Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
J Biol Chem. 2013 Jul 26;288(30):22150-62. doi: 10.1074/jbc.M113.454082. Epub 2013 Jun 4.
Recent literature suggests that cyclin-dependent kinases (CDKs) mediate cell migration. However, the mechanisms were not known. Therefore, the objective of this study is to test whether cyclin/CDKs activate Pak1, an effector of Rac1, whose involvement in the modulation of cell migration and proliferation is well established. Monocyte chemotactic protein 1 (MCP1) induced Pak1 phosphorylation/activation in human aortic smooth muscle cells (HASMCs) in a delayed time-dependent manner. MCP1 also stimulated F-actin stress fiber formation in a delayed manner in HASMCs, as well as the migration and proliferation of these cells. Inhibition of Pak1 suppressed MCP1-induced HASMC F-actin stress fiber formation, migration, and proliferation. MCP1 induced cyclin D1 expression as well as CDK6 and CDK4 activities, and these effects were dependent on activation of NFATc1. Depletion of NFATc1, cyclin D1, CDK6, or CDK4 levels attenuated MCP1-induced Pak1 phosphorylation/activation and resulted in decreased HASMC F-actin stress fiber formation, migration, and proliferation. CDK4, which appeared to be activated downstream of CDK6, formed a complex with Pak1 in response to MCP1. MCP1 also activated Rac1 in a time-dependent manner, and depletion/inhibition of its levels/activation abrogated MCP1-induced NFATc1-cyclin D1-CDK6-CDK4-Pak1 signaling and, thereby, decreased HASMC F-actin stress fiber formation, migration, and proliferation. In addition, smooth muscle-specific deletion of NFATc1 led to decreased cyclin D1 expression and CDK6, CDK4, and Pak1 activities, resulting in reduced neointima formation in response to injury. Thus, these observations reveal that Pak1 is a downstream effector of CDK4 and Rac1-dependent, NFATc1-mediated cyclin D1 expression and CDK6 activity mediate this effect. In addition, smooth muscle-specific deletion of NFATc1 prevented the capacity of vascular smooth muscle cells for MCP-1-induced activation of the cyclin D1-CDK6-CDK4-Pak1 signaling axis, affecting their migration and proliferation in vitro and injury-induced neointima formation in vivo.
最近的文献表明，细胞周期蛋白依赖性激酶 (CDKs) 介导细胞迁移。然而，其机制尚不清楚。因此，本研究的目的是测试细胞周期蛋白/CDKs 是否激活 Rac1 的效应物 Pak1，Rac1 参与细胞迁移和增殖的调节已得到充分证实。单核细胞趋化蛋白 1 (MCP1) 以延迟的时间依赖性方式诱导人主动脉平滑肌细胞 (HASMC) 中 Pak1 的磷酸化/激活。MCP1 还以延迟的方式刺激 HASMC 中 F-肌动蛋白应力纤维的形成，以及这些细胞的迁移和增殖。Pak1 的抑制抑制了 MCP1 诱导的 HASMC F-肌动蛋白应力纤维形成、迁移和增殖。MCP1 诱导 cyclin D1 表达以及 CDK6 和 CDK4 的活性，这些作用依赖于 NFATc1 的激活。NFATc1、cyclin D1、CDK6 或 CDK4 水平的耗竭减弱了 MCP1 诱导的 Pak1 磷酸化/激活，并导致 HASMC F-肌动蛋白应力纤维形成、迁移和增殖减少。CDK4 似乎在 CDK6 下游被激活，它与 Pak1 形成复合物以响应 MCP1。MCP1 还以时间依赖性方式激活 Rac1，并且其水平/激活的耗竭/抑制消除了 MCP1 诱导的 NFATc1-cyclin D1-CDK6-CDK4-Pak1 信号传导，从而减少 HASMC F-肌动蛋白应力纤维形成、迁移和增殖。此外，平滑肌特异性 NFATc1 的缺失导致 cyclin D1 表达和 CDK6、CDK4 和 Pak1 活性降低，从而导致对损伤的新生内膜形成减少。因此，这些观察结果表明，Pak1 是 CDK4 和 Rac1 依赖性的下游效应物，NFATc1 介导的 cyclin D1 表达和 CDK6 活性介导了这种作用。此外，平滑肌特异性 NFATc1 的缺失防止了血管平滑肌细胞对 MCP-1 诱导的 cyclin D1-CDK6-CDK4-Pak1 信号轴的激活能力，影响其体外迁移和增殖以及体内损伤诱导的新生内膜形成。
