Regulation of cerebral vascular smooth muscle by local calcium signals

脑动脉的功能是为大脑提供充足的血液供应。为了实现这一功能，脑动脉必须根据生理刺激改变其直径。动脉直径由血管平滑肌细胞（VSMCs）的收缩状态调节，而血管平滑肌细胞是由电压依赖性Ca2+通道（VDCCs）的活性调节的。目前的观点是，vdcc通过Ca2+的直接贡献或间接收缩脑动脉，通过肌浆网中的ryanodine受体（RYRs）激活Ca2+释放，称为“Ca2+火花”，通过激活附近的Ca2+敏感钾（K/ca）通道使VSMCs超极化，该通道关闭vdcc，减少细胞Ca2+，从而扩张脑动脉。这一发现强调了局部Ca2+信号的位置、频率和幅度在VSMCs功能中的重要性。PI和合作者最近的工作表明，像福斯克林和一氧化氮（NO）这样的血管扩张剂分别通过蛋白激酶A和G起作用，以一种基本的、以前未被怀疑的方式改变了vdcs和RyRs之间的通信。这项合作提议的目标是测试蛋白激酶A和G的激活放松脑动脉的假设，因为它们使vdcc的局部Ca2+信号激活K/Ca通道，并测试这一假设，PI和合作者将进行一系列互补实验，包括使用电生理学，共聚焦显微镜和分子技术在他们的实验室。这项建议有三个具体目标。1）. 了解VDCC和RyR之间的通信，以及PKA对其进行调制。2)了解VDCC和RyR之间的通信，以及PKG对其进行调制。了解SR蛋白磷蛋白在VDCCs与RyRs通讯调控中的作用。当PI将专注于提案中涉及游离VSMCs和基因转移的部分时，合作者将专注于涉及完整脑动脉的实验。这种价值的划分将使双方研究人员的互补专业知识能够以互利的方式得到应用。这项工作将为脑动脉张力调节机制提供新的基础信息，并为高血压、中风、脑血管痉挛和偏头痛等临床疾病的治疗提供新的见解。

The function of cerebral arteries is to provide an adequate supply of blood to the brain. TO achieve this function cerebral arteries must alter their diameter in response to physiological stimuli. Arterial diameter is regulated by the contractile state of vascular smooth muscle cells (VSMCs), which is regulated by the activity of voltage-dependent Ca2+ channels (VDCCs). The current view is that VDCCs constrict cerebral arteries through a direct contribution of Ca2+ or indirectly, by activating Ca2+ release through ryanodine receptors (RYRs) in the sarcoplasmic reticulum RyRs, called "Ca2+ sparks", hyperpolarize VSMCs by activating nearby Ca2+-sensitive potassium (K/ca) channels which close VDCCs, reduces cellular Ca2+ and thus dilates cerebral arteries. This findings underscore the importance of the location, frequency and amplitude of local Ca2+ signals in the function of VSMCs. Recent work by the PI and the collaborator suggest that vasodilators like forskolin and nitric oxide (NO) acting, respectively, through protein kinase A and G alter in a fundamental and previously unsuspected way the communication between VDCCs and RyRs. The goal of this collaborative proposal is to test the hypothesis that activation of protein kinase A and G relax cerebral arteries because they enable local Ca2+ signals from VDCCs to activate K/Ca channels and test this hypothesis the PI and collaborator will perform a series of complementary experiments that involve the use of electrophysiological, confocal microscopy and molecular techniques available in their laboratories. This proposal has three specific aims. 1). To understand the communication between VDCC and RyR, and its modulation by PKA. 2) To understand the communication between VDCC and RyR, and its modulation by PKG. 3). To understand the role of the SR protein phospholamban in the regulation of the communication between VDCCs and RyRs. While the PI will focus on the portions of the proposal involving dissociated VSMCs and gene- transfer, the collaborator will focus on experiments involving intact cerebral arteries. This division of worth will allow the complementary expertise of both investigators ti be applied in a mutually beneficial way. The proposed work should provide new fundamental information on the mechanisms that regulate tone in cerebral arteries and provide insights in the treatment of clinical conditions such as hypertension, stroke, cerebral vasospasm and migraine.