101
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Evans CS, Holzbaur EL. Degradation of engulfed mitochondria is rate-limiting in Optineurin-mediated mitophagy in neurons. eLife 2020; 9:50260. [PMID: 31934852 PMCID: PMC6959996 DOI: 10.7554/elife.50260] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 12/19/2019] [Indexed: 12/19/2022] Open
Abstract
Mitophagy, the selective removal of damaged mitochondria, is thought to be critical to maintain neuronal homeostasis. Mutations of proteins in the pathway cause neurodegenerative diseases, suggesting defective mitochondrial turnover contributes to neurodegeneration. In primary rat hippocampal neurons, we developed a mitophagy induction paradigm where mild oxidative stress induced low levels of mitochondrial damage. Mitophagy-associated proteins were sequentially recruited to depolarized mitochondria followed by sequestration into autophagosomes. The localization of these mitophagy events had a robust somal bias. In basal and induced conditions, engulfed mitochondria remained in non-acidified organelles for hours to days, illustrating efficient autophagosome sequestration but delayed lysosomal fusion or acidification. Furthermore, expression of an ALS-linked mutation in the pathway disrupted mitochondrial network integrity and this effect was exacerbated by oxidative stress. Thus, age-related decline in neuronal health or expression of disease-associated mutations in the pathway may exacerbate the slow kinetics of neuronal mitophagy, leading to neurodegeneration.
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Affiliation(s)
- Chantell S Evans
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Erika Lf Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
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102
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McCormick LE, Gupton SL. Mechanistic advances in axon pathfinding. Curr Opin Cell Biol 2020; 63:11-19. [PMID: 31927278 DOI: 10.1016/j.ceb.2019.12.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/02/2019] [Accepted: 12/02/2019] [Indexed: 02/08/2023]
Abstract
The development of a functional nervous system entails establishing connectivity between appropriate synaptic partners. During axonal pathfinding, the developing axon navigates through the extracellular environment, extending toward postsynaptic targets. In the early 1900s, Ramon y Cajal suggested that the growth cone, a specialized, dynamic, and cytoskeletal-rich structure at the tip of the extending axon, is guided by chemical cues in the extracellular environment. A century of work supports this hypothesis and introduced myriad guidance cues and receptors that promote a variety of growth cone behaviors including extension, pause, collapse, retraction, turning, and branching. Here, we highlight research from the last two years regarding pathways implicated in axon pathfinding.
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Affiliation(s)
- Laura E McCormick
- UNC Department of Cell Biology and Physiology, 111 Mason Farm Road, Chapel Hill, NC, 27599, USA
| | - Stephanie L Gupton
- UNC Department of Cell Biology and Physiology, 111 Mason Farm Road, Chapel Hill, NC, 27599, USA; UNC Neuroscience Center, 115 Mason Farm Road, Chapel Hill, NC, 27599, USA; UNC Lineberger Comprehensive Cancer Center, 101 Manning Dr, Chapel Hill, NC, 27514, USA.
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103
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The Synaptic Autophagy Cycle. J Mol Biol 2019; 432:2589-2604. [PMID: 31866297 DOI: 10.1016/j.jmb.2019.12.028] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/10/2019] [Accepted: 12/12/2019] [Indexed: 02/08/2023]
Abstract
Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved pathway in which proteins and organelles are delivered to the lysosome for degradation. In neurons, autophagy was originally described as associated with disease states and neuronal survival. Over the last decade, however, evidence has accumulated that autophagy controls synaptic function in both the axon and dendrite. Here, we review this literature, highlighting the role of autophagy in the pre- and postsynapse, synaptic plasticity, and behavior. We end by discussing open questions in the field of synaptic autophagy.
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104
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An autism-causing calcium channel variant functions with selective autophagy to alter axon targeting and behavior. PLoS Genet 2019; 15:e1008488. [PMID: 31805042 PMCID: PMC6894750 DOI: 10.1371/journal.pgen.1008488] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 10/21/2019] [Indexed: 11/22/2022] Open
Abstract
Common and rare variants of the CACNA1C voltage-gated calcium channel gene have been associated with autism and other neurodevelopmental disorders including schizophrenia, bipolar disorder and ADHD. However, little is known about how CACNA1C variants affect cellular processes to alter neurodevelopment. The Timothy syndrome mutation is a rare de novo gain-of-function variant in CACNA1C that causes autism with high penetrance, providing a powerful avenue into investigating the role of CACNA1C variants in neurodevelopmental disorders. Here, we use egl-19, the C. elegans homolog of CACNA1C, to investigate the role of voltage-gated calcium channels in autism. We show that an egl-19(gof) mutation that is equivalent to the Timothy syndrome mutation can alter axon targeting and affect behavior in C. elegans. We find that wildtype egl-19 negatively regulates axon termination. The egl-19(gof) mutation represses axon termination to cause axon targeting defects that lead to the misplacement of electrical synapses and alterations in habituation to light touch. Moreover, genetic interactions indicate that the egl-19(gof) mutation functions with genes that promote selective autophagy to cause defects in axon termination and behavior. These results reveal a novel genetic mechanism whereby a de novo mutation in CACNA1C can drive alterations in circuit formation and behavior. Autism is a disorder that affects neuronal development, leading to alterations in cognition and behavior. Imaging studies have revealed alterations in axonal connectivity as a key feature of autism. However, the underlying perturbations in cell biology that drive these alterations remain largely unknown. To address this issue, we have taken advantage of the Timothy syndrome mutation, a variant in a voltage-gated calcium channel that has the unusual property of causing autism with high penetrance. We identify a role for wild-type voltage-gated calcium channels in regulating axon targeting in C. elegans. Moreover, we find that two different versions of the Timothy syndrome mutation disrupt axon targeting. Our results suggest that the Timothy syndrome mutations disrupt axon targeting and behavior by interacting with genes that promote selective autophagy, the process through which cellular components are selected for degradation. These results reveal a mechanism through which variants in voltage-gated calcium channels can cause the disruptions in axonal connectivity that underlie autism.
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105
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Pushpalatha KV, Besse F. Local Translation in Axons: When Membraneless RNP Granules Meet Membrane-Bound Organelles. Front Mol Biosci 2019; 6:129. [PMID: 31824961 PMCID: PMC6882739 DOI: 10.3389/fmolb.2019.00129] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 11/06/2019] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic cell compartmentalization relies on long-known membrane-delimited organelles, as well as on more recently discovered membraneless macromolecular condensates. How these two types of organelles interact to regulate cellular functions is still largely unclear. In this review, we highlight how membraneless ribonucleoprotein (RNP) organelles, enriched in RNAs and associated regulatory proteins, cooperate with membrane-bound organelles for tight spatio-temporal control of gene expression in the axons of neuronal cells. Specifically, we present recent evidence that motile membrane-bound organelles are used as vehicles by RNP cargoes, promoting the long-range transport of mRNA molecules to distal axons. As demonstrated by recent work, membrane-bound organelles also promote local protein synthesis, by serving as platforms for the local translation of mRNAs recruited to their outer surface. Furthermore, dynamic and specific association between RNP cargoes and membrane-bound organelles is mediated by bi-partite adapter molecules that interact with both types of organelles selectively, in a regulated-manner. Maintaining such a dynamic interplay is critical, as alterations in this process are linked to neurodegenerative diseases. Together, emerging studies thus point to the coordination of membrane-bound and membraneless organelles as an organizing principle underlying local cellular responses.
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Affiliation(s)
| | - Florence Besse
- Université Côte d'Azur, CNRS, Inserm, Institut de Biology Valrose, Nice, France
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106
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Boecker CA, Olenick MA, Gallagher ER, Ward ME, Holzbaur ELF. ToolBox: Live Imaging of intracellular organelle transport in induced pluripotent stem cell-derived neurons. Traffic 2019; 21:138-155. [PMID: 31603614 DOI: 10.1111/tra.12701] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 12/13/2022]
Abstract
Induced pluripotent stem cells (iPSCs) hold promise to revolutionize studies of intracellular transport in live human neurons and to shed new light on the role of dysfunctional transport in neurodegenerative disorders. Here, we describe an approach for live imaging of axonal and dendritic transport in iPSC-derived cortical neurons. We use transfection and transient expression of genetically-encoded fluorescent markers to characterize the motility of Rab-positive vesicles, including early, late and recycling endosomes, as well as autophagosomes and mitochondria in iPSC-derived neurons. Comparing transport parameters of these organelles with data from primary rat hippocampal neurons, we uncover remarkable similarities. In addition, we generated lysosomal-associated membrane protein 1 (LAMP1)-enhanced green fluorescent protein (EGFP) knock-in iPSCs and show that knock-in neurons can be used to study the transport of endogenously labeled vesicles, as a parallel approach to the transient overexpression of fluorescently labeled organelle markers.
