RAB5A and Alzheimer disease: For example, in postmortem brains of AD patients, enlargement of Rab5-positive EEs and upregulation of Rab4 were observed in pyramidal neurons of the prefrontal cortex at the early-stages (Cataldo et al., 2000), and upregulation of Rab4, Rab5, Rab7, and Rab27 was observed in the cholinergic basal forebrain neurons (Ginsberg et al., 2011).