INTERACTION OF INSULIN-RECEPTOR SUBSTRATE-2 (IRS-2) WITH THE INSULIN AND INSULIN-LIKE GROWTH-FACTOR-I RECEPTORS - EVIDENCE FOR 2 DISTINCT PHOSPHOTYROSINE-DEPENDENT INTERACTION DOMAINS WITHIN IRS-2

Insulin receptor substrate 2 (IRS-2) has recently been shown to be a s ubstrate of the insulin receptor (IR), In this study we utilize the ye ast two-hybrid system and assays of in vitro interaction to demonstrat e that IRS-2 interacts directly with the IR and the insulin-like growt h factor I receptor, We show that, like IRS-1, the region of IRS-2 tha t contains the putative phosphotyrosine binding and SAIN elements (188 -591) is sufficient for receptor interaction and that this interaction is dependent upon the NPX(p)Y (where (p)Y is phosphotyrosine) motifs within the juxtamembrane domains of the receptors, In addition to this amino-terminal NPX(p)Y-binding domain, an additional domain of strong interaction was identified in the central region of IRS-2 and was loc alized between amino acids 591 and 733, This interaction was found to be dependent upon receptor phosphorylation but was NPX(p)Y-independent , This region does not appear to have either an SH2 or a phosphotyrosi ne binding domain, Both of the interactions could also be demonstrated in vitro using IRS-2 glutathione S-transferase fusion proteins, We co nclude that IRS-2, unlike IRS-1, can interact with tyrosine phosphoryl ated receptors such as the IR and insulin-like growth factor I recepto r via multiple independent binding motifs, Our findings suggest the ex istence of a previously unidentified phosphotyrosine dependent binding domain within the central region of IRS-2.