Pocard Thomas, Le Bivic André, Galli Thierry, Zurzolo Chiara
Unité de Trafic Membranaire et Pathogenèse, Institut Pasteur, 75724, Paris CEDEX 15, France.
J Cell Sci. 2007 Sep 15;120(Pt 18):3309-20. doi: 10.1242/jcs.007948.
SNARE [soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor] proteins control the membrane-fusion events of eukaryotic membrane-trafficking pathways. Specific vesicular and target SNAREs operate in specific trafficking routes, but the degree of specificity of SNARE functions is still elusive. Apical fusion requires the polarized distribution at the apical surface of the t-SNARE syntaxin 3, and several v-SNAREs including TI-VAMP and VAMP8 operate at the apical plasma membrane in polarized epithelial cells. It is not known, however, whether specific v-SNAREs are involved in direct and indirect routes to the apical surface. Here, we used RNAi to assess the role of two tetanus-neurotoxin-insensitive v-SNAREs, TI-VAMP/VAMP7 and VAMP8, in the sorting of raft- and non-raft-associated apical markers that follow either a direct or a transcytotic delivery, respectively, in FRT or Caco2 cells. We show that TI-VAMP mediates the direct apical delivery of both raft- and non-raft-associated proteins. By contrast, sorting by means of the transcytotic pathway is not affected by TI-VAMP knockdown but does appear to be regulated by VAMP8. Together with the specific role of VAMP3 in basolateral transport, our results demonstrate a high degree of specificity in v-SNARE function in polarized cells.
SNARE（可溶性N - 乙基马来酰亚胺敏感因子（NSF）附着蛋白（SNAP）受体）蛋白控制真核细胞膜运输途径中的膜融合事件。特定的囊泡SNARE和靶标SNARE在特定的运输途径中发挥作用，但SNARE功能的特异性程度仍不清楚。顶端融合需要t - SNARE syntaxin 3在顶端表面的极化分布，并且包括TI - VAMP和VAMP8在内的几种v - SNARE在极化上皮细胞的顶端质膜发挥作用。然而，尚不清楚特定的v - SNARE是否参与到顶端表面的直接和间接途径。在这里，我们使用RNA干扰来评估两种对破伤风神经毒素不敏感的v - SNARE，TI - VAMP / VAMP7和VAMP8，在FRT或Caco2细胞中分别沿着直接或转胞吞途径递送的与筏和非筏相关的顶端标记物分选过程中的作用。我们表明，TI - VAMP介导了与筏和非筏相关蛋白的直接顶端递送。相比之下，通过转胞吞途径的分选不受TI - VAMP敲低的影响，但似乎受VAMP8调节。连同VAMP3在基底外侧运输中的特定作用，我们的结果证明了极化细胞中v - SNARE功能具有高度特异性。
