THE PHOSPHOTYROSINE INTERACTION DOMAINS OF X11 AND FE65 BIND TO DISTINCT SITES ON THE YENPTY MOTIF OF AMYLOID PRECURSOR PROTEIN

The phosphotyrosine interaction (PI) domains (also known as the PTB, o r phosphotyrosine binding, domains) of She and IRS-1 are recently desc ribed domains that bind peptides phosphorylated on tyrosine residues, The PI/PTB domains differ from Src homology 2 (SH2) domains in that th eir binding specificity is determined by residues that lie amino termi nal and not carboxy terminal to the phosphotyrosine. Recently, it has been appreciated that other cytoplasmic proteins also contain PI domai ns, We now show that the PI domain of X11 and one of the PI domains of FE65, two neuronal proteins, bind to the cytoplasmic domain of the am yloid precursor protein (beta APP), beta APP is an integral transmembr ane glycoprotein whose cellular function is unknown, One of the proces sing pathways of beta APP leads to the secretion of AP, the major cons tituent of the amyloid deposited in the brain parenchyma and vessel wa lls of Alzheimer's disease patients. We have found that the X11 PI dom ain binds a YEPTY motif in the intracellular domain of beta APP that i s strikingly similar to the NPXY motifs that bind the She and IRS-1 PI /PTB domains, However, unlike the case for binding of the She PI/PTB d omain, tyrosine phosphorylation of the YENPTY motif is not required fo r the binding of beta APP to X11 or FE65, The binding site of the FE65 PI domain appears to be different from that of X11, as mutations with in the YENPTY motif differentially affect the binding of X11 and FE65. Using site-directed mutagenesis, we have identified a crucial residue within the PI domain involved in X11 and FE65 binding to beta APP. Th e binding of X11 or FE65 PI domains to residues of the YENPTY motif of beta APP identifies PI domains as general protein interaction domains and may have important implications for the processing of beta APP.