Effects of phosphoinositide 3-kinase on the endothelin-1-induced activation of voltage-independent Ca(2+) channels and mitogenesis in Chinese hamster ovary cells stably expressing endothelin(a) receptor.
We recently demonstrated that endothelin-1 (ET-1) activates two types of Ca(2+)-permeable nonselective cation channel (designated NSCC-1 and NSCC-2) and a store-operated Ca(2+) channel (SOCC) in Chinese hamster ovary cells expressing endothelin(A) receptor (CHO-ET(A)R). In addition, these channels can be discriminated using Ca(2+) channel blockers (R,S)-(3,4-dihydro-6,7-dimethoxy-isochinolin-1-yl)-2-phenyl-N,N-di[2-(2,3,4-trimethoxyphenyl)ethyl]acetamid mesylate (LOE 908) and 1-(beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl)-1H-imidazole (SK&F 96365). LOE 908 is a blocker of NSCC-1 and NSCC-2, whereas SK&F 96365 is a blocker of SOCC and NSCC-2. In this study, we investigated the effects of phosphoinositide 3-kinase (PI3K) on the ET-1-induced activation of these channels and mitogenesis in CHO-ET(A)R using wortmannin and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY 294002), inhibitors of phosphoinositide 3-kinase (PI3K). ET-1-induced Ca(2+) influx was partially inhibited in CHO-ET(A)R pretreated with wortmannin or LY 294002. In contrast, addition of wortmannin or LY 294002 after stimulation with ET-1 did not suppress Ca(2+) influx. The Ca(2+) channels activated by ET-1 in wortmannin or LY 294002-treated CHO-ET(A)R were sensitive to LOE 908 and resistant to SK&F 96365. Wortmannin also partially inhibited ET-1-induced mitogenesis. LOE 908, but not SK&F 96365, abolished the wortmannin-resistant part of mitogenesis. The IC(50) values (~30 nM) of wortmannin for the ET-1-induced Ca(2+) influx and mitogenesis were similar to those for the ET-1-induced PI3K activation. In conclusion, NSCC-2 and SOCC are stimulated by ET-1 via PI3K-dependent cascade, whereas NSCC-1 is stimulated via PI3K-independent cascade. Moreover, PI3K seems to be required for the activation of the Ca(2+) entry, but not for its maintenance. In addition, PI3K is involved in the ET-1-induced mitogenesis that depends on the extracellular Ca(2+) influx through SOCC and NSCC-2.
Department of Neurosurgery, Kyoto University Faculty of Medicine, Kyoto, Japan. ykawanabe@rics.bwh.harvard.edu
Yoshifumi
Y
Kawanabe
Nobuo
N
Hashimoto
Tomoh
T
Masaki
D000081:Acetamides / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D006224:Cricetinae; D004347:Drug Interactions; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000096:biosynthesis*; D014162:Transfection; D000077191:Wortmannin
D000081:Acetamides; D000730:Androstadienes; D015220:Calcium Channels; D002867:Chromones; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007546:Isoquinolines; D009025:Morpholines; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; C081356:LOE 908; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium; D000077191:Wortmannin