ADP: A Master Regulator for Bioenergetics and Ca2+/ROS Signaling in Heart

描述（由申请人提供）：心力衰竭是一种严重的医学问题：在美国有超过500万人受到影响。慢性心力衰竭的原因是多方面的，包括生物能量缺乏，Ca 2+过载和氧化应激。ADP是ATP形成的关键底物。此外，ADP是线粒体通透性转换孔（mPTP）开放的有效抑制剂。虽然mPTP的分子身份仍然没有解决，但两个不同的概念脱颖而出。其中一个表明腺嘌呤核苷酸移位酶（ANT）不是mPTP所必需的，而另一个将mPTP描述为多蛋白复合物，ANT和称为亲环素-D（Cyp-D）的线粒体肽基脯氨酰顺反异构酶是关键组分。有趣的是，ADP与ANT的结合促进心磷脂稳定呼吸链超复合物，从而增强ATP产生的效率。心磷脂的氧化使这些超复合物不稳定，并与衰老、糖尿病性心肌病、缺血-再灌注损伤和心力衰竭相关的线粒体功能障碍有关。此外，ADP抑制无机磷酸盐Pi的流出，无机磷酸盐Pi是形成Ca 2 +-Pi复合物的关键线粒体Ca 2+缓冲液。最后，线粒体分裂蛋白DLP 1的激活导致线粒体分裂、ROS产生和mPTP开放。总之，这些结果使我们假设“ADP与ANT的结合在线粒体功能中起两个基本作用：通过稳定心磷脂-ETC复合物来增强ATP生成效率，通过减少ROS生成和DLP 1激活来抑制mPTP。在生理学上，ADP介导的mPTP抑制使过量的线粒体ROS产生和从线粒体释放的Ca 2+最小化，以优化兴奋-收缩-代谢（ECM）偶联的有效性。在病理学上，这种ADP调节机制的缺陷导致能量衰竭、氧化应激和Ca 2+失调，从而增强心脏对损伤的脆弱性。我们提出了2个具体目标：具体目标1：确定ADP抑制mPTP的机制。假设：ADP稳定心磷脂完整性并抑制线粒体中的DLP 1活性，从而防止Cyp-D非依赖性mPTP开放。此外，ADP通过抑制mPTP减少ROS的产生，从而使ROS对mPTP的反馈激活最小化。具体目标2：评估ADP在心脏保护中的作用。假设：疾病模型的心脏中的mPTP表现出对Ca 2+诱导的开放的敏感性增加，这是由于其对包括氧化应激、高DLP 1活性和/或降低的Ca 2+缓冲能力的首次打击应激的易感性。维持最佳的ADP水平矩阵，这增加了mPTP的脆弱性。代谢信号传导和Ca 2 +/氧化还原/细胞死亡信号传导之间的相互作用的干扰是包括心脏疾病在内的疾病发病机制的基础。这种应用中的探索性和高风险的想法，如果得到验证，将在广泛的疾病机制和治疗方面开辟新天地。

DESCRIPTION (provided by applicant): Heart failure is a serious medical problem: over 5 million people in the US affected. The cause for chronic heart failure is multifaceted and includes bioenergetic deficiency, Ca2+ overload, and oxidative stress. ADP is the key substrate for ATP formation. Moreover, ADP is a potent inhibitor for the opening of mitochondrial permeability transition pore (mPTP). Although the molecular identity of mPTP is still unsolved, 2 different concepts stand out. One indicates that adenine nucleotide translocase (ANT) is not required for mPTP, whereas the other depicts mPTP as a multi-protein complex, the ANT and the mitochondrial peptidyl-prolyl cis-trans isomerase known as cyclophilin-D (Cyp-D), are the key components. Interestingly, binding of ADP to ANT facilitates cardiolipin to stabilize respiratory chain supercomplexes so that the efficiency of ATP generation is enhanced. Oxidation of cardiolipin destabilizes these supercomplexes and has been linked to mitochondrial dysfunction associated with aging, diabetic cardiomyopathy, ischemia-reperfusion injury, and heart failure. Furthermore, ADP inhibits efflux of inorganic phosphate Pi, the key mitochondrial Ca2+ buffer that forms Ca2+-Pi complex. Finally, activation of the mitochondrial fission protein, DLP1 causes mitochondrial fission, ROS generation, and mPTP opening. Taken together, these results lead us to hypothesize that "binding of ADP to ANT serves two fundamental roles in mitochondrial function: enhancing ATP generation efficiency by stabilizing cardiolipin-ETC complexes and inhibiting mPTP by decreasing ROS generation and DLP1 activation. Physiologically, ADP- mediated mPTP inhibition minimizes excessive mitochondrial ROS generation and Ca2+ release from mitochondria in order to optimize the effectiveness of excitation-contraction-metabolism (ECM) coupling. Pathologically, defects of this ADP regulatory mechanism lead to energetic failure, oxidative stress, and Ca2+ dysregulation that enhance cardiac vulnerability to injury". We propose 2 Specific Aims: Specific Aim 1: To determine the mechanisms for ADP inhibition of mPTP. Hypothesis: ADP stabilizes cardiolipin integrity and inhibits DLP1 activity in the mitochondria and thus protects against Cyp-D-independent mPTP opening. Moreover, ADP decreases ROS generation via mPTP inhibition, and thus minimizes feedback activation of mPTP by ROS. Specific Aim 2: To assess the role of ADP in cardiac protection. Hypothesis: The mPTP in hearts of diseased models exhibits increased sensitivity to Ca2+-induced opening due to its predisposition to the first hit stresses including oxidative stress, high DLP1 activity, and/or diminished Ca2+ buffering capacity. Maintenance of optimal matrix ADP levels alleviates this increased mPTP vulnerability. Disturbances in the interaction between metabolic signaling and Ca2+/redox/cell death signaling are fundamental in disease pathogenesis including cardiac diseases. The exploratory and high-risk ideas in this application, if validated, will break new ground in a wide spectrum of disease mechanisms and treatments.