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Affiliation(s)
- Clemens Alexander Boecker
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Mara A Olenick
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Elizabeth R Gallagher
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Michael E Ward
- National Institutes of Health, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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107
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Yang R, Bostick Z, Garbouchian A, Luisi J, Banker G, Bentley M. A novel strategy to visualize vesicle-bound kinesins reveals the diversity of kinesin-mediated transport. Traffic 2019; 20:851-866. [PMID: 31461551 PMCID: PMC7714429 DOI: 10.1111/tra.12692] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Revised: 08/26/2019] [Accepted: 08/26/2019] [Indexed: 01/04/2023]
Abstract
In mammals, 15 to 20 kinesins are thought to mediate vesicle transport. Little is known about the identity of vesicles moved by each kinesin or the functional significance of such diversity. To characterize the transport mediated by different kinesins, we developed a novel strategy to visualize vesicle-bound kinesins in living cells. We applied this method to cultured neurons and systematically determined the localization and transport parameters of vesicles labeled by different members of the Kinesin-1, -2, and -3 families. We observed vesicle labeling with nearly all kinesins. Only six kinesins bound vesicles that undergo long-range transport in neurons. Of these, three had an axonal bias (KIF5B, KIF5C and KIF13B), two were unbiased (KIF1A and KIF1Bβ), and one transported only in dendrites (KIF13A). Overall, the trafficking of vesicle-bound kinesins to axons or dendrites did not correspond to their motor domain preference, suggesting that on-vesicle regulation is crucial for kinesin targeting. Surprisingly, several kinesins were associated with populations of somatodendritic vesicles that underwent little long-range transport. This assay should be broadly applicable for investigating kinesin function in many cell types.
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Affiliation(s)
- Rui Yang
- The Jungers Center for Neurosciences Research, Oregon Health & Science University, Portland, Oregon
- Department of Biochemistry, Duke University, Durham, North Carolina
| | - Zoe Bostick
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Sciences, Rensselaer Polytechnic Institute, Troy, New York
| | - Alex Garbouchian
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Sciences, Rensselaer Polytechnic Institute, Troy, New York
| | - Julie Luisi
- The Jungers Center for Neurosciences Research, Oregon Health & Science University, Portland, Oregon
| | - Gary Banker
- The Jungers Center for Neurosciences Research, Oregon Health & Science University, Portland, Oregon
| | - Marvin Bentley
- Department of Biological Sciences and the Center for Biotechnology and Interdisciplinary Sciences, Rensselaer Polytechnic Institute, Troy, New York
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108
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The Endolysosomal System and Proteostasis: From Development to Degeneration. J Neurosci 2019; 38:9364-9374. [PMID: 30381428 DOI: 10.1523/jneurosci.1665-18.2018] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 09/17/2018] [Accepted: 09/20/2018] [Indexed: 12/12/2022] Open
Abstract
How do neurons adapt their endolysosomal system to address the particular challenge of membrane transport across their elaborate cellular landscape and to maintain proteostasis for the lifetime of the organism? Here we review recent findings that address this central question. We discuss the cellular and molecular mechanisms of endolysosomal trafficking and the autophagy pathway in neurons, as well as their role in neuronal development and degeneration. These studies highlight the importance of understanding the basic cell biology of endolysosomal trafficking and autophagy and their roles in the maintenance of proteostasis within the context of neurons, which will be critical for developing effective therapies for various neurodevelopmental and neurodegenerative disorders.
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109
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Liao YC, Fernandopulle MS, Wang G, Choi H, Hao L, Drerup CM, Patel R, Qamar S, Nixon-Abell J, Shen Y, Meadows W, Vendruscolo M, Knowles TPJ, Nelson M, Czekalska MA, Musteikyte G, Gachechiladze MA, Stephens CA, Pasolli HA, Forrest LR, St George-Hyslop P, Lippincott-Schwartz J, Ward ME. RNA Granules Hitchhike on Lysosomes for Long-Distance Transport, Using Annexin A11 as a Molecular Tether. Cell 2019; 179:147-164.e20. [PMID: 31539493 PMCID: PMC6890474 DOI: 10.1016/j.cell.2019.08.050] [Citation(s) in RCA: 291] [Impact Index Per Article: 58.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 05/21/2019] [Accepted: 08/26/2019] [Indexed: 02/06/2023]
Abstract
Long-distance RNA transport enables local protein synthesis at metabolically-active sites distant from the nucleus. This process ensures an appropriate spatial organization of proteins, vital to polarized cells such as neurons. Here, we present a mechanism for RNA transport in which RNA granules "hitchhike" on moving lysosomes. In vitro biophysical modeling, live-cell microscopy, and unbiased proximity labeling proteomics reveal that annexin A11 (ANXA11), an RNA granule-associated phosphoinositide-binding protein, acts as a molecular tether between RNA granules and lysosomes. ANXA11 possesses an N-terminal low complexity domain, facilitating its phase separation into membraneless RNA granules, and a C-terminal membrane binding domain, enabling interactions with lysosomes. RNA granule transport requires ANXA11, and amyotrophic lateral sclerosis (ALS)-associated mutations in ANXA11 impair RNA granule transport by disrupting their interactions with lysosomes. Thus, ANXA11 mediates neuronal RNA transport by tethering RNA granules to actively-transported lysosomes, performing a critical cellular function that is disrupted in ALS.
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Affiliation(s)
| | | | - Guozhen Wang
- Cambridge Institute for Medical Research, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0XY, UK
| | - Heejun Choi
- HHMI Janelia Research Campus, Ashburn, VA, USA
| | | | | | | | - Seema Qamar
- Cambridge Institute for Medical Research, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0XY, UK
| | - Jonathon Nixon-Abell
- Cambridge Institute for Medical Research, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0XY, UK
| | - Yi Shen
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
| | - William Meadows
- Cambridge Institute for Medical Research, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0XY, UK
| | | | - Tuomas P J Knowles
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK; Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK
| | | | | | - Greta Musteikyte
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
| | | | | | | | | | - Peter St George-Hyslop
- Cambridge Institute for Medical Research, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0XY, UK; Department of Medicine (Division of Neurology), University of Toronto and University Health Network, Toronto, Ontario M5S 3H2, Canada
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110
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Delevoye C, Marks MS, Raposo G. Lysosome-related organelles as functional adaptations of the endolysosomal system. Curr Opin Cell Biol 2019; 59:147-158. [PMID: 31234051 PMCID: PMC6726539 DOI: 10.1016/j.ceb.2019.05.003] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 05/10/2019] [Accepted: 05/13/2019] [Indexed: 12/19/2022]
Abstract
Unique functions of specialised cells such as those of the immune and haemostasis systems, skin, blood vessels, lung, and bone require specialised compartments, collectively referred to as lysosome-related organelles (LROs), that share features of endosomes and lysosomes. LROs harbour unique morphological features and cell type-specific contents, and most if not all undergo regulated secretion for diverse functions. Ongoing research, largely driven by analyses of inherited diseases and their model systems, is unravelling the mechanisms involved in LRO generation, maturation, transport and secretion. A molecular understanding of these features will provide targets and markers that can be exploited for diagnosis and therapy of a myriad of diseases.
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Affiliation(s)
- Cédric Delevoye
- Structure and Membrane Compartments, Institut Curie, Paris Sciences and Lettres Research University, Centre National de la Recherche Scientifique, UMR144, Paris, France
| | - Michael S Marks
- Dept. of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA 19104, USA; Dept. of Pathology and Laboratory Medicine and Dept. of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Graça Raposo
- Structure and Membrane Compartments, Institut Curie, Paris Sciences and Lettres Research University, Centre National de la Recherche Scientifique, UMR144, Paris, France.
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111
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van Bommel B, Konietzny A, Kobler O, Bär J, Mikhaylova M. F-actin patches associated with glutamatergic synapses control positioning of dendritic lysosomes. EMBO J 2019; 38:e101183. [PMID: 31267565 PMCID: PMC6669925 DOI: 10.15252/embj.2018101183] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 05/27/2019] [Accepted: 05/29/2019] [Indexed: 12/31/2022] Open
Abstract
Organelle positioning within neurites is required for proper neuronal function. In dendrites, with their complex cytoskeletal organization, transport of organelles is guided by local specializations of the microtubule and actin cytoskeleton, and by coordinated activity of different motor proteins. Here, we focus on the actin cytoskeleton in the dendritic shaft and describe dense structures consisting of longitudinal and branched actin filaments. These actin patches are devoid of microtubules and are frequently located at the base of spines, or form an actin mesh around excitatory shaft synapses. Using lysosomes as an example, we demonstrate that the presence of actin patches has a strong impact on dendritic organelle transport, as lysosomes frequently stall at these locations. We provide mechanistic insights on this pausing behavior, demonstrating that actin patches form a physical barrier for kinesin-driven cargo. In addition, we identify myosin Va as an active tether which mediates long-term stalling. This correlation between the presence of actin meshes and halting of organelles could be a generalized principle by which synapses control organelle trafficking.
