IndraLab

"IRS-1 is a novel direct substrate for IKK and that phosphorylation of IRS-1 at Ser(312) (and other sites) by IKK may contribute to the insulin resistance mediated by activation of inflammatory pathways."

"These results indicate that activation of protein kinase c stimulates a kinase which can phosphorylate insulin receptor substrate-1 at serine 612, resulting in an inhibition of insulin signaling in the cell these data suggest that: 1) activation of pkctheta contributes to ikk and jnk activation by ffas;2) ikk and jnk mediate pkctheta signals for irs-1 serine phosphorylation and degradation; ser-302 phosphorylation is dependent on pi 3-kinase/mtor, whereas ser-307 depends on c-jun nh2-terminal kinase to inhibit irs1 tyrosine phosphorylation. Ser-636 is located around the pi 3-kinase binding site and, therefore, thought to inhibit pi 3-kinase signaling."

"Nevertheless, s6k1-deficient mice remain sensitive to insulin owing to the apparent loss of a negative feedback loop from s6k1 to insulin receptor substrate 1 (irs1), which blunts s307 and s636/s639 phosphorylation; thus under conditions of nutrient satiation s6k1 negatively regulatesinsulin."

"Extensive studies have provided evidence that phosphorylation of Ser307 in IRS-1 inhibits IR/IRS-1 complex formation and IRS-1 tyrosine phosphorylation after prolonged insulin-stimulation similar to our results."

"Thus, at least three kinases mediate phosphorylation of ser307, including jnk, serine kinases in the pi 3-kinase cascade that are activated byinsulinor igf-1, and mek1-sensitive kinase cascades during tnf-alfa stimulation."

"Insulin also activates jnk, erk, pkc and mtor, which induce the phosphorylation of irs1 on serine residues 307, 612 and 632 and inhibit its functions. Our results indicate that the insulin-stimulated degradation of irs-1 via the phosphatidylinositol 3-kinase pathway is in part dependent upon the ser(312) phosphorylation of irs-1."

"Thus, at least three kinases mediate phosphorylation of ser307, including jnk, serine kinases in the pi 3-kinase cascade that are activated byinsulinor igf-1, and mek1-sensitive kinase cascades during tnf-alfa stimulation."

"Map kinases and mtor mediate insulin-induced phosphorylation ofinsulinreceptor substrate-1 on serine residues 307, 612 and 632"

"Insulin also activates jnk, erk, pkc and mtor, which induce the phosphorylation of irs1 on serine residues 307, 612 and 632 and inhibit its functions. Our results indicate that the insulin-stimulated degradation of irs-1 via the phosphatidylinositol 3-kinase pathway is in part dependent upon the ser(312) phosphorylation of irs-1."

"Mtor induced the serine phosphorylation of irs-1 (ser-636/639), and such phosphorylation was inhibited by rapamycin. These results suggest that tnf impairs insulin signaling through irs-1 by activation of a pi 3-kinase/akt/mtor pathway, which is antagonized by pten"