Department of Cell Physiology and Pharmacology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 9HN, UK.
Cardiovasc Res. 2011 Sep 1;91(4):694-702. doi: 10.1093/cvr/cvr137. Epub 2011 May 23.
Membrane potential is a key determinant of vascular tone and many vasodilators act through the modulation of ion channel currents [e.g. the ATP-sensitive potassium channel (K(ATP))] involved in setting the membrane potential. Adenylyl cyclase (AC) isoenzymes are potentially important intermediaries in such vasodilator signalling pathways. Vascular smooth muscle cells (VSMCs) express multiple AC isoenzymes, but the reason for such redundancy is unknown. We investigated which of these isoenzymes are involved in vasodilator signalling and regulation of vascular ion channels important in modulating membrane potential.
AC isoenzymes were selectively depleted (by >75%) by transfection of cultured VSMCs with selective short interfering RNA sequences. AC6 was the predominant isoenzyme involved in vasodilator-mediated cAMP accumulation in VSMCs, accounting for ∼60% of the total response to β-adrenoceptor (β-AR) stimulation. AC3 played a minor role in β-AR signalling, whereas AC5 made no significant contribution. AC6 was also the principal isoenzyme involved in β-AR-mediated protein kinase A (PKA) signalling (determined using the fluorescent biosensor for PKA activity, AKAR3) and the substantial β-AR/PKA-dependent enhancement of K(ATP) current. K(ATP) current was shown to play a vital role in setting the resting membrane potential and in mediating the hyperpolarization observed upon β-AR stimulation.
AC6, but not the closely related AC5, plays a principal role in vasodilator signalling and regulation of the membrane potential in VSMCs. These findings identify AC6 as a vital component in the vasodilatory apparatus central to the control of blood pressure.
膜电位是血管张力的关键决定因素，许多血管扩张剂通过调节参与设定膜电位的离子通道电流（例如，ATP 敏感性钾通道（KATP））起作用。腺苷酸环化酶（AC）同工酶可能是这种血管扩张剂信号通路中的重要中间介质。血管平滑肌细胞（VSMCs）表达多种 AC 同工酶，但这种冗余的原因尚不清楚。我们研究了这些同工酶中的哪一种参与血管扩张剂信号转导以及调节对膜电位有重要调节作用的血管离子通道。
通过用选择性短干扰 RNA 序列转染培养的 VSMCs，选择性地耗尽了 AC 同工酶（>75%）。AC6 是参与 VSMCs 中血管扩张剂介导的 cAMP 积累的主要同工酶，占β-肾上腺素能受体（β-AR）刺激的总反应的约 60%。AC3 在β-AR 信号转导中起次要作用，而 AC5 没有显著贡献。AC6 也是β-AR 介导的蛋白激酶 A（PKA）信号转导（使用 PKA 活性的荧光生物传感器 AKAR3 确定）和β-AR/PKA 依赖性增强 KATP 电流的主要同工酶。已经表明，KATP 电流在设定静息膜电位以及介导β-AR 刺激时观察到的超极化中起着至关重要的作用。
AC6，但不是密切相关的 AC5，在 VSMCs 中的血管扩张剂信号转导和膜电位调节中起主要作用。这些发现确定了 AC6 是血管舒张装置中的重要组成部分，该装置是控制血压的核心。