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Affiliation(s)
- Bas van Bommel
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anja Konietzny
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Oliver Kobler
- Combinatorial Neuroimaging Core Facility (CNI), Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Julia Bär
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Marina Mikhaylova
- DFG Emmy Noether Group "Neuronal Protein Transport", Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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112
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Griffin EF, Yan X, Caldwell KA, Caldwell GA. Distinct functional roles of Vps41-mediated neuroprotection in Alzheimer's and Parkinson's disease models of neurodegeneration. Hum Mol Genet 2019; 27:4176-4193. [PMID: 30508205 DOI: 10.1093/hmg/ddy308] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Accepted: 08/21/2018] [Indexed: 12/25/2022] Open
Abstract
Commonalities and, in some cases, pathological overlap between neurodegenerative diseases have led to speculation that targeting of underlying mechanisms might be of potentially shared therapeutic benefit. Alzheimer's disease is characterized by the formation of plaques, composed primarily of the amyloid-β 1-42 (Aβ) peptide in the brain, resulting in neurodegeneration. Previously, we have shown that overexpression of the lysosomal-trafficking protein, human Vps41 (hVps41), is neuroprotective in a transgenic worm model of Parkinson's disease, wherein progressive dopaminergic neurodegeneration is induced by α-synuclein overexpression. Here, we report the results of a systematic comparison of hVps41-mediated neuroprotection between α-synuclein and Aβ in transgenic nematode models of Caenorhabditis elegans. Our results indicate that an ARF-like GTPase gene product, ARL-8, mitigates endocytic Aβ neurodegeneration in a VPS-41-dependent manner, rather than through RAB-7 and AP3 as with α-synuclein. Furthermore, the neuroprotective effect of ARL-8 or hVps41 appears to be dependent on their colocalization and the activity of ARL-8. Additionally, we demonstrate that the LC3 orthologue, LGG-2, plays a critical role in Aβ toxicity with ARL-8. Further analysis of functional effectors of Aβ protein processing via the lysosomal pathway will assist in the elucidation of the underlying mechanism involving VPS-41-mediated neuroprotection. These results reveal functional distinctions in the intracellular management of neurotoxic proteins that serve to better inform the path for development of therapeutic interventions to halt neurodegeneration.
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Affiliation(s)
- Edward F Griffin
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA
| | | | - Kim A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA.,Departments of Neurology and Neurobiology, Center for Neurodegeneration and Experimental Therapeutics, Nathan Shock Center for Research on the Basic Biology of Aging, University of Alabama at Birmingham School of Medicine, Birmingham, AL, USA
| | - Guy A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA.,Departments of Neurology and Neurobiology, Center for Neurodegeneration and Experimental Therapeutics, Nathan Shock Center for Research on the Basic Biology of Aging, University of Alabama at Birmingham School of Medicine, Birmingham, AL, USA
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113
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Ibata K, Kono M, Narumi S, Motohashi J, Kakegawa W, Kohda K, Yuzaki M. Activity-Dependent Secretion of Synaptic Organizer Cbln1 from Lysosomes in Granule Cell Axons. Neuron 2019; 102:1184-1198.e10. [PMID: 31072786 DOI: 10.1016/j.neuron.2019.03.044] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Revised: 03/18/2019] [Accepted: 03/27/2019] [Indexed: 12/18/2022]
Abstract
Synapse formation is achieved by various synaptic organizers. Although this process is highly regulated by neuronal activity, the underlying molecular mechanisms remain largely unclear. Here we show that Cbln1, a synaptic organizer of the C1q family, is released from lysosomes in axons but not dendrites of cerebellar granule cells in an activity- and Ca2+-dependent manner. Exocytosed Cbln1 was retained on axonal surfaces by binding to its presynaptic receptor neurexin. Cbln1 further diffused laterally along the axonal surface and accumulated at boutons by binding postsynaptic δ2 glutamate receptors. Cbln1 exocytosis was insensitive to tetanus neurotoxin, accompanied by cathepsin B release, and decreased by disrupting lysosomes. Furthermore, overexpression of lysosomal sialidase Neu1 not only inhibited Cbln1 and cathepsin B exocytosis in vitro but also reduced axonal bouton formation in vivo. Our findings imply that co-release of Cbln1 and cathepsin B from lysosomes serves as a new mechanism of activity-dependent coordinated synapse modification.
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Affiliation(s)
- Keiji Ibata
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; Department of Physiology, St. Marianna University School of Medicine, Kanagawa 216-8511, Japan
| | - Maya Kono
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan; Department of Neurosurgery, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Sakae Narumi
- Department of Physiology, St. Marianna University School of Medicine, Kanagawa 216-8511, Japan
| | - Junko Motohashi
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Wataru Kakegawa
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Kazuhisa Kohda
- Department of Physiology, St. Marianna University School of Medicine, Kanagawa 216-8511, Japan
| | - Michisuke Yuzaki
- Department of Physiology, Keio University School of Medicine, Tokyo 160-8582, Japan.
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114
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Zheng Y, Zhang X, Wu X, Jiang L, Ahsan A, Ma S, Xiao Z, Han F, Qin ZH, Hu W, Chen Z. Somatic autophagy of axonal mitochondria in ischemic neurons. J Cell Biol 2019; 218:1891-1907. [PMID: 30979799 PMCID: PMC6548140 DOI: 10.1083/jcb.201804101] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 01/01/2019] [Accepted: 03/15/2019] [Indexed: 12/12/2022] Open
Abstract
How mitochondria damaged in distal axons are cleared is not understood. Zheng et al. find that axonal mitochondria return to neuronal soma for mitophagy after ischemic insult. These spatial features of neuronal mitophagy provide insight into how neurons control mitochondrial quality under pathological conditions. Mitophagy protects against ischemic neuronal injury by eliminating damaged mitochondria, but it is unclear how mitochondria in distal axons are cleared. We find that oxygen and glucose deprivation-reperfusion reduces mitochondrial content in both cell bodies and axons. Axonal mitochondria elimination was not abolished in Atg7fl/fl;nes-Cre neurons, suggesting the absence of direct mitophagy in axons. Instead, axonal mitochondria were enwrapped by autophagosomes in soma and axon-derived mitochondria prioritized for elimination by autophagy. Intriguingly, axonal mitochondria showed prompt loss of anterograde motility but increased retrograde movement upon reperfusion. Anchoring of axonal mitochondria by syntaphilin blocked neuronal mitophagy and aggravated injury. Conversely, induced binding of mitochondria to dynein reinforced retrograde transport and enhanced mitophagy to prevent mitochondrial dysfunction and attenuate neuronal injury. Therefore, we reveal somatic autophagy of axonal mitochondria in ischemic neurons and establish a direct link of retrograde mitochondrial movement with mitophagy. Our findings may provide a new concept for reducing ischemic neuronal injury by correcting mitochondrial motility.
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Affiliation(s)
- Yanrong Zheng
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Xiangnan Zhang
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Xiaoli Wu
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Lei Jiang
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Anil Ahsan
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Shijia Ma
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Ziyu Xiao
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Feng Han
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Zheng-Hong Qin
- Department of Pharmacology and Laboratory of Aging and Nervous Diseases, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, Soochow University School of Pharmaceutical Sciences, Suzhou, China
| | - Weiwei Hu
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
| | - Zhong Chen
- Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang University, Hangzhou, China
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115
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Zheng YR, Zhang XN, Chen Z. Mitochondrial transport serves as a mitochondrial quality control strategy in axons: Implications for central nervous system disorders. CNS Neurosci Ther 2019; 25:876-886. [PMID: 30900394 PMCID: PMC6566064 DOI: 10.1111/cns.13122] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Revised: 03/02/2019] [Accepted: 03/05/2019] [Indexed: 12/13/2022] Open
Abstract
Axonal mitochondrial quality is essential for neuronal health and functions. Compromised mitochondrial quality, reflected by loss of membrane potential, collapse of ATP production, abnormal morphology, burst of reactive oxygen species generation, and impaired Ca2+ buffering capacity, can alter mitochondrial transport. Mitochondrial transport in turn maintains axonal mitochondrial homeostasis in several ways. Newly generated mitochondria are anterogradely transported along with axon from soma to replenish axonal mitochondrial pool, while damaged mitochondria undergo retrograde transport for repair or degradation. Besides, mitochondria are also arrested in axon to quarantine damages locally. Accumulating evidence suggests abnormal mitochondrial transport leads to mitochondrial dysfunction and axon degeneration in a variety of neurological and psychiatric disorders. Further investigations into the details of this process would help to extend our understanding of various neurological diseases and shed light on the corresponding therapies.
