Alternative titles; symbols
HGNC Approved Gene Symbol: PAQR8
Cytogenetic location: 6p12.2 Genomic coordinates (GRCh38) : 6:52,362,151-52,407,777 (from NCBI)
Suzuki et al. (2001) identified an EST for LMPB1 within the juvenile myoclonic epilepsy-1 (EJM1; 254770) critical region of chromosome 6, and they obtained the full-length cDNA by screening an adult brain cDNA library. The deduced 354-amino acid protein has a calculated molecular mass of about 40 kD. LMPB1 has 8 putative transmembrane regions and an intracellular N terminus that contains a leucine-rich motif. The protein is translated from the second of 2 possible start codons, and the 3-prime untranslated region contains 5 potential polyadenylation sites. Northern blot analysis detected 5- and 3-kb transcripts expressed predominantly in whole brain and in all adult brain regions tested. Similar results were found in mouse, except that mouse testis showed a 2-kb transcript. Northern blot analysis was unable to detect LMPB1 expression in human or mouse fetal tissues, including brain. By confocal imaging of transfected HeLa cells, Suzuki et al. (2001) detected a punctate cytoplasmic distribution of fluorescence-tagged LMPB1. Double staining for cathepsin D (116840) showed extensive overlap, indicating that LMPB1 associated with lysosomes. Colocalization of cathepsin D and LMPB1 was also found by subcellular fractionation, and Triton X-114 phase separation confirmed that LMPB1 is an integral membrane protein.
Using homology with the sequence of seatrout membrane progestin receptor, Zhu et al. (2003) identified ESTs containing MPRB, and they cloned full-length cDNAs from several vertebrate species, including human. The deduced proteins contain 352 to 354 amino acids, consisting of an extracellular N terminus, an intracellular C terminus, and 7 transmembrane domains. Northern blot analysis detected a major 5.2-kb transcript and minor 3.2- and 2.8-kb transcripts expressed only in brain. RNA dot blot analysis detected expression in all brain and spinal cord regions examined except pituitary.
Tang et al. (2005) stated that the deduced full-length 359-amino acid PAQR8 protein contains a 7-transmembrane domain that shares significant similarity with the transmembrane domains of ADIPOR1 (607945) and ADIPOR2 (607946). Database analysis identified the mouse ortholog, which shares 94% identity with human PAQR8. RT-PCR detected only weak PAQR8 expression in human lung, adrenal gland, stomach, colon, lymph node, kidney, brain, testis, bladder, small intestine, breast, heart, thymus, and adult bone marrow. No expression was detected in other tissues examined.
Zhu et al. (2003) determined that recombinant mouse Mprb, expressed by E. coli, showed high-affinity progesterone binding.
Suzuki et al. (2001) determined that the LMPB1 gene contains 2 exons and spans about 44 kb. The complete coding region and 3-prime untranslated region is coded by exon 2.
Suzuki et al. (2001) mapped the LMPB1 gene within the EJM1 critical region of chromosome 6p12. By genomic sequence analysis, Tang et al. (2005) mapped the PAQR8 gene to chromosome 6p12.2.
Suzuki, T., Ganesh, S., Agarwala, K. L., Morita, R., Sugimoto, Y., Inazawa, J., Delgado-Escueta, A. V., Yamakawa, K. A novel gene in the chromosomal region for juvenile myoclonic epilepsy on 6p12 encodes a brain-specific lysosomal membrane protein. Biochem. Biophys. Res. Commun. 288: 626-636, 2001. [PubMed: 11676489] [Full Text: https://doi.org/10.1006/bbrc.2001.5825]
Tang, Y. T., Hu, T., Arterburn, M., Boyle, B., Bright, J. M., Emtage, P. C., Funk, W. D. PAQR proteins: a novel membrane receptor family defined by an ancient 7-transmembrane pass motif. J. Molec. Evol. 61: 372-380, 2005. [PubMed: 16044242] [Full Text: https://doi.org/10.1007/s00239-004-0375-2]
Zhu, Y., Bond, J., Thomas, P. Identification, classification, and partial characterization of genes in humans and other vertebrates homologous to a fish membrane progestin receptor. Proc. Nat. Acad. Sci. 100: 2237-2242, 2003. [PubMed: 12601167] [Full Text: https://doi.org/10.1073/pnas.0436133100]