title: Activity-Dependent Degradation of Synaptic Vesicle Proteins Requires Rab35 and the ESCRT Pathway.
abstract: Synaptic vesicle (SV) pools must maintain a functional repertoire of proteins to efficiently release neurotransmitter. The accumulation of old or damaged proteins on SV membranes is linked to synaptic dysfunction and neurodegeneration. However, despite the importance of SV protein turnover for neuronal health, the molecular mechanisms underlying this process are largely unknown. Here, we have used dissociated rat hippocampal neurons to investigate the pathway for SV protein degradation. We find that neuronal activity drives the degradation of a subset of SV proteins and that the endosomal sorting complex required for transport (ESCRT) machinery and SV-associated GTPase Rab35 are key elements of this use-dependent degradative pathway. Specifically, neuronal activity induces Rab35 activation and binding to the ESCRT-0 protein Hrs, which we have identified as a novel Rab35 effector. These actions recruit the downstream ESCRT machinery to SV pools, thereby initiating SV protein degradation via the ESCRT pathway. Our findings show that the Rab35/ESCRT pathway facilitates the activity-dependent removal of specific proteins from SV pools, thereby maintaining presynaptic protein homeostasis.
  
  
  
  Synaptic transmission is mediated by the release of chemical neurotransmitters from synaptic vesicles (SVs). This tightly regulated process requires a functional pool of SVs, necessitating cellular mechanisms for removing old or damaged proteins that could impair SV cycling. Here, we show that a subset of SV proteins is degraded in an activity-dependent manner and that key steps in this degradative pathway are the activation of the small GTPase Rab35 and the subsequent recruitment of the endosomal sorting complex required for transport (ESCRT) machinery to SV pools. Further, we demonstrate that ESCRT-0 component Hrs is an effector of Rab35, thus providing novel mechanistic insight into the coupling of neuronal activity with SV protein degradation and the maintenance of functional SV pools.
authors.affiliation: Department of Pathology and Cell Biology and.
authors.forename: Patricia
authors.initials: P
authors.lastname: Sheehan
authors.affiliation: Department of Pathology and Cell Biology and.
authors.forename: Mei
authors.initials: M
authors.lastname: Zhu
authors.affiliation: Department of Pathology and Cell Biology and.
authors.forename: Anne
authors.initials: A
authors.lastname: Beskow
authors.affiliation: Department of Pathology and Cell Biology and.
authors.forename: Cyndel
authors.identifier: 0000-0001-5192-0796
authors.initials: C
authors.lastname: Vollmer
authors.affiliation: Department of Pathology and Cell Biology and Department of Neuroscience, Columbia University Medical Center, New York, New York 10032 cw2622@cumc.columbia.edu.
authors.forename: Clarissa L
authors.identifier: 0000-0003-4263-5576
authors.initials: CL
authors.lastname: Waites
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D004622:Embryo, Mammalian; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D018846:Excitatory Amino Acids / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000235:genetics / Q000502:physiology; D005260:Female; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology*; D006801:Humans; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000502:physiology* / Q000648:ultrastructure; D020733:RNA, Small Cytoplasmic / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D018846:Excitatory Amino Acids; D009419:Nerve Tissue Proteins; D020733:RNA, Small Cytoplasmic; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C056639:2-amino-5-phosphopentanoic acid; C575759:Rab35 protein, rat; D020691:rab GTP-Binding Proteins; D014633:Valine
keywords: ESCRT; Hrs; Rab35; SV2; VAMP2; synaptic vesicle