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Affiliation(s)
- Yan-Rong Zheng
- Institute of Pharmacology and Toxicology, NHC and CAMS Key Laboratory of Medical Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Xiang-Nan Zhang
- Institute of Pharmacology and Toxicology, NHC and CAMS Key Laboratory of Medical Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Zhong Chen
- Institute of Pharmacology and Toxicology, NHC and CAMS Key Laboratory of Medical Neurobiology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.,Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
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116
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Bae D, Moore KA, Mella JM, Hayashi SY, Hollien J. Degradation of Blos1 mRNA by IRE1 repositions lysosomes and protects cells from stress. J Cell Biol 2019; 218:1118-1127. [PMID: 30787040 PMCID: PMC6446841 DOI: 10.1083/jcb.201809027] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/28/2018] [Accepted: 01/23/2019] [Indexed: 11/22/2022] Open
Abstract
Bae et al. show that degradation of the mRNA encoding the adaptor Blos1 leads to the repositioning of late endosomes/lysosomes to the microtubule-organizing center in response to ER stress. This repositioning enhances cell survival during stress by promoting the clearance of protein aggregates. Cells respond to stress in the ER by initiating the widely conserved unfolded protein response. Activation of the ER transmembrane nuclease IRE1 leads to the degradation of specific mRNAs, but how this pathway affects the ability of cells to recover from stress is not known. Here, we show that degradation of the mRNA encoding biogenesis of lysosome-related organelles 1 subunit 1 (Blos1) leads to the repositioning of late endosomes (LEs)/lysosomes to the microtubule-organizing center in response to stress in mouse cells. Overriding Blos1 degradation led to ER stress sensitivity and the accumulation of ubiquitinated protein aggregates, whose efficient degradation required their independent trafficking to the cell center and the LE-associated endosomal sorting complexes required for transport. We propose that Blos1 regulation by IRE1 promotes LE-mediated microautophagy of protein aggregates and protects cells from their cytotoxic effects.
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Affiliation(s)
- Donghwi Bae
- School of Biological Sciences, University of Utah, Salt Lake City, UT
| | - Kristin A Moore
- School of Biological Sciences, University of Utah, Salt Lake City, UT
| | - Jessica M Mella
- School of Biological Sciences, University of Utah, Salt Lake City, UT
| | | | - Julie Hollien
- School of Biological Sciences, University of Utah, Salt Lake City, UT
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117
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Farías GG, Fréal A, Tortosa E, Stucchi R, Pan X, Portegies S, Will L, Altelaar M, Hoogenraad CC. Feedback-Driven Mechanisms between Microtubules and the Endoplasmic Reticulum Instruct Neuronal Polarity. Neuron 2019; 102:184-201.e8. [PMID: 30772082 DOI: 10.1016/j.neuron.2019.01.030] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Revised: 11/29/2018] [Accepted: 01/15/2019] [Indexed: 12/20/2022]
Abstract
Establishment of neuronal polarity depends on local microtubule (MT) reorganization. The endoplasmic reticulum (ER) consists of cisternae and tubules and, like MTs, forms an extensive network throughout the entire cell. How the two networks interact and control neuronal development is an outstanding question. Here we show that the interplay between MTs and the ER is essential for neuronal polarity. ER tubules localize within the axon, whereas ER cisternae are retained in the somatodendritic domain. MTs are essential for axonal ER tubule stabilization, and, reciprocally, the ER is required for stabilizing and organizing axonal MTs. Recruitment of ER tubules into one minor neurite initiates axon formation, whereas ER retention in the perinuclear area or disruption of ER tubules prevent neuronal polarization. The ER-shaping protein P180, present in axonal ER tubules, controls axon specification by regulating local MT remodeling. We propose a model in which feedback-driven regulation between the ER and MTs instructs neuronal polarity.
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Affiliation(s)
- Ginny G Farías
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands.
| | - Amélie Fréal
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands
| | - Elena Tortosa
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands
| | - Riccardo Stucchi
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands; Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Xingxiu Pan
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands
| | - Sybren Portegies
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands
| | - Lena Will
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands
| | - Maarten Altelaar
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht 3584 CH, the Netherlands.
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118
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von Kleist L, Ariunbat K, Braren I, Stauber T, Storch S, Danyukova T. A newly generated neuronal cell model of CLN7 disease reveals aberrant lysosome motility and impaired cell survival. Mol Genet Metab 2019; 126:196-205. [PMID: 30301600 DOI: 10.1016/j.ymgme.2018.09.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 09/26/2018] [Accepted: 09/26/2018] [Indexed: 01/11/2023]
Abstract
Mutations in the CLN7/MFSD8 gene encoding the lysosomal membrane protein CLN7 are causative of CLN7 disease, an inherited neurodegenerative disorder that typically affects children. To gain insight into the pathomechanisms of CLN7 disease, we established an immortalized cell line based on cerebellar (Cb) granule neuron precursors isolated from Cln7-/- mice. Here, we demonstrate that Cln7-deficient neuron-derived Cb cells display an abnormal phenotype that includes increased size and defective outward movement of late endosomes and lysosomes as well as impaired lysosomal exocytosis. Whereas Cln7-/- Cb cells appeared to be autophagy-competent, loss of Cln7 resulted in enhanced cell death under prolonged nutrient deprivation. Furthermore, reduced cell survival of Cln7-deficient cells was accompanied by a significantly impaired protein kinase B/Akt phosphorylation at Ser473 during long-term starvation. In summary, our data demonstrate for the first time that the putative lysosomal transporter CLN7 is relevant for lysosome motility and plays an important role for neuronal cell survival under conditions of starvation.
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Affiliation(s)
- Lisa von Kleist
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany.
| | - Khandsuren Ariunbat
- Section Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
| | - Ingke Braren
- Vector Core Unit, Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
| | - Tobias Stauber
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany.
| | - Stephan Storch
- Section Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
| | - Tatyana Danyukova
- Section Biochemistry, Children's Hospital, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
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119
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Guedes-Dias P, Nirschl JJ, Abreu N, Tokito MK, Janke C, Magiera MM, Holzbaur ELF. Kinesin-3 Responds to Local Microtubule Dynamics to Target Synaptic Cargo Delivery to the Presynapse. Curr Biol 2019; 29:268-282.e8. [PMID: 30612907 DOI: 10.1016/j.cub.2018.11.065] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 11/08/2018] [Accepted: 11/28/2018] [Indexed: 01/05/2023]
Abstract
Neurons in the CNS establish thousands of en passant synapses along their axons. Robust neurotransmission depends on the replenishment of synaptic components in a spatially precise manner. Using live-cell microscopy and single-molecule reconstitution assays, we find that the delivery of synaptic vesicle precursors (SVPs) to en passant synapses in hippocampal neurons is specified by an interplay between the kinesin-3 KIF1A motor and presynaptic microtubules. Presynaptic sites are hotspots of dynamic microtubules rich in GTP-tubulin. KIF1A binds more weakly to GTP-tubulin than GDP-tubulin and competes with end-binding (EB) proteins for binding to the microtubule plus end. A disease-causing mutation within KIF1A that reduces preferential binding to GDP- versus GTP-rich microtubules disrupts SVP delivery and reduces presynaptic release upon neuronal stimulation. Thus, the localized enrichment of dynamic microtubules along the axon specifies a localized unloading zone that ensures the accurate delivery of SVPs, controlling presynaptic strength in hippocampal neurons.
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Affiliation(s)
- Pedro Guedes-Dias
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA; The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
| | - Jeffrey J Nirschl
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA; The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
| | - Nohely Abreu
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA; The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
| | - Mariko K Tokito
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
| | - Carsten Janke
- Institut Curie, PSL Research University, CNRS UMR3348, Orsay, France; Université Paris Sud, Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Maria M Magiera
- Institut Curie, PSL Research University, CNRS UMR3348, Orsay, France; Université Paris Sud, Université Paris-Saclay, CNRS UMR3348, Orsay, France
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA; The Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6085, USA.
