Cloning and functional expression of a rat kidney extracellular calcium/polyvalent cation-sensing receptor.
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 (BoPCaRI) 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 NH2 terminus 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 Ca(2+)-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.
Riccardi
D
D
Laboratory of Molecular Physiology and Biophysics, Brigham and Women's Hospital, Boston, MA.
Park
J
J
Lee
W S
WS
Gamba
G
G
Brown
E M
EM
Hebert
S C
SC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002712:Chlorides / Q000378:metabolism*; D003001:Cloning, Molecular; D005260:Female; D015870:Gene Expression; D015723:Gene Library; D017403:In Situ Hybridization; D007668:Kidney / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D009928:Organ Specificity; D017433:Protein Structure, Secondary; D018075:RNA, Complementary; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000737:chemistry / Q000502:physiology; D014982:Xenopus laevis
D002712:Chlorides; D018075:RNA, Complementary; D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface; C473605:extracellular calcium cation-sensing receptor, rat