Vasoregulation by IP3 receptor coupling to TRPC channels

描述(申请人提供)：动脉直径，全身血压和器官血流的主要调节器，由动脉肌细胞收缩能力的变化来调节。动脉肌细胞的收缩状态由几个局部和整体细胞内钙([Ca~(2+)]i)信号决定。肌醇1，4，5-三磷酸(IPS)是磷脂酶C产生的第二信使，对钙信号和直径的调节知之甚少。传统的观点认为，IPS通过刺激肌浆网(SR)钙离子的释放而收缩动脉。我们最近发表的数据表明，IPS诱导的血管收缩是一种新的机制，这种收缩不依赖于SRCa+的释放，而是通过IPS受体(IP3R)和依赖于典型瞬时受体电位(TRPC)3的阳离子电流(ICAT)的激活而发生的。但是，IP3R激活刺激动脉肌细胞TRPC通道以调节动脉内径的机制尚不清楚。初步数据表明，心肌细胞IPSRs和TRPC3通道之间的物理偶联调节IPS诱导的血管收缩。数据还表明，动脉肌细胞小窝促进了IP3R-TRPC通道的血管调节机制。这一假设的中心假设是，在大脑动脉肌细胞中，小窝促进TRPC3通道与IPSRs偶联，介导血管收缩和IPS引起的膜去极化、电压依赖性钙通道激活、[Ca2+]i升高和收缩。本提案将研究3个特定的目标：目的1将验证在大脑动脉肌细胞中，IP3R到TRPC3通道的物理偶联是IPS诱导的ICAT激活所必需的。目的2将验证IP3R到TRPC3偶联介导IPS诱导的脑血管膜去极化、[Ca~(2+)]i升高和收缩的假设。目的3验证动脉肌细胞小窝介导TRPC3通道与IPSR的物理和功能偶联的假说。研究这些目标的实验将整合在分子、细胞和完整组织水平上进行的技术，包括钙成像、FRET、电生理学、加压动脉肌图和基因抑制。相关性(见说明)：调节血压和血流的机制还不完全清楚。动脉收缩能力的改变与血管疾病有关，包括中风和高血压。这一提议将增强我们对调节动脉收缩能力的新信号事件的了解，并最终将导致对血管疾病中发生的变化的更好的洞察。(摘要结束)

DESCRIPTION (provided by applicant): Arterial diameter, a principal modulator of systemic blood pressure and organ blood flow is regulated by changes in the contractility of arterial myocytes. The contractile status of arterial myocytes is determined by several local and global intracellular calcium([Ca2+]i) signals. Ca2+ signal and diameter regulation byinositol 1,4,5-trisphophate (IPS), a phospholipase C-generated second messenger is poorly understood. The conventional view has been that IPS constricts arteries by stimulatingsarcoplasmic reticulum(SR) Ca2+ release in myocytes. Our recently published data indicateda novel mechanism of IPS-induced vasoconstriction that occurred independentlyof SRCa2+ release, and via IPS receptor (IP3R)-and canonicaltransient receptor potential (TRPC) 3-dependent cation current (ICat) activation.However, mechanisms by which IP3R activation stimulates TRPC channelsin arterial myocytes to regulate arterial diameter are unclear. Preliminary data suggest that physical couplingbetween myocyte IPSRs and TRPC3 channels regulates IPS-induced vasoconstriction. Data also indicate that arterial myocyte caveolae facilitate this IP3R-TRPCchannel vasoregulatory mechanism. The central hypothesis ofthis proposal is that in cerebral artery myocytes, caveolae facilitate TRPC3 channel couplingwith IPSRs to mediate vasoconstrictor and IPS-induced membrane depolarization, voltage-dependent Ca2+ channel activation, [Ca2+]i elevation, and contraction. This proposal will investigate 3 specific aims: Aim 1 will test the hypothesis that in cerebral artery myocytes, IP3R to TRPC3 channel physical couplingis required for IPS-inducedICat activation.Aim 2 will test the hypothesis that IP3R to TRPC3 couplingmediates IPS-induced membrane depolarization, [Ca2+]i elevation, and constriction in cerebral arteries. Aim 3 will examine the hypothesis that arterial myocyte caveolae mediate physical and functional coupling of TRPC3 channelsto IPSRs. Experiments to study these aims will integrate techniques performed at molecular, cellular,and intact tissue levels, including Ca2+ imaging,FRET, electrophysiology, pressurized artery myography, and gene suppression. RELEVANCE (See instructions): Mechanisms that regulate blood pressure and flow are incompletely understood. Alterations in arterial contractility are associated with vascular diseases, including stroke and hypertension. This proposal will enhance our knowledge of a novel signaling event that modulates arterial contractility, and will ultimately lead to better insights into alterations that occur in vascular disease. (End of Abstract)