A 127-kDa protein (UV-DDB) binds to the cytoplasmic domain of the Alzheimer's amyloid precursor protein

Alzheimer amyloid precursor protein (APP) is an integral membrane protein w ith a short cytoplasmic domain of 47 amino acids. It is hoped that identifi cation of proteins that interact with the cytoplasmic domain will provide n ew insights into the physiological function of APP and, in turn, into the p athogenesis of Alzheimer's disease. To identify proteins that interact with the cytoplasmic domain of APP, we employed affinity chromatography using a n immobilized synthetic peptide corresponding to residues 645-694 of APP(69 5), and identified a protein of similar to 130 kDa in rat brain cytosol. Am ino acid sequencing of the protein revealed the protein to be a rat homolog ue of monkey UV-DDB (UV-damaged DNA-binding protein, calculated molecular m ass of 127 kDa), UV-DDB/p127 co-immunoprecipitated with APP using an anti-A PP antibody from PC12 cell lysates. APP also coimmunoprecipitated with UV-D DB/p127 using an anti-UV-DDB/p127 antibody. These results indicate that UV- DDB/p127, which is present in the cytosolic fraction, forms a complex with APP through its cytoplasmic domain. In vitro binding experiments using a gl utathione S-transferase-APP cytoplasmic domain fusion protein and several m utants indicated that the YENPTY motif within the APP cytoplasmic domain, w hich is important in the internalization of APP and amyloid beta protein se cretion, may be involved in the interaction between UV-DDB/p127 and APP.