Resistance-size, myogenic arteries regulate both systemic blood pressure and regional flow. L-type voltage- dependent calcium (Ca2+, CaV1.2) channels are the primary Ca2+ entry pathway in myocytes of resistance-size arteries and regulate physiological functions including contractility and gene expression. CaV1.2 channels are formed from multiple subunits, including a pore forming 11 and an auxiliary 124 and 2 which modulate channel properties. Despite the importance of vascular CaV1.2 channels, little is known regarding the functional significance of myocyte splice variants and auxiliary subunits. In hypertension there is an increase in arterial myocyte Cav1.2 currents, leading to an elevation in vascular contraction and blood pressure, but mechanisms mediating this pathological alteration are unclear. Similarly, there are few approaches to selectively target Cav1.2 channels to reduce vascular contractility. This proposal stems from preliminary data which suggest that myocytes of resistance-size cerebral arteries express a novel CaV1.2 11 subunit splice variant that is uniquely modulated by the auxiliary 124 subunit. Data also indicate that in hypertension, altered myocyte Cav1.2 channel regulation by 124 leads to an elevation in Cav1.2 currents and vasoconstriction. The overall goal of this application is to expand our knowledge of the molecular physiology of CaV1.2 channels in myocytes of resistance-size cerebral arteries and to study functional alterations that are associated with hypertension.
Three specific aims will be investigated.
Aim 1 will examine arterial myocyte CaV1.2 11 subunit splice variants in normotension and hypertension and test the hypothesis that molecular targeting of a myocyte-specific N-terminal variant causes vasodilation.
Aim 2 will investigate the hypothesis that 124 modulates myocyte CaV1.2 currents and that hypertension is associated with altered regulation, leading to a Cav1.2 current elevation and vasoconstriction.
Aim 3 will explore the hypothesis that in arterial myocytes, 124 is necessary for plasma membrane insertion of CaV1.2 11 subunits and that upregulation in hypertension leads to vasoconstriction. To investigate these aims, we will use a wide variety of techniques, including quantitative polymerase chain reaction, patch-clamp electrophysiology, laser-scanning confocal microscopy, Western blotting, RNA interference, intracellular Ca2+ measurements, and pressurized arterial diameter myography. These studies will improve knowledge of the molecular identity, subunit regulation, physiology, and pathophysiology of CaV1.2 channels that are expressed in myocytes of resistance-size arteries.
Project Narrative Voltage-dependent calcium (Ca2+) channels of the CaV1.2 family are the principal Ca2+ influx pathway in arterial smooth muscle cells, regulate a variety of physiological functions including contractility, and are upregulated in hypertension leading to vasoconstriction and elevated blood pressure. The molecular identity and associated functions of CaV1.2 channel subunits that are expressed in smooth muscle cells of arteries that regulate blood pressure and flow in normotension and hypertension is poorly understood. Our proposal will investigate the hypothesis that molecularly distinct CaV1.2 channels are expressed in arterial smooth muscle cells, and that the molecular composition of these channels is altered in hypertension, leading to vasoconstriction.
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