| Modification Notes |
Serum- and glucocorticoid-regulated kinase (SGK), a serine/threonine protein kinase, is transcriptionally regulated by serum, glucorticoids and mineralocorticoids. SGK regulates the control of extracellular fluid volume, blood pressure and sodium homeostasis and is also a component of the p38 MAPK-mediated response to hyperosmotic stress. SGK is a downstream target of phosphoinositide 3-kinase (PI 3-kinase)-stimulated growth factor signaling, and 3-phosphoinositide-dependent protein kinase 1 (PDK1) is capable of phosphorylating the activation-loop of SGK at Thr 256. Thr 256 and Ser 422 are the putative phosphorylation sites of SGK. Mutations at those putative phosphorylation sites inhibit SGK activation. For example, the Ser 422 to Ala mutant, lacking a PDK-2 phosphorylation site, is inactive and resistant to activation by Insulin. Thus, in addition to regulation at the level of gene expression, the enzymatic activity of SGK is regulated by multiple protein kinases, including PKA, PDK1, and PDK2. |