Cloning and Functional Expression of a Rat Kidney Extracellular Calcium/ Polyvalent Cation-Sensing Receptor

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 92; no. 1; pp. 131 - 135
• Main Authors: Riccardi, Daniela, Park, Ji, Lee, Wen-Sen, Gamba, Gerardo, Brown, Edward M., Hebert, Steven C.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 03.01.1995; National Acad Sciences; National Academy of Sciences
• Subjects: Amino Acid Sequence; Amino acids; Animals; Base Sequence; Blotting, Northern; Calcium; Calcium sensing receptors; Chlorides - metabolism; Cloning, Molecular; Complementary DNA; Deoxyribonucleic acid; DNA; Female; Gene Expression; Gene Library; In Situ Hybridization; Ions; Kidney - metabolism; Kidneys; Male; Molecular Sequence Data; Nephrons; Oocytes; Oocytes - physiology; Organ Specificity; Protein Structure, Secondary; Rats; Rats, Sprague-Dawley; Receptors; Receptors, Calcium-Sensing; Receptors, Cell Surface - biosynthesis; Receptors, Cell Surface - chemistry; Receptors, Cell Surface - physiology; RNA; RNA, Complementary; RNA, Messenger - analysis; RNA, Messenger - biosynthesis; Rodents; Ungulates; Xenopus laevis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.92.1.131

The maintenance of a stable extracellular concentration of ionized calcium depends on the integrated function of a number of specialized cells (e.g., parathyroid and certain kidney epithelial cells). We recently identified another G protein-coupled receptor (BoPCaR1) from bovine parathyroid that responds to changes in extracellular Ca2+within the millimolar range and provides a key mechanism for regulating the secretion of parathyroid hormone. Using an homology-based strategy, we now report the isolation of a cDNA encoding an extracellular Ca2+/polyvalent cation-sensing receptor (RaKCaR) from rat kidney. The predicted RaKCaR protein shares 92% identity with BoPCaR1 receptor and features a seven membrane-spanning domain, characteristic of the G protein-coupled receptors, which is preceded by a large hydrophilic extracellular NH2terminus believed to be involved in cation binding. RaKCaR cRNA-injected Xenopus oocytes responded to extracellular Ca2+, Mg2+, Gd3+, and neomycin with characteristic activation of inositol phospholipid-dependent, intracellular Ca2+-induced Cl-currents. In rat kidney, Northern analysis revealed RaKCaR transcripts of 4 and 7 kb, and in situ hybridization showed localization primarily in outer medulla and cortical medullary rays. Our results provide important insights into the molecular structure of an extracellular Ca2+/polyvalent cation-sensing receptor in rat kidney and provide another basis on which to understand the role of extracellular divalent cations in regulating kidney function in mineral metabolism.