Extracellular Ca2+-sensing receptor is a promiscuous divalent cation sensor that responds to lead
Extracellular Ca2+-sensing receptor is a promiscuous divalent cation sensor that responds to lead
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DOI：
10.1152/ajprenal.2000.279.6.f1083
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发表时间：
2000-12-01
影响因子：
4.2
通讯作者：
Miller, RT
中科院分区：
文献类型：
--
作者：
Handlogten, ME;Shiraishi, N;Miller, RT
细胞外Ca（2+）敏感受体（CaR）对包括Ca（2+）和新霉素在内的聚阳离子有反应。该受体是全身Ca（2+）代谢的生理调节剂，也可能介导高钙血症的毒性作用。许多二价阳离子，包括Pb（2+）、Co（2+）、Cd（2+）和Fe（2+），对肾、脑和表达CaR的其他组织是有毒的。为了确定哪些二价阳离子可以激活CaR，我们在HEK-293细胞中表达了人CaR，并测量了磷脂酶A（2）（PLA（2））和促分裂原活化蛋白激酶p42 ERK对受体潜在激动剂的响应。表达非功能性突变体CaR R796 W的HEK-293细胞作为对照。细胞外Ca（2+）、Ba（2+）、Cd（2+）、Co（2+）、Fe（2+）、Gd（3+）、Ni（2+）、Pb（2+）和新霉素对CaR有激活作用，而Hg（2+）和Fe（3+）对CaR无激活作用。我们分析了Ca（2+）、Co（2+）和Pb（2+）对CaR激活p42 ERK和PLA 2的动力学。EC（50）值范围从Pb（2+）的0.1 mM到Ca（2+）的4.0 mM。希尔系数>3，表明多个协同配体结合位点或亚基。次高浓度的Ca（2+）和Pb（2+）对CaR的激活有相加作用。Ca（2+）或Pb（2+）的EC（50）因另一种离子的存在而降低4 - 5倍。这些二价阳离子还通过稳定表达CaR的Madin-Darby犬肾细胞中的CaR激活PLA（2）。我们的结论是，许多二价阳离子激活的CaR和它们的影响是加性的。事实上，CaR是一种混杂的聚阳离子传感器，这些离子的作用是相加的激活它表明，CaR可能有助于一些重金属，如铅（2+），镉（2+），钴（2+），和铁（2+）的肾脏和其他组织中表达的毒性。
The extracellular Ca(2+)-sensing receptor (CaR) responds to polycations, including Ca(2+) and neomycin. This receptor is a physiological regulator of systemic Ca(2+) metabolism and may also mediate the toxic effects of hypercalcemia. A number of divalent cations, including Pb(2+), Co(2+), Cd(2+), and Fe(2+), are toxic to the kidney, brain, and other tissues where the CaR is expressed. To determine which divalent cations can activate the CaR, we expressed the human CaR in HEK-293 cells and measured activation of phospholipase A(2) (PLA(2)) and the mitogen-activated protein kinase p42ERK in response to potential agonists for the receptor. HEK-293 cells expressing the nonfunctional mutant CaR R796W served as controls. Extracellular Ca(2+), Ba(2+), Cd(2+), Co(2+), Fe(2+), Gd(3+), Ni(2+), Pb(2+), and neomycin activated the CaR, but Hg(2+) and Fe(3+) did not. We analyzed the kinetics of activation of p42ERK and PLA2 by the CaR in response to Ca(2+), Co(2+), and Pb(2+). The EC(50) values ranged from similar to0.1 mM for Pb(2+) to similar to4.0 mM for Ca(2+). The Hill coefficients were >3, indicating multiple cooperative ligand binding sites or subunits. Submaximal concentrations of Ca(2+) and Pb(2+) were additive for activation of the CaR. The EC(50) for Ca(2+) or Pb(2+) was reduced four- to fivefold by the presence of the other ion. These divalent cations also activated PLA(2) via the CaR in Madin-Darby canine kidney cells that stably express the CaR. We conclude that many divalent cations activate the CaR and that their effects are additive. The facts that the CaR is a promiscuous polycation sensor and that the effects of these ions are additive to activate it suggest that the CaR may contribute to the toxicity of some heavy metals such as Pb(2+), Cd(2+), Co(2+), and Fe(2+) for the kidney and other tissues where it is expressed.