Mukhin Yurii V, Garnovskaya Maria N, Ullian Michael E, Raymond John R
Medical and Research Services of the Ralph H. Johnson Veterans Affairs Medical Center, Department of Medicine (Nephrology Division), Medical University of South Carolina, 96 Jonathan Lucas Street, Charleston, SC 29425, USA.
J Biol Chem. 2004 Jan 16;279(3):1845-52. doi: 10.1074/jbc.M304907200. Epub 2003 Nov 4.
The purposes of this study were to test 1) the relationship between two widely studied mitogenic effector pathways, and 2) the hypothesis that sodium-proton exchanger type 1 (NHE-1) is a regulator of extracellular signal-regulated protein kinase (ERK) activation in rat aortic smooth muscle (RASM) cells. Angiotensin II (Ang II) and 5-hydroxytryptamine (5-HT) stimulated both ERK and NHE-1 activities, with activation of NHE-1 preceding that of ERK. The concentration-response curves for 5-HT and Ang II were superimposable for both processes. Inhibition of NHE-1 with pharmacological agents or by isotonic replacement of sodium in the perfusate with choline or tetramethylammonium greatly attenuated ERK activation by 5-HT or Ang II. Similar maneuvers significantly attenuated 5-HT- or Ang II-mediated activation of MEK and Ras but not transphosphorylation of the epidermal growth factor (EGF) receptor. EGF receptor blockade attenuated ERK activation, but not NHE-1 activation by 5-HT and Ang II, suggesting that the EGF receptor and NHE-1 work in parallel to stimulate ERK activity in RASM cells, converging distal to the EGF receptor but at or above the level of Ras in the Ras-MEK-ERK pathway. Receptor-independent activation of NHE-1 by acute acid loading of RASM cells resulted in the rapid phosphorylation of ERK, which could be blocked by pharmacological inhibitors of NHE-1 or by isotonic replacement of sodium, closely linking the proton transport function of NHE-1 to ERK activation. These studies identify NHE as a new regulator of ERK activity in RASM cells.
1）两条广泛研究的促有丝分裂效应通路之间的关系；2）1型钠-质子交换体（NHE-1）是大鼠主动脉平滑肌（RASM）细胞中细胞外信号调节蛋白激酶（ERK）激活的调节因子这一假说。血管紧张素II（Ang II）和5-羟色胺（5-HT）刺激ERK和NHE-1的活性，NHE-1的激活先于ERK。5-HT和Ang II的浓度-反应曲线在这两个过程中是可叠加的。用药物制剂抑制NHE-1或用胆碱或四甲基铵等渗替代灌注液中的钠，可大大减弱5-HT或Ang II对ERK的激活。类似的操作可显著减弱5-HT或Ang II介导的MEK和Ras的激活，但不影响表皮生长因子（EGF）受体的转磷酸化。EGF受体阻断可减弱ERK的激活，但不影响5-HT和Ang II对NHE-1的激活，这表明EGF受体和NHE-1在RASM细胞中平行发挥作用以刺激ERK活性，在EGF受体远端汇聚，但在Ras-MEK-ERK通路中在Ras水平或其以上。通过急性酸负荷使RASM细胞非受体依赖性激活NHE-1可导致ERK快速磷酸化，这可被NHE-1的药理抑制剂或等渗替代钠所阻断，将NHE-1的质子转运功能与ERK激活紧密联系起来。这些研究确定NHE是RASM细胞中ERK活性的新调节因子。
