Hypotonic cell swelling induces translocation of the α isoform of cytosolic phospholipase A2 but not the γ isoform in Ehrlich ascites tumor cells
Hypotonic cell swelling induces translocation of the α isoform of cytosolic phospholipase A2 but not the γ isoform in Ehrlich ascites tumor cells
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DOI：
10.1046/j.1432-1327.2000.01615.x
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发表时间：
2000-09-01
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影响因子：
--
通讯作者：
Hoffmann, EK
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文献类型：
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作者：
Pedersen, S;Lambert, IH;Hoffmann, EK
我们证明了在埃利希腹水肿瘤细胞中存在两种胞浆型磷脂酶A（2），cPLA（2）α和cPLA（2）γ。这两种酶几乎均匀分布在整个细胞在控制条件下，通过激光扫描共聚焦显微镜可视化。通过低渗细胞肿胀或添加Ca 2+离子载体A23187的刺激导致cPLA（2）α（而不是cPLA（2）γ）易位到细胞核，在那里它形成热点样簇。我们的小组先前表明，掺入埃利希细胞磷脂中的放射性标记的花生四烯酸的释放在低渗细胞肿胀时立即且短暂地增加[Thoroed，S.M.，劳里岑湖兰伯特，I.H.，汉森，H.S. & Hoffmann，E.K.（1997）J. 160，47-58]。我们现在证明，花生四烯酸是从核馏分释放低渗暴露。用A23187刺激埃利希细胞也导致从细胞核释放花生四烯酸的增加。然而，由于低渗细胞肿胀并不伴随着细胞内游离胞质Ca 2+浓度（[Ca 2 +]（i））的任何可检测的增加，因此刺激诱导的cPLA（2）α易位也可以在[Ca 2 +]（i）不升高的情况下发生。刺激诱导的cPLA（2）α易位似乎不能通过抑制促分裂原活化蛋白（MAP）激酶激活、p38 MAP激酶、酪氨酸激酶和蛋白激酶C来阻止，因此磷酸化对刺激诱导的cPLA（2）α易位并不重要。F-肌动蛋白的破坏并不影响易位过程，因此，完整的F-肌动蛋白细胞骨架似乎并不需要cPLA（2）α的易位。
We demonstrate that two isoforms of the cytosolic phospholipase A(2), cPLA(2)alpha and cPLA(2)gamma, are present in Ehrlich ascites tumor cells. Both enzymes are almost uniformly distributed throughout the cells under control conditions, as visualized by laser-scanning confocal microscopy. Stimulation by either hypotonic cell swelling or addition of the Ca2+ ionophore A23187 results in translocation of cPLA(2)alpha, but not cPLA(2)gamma, to the nucleus, where it forms hot-spot-like clusters. Our group previously showed that release of radioactively labeled arachidonic acid, incorporated into the phospholipids of Ehrlich cells, was immediately and transiently increased on hypotonic cell swelling [Thoroed, S.M., Lauritzen, L., Lambert, I.H., Hansen, H.S. & Hoffmann, E.K. (1997) J. Membr. Biol. 160, 47-58]. We now demonstrate that arachidonic acid is released from the nuclear fraction following hypotonic exposure. Stimulation of Ehrlich cells with A23187 also leads to an increase in arachidonic acid release from the nucleus. However, as hypotonic cell swelling is not accompanied by any detectable increase in intracellular concentration of free cytosolic Ca2+ ([Ca2+](i)), stimulus-induced translocation of cPLA(2)alpha can also occur without elevation of [Ca2+](i). The stimulus-induced translocation of cPLA(2)alpha appears not to be prevented by inhibition of mitogen-activated protein (MAP) kinase activation, p38 MAP kinase, tyrosine kinases and protein kinase C, hence, phosphorylation is not crucial for the stimulus-induced translocation of cPLA(2)alpha. Disruption of F-actin did not affect the translocation process, thus, an intact F-actin cytoskeleton does not seem to be required for translocation of cPLA(2)alpha.