The mechanism of cardio-protection from a sulfonylurea receptor isoform 2 splice variant (SUR2A-55) and its role in regulating ROMK activity, the putative mitochondrial ATP sensitive potassium channel

点击翻译按钮获取中文摘要

Candidate: I am a staff cardiologist at the William S. Middleton Memorial VA and Assistant Professor of Medicine at the University of Wisconsin School of Medicine and Public Health. I obtained my MD from Northwestern University and completed internal medicine residency at Johns Hopkins Hospital and cardiology fellowship at the University of Pittsburgh. During my fellowship training I dedicated additional time in the laboratory of Dr. Ferhaan Ahmad to study mechanisms of genetic cardiomyopathies, which eventually led to the study of cardioprotective mechanisms in ischemia reperfusion injury due to my clinical interest in interventional cardiology. I was recruited to the William S. Middleton Memorial VA and University of Wisconsin to provide increased interventional cardiology coverage to Veteran patients but to also continue my work in cardioprotection with start-up funds, institutional mentorship and laboratory resources. Research Project: Activation of mitochondrial K+ flux confers cardioprotection in models of ischemic injury. Of the potential channels that modulate K+ flux, the putative mitochondrial ATP-sensitive potassium channel (mitoKATP) is most closely related to cardioprotection. However the molecular identity of mitoKATP is unknown and represents a critical gap in knowledge to discover therapies that target the mitochondrial K+ cycle. Prior studies and my preliminary data provide evidence for a short 55 kDa splice variant of the sulfonylurea receptor 2A (SUR2A-55) that targets mitochondria, regulates mitoKATP activity, enables increased glucose metabolism and protects the heart from ischemia-reperfusion injury when overexpressed. In addition, prior studies and my preliminary data suggest a role for the renal outer medullary K+ channel (ROMK) in mitochondrial ATP sensitive K+ transport and cardioprotection. In this proposal we hypothesize that SUR2A-55 combines with ROMK2 to form a cardiac mitoKATP channel that blocks ischemic injury by activating the mitochondrial K+ cycle and enhancing glucose metabolism. By targeting both mitochondria and myocardial substrate utilization, SUR2A-55 represents a novel target in the treatment of ischemic heart disease. We propose to investigate this hypothesis with three specific aims. Specific Aim 1: Determine if SUR2A-55 associates with ROMK in cardiac mitochondria to form a mitochondrial K+ channel. Immuno-affinity enrichment coupled with mass spectroscopy will be used to examine potential associations between SUR2A-55 and ROMK2. Specific Aim 2: Determine if the loss of function of cardiac ROMK prevents activation of mitoKATP and cardioprotection. We will test whether pharmacologic inhibition or genetic knockdown of ROMK prevents activation of mitoKATP and protection from ischemic preconditioning. Specific Aim 3: Examine how TGSUR2A-55 mice utilize metabolic substrates and whether a preference for glucose utilization over fatty acids during ischemia contributes to cardioprotection. Glucose and fatty acid metabolism from isolated hanging hearts during rest and after ischemia will be assessed in TGSUR2A-55 and WT mice. Career Plan: My long-term career goal is to become an independently funded VA physician-scientist who is a leader in the field of treating ischemic heart disease by targeting cardiac mitochondria and metabolism. My primary VA research mentor, Dr. Nihal Ahmad, will guide my progress and training. My additional mentors and collaborators will provide training to accomplish my research aims and career goals. The results from this VA CDA will provide me with the preliminary data and research experience to formulate a competitive MERIT Review proposal to further develop novel therapeutic targets for ischemic heart disease. Environment: I will complete the proposed research at the VA and the University of Wisconsin. Both organizations provide an exceptionally collegial atmosphere and strong institutional support that include laboratory resources, equipment, and core facilities.