Thromboxane A2 activates phospholipase C in astrocytoma cells via pertussis toxin-insensitive G-protein.
Thromboxane A2 activates phospholipase C in astrocytoma cells via pertussis toxin-insensitive G-protein.
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DOI：
10.1016/0014-2999(89)90331-2
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发表时间：
1989-03
影响因子：
5
通讯作者：
N. Nakahata;I. Matsuoka;T. Ono;H. Nakanishi
中科院分区：
文献类型：
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作者：
N. Nakahata;I. Matsuoka;T. Ono;H. Nakanishi
在 1321N1 人星形细胞瘤细胞中检查了血栓素 A2 (TXA2) 受体的特性。 9,11-Epithio-11,12-methanothromboxane A2(STA2) 是 TXA2 的稳定类似物，可刺激磷酸肌醇 (IPs) 的积累，EC50 约为 50 nM。 STA2 诱导的 IP 积累受到 TXA2 受体拮抗剂 ONO3708 的浓度依赖性抑制，抑制常数 (Ki) 约为 10 nM。响应 STA2，肌醇三磷酸 (IP3) 的积累速度比肌醇二磷酸 (IP2) 更快。 HPLC分析表明肌醇1,4,5-三磷酸在STA2存在下积累。单独的 STA2 对膜制剂中 IP 的积累没有影响，但它增强了 GTPγS 诱导的积累。 [3H]SQ29548 是一种 TXA2 受体拮抗剂，与 TXA2 受体特异性结合，表达解离常数 (Kd) 为 10.9 nM 的单一结合位点。 [3H]SQ29548 结合的 STA2 抑制竞争曲线向右移动，并且在 GTPγS 存在的情况下更加陡峭。百日咳毒素 (IAP) 引发 41KD 蛋白的 ADP-核糖基化，但对 SQ29548 结合的 STA2 抑制或 STA2 诱导的 IP 积累对 GTP 的敏感性没有影响。从这些结果可以得出结论，TXA2受体的刺激导致通过GTP结合蛋白激活磷脂酶C，并且该蛋白不是IAP的底物。
The properties of thromboxane A2(TXA2) receptors were examined in 1321N1 human astrocytoma cells. 9,11-Epithio-11,12-methanothromboxane A2(STA2), a stable analogue of TXA2, stimulated the accumulation of inositol phosphates (IPs) with an EC50of about 50 nM. The STA2-induced accumulation of IPs was inhibited concentration dependently by ONO3708, a TXA2receptor antagonist, with an inhibition constant (Ki) of about 10 nM. Inositol triphosphate (IP3) was accumulated more rapidly than inositol bisphosphate (IP2) in response to STA2. HPLC analysis indicated that inositol 1,4,5-triphosphate accumulated in the presence of STA2. STA2alone had no effect on the accumulation of IPs in membrane preparations but it potentiated the accumulation induced by GTPγS. [3H]SQ29548, a TXA2receptor antagonist, bound specifically to TXA2receptors, expressing a single binding site with a dissociation constant (Kd) of 10.9 nM. The competition curve for STA2inhibition of [3H]SQ29548 binding was shifted to the right and was steeper in the presence of GTPγS. Pertussis toxin (IAP) elicited ADP-ribosylation of 41KD protein but had no effect on the sensitivity to GTP of the STA2inhibition of SQ29548 binding or of STA2-induced accumulation of IPs. It is concluded from these results that the stimulation of TXA2receptors results in activation of phospholipase C via a GTP binding protein and that the protein is not a substrate for IAP.