Phosphotyrosine-Dependent Interaction of SHC and Insulin Receptor Substrate 1 with the NPEY Motif of the Insulin Receptor via a Novel Non-SH2 Domain

The SHC proteins have been implicated in insulin receptor (IR) signaling. In this study, we used the sensitive two-hybrid assay of protein-protein interaction to demonstrate that SHC interacts directly with the IR. The interaction is mediated by SHC amino acids 1 to 238 and is therefore independent of the Src homology 2 domain. The interaction is dependent upon IR autophosphorylation, since the interaction is eliminated by mutation of the IR ATP-binding site. In addition, mutational analysis of the Asn-Pro-Glu-Tyr (NPEY) motif within the juxtamembrane domain of the IR showed the importance of the Asn, Pro, and Tyr residues to both SHC and IR substrate 1 (IRS-1) binding. We conclude that SHC interacts directly with the IR and that phosphorylation of Tyr-960 within the IR juxtamembrane domain is necessary for efficient interaction. This interaction is highly reminiscent of that of IRS-1 with the IR, and we show that the SHC IR-binding domain can substitute for that of IRS-1 in yeast and COS cells. We identify a homologous region within the IR-binding domains of SHC and IRS-1, which we term the SAIN (SHC and IRS-1 NPXY-binding) domain, which may explain the basis of these interactions. The SAIN domain appears to represent a novel motif which is able to interact with autophosphorylated receptors such as the IR.