Regulation of cytosolic prostaglandin E synthase by phosphorylation
Regulation of cytosolic prostaglandin E synthase by phosphorylation
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DOI：
10.1042/bj20040118
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发表时间：
2004-07-01
影响因子：
4.1
通讯作者：
Kudo, I
中科院分区：
文献类型：
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作者：
Kobayashi, T;Nakatani, Y;Kudo, I
cPGES[胞质PG（前列腺素）E合成酶]在多种细胞中组成性表达，可调节COX（环加氧酶）-1依赖性即刻PGE(2)的生成。在本研究中，我们发现cPGES发生丝氨酸磷酸化，并在细胞激活后瞬间加速。一些证据表明，激活cpges的蛋白激酶是CK-II（酪蛋白激酶11）。在体外，重组cPGES被CK-II直接磷酸化并与CK-II相关，导致底物PGH的Km显著降低(2)。在活化的细胞中，cPGES磷酸化与cPGES酶活性和外源性和内源性花生四烯酸产生的PGE2的增加同时发生，这些过程由Hsp90（热休克蛋白90）促进，Hsp90是一种与cPGES和CK-II形成三级复合物的分子伴侣。用CK-II和Hsp90抑制剂以及显性阴性CK-II抑制剂处理细胞可减弱cPGES-CK-II-Hsp90复合物的形成以及随之而来的cPGES磷酸化和活化。cPGES上两个预测CK-II磷酸化位点（Ser（113）和Ser(118)）中的任何一个发生突变，都可以在体外和体内消除其磷酸化和激活。此外，p38丝裂原激活的蛋白激酶抑制剂SB20358或抗炎糖皮质激素地塞米松可改善ck - ii - hsp90介导的cPGES活化。总之，本研究的结果提供了第一个证据，证明这种二十烷类生物合成酶的细胞功能是由分子伴侣及其客户蛋白激酶控制的。
cPGES [cytosolic PG (prostaglandin) E synthase] is constitutively expressed in various cells and can regulate COX (cyclo-oxygenase)-1-dependent immediate PGE(2) generation. In the present study, we found that cPGES underwent serine phosphorylation, which was accelerated transiently after cell activation. Several lines of evidence suggest that a cPGES-activating protein kinase is CK-II (casein kinase 11). Recombinant cPGES was phosphorylated directly by and associated with CK-II in vitro, resulting in marked reduction of the Km for the substrate PGH(2). In activated cells, cPGES phosphorylation occurred in parallel with increased cPGES enzymic activity and PGE2 production from exogenous and endogenous arachidonic acid, and these processes were facilitated by Hsp90 (heat-shock protein 90), a molecular chaperone that formed a tertiary complex with cPGES and CK-II. Treatment of cells with inhibitors of CK-II and Hsp90 and with a dominant-negative CK-II attenuated the formation of the cPGES-CK-II-Hsp90 complex and attendant cPGES phosphorylation and activation. Mutations of either of two predicted CK-II phosphorylation sites on cPGES (Ser(113) and Ser(118)) abrogated its phosphorylation and activation both in vitro and in vivo. Moreover, the CK-II-Hsp90-mediated activation of cPGES was ameliorated by the p38 mitogen-activated protein kinase inhibitor SB20358 or by the anti-inflammatory glucocorticoid dexamethasone. Taken together, the results of the present study have provided the first evidence that the cellular function of this eicosanoid-biosynthetic enzyme is under the control of a molecular chaperone and its client protein kinase.