This group includes orphan receptors GPR158, GPR158-like (also called GPR179) and similar proteins. These orphan receptors are closely related to the type B receptor for gamma-aminobutyric acid (GABA-B), which is activated by its endogenous ligand GABA, the principal inhibitory neurotransmitter []. Both GPR179 and GPR158 were shown to recruit regulator of G protein signaling (RGS) complexes and thus regulate activity of other GPCRs []. GPR158 has been suggested to act as a homeostatic regulator of intraocular pressure and could be a pharmacological target for managing ocular hypertension [, ]. It has been linked to prostate cancer growth and progression []. It also serves as a novel regulator operating in the prefrontal cortex (PFC) that links chronic stress to depression []. GPR179 has been shown to play a critical role in depolarizing bipolar cell signal transduction. It is mutated in autosomal-recessive complete congenital stationary night blindness [].
