insulin receptor substrate-1
a cytoplasmic protein that is a direct substrate of the activated insulin receptor kinase. Insulin exposure results in its rapid phosphorylation at multiple tyrosine residues. Its phosphorylated sites associate with high affinity to certain cellular proteins. IRS-1 thus acts as an adaptor molecule that links the receptor kinase to various cellular activities regulated by insulin. IRS-1 is also phosphorylated after stimulation by insulinlike growth factor-1 and several interleukins.
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Examples: glitazone, GI cocktail, etc.