Ubiquitin–proteasome degradation of serum-and glucocorticoid-regulated kinase-1 (SGK-1) is mediated by the chaperone-dependent E3 ligase CHIP

L Belova, S Sharma, DR Brickley… - Biochemical …, 2006 - portlandpress.com
L Belova, S Sharma, DR Brickley, JR Nicolarsen, C Patterson, SD Conzen
Biochemical Journal, 2006portlandpress.com
SGK-1 (serum-and glucocorticoid-regulated kinase-1) is a stress-induced serine/threonine
kinase that is phosphorylated and activated downstream of PI3K (phosphoinositide 3-
kinase). SGK-1 plays a critical role in insulin signalling, cation transport and cell survival.
SGK-1 mRNA expression is transiently induced following cellular stress, and SGK-1 protein
levels are tightly regulated by rapid proteasomal degradation. In the present study we report
that SGK-1 forms a complex with the stress-associated E3 ligase CHIP [C-terminus of H sc …
SGK-1 (serum- and glucocorticoid-regulated kinase-1) is a stress-induced serine/threonine kinase that is phosphorylated and activated downstream of PI3K (phosphoinositide 3-kinase). SGK-1 plays a critical role in insulin signalling, cation transport and cell survival. SGK-1 mRNA expression is transiently induced following cellular stress, and SGK-1 protein levels are tightly regulated by rapid proteasomal degradation. In the present study we report that SGK-1 forms a complex with the stress-associated E3 ligase CHIP [C-terminus of Hsc (heat-shock cognate protein) 70-interacting protein]; CHIP is required for both the ubiquitin modification and rapid proteasomal degradation of SGK-1. We also show that CHIP co-localizes with SGK-1 at or near the endoplasmic reticulum. CHIP-mediated regulation of SGK-1 steady-state levels alters SGK-1 kinase activity. These data suggest a model that integrates CHIP function with regulation of the PI3K/SGK-1 pathway in the stress response.
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