.4 and 14.2% of the striatum (average = 4%). The total number of boutons formed by individual axons ranged from 25 to 2,900 (average = 879). Within the innervation volume, the density of innervation was extremely sparse but inhomogeneous. The pattern of innervation resembled matrisomes, as defined by bulk labeling and functional mapping experiments, superimposed on a low background innervation. Using this sample as representative of all corticostriatal axons, the total number of corticostriatal neurons was estimated to be 17 million, about 10 times the number of striatal projection neurons.

  4. Molecular analysis of axon repulsion by the notochord.

    Science.gov (United States)

    Anderson, Christopher N G; Ohta, Kunimasa; Quick, Marie M; Fleming, Angeleen; Keynes, Roger; Tannahill, David

    2003-03-01

    During development of the amniote peripheral nervous system, the initial trajectory of primary sensory axons is determined largely by the action of axon repellents. We have shown previously that tissues flanking dorsal root ganglia, the notochord lying medially and the dermamyotomes lying laterally, are sources of secreted molecules that prevent axons from entering inappropriate territories. Although there is evidence suggesting that SEMA3A contributes to the repellent activity of the dermamyotome, the nature of the activity secreted by the notochord remains undetermined. We have employed an expression cloning strategy to search for axon repellents secreted by the notochord, and have identified SEMA3A as a candidate repellent. Moreover, using a spectrum of different axon populations to assay the notochord activity, together with neuropilin/Fc receptor reagents to block semaphorin activity in collagen gel assays, we show that SEMA3A probably contributes to notochord-mediated repulsion. Sympathetic axons that normally avoid the midline in vivo are also repelled, in part, by a semaphorin-based notochord activity. Although our results implicate semaphorin signalling in mediating repulsion by the notochord, repulsion of early dorsal root ganglion axons is only partially blocked when using neuropilin/Fc reagents. Moreover, retinal axons, which are insensitive to SEMA3A, are also repelled by the notochord. We conclude that multiple factors act in concert to guide axons in this system, and that further notochord repellents remain to be identified.

  5. Differences in excitability properties of FDI and ADM motor axons.

    Science.gov (United States)

    Bae, Jong Seok; Sawai, Setsu; Misawa, Sonoko; Kanai, Kazuaki; Isose, Sagiri; Kuwabara, Satoshi

    2009-03-01

    The first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles are innervated by the same ulnar nerve, but studies have shown that the former is much more severely affected in amyotrophic lateral sclerosis. In this study, threshold tracking was used to investigate whether membrane properties differ between FDI and ADM motor axons. In 12 normal subjects, compound muscle action potentials were recorded from FDI and ADM after ulnar nerve stimulation at the wrist. The strength-duration time constant was significantly longer in the FDI axons than in the ADM axons, and latent addition studies showed greater threshold changes at the conditioning-test stimulus of 0.2 ms in FDI than in ADM axons. These findings suggest that nodal persistent sodium conductances are more prominent in FDI axons than in ADM axons, and therefore excitability is physiologically higher in FDI axons. Even in the same nerve at the same sites, membrane properties of FDI and ADM motor axons differ significantly, and thus their axonal/neuronal responses to disease may also differ.

  6. Axonal autophagy during regeneration of the rat sciatic nerve

    Institute of Scientific and Technical Information of China (English)

    Kangrong Lu; Zhongxian Piao; Zhenxi Liu; Weiwang Gu; Wanshan Wang; Nngjie Piao

    2008-01-01

    BACKGROUND: The removal of degenerated axonal debris during Wallerian degeneration is very important for nerve regeneration. However, the mechanism by which debris is removed is not been completely understood. Considerable controversy remains as to the clearance pathway and cells that are involved. OBJECTIVE: To investigate axonal autophagy during removal of degenerated axonal debris by transecting the sciatic nerve in a rat Wallerian degeneration model.DESIGN, TIME AND SETTING: Experimental neuropathological analysis. The experiment was conducted at the Laboratory Animal Service Center of the Southern Medical University between January and June 2005. MATERIALS: Fifty-four adult, Wistar rats of either sex, weighing 180-250 g, were obtained from the Laboratory Animal Service Center of the Southern Medical University. Animals were randomly divided into nine groups of six rats. METHODS: Wallerian degeneration was induced by transecting the rat sciatic nerve, and tissue samples from the distal stump were obtained 0.2, 0.4, 1, 2, 3, 4, 7, 10, and 15 days post-transection. Ultrathin sections were prepared for electron microscopy to study ultrastructure and enzyme cytochemistry staining. MAIN OUTCOME MEASURES: Ultrastructure (axon body, autophagic body, and cystoskeleton) of axons and myelin sheaths observed with electron microscopy; acidic phosphatase activity detected by Gomori staining using electron microscopy. RESULTS: The major changes of degenerating axons after transection were axoplasm swelling and separation of axons from their myelin sheath between five hours and two days post-transection. At four days post-transection, the axoplasm condensed and axons were completely separated from the myelin sheath, forming dissociative axon bodies. Vacuoles of different sizes formed in axons during the early phase after lesion. Larger dissociative axon bodies were formed when the axons were completely separated from the myelin sheath during a late phase. The axolemma

  7. Crossing the Border: Molecular Control of Motor Axon Exit

    Directory of Open Access Journals (Sweden)

    Arlene Bravo-Ambrosio

    2011-11-01

    Full Text Available Living organisms heavily rely on the function of motor circuits for their survival and for adapting to ever-changing environments. Unique among central nervous system (CNS neurons, motor neurons (MNs project their axons out of the CNS. Once in the periphery, motor axons navigate along highly stereotyped trajectories, often at considerable distances from their cell bodies, to innervate appropriate muscle targets. A key decision made by pathfinding motor axons is whether to exit the CNS through dorsal or ventral motor exit points (MEPs. In contrast to the major advances made in understanding the mechanisms that regulate the specification of MN subtypes and the innervation of limb muscles, remarkably little is known about how MN axons project out of the CNS. Nevertheless, a limited number of studies, mainly in Drosophila, have identified transcription factors, and in some cases candidate downstream effector molecules, that are required for motor axons to exit the spinal cord. Notably, specialized neural crest cell derivatives, referred to as Boundary Cap (BC cells, pre-figure and demarcate MEPs in vertebrates. Surprisingly, however, BC cells are not required for MN axon exit, but rather restrict MN cell bodies from ectopically migrating along their axons out of the CNS. Here, we describe the small set of studies that have addressed motor axon exit in Drosophila and vertebrates, and discuss our fragmentary knowledge of the mechanisms, which guide motor axons out of the CNS.

  8. A unified cell biological perspective on axon-myelin injury.

    Science.gov (United States)

    Simons, Mikael; Misgeld, Thomas; Kerschensteiner, Martin

    2014-08-04

    Demyelination and axon loss are pathological hallmarks of the neuroinflammatory disorder multiple sclerosis (MS). Although we have an increasingly detailed understanding of how immune cells can damage axons and myelin individually, we lack a unified view of how the axon-myelin unit as a whole is affected by immune-mediated attack. In this review, we propose that as a result of the tight cell biological interconnection of axons and myelin, damage to either can spread, which might convert a local inflammatory disease process early in MS into the global progressive disorder seen during later stages. This mode of spreading could also apply to other neurological disorders.

  9. Dopaminergic axon guidance: which makes what?

    Directory of Open Access Journals (Sweden)

    Laetitia ePrestoz

    2012-07-01

    Full Text Available Mesotelencephalic pathways in the adult central nervous system have been studied in great detail because of their implication in major physiological functions as well as in psychiatric, neurological and neurodegenerative diseases. However, the ontogeny of these pathways and the molecular mechanisms that guide dopaminergic axons during embryogenesis have been only recently studied. This line of research is of crucial interest for the repair of lesioned circuits in adulthood following neurodegenerative diseases or common traumatic injuries. For instance, in the adult, the anatomic and functional repair of the nigrostriatal pathway following dopaminergic embryonic neuron transplantation suggests that specific guidance cues exist which govern embryonic fibers outgrowth, and suggests that axons from transplanted embryonic cells are able to respond to theses cues, which then guide them to their final targets. In this review, we first synthesize the work that has been performed in the last few years on developing mesotelencephalic pathways, and summarize the current knowledge on the identity of cellular and molecular signals thought to be involved in establishing mesotelencephalic dopaminergic neuronal connectivity during embryogenesis in the central nervous system of rodents. Then, we review the modulation of expression of these molecular signals in the lesioned adult brain and discuss their potential role in remodeling the mesotelencephalic dopaminergic circuitry, with a particular focus on Parkinson’s disease. Identifying guidance molecules involved in the connection of grafted cells may be useful for cellular therapy in Parkinsonian patients, as these molecules may help direct axons from grafted cells along the long distance they have to travel from the substantia nigra to the striatum.

  10. Axonal regeneration and development of de novo axons from distal dendrites of adult feline commissural interneurons after a proximal axotomy

    DEFF Research Database (Denmark)

    Fenrich, Keith K; Skelton, Nicole; MacDermid, Victoria E

    2007-01-01

    at 4-5 weeks post injury. The somata of axotomized CINs were identified by the presence of immunoreactivity for the axonal growth-associated protein-43 (GAP-43). Nearly half of the CINs had de novo axons that emerged from distal dendrites. These axons lacked immunoreactivity for the dendritic protein......Following proximal axotomy, several types of neurons sprout de novo axons from distal dendrites. These processes may represent a means of forming new circuits following spinal cord injury. However, it is not know whether mammalian spinal interneurons, axotomized as a result of a spinal cord injury......, develop de novo axons. Our goal was to determine whether spinal commissural interneurons (CINs), axotomized by 3-4-mm midsagittal transection at C3, form de novo axons from distal dendrites. All experiments were performed on adult cats. CINs in C3 were stained with extracellular injections of Neurobiotin...

  11. Elevated mitochondrial oxidative stress impairs metabolic adaptations to exercise in skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Justin D Crane

    Full Text Available Mitochondrial oxidative stress is a complex phenomenon that is inherently tied to energy provision and is implicated in many metabolic disorders. Exercise training increases mitochondrial oxidative capacity in skeletal muscle yet it remains unclear if oxidative stress plays a role in regulating these adaptations. We demonstrate that the chronic elevation in mitochondrial oxidative stress present in Sod2 (+/- mice impairs the functional and biochemical mitochondrial adaptations to exercise. Following exercise training Sod2 (+/- mice fail to increase maximal work capacity, mitochondrial enzyme activity and mtDNA copy number, despite a normal augmentation of mitochondrial proteins. Additionally, exercised Sod2 (+/- mice cannot compensate for their higher amount of basal mitochondrial oxidative damage and exhibit poor electron transport chain complex assembly that accounts for their compromised adaptation. Overall, these results demonstrate that chronic skeletal muscle mitochondrial oxidative stress does not impact exercise induced mitochondrial biogenesis, but impairs the resulting mitochondrial protein function and can limit metabolic plasticity.

  12. IMP2 axonal localization, RNA interactome, and function in the development of axon trajectories

    DEFF Research Database (Denmark)

    Preitner, Nicolas; Quan, Jie; Li, Xinmin

    2016-01-01

    RNA-based regulatory mechanisms play important roles in the development and plasticity of neural circuits and neurological disease. Developing axons provide a model well suited to the study of RNA-based regulation, and contain specific subsets of mRNAs that are locally translated and have roles i...

  13. White-matter astrocytes, axonal energy metabolism, and axonal degeneration in multiple sclerosis

    NARCIS (Netherlands)

    Cambron, Melissa; D'haeseleer, Miguel; Laureys, Guy; Clinckers, Ralph; Debruyne, Jan; De Keyser, Jacques

    2012-01-01

    In patients with multiple sclerosis (MS), a diffuse axonal degeneration occurring throughout the white matter of the central nervous system causes progressive neurologic disability. The underlying mechanism is unclear. This review describes a number of pathways by which dysfunctional astrocytes in M

  14. AxonPacking: An Open-Source Software to Simulate Arrangements of Axons in White Matter.

    Science.gov (United States)

    Mingasson, Tom; Duval, Tanguy; Stikov, Nikola; Cohen-Adad, Julien

    2017-01-01

    HIGHLIGHTS AxonPacking: Open-source software for simulating white matter microstructure.Validation on a theoretical disk packing problem.Reproducible and stable for various densities and diameter distributions.Can be used to study interplay between myelin/fiber density and restricted fraction. Quantitative Magnetic Resonance Imaging (MRI) can provide parameters that describe white matter microstructure, such as the fiber volume fraction (FVF), the myelin volume fraction (MVF) or the axon volume fraction (AVF) via the fraction of restricted water (fr). While already being used for clinical application, the complex interplay between these parameters requires thorough validation via simulations. These simulations required a realistic, controlled and adaptable model of the white matter axons with the surrounding myelin sheath. While there already exist useful algorithms to perform this task, none of them combine optimisation of axon packing, presence of myelin sheath and availability as free and open source software. Here, we introduce a novel disk packing algorithm that addresses these issues. The performance of the algorithm is tested in term of reproducibility over 50 runs, resulting density, and stability over iterations. This tool was then used to derive multiple values of FVF and to study the impact of this parameter on fr and MVF in light of the known microstructure based on histology sample. The standard deviation of the axon density over runs was lower than 10(-3) and the expected hexagonal packing for monodisperse disks was obtained with a density close to the optimal density (obtained: 0.892, theoretical: 0.907). Using an FVF ranging within [0.58, 0.82] and a mean inter-axon gap ranging within [0.1, 1.1] μm, MVF ranged within [0.32, 0.44] and fr ranged within [0.39, 0.71], which is consistent with the histology. The proposed algorithm is implemented in the open-source software AxonPacking (https://github.com/neuropoly/axonpacking) and can be useful for

  15. ALS5/SPG11/KIAA1840 mutations cause autosomal recessive axonal Charcot-Marie-Tooth disease.

    Science.gov (United States)

    Montecchiani, Celeste; Pedace, Lucia; Lo Giudice, Temistocle; Casella, Antonella; Mearini, Marzia; Gaudiello, Fabrizio; Pedroso, José L; Terracciano, Chiara; Caltagirone, Carlo; Massa, Roberto; St George-Hyslop, Peter H; Barsottini, Orlando G P; Kawarai, Toshitaka; Orlacchio, Antonio

    2016-01-01

    Charcot-Marie-Tooth disease is a group of hereditary peripheral neuropathies that share clinical characteristics of progressive distal muscle weakness and atrophy, foot deformities, distal sensory loss, as well as diminished tendon reflexes. Hundreds of causative DNA changes have been found, but much of the genetic basis of the disease is still unexplained. Mutations in the ALS5/SPG11/KIAA1840 gene are a frequent cause of autosomal recessive hereditary spastic paraplegia with thin corpus callosum and peripheral axonal neuropathy, and account for ∼ 40% of autosomal recessive juvenile amyotrophic lateral sclerosis. The overlap of axonal Charcot-Marie-Tooth disease with both diseases, as well as the common autosomal recessive inheritance pattern of thin corpus callosum and axonal Charcot-Marie-Tooth disease in three related patients, prompted us to analyse the ALS5/SPG11/KIAA1840 gene in affected individuals with autosomal recessive axonal Charcot-Marie-Tooth disease. We investigated 28 unrelated families with autosomal recessive axonal Charcot-Marie-Tooth disease defined by clinical, electrophysiological, as well as pathological evaluation. Besides, we screened for all the known genes related to axonal autosomal recessive Charcot-Marie-Tooth disease (CMT2A2/HMSN2A2/MFN2, CMT2B1/LMNA, CMT2B2/MED25, CMT2B5/NEFL, ARCMT2F/dHMN2B/HSPB1, CMT2K/GDAP1, CMT2P/LRSAM1, CMT2R/TRIM2, CMT2S/IGHMBP2, CMT2T/HSJ1, CMTRID/COX6A1, ARAN-NM/HINT and GAN/GAN), for the genes related to autosomal recessive hereditary spastic paraplegia with thin corpus callosum and axonal peripheral neuropathy (SPG7/PGN, SPG15/ZFYVE26, SPG21/ACP33, SPG35/FA2H, SPG46/GBA2, SPG55/C12orf65 and SPG56/CYP2U1), as well as for the causative gene of peripheral neuropathy with or without agenesis of the corpus callosum (SLC12A6). Mitochondrial disorders related to Charcot-Marie-Tooth disease type 2 were also excluded by sequencing POLG and TYMP genes. An additional locus for autosomal recessive Charcot

  16. [Current progress in functions of axon guidance molecule Robo and underlying molecular mechanism].

    Science.gov (United States)

    Li, Xiao-Tong; Zhou, Qi-Sheng; Yu, Qi; Zhao, Xiao; Liu, Qing-Xin

    2014-06-25

    The axon guidance molecule Robo is a transmembrane protein which is conserved during evolution. Robo and its ligand, Slit, have been implicated in regulating many developmental processes, such as axon guidance, neuronal migration, tumor metastasis, angiogenesis, lung morphogenesis, kidney morphogenesis, heart morphogenesis, ovary development and gonad development. Robo function mainly depends on the binding of its Ig1 domain to the LRR-2 domain of Slit ligand. Meanwhile, Robo function is also mediated by binding to some signaling molecules, including the heparan sulfate proteoglycans (HSPGs), GTPase-activating proteins (GAPs) and tyrosine kinase Abelson. Several transcription factors, including Hox, Midline and Nkx2.9, were shown to regulate robo expression. In addition, alternative splicing and transport regulation also affect Robo function. In this review, we summarized the studies on the molecular structure, functions and molecular mechanism of Robo, which would propose a novel strategy for the research of neural development, as well as prevention and treatment of nervous system diseases and cancers.

  17. Dynamics of the mitochondrial network during mitosis.

    Science.gov (United States)

    Kanfer, Gil; Kornmann, Benoît

    2016-04-15

    During mitosis, cells undergo massive deformation and reorganization, impacting on all cellular structures. Mitochondria, in particular, are highly dynamic organelles, which constantly undergo events of fission, fusion and cytoskeleton-based transport. This plasticity ensures the proper distribution of the metabolism, and the proper inheritance of functional organelles. During cell cycle, mitochondria undergo dramatic changes in distribution. In this review, we focus on the dynamic events that target mitochondria during mitosis. We describe how the cell-cycle-dependent microtubule-associated protein centromeric protein F (Cenp-F) is recruited to mitochondria by the mitochondrial Rho GTPase (Miro) to promote mitochondrial transport and re-distribution following cell division.