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120
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Griffin EF, Caldwell KA, Caldwell GA. Vacuolar protein sorting protein 41 (VPS41) at an intersection of endosomal traffic in neurodegenerative disease. Neural Regen Res 2019; 14:1210-1212. [PMID: 30804248 PMCID: PMC6425830 DOI: 10.4103/1673-5374.251329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Edward F Griffin
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA
| | - Kim A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa; Departments of Neurology and Neurobiology; Center for Neurodegeneration and Experimental Therapeutics, University of Alabama at Birmingham School of Medicine; Nathan Shock Center of Excellence for Basic Research in the Biology of Aging, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Guy A Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa; Departments of Neurology and Neurobiology; Center for Neurodegeneration and Experimental Therapeutics, University of Alabama at Birmingham School of Medicine; Nathan Shock Center of Excellence for Basic Research in the Biology of Aging, University of Alabama at Birmingham, Birmingham, AL, USA
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121
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Mohan N, Sorokina EM, Verdeny IV, Alvarez AS, Lakadamyali M. Detyrosinated microtubules spatially constrain lysosomes facilitating lysosome-autophagosome fusion. J Cell Biol 2018; 218:632-643. [PMID: 30567713 PMCID: PMC6363446 DOI: 10.1083/jcb.201807124] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 10/22/2018] [Accepted: 11/27/2018] [Indexed: 12/31/2022] Open
Abstract
Detyrosinated microtubules constitute a minor subpopulation of microtubules in epithelial cells. Lysosomes are specifically enriched on detyrosinated microtubules through a kinesin-1–dependent mechanism. This spatial constraining of lysosomes to a subset of microtubules enables them to efficiently encounter and fuse with autophagosomes to initiate autophagy. Microtubule post-translational modifications impart functional diversity to microtubules by affecting their dynamics, organization, and interaction with proteins. Using super-resolution microscopy, we show that only a small subpopulation of microtubules are detyrosinated in epithelial cells, while acetylated and tyrosinated microtubules comprise the majority of all microtubules. Surprisingly, lysosomes are enriched by approximately threefold on detyrosinated microtubules. Further, their motility on detyrosinated microtubules is impaired, showing shorter runs and more frequent and longer pauses. Lysosome enrichment is mediated through a kinesin-1–dependent mechanism, since knocking down this motor abolishes enrichment. Finally, correlative live-cell and super-resolution microscopy showed that lysosomes interact with autophagosomes on detyrosinated microtubules. Removal of detyrosinated microtubules or knockdown of kinesin-1 leads to a decrease in the percentage of autolysosomes, a fusion intermediate of autophagosomes and lysosomes. Taken together, our data reveal a new role of detyrosinated microtubules as hubs that spatially concentrate lysosomes on a small subset of microtubules and facilitate their interaction and fusion with autophagosomes to initiate autophagy.
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Affiliation(s)
- Nitin Mohan
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Elena M Sorokina
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Ione Vilanova Verdeny
- Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Angel Sandoval Alvarez
- Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Melike Lakadamyali
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA .,Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
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122
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Petrova V, Eva R. The Virtuous Cycle of Axon Growth: Axonal Transport of Growth-Promoting Machinery as an Intrinsic Determinant of Axon Regeneration. Dev Neurobiol 2018; 78:898-925. [PMID: 29989351 DOI: 10.1002/dneu.22608] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 05/25/2018] [Accepted: 05/26/2018] [Indexed: 02/02/2023]
Abstract
Injury to the brain and spinal cord has devastating consequences because adult central nervous system (CNS) axons fail to regenerate. Injury to the peripheral nervous system (PNS) has a better prognosis, because adult PNS neurons support robust axon regeneration over long distances. CNS axons have some regenerative capacity during development, but this is lost with maturity. Two reasons for the failure of CNS regeneration are extrinsic inhibitory molecules, and a weak intrinsic capacity for growth. Extrinsic inhibitory molecules have been well characterized, but less is known about the neuron-intrinsic mechanisms which prevent axon re-growth. Key signaling pathways and genetic/epigenetic factors have been identified which can enhance regenerative capacity, but the precise cellular mechanisms mediating their actions have not been characterized. Recent studies suggest that an important prerequisite for regeneration is an efficient supply of growth-promoting machinery to the axon; however, this appears to be lacking from non-regenerative axons in the adult CNS. In the first part of this review, we summarize the evidence linking axon transport to axon regeneration. We discuss the developmental decline in axon regeneration capacity in the CNS, and comment on how this is paralleled by a similar decline in the selective axonal transport of regeneration-associated receptors such as integrins and growth factor receptors. In the second part, we discuss the mechanisms regulating selective polarized transport within neurons, how these relate to the intrinsic control of axon regeneration, and whether they can be targeted to enhance regenerative capacity. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 00: 000-000, 2018.
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Affiliation(s)
- Veselina Petrova
- John Van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 OPY, United Kingdom
| | - Richard Eva
- John Van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 OPY, United Kingdom
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123
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Joshi U, Houwman JA, van der Sluijs P. Lysosomes nor Mice Move Forward without Borcs7. Trends Cell Biol 2018; 28:761-763. [PMID: 30185380 DOI: 10.1016/j.tcb.2018.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 08/15/2018] [Indexed: 10/28/2022]
Abstract
Lysosome function and position in the cytoplasm depends on the BORCS machinery, which tethers lysosomes to the kinesin microtubule motor. A recent paper of Snouwaert et al. in Cell Reports characterizes a mouse with a spontaneous mutation in the Borcs7 subunit, which causes axonal dystrophy and impaired motor function.
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Affiliation(s)
- Urjita Joshi
- Cellular Protein Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Joseline A Houwman
- Cellular Protein Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Peter van der Sluijs
- Cellular Protein Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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124
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Yap CC, Digilio L, McMahon LP, Garcia ADR, Winckler B. Degradation of dendritic cargos requires Rab7-dependent transport to somatic lysosomes. J Cell Biol 2018; 217:3141-3159. [PMID: 29907658 PMCID: PMC6122995 DOI: 10.1083/jcb.201711039] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 03/30/2018] [Accepted: 05/31/2018] [Indexed: 12/13/2022] Open
Abstract
Neurons are large and long lived, creating high needs for regulating protein turnover. Disturbances in proteostasis lead to aggregates and cellular stress. We characterized the behavior of the short-lived dendritic membrane proteins Nsg1 and Nsg2 to determine whether these proteins are degraded locally in dendrites or centrally in the soma. We discovered a spatial heterogeneity of endolysosomal compartments in dendrites. Early EEA1-positive and late Rab7-positive endosomes are found throughout dendrites, whereas the density of degradative LAMP1- and cathepsin (Cat) B/D-positive lysosomes decreases steeply past the proximal segment. Unlike in fibroblasts, we found that the majority of dendritic Rab7 late endosomes (LEs) do not contain LAMP1 and that a large proportion of LAMP1 compartments do not contain CatB/D. Second, Rab7 activity is required to mobilize distal predegradative LEs for transport to the soma and terminal degradation. We conclude that the majority of dendritic LAMP1 endosomes are not degradative lysosomes and that terminal degradation of dendritic cargos such as Nsg1, Nsg2, and DNER requires Rab7-dependent transport in LEs to somatic lysosomes.
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Affiliation(s)
- Chan Choo Yap
- Department of Cell Biology, University of Virginia, Charlottesville, VA
| | - Laura Digilio
- Department of Cell Biology, University of Virginia, Charlottesville, VA
| | - Lloyd P McMahon
- Department of Cell Biology, University of Virginia, Charlottesville, VA
| | | | - Bettina Winckler
- Department of Cell Biology, University of Virginia, Charlottesville, VA
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125
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Cheng XT, Xie YX, Zhou B, Huang N, Farfel-Becker T, Sheng ZH. Characterization of LAMP1-labeled nondegradative lysosomal and endocytic compartments in neurons. J Cell Biol 2018; 217:3127-3139. [PMID: 29695488 PMCID: PMC6123004 DOI: 10.1083/jcb.201711083] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 02/20/2018] [Accepted: 04/13/2018] [Indexed: 01/04/2023] Open
Abstract
Despite widespread distribution of LAMP1 and the heterogeneous nature of LAMP1-labeled compartments, LAMP1 is routinely used as a lysosomal marker, and LAMP1-positive organelles are often referred to as lysosomes. In this study, we use immunoelectron microscopy and confocal imaging to provide quantitative analysis of LAMP1 distribution in various autophagic and endolysosomal organelles in neurons. Our study demonstrates that a significant portion of LAMP1-labeled organelles do not contain detectable lysosomal hydrolases including cathepsins D and B and glucocerebrosidase. A bovine serum albumin-gold pulse-chase assay followed by ultrastructural analysis suggests a heterogeneity of degradative capacity in LAMP1-labeled endolysosomal organelles. Gradient fractionation displays differential distribution patterns of LAMP1/2 and cathepsins D/B in neurons. We further reveal that LAMP1 intensity in familial amyotrophic lateral sclerosis-linked motor neurons does not necessarily reflect lysosomal deficits in vivo. Our study suggests that labeling a set of lysosomal hydrolases combined with various endolysosomal markers would be more accurate than simply relying on LAMP1/2 staining to assess neuronal lysosome distribution, trafficking, and functionality under physiological and pathological conditions.
