Syntaxin-1/TI-VAMP SNAREs interact with Trk receptors and are required for neurotrophin-dependent outgrowth

Abstract

SNARE proteins are essential components of the machinery that regulates vesicle trafficking and exocytosis. Their role is critical for the membrane-fusion processes that occur during neurotransmitter release. However, research in the last decade has also unraveled the relevance of these proteins in membrane expansion and cytoskeletal rearrangements during developmental processes such as neuronal migration and growth cone extension and attraction. Neurotrophins are neurotrophic factors that are required for many cellular functions throughout the brain, including neurite outgrowth and guidance, synaptic formation, and plasticity. Here we show that neurotrophin Trk receptors form a specific protein complex with the t-SNARE protein Syntaxin 1, both in vivo and in vitro. We also demonstrate that blockade of Syntaxin 1 abolishes neurotrophin-dependent growth of axons in neuronal cultures and decreases exocytotic events at the tip of axonal growth cones. 25-kDa soluble N-ethylmaleimide-sensitive factor attachment protein and Vesicle-associated membrane protein 2 do not participate in the formation of this SNARE complex, while tetanus neurotoxin-insensitive vesicle-associated membrane protein interacts with Trk receptors; knockdown of this (v) SNARE impairs Trk-dependent outgrowth. Taken together, our results support the notion that an atypical SNARE complex comprising Syntaxin 1 and tetanus neurotoxin-insensitive vesicle-associated membrane protein is required for axonal neurotrophin function.

TRIM67 Regulates Exocytic Mode and Neuronal Morphogenesis via SNAP47

“…The accuracy of our model decreased somewhat at 3 DIV, suggesting additional parameters in membrane remodeling were not captured. Perhaps analogously, in vivo Vamp2 -/- neurons have a largely normal morphology, suggesting compensatory mechanisms such as membrane added via ER-PM contact sites or exocytosis mediated by other SNARE proteins like VAMP7 (Fuschini et al, 2018; Galli et al, 1998) participate in membrane remodeling.…”

Syntaxin-1 is necessary for UNC5/Netrin-1-dependent macropinocytosis and chemorepulsion

“…VAMP-2 function is required for repulsion to class III semaphorins (Zylbersztejn et al, 2012). We have previously described how Stx1 mediates ligand-dependent exocytosis and attraction to neurotrophic factors (Fuschini et al, 2018) and Netrin-1 (Cotrufo et al, 2012;Cotrufo et al, 2011) through the interaction with Trk receptors and DCC, respectively. Here we describe how Stx1 interacts directly with the repulsive Netrin-1 receptor UNC5.…”

“…We have previously demonstrated that the t-SNARE Stx1 interacts with the guidance receptor DCC (Cotrufo et al, 2012;Cotrufo et al, 2011) and the tropomyosinrelated kinase (TrkB) receptor (Fuschini et al, 2018), with these associations being necessary for the Netrin-1-dependent chemoattraction and neurotrophin-dependent outgrowth of axons, respectively. These results indicate that Stx1 regulates exocytosis and membrane retrieval in growth cones, and is required for Netrin-1-induced chemotropic guidance in vitro and in vivo (Ros et al, 2015).…”

TRIM67 regulates exocytic mode and neuronal morphogenesis via SNAP47

“…We conclude that VAMP2-mediated fusion is the primary source of membrane addition in developing neurons and that manipulating exocytic frequency or mode alters neuronal growth. Perhaps analogously, in vivo Vamp2 À/À neurons have a largely normal morphology, suggesting compensatory mechanisms such as membrane added by endoplasmic reticulum (ER)-PM contact sites or exocytosis mediated by other SNARE proteins like VAMP7 (Fuschini et al, 2018;Galli et al, 1998) participate in remodeling.…”