G protein betagamma complex-mediated apoptosis by familial Alzheimer's disease mutant of APP

Abstract

In familial Alzheimer's disease (FAD), three missense mutations, V642I, V642F and V642G, that co-segregate with the disease phenotype have been discovered in the 695 amino acid form of the amyloid precursor protein APP. Expression of these mutants causes a COS cell NK1 clone to undergo pertussis toxin-sensitive apoptosis in an FAD trait-linked manner by activating the G protein Go, which consists of G alpha(o) and G betagamma subunits. We investigated which subunit was responsible for the induction of apoptosis by V642I APP in NK1 cells. In the same system, expression of mutationally activated G alpha(o) or G alpha(i) induced little apoptosis. Apoptosis by V642I APP was antagonized by the overexpression of the carboxy-terminal amino acids 495-689 of the beta-adrenergic receptor kinase-1, which blocks the specific functions of G betagamma. Co-transfection of G beta2gamma2 cDNAs, but not that of other G beta(x)gamma(z) (x = 1-3; z = 2, 3), induced DNA fragmentation in a manner sensitive to bcl-2. These data implicate G betagamma as a cell death mediator for the FAD-associated mutant of APP.