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Affiliation(s)
- Xiu-Tang Cheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Yu-Xiang Xie
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Bing Zhou
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Ning Huang
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Tamar Farfel-Becker
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
| | - Zu-Hang Sheng
- Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
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126
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Presynaptic Biogenesis Requires Axonal Transport of Lysosome-Related Vesicles. Neuron 2018; 99:1216-1232.e7. [DOI: 10.1016/j.neuron.2018.08.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 05/18/2018] [Accepted: 08/02/2018] [Indexed: 01/05/2023]
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127
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Abstract
During neural development, growing axons navigate over long distances to reach their targets. A critical step in this process is the regulation of its surface receptors on the axon’s growth cone in response to environmental cues. We focus on how the UNC-5 receptor in Caenorhabditis elegans motor axons is regulated during axon repulsion. By combining C. elegans genetics, biochemistry, and imaging, we found that MAX-1 SUMOylation and AP-3 complex have significant roles in UNC-5–mediated axon repulsion. Our findings reveal how SUMOylation and AP-3–mediated trafficking and degradation interact to help the growing axon find its final target. During neural development, growing axons express specific surface receptors in response to various environmental guidance cues. These axon guidance receptors are regulated through intracellular trafficking and degradation to enable navigating axons to reach their targets. In Caenorhabditis elegans, the UNC-5 receptor is necessary for dorsal migration of developing motor axons. We previously found that MAX-1 is required for UNC-5–mediated axon repulsion, but its mechanism of action remained unclear. Here, we demonstrate that UNC-5–mediated axon repulsion in C. elegans motor axons requires both max-1 SUMOylation and the AP-3 complex β subunit gene, apb-3. Genetic interaction studies show that max-1 is SUMOylated by gei-17/PIAS1 and acts upstream of apb-3. Biochemical analysis suggests that constitutive interaction of MAX-1 and UNC-5 receptor is weakened by MAX-1 SUMOylation and by the presence of APB-3, a competitive interactor with UNC-5. Overexpression of APB-3 reroutes the trafficking of UNC-5 receptor into the lysosome for protein degradation. In vivo fluorescence recovery after photobleaching experiments shows that MAX-1 SUMOylation and APB-3 are required for proper trafficking of UNC-5 receptor in the axon. Our results demonstrate that SUMOylation of MAX-1 plays an important role in regulating AP-3–mediated trafficking and degradation of UNC-5 receptors during axon guidance.
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128
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Khalil B, Morderer D, Price PL, Liu F, Rossoll W. mRNP assembly, axonal transport, and local translation in neurodegenerative diseases. Brain Res 2018; 1693:75-91. [PMID: 29462608 PMCID: PMC5997521 DOI: 10.1016/j.brainres.2018.02.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/31/2018] [Accepted: 02/13/2018] [Indexed: 12/12/2022]
Abstract
The development, maturation, and maintenance of the mammalian nervous system rely on complex spatiotemporal patterns of gene expression. In neurons, this is achieved by the expression of differentially localized isoforms and specific sets of mRNA-binding proteins (mRBPs) that regulate RNA processing, mRNA trafficking, and local protein synthesis at remote sites within dendrites and axons. There is growing evidence that axons contain a specialized transcriptome and are endowed with the machinery that allows them to rapidly alter their local proteome via local translation and protein degradation. This enables axons to quickly respond to changes in their environment during development, and to facilitate axon regeneration and maintenance in adult organisms. Aside from providing autonomy to neuronal processes, local translation allows axons to send retrograde injury signals to the cell soma. In this review, we discuss evidence that disturbances in mRNP transport, granule assembly, axonal localization, and local translation contribute to pathology in various neurodegenerative diseases, including spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's disease (AD).
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Affiliation(s)
- Bilal Khalil
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA
| | - Dmytro Morderer
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA
| | - Phillip L Price
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA; Department of Cell Biology, Emory University, Atlanta, GA 30322 USA
| | - Feilin Liu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA; Eye Center, The Second Hospital of Jilin University, Changchun, Jilin 130021, China
| | - Wilfried Rossoll
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA.
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129
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Snouwaert JN, Church RJ, Jania L, Nguyen M, Wheeler ML, Saintsing A, Mieczkowski P, Manuel de Villena FP, Armao D, Moy SS, Lorenzo DN, Koller BH. A Mutation in the Borcs7 Subunit of the Lysosome Regulatory BORC Complex Results in Motor Deficits and Dystrophic Axonopathy in Mice. Cell Rep 2018; 24:1254-1265. [PMID: 30067980 DOI: 10.1016/j.celrep.2018.06.118] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 05/06/2018] [Accepted: 06/28/2018] [Indexed: 12/13/2022] Open
Abstract
Lysosomes play a critical role in maintenance of the integrity of neuronal function, and mutations in genes that contribute to lysosome formation, transport, and activity are associated with neurodegenerative disorders. Recently, the multisubunit complex, BLOC-one-related complex (BORC), has been shown to be involved in positioning lysosomes within the cytoplasm, although the consequences of altered BORC function in adult animals have not been established. We show that a spontaneous truncation mutation in the mouse Borcs7 gene, identified through whole-genome sequencing followed by genetic complementation, results in progressive axonal dystrophy with dramatic impairment of motor function. Furthermore, mice homozygous for deletion of the entire Borcs7 coding sequence die shortly after birth, and neurons cultured from these animals show impaired centrifugal transport of lysosomes. This identifies BORCS7 as a central factor in axonal transport of lysosomes and a possible target for improving disease-related disturbances in this important function.
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Affiliation(s)
- John N Snouwaert
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Rachel J Church
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Leigh Jania
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - MyTrang Nguyen
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Matthew L Wheeler
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Andrew Saintsing
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Piotr Mieczkowski
- High Throughput Sequencing Facility, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Fernando Pardo Manuel de Villena
- Department of Genetics and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Diane Armao
- Department of Radiology, UNC Healthcare System, Chapel Hill, NC 27599, USA; Department of Pathology and Laboratory Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA; Department of Physician Assistant Studies, Elon University, Elon, NC 27244, USA
| | - Sheryl S Moy
- Department of Psychiatry and Carolina Institute for Developmental Disorders, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Damaris N Lorenzo
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Beverly H Koller
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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130
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Cabukusta B, Neefjes J. Mechanisms of lysosomal positioning and movement. Traffic 2018; 19:761-769. [PMID: 29900632 PMCID: PMC6175085 DOI: 10.1111/tra.12587] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Revised: 06/07/2018] [Accepted: 06/11/2018] [Indexed: 12/12/2022]
Abstract
Lysosomes are highly dynamic organelles that can move rapidly throughout the cell. They distribute in a rather immobile pool located around the microtubule‐organizing center in a “cloud,” and a highly dynamic pool in the cell periphery. Their spatiotemporal characteristics allow them to carry out multiple biological functions, such as cargo degradation, antigen presentation and plasma membrane repair. Therefore, it is not surprising that lysosomal dysfunction underlies various diseases, including cancer, neurodegenerative and autoimmune diseases. In most of these biological events, the involvement of lysosomes is dependent on their ability to move throughout the cytoplasm, to find and fuse to the correct compartments to receive and deliver substrates for further handling. These dynamics are orchestrated by motor proteins moving along cytoskeletal components. The complexity of the mechanisms responsible for controlling lysosomal transport has recently been appreciated and has yielded novel insights into interorganellar communication, as well as lipid‐protein interplay. In this review, we discuss the current understanding of the mechanisms of lysosomal transport and the molecular machineries that control this mobility.
