IRS4 (Insulin receptor substrate 4) is a cytoplasmic protein that contains many potential tyrosine and serine/threonine phosphorylation sites. Tyrosine-phosphorylated IRS4 protein has been shown to associate with cytoplasmic signaling molecules that contain SH2 domains. The IRS4 protein is phosphorylated by the insulin receptor tyrosine kinase upon receptor stimulation.
