Role of tetanus neurotoxin insensitive vesicle-associated membrane protein in membrane domains transport and homeostasis

Abstract

Keywords: exocytosis, Golgi apparatus, SNARE, sphingolipids, TI-VAMP/VAMP7 Abbreviations: BFA, Brefeldin A; Cer, Ceramide; ER, Endoplasmic Reticulum; GlcCer, Glucosylceramide; GM3, ganglioside monosialic acid 3; GPI, Glycosylphosphatidylinositol; GSL, Glycosphingolipids; LC, Long Chain; PI, Phosphatidylinositide; PM, Plasma Membrane; SM, Sphingomyelin; TGN, D Trans-Golgi Network; TI-VAMP/VAMP7, Tetanus neurotoxin-insensitive vesicle-associated membrane protein / Vesicle associated membrane protein 7; VLC, very long vhain; VSVG, Vesicular Stomatitis Virus GlycoproteinBiological membranes in eukaryotes contain a large variety of proteins and lipids often distributed in domains in plasma membrane and endomembranes. Molecular mechanisms responsible for the transport and the organization of these membrane domains along the secretory pathway still remain elusive. Here we show that vesicular SNARE TI-VAMP/VAMP7 plays a major role in membrane domains composition and transport. We found that the transport of exogenous and endogenous GPI-anchored proteins was altered in fibroblasts isolated from VAMP7-knockout mice. Furthermore, disassembly and reformation of the Golgi apparatus induced by Brefeldin A treatment and washout were impaired in VAMP7-depleted cells, suggesting that loss of VAMP7 expression alters biochemical properties and dynamics of the Golgi apparatus. In addition, lipid profiles from these knockout cells indicated a defect in glycosphingolipids homeostasis. We conclude that VAMP7 is required for effective transport of GPI-anchored proteins to cell surface and that VAMP7-dependent transport contributes to both sphingolipids and Golgi homeostasis.

Biomechanical control of lysosomal secretion via the VAMP7 hub: a tug-of-war mechanism between VARP and LRRK1

“…VAMP7 was shown to be important for phagophore formation and autophagosome secretion (Fader et al, 2012; Moreau et al, 2011) and rigidity was shown to increase autophagy (Ulbricht et al, 2013) but we did not find significant LC3-II induction in the different conditions tested so we do not think that substrate stiffness significantly activated autophagy in our experimental conditions. More likely we think our findings are related to the previous demonstration that VAMP7 mediates the transport of GPI-anchored proteins and lipid microdomains to the plasma membrane (Lafont et al, 1999; Molino et al, 2015; Pocard et al, 2007). Accordingly, increased exocytosis of GPI-anchored proteins was found in the secondary contractile phase during cell spreading (Gauthier et al, 2011).…”

“…Interestingly enough, VAMP7 was shown to play an essential role in cell migration and invasion (Proux-Gillardeaux et al, 2007; Steffen et al, 2008; Williams and Coppolino, 2011). VAMP7 also contributes into the regulation of membrane composition of sphingolipids and GPI-anchored protein (Molino et al, 2015), which in turn modulates integrin dynamic and adhesion (Eich et al, 2016; van Zanten et al, 2009).…”

Reciprocal link between cell biomechanics and exocytosis

“…The vesicular SNARE VAMP7 was shown to mediate the transport of PrPc, a GPI-anchored protein to the cell surface and its knockout leads to the impaired cellular content of different ganglioside monosialic acid 3 (GM3) species containing long (C16-18) or very long acyl chain (C ≥ 20, VLC), and very long sphingomyelin (SM) with a preferential channeling of very long chain ceramides precursors to form VLC-GM3 and concomitant reduction of VLC-SM in VAMP7-knockout fibroblasts. 88 Thus, the VAMP7 knockout was hypothesized to carry defective biomechanical properties, a hypothesis supported by our recent data. 42 Altogether, we conclude that integrin sensing of the cell environment, particularly rigidity, likely regulates the exocytosis of endosomes which could bring specific sets of lipids and proteins which could allow the cell to adapt to an increased surface area ( Figure 2).…”

“…Interestingly enough, GEECs have a lipid content rich in glycosphingolipids which generates more ordered membrane microdomains thus could allow the cell to adapt to the increased surface. The vesicular SNARE VAMP7 was shown to mediate the transport of PrPc, a GPI‐anchored protein to the cell surface and its knockout leads to the impaired cellular content of different ganglioside monosialic acid 3 (GM3) species containing long (C16‐18) or very long acyl chain (C ≥ 20, VLC), and very long sphingomyelin (SM) with a preferential channeling of very long chain ceramides precursors to form VLC‐GM3 and concomitant reduction of VLC‐SM in VAMP7‐knockout fibroblasts . Thus, the VAMP7 knockout was hypothesized to carry defective biomechanical properties, a hypothesis supported by our recent data …”

Membrane traffic during axon development

“…Interestingly, Vamp7 exocytosis is stimulated by Reelin (Bal et al, ), Insulin and IGF‐1 (Burgo et al, ), all important signals for axonal growth and neuronal differentiation. Noteworthy, Vamp7‐KO MEFs show strong defects of Golgi to cell surface transport, particularly GPI‐anchored proteins including the Prion protein, Golgi dynamics, and membrane microdomain lipid defects (Molino et al, ), all phenotypic traits that may be expected to translate into impairment in neuronal development, at least in some subtypes. Furthermore, the exocyst‐dependent membrane delivery may be involved in neurite growth via the secretion of Prion protein (Bodrikov et al, ), a process which likely involves Vamp7 (Molino et al, ).…”