  18. Excitotoxins, Mitochondrial and Redox Disturbances in Multiple Sclerosis

    Science.gov (United States)

    Rajda, Cecilia; Pukoli, Dániel; Bende, Zsuzsanna; Majláth, Zsófia; Vécsei, László

    2017-01-01

    Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). There is increasing evidence that MS is not only characterized by immune mediated inflammatory reactions, but also by neurodegenerative processes. There is cumulating evidence that neurodegenerative processes, for example mitochondrial dysfunction, oxidative stress, and glutamate (Glu) excitotoxicity, seem to play an important role in the pathogenesis of MS. The alteration of mitochondrial homeostasis leads to the formation of excitotoxins and redox disturbances. Mitochondrial dysfunction (energy disposal failure, apoptosis, etc.), redox disturbances (oxidative stress and enhanced reactive oxygen and nitrogen species production), and excitotoxicity (Glu mediated toxicity) may play an important role in the progression of the disease, causing axonal and neuronal damage. This review focuses on the mechanisms of mitochondrial dysfunction (including mitochondrial DNA (mtDNA) defects and mitochondrial structural/functional changes), oxidative stress (including reactive oxygen and nitric species), and excitotoxicity that are involved in MS and also discusses the potential targets and tools for therapeutic approaches in the future. PMID:28208701

  19. Molecular disruptions of the panglial syncytium block potassium siphoning and axonal saltatory conduction: pertinence to neuromyelitis optica and other demyelinating diseases of the central nervous system.

    Science.gov (United States)

    Rash, J E

    2010-07-28

    The panglial syncytium maintains ionic conditions required for normal neuronal electrical activity in the central nervous system (CNS). Vital among these homeostatic functions is "potassium siphoning," a process originally proposed to explain astrocytic sequestration and long-distance disposal of K(+) released from unmyelinated axons during each action potential. Fundamentally different, more efficient processes are required in myelinated axons, where axonal K(+) efflux occurs exclusively beneath and enclosed within the myelin sheath, precluding direct sequestration of K(+) by nearby astrocytes. Molecular mechanisms for entry of excess K(+) and obligatorily-associated osmotic water from axons into innermost myelin are not well characterized, whereas at the output end, axonally-derived K(+) and associated osmotic water are known to be expelled by Kir4.1 and aquaporin-4 channels concentrated in astrocyte endfeet that surround capillaries and that form the glia limitans. Between myelin (input end) and astrocyte endfeet (output end) is a vast network of astrocyte "intermediaries" that are strongly inter-linked, including with myelin, by abundant gap junctions that disperse excess K(+) and water throughout the panglial syncytium, thereby greatly reducing K(+)-induced osmotic swelling of myelin. Here, I review original reports that established the concept of potassium siphoning in unmyelinated CNS axons, summarize recent revolutions in our understanding of K(+) efflux during axonal saltatory conduction, then describe additional components required by myelinated axons for a newly-described process of voltage-augmented "dynamic" potassium siphoning. If any of several molecular components of the panglial syncytium are compromised, K(+) siphoning is blocked, myelin is destroyed, and axonal saltatory conduction ceases. Thus, a common thread linking several CNS demyelinating diseases is the disruption of potassium siphoning/water transport within the panglial syncytium

  20. Integrated compound profiling screens identify the mitochondrial electron transport chain as the molecular target of the natural products manassantin, sesquicillin, and arctigenin.

    Science.gov (United States)

    Lai, Kevin; Selinger, Douglas W; Solomon, Jonathan M; Wu, Hua; Schmitt, Esther; Serluca, Fabrizio C; Curtis, Daniel; Benson, John D

    2013-01-18

    Phenotypic compound screens can be used to identify novel targets in signaling pathways and disease processes, but the usefulness of these screens depends on the ability to quickly determine the target and mechanism of action of the molecules identified as hits. One fast route to discovering the mechanism of action of a compound is to profile its properties and to match this profile with those of compounds of known mechanism of action. In this work, the Novartis collection of over 12,000 pure natural products was screened for effects on early zebrafish development. The largest phenotypic class of hits, which caused developmental arrest without necrosis, contained known electron transport chain inhibitors and many compounds of unknown mechanism of action. High-throughput transcriptional profiling revealed that these compounds are mechanistically related to one another. Metabolic and biochemical assays confirmed that all of the molecules that induced developmental arrest without necrosis inhibited the electron transport chain. These experiments demonstrate that the electron transport chain is the target of the natural products manassantin, sesquicillin, and arctigenin. The overlap between the zebrafish and transcriptional profiling screens was not perfect, indicating that multiple profiling screens are necessary to fully characterize molecules of unknown function. Together, zebrafish screening and transcriptional profiling represent sensitive and scalable approaches for identifying bioactive compounds and elucidating their mechanism of action.

  1. Axonal accumulation of synaptic markers in APP transgenic Drosophila depends on the NPTY motif and is paralleled by defects in synaptic plasticity

    DEFF Research Database (Denmark)

    Rusu, Patricia; Jansen, Anna; Soba, Peter;

    2007-01-01

    Alzheimer's disease (AD) is characterized by neurofibrillary tangles and extracellular plaques, which consist mainly of beta-amyloid derived from the beta-amyloid precursor protein (APP). An additional feature of AD is axonopathy, which might contribute to impairment of cognitive functions....... Specifically, axonal transport defects have been reported in AD animal models, including mice and flies that overexpress APP and tau. Here we demonstrate that the APP-induced traffic jam of vesicles in peripheral nerves of Drosophila melanogaster larvae depends on the four residues NPTY motif in the APP...... intracellular domain. Furthermore, heterologous expression of Fe65 and JIP1b, scaffolding proteins interacting with the NPTY motif, also perturb axonal transport. Together, these data indicate that JIP1b or Fe65 may be involved in the APP-induced axonal transport defect. Moreover, we have characterized...

  2. Mitochondrial biogenesis and turnover.

    Science.gov (United States)

    Diaz, Francisca; Moraes, Carlos T

    2008-07-01

    Mitochondrial biogenesis is a complex process involving the coordinated expression of mitochondrial and nuclear genes, the import of the products of the latter into the organelle and turnover. The mechanisms associated with these events have been intensively studied in the last 20 years and our understanding of their details is much improved. Mitochondrial biogenesis requires the participation of calcium signaling that activates a series of calcium-dependent protein kinases that in turn activate transcription factors and coactivators such as PGC-1alpha that regulates the expression of genes coding for mitochondrial components. In addition, mitochondrial biogenesis involves the balance of mitochondrial fission-fusion. Mitochondrial malfunction or defects in any of the many pathways involved in mitochondrial biogenesis can lead to degenerative diseases and possibly play an important part in aging.

  3. Mitochondrial Composition,Function and Stress Response in Plants

    Institute of Scientific and Technical Information of China (English)

    Richard P.Jacoby; Lei Li; Shaobai Huang; Chun Pong Lee; A.Harvey Millar; Nicolas L.Taylor

    2012-01-01

    The primary function of mitochondria is respiration,where catabolism of substrates is coupled to ATP synthesis via oxidative phosphorylation.In plants,mitochondrial composition is relatively complex and flexible and has specific pathways to support photosynthetic processes in illuminated leaves.This review begins with outlining current models of mitochondrial composition in plant cells,with an emphasis upon the assembly of the complexes of the classical electron transport chain (ETC).Next,we focus upon the comparative analysis of mitochondrial function from different tissue types.A prominent theme in the plant mitochondrial literature involves linking mitochondrial composition to environmental stress responses,and this review then gives a detailed outline of how oxidative stress impacts upon the plant mitochondrial proteome with particular attention to the role of transition metals.This is followed by an analysis of the signaling capacity of mitochondrial reactive oxygen species,which studies the transcriptional changes of stress responsive genes as a framework to define specific signals emanating from the mitochondrion.Finally,specific mitochondrial roles during exposure to harsh environments are outlined,with attention paid to mitochondrial delivery of energy and intermediates,mitochondrial support for photosynthesis,and mitochondrial processes operating within root cells that mediate tolerance to anoxia and unfavorable soil chemistries.

  4. Mitochondrial Machineries for Protein Import and Assembly.

    Science.gov (United States)

    Wiedemann, Nils; Pfanner, Nikolaus

    2017-03-15

    Mitochondria are essential organelles with numerous functions in cellular metabolism and homeostasis. Most of the >1,000 different mitochondrial proteins are synthesized as precursors in the cytosol and are imported into mitochondria by five transport pathways. The protein import machineries of the mitochondrial membranes and aqueous compartments reveal a remarkable variability of mechanisms for protein recognition, translocation, and sorting. The protein translocases do not operate as separate entities but are connected to each other and to machineries with functions in energetics, membrane organization, and quality control. Here, we discuss the versatility and dynamic organization of the mitochondrial protein import machineries. Elucidating the molecular mechanisms of mitochondrial protein translocation is crucial for understanding the integration of protein translocases into a large network that controls organelle biogenesis, function, and dynamics. Expected final online publication date for the Annual Review of Biochemistry Volume 86 is June 20, 2017. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

  5. Misfolded SOD1 associated with motor neuron mitochondria alters mitochondrial shape and distribution prior to clinical onset.

    Directory of Open Access Journals (Sweden)

    Christine Vande Velde

    Full Text Available Mutations in superoxide dismutase (SOD1 are causative for inherited amyotrophic lateral sclerosis. A proportion of SOD1 mutant protein is misfolded onto the cytoplasmic face of mitochondria in one or more spinal cord cell types. By construction of mice in which mitochondrially targeted enhanced green fluorescent protein is selectively expressed in motor neurons, we demonstrate that axonal mitochondria of motor neurons are primary in vivo targets for misfolded SOD1. Mutant SOD1 alters axonal mitochondrial morphology and distribution, with dismutase active SOD1 causing mitochondrial clustering at the proximal side of Schmidt-Lanterman incisures within motor axons and dismutase inactive SOD1 producing aberrantly elongated axonal mitochondria beginning pre-symptomatically and increasing in severity as disease progresses. Somal mitochondria are altered by mutant SOD1, with loss of the characteristic cylindrical, networked morphology and its replacement by a less elongated, more spherical shape. These data indicate that mutant SOD1 binding to mitochondria disrupts normal mitochondrial distribution and size homeostasis as early pathogenic features of SOD1 mutant-mediated ALS.

  6. Molecular Determinants Fundamental to Axon Regeneration after SCI

    Science.gov (United States)

    2014-09-01

    TITLE: Molecular Determinants Fundamental to Axon Regeneration after SCI PRINCIPAL INVESTIGATOR: Jeffrey Alan Plunkett, Ph.D. Martin...TYPE FINAL 3. DATES COVERED (From - To) 1 Sept 2011 - 1 Sept 2014 4. TITLE AND SUBTITLE Molecular Determinants Fundamental to Axon Regeneration...available that restore motor impairments resulting fromspinal cord injury (SCI). Soldiers with SCI are permanently paralyzed and in needof lifelong care

  7. Molecular Determinants Fundamental to Axon Regeneration after SCI

    Science.gov (United States)

    2012-06-01

    currently employed to investigate the evolution of the scar and the time course of axon regeneration after spinal cord injury. The data from these...Medicine, Pittsburgh, PA. It has been established in amphibians and fish that neurons can successfully regenerate their axons in the damaged central

  8. Spontaneous axonal regeneration in rodent spinal cord after ischemic injury

    DEFF Research Database (Denmark)

    von Euler, Mia; Janson, A M; Larsen, Jytte Overgaard;

    2002-01-01

    Here we present evidence for spontaneous and long-lasting regeneration of CNS axons after spinal cord lesions in adult rats. The length of 200 kD neurofilament (NF)-immunolabeled axons was estimated after photochemically induced ischemic spinal cord lesions using a stereological tool. The total l...

  9. Inhibiting poly(ADP-ribosylation) improves axon regeneration

    Science.gov (United States)

    Byrne, Alexandra B; McWhirter, Rebecca D; Sekine, Yuichi; Strittmatter, Stephen M; Miller, David M; Hammarlund, Marc

    2016-01-01

    The ability of a neuron to regenerate its axon after injury depends in part on its intrinsic regenerative potential. Here, we identify novel intrinsic regulators of axon regeneration: poly(ADP-ribose) glycohodrolases (PARGs) and poly(ADP-ribose) polymerases (PARPs). PARGs, which remove poly(ADP-ribose) from proteins, act in injured C. elegans GABA motor neurons to enhance axon regeneration. PARG expression is regulated by DLK signaling, and PARGs mediate DLK function in enhancing axon regeneration. Conversely, PARPs, which add poly(ADP-ribose) to proteins, inhibit axon regeneration of both C. elegans GABA neurons and mammalian cortical neurons. Furthermore, chemical PARP inhibitors improve axon regeneration when administered after injury. Our results indicate that regulation of poly(ADP-ribose) levels is a critical function of the DLK regeneration pathway, that poly-(ADP ribosylation) inhibits axon regeneration across species, and that chemical inhibition of PARPs can elicit axon regeneration. DOI: http://dx.doi.org/10.7554/eLife.12734.001

  10. Axon guidance of rat cortical neurons by microcontact printed gradients.

    Science.gov (United States)

    Fricke, Rita; Zentis, Peter D; Rajappa, Lionel T; Hofmann, Boris; Banzet, Marko; Offenhäusser, Andreas; Meffert, Simone H

    2011-03-01

    Substrate-bound gradients expressed in numerous spatio-temporal patterns play a crucial role during the development of complex neural circuits. A deeper understanding of the axon guidance mechanism is provided by studying the effect of a defined substrate-bound cue on a confined neural network. In this study, we constructed a discontinuous substrate-bound gradient to control neuronal cell position, the path of neurite growth, and axon directionality. A variety of gradient patterns, with slight changes in slope, width, and length were designed and fabricated by microcontact printing using laminin/poly-l-lysine (PLL) or PLL alone. The gradients were tested for neurite growth and their impact on axon guidance of embryonic rat cortical neurons. The neurite length was determined and the axon was evaluated by Tau-1 immunostaining. We found that the microgradients of laminin/PLL and PLL directed neurons' adhesion, differentially controlled the neurite growth, and guided up to 84% of the axons. The effect of the protein micropattern on axon guidance and neurite growth depended on the protein and geometric parameters used. Our approach proved to be very successful in guiding axons of single multipolar neurons with very high efficiency. It could thereby be useful to engineer defined neural networks for analyzing signal processing of functional circuits, as well as to unravel fundamental questions of the axon guidance mechanism.

  11. SnoN facilitates axonal regeneration after spinal cord injury.

    Directory of Open Access Journals (Sweden)

    Jiun L Do

    Full Text Available Adult CNS neurons exhibit a reduced capacity for growth compared to developing neurons, due in part to downregulation of growth-associated genes as development is completed. We tested the hypothesis that SnoN, an embryonically regulated transcription factor that specifies growth of the axonal compartment, can enhance growth in injured adult neurons. In vitro, SnoN overexpression in dissociated adult DRG neuronal cultures significantly enhanced neurite outgrowth. Moreover, TGF-β1, a negative regulator of SnoN, inhibited neurite outgrowth, and SnoN over-expression overcame this inhibition. We then examined whether SnoN influenced axonal regeneration in vivo: indeed, expression of a mutant form of SnoN resistant to degradation significantly enhanced axonal regeneration following cervical spinal cord injury, despite peri-lesional upregulation of TGF-β1. Thus, a developmental mechanism that specifies extension of the axonal compartment also promotes axonal regeneration after adult CNS injury.

  12. Internodal function in normal and regenerated mammalian axons

    DEFF Research Database (Denmark)

    Moldovan, M; Krarup, C

    2007-01-01

    AIM: Following Wallerian degeneration, peripheral myelinated axons have the ability to regenerate and, given a proper pathway, establish functional connections with targets. In spite of this capacity, the clinical outcome of nerve regeneration remains unsatisfactory. Early studies have found...... that regenerated internodes remain persistently short though this abnormality did not seem to influence recovery in conduction. It remains unclear to which extent abnormalities in axonal function itself may contribute to the poor outcome of nerve regeneration. METHODS: We review experimental evidence indicating...... that internodes play an active role in axonal function. RESULTS: By investigating internodal contribution to axonal excitability we have found evidence that axonal function may be permanently compromised in regenerated nerves. Furthermore, we illustrate that internodal function is also abnormal in regenerated...

  13. Diversity in degrees of freedom of mitochondrial transit peptides.

    NARCIS (Netherlands)

    Staiger, C.; Hinneburg, A.; Kloesgen, R.B.

