CHARACTERIZATION OF HUMAN PRESENILIN-1 USING N-TERMINAL SPECIFIC MONOCLONAL-ANTIBODIES - EVIDENCE THAT ALZHEIMER MUTATIONS AFFECT PROTEOLYTIC PROCESSING

The majority of cases of early-onset familial Alzheimer disease are ca used by mutations in the recently identified presenilin 1 (PS1) gene, located on chromosome 14, PS1, a 467 amino acid protein, is predicted to be an integral membrane protein containing seven putative transmemb rane domains and a large hydrophilic loop between the sixth and sevent h membrane-spanning domain, We produced 7 monoclonal antibodies that r eact with 3 non-overlapping epitopes on the N-terminal hydrophilic tai l of PS1, The monoclonal antibodies can detect the full-size PS1 at M( r) 47 000 and a more abundant M(r) 28 000 product in membrane extracts from human brain and human cell lines, PC12 cells transiently transfe cted with PS1 constructs containing two different Alzheimer mutations fail to generate the 28 kDa degradation product in contrast to PC12 ce lls transfected with wild-type PS1. Our results indicate that missense mutations in this form of familial Alzheimer disease may act via a me chanism of impaired proteolytic processing of PS1.