Martinez-Arca Sonia, Rudge Rachel, Vacca Marcella, Raposo Graça, Camonis Jacques, Proux-Gillardeaux Véronique, Daviet Laurent, Formstecher Etienne, Hamburger Alexandre, Filippini Francesco, D'Esposito Maurizio, Galli Thierry
Membrane Traffic and Neuronal Plasticity, Institut National de la Santé et de la Recherche Médicale U536, Institut du Fer-à-Moulin, 75005 Paris, France.
Proc Natl Acad Sci U S A. 2003 Jul 22;100(15):9011-6. doi: 10.1073/pnas.1431910100. Epub 2003 Jul 9.
SNARE [soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor] proteins are essential for membrane fusion but their regulation is not yet fully understood. We have previously shown that the amino-terminal Longin domain of the v-SNARE TI-VAMP (tetanus neurotoxin-insensitive vesicle-associated membrane protein)/VAMP7 plays an inhibitory role in neurite outgrowth. The goal of this study was to investigate the regulation of TI-VAMP as a model of v-SNARE regulation. We show here that the Longin domain (LD) plays a dual role. First, it negatively regulates the ability of TI-VAMP and of a Longin/Synaptobrevin chimera to participate in SNARE complexes. Second, it interacts with the adaptor complex AP-3 and this interaction targets TI-VAMP to late endosomes. Accordingly, in mocha cells lacking AP-3 delta, TI-VAMP is retained in an early endosomal compartment. Furthermore, TI-VAMPc, an isoform of TI-VAMP lacking part of the LD, does not interact with AP-3, and therefore is not targeted to late endosomes; however, this shorter LD still inhibits SNARE-complex formation. These findings support a mechanism controlling both localization and function of TI-VAMP through the LD and clathrin adaptors. Moreover, they point to the amino-terminal domains of SNARE proteins as multifunctional modules responsible for the fine tuning of SNARE function.
SNARE[可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体]蛋白对于膜融合至关重要，但其调控机制尚未完全明确。我们先前已经表明，v-SNARE TI-VAMP（破伤风神经毒素不敏感的囊泡相关膜蛋白）/VAMP7的氨基末端Longin结构域在神经突生长中起抑制作用。本研究的目的是研究TI-VAMP作为v-SNARE调控模型的调控机制。我们在此表明，Longin结构域（LD）具有双重作用。首先，它负向调节TI-VAMP以及Longin/突触融合蛋白嵌合体参与SNARE复合体的能力。其次，它与衔接蛋白复合体AP-3相互作用，这种相互作用将TI-VAMP靶向晚期内体。因此，在缺乏AP-3δ的mocha细胞中，TI-VAMP保留在早期内体区室中。此外，TI-VAMPc是TI-VAMP的一种异构体，缺少部分LD，不与AP-3相互作用，因此不被靶向晚期内体；然而，这种较短的LD仍然抑制SNARE复合体的形成。这些发现支持了一种通过LD和网格蛋白衔接蛋白控制TI-VAMP定位和功能的机制。此外，它们指出SNARE蛋白的氨基末端结构域是负责精细调节SNARE功能的多功能模块。
