Differential desensitization of thromboxane A2 receptor subtypes.
Differential desensitization of thromboxane A2 receptor subtypes.
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血栓素 A2 受体亚型的差异脱敏。
DOI：
10.1161/01.res.80.4.551
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发表时间：
1997
影响因子：
20.1
通讯作者：
Ware,JA
中科院分区：
文献类型：
--
作者：
Yukawa,M;Yokota,R;Eberhardt,RT;vonAndrian,L;Ware,JA
血栓素A2(TXA2)受体的两个亚型(TxA2R-E和TxA2R-P)已被鉴定，它们的胞浆尾部选择性剪接不同。在高表达TxA2R-E或-P亚型的成纤维细胞中，第二次加入IBOP(100nmol/L)所需的TxA2模拟IBOP的初始浓度(IC50)相似(对TxA2R-E和TxA2R-P分别为0.46±0.16和0.40±0.07nmol/L)。经TxA2模拟物长时间刺激后，TxA2R-P细胞的TxA2结合位点数减少，但TxA2R-E细胞的TxA2结合位点数显著增加。为了确定脱敏机制是否因亚型不同而不同，检测了蛋白激酶C(PKC)或cAMP依赖的激酶激活对TXA2诱导的[Ca~(2+)]固定的影响。福司可林对IBOP诱导的TxA2R-E和TxA2R-P细胞[Ca~(2+)]i均无抑制作用；佛波酯(IC50，0.57±0.70nmol/L)可显著抑制IBOP诱导的TxA_2R-E细胞[Ca~(2+)]i升高，但对TxA_2R-P细胞无明显影响。PKC抑制剂Calphostin C或下调PKC-α可阻止佛波酯对TxA2R-E的脱敏作用。因此，TxA2R-E对长时间刺激的反应与TxA2R-P的不同之处在于结合位点数的调节和脱敏机制；激活PKC-α的激动剂可能会干扰TxA2R-E介导的信号转导。
Two subtypes of the thromboxane A2(TxA2) receptor (TxA2R-E and TxA2R-P), which differ in their alternatively spliced cytoplasmic tails, have been identified. The initial concentration of the TxA2mimetic IBOP required to reduce peak intracellular Ca2+concentration ([Ca2+]i) induced by a second addition of IBOP (100 nmol/L) was similar (IC50for TxA2R-E and TxA2R-P, 0.46±0.16 and 0.40±0.07 nmol/L) in fibroblasts overexpressing either the TxA2R-E or -P subtype. Although the number of TxA2binding sites decreased in TxA2R-P cells after prolonged stimulation with a TxA2mimetic, those in the TxA2R-E cells increased markedly. To determine whether the mechanism for desensitization differs between subtypes, the effect of activation of protein kinase C (PKC) or cAMP-dependent kinase on TxA2-induced [Ca2+]imobilization was measured. Forskolin reduced the IBOP-induced peak [Ca2+]iin neither TxA2R-E nor TxA2R-P cells; however, treatment with phorbol esters (IC50, 0.57±0.70 nmol/L) strongly prevented IBOP-mediated [Ca2+]irise in TxA2R-E but not in TxA2R-P cells. Desensitization of TxA2R-E by phorbol esters was prevented by the PKC inhibitor calphostin C or by downregulation of PKC-α. Thus, the response of TxA2R-E to prolonged stimulation differs from that of TxA2R-P in both the regulation of the number of binding sites and the mechanism for desensitization; agonists that activate PKC-α might interfere with TxA2R-E–mediated signaling.