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, or phosphotyrosine binding, domains) of Shc and IRS-1 are recently described domains that bind peptides phosphorylated on tyrosine residues. The PI/PTB domains differ from Src homology 2 (SH2) domains in that their binding specificity is determined by residues that lie amino terminal and not carboxy terminal to the phosphotyrosine. Recently, it has been appreciated that other cytoplasmic proteins also contain PI domains. 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 amyloid precursor protein ((beta)APP). (beta)APP is an integral transmembrane glycoprotein whose cellular function is unknown. One of the processing pathways of (beta)APP leads to the secretion of A(beta), the major constituent of the amyloid deposited in the brain parenchyma and vessel walls of Alzheimer's disease patients. We have found that the X11 PI domain binds a YENPTY motif in the intracellular domain of (beta)APP that is strikingly similar to the NPXY motifs that bind the Shc and IRS-1 PI/PTB domains. However, unlike the case for binding of the Shc PI/PTB domain, tyrosine phosphorylation of the YENPTY motif is not required for 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 within 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. The 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.