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Affiliation(s)
- Birol Cabukusta
- Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
| | - Jacques Neefjes
- Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands
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131
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Lie PPY, Nixon RA. Lysosome trafficking and signaling in health and neurodegenerative diseases. Neurobiol Dis 2018; 122:94-105. [PMID: 29859318 DOI: 10.1016/j.nbd.2018.05.015] [Citation(s) in RCA: 173] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 04/27/2018] [Accepted: 05/29/2018] [Indexed: 12/20/2022] Open
Abstract
Lysosomes, single-membrane organelles defined by a uniquely strong acidic lumenal pH and high content of acid hydrolases, are the shared degradative compartments of the endocytic and autophagic pathways. These pathways, and especially lysosomes, are points of particular vulnerability in many neurodegenerative diseases. Beyond the role of lysosomes in substrate degradation, new findings have ascribed to lysosomes the leading role in sensing and responding to cellular nutrients, growth factors and cellular stress. This review aims to integrate recent concepts of basic lysosome biology and pathobiology as a basis for understanding neurodegenerative disease pathogenesis. Here, we discuss the newly recognized signaling functions of lysosomes and specific aspects of lysosome biology in neurons while re-visiting the classical defining criteria for lysosomes and the importance of preserving strict definitions. Our discussion emphasizes dynein-mediated axonal transport of maturing degradative organelles, with further consideration of their roles in synaptic function. We finally examine how distinctive underlying disturbances of lysosomes in various neurodegenerative diseases result in unique patterns of auto/endolysosomal mistrafficking. The rapidly emerging understanding of lysosomal trafficking and disruptions in lysosome signaling is providing valuable clues to new targets for disease-modifying therapies.
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Affiliation(s)
- Pearl P Y Lie
- Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, NY 10962, USA; Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA.
| | - Ralph A Nixon
- Center for Dementia Research, Nathan S. Kline Institute, Orangeburg, NY 10962, USA; Department of Psychiatry, New York University Langone Medical Center, New York, NY 10016, USA; Department of Cell Biology, New York University Langone Medical Center, New York, NY 10016, USA; NYU Neuroscience Institute, New York University Langone Medical Center, New York, NY 10016, USA
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132
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Altered distribution of ATG9A and accumulation of axonal aggregates in neurons from a mouse model of AP-4 deficiency syndrome. PLoS Genet 2018; 14:e1007363. [PMID: 29698489 PMCID: PMC5940238 DOI: 10.1371/journal.pgen.1007363] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 05/08/2018] [Accepted: 04/12/2018] [Indexed: 12/22/2022] Open
Abstract
The hereditary spastic paraplegias (HSP) are a clinically and genetically heterogeneous group of disorders characterized by progressive lower limb spasticity. Mutations in subunits of the heterotetrameric (ε-β4-μ4-σ4) adaptor protein 4 (AP-4) complex cause an autosomal recessive form of complicated HSP referred to as "AP-4 deficiency syndrome". In addition to lower limb spasticity, this syndrome features intellectual disability, microcephaly, seizures, thin corpus callosum and upper limb spasticity. The pathogenetic mechanism, however, remains poorly understood. Here we report the characterization of a knockout (KO) mouse for the AP4E1 gene encoding the ε subunit of AP-4. We find that AP-4 ε KO mice exhibit a range of neurological phenotypes, including hindlimb clasping, decreased motor coordination and weak grip strength. In addition, AP-4 ε KO mice display a thin corpus callosum and axonal swellings in various areas of the brain and spinal cord. Immunohistochemical analyses show that the transmembrane autophagy-related protein 9A (ATG9A) is more concentrated in the trans-Golgi network (TGN) and depleted from the peripheral cytoplasm both in skin fibroblasts from patients with mutations in the μ4 subunit of AP-4 and in various neuronal types in AP-4 ε KO mice. ATG9A mislocalization is associated with increased tendency to accumulate mutant huntingtin (HTT) aggregates in the axons of AP-4 ε KO neurons. These findings indicate that the AP-4 ε KO mouse is a suitable animal model for AP-4 deficiency syndrome, and that defective mobilization of ATG9A from the TGN and impaired autophagic degradation of protein aggregates might contribute to neuroaxonal dystrophy in this disorder.
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133
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Abstract
Lysosomes support diverse cellular functions by acting as sites of macromolecule degradation and nutrient recycling. The degradative abilities of lysosomes are conferred by a lumen that is characterized by an acidic pH and which contains numerous hydrolases that support the breakdown of major cellular macromolecules to yield cellular building blocks (amino acids, nucleic acids, sugars, lipids and metals) that are transported into the cytoplasm for their re-use. In addition to these important hydrolytic and recycling functions, lysosomes also serve as a signaling platform that integrates nutrient and metabolic cues to control signaling via the mTORC1 pathway. Due to their extreme longevity, polarity, demands of neurotransmission and metabolic activity, neurons are particularly sensitive to perturbations in lysosome function. The dependence of neurons on optimal lysosome function is highlighted by insights from human genetics that link lysosome dysfunction to a wide range of both rare and common neurological diseases. How then is lysosome function adapted to the unique demands of neurons? This review will focus on the roles played by lysosomes in distinct neuronal sub-compartments, the regulation of neuronal lysosome sub-cellular localization and the implications of such neuronal lysosome regulation for both physiology and disease.
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Affiliation(s)
- Shawn M Ferguson
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, 06510, United States; Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT, 06510, United States.
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134
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Abstract
Lysosomes perform degradative functions that are important for all cells. However, neurons are particularly dependent on optimal lysosome function due to their extremes of longevity, size and polarity. Axons in particular exemplify the major spatial challenges faced by neurons in the maintenance of lysosome biogenesis and function. What impact does this have on the regulation and functions of lysosomes in axons? This review focuses on the mechanisms whereby axonal lysosome biogenesis, transport and function are adapted to meet neuronal demand. Important features include the dynamic relationship between endosomes, autophagosomes and lysosomes as well as the transport mechanisms that support the movement of lysosome precursors in axons. A picture is emerging wherein intermediates in the lysosome maturation processes that would only exist transiently within the crowded confines of a neuronal cell body are spatially and temporally separated over the extreme distances encountered in axons. Axons may thus offer significant opportunities for the analysis of the mechanisms that control lysosome biogenesis. Insights from the genetics and pathology of human neurodegenerative diseases furthermore emphasize the importance of efficient axonal transport of lysosomes and their precursors.
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135
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Gumy LF, Hoogenraad CC. Local mechanisms regulating selective cargo entry and long-range trafficking in axons. Curr Opin Neurobiol 2018; 51:23-28. [PMID: 29510294 DOI: 10.1016/j.conb.2018.02.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/14/2018] [Indexed: 02/02/2023]
Abstract
The polarized long-distance transport of neuronal cargoes depends on the presence of functional and structural axonal subcompartments. Given the heterogeneity of neuronal cargoes, selective sorting and entry occurs in the proximal axon where multiple subcellular specializations such as the axon initial segment, the pre-axonal exclusion zone, the MAP2 pre-axonal filtering zone and the Tau diffusion barrier provide different levels of regulation. Cargoes allowed to pass through the proximal axon spread into the more distal parts. Recent findings show that diverse cargo distributions along the axon depend on the compartmentalized organization of the cytoskeleton and the local regulation of multiple motor proteins by microtubule associated proteins. In this review, we focus on the local mechanisms that control cargo motility and discuss how they play a role in the overall circulation of axonal cargoes.
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Affiliation(s)
- Laura F Gumy
- Department of Anatomy, University of Otago, Dunedin, New Zealand.
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
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136
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Pu J, Keren-Kaplan T, Bonifacino JS. A Ragulator-BORC interaction controls lysosome positioning in response to amino acid availability. J Cell Biol 2017; 216:4183-4197. [PMID: 28993468 PMCID: PMC5716277 DOI: 10.1083/jcb.201703094] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 08/10/2017] [Accepted: 08/25/2017] [Indexed: 11/22/2022] Open
Abstract
Lysosomes play key roles in the cellular response to amino acid availability. Depletion of amino acids from the medium turns off a signaling pathway involving the Ragulator complex and the Rag guanosine triphosphatases (GTPases), causing release of the inactive mammalian target of rapamycin complex 1 (mTORC1) serine/threonine kinase from the lysosomal membrane. Decreased phosphorylation of mTORC1 substrates inhibits protein synthesis while activating autophagy. Amino acid depletion also causes clustering of lysosomes in the juxtanuclear area of the cell, but the mechanisms responsible for this phenomenon are poorly understood. Herein we show that Ragulator directly interacts with BLOC-1-related complex (BORC), a multi-subunit complex previously found to promote lysosome dispersal through coupling to the small GTPase Arl8 and the kinesins KIF1B and KIF5B. Interaction with Ragulator exerts a negative regulatory effect on BORC that is independent of mTORC1 activity. Amino acid depletion strengthens this interaction, explaining the redistribution of lysosomes to the juxtanuclear area. These findings thus demonstrate that amino acid availability controls lysosome positioning through Ragulator-dependent, but mTORC1-independent, modulation of BORC.
