We previously demonstrated that cyclic guanosine monophosphate (cGMP) stimulates amyloid precursor protein (APP) and beta-secretase (BACE1) approximation in neuronal endo-lysosomal compartments, thus boosting the production of amyloid-\u3b2 (A\u3b2) peptides and enhancing synaptic plasticity and memory. Here, we further investigated the mechanism by which cGMP regulates the subcellular localization of APP and BACE1, finding that the cyclic nucleotide inhibits the activity of Rab5, a small GTPase associated with the plasma membrane and early endosomes. Accordingly, we also found that expression of a dominant-negative Rab5 mutant increases both APP-BACE1 approximation and A\u3b2 extracellular levels, therefore mimicking the effects induced by cGMP. These results reveal a functional correlation between the cGMP/A\uf062 pathway and the activity of Rab5 that may contribute to the understanding of Alzheimer\u2019s disease pathophysiology
