Alternative titles; symbols
HGNC Approved Gene Symbol: NPBWR2
Cytogenetic location: 20q13.33 Genomic coordinates (GRCh38): 20:64,103,802-64,107,565 (from NCBI)
Opioid receptors belong to the family of G protein-coupled receptors and are the primary sites of interaction of the endogenous opioid peptides (O'Dowd et al., 1995). At least 3 major types are known, designated mu (OPRM1; 600018), delta (OPRD1; 165195), and kappa (OPRK1; 165196). This classification has been based on pharmacologic and bioassay characteristics . In a search for additional members of the opioid receptor gene family, O'Dowd et al. (1995) cloned and characterized 2 novel and related human genes, named GPR7 (600730) and GPR8 (for 'G protein-coupled receptor'), encoding receptors with structural features in common with both opioid and somatostatin receptors. The 2 genes were demonstrated to have discrete distributions in the brain. The intronless coding sequences of GPR7 and GPR8 had 70% identity with each other and each shared significant similarity with the sequences encoding transmembrane regions of the opioid and somatostatin receptors. Northern blot analysis using human mRNA demonstrated expression of GPR7 mainly in cerebellum and frontal cortex, while GPR8 was located mainly in the frontal cortex. In situ hybridization revealed expression of GPR7 in the human pituitary. Initial pharmacologic studies indicated binding to several opioid drugs, but not to the opioid receptor subtype-specific mu, delta, or kappa agonists.
By RT-PCR, Brezillon et al. (2003) detected high levels of GPR8 expression in caudate nucleus, hippocampus, and amygdala. Moderate levels were detected in adult brain, thalamus, parietal cortex, pituitary gland, adrenal gland, lymph nodes, and lymphoblastic leukemia.
Brezillon et al. (2003) identified and partially characterized 2 endogenous ligands of GPR8, NPB (607996) and NPW (607997).
By fluorescence in situ hybridization, O'Dowd et al. (1995) mapped the GPR8 gene to 20q13.3. They suggested that a sequence related to GPR8 may be present on 14q23-q24.
In connection with an examination of the sequence homology between human chromosome 20 and mouse chromosome 2, Zhu et al. (2003) found that the relative position of each of 460 putative coding orthologs was the same in the 2 species, except for a single genomic segment rearrangement. This similarity extended to exon/intron structure and the size of introns, as well as providing strong evidence for the conservation of position of ancient LINE-1, LINE-2, and LTR repetitive sequence. There was also evidence for conservation of the limited amount of noncoding single-copy sequence.
Brezillon, S., Lannoy, V., Franssen, J.-D., Le Poul, E., Dupriez, V., Lucchetti, J., Detheux, M., Parmentier, M. Identification of natural ligands for the orphan G protein-coupled receptors GPR7 and GPR8. J. Biol. Chem. 278: 776-783, 2003. [PubMed: 12401809] [Full Text: https://doi.org/10.1074/jbc.M206396200]
O'Dowd, B. F., Scheideler, M. A., Nguyen, T., Cheng, R., Rasmussen, J. S., Marchese, A., Zastawny, R., Heng, H. H. Q., Tsui, L.-C., Shi, X., Asa, S., Puy, L., George, S. R. The cloning and chromosomal mapping of two novel human opioid-somatostatin-like receptor genes, GPR7 and GPR8, expressed in discrete areas of the brain. Genomics 28: 84-91, 1995. [PubMed: 7590751] [Full Text: https://doi.org/10.1006/geno.1995.1109]
Zhu, L., Swergold, G. D., Seldin, M. F. Examination of sequence homology between human chromosome 20 and the mouse genome: intense conservation of many genomic elements. Hum. Genet. 113: 60-70, 2003. [PubMed: 12644935] [Full Text: https://doi.org/10.1007/s00439-003-0920-x]