Molecular mechanisms of altered membrane microdomain sensitivity leading to initiation of the arachidonic acid metabolism

膜微区敏感性改变导致花生四烯酸代谢启动的分子机制

基本信息

批准号：
13680791
负责人：
MURAKAMI Makoto
金额：
$ 2.37万
依托单位：
Showa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

In this study, we have investigated the molecular mechanisms of the perturbation of cellular membrane microdomains leading to the initiation of arachidonic acid (AA) release by various mammalian secretory phospholipase A2(sPLA2) enzymes. We have subdivided sPLA2s into three classes in terms of their different membrane microdomain sensisivities: (i) the sPLA2-IIA type, which acts on elicited membranes in activated cells;(ii) the sPLA2-X type, which acts on unmodified membranes in quiescent cells;and (iii) the sPLA-V type, which displays both the sPLA2-IIA and sPLA2-X type properties. sPLA2-IIA and related enzymes (IID and IIE) bind to the heparan sulfate proteoglycan (HSPG) glypican that is enriched in the rafts/caveolae,and are internalized into the perinuclear membtane compartments where they exhibit the AA-releasing function(the HSPG-shuttling pathway). sPLA2-X is unable to utilize the HSPG-shuttling pathway because of its inability to bind HSPG,yet it has a high affinity for phosphatidylcholine(PC) and can act on the PC-rich outer leaflet of the plasma membrane (the external plasma membrane (EPM) pathway). sPLA2-V has high affinity for both HSPG and PC, thereby being able to utilize both pathways, Although sPLA2-IIF weakly elicits the EPM pathway-based AA release, its function is greatly faciliated in activated cells, where this enzyme may interacts with the perturbed plasma membrame microdomain through its unique C-terminal extension. sPLA2III,which is composed of the central sPLA2 domain flanked with unique C-terminal domains, is capable of utilizing the EPM pathway. In addition, the highly cationic N-and C-terminal domains allow sPLA2-III to bind anionic HSPG and thus to enter the HSPG-shuttiling route. Collectively, our present analyses have revealed that the cellular actions of various sPLA2 enzymes are crucially affected by their anzymatic properties and subcellular localization, the latter of which is tightly linked with the dymanics of cellular membranes.

在这项研究中，我们研究了细胞膜微区扰动导致各种哺乳动物分泌型磷脂酶 A2 (sPLA2) 启动花生四烯酸 (AA) 释放的分子机制。我们根据不同的膜微区敏感性将 sPLA2 细分为三类：(i) sPLA2-IIA 型，作用于激活细胞中的诱发膜；(ii) sPLA2-X 型，作用于静止细胞中未修饰的膜。细胞；(iii) sPLA-V 类型，显示 sPLA2-IIA 和 sPLA2-X 类型特性。 sPLA2-IIA 和相关酶（IID 和 IIE）与筏/小窝中富集的硫酸乙酰肝素蛋白聚糖 (HSPG) 磷脂酰肌醇结合，并内化到核周膜区室中，在那里它们表现出 AA 释放功能（HSPG-穿梭路径）。 sPLA2-X由于无法结合HSPG而无法利用HSPG穿梭途径，但它对磷脂酰胆碱（PC）具有高亲和力，可以作用于富含PC的质膜外叶（外部质膜）（EPM）途径）。 sPLA2-V 对 HSPG 和 PC 都具有高亲和力，因此能够利用这两种途径，尽管 sPLA2-IIF 微弱地引发基于 EPM 途径的 AA 释放，但其功能在活化细胞中得到极大促进，在活化细胞中，该酶可能与通过其独特的 C 端延伸扰动质膜微区。 sPLA2III 由中央 sPLA2 结构域和两侧独特的 C 端结构域组成，能够利用 EPM 途径。此外，高度阳离子的 N 端和 C 端结构域允许 sPLA2-III 结合阴离子 HSPG，从而进入 HSPG 穿梭途径。总的来说，我们目前的分析表明，各种 sPLA2 酶的细胞作用很大程度上受到其酶特性和亚细胞定位的影响，后者与细胞膜的动力学密切相关。