Alzheimer's disease is characterized by neuropathological accumulations of
amyloid beta(1-42) [A beta(1-42)], a cleavage product of the
amyloid precursor
protein (APP). Recent studies have highlighted the role of APP in A beta-mediated toxicity and have implicated the
G-protein system; however, the exact mechanisms underlying this pathway are as yet undetermined. In this context, we sought to investigate the role of
calcium upregulation following APP-dependent, A beta-mediated
G-protein activation. Initial studies on the interaction between APP, A beta and Go
proteins demonstrated that the interaction between APP, specifically its C-terminal -YENPTY- region, and Go was reduced in the presence of A beta. Cell death and
calcium influx in A beta-treated cells were shown to be APP dependent and to involve
G-protein activation because these effects were blocked by use of the
G-protein inhibitor,
pertussis toxin. Collectively, these results highlight a role for the
G-protein system in APP-dependent, A beta-induced toxicity and
calcium dysregulation. Analysis of the APP:Go interaction in human brain samples from
Alzheimer's disease patients at different stages of the disease revealed a decrease in the interaction, correlating with
disease progression. Moreover, the reduced interaction between APP and Go was shown to correlate with an increase in membrane A beta levels and
G-protein activity, showing for first time that the APP:Go interaction is present in humans and is responsive to A beta load. The results presented support a role for APP in A beta-induced
G-protein activation and suggest a mechanism by which basal APP binding to Go is reduced under pathological loads of A beta, liberating Go and activating the
G-protein system, which may in turn result in downstream effects including
calcium dysregulation. These results also suggest that specific antagonists of
G-protein activity may have a therapeutic relevance in
Alzheimer's disease.