    2009-01-01

    Most mitochondrial proteins are synthesized in the cytosol of eukaryotic cells as precursor proteins carrying N-terminal extensions called transit peptides or presequences, which mediate their specific transport into mitochondria. However, plant cells possess a second potential target organelle

  14. Altered Mitochondrial Dynamics and TBI Pathophysiology.

    Science.gov (United States)

    Fischer, Tara D; Hylin, Michael J; Zhao, Jing; Moore, Anthony N; Waxham, M Neal; Dash, Pramod K

    2016-01-01

    Mitochondrial function is intimately linked to cellular survival, growth, and death. Mitochondria not only generate ATP from oxidative phosphorylation, but also mediate intracellular calcium buffering, generation of reactive oxygen species (ROS), and apoptosis. Electron leakage from the electron transport chain, especially from damaged or depolarized mitochondria, can generate excess free radicals that damage cellular proteins, DNA, and lipids. Furthermore, mitochondrial damage releases pro-apoptotic factors to initiate cell death. Previous studies have reported that traumatic brain injury (TBI) reduces mitochondrial respiration, enhances production of ROS, and triggers apoptotic cell death, suggesting a prominent role of mitochondria in TBI pathophysiology. Mitochondria maintain cellular energy homeostasis and health via balanced processes of fusion and fission, continuously dividing and fusing to form an interconnected network throughout the cell. An imbalance of these processes, particularly an excess of fission, can be detrimental to mitochondrial function, causing decreased respiration, ROS production, and apoptosis. Mitochondrial fission is regulated by the cytosolic GTPase, dynamin-related protein 1 (Drp1), which translocates to the mitochondrial outer membrane (MOM) to initiate fission. Aberrant Drp1 activity has been linked to excessive mitochondrial fission and neurodegeneration. Measurement of Drp1 levels in purified hippocampal mitochondria showed an increase in TBI animals as compared to sham controls. Analysis of cryo-electron micrographs of these mitochondria also showed that TBI caused an initial increase in the length of hippocampal mitochondria at 24 h post-injury, followed by a significant decrease in length at 72 h. Post-TBI administration of Mitochondrial division inhibitor-1 (Mdivi-1), a pharmacological inhibitor of Drp1, prevented this decrease in mitochondria length. Mdivi-1 treatment also reduced the loss of newborn neurons in the

  15. Signaling mechanisms in cortical axon growth, guidance and branching

    Directory of Open Access Journals (Sweden)

    Katherine eKalil

    2011-09-01

    Full Text Available Precise wiring of cortical circuits during development depends upon axon extension, guidance and branching to appropriate targets. Motile growth cones at axon tips navigate through the nervous system by responding to molecular cues, which modulate signaling pathways within axonal growth cones. Intracellular calcium signaling has emerged as a major transducer of guidance cues but exactly how calcium signaling pathways modify the actin and microtubule cytoskeleton to evoke growth cone behaviors and axon branching is still mysterious. Axons must often pause in their outgrowth while their branches extend into targets. Some evidence suggests a competition between growth of axons and branches but the mechanisms are poorly understood. Since it is difficult to study growing axons deep within the mammalian brain, much of what we know about signaling pathways and cytoskeletal dynamics has come from studies of axonal growth cones, in many cases from non-mammalian species, growing in tissue culture. Consequently it is not well understood how guidance cues relevant to mammalian neural development in vivo signal to the growth cone cytoskeleton during axon outgrowth and guidance. In this review we describe our recent work in dissociated cultures of developing rodent sensorimotor cortex in the context of the current literature on molecular guidance cues, calcium signaling pathways and cytoskeletal dynamics that regulate growth cone behaviors. A major challenge is to relate findings in tissue culture to mechanisms of cortical development in vivo. Toward this goal, we describe our recent work in cortical slices, which preserve the complex cellular and molecular environment of the mammalian brain but allow direct visualization of growth cone behaviors and calcium signaling. Findings from this work suggest that mechanisms regulating axon growth and guidance in dissociated culture neurons also underlie development of cortical connectivity in vivo.

  16. Compartment-dependent mitochondrial alterations in experimental ALS, the effects of mitophagy and mitochondriogenesis.

    Science.gov (United States)

    Natale, Gianfranco; Lenzi, Paola; Lazzeri, Gloria; Falleni, Alessandra; Biagioni, Francesca; Ryskalin, Larisa; Fornai, Francesco

    2015-01-01

    Amyotrophic lateral sclerosis (ALS) is characterized by massive loss of motor neurons. Data from ALS patients and experimental models indicate that mitochondria are severely damaged within dying or spared motor neurons. Nonetheless, recent data indicate that mitochondrial preservation, although preventing motor neuron loss, fails to prolong lifespan. On the other hand, the damage to motor axons plays a pivotal role in determining both lethality and disease course. Thus, in the present article each motor neuron compartment (cell body, central, and peripheral axons) of G93A SOD-1 mice was studied concerning mitochondrial alterations as well as other intracellular structures. We could confirm the occurrence of ALS-related mitochondrial damage encompassing total swelling, matrix dilution and cristae derangement along with non-pathological variations of mitochondrial size and number. However, these alterations occur to a different extent depending on motor neuron compartment. Lithium, a well-known autophagy inducer, prevents most pathological changes. However, the efficacy of lithium varies depending on which motor neuron compartment is considered. Remarkably, some effects of lithium are also evident in wild type mice. Lithium is effective also in vitro, both in cell lines and primary cell cultures from the ventral spinal cord. In these latter cells autophagy inhibition within motor neurons in vitro reproduced ALS pathology which was reversed by lithium. Muscle and glial cells were analyzed as well. Cell pathology was mostly severe within peripheral axons and muscles of ALS mice. Remarkably, when analyzing motor axons of ALS mice a subtotal clogging of axoplasm was described for the first time, which was modified under the effects of lithium. The effects induced by lithium depend on several mechanisms such as direct mitochondrial protection, induction of mitophagy and mitochondriogenesis. In this study, mitochondriogenesis induced by lithium was confirmed in situ by a

  17. Compartment-dependent mitochondrial alterations in experimental ALS, the effects of mitophagy and mitochondriogenesis

    Science.gov (United States)

    Natale, Gianfranco; Lenzi, Paola; Lazzeri, Gloria; Falleni, Alessandra; Biagioni, Francesca; Ryskalin, Larisa; Fornai, Francesco

    2015-01-01

    Amyotrophic lateral sclerosis (ALS) is characterized by massive loss of motor neurons. Data from ALS patients and experimental models indicate that mitochondria are severely damaged within dying or spared motor neurons. Nonetheless, recent data indicate that mitochondrial preservation, although preventing motor neuron loss, fails to prolong lifespan. On the other hand, the damage to motor axons plays a pivotal role in determining both lethality and disease course. Thus, in the present article each motor neuron compartment (cell body, central, and peripheral axons) of G93A SOD-1 mice was studied concerning mitochondrial alterations as well as other intracellular structures. We could confirm the occurrence of ALS-related mitochondrial damage encompassing total swelling, matrix dilution and cristae derangement along with non-pathological variations of mitochondrial size and number. However, these alterations occur to a different extent depending on motor neuron compartment. Lithium, a well-known autophagy inducer, prevents most pathological changes. However, the efficacy of lithium varies depending on which motor neuron compartment is considered. Remarkably, some effects of lithium are also evident in wild type mice. Lithium is effective also in vitro, both in cell lines and primary cell cultures from the ventral spinal cord. In these latter cells autophagy inhibition within motor neurons in vitro reproduced ALS pathology which was reversed by lithium. Muscle and glial cells were analyzed as well. Cell pathology was mostly severe within peripheral axons and muscles of ALS mice. Remarkably, when analyzing motor axons of ALS mice a subtotal clogging of axoplasm was described for the first time, which was modified under the effects of lithium. The effects induced by lithium depend on several mechanisms such as direct mitochondrial protection, induction of mitophagy and mitochondriogenesis. In this study, mitochondriogenesis induced by lithium was confirmed in situ by a

  18. Mitochondrial oxidative function and type 2 diabetes

    DEFF Research Database (Denmark)

    Rabøl, Rasmus; Boushel, Robert; Dela, Flemming

    2006-01-01

    The cause of insulin resistance and type 2 diabetes is unknown. The major part of insulin-mediated glucose disposal takes place in the skeletal muscle, and increased amounts of intramyocellular lipid has been associated with insulin resistance and linked to decreased activity of mitochondrial...... oxidative phosphorylation. This review will cover the present knowledge and literature on the topics of the activity of oxidative enzymes and the electron transport chain (ETC) in skeletal muscle of patients with type 2 diabetes. Different methods of studying mitochondrial function are described, including...... biochemical measurements of oxidative enzyme and electron transport activity, isolation of mitochondria for measurements of respiration, and ATP production and indirect measurements of ATP production using nuclear magnetic resonance (NMR) - spectroscopy. Biochemical markers of mitochondrial content are also...

  19. Strokes in mitochondrial diseases

    Directory of Open Access Journals (Sweden)

    N V Pizova

    2012-01-01

    Full Text Available It is suggested that mitochondrial diseases might be identified in 22—33% of cryptogenic stroke cases in young subjects. The incidence of mitochondrial disorders in patients with stroke is unknown; it is 0.8 to 7.2% according to the data of some authors. The paper gives data on the prevalence, pathogenesis, and clinical manifestations of mitochondrial diseases, such as mitochondrial encephalopathy, lactic acidosis, and stroke-like syndrome (MELAS and insulin-like episodes; myoclonic epilepsy and ragged-red fibers (MERRF syndrome, and Kearns-Sayre syndrome (sporadic multisystem mitochondrial pathology.

  20. Clinical features of diffuse axonal injury

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective: To analyze the mechanism of diffuse axonal injury (DAI) and study the relationship between DAI and brain concussion, brain contusion, and primary brain stem injury.Methods: The clinical data and iconographic characteristics of 56 patients with DAI were analyzed retrospectively.Results: Traffic accidents were the main cause of DAI. Among the 56 cases, 34 were injured for at least twice, and 71.43% of the patients were complicated with contusion.Conclusions: It is considered that DAI is a common pattern of primary brain injury, which is often underestimated. And DAI includes cerebral concussion and primary brain injury, and is often complicated by cerebral cortex contusion. Therefore, it is very simple and practical to divide primary brain injuries into local and diffuse injuries.

  1. Drug-induced mitochondrial neuropathy in children: a conceptual framework for critical windows of development.

    Science.gov (United States)

    Wallace, Kendall B

    2014-09-01

    Mitochondrial disease arises from genetic or nongenetic events that interfere either directly or indirectly with the bioenergetic function of the mitochondrion and manifest clinically in some form of metabolic disorder. In primary mitochondrial disease, the critical molecular target is one or more of the individual subunits of the respiratory complexes or their assembly and incorporation into the inner mitochondrial membrane, whereas with secondary mitochondrial disease the bioenergetic deficits are secondary to effects on targets other than the electron transport chain and oxidative phosphorylation. Primary genetic events include mutations to or altered expression of proteins targeted to the mitochondrial compartment, whether they are encoded by the nuclear or mitochondrial genome. In this review, we emphasize the occurrence of nongenetic mitochondrial disease resulting from therapeutic drug administration, review the broad scope of drugs implicated in affecting specific primary mitochondrial targets, and describe evidence demonstrating critical windows of risk for the developing neonate to drug-induced mitochondrial disease and neuropathy.

  2. Metabolism. AMP-activated protein kinase mediates mitochondrial fission in response to energy stress.

    Science.gov (United States)

    Toyama, Erin Quan; Herzig, Sébastien; Courchet, Julien; Lewis, Tommy L; Losón, Oliver C; Hellberg, Kristina; Young, Nathan P; Chen, Hsiuchen; Polleux, Franck; Chan, David C; Shaw, Reuben J

    2016-01-15

    Mitochondria undergo fragmentation in response to electron transport chain (ETC) poisons and mitochondrial DNA-linked disease mutations, yet how these stimuli mechanistically connect to the mitochondrial fission and fusion machinery is poorly understood. We found that the energy-sensing adenosine monophosphate (AMP)-activated protein kinase (AMPK) is genetically required for cells to undergo rapid mitochondrial fragmentation after treatment with ETC inhibitors. Moreover, direct pharmacological activation of AMPK was sufficient to rapidly promote mitochondrial fragmentation even in the absence of mitochondrial stress. A screen for substrates of AMPK identified mitochondrial fission factor (MFF), a mitochondrial outer-membrane receptor for DRP1, the cytoplasmic guanosine triphosphatase that catalyzes mitochondrial fission. Nonphosphorylatable and phosphomimetic alleles of the AMPK sites in MFF revealed that it is a key effector of AMPK-mediated mitochondrial fission.

  3. Kif5 regulates mitochondrial movement, morphology, function and neuronal survival.

    Science.gov (United States)

    Iworima, Diepiriye G; Pasqualotto, Bryce A; Rintoul, Gordon L

    2016-04-01

    Due to the unique architecture of neurons, trafficking of mitochondria throughout processes to regions of high energetic demand is critical to sustain neuronal health. It has been suggested that compromised mitochondrial trafficking may play a role in neurodegenerative diseases. We evaluated the consequences of disrupted kif5c-mediated mitochondrial trafficking on mitochondrial form and function in primary rat cortical neurons. Morphological changes in mitochondria appeared to be due to remodelling, a phenomenon distinct from mitochondrial fission, which resulted in punctate-shaped mitochondria. We also demonstrated that neurons displaying punctate mitochondria exhibited relatively decreased ROS and increased cellular ATP levels using ROS-sensitive GFP and ATP FRET probes, respectively. Somewhat unexpectedly, neurons overexpressing the dominant negative form of kif5c exhibited enhanced survival following excitotoxicity, suggesting that the impairment of mitochondrial trafficking conferred some form of neuroprotection. However, when neurons were exposed to H2O2, disruption of kif5c exacerbated cell death indicating that the effect on cell viability was dependent on the mode of toxicity. Our results suggest a novel role of kif5c. In addition to mediating mitochondrial transport, kif5c plays a role in the mechanism of regulating mitochondrial morphology. Our results also suggest that kif5c mediated mitochondrial dynamics may play an important role in regulating mitochondrial function and in turn cellular health. Moreover, our studies demonstrate an interesting interplay between the regulation of mitochondrial motility and morphology.

  4. Calpains mediate axonal cytoskeleton disintegration during Wallerian degeneration.

    Science.gov (United States)

    Ma, Marek; Ferguson, Toby A; Schoch, Kathleen M; Li, Jian; Qian, Yaping; Shofer, Frances S; Saatman, Kathryn E; Neumar, Robert W

    2013-08-01

    In both the central nervous system (CNS) and peripheral nervous system (PNS), transected axons undergo Wallerian degeneration. Even though Augustus Waller first described this process after transection of axons in 1850, the molecular mechanisms may be shared, at least in part, by many human diseases. Early pathology includes failure of synaptic transmission, target denervation, and granular disintegration of the axonal cytoskeleton (GDC). The Ca(2+)-dependent protease calpains have been implicated in GDC but causality has not been established. To test the hypothesis that calpains play a causal role in axonal and synaptic degeneration in vivo, we studied transgenic mice that express human calpastatin (hCAST), the endogenous calpain inhibitor, in optic and sciatic nerve axons. Five days after optic nerve transection and 48 h after sciatic nerve transection, robust neurofilament proteolysis observed in wild-type controls was reduced in hCAST transgenic mice. Protection of the axonal cytoskeleton in sciatic nerves of hCAST mice was nearly complete 48 h post-transection. In addition, hCAST expression preserved the morphological integrity of neuromuscular junctions. However, compound muscle action potential amplitudes after nerve transection were similar in wild-type and hCAST mice. These results, in total, provide direct evidence that calpains are responsible for the morphological degeneration of the axon and synapse during Wallerian degeneration.

  5. Local erythropoietin signaling enhances regeneration in peripheral axons.

    Science.gov (United States)

    Toth, C; Martinez, J A; Liu, W Q; Diggle, J; Guo, G F; Ramji, N; Mi, R; Hoke, A; Zochodne, D W

    2008-06-23

    Erythropoietin (EPO) and its receptor (EPO-R), mediate neuroprotection from axonopathy and apoptosis in the peripheral nervous system (PNS). We examined the impact and potential mechanisms of local EPO signaling on regenerating PNS axons in vivo and in vitro. As a consequence of injury, peripheral nerve axons and DRG neurons have a marked increase in the expression of EPO and EPO-R. Local delivery of EPO via conduit over 2 weeks to rat sciatic nerve following crush injury increased the density and maturity of regenerating myelinated axons growing distally from the crush site. In addition, EPO also rescued retrograde degeneration and atrophy of axons. EPO substantially increased the density and intensity of calcitonin gene-related peptide (CGRP) expression within outgrowing axons. Behavioral improvements in sensorimotor function also occurred in rats exposed to near nerve EPO delivery. EPO delivery led to decreased nuclear factor kappaB (NFkB) activation but increased phosphorylation of Akt and STAT3 within nerve and dorsal root ganglia neurons indicating rescue from an injury phenotype. Spinal cord explant studies also demonstrated a similar dose-dependent effect of EPO upon motor axonal outgrowth. Local EPO signaling enhances regenerating peripheral nervous system axons in addition to its known neuroprotection. Exogenous EPO may have a therapeutic role in a large number of peripheral nerve diseases through its impact on regeneration.

  6. Mitochondrial Dysfunction in Lysosomal Storage Disorders

    Directory of Open Access Journals (Sweden)

    Mario de la Mata

    2016-10-01

    Full Text Available Lysosomal storage diseases (LSDs describe a heterogeneous group of rare inherited metabolic disorders that result from the absence or loss of function of lysosomal hydrolases or transporters, resulting in the progressive accumulation of undigested material in lysosomes. The accumulation of substances affects the function of lysosomes and other organelles, resulting in secondary alterations such as impairment of autophagy, mitochondrial dysfunction, inflammation and apoptosis. LSDs frequently involve the central nervous system (CNS, where neuronal dysfunction or loss results in progressive neurodegeneration and premature death. Many LSDs exhibit signs of mitochondrial dysfunction, which include mitochondrial morphological changes, decreased mitochondrial membrane potential (ΔΨm, diminished ATP production and increased generation of reactive oxygen species (ROS. Furthermore, reduced autophagic flux may lead to the persistence of dysfunctional mitochondria. Gaucher disease (GD, the LSD with the highest prevalence, is caused by mutations in the GBA1 gene that results in defective and insufficient activity of the enzyme β-glucocerebrosidase (GCase. Decreased catalytic activity and/or instability of GCase leads to accumulation of glucosylceramide (GlcCer and glucosylsphingosine (GlcSph in the lysosomes of macrophage cells and visceral organs. Mitochondrial dysfunction has been reported to occur in numerous cellular and mouse models of GD. The aim of this manuscript is to review the current knowledge and implications of mitochondrial dysfunction in LSDs.

  7. Axon guidance and neuronal migration research in China

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Proper migration of neuronal somas and axonal growth cones to designated locations in the developing brain is essential for the assembly of functional neuronal circuits.Rapid progress in research of axon guidance and neuronal migration has been made in the last twenty years.Chinese researchers began their exploration in this field ten years ago and have made significant contributions in clarifying the signal transduction of axon guidance and neuronal migration.Several unique experimental approaches,including the migration assay of single isolated neurons in response to locally delivered guidance cues,have been developed by Chinese neuroscientists to investigate the molecular machinery underlying these guidance events.

