O1–02–03: Change of cleavage precision by presenilin–dependent gamma–secretase

Background: An unusual characteristics of the PS-dependent intramembrane proteolysis is that some cleavage sites are not single but have a variety. Because of the variety, the cleavage precision can be defined. The cleavage precision is the ratio of the cleavage occurring in each site. The change of the cleavage precision plays a pathological role, since pathological ‘gain-of-function’ of many familial AD-associated PS or betaAPP mutants is considered to be the increase of Abeta42 production induced by change of gamma-cleavage precision. However, it is unclear whether any changes of the cleavage precision play a physiological role. Objective(s): Cleavage precision of betaAPP and Notch-1 were identified and characterized to reveal their pathological and physiological roles. Methods: Combined immunoprecipitation and semi-quantitive MALDI-TOF MS as well as separation of radiolabeled Abeta/Nbeta species and AICD/NICD species by electrophoresis was performed. The cells treated with or without the compounds were subjected to metabolic labeling with [35S] methionine for quantitative analysis. Results: The characteristics of cleavage precision determining process of Nbeta and Abeta are almost identical. Since many other type-1 membrane-bound receptors release intracellular domains by PS-dependent intramembrane proteolysis, we suspect that the release of Abetaor Nbeta-like peptides is a common feature of the proteolysis during RIP signaling. Moreover, the cleavage precision determining process of NICD and AICD are also similar. Conclusions: Our results propose physiological as well as pathological roles for precision of the intramembrane cleavage by PS/gamma-secretase.