Mechanisms for Adenylyl Cyclase Effects in the Heart

腺苷酸环化酶（Adenylyl cyclase，AC）是心肌细胞和其他细胞的重要效应分子。1998年，我们发现腺苷酸环化酶的量限制了心肌细胞产生cAMP的能力。1随后的研究表明，AC基因表达对正常和衰竭心脏的心血管功能具有明显的有利影响，2-7包括增加整体左心室（LV）功能，增加存活率和预防有害重塑。我们实验室的初步数据表明，AC表达也与急性心肌梗死死亡率降低有关。解释AC对心脏功能的这些有利作用的机制尚不清楚。最直接的解释是，这种益处来自于细胞内cAMP水平的增加，这与目前心力衰竭的教条相反，该教条认为增加cAMP的正性肌力药物对心脏有害。8缺乏这些有利作用的无懈可击的机制，以及AC在心血管治疗中广泛应用的潜力，要求严格研究AC表达如何影响心脏结构，功能和转录调控。该建议旨在确定AC影响急性心肌梗死和心力衰竭患者心脏功能和生存率的机制。我们建议使用临床相关心血管疾病的动物模型，转基因小鼠的独特品系和基因转移方法来发现AC如何对心脏功能产生有利影响。使用具有AC V型（ACV）和VI型（ACVi）（哺乳动物心脏中的主要亚型）的靶向缺失的转基因小鼠以及策略性地使用AC的可诱导心脏特异性表达提供了新的方法，这将使我们能够实现我们的目标。假设：1.心肌细胞腺苷酸环化酶表达增加与心肌梗死后早期死亡率降低相关。2.在衰竭心脏的心肌细胞中腺苷酸环化酶表达的增加将与增加收缩性的基因的表达相关。3.增加心肌细胞腺苷酸环化酶含量将通过cAMP依赖性和cAMP非依赖性途径改变基因表达和蛋白磷酸化。4.腺苷酸环化酶V型和VI型的消除将对心脏功能产生影响，阐明其特定的功能作用。腺苷酸环化酶VI型的靶向缺失将对正常和衰竭的心脏产生不利影响。

Adenylyl cyclase (AC) has long been recognized as a pivotal effector molecule in cardiac myocytes and other cells. In 1998 we showed that the amount of adenylyl cyclase sets a limit on the ability of cardiac myocytes to generate cAMP.1 Subsequent studies showed that AC gene expression has a pronounced favorable effect on cardiovascular function in normal and failing hearts,2-7 including increased global left ventricular (LV) function, increased survival and prevention of deleterious remodeling. Preliminary data from our laboratory suggest that AC expression also is associated with reduced mortality in acute myocardial infarction. Mechanisms explaining these favorable effects of AC on heart function are unknown. The most direct explanation - that the benefits stem from increased intracellular levels of cAMP - is contrary to current dogma in heart failure asserting that inotropic agents that increase cAMP are bad for the heart.8 The absence of unassailable mechanisms for these favorable effects - and the potential for broadened application of AC in cardiovascular therapeutics - mandate a rigorous study of how AC expression effects cardiac structure, function and transcriptional regulation. This proposal is designed to determine mechanisms by which AC affects cardiac function and survival in acute myocardial infarction and heart failure. We propose to use animal models of clinically relevant cardiovascular diseases, unique lines of transgenic mice and methods of gene transfer to discover how AC confers favorable effects on heart function. The use of transgenic mice with targeted deletions of AC type V (ACV) and type VI (ACVi) - the dominant isoforms in mammalian heart - and strategic use of inducible cardiac-specific expression of AC provide novel approaches that will enable us to achieve our goals. Hypotheses: 1. Increased adenylyl cyclase expression in cardiac myocytes will be associated with reduced early mortality after myocardial infarction. 2. Increased adenylyl cyclase expression in cardiac myocytes of failing hearts will be associated with expression of genes that increase contractility. 3. Increased cardiac myocyte adenylyl cyclase content will alter gene expression and protein phosphorylation through cAMP-dependent and cAMP-independent pathways. 4. Elimination of adenylyl cyclase Type V and Type VI will have effects on cardiac function that elucidate their specific functional roles. Targeted deletions of adenylyl cyclase Type VI will have adverse effects on normal and failing hearts.