The Role of CIC-6 in Vascular Control of Blood Pressure

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PROJECT SUMMARY Nearly half of the US adult population has hypertension, which puts them at increased risk for stroke, vascular damage, heart attack, heart failure, and kidney disease. Recent genome-wide association studies have linked a number of mutations in the gene, CLCN6, to reduced hypertension and stroke risk. CLCN6 encodes the voltage-sensitive chloride channel 6 (ClC-6). To date, very little is known of about the function ClC-6, or its role in blood pressure homeostasis. The overall goal of this proposal is to establish the physiological and molecular roles of ClC-6 on vascular smooth muscle cell (VSMC) function and blood pressure. Mentored Phase: Preliminary data have demonstrated that ClC-6 is expressed in the Golgi apparatus of VSMCs. I hypothesize that ClC-6 activity in VSMCs regulates luminal Golgi Ca2+ stores by providing a charge balance for Ca2+ uptake, thereby maintaining membrane electroneutrality. This occurs through an association with the Golgi-specific Ca2+-ATPase, SPCA1, and loss of ClC-6 reduces Golgi Ca2+ stores and signaling, which alters VSMC contractility. Specific Aim 1. Establish the role of ClC-6 on Golgi Ca2+ handling in VSMCs. I will utilize planar lipid bilayer electrophysiology and sophisticated Ca2+ imaging to determine ClC-6 chloride channel properties and their impact on the Ca2+ storage capacity of the Golgi. Furthermore, these experiments will provide the first evidence of the role of Golgi-specific Ca2+ release in VSMC Ca2+ handling in response to vasocontraction and dilation stimuli, which has never before been examined. Independent Phase: This phase of the project will develop an independent line of investigation into the molecular effects of ClC-6 on VSMC function. Insight gained from these experiments will further explain the physiological mechanism underlying ClC-6 regulation of blood pressure control. My preliminary data have established that ClC-6 prevents or slows large artery vessel stiffening during development of hypertension. I will further examine the effect of ClC-6 on cellular proliferation, migration, apoptosis, and extracellular matrix protein deposition in normotensive and hypertensive vessels. I hypothesize that loss of ClC-6 will reduce extracellular matrix protein secretion and slow cell proliferation, thereby reducing hypertension induced fibrosis and media thickening. These changes will result in abrogated arterial stiffening and vessel remodeling, and reduce peripheral vascular resistance, providing a rationale for how ClC-6 moderates blood pressure. Specific Aim 2. Elucidate the influence of ClC-6 on vascular stiffness and vessel remodeling during hypertension. Experiments to address this hypothesis will include a diverse range of experiments, including pulse-wave velocity measurements, histological analyses, migration assays, myography, TUNNEL and BrdU assays, and transcriptomic analysis. These studies will inform our understanding of the protein's function by defining the role of this channel in vasculature at the molecular, cellular, and systemic levels.