G protein-coupled receptor 45 (GPR45) is a transmembrane receptor that mediates signaling processes to the interior of the cell via activation of heterotrimeric G proteins. GPR45 functions in the central nervous system, and it is thought to regulate energy expenditure and POMC signaling. Mutations in GPR45 can lead to obesity, and this receptor may be target of interest in obesity therapies. In immunohistochemistry, GPR45 has membranous positivity on neurons in the substantia nigra and nucleus basalis of Meynert in the brain, and has faint positivity on astrocytes in the amygdala and Bergman glia. Scattered positivity on neurons is also seen in other regions in the brain. Outside of the nervous system, genitourinary epithelial cells in the kidney and bladder express GPR45, and it is also present in adipocytes and has faint positivity in epithelial tissues. In cancer, GPR45 is expressed on neoplastic cells in glioblastoma multiforme, malignant melanoma, and breast, lung, and ovarian adenocarcinomas. References: J Clin Invest. 2016 Sep 1;126(9):3192-206, PMID: 27500489;