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Kinase-active IGF1R phosphorylates IRS1 on tyrosine. 5 / 5
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"Insulin and IGF-I initiate the biological effects in target cells by binding to and activating its endogenous tyrosine kinase receptors [23,24]. These receptors are believed to transduce signals by phosphorylation on tyrosine residues of several cellular substrates including IRS proteins (IRS-1,-2,- 3 and –4) [25-28]."

"Accordingly, under the cellular context of the elevated expression of IL- 6Ra on myeloma cells, it is assumed that IL-6Ra molecules are located close to IGF-I receptors at lipid rafts, and IL-6 stimulation triggers the complex formation of IL-6Ra not only with gp130 but also with IGF-I receptors, leading to autophosphorylation of IGF-I receptor b and subsequent acti- vation of PI-3 kinase-Akt pathways (Fig. 4) 79 ."

"upon binding of IGF1, the IGFR, which is a receptor tyrosine kinase, becomes phosphorylated and recruits the substrate IRS1, leading to the activation of the lipid kinase PI3K"

"At least nine intracellular substrates of the insulin/IGF-I receptor kinases have been identified (Fig. 2). Four of these belong to the family of insulin-receptor substrate (IRS) proteins9. Other substrates include Gab-1, p60dok, Cbl, APS and isoforms of Shc10."

"from http://www.ub.rug.nl/eldoc/dis/medicine/n.wilczak/c1.pdf The intrinsic tyrosine kinase activity of the IGF-I receptor is enhanced and phosphorylates multiple substrates, including IRS1 and IRS2 on tyrosine residues"