Mechanism of SSH1L Phosphatase Activation in VSMC: Role in Vascular Pathology

血管平滑肌细胞(VSMC)在体内的迁移主要是PDGF-p受体被血小板衍生生长因子(PDGF)激活的结果，导致血管成形术后再狭窄和动脉粥样硬化。尽管细胞迁移在不同的细胞类型和组织环境中涉及不同的机制，但这是一个普遍的过程，在所有情况下都涉及肌动蛋白细胞骨架的重塑。Cofilin是一种蛋白质，通过刺激肌动蛋白细丝的快速周转来调节肌动蛋白的动态。Cofilin被Slingshot磷酸酶SSH1L去磷酸化激活。然而，导致SSHIL激活的机制尚不清楚。我们的初步数据有力地表明，NADPH氧化酶-1(NoXL)衍生的活性氧物种(ROS)参与了SSH1L的激活。在这些观察的基础上，将调查三个具体目标。首先，将确定NOX 1衍生的ROS在SSH1L磷酸酶激活或亚细胞定位变化中的作用。其次，我们将描述在ROS诱导的VSMC中SSHIL激活的上游信号通路；特别是我们将重点关注调节SSHIL活性的蛋白质伙伴的参与。最后，我们将研究SSH1L在血管内膜形成过程中VSMC迁移中的作用。这些研究将为控制血管平滑肌细胞迁移的机制提供重要的洞察力，并可能有助于确定血管疾病的新治疗靶点。综上所述，在本研究中，我们将从分子水平探讨PDGF激活SSHIL的ROS依赖机制在VSMC中的作用，并评估这一激活途径在体内的影响。这些研究将有助于确定动脉粥样硬化和再狭窄等涉及VSMC迁移失调的病理疾病的潜在治疗靶点。

Vascular smooth muscle cell (VSMC) migration, which in vivo is primarily the consequence of activation of the PDGF-p receptor by platelet-derived growth factor (PDGF), contributes to post-angioplasty restenosis and atherosclerosis. Although cell migration involves different mechanisms in different cell types and tissue environments, it is a universal process that in all cases involves remodelling of actin cytoskeleton. Cofilin is a protein that regulates actin dynamics by stimulating rapid turnover of actin filaments. Cofilin is activated by dephosphorylation by the Slingshot phosphatase SSH1L. However, the mechanisms leading to SSHIL activation are unknown. Our preliminary data strongly suggest that NADPH oxidase-1 (Noxl)-derived reactive oxygen species (ROS) participate in SSH1L activation. Based on these observations, three specific aims will be investigated. First, the role of Nox 1-derived ROS in SSH1L phosphatase activation or changes in subcellular localization will be determined. Second, we will characterize the upstream signaling pathways responsible for ROS-induced SSHIL activation in VSMC; particularly, we will focus on the participation of protein partners which regulate SSHIL activity. Finally, the role of SSH1L in VSMC migration during neointimal formation will be investigated. These studies will provide important insight into the mechanisms controlling vascular smooth muscle cell migration, and may help to identify new therapeutic targets for vascular disease. In summary, in this proposal we will explore the role of ROS-dependent mechanisms of SSHIL activation by PDGF at the molecular level in VSMC, and we will evaluate the impact of this activation pathway in vivo. These studies will help to identify potential therapeutic targets for pathologies such as atherosclerosis and restenosis that involve dysregulation of VSMC migration.