The activation of exocytotic sites by the formation of phosphatidylinositol 4,5-bisphosphate microdomains at syntaxin clusters
The activation of exocytotic sites by the formation of phosphatidylinositol 4,5-bisphosphate microdomains at syntaxin clusters
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DOI：
10.1074/jbc.m413307200
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发表时间：
2005-04-29
影响因子：
4.8
通讯作者：
Takahashi, M
中科院分区：
文献类型：
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作者：
Aoyagi, K;Sugaya, T;Takahashi, M
磷脂酰肌醇4，5-二磷酸（PI（4，5）P-2）是脂质双层的次要组分，但在各种细胞功能中起重要作用，包括胞吐和胞吞。最近，PI（4，5）P-2被证明在质膜中形成微区。在这项研究中，我们研究了PI（4，5）P-2微结构域的空间组织和细胞外吞机制之间的关系，在克隆大鼠嗜铬细胞瘤PC 12细胞。PI（4，5）P-2和突触融合蛋白，一种可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体蛋白的胞吐作用所必需的，表现出点状集群在分离的质膜。与突触融合蛋白簇和大致密核心囊泡（LDCV）共定位的PI（4，5）P-2微区的数量在儿茶酚胺释放后减少。或者，I型磷脂酰肌醇-4-磷酸5-激酶（PIP 5 KI）的表达增加了PI（4，5）P-2微结构域的数量与对接LDCV的突触融合蛋白簇和增强胞吐活性，可能是通过增加释放位点的数量。约有一半的PI（4，5）P-2微结构域不与脂筏特异性标记物Thy-1共定位，并且观察到转染的PIP 5 KI与突触融合蛋白簇共定位。这些结果表明，PI（4，5）P-2微结构域的形成与对接LDCV的突触融合蛋白集群是必不可少的钙依赖性胞吐。
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P-2) is a minor component of the lipid bilayer but plays an important role in various cellular functions, including exocytosis and endocytosis. Recently, PI(4,5)P-2 was shown to form microdomains in the plasma membrane. In this study, we investigated the relationship between the spatial organization of PI(4,5)P-2 microdomains and exocytotic machineries in clonal rat pheochromocytoma PC12 cells. Both PI(4,5)P-2 and syntaxin, a soluble N-ethylmaleimide-sensitive factor attachment protein receptor protein essential for exocytosis, exhibited punctate clusters in isolated plasma membranes. The number of PI(4,5)P-2 microdomains colocalizing with syntaxin clusters and large dense core vesicles (LDCVs) was decreased after catecholamine release. Alternatively, the expression of type I phosphatidylinositol-4-phosphate 5-kinase (PIP5KI) increased the number of PI(4,5)P-2 microdomains at syntaxin clusters with docked LDCVs and enhanced exocytotic activity, possibly by increasing the number of release sites. About half of the PI(4,5)P-2 microdomains were not colocalized with Thy-1, a specific marker of lipid rafts, and the colocalization of transfected PIP5KI with syntaxin clusters was observed. These results suggest that the formation of PI(4,5)P-2 microdomains at syntaxin clusters with docked LDCVs is essential for Ca2+-dependent exocytosis.