  8. Mitochondrial helicases and mitochondrial genome maintenance

    DEFF Research Database (Denmark)

    Aamann, Maria Diget; de Souza-Pinto, Nadja C; Kulikowicz, Tomasz;

    2010-01-01

    Helicases are essential enzymes that utilize the energy of nucleotide hydrolysis to drive unwinding of nucleic acid duplexes. Helicases play roles in all aspects of DNA metabolism including DNA repair, DNA replication and transcription. The subcellular locations and functions of several helicases...... have been studied in detail; however, the roles of specific helicases in mitochondrial biology remain poorly characterized. This review presents important recent advances in identifying and characterizing mitochondrial helicases, some of which also operate in the nucleus....

  9. Action potentials initiate in the axon initial segment and propagate through axon collaterals reliably in cerebellar Purkinje neurons.

    Science.gov (United States)

    Foust, Amanda; Popovic, Marko; Zecevic, Dejan; McCormick, David A

    2010-05-19

    Purkinje neurons are the output cells of the cerebellar cortex and generate spikes in two distinct modes, known as simple and complex spikes. Revealing the point of origin of these action potentials, and how they conduct into local axon collaterals, is important for understanding local and distal neuronal processing and communication. By using a recent improvement in voltage-sensitive dye imaging technique that provided exceptional spatial and temporal resolution, we were able to resolve the region of spike initiation as well as follow spike propagation into axon collaterals for each action potential initiated on single trials. All fast action potentials, for both simple and complex spikes, whether occurring spontaneously or in response to a somatic current pulse or synaptic input, initiated in the axon initial segment. At discharge frequencies of less than approximately 250 Hz, spikes propagated faithfully through the axon and axon collaterals, in a saltatory manner. Propagation failures were only observed for very high frequencies or for the spikelets associated with complex spikes. These results demonstrate that the axon initial segment is a critical decision point in Purkinje cell processing and that the properties of axon branch points are adjusted to maintain faithful transmission.

  10. Cardiolipin and mitochondrial cristae organization.

    Science.gov (United States)

    Ikon, Nikita; Ryan, Robert O

    2017-03-20

    A fundamental question in cell biology, under investigation for over six decades, is the structural organization of mitochondrial cristae. Long known to harbor electron transport chain proteins, crista membrane integrity is key to establishment of the proton gradient that drives oxidative phosphorylation. Visualization of cristae morphology by electron microscopy/tomography has provided evidence that cristae are tube-like extensions of the mitochondrial inner membrane (IM) that project into the matrix space. Reconciling ultrastructural data with the lipid composition of the IM provides support for a continuously curved cylindrical bilayer capped by a dome-shaped tip. Strain imposed by the degree of curvature is relieved by an asymmetric distribution of phospholipids in monolayer leaflets that comprise cristae membranes. The signature mitochondrial lipid, cardiolipin (~18% of IM phospholipid mass), and phosphatidylethanolamine (34%) segregate to the negatively curved monolayer leaflet facing the crista lumen while the opposing, positively curved, matrix-facing monolayer leaflet contains predominantly phosphatidylcholine. Associated with cristae are numerous proteins that function in distinctive ways to establish and/or maintain their lipid repertoire and structural integrity. By combining unique lipid components with a set of protein modulators, crista membranes adopt and maintain their characteristic morphological and functional properties. Once established, cristae ultrastructure has a direct impact on oxidative phosphorylation, apoptosis, fusion/fission as well as diseases of compromised energy metabolism.

  11. Altered Mitochondrial Dynamics and TBI Pathophysiology

    Directory of Open Access Journals (Sweden)

    Tara Diane Fischer

    2016-03-01

    Full Text Available Mitochondrial function is intimately linked to cellular survival, growth, and death. Mitochondria not only generate ATP from oxidative phosphorylation, but also mediate intracellular calcium buffering, generation of reactive oxygen species (ROS, and apoptosis. Electron leakage from the electron transport chain, especially from damaged or depolarized mitochondria, can generate excess free radicals that damage cellular proteins, DNA, and lipids. Furthermore, mitochondrial damage releases pro-apoptotic factors to initiate cell death. Previous studies have reported that traumatic brain injury (TBI reduces mitochondrial respiration, enhances production of ROS, and triggers apoptotic cell death, suggesting a prominent role of mitochondria in TBI pathophysiology. Mitochondria maintain cellular energy homeostasis and health via balanced processes of fusion and fission, continuously dividing and fusing to form an interconnected network throughout the cell. An imbalance of these processes, particularly an excess of fission, can be detrimental to mitochondrial function, causing decreased respiration, ROS production, and apoptosis. Mitochondrial fission is regulated by the cytosolic GTPase, dynamin-related protein 1 (Drp1, which translocates to the mitochondrial outer membrane to initiate fission. Aberrant Drp1 activity has been linked to excessive mitochondrial fission and neurodegeneration. Measurement of Drp1 levels in purified hippocampal mitochondria showed an increase in TBI animals as compared to sham controls. Analysis of cryo-electron micrographs of these mitochondria also showed that TBI caused an initial increase in the length of hippocampal mitochondria at 24 hours post-injury, followed by a significant decrease in length at 72 hours. Post-TBI administration of Mdivi-1, a pharmacological inhibitor of Drp1, prevented this decrease in mitochondria length. Mdivi-1 treatment also reduced the loss of newborn neurons in the hippocampus and improved

  12. Npn-1 contributes to axon-axon interactions that differentially control sensory and motor innervation of the limb.

    Directory of Open Access Journals (Sweden)

    Rosa-Eva Huettl

    2011-02-01

    Full Text Available The initiation, execution, and completion of complex locomotor behaviors are depending on precisely integrated neural circuitries consisting of motor pathways that activate muscles in the extremities and sensory afferents that deliver feedback to motoneurons. These projections form in tight temporal and spatial vicinities during development, yet the molecular mechanisms and cues coordinating these processes are not well understood. Using cell-type specific ablation of the axon guidance receptor Neuropilin-1 (Npn-1 in spinal motoneurons or in sensory neurons in the dorsal root ganglia (DRG, we have explored the contribution of this signaling pathway to correct innervation of the limb. We show that Npn-1 controls the fasciculation of both projections and mediates inter-axonal communication. Removal of Npn-1 from sensory neurons results in defasciculation of sensory axons and, surprisingly, also of motor axons. In addition, the tight coupling between these two heterotypic axonal populations is lifted with sensory fibers now leading the spinal nerve projection. These findings are corroborated by partial genetic elimination of sensory neurons, which causes defasciculation of motor projections to the limb. Deletion of Npn-1 from motoneurons leads to severe defasciculation of motor axons in the distal limb and dorsal-ventral pathfinding errors, while outgrowth and fasciculation of sensory trajectories into the limb remain unaffected. Genetic elimination of motoneurons, however, revealed that sensory axons need only minimal scaffolding by motor axons to establish their projections in the distal limb. Thus, motor and sensory axons are mutually dependent on each other for the generation of their trajectories and interact in part through Npn-1-mediated fasciculation before and within the plexus region of the limbs.

  13. Npn-1 contributes to axon-axon interactions that differentially control sensory and motor innervation of the limb.

    Science.gov (United States)

    Huettl, Rosa-Eva; Soellner, Heidi; Bianchi, Elisa; Novitch, Bennett G; Huber, Andrea B

    2011-02-01

    The initiation, execution, and completion of complex locomotor behaviors are depending on precisely integrated neural circuitries consisting of motor pathways that activate muscles in the extremities and sensory afferents that deliver feedback to motoneurons. These projections form in tight temporal and spatial vicinities during development, yet the molecular mechanisms and cues coordinating these processes are not well understood. Using cell-type specific ablation of the axon guidance receptor Neuropilin-1 (Npn-1) in spinal motoneurons or in sensory neurons in the dorsal root ganglia (DRG), we have explored the contribution of this signaling pathway to correct innervation of the limb. We show that Npn-1 controls the fasciculation of both projections and mediates inter-axonal communication. Removal of Npn-1 from sensory neurons results in defasciculation of sensory axons and, surprisingly, also of motor axons. In addition, the tight coupling between these two heterotypic axonal populations is lifted with sensory fibers now leading the spinal nerve projection. These findings are corroborated by partial genetic elimination of sensory neurons, which causes defasciculation of motor projections to the limb. Deletion of Npn-1 from motoneurons leads to severe defasciculation of motor axons in the distal limb and dorsal-ventral pathfinding errors, while outgrowth and fasciculation of sensory trajectories into the limb remain unaffected. Genetic elimination of motoneurons, however, revealed that sensory axons need only minimal scaffolding by motor axons to establish their projections in the distal limb. Thus, motor and sensory axons are mutually dependent on each other for the generation of their trajectories and interact in part through Npn-1-mediated fasciculation before and within the plexus region of the limbs.

  14. Differential Trafficking of Transport Vesicles Contributes to the Localization of Dendritic Proteins

    Directory of Open Access Journals (Sweden)

    Sarmad Al-Bassam

    2012-07-01

    Full Text Available In neurons, transmembrane proteins are targeted to dendrites in vesicles that traffic solely within the somatodendritic compartment. How these vesicles are retained within the somatodendritic domain is unknown. Here, we use a novel pulse-chase system, which allows synchronous release of exogenous transmembrane proteins from the endoplasmic reticulum to follow movements of post-Golgi transport vesicles. Surprisingly, we found that post-Golgi vesicles carrying dendritic proteins were equally likely to enter axons and dendrites. However, once such vesicles entered the axon, they very rarely moved beyond the axon initial segment but instead either halted or reversed direction in an actin and Myosin Va-dependent manner. In contrast, vesicles carrying either an axonal or a nonspecifically localized protein only rarely halted or reversed and instead generally proceeded to the distal axon. Thus, our results are consistent with the axon initial segment behaving as a vesicle filter that mediates the differential trafficking of transport vesicles.

  15. Mitochondrial Biogenesis and Turnover

    OpenAIRE

    Diaz, Francisca; Moraes, Carlos T.

    2008-01-01

    Mitochondrial biogenesis is a complex process involving the coordinated expression of mitochondrial and nuclear genes, the import of the products of the latter into the organelle and turnover. The mechanisms associated with these events have been intensively studied in the last twenty years and our understanding of their details is much improved. Mitochondrial biogenesis requires the participation of calcium signaling that activates a series of calcium dependent protein kinases that in turn a...

  16. Structural plasticity of axon terminals in the adult.

    Science.gov (United States)

    Gogolla, Nadine; Galimberti, Ivan; Caroni, Pico

    2007-10-01

    There is now conclusive evidence for widespread ongoing structural plasticity of presynaptic boutons and axon side-branches in the adult brain. The plasticity complements that of postsynaptic spines, but axonal plasticity samples larger volumes of neuropil, and has a larger impact on circuit remodeling. Axons from distinct neurons exhibit unique ratios of stable (t1/2>9 months) and dynamic (t1/2 5-20 days) boutons, which persist as spatially intermingled subgroups along terminal arbors. In addition, phases of side-branch dynamics mediate larger scale remodeling guided by synaptogenesis. The plasticity is most pronounced during critical periods; its patterns and outcome are controlled by Hebbian mechanisms and intrinsic neuronal factors. Novel experience, skill learning, life-style, and age can persistently modify local circuit structure through axonal structural plasticity.

  17. [Mitochondrial and oocyte development].

    Science.gov (United States)

    Deng, Wei-Ping; Ren, Zhao-Rui

    2007-12-01

    Oocyte development and maturation is a complicated process. The nuclear maturation and cytoplasmic maturation must synchronize which can ensure normal oocyte fertilization and following development. Mitochondrial is the most important cellular organell in cytoplasm, and the variation of its distribution during oocyte maturation, the capacity of OXPHOS generating ATP as well as the content or copy number or transcription level of mitochondrial DNA play an important role in oocyte development and maturation. Therefore, the studies on the variation of mitochondrial distribution, function and mitochondrial DNA could enhance our understanding of the physiology of reproduction and provide new insight to solve the difficulties of assisted reproduction as well as cloning embryo technology.

  18. Progress in mitochondrial epigenetics.

    Science.gov (United States)

    Manev, Hari; Dzitoyeva, Svetlana

    2013-08-01

    Mitochondria, intracellular organelles with their own genome, have been shown capable of interacting with epigenetic mechanisms in at least four different ways. First, epigenetic mechanisms that regulate the expression of nuclear genome influence mitochondria by modulating the expression of nuclear-encoded mitochondrial genes. Second, a cell-specific mitochondrial DNA content (copy number) and mitochondrial activity determine the methylation pattern of nuclear genes. Third, mitochondrial DNA variants influence the nuclear gene expression patterns and the nuclear DNA (ncDNA) methylation levels. Fourth and most recent line of evidence indicates that mitochondrial DNA similar to ncDNA also is subject to epigenetic modifications, particularly by the 5-methylcytosine and 5-hydroxymethylcytosine marks. The latter interaction of mitochondria with epigenetics has been termed 'mitochondrial epigenetics'. Here we summarize recent developments in this particular area of epigenetic research. Furthermore, we propose the term 'mitoepigenetics' to include all four above-noted types of interactions between mitochondria and epigenetics, and we suggest a more restricted usage of the term 'mitochondrial epigenetics' for molecular events dealing solely with the intra-mitochondrial epigenetics and the modifications of mitochondrial genome.

  19. Dynein mutations associated with hereditary motor neuropathies impair mitochondrial morphology and function with age.

    Science.gov (United States)

    Eschbach, Judith; Sinniger, Jérôme; Bouitbir, Jamal; Fergani, Anissa; Schlagowski, Anna-Isabel; Zoll, Joffrey; Geny, Bernard; René, Frédérique; Larmet, Yves; Marion, Vincent; Baloh, Robert H; Harms, Matthew B; Shy, Michael E; Messadeq, Nadia; Weydt, Patrick; Loeffler, Jean-Philippe; Ludolph, Albert C; Dupuis, Luc

    2013-10-01

    Mutations in the DYNC1H1 gene encoding for dynein heavy chain cause two closely related human motor neuropathies, dominant spinal muscular atrophy with lower extremity predominance (SMA-LED) and axonal Charcot-Marie-Tooth (CMT) disease, and lead to sensory neuropathy and striatal atrophy in mutant mice. Dynein is the molecular motor carrying mitochondria retrogradely on microtubules, yet the consequences of dynein mutations on mitochondrial physiology have not been explored. Here, we show that mouse fibroblasts bearing heterozygous or homozygous point mutation in Dync1h1, similar to human mutations, show profoundly abnormal mitochondrial morphology associated with the loss of mitofusin 1. Furthermore, heterozygous Dync1h1 mutant mice display progressive mitochondrial dysfunction in muscle and mitochondria progressively increase in size and invade sarcomeres. As a likely consequence of systemic mitochondrial dysfunction, Dync1h1 mutant mice develop hyperinsulinemia and hyperglycemia and progress to glucose intolerance with age. Similar defects in mitochondrial morphology and mitofusin levels are observed in fibroblasts from patients with SMA-LED. Last, we show that Dync1h1 mutant fibroblasts show impaired perinuclear clustering of mitochondria in response to mitochondrial uncoupling. Our results show that dynein function is required for the maintenance of mitochondrial morphology and function with aging and suggest that mitochondrial dysfunction contributes to dynein-dependent neurological diseases, such as SMA-LED.

  20. Modality-Specific Axonal Regeneration: Towards selective regenerative neural interfaces

    Directory of Open Access Journals (Sweden)

    Parisa eLotfi

    2011-10-01

    Full Text Available Regenerative peripheral nerve interfaces have been proposed as viable alternatives for the natural control of robotic prosthetic devices. However, sensory and motor axons at the neural interface are of mixed submodality types, which difficult the specific recording from motor axons and the eliciting of precise sensory modalities through selective stimulation. Here we evaluated the possibility of using type-specific neurotrophins to preferentially entice the regeneration of defined axonal populations from transected peripheral nerves into separate compartments. Segregation of mixed sensory fibers from dorsal root ganglion neurons was evaluated in vitro by compartmentalized diffusion delivery of nerve growth factor (NGF and neurotrophin-3 (NT-3, to preferentially entice the growth of TrkA+ nociceptive and TrkC+ proprioceptive subsets of sensory neurons, respectively. The average axon length in the NGF channel increased 2.5 fold compared to that in saline or NT-3, whereas the number of branches increased 3 fold in the NT-3 channels. These results were confirmed using a 3-D Y-shaped in vitro assay showing that the arm containing NGF was able to entice a 5-fold increase in axonal length of unbranched fibers. To address if such segregation can be enticed in vivo, a Y-shaped tubing was used to allow regeneration of the transected adult rat sciatic nerve into separate compartments filled with either NFG or NT-3. A significant increase in the number of CGRP+ pain fibers were attracted towards the sural nerve, while N-52+ large diameter axons were observed in the tibial and NT-3 compartments. This study demonstrates the guided enrichment of sensory axons in specific regenerative chambers, and supports the notion that neurotrophic factors can be used to segregate sensory and perhaps motor axons in separate peripheral interfaces.

  1. Electrophysiology of a nonmyelinated glutamatergic axon in rat hippocampus

    OpenAIRE

    Alle, Henrik

    2012-01-01

    The common theme of the presented work on the nonmyelinated hippocampal mossy fiber (the axon of the granule cell in the dentate gyrus) is the generation of subthreshold and suprathreshold electrical signals. Subthreshold depolarizations in the axon can occur due to passive propagation of excitatory postsynaptic potentials, which are generated in the somato-dendritic domain. The remote passive propagation of these comparatively slow but transient signals is due to a space constant...

  2. 6-Sulphated chondroitins have a positive influence on axonal regeneration.

    Directory of Open Access Journals (Sweden)

    Rachel Lin

    Full Text Available Chondroitin sulphate proteoglycans (CSPGs upregulated in the glial scar inhibit axon regeneration via their sulphated glycosaminoglycans (GAGs. Chondroitin 6-sulphotransferase-1 (C6ST-1 is upregulated after injury leading to an increase in 6-sulphated GAG. In this study, we ask if this increase in 6-sulphated GAG is responsible for the increased inhibition within the glial scar, or whether it represents a partial reversion to the permissive embryonic state dominated by 6-sulphated glycosaminoglycans (GAGs. Using C6ST-1 knockout mice (KO, we studied post-injury changes in chondroitin sulphotransferase (CSST expression and the effect of chondroitin 6-sulphates on both central and peripheral axon regeneration. After CNS injury, wild-type animals (WT showed an increase in mRNA for C6ST-1, C6ST-2 and C4ST-1, but KO did not upregulate any CSSTs. After PNS injury, while WT upregulated C6ST-1, KO showed an upregulation of C6ST-2. We examined regeneration of nigrostriatal axons, which demonstrate mild spontaneous axon regeneration in the WT. KO showed many fewer regenerating axons and more axonal retraction than WT. However, in the PNS, repair of the median and ulnar nerves led to similar and normal levels of axon regeneration in both WT and KO. Functional tests on plasticity after the repair also showed no evidence of enhanced plasticity in the KO. Our results suggest that the upregulation of 6-sulphated GAG after injury makes the extracellular matrix more permissive for axon regeneration, and that the balance of different CSs in the microenvironment around the lesion site is an important factor in determining the outcome of nervous system injury.

