Rabbit Anti-Human IRS1 monoclonal antibody for IHC-P, WB. Insulin Receptor Substrate-1. The main function of IRS1 is to enhance growth hormone-induced proliferative signaling. The activated insulin receptor phosphorylates IRS proteins on multiple tyrosine residues that serve as docking sites for downstream mediators of metabolic actions such as phosphatidylinositol-3 kinase. IRS proteins also undergo serine phosphorylation, which regulates its function. Phosphorylation of human IRS-1 at serines, such as 312 and 616 (serines 307 and 612 in mouse), results in the impairment of metabolic insulin signaling pathways.