New Signaling Networks in Vascular Smooth Muscle

摘要： 这项提议的重点是我们发现了由p90核糖体S6激酶介导的新的信号通路 (RSK2)调节血管平滑肌(VSM)介导的血管阻力、肌张力和血液 理性地认为，结果有可能提供新的治疗目标。大鼠的肌源性反应 小阻力动脉是保护下游小动脉和毛细血管免受气压创伤的关键 血管内压的过度变化。我们对控制信号通路的理解 肌源性和激动剂介导的血管收缩、血管阻力和血压稳态 这项建议解决了我们知识库中的这一差距。我们的总体目标是确定 RSK2在血管生理学和病理生理学中的作用 透视。我们的中心假设是RSK2激酶介导了一个新的通路网络，导致 肌源性压力和激动剂对VSM收缩的调节。这一假设是基于 初步数据表明，阻力动脉中有三个RSK2靶点，它们增强了收缩状态：(1) RLC20，导致肌球蛋白跨桥功能的典型激活的直接增强；(2)NHE-1 Na+/H+交换器，其磷酸化有助于与增加相关的PHI增加 胞内[Ca~(2+)]，从而增强MLCK介导的途径；和(3)两个RhoA特异性核苷酸 交换因素，对RhoA介导的途径具有潜在的调控影响。我们的初步数据也 提示RSK2信号对最大肌力的贡献约为20%，来自RSK2-/-小鼠的动脉 或使用RSK抑制剂治疗后，血管扩张更明显，肌张力和RLC20磷酸化降低， 与野生型小鼠相比，RSK2-/-小鼠的血压更低。我们假设这是非正统的 RSK2途径与典型的钙/MLCK和RhoA/ROCK的钙敏化增强和交叉对话 调节血管收缩和基础血压的途径。以下目标验证了我们的假设：目标1： 确定RSK2如何在对灌流压力和激动剂的反应中促进VSM收缩 重点关注选定的磷酸化靶点，即RLC20、NHE-1和RhoGEF。目标2：评估以下项目的贡献 RSK2对血压动态平衡的影响。预计结果将建立并添加一个新的RSK2介导的 信号网络到规范的MLCK和RhoA/ROCK信号通路，调节VSM音调和 血管收缩，并为血管壁收缩病理提供可能的新治疗靶点。

Abstract: This proposal focuses on our discovery of new signaling pathways mediated by the p90 ribosomal S6 kinase (RSK2) that regulate vascular smooth muscle (VSM) mediated vascular resistance, myogenic tone and blood flow with the rational that outcomes have potential to deliver new therapeutic targets. The myogenic response of small resistance arteries is critical for protection of downstream arterioles and capillaries against barotrauma due to excessive changes in intravascular pressure. Our understanding of the signaling pathways that control myogenic and agonist-mediated vasoconstriction, vascular resistance and blood pressure homeostasis are incomplete and this proposal addresses this gap in our knowledge base. Our overall objective is to determine the contribution of RSK2 to vascular physiology and pathophysiology from a mechanistic and functional perspective. Our central hypothesis is that RSK2 kinase mediates a novel network of pathways that result in regulation of VSM contraction in response to myogenic pressure and to agonists. This hypothesis is based on preliminary data identifying three RSK2 targets in resistance arteries which potentiate the contractile state: (1) RLC20, leading to direct augmentation of the canonical activation of myosin cross-bridge function; (2) NHE-1 Na+/H+ exchanger, the phosphorylation of which contributes to an increase in pHi associated with an increase in cytosolic [Ca2+], thereby potentiating the MLCK-mediated pathway; and (3) two RhoA-specific nucleotide exchange factors, with potential regulatory impact on the RhoA-mediated pathway. Our preliminary data also suggest that RSK2 signaling contributes ~20% of maximal myogenic force and that arteries from a Rsk2-/- mouse or treated with RSK inhibitors are more dilated, have reduced myogenic tone and RLC20 phosphorylation and that Rsk2-/- mice have lower blood pressure compared to wild-type mice. We hypothesize that this non-canonical RSK2 pathway augments and cross talks with the canonical Ca2+/MLCK and RhoA/ROCK Ca2+-sensitization pathways to regulate vasoconstriction and basal BP. The following aims test our hypotheses: Aim 1: To determine how RSK2 contributes to VSM contraction in response to perfusion pressure and agonists, with a focus on select phosphorylation targets, i.e. RLC20, NHE-1 and RhoGEFs. Aim 2: To assess the contribution of RSK2 to blood pressure homeostasis. Outcomes are expected to establish and add a new RSK2 mediated signaling network to the canonical MLCK and RhoA/ROCK signaling pathways regulating VSM tone and vasoconstriction and to provide possible new therapeutic targets for contractile pathologies of the vessel wall.