UNBIASED PHOSPHOPROTEOMICS ANALYSIS UNVEILS MODULATION OF INSULIN SIGNALING BY EXTRAMITOTIC CDK1 KINASE ACTIVITY IN HUMAN MYOTUBES

Abstract

Isolated myoblasts from a multi-ethnic cohort of lean South Asians, lean Chinese, and obese Chinese (N=10 each) were terminally differentiated and stimulated with a low dose of insulin (10nM at 0, 5 and 30 min). Cell lysates were analyzed using unbiased proteomics and phosphoproteomics approach. Results showed recapitulation of the canonical PI3K-AKT insulin signaling pathway. Other enriched pathways include the apoptotic pathway, mRNA splicing pathway and Rho GTPase signaling pathway. Similarly, ethnicity and obesity specific phosphorylation changes were also observed both within and outside the insulin signaling pathway. Moreover, a novel joint kinase-substrate statistical analysis identified CDK1 and PAK1 as novel hub kinases. Further work on CDK1 revealed that CDK1 inhibition reduced glucose uptake and desensitized the mTORC1-S6K1 signaling downstream of the PI3K-AKT pathway. The result of this study also provides a rich resource for future studies on the mechanistic role of different kinases in insulin resistance development.