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MEMBRANE DOMAINS IN SECRETORY GRANUES OF RAT PAROTID ACINAR CELLS

大鼠腮腺腺泡细胞分泌颗粒的膜结构域

基本信息

批准号：
11671856
负责人：
YOKOYAMA Miki
金额：
$ 1.92万
依托单位：
NIHON UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Recent advances in membrane biology suggest the glycolipids- and cholesterol-rich membrane microdomains as lateral structural components of the plasma membranes. These microdomains are called as lipid rafts and have been proposed to function as platforms for both signal transduction and membrane trafficking. Rafts are considered to be formed by tight packing of long and mostly saturated acyl chains of glycolipids interspaced by cholesterol. The components of lipid rafts are biochemically separated as DRMs (detergent-resistant membranes) or DIGs (detergent-insoluble glycolipids-enriched domains) based on their insolubility in the detergent Triton X-100 in the cold. Because of their high lipid content, DRMs can be isolated in the low density fraction after gradient centrifugation. DRMs concentrate glycosyl-phosphatidylinositol-anchored proteins (GPI-anchored proteins), some transmembrane proteins including influenza hemagglutinin, and also intracellular signaling proteins such as dually acylated Src-PTKs Lck, Lyn and Fyn or heterotrimeric GTP-binding proteins and phosphatidylinositol bisphosphate. Rafts are therefore likely to act as scaffolding for both extracellular proteins and intracellular molecules. In the immune system, the requirement of lipid rafts for tyrosine phosphorylation mediated via high affinity Fc receptor for IgE (FceRI) and TCR has been reported. However, the requirement of lipid rafts for FcγR-mediated tyrosine phosphorylation has not been investigated.In the present study, we investigated the role of lipid rafts in FcγR-signaling in retinoic acid-differentiated HL60 cells (RA-HL60 cells). Our results suggest that lipid rafts are crucial machinery in which clustering of FCγRIIa induces the activation of Src-PTKs to initiate the tyrosine phosphorylation pathway. We have also tried to identify lipid raft in the secretory granules of rat parotid acinar cells.

膜生物学的最新进展表明，富含糖脂和胆固醇的膜微区是质膜的侧向结构成分。这些微结构域被称为脂筏，并已被提出作为信号转导和膜运输的平台。筏状物被认为是由胆固醇间隔的糖脂的长且大部分饱和的酰基链紧密堆积形成的。脂筏的组分在低温下不溶于洗涤剂Triton X-100，可通过生物化学方法分离为DRM（抗洗涤剂膜）或DIG（洗涤剂不溶性糖脂富集结构域）。由于它们的高脂质含量，DRMs可以在梯度离心后在低密度级分中分离。DRM浓缩糖基-磷脂酰肌醇锚定蛋白（GPI锚定蛋白）、一些跨膜蛋白（包括流感血凝素）以及细胞内信号传导蛋白（如双酰化Src-PTKs Lck、林恩和Fyn或异源三聚体GTP结合蛋白和磷脂酰肌醇二磷酸）。因此，筏可能作为细胞外蛋白质和细胞内分子的支架。在免疫系统中，已经报道了通过IgE的高亲和力Fc受体（FceRI）和TCR介导的酪氨酸磷酸化对脂筏的需求。本研究以视黄酸诱导分化的HL 60细胞（RA HL 60细胞）为研究对象，探讨了脂筏在Fcγ R信号转导中的作用。我们的研究结果表明，脂筏是重要的机制，其中聚集的FCγRIIa诱导Src-PTKs激活启动酪氨酸磷酸化途径。我们还试图确定大鼠腮腺腺泡细胞分泌颗粒中的脂筏。