INSERM U950, Membrane Traffic in Neuronal & Epithelial Morphogenesis, Paris, F-75013, France.
J Cell Sci. 2010 Mar 1;123(Pt 5):723-35. doi: 10.1242/jcs.062497. Epub 2010 Feb 9.
The v-SNARE TI-VAMP (VAMP7) mediates exocytosis during neuritogenesis, phagocytosis and lysosomal secretion. It localizes to endosomes and lysosomes but also to the trans-Golgi network. Here we show that depletion of TI-VAMP enhances the endocytosis of activated EGF receptor (EGFR) without affecting constitutive endocytosis of EGFR, or transferrin uptake. This increased EGFR internalization is mainly clathrin dependent. Searching for defects in EGFR regulators, we found that TI-VAMP depletion reduces the cell surface amount of CD82, a tetraspanin known to control EGFR localization in microdomains. We further show that TI-VAMP is required for secretion from the Golgi apparatus to the cell surface, and that TI-VAMP-positive vesicles transport CD82. Quantum dots video-microscopy indicates that depletion of TI-VAMP, or its cargo CD82, restrains EGFR diffusion and the area explored by EGFR at the cell surface. Both depletions also impair MAPK signaling and enhance endocytosis of activated EGFR by increased recruitment of AP-2. These results highlight the role of TI-VAMP in the secretory pathway of a tetraspanin, and support a model in which CD82 allows EGFR entry in microdomains that control its clathrin-dependent endocytosis and signaling.
v-SNARE TI-VAMP（VAMP7）在神经突发生、吞噬作用和溶酶体分泌过程中介导胞吐作用。它定位于内体和溶酶体，但也定位于高尔基体内网络。在这里，我们表明 TI-VAMP 的耗竭增强了激活的表皮生长因子受体 (EGFR) 的内吞作用，而不影响 EGFR 的组成性内吞作用或转铁蛋白摄取。这种增强的 EGFR 内化主要依赖于网格蛋白。在寻找 EGFR 调节剂的缺陷时，我们发现 TI-VAMP 耗竭会减少四跨膜蛋白 CD82 的细胞表面数量，CD82 是一种已知控制 EGFR 在微区定位的四跨膜蛋白。我们进一步表明，TI-VAMP 是从高尔基体到细胞表面分泌所必需的，并且 TI-VAMP 阳性囊泡运输 CD82。量子点视频显微镜表明，TI-VAMP 的耗竭或其货物 CD82 会限制 EGFR 的扩散和 EGFR 在细胞表面上的探索区域。两种耗竭也会损害 MAPK 信号传导，并通过增加 AP-2 的募集来增强激活的 EGFR 的内吞作用。这些结果突出了 TI-VAMP 在四跨膜蛋白分泌途径中的作用，并支持 CD82 允许 EGFR 进入控制其网格蛋白依赖性内吞作用和信号转导的微区的模型。
