Membrane protein sequestering by ionic protein- lipid interactions

摘要

Neuronal exocytosis is catalysed by the SNAP receptor protein syntaxin-lA, which is clustered in the plasma membrane at sites where synaptic vesicles undergo exocytosis23. However, how syntaxin-lA is sequestered is unknown. Here we show that syntaxin clustering is mediated by electrostatic interactions with the strongly anionic lipid phosphatidylinositol-4,5-bisphosphate (PIP2). Using super-resolution stimulated-emission depletion microscopy on the plasma membranes of PC 12 cells, we found that PIP2 is the dominant inner-leaflet lipid in microdomains about 73 nanometres in size. This high accumulation of PIP2 was required for syntaxin-1A sequestering, as destruction of PIP2 by the phosphatase synaptojanin-1 reduced syntaxin-1A clustering. Furthermore, co-reconstitution of PIP2 and the carboxy-terminal part of syntaxin-lA in artificial giant unilamellar vesicles resulted in segregation of PIP2 and syntaxin-1A into distinct domains even when cholesterol was absent. Our results demonstrate that electrostatic protein-lipid interactions can result in the formation of microdomains independently of cholesterol or lipid phases.%神经细胞中台勺"胞吐作用"需要SNARE'蛋白"突rn触融合蛋白.1A,该蛋白类聚在突触囊泡要进rn行"胞吐作用"的点上.ReInrlard Jahn及其同rn事利用超高分辨率"受激发射损耗"(STED)显rn微镜发现,突触融合蛋白通过与强阴离子性的rn"lipid Drlosphatidylirlositol-4,5-bisphospllate rn(PIP2)"发生静电相互作用,而在细胞膜中类rn聚成70纳米大小的微型区域.这些结果表明,rn静电性的蛋白一脂质相互作用可独立于胆固醇rn或脂质相而导致微型区域的形成,它们对于质rn膜的组织有重要意义.