Molecular function of the WW domainof Fe65 adaptor protein: towardsunderstanding of signaling byAlzheimer’s amyloid precursor protein

FE65 protein is an important component of the oligomeric complex assembled by the Alzheimer’s amyloid precursor protein (APP). The interaction between APP and FE65 was documented biochemically and genetically. The emerging pathway of signaling by FE65 and APP resembles that of Notch. It involves the presenilin-mediated cleavage of APP that results in the APP fragment/FE65 complex translocation to the nucleus where it affects transcription. FE65 is a typical adapter containing two types of protein modules: theWWdomain and two PTB domains. The first PTB domain interacts functionally with the transcripton factor LSF or the histone acetylase Tip60. The second PTB mediates the complex with APP. The FE65 WW domain interacts with several proteins involved in the nuclear function and in the regulation of cytoskeleton, e.g. MENA and Abl. Since the effects of FE65 on transcription are mediated by itsWWdomains and since FE65 with mutated WW domain has biological effects on the processing of APP, we elected to identify the repertoire of proteins, which interact with the wild-type FE65WW. Two approaches were used. First, the mass spectrometry analysis of proteins pulled-down from mammalian cell lysates by GST-FE65WW fusion protein. Second, the acquisition of data from AxCell Biosciences Company, which mapped all 70WWdomains found in the human proteome for protein–protein interaction profiles. Two dozen proteins were identified as ligands of FE65WW domain by these approaches and selected candidates are being evaluated in cell culture models for their biological effects on APP/FE65 complex and its transcriptional function. Understanding of complexes that nucleate on FE65 and APP could provide rational strategies for controlling APP processing and A peptide production in Alzheimer’s brain.