  3. Fast and reliable identification of axons, axon initial segments and dendrites with local field potential recording

    DEFF Research Database (Denmark)

    Petersen, Anders V.; Johansen, Emil O.; Perrier, Jean-Francois

    2015-01-01

    The axon initial segment (AIS) is an essential neuronal compartment. It is usually where action potentials are initiated. Recent studies demonstrated that the AIS is a plastic structure that can be regulated by neuronal activity and by the activation of metabotropic receptors. Studying the AIS...... of neurons, we can detect sinks caused by inward currents flowing across the membrane. We determine the location of the AIS by comparing the timing of these events with the action potential. We demonstrate that this method allows the unequivocal identification of the AIS of different types of neurons from...

  4. Axon morphology at the lamina cribrosa in monkey eyes.

    Science.gov (United States)

    Radius, R L; Klewin, K M

    1986-01-01

    The eyes of 8 monkeys (Aotus trivirgatus) were studied. The mean cross-section area and the least diameter of axon cylinders were calculated from measurements made by computer assisted planimetry of electron photomicrographs of sections through the optic nerve head at the level of the lamina cribrosa. The density of intrabundle connective tissue and glial cell elements in nerve fiber bundles was also calculated. The mean cross-section area and minimum diameter of axons in the temporal part were less than in the nasal part of the nerve. The values for axons in the superior and inferior parts of the nerve were intermediate. A similar pattern of increasing dimensions was seen in axons from the more axial nerve compared to neurons in the more circumferential nerve sectors. The density of the intrabundle, nonaxonal tissue elements did not differ significantly across the nerve. Although axon dimensions may play some role in defining the vulnerability of neuronal tissue to a pressure insult, the results of this anatomic investigation do not support the hypothesis that differences in axonal distribution by size across the nerve section define the regional vulnerability of the nerve head to elevated intraocular pressure.

  5. Uncovering sensory axonal dysfunction in asymptomatic type 2 diabetic neuropathy.

    Science.gov (United States)

    Sung, Jia-Ying; Tani, Jowy; Chang, Tsui-San; Lin, Cindy Shin-Yi

    2017-01-01

    This study investigated sensory and motor nerve excitability properties to elucidate the development of diabetic neuropathy. A total of 109 type 2 diabetes patients were recruited, and 106 were analyzed. According to neuropathy severity, patients were categorized into G0, G1, and G2+3 groups using the total neuropathy score-reduced (TNSr). Patients in the G0 group were asymptomatic and had a TNSr score of 0. Sensory and motor nerve excitability data from diabetic patients were compared with data from 33 healthy controls. Clinical assessment, nerve conduction studies, and sensory and motor nerve excitability testing data were analyzed to determine axonal dysfunction in diabetic neuropathy. In the G0 group, sensory excitability testing revealed increased stimulus for the 50% sensory nerve action potential (Pmotor excitability only had significantly increased stimulus for the 50% compound motor nerve action potential (Pdevelopment of axonal dysfunction in sensory axons occurred prior to and in a different fashion from motor axons. Additionally, sensory nerve excitability tests can detect axonal dysfunction even in asymptomatic patients. These insights further our understanding of diabetic neuropathy and enable the early detection of sensory axonal abnormalities, which may provide a basis for neuroprotective therapeutic approaches.

  6. Ultrastructural observation of effect of moderate hypothermia on axonal damage in an animal model of diffuse axonal injury

    Institute of Scientific and Technical Information of China (English)

    孙晓川; 唐文渊; 郑履平

    2002-01-01

    Objective: To investigate the effect of moderate hypothermia on responses of axonal cytoskeleton to axonal injury in the acute stage of injury. Methods: Of fifteen adult guinea pigs, twelve animals were subjected to stretch injury to the right optic nerves and divided into the normothermic group (n=6) in which the animal's core temperature was maintained at 36.0-37.5℃ and the hypothermia group (n=6) in which the core temperature was reduced to 32.0-32.5℃ after stretch injury. Remaining three animals sustained no injury to the right optic nerves and served as control group. Half of injured animals (n=3) of either normothermic group or hypothermic group were killed at either 2 hours or 4 hours after injury. The ultrastructural changes of axonal cytoskeleton of the right optic nerve fibers from the animals were examined under a transmission electron microscope and analyzed by quantitative analysis with a computer image analysis system. Results: At 2 hours after stretch injury, there was a significant reduction in the mean number of microtubules (P<0.001), and a significant increase in the mean intermicrotubule spacing (P<0.05 or P<0.01) in axons of all sizes in normothermic animals. The mean number of neurofilaments also decreased statistically (P<0.01) in large and medium subgroups of axons in the same experimental group at 2 hours. By 4 hours, the large subgroup of axons in normothermic animals still demonstrated a significant decline in the mean number of microtubules (P<0.01) and an increase in the mean intermicrotubule spacing (P<0.05), while the medium and small subgroups of axons displayed a significant increase in the mean number of neurofilaments (P<0.05) and reduction in the mean interneurofilament spacing (P<0.05). On the contrary, either the mean number of microtubules and the mean intermicrotubule spacing, or the mean number of neurofilaments and interneurofilament spacing in axons of all sizes in hypothermic stretch-injured animals was not

  7. White matter involvement after TBI: Clues to axon and myelin repair capacity.

    Science.gov (United States)

    Armstrong, Regina C; Mierzwa, Amanda J; Marion, Christina M; Sullivan, Genevieve M

    2016-01-01

    Impact-acceleration forces to the head cause traumatic brain injury (TBI) with damage in white matter tracts comprised of long axons traversing the brain. White matter injury after TBI involves both traumatic axonal injury (TAI) and myelin pathology that evolves throughout the post-injury time course. The axon response to initial mechanical forces and secondary insults follows the process of Wallerian degeneration, which initiates as a potentially reversible phase of intra-axonal damage and proceeds to an irreversible phase of axon fragmentation. Distal to sites of axon disconnection, myelin sheaths remain for prolonged periods, which may activate neuroinflammation and inhibit axon regeneration. In addition to TAI, TBI can cause demyelination of intact axons. These evolving features of axon and myelin pathology also represent opportunities for repair. In experimental TBI, demyelinated axons exhibit remyelination, which can serve to both protect axons and facilitate recovery of function. Myelin remodeling may also contribute to neuroplasticity. Efficient clearance of myelin debris is a potential target to attenuate the progression of chronic pathology. During the early phase of Wallerian degeneration, interventions that prevent the transition from reversible damage to axon disconnection warrant the highest priority, based on the poor regenerative capacity of axons in the CNS. Clinical evaluation of TBI will need to address the challenge of accurately detecting the extent and stage of axon damage. Distinguishing the complex white matter changes associated with axons and myelin is necessary for interpreting advanced neuroimaging approaches and for identifying a broader range of therapeutic opportunities to improve outcome after TBI.

  8. Mitochondrial network energetics in the heart.

    Science.gov (United States)

    Aon, Miguel A; Cortassa, Sonia

    2012-01-01

    At the core of eukaryotic aerobic life, mitochondrial function like 'hubs' in the web of energetic and redox processes in cells. In the heart, these networks-extending beyond the complex connectivity of biochemical circuit diagrams and apparent morphology-exhibit collective dynamics spanning several spatiotemporal levels of organization, from the cell, to the tissue, and the organ. The network function of mitochondria, i.e., mitochondrial network energetics, represents an advantageous behavior. Its coordinated action, under normal physiology, provides robustness despite failure in a few nodes, and improves energy supply toward a swiftly changing demand. Extensive diffuse loops, encompassing mitochondrial-cytoplasmic reaction/transport networks, control and regulate energy supply and demand in the heart. Under severe energy crises, the network behavior of mitochondria and associated glycolytic and other metabolic networks collapse, thereby triggering fatal arrhythmias.

  9. Genetic analyses of roundabout (ROBO) axon guidance receptors in autism.

    Science.gov (United States)

    Anitha, A; Nakamura, Kazuhiko; Yamada, Kazuo; Suda, Shiro; Thanseem, Ismail; Tsujii, Masatsugu; Iwayama, Yoshimi; Hattori, Eiji; Toyota, Tomoko; Miyachi, Taishi; Iwata, Yasuhide; Suzuki, Katsuaki; Matsuzaki, Hideo; Kawai, Masayoshi; Sekine, Yoshimoto; Tsuchiya, Kenji; Sugihara, Gen-Ichi; Ouchi, Yasuomi; Sugiyama, Toshiro; Koizumi, Keita; Higashida, Haruhiro; Takei, Nori; Yoshikawa, Takeo; Mori, Norio

    2008-10-05

    Autism is a pervasive developmental disorder diagnosed in early childhood. Abnormalities of serotonergic neurotransmission have been reported in autism. Serotonin transporter (SERT) modulates serotonin levels, and is a major therapeutic target in autism. Factors that regulate SERT expression might be implicated in the pathophysiology of autism. One candidate SERT regulatory protein is the roundabout axon guidance molecule, ROBO. SerT expression in Drosophila is regulated by robo; it plays a vital role in mammalian neurodevelopment also. Here, we examined the associations of ROBO3 and ROBO4 with autism, in a trio association study using DNA from 252 families recruited to AGRE. Four SNPs of ROBO3 (rs3923890, P = 0.023; rs7925879, P = 0.017; rs4606490, P = 0.033; and rs3802905, P = 0.049) and a single SNP of ROBO4 (rs6590109, P = 0.009) showed associations with autism; the A/A genotype of rs3923890 showed lower ADI-R_A scores, which reflect social interaction. Significant haplotype associations were also observed for ROBO3 and ROBO4. We further compared the mRNA expressions of ROBO1, ROBO2, ROBO3, and ROBO4 in the lymphocytes of 19 drug-naïve autistic patients and 20 age- and sex-matched controls. Expressions of ROBO1 (P = 0.018) and ROBO2 (P = 0.023) were significantly reduced in the autistic group; the possibility of using the altered expressions of ROBO as peripheral markers for autism, may be explored. In conclusion, we suggest a possible role of ROBO in the pathogenesis of autism. Abnormalities of ROBO may lead to autism either by interfering with serotonergic system, or by disrupting neurodevelopment. To the best of our knowledge, this is the first report relating ROBO with autism.

  10. Defects of mitochondrial DNA replication.

    Science.gov (United States)

    Copeland, William C

    2014-09-01

    Mitochondrial DNA is replicated by DNA polymerase γ in concert with accessory proteins such as the mitochondrial DNA helicase, single-stranded DNA binding protein, topoisomerase, and initiating factors. Defects in mitochondrial DNA replication or nucleotide metabolism can cause mitochondrial genetic diseases due to mitochondrial DNA deletions, point mutations, or depletion, which ultimately cause loss of oxidative phosphorylation. These genetic diseases include mitochondrial DNA depletion syndromes such as Alpers or early infantile hepatocerebral syndromes, and mitochondrial DNA deletion disorders, such as progressive external ophthalmoplegia, ataxia-neuropathy, or mitochondrial neurogastrointestinal encephalomyopathy. This review focuses on our current knowledge of genetic defects of mitochondrial DNA replication (POLG, POLG2, C10orf2, and MGME1) that cause instability of mitochondrial DNA and mitochondrial disease.

  11. Axonal synapses utilize multiple synaptic ribbons in the mammalian retina.

    Directory of Open Access Journals (Sweden)

    Hong-Lim Kim

    Full Text Available In the mammalian retina, bipolar cells and ganglion cells which stratify in sublamina a of the inner plexiform layer (IPL show OFF responses to light stimuli while those that stratify in sublamina b show ON responses. This functional relationship between anatomy and physiology is a key principle of retinal organization. However, there are at least three types of retinal neurons, including intrinsically photosensitive retinal ganglion cells (ipRGCs and dopaminergic amacrine cells, which violate this principle. These cell types have light-driven ON responses, but their dendrites mainly stratify in sublamina a of the IPL, the OFF sublayer. Recent anatomical studies suggested that certain ON cone bipolar cells make axonal or ectopic synapses as they descend through sublamina a, thus providing ON input to cells which stratify in the OFF sublayer. Using immunoelectron microscopy with 3-dimensional reconstruction, we have identified axonal synapses of ON cone bipolar cells in the rabbit retina. Ten calbindin ON cone bipolar axons made en passant ribbon synapses onto amacrine or ganglion dendrites in sublamina a of the IPL. Compared to the ribbon synapses made by bipolar terminals, these axonal ribbon synapses were characterized by a broad postsynaptic element that appeared as a monad and by the presence of multiple short synaptic ribbons. These findings confirm that certain ON cone bipolar cells can provide ON input to amacrine and ganglion cells whose dendrites stratify in the OFF sublayer via axonal synapses. The monadic synapse with multiple ribbons may be a diagnostic feature of the ON cone bipolar axonal synapse in sublamina a. The presence of multiple ribbons and a broad postsynaptic density suggest these structures may be very efficient synapses. We also identified axonal inputs to ipRGCs with the architecture described above.

  12. Control mechanisms in mitochondrial oxidative phosphorylation

    Institute of Scientific and Technical Information of China (English)

    Jana Hroudová; Zdeněk Fi(s)ar

    2013-01-01

    Distribution and activity of mitochondria are key factors in neuronal development, synaptic plasticity and axogenesis. The majority of energy sources, necessary for cellular functions, originate from oxidative phosphorylation located in the inner mitochondrial membrane. The adenosine-5'- triphosphate production is regulated by many control mechanism–firstly by oxygen, substrate level, adenosine-5'-diphosphate level, mitochondrial membrane potential, and rate of coupling and proton leak. Recently, these mechanisms have been implemented by "second control mechanisms," such as reversible phosphorylation of the tricarboxylic acid cycle enzymes and electron transport chain complexes, allosteric inhibition of cytochrome c oxidase, thyroid hormones, effects of fatty acids and uncoupling proteins. Impaired function of mitochondria is implicated in many diseases ranging from mitochondrial myopathies to bipolar disorder and schizophrenia. Mitochondrial dysfunctions are usually related to the ability of mitochondria to generate adenosine-5'-triphosphate in response to energy demands. Large amounts of reactive oxygen species are released by defective mitochondria, similarly, decline of antioxidative enzyme activities (e.g. in the elderly) enhances reactive oxygen species production. We reviewed data concerning neuroplasticity, physiology, and control of mitochondrial oxidative phosphorylation and reactive oxygen species production.

  13. Erythropoietin treatment enhances muscle mitochondrial capacity in humans

    DEFF Research Database (Denmark)

    Plenge, Ulla; Belhage, Bo; Guadalupe-Grau, Amelia;

    2012-01-01

    Erythropoietin (Epo) treatment has been shown to induce mitochondrial biogenesis in cardiac muscle along with enhanced mitochondrial capacity in mice. We hypothesized that recombinant human Epo (rhEpo) treatment enhances skeletal muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity...... in humans. In six healthy volunteers rhEpo was administered by sub-cutaneous injection over 8 weeks with oral iron (100 mg) supplementation taken daily. Mitochondrial OXPHOS was quantified by high-resolution respirometry in saponin-permeabilized muscle fibers obtained from biopsies of the vastus lateralis...... before and after rhEpo treatment. OXPHOS was determined with the mitochondrial complex I substrates malate, glutamate, pyruvate, and complex II substrate succinate in the presence of saturating ADP concentrations, while maximal electron transport capacity (ETS) was assessed by addition of an uncoupler...

  14. Ciliary neurotrophic factor reverses aberrant mitochondrial bioenergetics through the JAK/STAT pathway in cultured sensory neurons derived from streptozotocin-induced diabetic rodents.

    Science.gov (United States)

    Chowdhury, Subir Roy; Saleh, Ali; Akude, Eli; Smith, Darrell R; Morrow, Dwane; Tessler, Lori; Calcutt, Nigel A; Fernyhough, Paul

    2014-07-01

    Mitochondrial dysfunction occurs in sensory neurons and contributes to diabetic neuropathy. Ciliary neurotrophic factor (CNTF) stimulates axon regeneration in type 1 diabetic rodents and prevents deficits in axonal caliber, nerve conduction, and thermal sensation. We tested the hypothesis that CNTF enhances sensory neuron function in diabetes through JAK/STAT (Janus kinase/signal transducers and activators of transcription) signaling to normalize impaired mitochondrial bioenergetics. The effect of CNTF on gene expression and neurite outgrowth of cultured adult dorsal root ganglia (DRG) sensory neurons derived from control and streptozotocin (STZ)-induced diabetic rodents was quantified. Polarization status and bioenergetics profile of mitochondria from cultured sensory neurons were determined. CNTF treatment prevented reduced STAT3 phosphorylation (Tyr 705) in DRG of STZ-diabetic mice and also enhanced STAT3 phosphorylation in rat DRG cultures. CNTF normalized polarization status of the mitochondrial inner membrane and corrected the aberrant oligomycin-induced mitochondrial hyperpolarization in axons of diabetic neurons. The mitochondrial bioenergetics profile demonstrated that spare respiratory capacity and respiratory control ratio were significantly depressed in sensory neurons cultured from STZ-diabetic rats and were corrected by acute CNTF treatment. The positive effects of CNTF on neuronal mitochondrial function were significantly inhibited by the specific JAK inhibitor, AG490. Neurite outgrowth of sensory neurons from age-matched control and STZ-induced diabetic rats was elevated by CNTF and blocked by AG490. We propose that CNTF's ability to enhance axon regeneration and protect from fiber degeneration in diabetes is associated with its targeting of mitochondrial function and improvement of cellular bioenergetics, in part, through JAK/STAT signaling.

