Tyrosine phosphorylation of phosphoinositide-dependent kinase 1 by the insulin receptor is necessary for insulin metabolic signaling.
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Fiory F, Alberobello AT, Miele C, Oriente F, Esposito I, Corbo V, Ruvo M, Tizzano B, Rasmussen TE, Gammeltoft S, Formisano P, Beguinot F
Tyrosine phosphorylation of phosphoinositide-dependent kinase 1 by the insulin receptor is necessary for insulin metabolic signaling.
Mol Cell Biol. 2005 Dec;25(24):10803-14.
- PubMed ID
- 16314505 [ View in PubMed]
- Abstract
In L6 myoblasts, insulin receptors with deletion of the C-terminal 43 amino acids (IR(Delta43)) exhibited normal autophosphorylation and IRS-1/2 tyrosine phosphorylation. The L6 cells expressing IR(Delta43) (L6(IRDelta43)) also showed no insulin effect on glucose uptake and glycogen synthase, accompanied by a >80% decrease in insulin induction of 3-phosphoinositide-dependent protein kinase 1 (PDK-1) activity and tyrosine phosphorylation and of protein kinase B (PKB) phosphorylation at Thr(308). Insulin induced the phosphatidylinositol 3 kinase-dependent coprecipitation of PDK-1 with wild-type IR (IR(WT)), but not IR(Delta43). Based on overlay blotting, PDK-1 directly bound IR(WT), but not IR(Delta43). Insulin-activated IR(WT), and not IR(Delta43), phosphorylated PDK-1 at tyrosines 9, 373, and 376. The IR C-terminal 43-amino-acid peptide (C-terminal peptide) inhibited in vitro PDK-1 tyrosine phosphorylation by the IR. Tyr-->Phe substitution prevented this inhibitory action. In the L6(hIR) cells, the C-terminal peptide coprecipitated with PDK-1 in an insulin-stimulated fashion. This peptide simultaneously impaired the insulin effect on PDK-1 coprecipitation with IR(WT), on PDK-1 tyrosine phosphorylation, on PKB phosphorylation at Thr(308), and on glucose uptake. Upon insulin exposure, PDK-1 membrane persistence was significantly reduced in L6(IRDelta43) compared to control cells. In L6 cells expressing IR(WT), the C-terminal peptide also impaired insulin-dependent PDK-1 membrane persistence. Thus, PDK-1 directly binds to the insulin receptor, followed by PDK-1 activation and insulin metabolic effects.