Characterization of the cloned HEL cell thromboxane A2 receptor: evidence that the affinity state can be altered by G alpha 13 and G alpha q.
Characterization of the cloned HEL cell thromboxane A2 receptor: evidence that the affinity state can be altered by G alpha 13 and G alpha q.
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发表时间：
1996-05
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通讯作者：
C. J. Allan;K. Higashiura;M. Martin;T. Morinelli;D. T. Kurtz;O. Geoffroy;G. Meier;T. Gettys;P. Halushka
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作者：
C. J. Allan;K. Higashiura;M. Martin;T. Morinelli;D. T. Kurtz;O. Geoffroy;G. Meier;T. Gettys;P. Halushka
血栓烷 A2 (TXA2) 通过细胞表面受体诱导血小板活化和血管平滑肌收缩。来自巨核细胞样 HEL 细胞的血小板型 TXA2 受体被克隆，其推导的氨基酸序列与先前报道的人胎盘 TXA2 受体的氨基酸序列相同。 HEL 细胞 TXA2 受体 cDNA 的瞬时表达和与激动剂 125I-BOP 的放射性配体结合研究显示，具有与低亲和力血小板 TXA2 受体相当的亲和力的单一类别结合位点。使用一系列区分血小板和血管平滑肌中TXA2受体亚型的13-氮杂庚烷TXA2类似物，我们发现克隆的HEL细胞TXA2受体具有血小板型TXA2受体的特征，并且其结合特征不同于血管平滑肌细胞的结合特征。在单独与 G α 13 或单独与 G α q 以及与 G α 13 和 G α 12 一起共转染后，HEL 细胞 TXA2 受体对 125 I-BOP 的亲和力显着增加 (P < .05) (n = 4-6)。 GTP gamma S 显着 (P < .05) 降低了共表达 HEL-TXR 和 G α 13 的 COS-7 细胞膜上受体对 125I-BOP 的亲和力，其值与单独的 HEL-TXA2 受体相当。我们得出结论：1) 克隆的 HEL 细胞 TXA2 受体具有低亲和力血小板型受体的药理学特征，2) 该受体的亲和状态可能受到与 G α 13 和 G α q 相互作用的影响。
Thromboxane A2 (TXA2) induces activation of platelets and vascular smooth muscle contraction via cell surface receptors. A platelet type TXA2 receptor from the megakaryocyte-like HEL cell was cloned with a deduced amino acid sequenced identical to that previously reported for the human placental TXA2 receptor. Transient expression of the HEL cell TXA2 receptor cDNA and radioligand binding studies with the agonist 125I-BOP showed a single class of binding sites with an affinity comparable to a low affinity platelet TXA2 receptor. Using a series of 13-azapinane TXA2 analogs, which discriminate between TXA2 receptor subtypes in platelets and vascular smooth muscle, we found that the cloned HEL cell TXA2 receptor is characteristic of a platelet type TXA2 receptor and that its binding characteristics are different from those of vascular smooth muscle cells. The affinity of the HEL cell TXA2 receptor for 125I-BOP was significantly (P < .05) increased upon co-transfection with G alpha 13 alone, or with G alpha q alone and with G alpha 13 and G alpha 12 together (n = 4-6). GTP gamma S significantly (P < .05) decreased the affinity of the receptor for 125I-BOP in COS-7 cell membranes coexpressing HEL-TXR and G alpha 13 to a value comparable to HEL-TXA2 receptor alone. We conclude that 1) the cloned HEL cell TXA2 receptor has pharmacological characteristics of a low affinity platelet type receptor and 2) that the affinity state of this receptor may be influenced by interaction with G alpha 13 and G alpha q.