  15. Myelinated sensory and alpha motor axon regeneration in peripheral nerve neuromas

    Science.gov (United States)

    Macias, M. Y.; Lehman, C. T.; Sanger, J. R.; Riley, D. A.

    1998-01-01

    Histochemical staining for carbonic anhydrase and cholinesterase (CE) activities was used to analyze sensory and motor axon regeneration, respectively, during neuroma formation in transected and tube-encapsulated peripheral nerves. Median-ulnar and sciatic nerves in the rodent model permitted testing whether a 4 cm greater distance of the motor neuron soma from axotomy site or intrinsic differences between motor and sensory neurons influenced regeneration and neuroma formation 10, 30, and 90 days later. Ventral root radiculotomy confirmed that CE-stained axons were 97% alpha motor axons. Distance significantly delayed axon regeneration. When distance was negligible, sensory axons grew out sooner than motor axons, but motor axons regenerated to a greater quantity. These results indicate regeneration differences between axon subtypes and suggest more extensive branching of motor axons within the neuroma. Thus, both distance from injury site to soma and inherent motor and sensory differences should be considered in peripheral nerve repair strategies.

  16. Schwann cell-derived exosomes enhance axonal regeneration in the peripheral nervous system.

    Science.gov (United States)

    Lopez-Verrilli, María Alejandra; Picou, Frederic; Court, Felipe A

    2013-11-01

    Axonal regeneration in the peripheral nervous system is greatly supported by Schwann cells (SCs). After nerve injury, SCs dedifferentiate to a progenitor-like state and efficiently guide axons to their original target tissues. Contact and soluble factors participate in the crosstalk between SCs and axons during axonal regeneration. Here we show that dedifferentiated SCs secrete nano-vesicles known as exosomes which are specifically internalized by axons. Surprisingly, SC-derived exosomes markedly increase axonal regeneration in vitro and enhance regeneration after sciatic nerve injury in vivo. Exosomes shift the growth cone morphology to a pro-regenerating phenotype and decrease the activity of the GTPase RhoA, involved in growth cone collapse and axon retraction. Altogether, our work identifies a novel mechanism by which SCs communicate with neighboring axons during regenerative processes. We propose that SC exosomes represent an important mechanism by which these cells locally support axonal maintenance and regeneration after nerve damage.

  17. LKB1 Regulates Mitochondria-Dependent Presynaptic Calcium Clearance and Neurotransmitter Release Properties at Excitatory Synapses along Cortical Axons.

    Directory of Open Access Journals (Sweden)

    Seok-Kyu Kwon

    2016-07-01

    Full Text Available Individual synapses vary significantly in their neurotransmitter release properties, which underlie complex information processing in neural circuits. Presynaptic Ca2+ homeostasis plays a critical role in specifying neurotransmitter release properties, but the mechanisms regulating synapse-specific Ca2+ homeostasis in the mammalian brain are still poorly understood. Using electrophysiology and genetically encoded Ca2+ sensors targeted to the mitochondrial matrix or to presynaptic boutons of cortical pyramidal neurons, we demonstrate that the presence or absence of mitochondria at presynaptic boutons dictates neurotransmitter release properties through Mitochondrial Calcium Uniporter (MCU-dependent Ca2+ clearance. We demonstrate that the serine/threonine kinase LKB1 regulates MCU expression, mitochondria-dependent Ca2+ clearance, and thereby, presynaptic release properties. Re-establishment of MCU-dependent mitochondrial Ca2+ uptake at glutamatergic synapses rescues the altered neurotransmitter release properties characterizing LKB1-null cortical axons. Our results provide novel insights into the cellular and molecular mechanisms whereby mitochondria control neurotransmitter release properties in a bouton-specific way through presynaptic Ca2+ clearance.

  18. LKB1 Regulates Mitochondria-Dependent Presynaptic Calcium Clearance and Neurotransmitter Release Properties at Excitatory Synapses along Cortical Axons

    Science.gov (United States)

    Kwon, Seok-Kyu; Sando, Richard; Maximov, Anton; Polleux, Franck

    2016-01-01

    Individual synapses vary significantly in their neurotransmitter release properties, which underlie complex information processing in neural circuits. Presynaptic Ca2+ homeostasis plays a critical role in specifying neurotransmitter release properties, but the mechanisms regulating synapse-specific Ca2+ homeostasis in the mammalian brain are still poorly understood. Using electrophysiology and genetically encoded Ca2+ sensors targeted to the mitochondrial matrix or to presynaptic boutons of cortical pyramidal neurons, we demonstrate that the presence or absence of mitochondria at presynaptic boutons dictates neurotransmitter release properties through Mitochondrial Calcium Uniporter (MCU)-dependent Ca2+ clearance. We demonstrate that the serine/threonine kinase LKB1 regulates MCU expression, mitochondria-dependent Ca2+ clearance, and thereby, presynaptic release properties. Re-establishment of MCU-dependent mitochondrial Ca2+ uptake at glutamatergic synapses rescues the altered neurotransmitter release properties characterizing LKB1-null cortical axons. Our results provide novel insights into the cellular and molecular mechanisms whereby mitochondria control neurotransmitter release properties in a bouton-specific way through presynaptic Ca2+ clearance. PMID:27429220

  19. Subtypes of GABAergic neurons project axons in the neocortex

    Directory of Open Access Journals (Sweden)

    Shigeyoshi Higo

    2009-11-01

    Full Text Available γ-aminobutyric acid (GABAergic neurons in the neocortex have been regarded as interneurons and speculated to modulate the activity of neurons locally. Recently, however, several experiments revealed that neuronal nitric oxide synthase (nNOS-positive GABAergic neurons project cortico-cortically with long axons. In this study, we illustrate Golgi-like images of the nNOS-positive GABAergic neurons using a nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d reaction and follow the emanating axon branches in cat brain sections. These axon branches projected cortico-cortically with other non-labeled arcuate fibers, contra-laterally via the corpus callosum and anterior commissure. The labeled fibers were not limited to the neocortex but found also in the fimbria of the hippocampus. In order to have additional information on these GABAergic neuron projections, we investigated green fluorescent protein (GFP-labeled GABAergic neurons in GAD67-Cre knock-in / GFP Cre-reporter mice. GFP-labeled axons emanate densely, especially in the fimbria, a small number in the anterior commissure, and very sparsely in the corpus callosum. These two different approaches confirm that not only nNOS-positive GABAergic neurons but also other subtypes of GABAergic neurons project long axons in the cerebral cortex and are in a position to be involved in information processing.

  20. A novel technique using hydrophilic polymers to promote axonal fusion

    Directory of Open Access Journals (Sweden)

    Ravinder Bamba

    2016-01-01

    Full Text Available The management of traumatic peripheral nerve injury remains a considerable concern for clinicians. With minimal innovations in surgical technique and a limited number of specialists trained to treat peripheral nerve injury, outcomes of surgical intervention have been unpredictable. The inability to manipulate the pathophysiology of nerve injury (i.e., Wallerian degeneration has left scientists and clinicians depending on the slow and lengthy process of axonal regeneration (~1 mm/day. When axons are severed, the endings undergo calcium-mediated plasmalemmal sealing, which limits the ability of the axon to be primarily repaired. Polythethylene glycol (PEG in combination with a bioengineered process overcomes the inability to fuse axons. The mechanism for PEG axonal fusion is not clearly understood, but multiple studies have shown that a providing a calcium-free environment is essential to the process known as PEG fusion. The proposed mechanism is PEG-induced lipid bilayer fusion by removing the hydration barrier surrounding the axolemma and reducing the activation energy required for membrane fusion to occur. This review highlights PEG fusion, its past and current studies, and future directions in PEG fusion.

  1. A novel technique using hydrophilic polymers to promote axonal fusion

    Institute of Scientific and Technical Information of China (English)

    Ravinder Bamba; D Colton Riley; Nathaniel D Kelm; Mark D Does; Richard D Dortch; Wesley P hTayer

    2016-01-01

    The management of traumatic peripheral nerve injury remains a considerable concern for clinicians. With minimal innovations in surgical technique and a limited number of specialists trained to treat peripheral nerve injury, outcomes of surgical intervention have been unpredictable. The inability to manipulate the pathophysiology of nerve injury (i.e., Wallerian degeneration) has left scientists and clinicians depending on the slow and lengthy process of axonal regeneration (~1 mm/day). When axons are severed, the endings undergo calcium-mediated plasmalemmal sealing, which limits the ability of the axon to be primarily re-paired. Polythethylene glycol (PEG) in combination with a bioengineered process overcomes the inability to fuse axons. The mechanism for PEG axonal fusion is not clearly understood, but multiple studies have shown that a providing a calcium-free environment is essential to the process known as PEG fusion. The proposed mechanism is PEG-induced lipid bilayer fusion by removing the hydration barrier surrounding the axolemma and reducing the activation energy required for membrane fusion to occur. This review highlights PEG fusion, its past and current studies, and future directions in PEG fusion.

  2. Calpain Inhibition Reduces Axolemmal Leakage in Traumatic Axonal Injury

    Directory of Open Access Journals (Sweden)

    János Sándor

    2009-12-01

    Full Text Available Calcium-induced, calpain-mediated proteolysis (CMSP has recently been implicated to the pathogenesis of diffuse (traumatic axonal injury (TAI. Some studies suggested that subaxolemmal CMSP may contribute to axolemmal permeability (AP alterations observed in TAI. Seeking direct evidence for this premise we investigated whether subaxolemmal CMSP may contribute to axolemmal permeability alterations (APA and pre-injury calpain-inhibition could reduce AP in a rat model of TAI. Horseradish peroxidase (HRP, a tracer that accumulates in axons with APA was administered one hour prior to injury into the lateral ventricle; 30 min preinjury a single tail vein bolus injection of 30 mg/kg MDL-28170 (a calpain inhibitor or its vehicle was applied in Wistar rats exposed to impact acceleration brain injury. Histological detection of traumatically injured axonal segments accumulating HRP and statistical analysis revealed that pre-injury administration of the calpain inhibitor MDL-28170 significantly reduced the average length of HRP-labeled axonal segments. The axono-protective effect of pre-injury calpain inhibition recently demonstrated with classical immunohistochemical markers of TAI was further corroborated in this experiment; significant reduction of the length of labeled axons in the drug-treated rats implicate CMSP in the progression of altered AP in TAI.

  3. Functional complexity of the axonal growth cone: a proteomic analysis.

    Directory of Open Access Journals (Sweden)

    Adriana Estrada-Bernal

    Full Text Available The growth cone, the tip of the emerging neurite, plays a crucial role in establishing the wiring of the developing nervous system. We performed an extensive proteomic analysis of axonal growth cones isolated from the brains of fetal Sprague-Dawley rats. Approximately 2000 proteins were identified at ≥ 99% confidence level. Using informatics, including functional annotation cluster and KEGG pathway analysis, we found great diversity of proteins involved in axonal pathfinding, cytoskeletal remodeling, vesicular traffic and carbohydrate metabolism, as expected. We also found a large and complex array of proteins involved in translation, protein folding, posttranslational processing, and proteasome/ubiquitination-dependent degradation. Immunofluorescence studies performed on hippocampal neurons in culture confirmed the presence in the axonal growth cone of proteins representative of these processes. These analyses also provide evidence for rough endoplasmic reticulum and reveal a reticular structure equipped with Golgi-like functions in the axonal growth cone. Furthermore, Western blot revealed the growth cone enrichment, relative to fetal brain homogenate, of some of the proteins involved in protein synthesis, folding and catabolism. Our study provides a resource for further research and amplifies the relatively recently developed concept that the axonal growth cone is equipped with proteins capable of performing a highly diverse range of functions.

  4. Mitochondrial gene therapy augments mitochondrial physiology in a Parkinson's disease cell model.

    Science.gov (United States)

    Keeney, Paula M; Quigley, Caitlin K; Dunham, Lisa D; Papageorge, Christina M; Iyer, Shilpa; Thomas, Ravindar R; Schwarz, Kathleen M; Trimmer, Patricia A; Khan, Shaharyar M; Portell, Francisco R; Bergquist, Kristen E; Bennett, James P

    2009-08-01

    Neurodegeneration in Parkinson's disease (PD) affects mainly dopaminergic neurons in the substantia nigra, where age-related, increasing percentages of cells lose detectable respiratory activity associated with depletion of intact mitochondrial DNA (mtDNA). Replenishment of mtDNA might improve neuronal bioenergetic function and prevent further cell death. We developed a technology ("ProtoFection") that uses recombinant human mitochondrial transcription factor A (TFAM) engineered with an N-terminal protein transduction domain (PTD) followed by the SOD2 mitochondrial localization signal (MLS) to deliver mtDNA cargo to the mitochondria of living cells. MTD-TFAM (MTD = PTD + MLS = "mitochondrial transduction domain") binds mtDNA and rapidly transports it across plasma membranes to mitochondria. For therapeutic proof-of-principle we tested ProtoFection technology in Parkinson's disease cybrid cells, using mtDNA generated from commercially available human genomic DNA (gDNA; Roche). Nine to 11 weeks after single exposures to MTD-TFAM + mtDNA complex, PD cybrid cells with impaired respiration and reduced mtDNA genes increased their mtDNA gene copy numbers up to 24-fold, mtDNA-derived RNAs up to 35-fold, TFAM and ETC proteins, cell respiration, and mitochondrial movement velocities. Cybrid cells with no or minimal basal mitochondrial impairments showed reduced or no responses to treatment, suggesting the possibility of therapeutic selectivity. Exposure of PD but not control cybrid cells to MTD-TFAM protein alone or MTD-TFAM + mtDNA complex increased expression of PGC-1alpha, suggesting activation of mitochondrial biogenesis. ProtoFection technology for mitochondrial gene therapy holds promise for improving bioenergetic function in impaired PD neurons and needs additional development to define its pharmacodynamics and delineate its molecular mechanisms. It also is unclear whether single-donor gDNA for generating mtDNA would be a preferred therapeutic compared with the pooled

  5. Axonal sorting of Kir3.3 defines a GABA-containing neuron in the CA3 region of rodent hippocampus.

    Science.gov (United States)

    Grosse, Gisela; Eulitz, Dirk; Thiele, Theodor; Pahner, Ingrid; Schröter, Sascha; Takamori, Shigeo; Grosse, Johannes; Wickman, Kevin; Tapp, Rosemarie; Veh, Rüdiger W; Ottersen, Ole Petter; Ahnert-Hilger, Gudrun

    2003-11-01

    Hippocampal interneurons comprise a heterogeneous group of locally acting GABAergic neurons. In addition to their variability in cotransmitter content and receptor profile, they express a variety of potassium channels that specify their individual properties. Here we describe a new type of large GABA-containing neuron in rodent hippocampus that is characterized by an axonal sorting of the potassium channel Kir3.3. The parent cell bodies of the Kir3.3-positive axons are located in CA3, as assessed by primary cultures derived from hippocampal subareas. At postnatal day 14 these neurons appear at the border between stratum oriens and stratum pyramidale of CA3, from where their axons pass through stratum pyramidale to join the mossy fiber tract. In adult hippocampus, high levels of Kir3.3 channel protein exist in axons that run with the mossy fiber tract. Kir3.3 and the vesicular GABA transporter could be identified in subpopulations of large synaptic terminals that probably derive from Kir3.3 neurons. Axonal sorting of Kir3.3 appears to be typical of a group of large inhibitory neurons, including Purkinje cells and a novel type of interneuron in CA3. Kir3.3 neurons might modulate the activity of CA3 circuitries and consequently memory processing in the hippocampus.

  6. Measurement of mitochondrial NADH and FAD autofluorescence in live cells.

    Science.gov (United States)

    Bartolomé, Fernando; Abramov, Andrey Y

    2015-01-01

    In the process of energy production, mitochondrial networks are key elements to allow metabolism of substrates into ATP. Many pathological conditions have been associated with mitochondrial dysfunction as mitochondria are associated with a wide range of cellular processes. Therefore, any disruption in the energy production induces devastating effects that can ultimately lead to cell death due to chemical ischemia. To address the mitochondrial health and function, there are several bioenergetic parameters reflecting either whole mitochondrial functionality or individual mitochondrial complexes. Particularly, metabolism of nutrients in the tricarboxylic acid cycle provides substrates used to generate electron carriers (nicotinamide adenine dinucleotide [NADH] and flavin adenine dinucleotide [FADH2]) which ultimately donate electrons to the mitochondrial electron transport chain. The levels of NADH and FADH2 can be estimated through imaging of NADH/NAD(P)H or FAD autofluorescence. This report demonstrates how to perform and analyze NADH/NAD(P)H and FAD autofluorescence in a time-course-dependent manner and provides information about NADH and FAD redox indexes both reflecting the activity of the mitochondrial electron transport chain (ETC). Furthermore, total pools of NADH and FAD can be estimated providing information about the rate of substrate supply into the ETC. Finally, the analysis of NADH autofluorescence after induction of maximal respiration can offer information about the pentose phosphate pathway activity where glucose can be alternatively oxidized instead of pyruvate.

  7. Impaired mitochondrial function in human placenta with increased maternal adiposity.

    Science.gov (United States)

    Mele, James; Muralimanoharan, Sribalasubashini; Maloyan, Alina; Myatt, Leslie

    2014-09-01

    The placenta plays a key role in regulation of fetal growth and development and in mediating in utero developmental programming. Obesity, which is associated with chronic inflammation and mitochondrial dysfunction in many tissues, exerts a programming effect in pregnancy. We determined the effect of increasing maternal adiposity and of fetal sex on placental ATP generation, mitochondrial biogenesis, expression of electron transport chain subunits, and mitochondrial function in isolated trophoblasts. Placental tissue was collected from women with prepregnancy BMI ranging from 18.5 to 45 following C-section at term with no labor. Increasing maternal adiposity was associated with excessive production of reactive oxygen species and a significant reduction in placental ATP levels in placentae with male and female fetuses. To explore the potential mechanism of placental mitochondrial dysfunction, levels of transcription factors regulating the expression of genes involved in electron transport and mitochondrial biogenesis were measured. Our in vitro studies showed significant reduction in mitochondrial respiration in cultured primary trophoblasts with increasing maternal obesity along with an abnormal metabolic flexibility of these cells. This reduction in placental mitochondrial respiration in pregnancies complicated by maternal obesity could compromise placental function and potentially underlie the increased susceptibility of these pregnancies to fetal demise in late gestation and to developmental programming.

