PANCREATIC ISLETS EXPRESS CA2+ INDEPENDENT PHOSPHOLIPASE A2 ENZYME

用葡萄糖刺激胰岛可导致 非酯化花生四烯酸的磷脂水解和积累 酸，如同位素稀释质谱仪所证明的。 胰岛表达一种不依赖钙离子的磷脂酶A2 对卤代烯醇抑制敏感的(CaI-PLA2)活性 内酯自杀底物(HELSS)，也可减弱葡萄糖诱导的 从胰岛磷脂和胰岛素中提取花生四烯酸 分泌物。从大鼠胰岛c DNA文库中克隆了一个c DNA。 编码一种氨基酸序列为751个氨基酸的蛋白质 这与最近从CHO中克隆的CaI-PLA2酶同源 细胞。人卵巢癌细胞系COS-7和中国仓鼠卵巢细胞系CHO的瞬时转染 克隆的胰岛CaI-PLA2基因使细胞数量增加 CaI-PLA2活性，该活性易受 HELSS。胰岛氨基酸残基中的CaI-PLA2结构域 150-414由8个重复的序列主题组成 大约33个氨基酸残基，这是高度 与与微管蛋白和整合体结合的锚蛋白结构域同源 膜蛋白，包括几种调节离子的蛋白质 跨膜的通量。这些发现补充了以前的 提示CaI-PLA2可能参与的药理观察 在调节葡萄糖刺激的b细胞跨膜离子通量方面。

Stimulation of pancreatic islets with glucose results in phospholipid hydrolysis and accumulation of non-esterified arachidonic acids, as demonstrated by isotope dilution mass spectrometry. Pancreatic islets express a Ca2+-independent phospholipase A2 (CaI-PLA2) activity which is sensitive to inhibition by a haloenol lactone suicide substrate (HELSS) that also attenuates glucose-induced hydrolysis of arachidonic acid from islet phospholipids and insulin secretion. A cDNA has been cloned from a rat islet cDNA library which encodes a protein with a deduced amino acid sequence of 751 residues that is homologous to a CaI-PLA2 enzyme recently cloned from CHO cells. Transient transfection of both COS-7 cells and CHO cells with the cloned islet CaI-PLA2 cDNA resulted in an increase in cellular CaI-PLA2 activity, and this activity was susceptible to inhibition by HELSS. The domain of the islet CaI-PLA2 from amino acid residues 150-414 is composed of 8 stretches of a repeating sequen ce motif of approximately 33 amino acid residues in length which is highly homologous to domains of ankyrin which bind both tubulin and integral membrane proteins, including several proteins which regulate ionic fluxes across membranes. These findings complement previous pharmacologic observations which suggest that CaI-PLA2 may participate in regulating trans-membrane ion flux in glucose-stimulated b-cells.