Regional blood flow to the brain is controlled by small (resistance-size) cerebral arteries and arterioles that supply neurons and other brain cells with oxygen and nutrients. Ion channels play a crucial role in the regulation of membrane potential which in turn controls arterial contractility. Intravascular pressure stimulates depolarization of vascular smooth muscle that elevates Ca2+ leading to vasoconstriction. Intravascular pressure-induced membrane depolarization also activates BK channels leading to membrane hyperpolarization and vasodilation and serves as a feedback regulatory mechanism to the pressure-induced vasoconstriction. BK channels are formed from pore-forming alpha subunits and auxiliary beta subunits. Mechanisms that control the number of functional ion channels on the plasma membrane are poorly understood. This application stems from exciting data that we published recently and also novel preliminary data indicating that myocyte plasma membrane BK channel subunit composition is rapidly modulated by different vasoregulatory stimuli to control arterial contractility. Our preliminary data indicates that, 1. Membrane depolarization stimulates rapid rab11A-dependent beta1 surface trafficking, 2. Depolarization activates extracellular Ca2+ entry and rho kinase to induce beta1 surface trafficking, whereas, nitric oxide (NO) activates PKG and Ca2+ sparks to induce beta1 surface trafficking, 3. Surface trafficking of beta1 elevates BK channel activity, Ca2+ sensitivity and activation by lithocholate, a beta1 subunit ligand and 4. Beta1 surface trafficking and BK channel activity in response to depolarization and NO are significantly inhibited in stroke-prone hypertensive rats (SPSHR) when compared to WKY rats. Techniques that will be used include, surface biotinylation, immuno-Fluorescence Resonance Energy Transfer (Immuno-FRET) microscopy, western blotting, gene knockdown, patch-clamp electrophysiology, high-speed confocal Ca2+ imaging, membrane potential measurements and pressurized artery diameter measurements. This work aims to identify novel signaling pathways that modulate BK channel activity and demonstrate the significance of rapid ion channel subunit trafficking in vasoregulation.
|Program type||Scientist Development Grant|
|Effective start/end date||01/01/2015 → 12/31/2018|