APP and Alzheimer disease: Numerous studies have presented evidence that implicate GPCRs in the pathogenesis of Alzheimer’s disease (AD) and in multiple stages of the hydrolytic processing of amyloid protein precursor (APP), a precursor protein involved in the formation of amyloid plaques found in AD patients’ brain (Thathiah and De Strooper, 2009, 2011; Wisely et al., 2014).