A novel Netrin-1-sensitive mechanism promotes local SNARE-mediated exocytosis during axon branching.
Developmental axon branching dramatically increases synaptic capacity and neuronal surface area. Netrin-1 promotes branching and synaptogenesis, but the mechanism by which Netrin-1 stimulates plasma membrane expansion is unknown. We demonstrate that SNARE-mediated exocytosis is a prerequisite for axon branching and identify the E3 ubiquitin ligase TRIM9 as a critical catalytic link between Netrin-1 and exocytic SNARE machinery in murine cortical neurons. TRIM9 ligase activity promotes SNARE-mediated vesicle fusion and axon branching in a Netrin-dependent manner. We identified a direct interaction between TRIM9 and the Netrin-1 receptor DCC as well as a Netrin-1-sensitive interaction between TRIM9 and the SNARE component SNAP25. The interaction with SNAP25 negatively regulates SNARE-mediated exocytosis and axon branching in the absence of Netrin-1. Deletion of TRIM9 elevated exocytosis in vitro and increased axon branching in vitro and in vivo. Our data provide a novel model for the spatial regulation of axon branching by Netrin-1, in which localized plasma membrane expansion occurs via TRIM9-dependent regulation of SNARE-mediated vesicle fusion.
Neuroscience Center and Curriculum in Neurobiology, 2 Department of Cell Biology and Physiology, and 3 Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599.
Cortney C
CC
Winkle
Leslie M
LM
McClain
Juli G
JG
Valtschanoff
Charles S
CS
Park
Christopher
C
Maglione
Stephanie L
SL
Gupton
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D000075388:Netrin-1; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism*; D000070584:Tripartite Motif Proteins; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; C000617351:NTN1 protein, human; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; C000617353:Ntn1 protein, mouse; C494208:SNAP25 protein, human; C494209:Snap25 protein, mouse; D050825:Synaptosomal-Associated Protein 25; D000070584:Tripartite Motif Proteins; D025521:Tumor Suppressor Proteins; D000075388:Netrin-1; C550446:TRIM9 protein, human; C469337:Trim9 protein, mouse; D044767:Ubiquitin-Protein Ligases