Regulation of cytosolic prostaglandin E synthase by phosphorylation.
cPGES [cytosolic PG (prostaglandin) E synthase] is constitutively expressed in various cells and can regulate COX (cyclo-oxygenase)-1-dependent immediate PGE2 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 II). Recombinant cPGES was phosphorylated directly by and associated with CK-II in vitro, resulting in marked reduction of the K m for the substrate PGH2. 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 (Ser113 and Ser118) 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.
Kobayashi
Tsuyoshi
T
Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Nakatani
Yoshihito
Y
Tanioka
Toshihiro
T
Tsujimoto
Masafumi
M
Nakajo
Shigeo
S
Nakaya
Kazuyasu
K
Murakami
Makoto
M
Kudo
Ichiro
I
D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D005938:Glucocorticoids / Q000494:pharmacology; D018841:HSP90 Heat-Shock Proteins / Q000502:physiology; D019746:Intramolecular Oxidoreductases / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D046911:Macromolecular Substances; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000502:physiology; D010766:Phosphorylation; D017354:Point Mutation / Q000502:physiology; D000071876:Prostaglandin-E Synthases; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D051381:Rats; D012694:Serine / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D005938:Glucocorticoids; D018841:HSP90 Heat-Shock Proteins; D046911:Macromolecular Substances; D012694:Serine; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases