May mediate the control of various cellular processes by insulin. When phosphorylated by the insulin receptor binds specifically to various cellular proteins containing SH2 domains such as phosphatidylinositol 3-kinase p85 subunit or GRB2. Activates phosphatidylinositol 3-kinase when bound to the regulatory p85 subunit. Interacts with SOCS7 (By similarity). Interacts (via IRS-type PTB domain) with IGF1R and INSR (via the tyrosine-phosphorylated NPXY motif) (By similarity). Interacts with UBTF, FER and PIK3CA (By similarity). Interacts (via phosphorylated YXXM motifs) with PIK3R1 (PubMed:1380456). Interacts with ROCK1 (PubMed:11739394). Interacts (via PH domain) with PHIP (PubMed:11018022). Interacts with GRB2 (PubMed:8491186). Interacts with ALK (By similarity). Interacts with EIF2AK2/PKR (By similarity). Interacts with GKAP1 (PubMed:25586176). Interacts with DGKZ in the absence of insulin; insulin stimulation decreases this interaction (PubMed:27739494). Found in a ternary complex with DGKZ and PIP5K1A in the absence of insulin stimulation (By similarity). Serine phosphorylation of IRS1 is a mechanism for insulin resistance. Ser-307 phosphorylation inhibits insulin action through disruption of IRS1 interaction with the insulin receptor, and Ser-789 phosphorylation is increased in the liver of insulin-resistant rats (PubMed:11606564, PubMed:12006586, PubMed:7504175). Phosphorylation of Tyr-895 is required for GRB2-binding. Phosphorylated by ALK. Phosphorylated at Ser-265, Ser-302, Ser-632 and Ser-1100 by RPS6KB1; phosphorylation induces accelerated degradation of IRS1 (By similarity). Phosphorylated on tyrosine residues in response to insulin (By similarity). In skeletal muscles, dephosphorylated on Tyr-608 by TNS2 under anabolic conditions; dephosphorylation results in the proteasomal degradation of IRS1 (By similarity). Ubiquitinated by the Cul7-RING(FBXW8) complex in a mTOR-dependent manner, leading to its degradation: the Cul7-RING(FBXW8) complex recognizes and binds IRS1 previously phosphorylated by S6 kinase (RPS6KB1 or RPS6KB2).