G protein and cAMP-dependent protein kinase mediate amyloid beta-peptide inhibition of neuronal glucose uptake

The mechanism by which amyloid beta -peptide (AP) inhibits glucose uptake in cultured cells is not known. Here we demonstrated a signaling pathway in which A beta 25-35, a neurotoxic portion of the A beta peptide corresponding to amino acids 25-35, inhibits neuronal glucose uptake by hippocampal neurons. The GP antagonist-2, which blocks Gs, prevented the inhibitory effect of A beta on the glucose uptake. Exposure of cells to A beta resulted in a transitory increase in intracellular levels of cAMP. To assess the role of cAMP in neuronal glucose uptake, cultured neurons were exposed to dibutyryl cAMP (Bt(2)cAMP) or an adenylyl cyclase activator, forskolin. Both Bt(2)cAMP and forskolin inhibited neuronal glucose uptake, and cAMP-dependent protein kinase (PKA) inhibitor KT5720 blocked the A beta -mediated inhibition of glucose uptake. Cholera toxin, which stimulates adenylyl cyclase by activating Gs protein, also inhibited neuronal glucose uptake, and A beta potentiated this inhibitory effect of cholera toxin on glucose uptake. Thus, our findings suggest that A beta inhibits glucose uptake by activating the Gs-coupled receptors and involves the cAMP-PKA system. (C) 2001 Academic Press.