Group VIBCa2+-independent phospholipase A2γ promotes cellular membrane hydrolysis and prostaglandin production in a manner distinct from other intracellular phospholipases A2
Group VIBCa2+-independent phospholipase A2γ promotes cellular membrane hydrolysis and prostaglandin production in a manner distinct from other intracellular phospholipases A2
复制标题
DOI：
10.1074/jbc.m413766200
复制
发表时间：
2005-04-08
影响因子：
4.8
通讯作者：
Kudo, I
中科院分区：
文献类型：
--
作者：
Murakami, M;Masuda, S;Kudo, I
尽管通过钙非依赖性磷脂酶A(2)β(iPLA2β)参与了多种细胞事件，但其他iPLA2(2)同工酶的功能在很大程度上仍不清楚。在这项研究中，我们检测了VIB组iPLA2(2)伽马的细胞功能。慢病毒导入HEK293细胞后，细胞自发的、刺激偶联的和细胞死亡相关的花生四烯酸(AA)释放显著增加，花生四烯酸以环氧合酶(COX)-1偶联的方式转化为前列腺素E-2。反之，iPLA(2)小干扰RNA处理HEK293细胞后，AA释放明显减少，提示内源性iPLA(2)Gamma参与了这一过程。Ipla(2)γ蛋白因细胞类型不同而呈现多种大小，63 kDa的形式主要定位于过氧化体中。细胞磷脂的电喷雾电离质谱分析表明，iPLA2(2)-γ和其他细胞内的PLA2(2)酶作用于不同的磷脂亚类。同时通过COX-1和COX-2将iPLA2-γ基因导入Hca-7细胞，促进AA的释放和前列腺素E-2的合成，细胞生长也随之增加。人结直肠癌组织免疫组织化学结果显示，腺癌细胞中iPLA2-γ的表达升高。这些结果共同提示了iPLA2β和iPLA2(2)伽马在细胞内稳态和信号传递中的不同作用，过氧体AA释放和二十烷类化合物生成之间的功能联系，以及iPLA2伽马在肿瘤发生中的潜在贡献。
Although group VIA Ca2+-independent phospholipase A(2)beta (iPLA(2)beta) has been implicated in various cellular events, the functions of other iPLA(2) isozymes remain largely elusive. In this study, we examined the cellular functions of group VIB iPLA(2)gamma. Lentiviral transfection of iPLA(2)gamma into HEK293 cells resulted in marked increases in spontaneous, stimulus-coupled, and cell death-associated release of arachidonic acid ( AA), which was converted to prostaglandin E-2 with preferred cyclooxygenase (COX)-1 coupling. Conversely, treatment of HEK293 cells with iPLA(2)gamma small interfering RNA significantly reduced AA release, indicating the participation of endogenous iPLA(2)gamma. iPLA(2)gamma protein appeared in multiple sizes according to cell types, and a 63-kDa form was localized mainly in peroxisomes. Electrospray ionization mass spectrometry of cellular phospholipids revealed that iPLA(2)gamma and other intracellular PLA(2) enzymes acted on different phospholipid subclasses. Transfection of iPLA(2)gamma into HCA-7 cells also led to increased AA release and prostaglandin E-2 synthesis via both COX-1 and COX-2, with a concomitant increase in cell growth. Immunohistochemistry of human colorectal cancer tissues showed elevated expression of iPLA(2)gamma in adenocarcinoma cells. These results collectively suggest distinct roles for iPLA(2 beta) and iPLA(2)gamma in cellular homeostasis and signaling, a functional link between peroxisomal AA release and eicosanoid generation, and a potential contribution of iPLA(2)gamma to tumorigenesis.