RAT AND HUMAN PANCREATIC-ISLET CELLS CONTAIN A CALCIUM-ION INDEPENDENT PHOSPHOLIPASE-A(2) ACTIVITY SELECTIVE FOR HYDROLYSIS OF ARACHIDONATE WHICH IS STIMULATED BY ADENOSINE-TRIPHOSPHATE AND IS SPECIFICALLY LOCALIZED TO ISLET BETA-CELLS
RAT AND HUMAN PANCREATIC-ISLET CELLS CONTAIN A CALCIUM-ION INDEPENDENT PHOSPHOLIPASE-A(2) ACTIVITY SELECTIVE FOR HYDROLYSIS OF ARACHIDONATE WHICH IS STIMULATED BY ADENOSINE-TRIPHOSPHATE AND IS SPECIFICALLY LOCALIZED TO ISLET BETA-CELLS
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DOI：
10.1021/bi00052a041
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发表时间：
1993-01-12
期刊：
影响因子：
2.9
通讯作者：
TURK, J
中科院分区：
文献类型：
--
作者：
GROSS, RW;RAMANADHAM, S;TURK, J
最近的研究表明，心肌Ca 2+非依赖性磷脂酶A2作为一种受ATP调节的催化和调节多肽复合物存在，这表明了一种新的机制，通过该机制，糖酵解通量的改变可以与促进胰岛素分泌的类二十烷酸的产生相结合。为了确定这种机制的潜在相关性，我们研究了胰岛中磷脂酶A2活性的动力学特征、底物特异性和细胞位点。大鼠胰岛含有Ca 2 +-非依赖性磷脂酶A2活性，其在生理pH下是最佳的，优先水解在sn-1位含有乙烯基醚键的磷脂底物，并且与sn-2位的油酸相比优选花生四烯酸。大鼠胰岛Ca 2+非依赖性磷脂酶A2活性受到基于机制的抑制剂（E）-6-（溴亚甲基）-3-（1-萘基）-2H-四氢吡喃-2-酮的抑制，并受到ATP的刺激。通过荧光激活细胞分选从分散的胰岛细胞中纯化β细胞，证明β细胞（而不是非β细胞）含有Ca 2+非依赖性、ATP刺激的磷脂酶A2活性。值得注意的是，克隆RIN-m5 f胰岛素瘤细胞，它具有葡萄糖诱导的胰岛素分泌的缺陷，含有一个Ca 2+非依赖性磷脂酶A2，这是不受ATP浓度的改变。总的来说，这些结果和所附的论文[Ramanadham et al.（1993）Biochemistry（following paper in this issue）]暗示Ca 2 +-非依赖性磷脂酶A2是一种假定的葡萄糖传感器，它可以将糖酵解代谢的改变与生物活性类二十烷酸的产生偶联，从而促进葡萄糖诱导的胰岛素分泌。
The recent demonstration that myocardial Ca2+-independent phospholipase A2 exists as a complex of catalytic and regulatory polypeptides that is modulated by ATP has suggested a novel mechanism through which alterations in glycolytic flux can be coupled to the generation of eicosanoids which facilitate insulin secretion. To determine the potential relevance of this mechanism, we examined the kinetic characteristics, substrate specificities, and cellular locus of phospholipase A2 activity in pancreatic islets. Rat pancreatic islets contain a Ca2+-independent phospholipase A2 activity which is optimal at physiologic pH, preferentially hydrolyzes phospholipid substrates containing a vinyl ether linkage at the sn-1 position, and prefers arachidonic acid compared to oleic acid in the sn-2 position. Rat islet Ca2+-independent phospholipase A2 activity is inhibited by the mechanism-based inhibitor (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one and is stimulated by ATP. Purification of beta-cells from dispersed pancreatic islet cells by fluorescence-activated cell sorting demonstrated that beta-cells (but not non-beta-cells) contain Ca2+-independent, ATP-stimulated phospholipase A2 activity. Remarkably, clonal RIN-m5f insulinoma cells, which possess a defect in glucose-induced insulin secretion, contain a Ca2+-independent phospholipase A2 which is not modulated by alterations in ATP concentration. Collectively, these results and those of an accompanying paper [Ramanadham et al. (1993) Biochemistry (following paper in this issue)] implicate Ca2+-independent phospholipase A2 as a putative glucose sensor which can couple alterations in glycolytic metabolism to the generation of biologically active eicosanoids and thereby facilitate glucose-induced insulin secretion.