GPR3 and Alzheimer disease: For example, β-arrestin 2 has been found to increase Aβ production upon binding with two GPCRs, the orphan GPCR, G Protein-Coupled Receptor 3 (GPR3) and β2 adrenergic receptor, in both in vitro and in vivo models of AD (Jiang et al., 2013; Thathiah et al., 2013).