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Affiliation(s)
- Jing Pu
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
| | - Tal Keren-Kaplan
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
| | - Juan S Bonifacino
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
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137
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Terenzio M, Schiavo G, Fainzilber M. Compartmentalized Signaling in Neurons: From Cell Biology to Neuroscience. Neuron 2017; 96:667-679. [PMID: 29096079 DOI: 10.1016/j.neuron.2017.10.015] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 09/27/2017] [Accepted: 10/09/2017] [Indexed: 12/18/2022]
Abstract
Neurons are the largest known cells, with complex and highly polarized morphologies. As such, neuronal signaling is highly compartmentalized, requiring sophisticated transfer mechanisms to convey and integrate information within and between sub-neuronal compartments. Here, we survey different modes of compartmentalized signaling in neurons, highlighting examples wherein the fundamental cell biological processes of protein synthesis and degradation, membrane trafficking, and organelle transport are employed to enable the encoding and integration of information, locally and globally within a neuron. Comparisons to other cell types indicate that neurons accentuate widely shared mechanisms, providing invaluable models for the compartmentalization and transfer mechanisms required and used by most eukaryotic cells.
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Affiliation(s)
- Marco Terenzio
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Giampietro Schiavo
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N 3BG, UK; Discoveries Centre for Regenerative and Precision Medicine at UCL, London WC1N 3BG, UK; UK Dementia Research Institute at UCL, London WC1E 6BT, UK
| | - Mike Fainzilber
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot 76100, Israel.
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138
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Hartwig C, Monis WJ, Chen X, Dickman DK, Pazour GJ, Faundez V. Neurodevelopmental disease mechanisms, primary cilia, and endosomes converge on the BLOC-1 and BORC complexes. Dev Neurobiol 2017; 78:311-330. [PMID: 28986965 DOI: 10.1002/dneu.22542] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 09/08/2017] [Accepted: 09/15/2017] [Indexed: 12/12/2022]
Abstract
The biogenesis of lysosome-related organelles complex-1 (BLOC-1) and the bloc-one-related complex (BORC) are the cytosolic protein complexes required for specialized membrane protein traffic along the endocytic route and the spatial distribution of endosome-derived compartments, respectively. BLOC-1 and BORC complex subunits and components of their interactomes have been associated with the risk and/or pathomechanisms of neurodevelopmental disorders. Thus, cellular processes requiring BLOC-1 and BORC interactomes have the potential to offer novel insight into mechanisms underlying behavioral defects. We focus on interactions between BLOC-1 or BORC subunits with the actin and microtubule cytoskeleton, membrane tethers, and SNAREs. These interactions highlight requirements for BLOC-1 and BORC in membrane movement by motors, control of actin polymerization, and targeting of membrane proteins to specialized cellular domains such as the nerve terminal and the primary cilium. We propose that the endosome-primary cilia pathway is an underappreciated hub in the genesis and mechanisms of neurodevelopmental disorders. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 311-330, 2018.
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Affiliation(s)
- Cortnie Hartwig
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322
| | - William J Monis
- Program in Molecular Medicine, University of Massachusetts Medical School, Biotech II, Worcester, Massachusetts, 01605
| | - Xun Chen
- Department of Biology, Neurobiology Section, University of Southern California, Los Angeles, California, 90089
| | - Dion K Dickman
- Department of Biology, Neurobiology Section, University of Southern California, Los Angeles, California, 90089
| | - Gregory J Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Biotech II, Worcester, Massachusetts, 01605
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, Georgia, 30322
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139
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Nirschl JJ, Ghiretti AE, Holzbaur ELF. The impact of cytoskeletal organization on the local regulation of neuronal transport. Nat Rev Neurosci 2017; 18:585-597. [PMID: 28855741 DOI: 10.1038/nrn.2017.100] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Neurons are akin to modern cities in that both are dependent on robust transport mechanisms. Like the best mass transit systems, trafficking in neurons must be tailored to respond to local requirements. Neurons depend on both high-speed, long-distance transport and localized dynamics to correctly deliver cargoes and to tune synaptic responses. Here, we focus on the mechanisms that provide localized regulation of the transport machinery, including the cytoskeleton and molecular motors, to yield compartment-specific trafficking in the axon initial segment, axon terminal, dendrites and spines. The synthesis of these mechanisms provides a sophisticated and responsive transit system for the cell.
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Affiliation(s)
- Jeffrey J Nirschl
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
| | - Amy E Ghiretti
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 638A Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA
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140
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Niwa S, Tao L, Lu SY, Liew GM, Feng W, Nachury MV, Shen K. BORC Regulates the Axonal Transport of Synaptic Vesicle Precursors by Activating ARL-8. Curr Biol 2017; 27:2569-2578.e4. [PMID: 28823680 DOI: 10.1016/j.cub.2017.07.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 06/09/2017] [Accepted: 07/06/2017] [Indexed: 12/23/2022]
Abstract
Axonal transport of synaptic vesicle precursors (SVPs) is essential for synapse development and function. The conserved ARF-like small GTPase ARL-8 is localized to SVPs and directly activates UNC-104/KIF1A, the axonal-transport kinesin for SVPs in C. elegans. It is not clear how ARL-8 is activated in this process. Here we show that part of the BLOC-1-related complex (BORC), previously shown to regulate lysosomal transport, is required to recruit and activate ARL-8 on SVPs. We found mutations in six BORC subunits-blos-1/BLOS1, blos-2/BLOS2, snpn-1/Snapin, sam-4/Myrlysin, blos-7/Lyspersin, and blos-9/MEF2BNB-cause defects in axonal transport of SVPs, leading to ectopic accumulation of synaptic vesicles in the proximal axon. This phenotype is suppressed by constitutively active arl-8 or unc-104 mutants. Furthermore, SAM-4/Myrlysin, a subunit of BORC, promotes the GDP-to-GTP exchange of ARL-8 in vitro and recruits ARL-8 onto SVPs in vivo. Thus, BORC regulates the axonal transport of synaptic materials and synapse formation by controlling the nucleotide state of ARL-8. Interestingly, the other two subunits of BORC essential for lysosomal transport, kxd-1/KXD1 and blos-8/Diaskedin, are not required for the SVP transport, suggesting distinct subunit requirements for lysosomal and SVP trafficking.
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Affiliation(s)
- Shinsuke Niwa
- Frontier Research Institute for Interdisciplinary Sciences and Graduate School of Life Sciences, Tohoku University, Aramaki Aza Aoba 6-3, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
| | - Li Tao
- Howard Hughes Medical Institute, Department of Biology, Stanford University, 385 Serra Mall, Stanford, CA 94305, USA
| | - Sharon Y Lu
- Howard Hughes Medical Institute, Department of Biology, Stanford University, 385 Serra Mall, Stanford, CA 94305, USA
| | - Gerald M Liew
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
| | - Wei Feng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China
| | - Maxence V Nachury
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA.
| | - Kang Shen
- Howard Hughes Medical Institute, Department of Biology, Stanford University, 385 Serra Mall, Stanford, CA 94305, USA; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China.
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141
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Gowrishankar S, Wu Y, Ferguson SM. Impaired JIP3-dependent axonal lysosome transport promotes amyloid plaque pathology. J Cell Biol 2017; 216:3291-3305. [PMID: 28784610 PMCID: PMC5626538 DOI: 10.1083/jcb.201612148] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 05/18/2017] [Accepted: 07/06/2017] [Indexed: 12/29/2022] Open
Abstract
Axonal lysosomes accumulate abnormally in Alzheimer’s disease brains. However, whether and how such lysosomes contribute to disease pathology has been unclear. Gowrishankar et al. show that the JIP3-dependent transport of axonal lysosomes negatively regulates amyloid precursor protein processing into amyloidogenic peptides. Lysosomes robustly accumulate within axonal swellings at Alzheimer’s disease (AD) amyloid plaques. However, the underlying mechanisms and disease relevance of such lysosome accumulations are not well understood. Motivated by these problems, we identified JNK-interacting protein 3 (JIP3) as an important regulator of axonal lysosome transport and maturation. JIP3 knockout mouse neuron primary cultures accumulate lysosomes within focal axonal swellings that resemble the dystrophic axons at amyloid plaques. These swellings contain high levels of amyloid precursor protein processing enzymes (BACE1 and presenilin 2) and are accompanied by elevated Aβ peptide levels. The in vivo importance of the JIP3-dependent regulation of axonal lysosomes was revealed by the worsening of the amyloid plaque pathology arising from JIP3 haploinsufficiency in a mouse model of AD. These results establish the critical role of JIP3-dependent axonal lysosome transport in regulating amyloidogenic amyloid precursor protein processing and support a model wherein Aβ production is amplified by plaque-induced axonal lysosome transport defects.
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Affiliation(s)
- Swetha Gowrishankar
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT.,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
| | - Yumei Wu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT.,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
| | - Shawn M Ferguson
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT .,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
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