Increased intracellular calcium activates serum and glucocorticoid-inducible kinase 1 (SGK1) through a calmodulin-calcium calmodulin dependent kinase kinase pathway in Chinese hamster ovary cells.
SGK1 is one of the protein-serine/threonine kinases that is activated by insulin in a PI3K-dependent manner. Although SGK1 mediates a variety of biological activities, the mechanisms regulating its activity remain unclear. In this study, we examined the potential roles of calcium signaling in the activation of SGK1. Treatment of CHO-IR cells with a cell-permeable calcium chelator, BAPTA-AM, abolished the insulin-induced activation of SGK1. Increasing intracellular calcium concentration by treating cells with thapsigargin or ionomycin induced a 6-8 fold increase in SGK1 activation. This was not affected by a PI3K inhibitor, wortmannin, but was completely inhibited by the calmodulin inhibitors, W 7 and W 5. Co-transfection of CHO cells with FLAG-SGK1 and CaMKK revealed the direct association of CaMKK with SGK1. These results suggest a calcium-triggered signaling cascade in which an increase in intracellular calcium concentration directly stimulates SGK1 through CaMKK.
Imai
Seiji
S
First Department of Internal Medicine, Nagoya City University Medical School, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan. imasei@med.nagoya-cu.ac.jp
Okayama
Naotsuka
N
Shimizu
Manabu
M
Itoh
Makoto
M
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D000252:Calcium-Transporting ATPases / Q000187:drug effects / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D006224:Cricetinae; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017874:Immediate-Early Proteins; D007328:Insulin / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D009687:Nuclear Proteins; D053499:Plasma Membrane Calcium-Transporting ATPases; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection; D000077191:Wortmannin; D000099184:Serum-Glucocorticoid Regulated Kinases
D000730:Androstadienes; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D000252:Calcium-Transporting ATPases; D002614:Chelating Agents; D004533:Egtazic Acid; D004791:Enzyme Inhibitors; D017874:Immediate-Early Proteins; D007328:Insulin; D015759:Ionomycin; D009687:Nuclear Proteins; D053499:Plasma Membrane Calcium-Transporting ATPases; D017346:Protein Serine-Threonine Kinases; D013449:Sulfonamides; D019284:Thapsigargin; D000077191:Wortmannin; D000099184:Serum-Glucocorticoid Regulated Kinases; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; C017967:W 7; C517695:CAMKK1 protein, human; C507517:ATP2B4 protein, human