A novel substrate for analyzing Alzheimer's disease gamma-secretase

Proteolytic processing of Alzheimer's disease amyloid precursor protein (AP P) by beta-secretase leads to A4CT (C99), which is further cleaved by the a s yet unknown protease called gamma-secretase, To study the enzymatic prope rties of gamma-secretase independently of beta-secretase, A4CT together wit h an N-terminal signal peptide (SPA4CT) may be expressed in eukaryotic cell s. However, in all existing SPA4CT proteins the signal peptide is not corre ctly cleaved upon membrane insertion. Here, we report the generation of a m utated SPA4CT protein that is correctly cleaved by signal peptidase and, th us, identical to the APP-derived A4CT. This novel SPA4CT protein is process ed by gamma-secretase in the same manner as APP-derived A4CT and might be v aluable for the generation of transgenic animals shelving amyloid pathology , (C) 1999 Federation of European Biochemical Societies.