Cooperative regulation of p70S6 kinase by receptor tyrosine kinases and g protein-coupled receptors augments airway smooth muscle growth
Cooperative regulation of p70S6 kinase by receptor tyrosine kinases and g protein-coupled receptors augments airway smooth muscle growth
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DOI：
10.1021/bi0510734
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发表时间：
2005-11-08
期刊：
影响因子：
2.9
通讯作者：
Penn, RB
中科院分区：
文献类型：
--
作者：
Billington, CK;Kong, KC;Penn, RB
我们先前已经证明，受体酪氨酸激酶和某些G蛋白偶联受体(GPCRs)的同时激活可以促进气道平滑肌细胞(ASM)增殖率的协同增加。在这里，我们阐明了p70S6激酶(P70S6K)作为受体酪氨酸激酶和GPCR信号的整合者的作用，通过证明特定的p70S6K磷酸化位点从GPCRs获得不同的调节输入，促进对有丝分裂至关重要的持续的激酶活性，从而增强ASM DNA合成。用EGF和凝血酶长期刺激ASM细胞后，T389残基的p70S6K磷酸化水平显著高于相加效应，而T229和T421/S424的磷酸化水平显著升高，但幅度较小。凝血酶的增强作用可能与p42/p44MAPK的激活无关，因为选择性抑制凝血酶刺激的p42/p44不能改变协同的p70S6K T389的磷酸化、p70S6K的活性或ASM[H-3]胸腺嘧啶核苷的掺入。凝血酶刺激Akt磷酸化水平持续升高，并增强EGF刺激的Akt磷酸化。凝血酶对Akt/p70S6K磷酸化和[3 H]胸腺嘧啶核苷掺入的协同作用均被异源表达的Gβγ受体减弱。这些数据表明，依赖于PI3K的T389/T229的磷酸化限制了EGF对晚期p70S6K的激活，并参与了GPCRs对p70S6K活性和细胞生长的协同作用。
We have previously demonstrated that concomitant activation of receptor tyrosine kinases and certain G protein-coupled receptors (GPCRs) can promote a synergistic increase in the rate of airway smooth muscle cell (ASM) proliferation. Here we clarify the role of p70S6 kinase (p70S6K) as an integrator of receptor tyrosine kinase and GPCR signaling that augments ASM DNA synthesis by demonstrating that specific p70S6K phosphorylation sites receive distinct regulatory input from GPCRs that promotes sustained kinase activity critical to mitogenesis. Prolonged stimulation of ASM cells with EGF and thrombin induced a greater than additive effect in levels of p70S6K phosphorylated at residue T389, whereas a significant but more modest increase in the level of T229 and T421/S424 phosphorylation was also observed. The augmenting effects of thrombin could be dissociated from p42/p44 MAPK activation, as selective inhibition of thrombin-stimulated p42/p44 failed to alter the profile of cooperative p70S6K T389 phosphorylation, p70S6K kinase activity, or ASM [H-3]thymidine incorporation. Thrombin stimulated a sustained increase in the level of Akt phosphorylation and also augmented EGF-stimulated Akt phosphorylation. The cooperative effects of thrombin on Akt/p70S6K phosphorylation and [3H]thymidine incorporation were all attenuated by heterologous expression of G beta gamma sequestrants. These data suggest that PI3K-dependent T389/T229 phosphorylation is limiting in late-phase p70S6K activation by EGF and contributes to the cooperative effect of GPCRs on p70S6K activity and cell growth.