  8. Selective Inhibition of Deactivated Mitochondrial Complex I by Biguanides †

    OpenAIRE

    2015-01-01

    Biguanides are widely used antihyperglycemic agents for diabetes mellitus and prediabetes treatment. Complex I is the rate limiting step of the mitochondrial electron transport chain (ETC), a major source of mitochondrial free radical production, and a known target of biguanides. Complex I has two reversible conformational states, active and de-active. The deactivated state is promoted in the absence of substrates, but is rapidly and fully reversed to the active state in the presence of NADH....

  9. Searching for the elusive mitochondrial longevity signal in C. elegans.

    Science.gov (United States)

    Bennett, Christopher F; Choi, Haeri; Kaeberlein, Matt

    2014-01-01

    There is a growing list of examples where perturbed mitochondrial function is associated with increased longevity, yet the exact mechanisms have remained elusive. This phenomenon was first documented, and has been studied most extensively, in C. elegans. One prominent model proposed that lifespan extension resulting from electron transport chain inhibition is due to induction of the mitochondrial unfolded protein response. This model requires revision in light of recent data showing that the mitochondrial unfolded protein response, as defined by the field, is neither necessary nor sufficient for lifespan extension in C. elegans. Several additional factors have been proposed to underlie this lifespan extension, which is likely to be multifactorial and complex.

  10. Vimar Is a Novel Regulator of Mitochondrial Fission through Miro

    Science.gov (United States)

    Ding, Lianggong; Han, Yanping; Li, Yuhong; Ji, Xunming; Liu, Lei

    2016-01-01

    As fundamental processes in mitochondrial dynamics, mitochondrial fusion, fission and transport are regulated by several core components, including Miro. As an atypical Rho-like small GTPase with high molecular mass, the exchange of GDP/GTP in Miro may require assistance from a guanine nucleotide exchange factor (GEF). However, the GEF for Miro has not been identified. While studying mitochondrial morphology in Drosophila, we incidentally observed that the loss of vimar, a gene encoding an atypical GEF, enhanced mitochondrial fission under normal physiological conditions. Because Vimar could co-immunoprecipitate with Miro in vitro, we speculated that Vimar might be the GEF of Miro. In support of this hypothesis, a loss-of-function (LOF) vimar mutant rescued mitochondrial enlargement induced by a gain-of-function (GOF) Miro transgene; whereas a GOF vimar transgene enhanced Miro function. In addition, vimar lost its effect under the expression of a constitutively GTP-bound or GDP-bound Miro mutant background. These results indicate a genetic dependence of vimar on Miro. Moreover, we found that mitochondrial fission played a functional role in high-calcium induced necrosis, and a LOF vimar mutant rescued the mitochondrial fission defect and cell death. This result can also be explained by vimar's function through Miro, because Miro’s effect on mitochondrial morphology is altered upon binding with calcium. In addition, a PINK1 mutant, which induced mitochondrial enlargement and had been considered as a Drosophila model of Parkinson’s disease (PD), caused fly muscle defects, and the loss of vimar could rescue these defects. Furthermore, we found that the mammalian homolog of Vimar, RAP1GDS1, played a similar role in regulating mitochondrial morphology, suggesting a functional conservation of this GEF member. The Miro/Vimar complex may be a promising drug target for diseases in which mitochondrial fission and fusion are dysfunctional. PMID:27716788

  11. Vimar Is a Novel Regulator of Mitochondrial Fission through Miro.

    Directory of Open Access Journals (Sweden)

    Lianggong Ding

    2016-10-01

    Full Text Available As fundamental processes in mitochondrial dynamics, mitochondrial fusion, fission and transport are regulated by several core components, including Miro. As an atypical Rho-like small GTPase with high molecular mass, the exchange of GDP/GTP in Miro may require assistance from a guanine nucleotide exchange factor (GEF. However, the GEF for Miro has not been identified. While studying mitochondrial morphology in Drosophila, we incidentally observed that the loss of vimar, a gene encoding an atypical GEF, enhanced mitochondrial fission under normal physiological conditions. Because Vimar could co-immunoprecipitate with Miro in vitro, we speculated that Vimar might be the GEF of Miro. In support of this hypothesis, a loss-of-function (LOF vimar mutant rescued mitochondrial enlargement induced by a gain-of-function (GOF Miro transgene; whereas a GOF vimar transgene enhanced Miro function. In addition, vimar lost its effect under the expression of a constitutively GTP-bound or GDP-bound Miro mutant background. These results indicate a genetic dependence of vimar on Miro. Moreover, we found that mitochondrial fission played a functional role in high-calcium induced necrosis, and a LOF vimar mutant rescued the mitochondrial fission defect and cell death. This result can also be explained by vimar's function through Miro, because Miro's effect on mitochondrial morphology is altered upon binding with calcium. In addition, a PINK1 mutant, which induced mitochondrial enlargement and had been considered as a Drosophila model of Parkinson's disease (PD, caused fly muscle defects, and the loss of vimar could rescue these defects. Furthermore, we found that the mammalian homolog of Vimar, RAP1GDS1, played a similar role in regulating mitochondrial morphology, suggesting a functional conservation of this GEF member. The Miro/Vimar complex may be a promising drug target for diseases in which mitochondrial fission and fusion are dysfunctional.

  12. Betaine is a positive regulator of mitochondrial respiration

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Icksoo, E-mail: icksoolee@dankook.ac.kr

    2015-01-09

    Highlights: • Betaine enhances cytochrome c oxidase activity and mitochondrial respiration. • Betaine increases mitochondrial membrane potential and cellular energy levels. • Betaine’s anti-tumorigenic effect might be due to a reversal of the Warburg effect. - Abstract: Betaine protects cells from environmental stress and serves as a methyl donor in several biochemical pathways. It reduces cardiovascular disease risk and protects liver cells from alcoholic liver damage and nonalcoholic steatohepatitis. Its pretreatment can rescue cells exposed to toxins such as rotenone, chloroform, and LiCl. Furthermore, it has been suggested that betaine can suppress cancer cell growth in vivo and in vitro. Mitochondrial electron transport chain (ETC) complexes generate the mitochondrial membrane potential, which is essential to produce cellular energy, ATP. Reduced mitochondrial respiration and energy status have been found in many human pathological conditions including aging, cancer, and neurodegenerative disease. In this study we investigated whether betaine directly targets mitochondria. We show that betaine treatment leads to an upregulation of mitochondrial respiration and cytochrome c oxidase activity in H2.35 cells, the proposed rate limiting enzyme of ETC in vivo. Following treatment, the mitochondrial membrane potential was increased and cellular energy levels were elevated. We propose that the anti-proliferative effects of betaine on cancer cells might be due to enhanced mitochondrial function contributing to a reversal of the Warburg effect.

  13. Mitochondrial biogenesis: pharmacological approaches.

    Science.gov (United States)

    Valero, Teresa

    2014-01-01

    Organelle biogenesis is concomitant to organelle inheritance during cell division. It is necessary that organelles double their size and divide to give rise to two identical daughter cells. Mitochondrial biogenesis occurs by growth and division of pre-existing organelles and is temporally coordinated with cell cycle events [1]. However, mitochondrial biogenesis is not only produced in association with cell division. It can be produced in response to an oxidative stimulus, to an increase in the energy requirements of the cells, to exercise training, to electrical stimulation, to hormones, during development, in certain mitochondrial diseases, etc. [2]. Mitochondrial biogenesis is therefore defined as the process via which cells increase their individual mitochondrial mass [3]. Recent discoveries have raised attention to mitochondrial biogenesis as a potential target to treat diseases which up to date do not have an efficient cure. Mitochondria, as the major ROS producer and the major antioxidant producer exert a crucial role within the cell mediating processes such as apoptosis, detoxification, Ca2+ buffering, etc. This pivotal role makes mitochondria a potential target to treat a great variety of diseases. Mitochondrial biogenesis can be pharmacologically manipulated. This issue tries to cover a number of approaches to treat several diseases through triggering mitochondrial biogenesis. It contains recent discoveries in this novel field, focusing on advanced mitochondrial therapies to chronic and degenerative diseases, mitochondrial diseases, lifespan extension, mitohormesis, intracellular signaling, new pharmacological targets and natural therapies. It contributes to the field by covering and gathering the scarcely reported pharmacological approaches in the novel and promising field of mitochondrial biogenesis. There are several diseases that have a mitochondrial origin such as chronic progressive external ophthalmoplegia (CPEO) and the Kearns- Sayre syndrome (KSS

  14. Quantitative ultrastructural analysis of basket and axo-axonic cell terminals in the mouse hippocampus.

    Science.gov (United States)

    Takács, Virág T; Szőnyi, András; Freund, Tamás F; Nyiri, Gábor; Gulyás, Attila I

    2015-03-01

    Three functionally different populations of perisomatic interneurons establish GABAergic synapses on hippocampal pyramidal cells: parvalbumin (PV)-containing basket cells, type 1 cannabinoid receptor (CB1)-positive basket cells both of which target somata, and PV-positive axo-axonic cells that innervate axon initial segments. Using electron microscopic reconstructions, we estimated that a pyramidal cell body receives synapses from about 60 and 140 synaptic terminals in the CA1 and CA3 area, respectively. About 60 % of these terminals were PV positive, whereas 35-40 % of them were CB1 positive. Only about 1 % (CA1) and 4 % (CA3) of the somatic boutons were negative for both markers. Using fluorescent labeling, we showed that most of the CB1-positive terminals expressed vesicular glutamate transporter 3. Reconstruction of somatic boutons revealed that although their volumes are similar, CB1-positive boutons are more flat and the total volume of their mitochondria was smaller than that of PV-positive boutons. Both types of boutons contain dense-core vesicles and frequently formed multiple release sites on their targets and innervated an additional soma or dendrite as well. PV-positive boutons possessed small, macular synapses; whereas the total synaptic area of CB1-positive boutons was larger and formed multiple irregular-shaped synapses. Axo-axonic boutons were smaller than somatic boutons, had only one synapse and their ultrastructural parameters were closer to those of PV-positive somatic boutons. Our results represent the first quantitative measurement-using a highly reliable method-of the contribution of different cell types to the perisomatic innervation of pyramidal neurons, and may help to explain functional differences in their output properties.

  15. Neurofilament proteins in axonal regeneration and neurodegenerative diseases

    Institute of Scientific and Technical Information of China (English)

    Haitao Wang; Minfei Wu; Chuanjun Zhan; Enyuan Ma; Maoguang Yang; Xiaoyu Yang; Yingpu Li

    2012-01-01

    Neurofilament protein is a component of the mature neuronal cytoskeleton, and it interacts with the zygosome, which is mediated by neurofilament-related proteins. Neurofilament protein regulates enzyme function and the structure of linker proteins. In addition, neurofilament gene expression plays an important role in nervous system development. Previous studies have shown that neurofilament gene transcriptional regulation is crucial for neurofilament protein expression, especially in axonal regeneration and degenerative diseases. Post-transcriptional regulation increased neurofilament protein gene transcription during axonal regeneration, ultimately resulting in a pattern of neurofilament protein expression. An expression imbalance of post-transcriptional regulatory proteins and other disorders could lead to amyotrophic lateral sclerosis or other neurodegenerative diseases. These findings indicated that after transcription, neurofilament protein regulated expression of related proteins and promoted regeneration of damaged axons, suggesting that regulation disorders could lead to neurodegenerative diseases.

  16. Pili canaliculi as manifestation of giant axonal neuropathy*

    Science.gov (United States)

    de Almeida Jr., Hiram Larangeira; Garcias, Gilberto; Silva, Ricardo Marques e; Batista, Stela Laner; Pasetto, Fernanda

    2016-01-01

    Giant axonal neuropathy is a rare autosomal recessive neurodegenerative disease. The condition is characterized by neurons with abnormally large axons due to intracellular filament accumulation. The swollen axons affect both the peripheral and central nervous system. A 6-year old female patient had been referred to a geneticist reporting problems with walking and hypotonia. At the age of 10, she became wheelchair dependent. Scanning electron microscopy of a curly hair classified it as pili canaliculi. GAN gene sequencing demonstrated mutation c.1456G>A (p.GLU486LYS). At the age of 12, the patient died due to respiratory complications. Dermatologists should be aware of this entity since hair changes are considered suggestive of GAN.

  17. Using quantum filters to process images of diffuse axonal injury

    Science.gov (United States)

    Pineda Osorio, Mateo

    2014-06-01

    Some images corresponding to a diffuse axonal injury (DAI) are processed using several quantum filters such as Hermite Weibull and Morse. Diffuse axonal injury is a particular, common and severe case of traumatic brain injury (TBI). DAI involves global damage on microscopic scale of brain tissue and causes serious neurologic abnormalities. New imaging techniques provide excellent images showing cellular damages related to DAI. Said images can be processed with quantum filters, which accomplish high resolutions of dendritic and axonal structures both in normal and pathological state. Using the Laplacian operators from the new quantum filters, excellent edge detectors for neurofiber resolution are obtained. Image quantum processing of DAI images is made using computer algebra, specifically Maple. Quantum filter plugins construction is proposed as a future research line, which can incorporated to the ImageJ software package, making its use simpler for medical personnel.

  18. Uncovering sensory axonal dysfunction in asymptomatic type 2 diabetic neuropathy

    Science.gov (United States)

    Sung, Jia-Ying; Tani, Jowy; Chang, Tsui-San; Lin, Cindy Shin-Yi

    2017-01-01

    This study investigated sensory and motor nerve excitability properties to elucidate the development of diabetic neuropathy. A total of 109 type 2 diabetes patients were recruited, and 106 were analyzed. According to neuropathy severity, patients were categorized into G0, G1, and G2+3 groups using the total neuropathy score-reduced (TNSr). Patients in the G0 group were asymptomatic and had a TNSr score of 0. Sensory and motor nerve excitability data from diabetic patients were compared with data from 33 healthy controls. Clinical assessment, nerve conduction studies, and sensory and motor nerve excitability testing data were analyzed to determine axonal dysfunction in diabetic neuropathy. In the G0 group, sensory excitability testing revealed increased stimulus for the 50% sensory nerve action potential (P<0.05), shortened strength-duration time constant (P<0.01), increased superexcitability (P<0.01), decreased subexcitability (P<0.05), decreased accommodation to depolarizing current (P<0.01), and a trend of decreased accommodation to hyperpolarizing current in threshold electrotonus. All the changes progressed into G1 (TNSr 1–8) and G2+3 (TNSr 9–24) groups. In contrast, motor excitability only had significantly increased stimulus for the 50% compound motor nerve action potential (P<0.01) in the G0 group. This study revealed that the development of axonal dysfunction in sensory axons occurred prior to and in a different fashion from motor axons. Additionally, sensory nerve excitability tests can detect axonal dysfunction even in asymptomatic patients. These insights further our understanding of diabetic neuropathy and enable the early detection of sensory axonal abnormalities, which may provide a basis for neuroprotective therapeutic approaches. PMID:28182728

  19. United Mitochondrial Disease Foundation

    Science.gov (United States)

    ... to Mitochondrial Disease FAQ's MitoFirst Handbook More Information Mito 101 Symposium Archives Get Connected Find an Event Adult Advisory Council Team Ask The Mito Doc Grand Rounds Kids & Teens Medical Child Abuse ...

  20. Motoneuron axon pathfinding errors in zebrafish: Differential effects related to concentration and timing of nicotine exposure

    Energy Technology Data Exchange (ETDEWEB)

    Menelaou, Evdokia; Paul, Latoya T. [Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803 (United States); Perera, Surangi N. [Joseph J. Zilber School of Public Health, University of Wisconsin — Milwaukee, Milwaukee, WI 53205 (United States); Svoboda, Kurt R., E-mail: svobodak@uwm.edu [Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803 (United States); Joseph J. Zilber School of Public Health, University of Wisconsin — Milwaukee, Milwaukee, WI 53205 (United States)

    2015-04-01

    Nicotine exposure during embryonic stages of development can affect many neurodevelopmental processes. In the developing zebrafish, exposure to nicotine was reported to cause axonal pathfinding errors in the later born secondary motoneurons (SMNs). These alterations in SMN axon morphology coincided with muscle degeneration at high nicotine concentrations (15–30 μM). Previous work showed that the paralytic mutant zebrafish known as sofa potato exhibited nicotine-induced effects onto SMN axons at these high concentrations but in the absence of any muscle deficits, indicating that pathfinding errors could occur independent of muscle effects. In this study, we used varying concentrations of nicotine at different developmental windows of exposure to specifically isolate its effects onto subpopulations of motoneuron axons. We found that nicotine exposure can affect SMN axon morphology in a dose-dependent manner. At low concentrations of nicotine, SMN axons exhibited pathfinding errors, in the absence of any nicotine-induced muscle abnormalities. Moreover, the nicotine exposure paradigms used affected the 3 subpopulations of SMN axons differently, but the dorsal projecting SMN axons were primarily affected. We then identified morphologically distinct pathfinding errors that best described the nicotine-induced effects on dorsal projecting SMN axons. To test whether SMN pathfinding was potentially influenced by alterations in the early born primary motoneuron (PMN), we performed dual labeling studies, where both PMN and SMN axons were simultaneously labeled with antibodies. We show that only a subset of the SMN axon pathfinding errors coincided with abnormal PMN axonal targeting in nicotine-exposed zebrafish. We conclude that nicotine exposure can exert differential effects depending on the levels of nicotine and developmental exposure window. - Highlights: • Embryonic nicotine exposure can specifically affect secondary motoneuron axons in a dose-dependent manner.

  1. The plant mitochondrial proteome

    DEFF Research Database (Denmark)

    Millar, A.H.; Heazlewood, J.L.; Kristensen, B.K.

    2005-01-01

    The plant mitochondrial proteome might contain as many as 2000-3000 different gene products, each of which might undergo post-translational modification. Recent studies using analytical methods, such as one-, two- and three-dimensional gel electrophoresis and one- and two-dimensional liquid...... context to be defined for them. There are indications that some of these proteins add novel activities to mitochondrial protein complexes in plants....

  2. [Mitochondrial diseases and stroke].

