Engineering of a Synthetic α-Secretase

Abstract

The excessive accumulation of amyloid- (A is implicated in the pathogenesis of Alzheimer’s disease (AD). Recent clinical studies have demonstrated that elimination of A is a viable therapeutic strategy. In the current study, we conceptualized a fusion membrane protein, referred to as synthetic -secretase (SAS), designed to cleave specifically amyloid precursor protein (APP) and A at the -site. In mammalian cells, SAS indeed cleaved APP and A at the targeted -site. Overexpression of SAS in the hippocampus was achieved by stereotaxic injection of recombinant adeno-associated virus serotype 9 (AAV9) encoding SAS (AAV9-SAS) into the bilateral ventricles of mouse brains. Consequently, SAS enhanced the non-amyloidogenic processing of APP, and reduced the levels of soluble A and plaques in the 5xFAD mice. Furthermore, SAS significantly attenuated the cognitive deficits in 5xFAD and App knock-in (NL-G-F/NL-G-F) mice, as demonstrated through novel object recognition and Morris water maze tests. Unlike other A -cleaving proteases, SAS has highly strict substrate specificity. I propose that SAS can be an efficient modality to eliminate excessive A from diseased brains. I further obtained and characterized SAS variants with increased proteolytic activity (SASN70Q, SASScMV, and SASWpMV), altered subcellular localizations (SAS 0, SASGPI, SASSEC, SASFUR, SASDUAL, SASFC5), and reduced immunogenicity (SASK114P, SAST117D). I propose that these findings would be valuable for optimizing SAS as a therapeutic candidate for various A -related diseases.