MEMBRANE SIGNALING IN BETA CELLS AND VASCULAR WALL CELLS

分离的胰岛表达ATP刺激的，Ca2 +- 独立的（ASCI）磷脂酶A2（PLA2）酶，我们假设， ASCI-PLA2参与葡萄糖诱导胰岛素的早期事件 通过促进Ca2+进入β细胞分泌， 未酯化的花生四烯酸 用卤烯醇抑制ASCI-PLA2 内酯硅化物底物抑制葡萄糖诱导的β- 细胞胞浆Ca~（2+），这种作用被外源性 花生四烯酸 我们假设ASCI-PLA2参与了 Ca2+内流，这一过程在β-细胞和胰岛细胞中均有描述。 血管壁，并参与调节胰岛素分泌 和控制血管肌细胞增殖。 ASCI-PLA2表达 在血管肌细胞和内皮细胞，我们假设， 活动不受高血糖的调节，并参与调节 扩散。 因此，目的1是表征ASCI的作用- 磷脂酶A_2在β细胞容性Ca~（2+）内流中的作用及对细胞内Ca~（2+）的调节 胞浆Ca~（2+）和胰岛素分泌，目的2是表征 ASCI-PLA2在容性Ca2+进入血管肌细胞中的作用， 内皮细胞和增殖的调节。 小岛也 表达Ca2+依赖性14kDa分泌型PLA2（sPLA2）酶， 在用胰岛素促分泌素刺激时从β细胞分泌。 其他细胞的先例使我们假设sPLA2参与了 在胞吐作用的最后共同途径中， 以促进与分泌颗粒的融合。 的一些影响 sPLA2是由180 kDa膜受体介导的，该受体由 胰岛和血管肌细胞，并影响肌细胞 增殖 因此，目的3是表征sPLA 2在以下中的作用： β细胞和血管肌细胞胞吐作用的远端事件 增殖 我们发现胰岛分泌颗粒和 质膜由甘油醛-3-磷酸的同种型催化 脱氢酶（GAPDH），其特异性识别富含 已知在胰岛血浆中表达的血浆乙醇胺种类 膜和分泌颗粒。 葡萄糖诱导的一个关键信号 已知胰岛素分泌在GAPDH水平上产生，我们 假设这个信号涉及到融合催化的激活， GADH亚型。 目的4是表征GAPDH同种型在以下中的作用： 催化β细胞质膜和分泌颗粒的融合。

Isolated pancreatic islets express an ATP-stimulated,Ca2+- independent(ASCI)phospholipase A2(PLA2) enzyme, and we postulate that ASCI-PLA2 participates in early events in glucose-induced insulin secretion by facilitating Ca2+ entry into beta-cells via generation of nonesterified arachidonic acid. Inhibition of ASCI-PLA2 with a haloenol lactone suicide substrate suppresses the glucose-induced rise in beta- cell cytosolic Ca2+, and the effect is reversed by exogenous arachidonate. We postulate that ASCI-PLA2 participates in capacitative Ca2+ entry, a process described both in beta-cells and in cells of the vascular wall and which is involved in regulation of insulin secretion and in governing vascular myocyte proliferation. ASCI-PLA2 is expressed in vascular myocytes and endothelial cells, and we postulate that activity is unregulated by hyperglycemia and participates in regulation of proliferation. Aim 1 is therefore to characterize the role of ASCI- PLA2 in capacitative Ca2+ entry into beta-cells and the regulation of cytosolic Ca2+ and insulin secretion, and Aim 2 is to characterize the role of ASCI-PLA2 in capacitative Ca2+ entry into vascular myocytes and endothelial cells and the regulation of proliferation. Islets also express Ca2+-dependent 14kDa secretory PLA2(sPLA2)enzymes that are secreted from beta-cells upon stimulation with insulin secretagogues. Precedents with other cells cause us to postulate that sPLA2 participates in the final common pathway of exocytosis by modifying plasma membranes so as to facilitate fusion with secretory granules. Some effects of sPLA2 are mediated by 180 kDa membrane receptors, which are expressed by islets and by vascular myocytes and which influence myocyte proliferation. Aim 3 is therefore to characterize the role of sPLA2 in distal events in exocytosis in beta-cells and in vascular myocyte proliferation. We have found that fusion of islet secretory granules and plasma membranes is catalyzed by an isoform of glyceraldehyde-3-phosphate dehydrogenase(GAPDH), which specifically recognizes membranes rich in plasmenylethanolamine species known to be expressed in islet plasma membranes and secretory granules. A critical signal in glucose-induced insulin secretion is known to arise at the level of GAPDH, and we postulate that this signal involves activation of the fusion-catalyzing GAPDH isoform. Aim 4 is to characterize the role of GAPDH isoforms in catalyzing fusion of beta-cell plasma membranes and secretory granules.