G-protein α-subunit levels in hippocampus and entorhinal cortex of brains staged for Alzheimer's disease neurofibrillary and amyloid pathologies

G-protein alpha-subunits (Galpha(o), Galpha(i), Galpha(s), Galpha(q)) and adenylyl cyclase (AC) I and II isoforms were quantified in hippocampus and entorhinal cortex from 22 cases staged for Alzheimer's disease (AD) pathologies according to Braak and Braak. Hippocampal Galpha(i) levels declined significantly with neurofibrillary staging, whereas AC I levels in this region increased. Significant amyloid stage-related reductions of Galpha(i) were seen in both the hippocampus and entorhinal cortex. The hippocampus also showed a significant reduction of Galpha(o) with amyloid staging. It is concluded that levels of inhibitory G-protein subunits Galpha(o), and in particular Galpha(i), decrease in parallel to the extent of AD pathology.