P35568

IRS-1(Insulin receptor substrate 1) is one of the major substrates of the insulin receptor kinase. IRS-1 plays a crucial role in insulin signaling as a major substrate of the insulin receptor, being phosphorylated in response to insulin, insulin-like growth factor 1 (IGF-1), and interleukin 4 (IL-4) stimulation. Phosphorylation occurs on serine, threonine, and tyrosine residues across various tissues, with casein kinase II being a key serine/threonine kinase that mediates a significant portion of insulin-stimulated phosphorylation of IRS-1. Notably, threonine 502 has been identified as the primary phosphorylation site for casein kinase II in rat IRS-1, while serine 99 serves as an additional phosphorylation site. Phosphorylation of IRS-1 by casein kinase II is an integral part of the intracellular insulin signaling cascade, influencing metabolic responses to insulin.