Cloning and characterization of a calcium-sensing receptor from the hypercalcemic New Zealand white rabbit reveals unaltered responsiveness to extracellular calcium
Cloning and characterization of a calcium-sensing receptor from the hypercalcemic New Zealand white rabbit reveals unaltered responsiveness to extracellular calcium
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DOI：
10.1359/jbmr.1997.12.4.568
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发表时间：
1997-04-01
影响因子：
6.2
通讯作者：
Brown, EM
中科院分区：
文献类型：
--
作者：
Butters, RR;Chattopadhyay, N;Brown, EM
最近从哺乳动物甲状旁腺、肾脏、脑和甲状腺中克隆的细胞外钙(Ca-0(2+))敏感受体(CAR)在维持Ca-0(2+)的近恒定中起着核心作用。我们以前表明，新西兰白兔正常存在的高钙血症与钙0(2+)调节的甲状旁腺激素释放(钙0(2+)水平一半最大地抑制激素分泌)的设定点升高有关，这一观察表明兔甲状旁腺的钙0(2+)敏感机制发生了变化，我们现在通过分离和鉴定CAR的兔同源基因来追求这一可能性，克隆的兔肾CAR(RabCaR)具有高度的总体同源性(>；与牛、人和大鼠CARS的氨基酸同源性为90%)，尽管在可能参与结合配体的胞外区的几个区域略有不同，但通过Northern分析和/或免疫组织化学，在甲状旁腺、甲状腺C细胞、小肠和大肠，以及肾脏的粗大上肢和集合管中也表达了类似或相同的受体，当在HEK293细胞中瞬时表达并通过CAR激动剂诱导的Ca-i(2+)增加进行功能检测时，兔CAR对Ca-0(2+)，Mg-0(2+)，和Gd-0(3+)，与使用人类CAR同时进行的研究中观察到的那些难以区分，因此，至少从其在HEK293细胞中表达时增加钙离子的能力来评估，CAR的内在功能特性不能解释新西兰大白兔体内观察到的高钙血症。
The extracellular Ca2+ (Ca-0(2+))-sensing receptor (CaR) recently cloned from mammalian parathyroid, kidney, brain, and thyroid plays a central role in maintaining near constancy of Ca-0(2+). We previously showed that the hypercalcemia normally present in New Zealand white rabbits is associated with an elevated set point for Ca-0(2+)-regulated PTH release (the level of Ca-0(2+) half-maximally inhibiting hormonal secretion), This observation suggested an alteration in the Ca-0(2+)-sensing mechanism in the rabbit parathyroid, a possibility we have now pursued by isolating and characterizing the rabbit homolog of the CaR, The cloned rabbit kidney CaR (RabCaR) shares a high degree of overall homology (>90% amino acid identity) with the bovine, human, and rat CaRs, although it differs slightly in several regions of the extracellular domain potentially involved in binding ligands, By Northern analysis and/or immunohistochemistry, a similar or identical receptor is also expressed in parathyroid, thyroid C cells, small and large intestine, and in the thick ascending limb and collecting ducts of the kidney, When expressed transiently in HEK293 cells and assayed functionally through CaR agonist-evoked increases in Ca-i(2+) the rabbit CaR shows apparent affinities for Ca-0(2+), Mg-0(2+), and Gd-0(3+) that are indistinguishable from those observed in studies carried out concomitantly using the human CaR, Therefore, at least as assessed by its ability to increase Ca-i(2+) when expressed in HEK293 cells, the intrinsic functional properties of the rabbit CaR cannot explain the hypercalcemia observed in vivo in the New Zealand white rabbit.