title: Transport of the major myelin proteolipid protein is directed by VAMP3 and VAMP7.
abstract: CNS myelination by oligodendrocytes requires directed transport of myelin membrane components and a timely and spatially controlled membrane expansion. In this study, we show the functional involvement of the R-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (R-SNARE) proteins VAMP3/cellubrevin and VAMP7/TI-VAMP in myelin membrane trafficking. VAMP3 and VAMP7 colocalize with the major myelin proteolipid protein (PLP) in recycling endosomes and late endosomes/lysosomes, respectively. Interference with VAMP3 or VAMP7 function using small interfering RNA-mediated silencing and exogenous expression of dominant-negative proteins diminished transport of PLP to the oligodendroglial cell surface. In addition, the association of PLP with myelin-like membranes produced by oligodendrocytes cocultured with cortical neurons was reduced. We furthermore identified Syntaxin-4 and Syntaxin-3 as prime acceptor Q-SNAREs of VAMP3 and VAMP7, respectively. Analysis of VAMP3-deficient mice revealed no myelination defects. Interestingly, AP-3δ-deficient mocha mice, which suffer from impaired secretion of lysosome-related organelles and missorting of VAMP7, exhibit a mild dysmyelination characterized by reduced levels of select myelin proteins, including PLP. We conclude that PLP reaches the cell surface via at least two trafficking pathways with distinct regulations: (1) VAMP3 mediates fusion of recycling endosome-derived vesicles with the oligodendroglial plasma membrane in the course of the secretory pathway; (2) VAMP7 controls exocytosis of PLP from late endosomal/lysosomal organelles as part of a transcytosis pathway. Our in vivo data suggest that exocytosis of lysosome-related organelles controlled by VAMP7 contributes to myelin biogenesis by delivering cargo to the myelin membrane.
authors.affiliation: Department of Biology, Molecular Cell Biology, University of Mainz, D-55128 Mainz, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Feldmann
authors.forename: Jesa
authors.initials: J
authors.lastname: Amphornrat
authors.forename: Madeleine
authors.initials: M
authors.lastname: Schönherr
authors.forename: Christine
authors.initials: C
authors.lastname: Winterstein
authors.forename: Wiebke
authors.initials: W
authors.lastname: Möbius
authors.forename: Torben
authors.initials: T
authors.lastname: Ruhwedel
authors.forename: Lydia
authors.initials: L
authors.lastname: Danglot
authors.forename: Klaus-Armin
authors.initials: KA
authors.lastname: Nave
authors.forename: Thierry
authors.initials: T
authors.lastname: Galli
authors.forename: Dieter
authors.initials: D
authors.lastname: Bruns
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Trotter
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Krämer-Albers
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D011992:Endosomes / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005089:Exocytosis / Q000502:physiology; D005260:Female; D005822:Genetic Vectors; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016253:Microscopy, Immunoelectron; D018991:Myelin Proteolipid Protein / Q000378:metabolism*; D009186:Myelin Sheath / Q000378:metabolism; D050683:R-SNARE Proteins / Q000378:metabolism*; D034622:RNA Interference; D014162:Transfection; D051040:Vesicle-Associated Membrane Protein 3 / Q000378:metabolism*
chemical_list: D018991:Myelin Proteolipid Protein; D050683:R-SNARE Proteins; C496927:Sybl1 protein, mouse; D051040:Vesicle-Associated Membrane Protein 3