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Updated: Jul 14, 2026

A High Resolution Method to Monitor Phosphorylation-dependent Activation of IRF3
Published on: January 24, 2016
Phosphorylation of Irs1 at SER-522 inhibits insulin signaling
Jodel Giraud1, Michael Haas, Edward P Feener
1Howard Hughes Medical Institute, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA.
Abstract:
Multisite phosphorylation of Irs1 on serine and threonine residues regulates insulin signaling that can contribute to insulin resistance. We identified by mass spectrometry the phosphorylation of Ser522 in rat Irs1 (S522(Irs1)). The functional effects of this phosphorylation site were investigated in cultured cells using a sequence-specific phosphoserine antibody. Insulin stimulated the phosphorylation of S522(Irs1) in L6 myoblasts and myotubes. S522(Irs1) phosphorylation was inhibited by wortmannin, whereas PD98059, rapamycin, or glucose-starvation had no effect. Reducing Akt expression with small interfering RNA inhibited insulin-stimulated phosphorylation of S522(Irs1), suggesting the involvement of the phosphatidylinositol 3-kinase--> Akt cascade. A S522(Irs1)-->A522(Irs1) substitution increased insulin-stimulated tyrosine phosphorylation of Irs1 and signaling, whereas a S522(Irs1)-->E522(Irs1) substitution reduced insulin-stimulated Irs1 tyrosine phosphorylation. Together, these results suggest the phosphatidylinositol 3-kinase-->Akt cascade can inhibit insulin signaling through the phosphorylation of S522(Irs1).
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