Miggin Sinead M, Kinsella B Therese
Department of Biochemistry, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland.
Mol Pharmacol. 2002 Apr;61(4):817-31. doi: 10.1124/mol.61.4.817.
Thromboxane A(2) (TXA(2)) stimulates mitogenic growth of vascular smooth muscle. In humans, TXA(2) signals through two TXA(2) receptor (TP) isoforms, termed TPalpha and TPbeta. To investigate the mechanism of TXA(2)-mediated mitogenesis, regulation of extracellular signal-regulated kinase (ERK) signaling was examined in human embryonic kidney 293 cells stably overexpressing the individual TP isoforms. The TXA(2) mimetic 9,11-dideoxy-9alpha,11alpha-methano epoxy prostaglandin F(2alpha) (U46619) elicited concentration- and time-dependent activation of ERK1 and -2 through both TPs with maximal TPalpha- and TPbeta-mediated ERK activation observed after 10 and 5 min, respectively. U46619-mediated ERK activation was inhibited by the TP antagonist [1S-[1alpha,2beta-(5Z)-3beta,4alpha-]]-7-[3-[[2-(phenylamino)carbonyl]hydrazine] methyl]-7-oxabicyclo[-2,2,1-]hept-2yl]-5-heptenoic acid (SQ29,548), and by the mitogen-activated protein kinase kinase inhibitor 2'-amino-3'-methoxyflavone (PD 98059). Although ERK activation through TPalpha was dependent on 2-[1-(dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide (GF 109203X)-sensitive protein kinase (PK) Cs, ERK activation through TPbeta was only partially dependent on PKCs. ERK activation through both TPalpha and TPbeta was dependent on PKA and phosphoinositide 3-kinase (PI3K) class 1(A), but not class 1(B), and was modulated by Harvey-Ras, A-Raf, c-Raf, and Rap1B/B-Raf and also involved transactivation of the epidermal growth factor receptor. Additionally, PKB/Akt was activated through TPalpha and TPbeta in a PI3K-dependent manner. In conclusion, we have defined the key components of TXA(2)-mediated ERK signaling and have established that both TPalpha and TPbeta are involved. TXA(2)-mediated ERK activation through the TPs is a complex event involving PKC-, PKA-, and PI3K-dependent mechanisms in addition to transactivation of the EGF receptor. TPalpha and TPbeta mediate ERK activation through similar mechanisms, although the time frame for maximal ERK activation and PKC dependence differs.
血栓素A2（TXA2）刺激血管平滑肌的有丝分裂生长。在人类中，TXA2通过两种TXA2受体（TP）亚型发出信号，分别称为TPα和TPβ。为了研究TXA2介导的有丝分裂发生机制，我们在稳定过表达单个TP亚型的人胚肾293细胞中检测了细胞外信号调节激酶（ERK）信号的调节情况。TXA2模拟物9,11-二脱氧-9α,11α-甲氧基环氧前列腺素F2α（U46619）通过两种TP引发ERK1和ERK2的浓度和时间依赖性激活，分别在10分钟和5分钟后观察到TPα和TPβ介导的ERK激活达到最大值。U46619介导的ERK激活被TP拮抗剂[1S-[1α,2β-(5Z)-3β,4α-]]-7-[3-[[2-(苯氨基)羰基]肼]甲基]-7-氧杂双环[-2,2,1-]庚-2-基]-5-庚烯酸（SQ29548）以及丝裂原活化蛋白激酶激酶抑制剂2'-氨基-3'-甲氧基黄酮（PD 98059）抑制。虽然通过TPα的ERK激活依赖于2-[1-(二甲基氨基丙基)-1H-吲哚-3-基]-3-(1H-吲哚-3-基)-马来酰亚胺（GF 109203X）敏感的蛋白激酶（PK）C，但通过TPβ的ERK激活仅部分依赖于PKC。通过TPα和TPβ的ERK激活均依赖于PKA和1（A）类磷酸肌醇3激酶（PI3K），而非1（B）类，并且受到哈维-拉斯（Harvey-Ras）、A-Raf、c-Raf和Rap1B/B-Raf的调节，还涉及表皮生长因子受体的反式激活。此外，蛋白激酶B/蛋白激酶B（PKB/Akt）通过TPα和TPβ以PI3K依赖的方式被激活。总之，我们确定了TXA2介导的ERK信号的关键组成部分，并证实TPα和TPβ均参与其中。TXA2通过TP介导的ERK激活是一个复杂的事件，除了表皮生长因子受体的反式激活外，还涉及PKC、PKA和PI3K依赖的机制。TPα和TPβ通过类似的机制介导ERK激活，尽管ERK激活最大值的时间框架和PKC依赖性有所不同。