    Science.gov (United States)

    Irimia, P; Oliveros-Cid, A; Martínez-Vila, E

    1998-04-01

    We review the mitochondrial diseases in which cerebrovascular changes are seen, such as the MERRF syndrome (myoclonic epilepsy and ragged red fibers) or the Kearns-Sayre syndrome (progressive external ophthalmoplegia, retinitis pigmentaria, cerebellar disorders and disorders of cardiac conduction), focusing on the syndrome involving mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). We consider the different clinical aspects, diagnostic methods, pathophysiological mechanisms of the cerebrovascular involvement as well as therapeutic approaches.

  3. Mitochondrial protection by resveratrol.

    Science.gov (United States)

    Ungvari, Zoltan; Sonntag, William E; de Cabo, Rafael; Baur, Joseph A; Csiszar, Anna

    2011-07-01

    Mitochondrial dysfunction and oxidative stress are thought to play important roles in mammalian aging. Resveratrol is a plant-derived polyphenol that exerts diverse antiaging activities, mimicking some of the molecular and functional effects of dietary restriction. This review focuses on the molecular mechanisms underlying the mitochondrial protective effects of resveratrol, which could be exploited for the prevention or amelioration of age-related diseases in the elderly.

  4. Giant Axonal Neuropathy Among Two Siblings - A Case Report

    Directory of Open Access Journals (Sweden)

    John Jhon. K

    2001-01-01

    Full Text Available Giant axonal neuropathy is a rate disorder with an autosomal recessive inheritance. It should be differentiated from toxic neuropathies, and hereditary degenerative disorders of nervous system like Friedreich′s ataxia and HMSN. Thick curly hair, though may not be present always is a useful clinical clue to identify cases. Prognosis is generally poor though course of the illness is variable. We report here a clinically and hisopathologically characteristic familial case of giant axonal neuropathy, which occurred in a 17-year-old boy, and his 21-year-old sister.

  5. LHON: Mitochondrial Mutations and More.

    Science.gov (United States)

    Kirches, E

    2011-03-01

    Leber's hereditary optic neuropathy (LHON) is a mitochondrial disorder leading to severe visual impairment or even blindness by death of retinal ganglion cells (RGCs). The primary cause of the disease is usually a mutation of the mitochondrial genome (mtDNA) causing a single amino acid exchange in one of the mtDNA-encoded subunits of NADH:ubiquinone oxidoreductase, the first complex of the electron transport chain. It was thus obvious to accuse neuronal energy depletion as the most probable mediator of neuronal death. The group of Valerio Carelli and other authors have nicely shown that energy depletion shapes the cell fate in a LHON cybrid cell model. However, the cybrids used were osteosarcoma cells, which do not fully model neuronal energy metabolism. Although complex I mutations may cause oxidative stress, a potential pathogenetic role of the latter was less taken into focus. The hypothesis of bioenergetic failure does not provide a simple explanation for the relatively late disease onset and for the incomplete penetrance, which differs remarkably between genders. It is assumed that other genetic and environmental factors are needed in addition to the 'primary LHON mutations' to elicit RGC death. Relevant nuclear modifier genes have not been identified so far. The review discusses the unresolved problems of a pathogenetic hypothesis based on ATP decline and/or ROS-induced apoptosis in RGCs.

  6. Mitochondrial fusion and ERK activity regulate steroidogenic acute regulatory protein localization in mitochondria.

    Science.gov (United States)

    Duarte, Alejandra; Castillo, Ana Fernanda; Podestá, Ernesto J; Poderoso, Cecilia

    2014-01-01

    The rate-limiting step in the biosynthesis of steroid hormones, known as the transfer of cholesterol from the outer to the inner mitochondrial membrane, is facilitated by StAR, the Steroidogenic Acute Regulatory protein. We have described that mitochondrial ERK1/2 phosphorylates StAR and that mitochondrial fusion, through the up-regulation of a fusion protein Mitofusin 2, is essential during steroidogenesis. Here, we demonstrate that mitochondrial StAR together with mitochondrial active ERK and PKA are necessary for maximal steroid production. Phosphorylation of StAR by ERK is required for the maintenance of this protein in mitochondria, observed by means of over-expression of a StAR variant lacking the ERK phosphorylation residue. Mitochondrial fusion regulates StAR levels in mitochondria after hormone stimulation. In this study, Mitofusin 2 knockdown and mitochondrial fusion inhibition in MA-10 Leydig cells diminished StAR mRNA levels and concomitantly mitochondrial StAR protein. Together our results unveil the requirement of mitochondrial fusion in the regulation of the localization and mRNA abundance of StAR. We here establish the relevance of mitochondrial phosphorylation events in the correct localization of this key protein to exert its action in specialized cells. These discoveries highlight the importance of mitochondrial fusion and ERK phosphorylation in cholesterol transport by means of directing StAR to the outer mitochondrial membrane to achieve a large number of steroid molecules per unit of StAR.

  7. Characterizing the composition of molecular motors on moving axonal cargo using "cargo mapping" analysis.

    Science.gov (United States)

    Neumann, Sylvia; Campbell, George E; Szpankowski, Lukasz; Goldstein, Lawrence S B; Encalada, Sandra E

    2014-10-30

    Understanding the mechanisms by which molecular motors coordinate their activities to transport vesicular cargoes within neurons requires the quantitative analysis of motor/cargo associations at the single vesicle level. The goal of this protocol is to use quantitative fluorescence microscopy to correlate ("map") the position and directionality of movement of live cargo to the composition and relative amounts of motors associated with the same cargo. "Cargo mapping" consists of live imaging of fluorescently labeled cargoes moving in axons cultured on microfluidic devices, followed by chemical fixation during recording of live movement, and subsequent immunofluorescence (IF) staining of the exact same axonal regions with antibodies against motors. Colocalization between cargoes and their associated motors is assessed by assigning sub-pixel position coordinates to motor and cargo channels, by fitting Gaussian functions to the diffraction-limited point spread functions representing individual fluorescent point sources. Fixed cargo and motor images are subsequently superimposed to plots of cargo movement, to "map" them to their tracked trajectories. The strength of this protocol is the combination of live and IF data to record both the transport of vesicular cargoes in live cells and to determine the motors associated to these exact same vesicles. This technique overcomes previous challenges that use biochemical methods to determine the average motor composition of purified heterogeneous bulk vesicle populations, as these methods do not reveal compositions on single moving cargoes. Furthermore, this protocol can be adapted for the analysis of other transport and/or trafficking pathways in other cell types to correlate the movement of individual intracellular structures with their protein composition. Limitations of this protocol are the relatively low throughput due to low transfection efficiencies of cultured primary neurons and a limited field of view available for

  8. Peripheral neuropathy in mitochondrial disorders.

    Science.gov (United States)

    Pareyson, Davide; Piscosquito, Giuseppe; Moroni, Isabella; Salsano, Ettore; Zeviani, Massimo

    2013-10-01

    Why is peripheral neuropathy common but mild in many mitochondrial disorders, and why is it, in some cases, the predominant or only manifestation? Although this question remains largely unanswered, recent advances in cellular and molecular biology have begun to clarify the importance of mitochondrial functioning and distribution in the peripheral nerve. Mutations in proteins involved in mitochondrial dynamics (ie, fusion and fission) frequently result in a Charcot-Marie-Tooth phenotype. Peripheral neuropathies with different phenotypic presentations occur in mitochondrial diseases associated with abnormalities in mitochondrial DNA replication and maintenance, or associated with defects in mitochondrial respiratory chain complex V. Our knowledge of mitochondrial disorders is rapidly growing as new nuclear genes are identified and new phenotypes described. Early diagnosis of mitochondrial disorders, essential to provide appropriate genetic counselling, has become crucial in a few treatable conditions. Recognising and diagnosing an underlying mitochondrial defect in patients presenting with peripheral neuropathy is therefore of paramount importance.

  9. Ocular manifestations of mitochondrial disease

    Directory of Open Access Journals (Sweden)

    S. D. Mathebula

    2012-12-01

    Full Text Available Mitochondrial disease caused by mutations in mitochondrial DNA is recognized as one of the most common causes of inherited neurological disease. Neuro-ophthalmic manifestations are a common feature of mitochondrial disease.  Optic atrophy causing central visual loss is the dominant feature of mitochondrial DNA diseases. Nystagmus is also encountered in mitochondrial disease.Although optometrists are not involved with the management of mitochondrial disease, they are likely to see more patients with this disease. Oph-thalmic examination forms part of the clinical assessment of mitochondrial disease. Mitochondrial disease should be suspected in any patient with unexplained optic neuropathy, ophthalmoplegia, pigmentary retinopathy or retrochiasmal visual loss. Despite considerable advances in the under-standing of mitochondrial genetics and the patho-genesis of mtDNA diseases, no effective treatment options are currently available for patients withmitochondrial dysfunction. (S Afr Optom 201271(1 46-50

  10. Regulation of Axonal Midline Guidance by Prolyl 4-Hydroxylation in Caenorhabditis elegans

    DEFF Research Database (Denmark)

    Torpe, Nanna; Pocock, Roger David John

    2014-01-01

    Neuronal wiring during development requires that the growth cones of axons and dendrites are correctly guided to their appropriate targets. As in other animals, axon growth cones in Caenorhabditis elegans integrate information in their extracellular environment via interactions among transiently...

  11. Peripheral motor axons of SOD1(G127X) mutant mice are susceptible to activity-dependent degeneration

    DEFF Research Database (Denmark)

    Alvarez Herrero, Susana; Calin, A; Graffmo, K S

    2013-01-01

    Motor neuron disorders may be associated with mitochondrial dysfunction, and repetitive electrical impulse conduction during energy restriction has been found to cause neuronal degeneration. The aim of this study was to investigate the vulnerability of motor axons of a presymptomatic late......-onset, fast-progression SOD1(G127X) mouse model of amyotrophic lateral sclerosis to long-lasting, high-frequency repetitive activity. Tibial nerves were stimulated at ankle in 7 to 8-month-old SOD1(G127X) mice when they were clinically indistinguishable from wild-type (WT) mice. The evoked compound muscle...... action potentials and ascending compound nerve action potentials were recorded from plantar muscles and from the sciatic nerve, respectively. Repetitive stimulation (RS) was carried out in interrupted trains of 200-Hz for 3h. During the stimulation-sequence there was progressive conduction failure in WT...

  12. Axon diameter and intra-axonal volume fraction of the corticospinal tract in idiopathic normal pressure hydrocephalus measured by q-space imaging.

    Directory of Open Access Journals (Sweden)

    Kouhei Kamiya

    Full Text Available PURPOSE: Previous studies suggest that compression and stretching of the corticospinal tract (CST potentially cause treatable gait disturbance in patients with idiopathic normal pressure hydrocephalus (iNPH. Measurement of axon diameter with diffusion MRI has recently been used to investigate microstructural alterations in neurological diseases. In this study, we investigated alterations in the axon diameter and intra-axonal fraction of the CST in iNPH by q-space imaging (QSI analysis. METHODS: Nineteen patients with iNPH and 10 age-matched controls were recruited. QSI data were obtained with a 3-T system by using a single-shot echo planar imaging sequence with the diffusion gradient applied parallel to the antero-posterior axis. By using a two-component low-q fit model, the root mean square displacements of intra-axonal space ( =  axon diameter and intra-axonal volume fraction of the CST were calculated at the levels of the internal capsule and body of the lateral ventricle, respectively. RESULTS: Wilcoxon's rank-sum test revealed a significant increase in CST intra-axonal volume fraction at the paraventricular level in patients (p<0.001, whereas no significant difference was observed in the axon diameter. At the level of the internal capsule, neither axon diameter nor intra-axonal volume fraction differed significantly between the two groups. CONCLUSION: Our results suggest that in patients with iNPH, the CST does not undergo irreversible axonal damage but is rather compressed and/or stretched owing to pressure from the enlarged ventricle. These analyses of axon diameter and intra-axonal fraction yield insights into microstructural alterations of the CST in iNPH.

  13. Difference in trafficking of brain-derived neurotrophic factor between axons and dendrites of cortical neurons, revealed by live-cell imaging

    Directory of Open Access Journals (Sweden)

    Kohara Keigo

    2005-06-01

    Full Text Available Abstract Background Brain-derived neurotrophic factor (BDNF, which is sorted into a regulated secretory pathway of neurons, is supposed to act retrogradely through dendrites on presynaptic neurons or anterogradely through axons on postsynaptic neurons. Depending on which is the case, the pattern and direction of trafficking of BDNF in dendrites and axons are expected to be different. To address this issue, we analyzed movements of green fluorescent protein (GFP-tagged BDNF in axons and dendrites of living cortical neurons by time-lapse imaging. In part of the experiments, the expression of BDNF tagged with cyan fluorescent protein (CFP was compared with that of nerve growth factor (NGF tagged with yellow fluorescent protein (YFP, to see whether fluorescent protein-tagged BDNF is expressed in a manner specific to this neurotrophin. Results We found that BDNF tagged with GFP or CFP was expressed in a punctated manner in dendrites and axons in about two-thirds of neurons into which plasmid cDNAs had been injected, while NGF tagged with GFP or YFP was diffusely expressed even in dendrites in about 70% of the plasmid-injected neurons. In neurons in which BDNF-GFP was expressed as vesicular puncta in axons, 59 and 23% of the puncta were moving rapidly in the anterograde and retrograde directions, respectively. On the other hand, 64% of BDNF-GFP puncta in dendrites did not move at all or fluttered back and forth within a short distance. The rest of the puncta in dendrites were moving relatively smoothly in either direction, but their mean velocity of transport, 0.47 ± 0.23 (SD μm/s, was slower than that of the moving puncta in axons (0.73 ± 0.26 μm/s. Conclusion The present results show that the pattern and velocity of the trafficking of fluorescence protein-tagged BDNF are different between axons and dendrites, and suggest that the anterograde transport in axons may be the dominant stream of BDNF to release sites.

  14. Mitochondrial superoxide flashes: metabolic biomarkers of skeletal muscle activity and disease

    OpenAIRE

    2011-01-01

    Mitochondrial superoxide flashes (mSOFs) are stochastic events of quantal mitochondrial superoxide generation. Here, we used flexor digitorum brevis muscle fibers from transgenic mice with muscle-specific expression of a novel mitochondrial-targeted superoxide biosensor (mt-cpYFP) to characterize mSOF activity in skeletal muscle at rest, following intense activity, and under pathological conditions. Results demonstrate that mSOF activity in muscle depended on electron transport chain and aden...

  15. Mitochondrial diseases: therapeutic approaches.

    Science.gov (United States)

    DiMauro, Salvatore; Mancuso, Michelangelo

    2007-06-01

    Therapy of mitochondrial encephalomyopathies (defined restrictively as defects of the mitochondrial respiratory chain) is woefully inadequate, despite great progress in our understanding of the molecular bases of these disorders. In this review, we consider sequentially several different therapeutic approaches. Palliative therapy is dictated by good medical practice and includes anticonvulsant medication, control of endocrine dysfunction, and surgical procedures. Removal of noxious metabolites is centered on combating lactic acidosis, but extends to other metabolites. Attempts to bypass blocks in the respiratory chain by administration of electron acceptors have not been successful, but this may be amenable to genetic engineering. Administration of metabolites and cofactors is the mainstay of real-life therapy and is especially important in disorders due to primary deficiencies of specific compounds, such as carnitine or coenzyme Q10. There is increasing interest in the administration of reactive oxygen species scavengers both in primary mitochondrial diseases and in neurodegenerative diseases directly or indirectly related to mitochondrial dysfunction. Aerobic exercise and physical therapy prevent or correct deconditioning and improve exercise tolerance in patients with mitochondrial myopathies due to mitochondrial DNA (mtDNA) mutations. Gene therapy is a challenge because of polyplasmy and heteroplasmy, but interesting experimental approaches are being pursued and include, for example, decreasing the ratio of mutant to wild-type mitochondrial genomes (gene shifting), converting mutated mtDNA genes into normal nuclear DNA genes (allotopic expression), importing cognate genes from other species, or correcting mtDNA mutations with specific restriction endonucleases. Germline therapy raises ethical problems but is being considered for prevention of maternal transmission of mtDNA mutations. Preventive therapy through genetic counseling and prenatal diagnosis is

  16. IFNgamma enhances microglial reactions to hippocampal axonal degeneration

    DEFF Research Database (Denmark)

    Jensen, M B; Hegelund, I V; Lomholt, N D;

    2000-01-01

    periods. Message for the immune cytokine interferon-gamma (IFNgamma) was undetectable, and glial reactivity to axonal lesions occurred as normal in IFNgamma-deficient mice. Microglial responses to lesion-induced neuronal injury were markedly enhanced in myelin basic protein promoter-driven transgenic mice...

  17. PTEN inhibition and axon regeneration and neural repair

    Institute of Scientific and Technical Information of China (English)

    Yosuke Ohtake; Umar Hayat; Shuxin Li

    2015-01-01

    The intrinsic growth ability of all the neurons declines during development although some may grow better than others. Numerous intracellular signaling proteins and transcription factors have been shown to regulate the intrinsic growth capacity in mature neurons. Among them, PI3 kinase/Akt pathway is important for controlling axon elongation. As a negative regulator of this pathway, the tumor suppressor phosphatase and tensin homolog (PTEN) appears critical to con-trol the regenerative ability of young and adult neurons. This review will focus on recent research progress in axon regeneration and neural repair by PTEN inhibition and therapeutic potential of blocking this phosphatase for neurological disorders. Inhibition of PTEN by deletion in con-ditional knockout mice, knockdown by short-hairpin RNA, or blockade by pharmacological approaches, including administration of selective PTEN antagonist peptides, stimulates various degrees of axon regrowth in juvenile or adult rodents with central nervous system injuries. Im-portantly, post-injury PTEN suppression could enhance axonal growth and functional recovery in adult central nervous system after injury.

  18. Life-or-death decisions upon axonal damage.

    Science.gov (United States)

    Roselli, Francesco; Caroni, Pico

    2012-02-01

    In this issue of Neuron, Hu et al. (2012) report that upon axonal damage, CHOP and XBP1 unfolded protein response pathways are not recruited equally and have opposite effects on neuronal survival. XBP1 pathway boosting may represent a valuable neuroprotective strategy.