Members of the G protein-coupled receptor (GPCR) family, such as GPR85, have a similar structure characterized by 7 transmembrane domains. Activation of GPCRs by extracellular stimuli, such as neurotransmitters, hormones, or light, induces an intracellular signaling cascade mediated by heterotrimeric GTP-binding proteins, or G proteins (Matsumoto et al., 2000 [PubMed 10833454]).[supplied by OMIM, Aug 2008].