Identification and characterization of a neuronal enriched novel transcript encoding the previously described p60Fe65 isoform.

Fe65 is a multimodular adaptor protein that interacts with the cytosolic domain of the β-amyloid precursor protein (APP), the major component of Alzheimer's disease (AD) senile plaques. In the work here presented, we describe the existence of a new Fe65 transcript variant (GenBank Accession EF103274). A unique 5' sequence of 69 nucleotides, spanning a region between exons 2 and 3 of the FE65 gene, was present in a yeast two-hybrid (YTH) clone from a human brain cDNA library. In silico analysis and RT-PCR revealed the presence of a novel exon of 133 bp, and we redefined the structure of the human FE65 gene. The novel exon 3a-inclusive transcript generates a shorter isoform, p60Fe65. The migration pattern of the p60Fe65 isoform was observed previously and attributed to an alternative translation initiation site within the p97Fe65 transcript. Here, we provide evidence for the origin of the previously unexplained p60Fe65 isoform. Moreover, Fe65E3a is expressed preferentially in the brain and the p60Fe65 protein levels increased during PC12 cell differentiation. This novel Fe65 isoform and the regulation of the splicing events leading to its production, may contribute to elucidating neuronal specific roles of Fe65 and its contribution to AD pathology.