GRB10 INTERACTS DIFFERENTIALLY WITH THE INSULIN-RECEPTOR, INSULIN-LIKE-GROWTH-FACTOR I RECEPTOR, AND EPIDERMAL GROWTH-FACTOR RECEPTOR VIA THE GRB10 SRC-HOMOLOGY-2 (SH2) DOMAIN AND A 2ND NOVEL DOMAIN LOCATED BETWEEN THE PLECKSTRIN HOMOLOGY AND SH2 DOMAINS

The Grb10 protein appears to be an adapter protein of unknown function that has been implicated in insulin receptor (IR) signaling, The inte raction of this protein with the IR has been shown to be mediated in p art by the Src homology 2 (SH2) domain of Grb10, Here we demonstrate t he existence of a second novel domain within Grb10 that interacts with the TR and insulin-like growth factor receptor in a kinase-dependent manner, This do main was localized to a region of approximately 50 ami no acids, and we term it the BPS domain to denote its location between the PH and SH2 domains, The BPS domain does not bear any obvious rese mblance to other known protein interaction domains but is highly conse rved among the Grb10-related proteins Grb7 and Grb14, We show that the BPS domain interaction is dependent upon receptor tyrosine kinase act ivity, Furthermore, interaction of the BPS domain requires the kinase domain of the IR, since mutation of the paired tyrosine residues (Y115 0F/Y1151F) within the HC. activation loop dramatically reduced the int eraction, Last, our data suggest that the presence of two distinct pro tein interaction domains may help to determine the specificity by whic h Grb10 interacts with different receptors, Specifically, the IR, whic h appears to interact most strongly with Grb10, interacts well with bo th the SH2 and BPS domains, Conversely, the insulin-like growth factor receptor and EGFR, which interact less avidly with Grb10, interact we ll only with the BPS domain or the SH2 domain, respectively. In summar y, our findings demonstrate the existence of a previously unidentified tyrosine kinase activity-dependent binding domain located between the Pleckstrin homology and SH2 domains of Grb10.