Chemokine receptor-4 regulation of Beta adrenergic-mediated calcium channel

描述（由申请人提供）：趋化因子基质细胞衍生因子-1（SDF 1）（也称为CXCL 12）及其主要受体CXCR 4长期以来一直被认为对心肌功能有负面影响，然而，越来越多的证据表明它们的作用已扩展到炎症和协调趋化性之外。最近的观察表明，CXCR 4是组成型表达的心肌细胞（CM）和负性调节心脏收缩功能。我们还证明，SDF-1/CXCR 4激活可防止由于持续暴露于异丙肾上腺素（ISO）（一种非特异性β 2-肾上腺素能激动剂）而导致的舒张期细胞内钙水平升高。钙失衡已被认为是人类心脏功能障碍的潜在机制。电压依赖性钙通道（VDCC）在心脏钙调节中起关键作用。因此，由该通道引起的异常钙信号传导可引发在心力衰竭（HF）中观察到的钙失衡。 2-肾上腺素受体（2AR）介导的信号转导机制不仅调节健康心脏的收缩活动，而且被认为在HF的发展过程中起作用。用于治疗心脏病的两大类药物; β受体阻滞剂和通道阻滞剂靶向VDCC的调节。这强调了这些通道在心脏功能中的重要作用。我们有初步的数据表明，CXCR 4通过其配体的激活阻止了L型VDCC（L-VDCC）的内化/再循环，并降低了通道活性。此外，我们有证据表明，CXCR 4激活负性调节Ca 2+瞬态和收缩功能，响应2-肾上腺素能激动剂。已知2AR的激活导致通过心脏细胞中Cav 1通道的钙电流增加，这是cAMP依赖性蛋白激酶（PKA）磷酸化的结果。我们最近证实，2AR激活通过2-arrestin 1介导的途径诱导心脏CaV1.2通道复合物的内化。我们建议研究CXCR 4负性调节CM中2AR诱导的正性肌力反应的机制。我们的数据表明CXCR 4在心脏中调节功能的两种可能性：CXCR 4介导的（i）2AR信号传导的中断，和/或（ii）激动剂诱导的VDCC内化/脱敏的改变，从而影响Ca 2+处理和调节收缩功能。我们的假设是SDF-1/CXCR 4激活负性调节健康心脏的L-VDCC功能。CXCR 4激活影响2AR信号传导，进而改变激动剂诱导的L-VDCC内化/运输。提出的实验将确定CXCR 4对2AR诱导的L-VDCC内化/脱敏的作用机制，并确定这种相互作用对钙电流和心肌细胞变力性反应的功能意义。 公共卫生相关性： 拟开展的研究将确定SDF-1（基质细胞衍生因子-1）及其主要受体CXCR 4对β肾上腺素能诱导的钙通道内化/脱敏作用的潜在机制，并确定这种相互作用对钙电流和心肌细胞变力性反应的功能意义。

DESCRIPTION (provided by applicant): The chemokine, Stromal Cell Derived Factor-1 (SDF1) (also known as, CXCL12) and its major receptor, CXCR4, have long been thought to have a negative impact on myocardial function, however, there is growing evidence that has expanded their role beyond inflammation and orchestrating chemotaxis. Recent observations demonstrated that CXCR4 is constitutively expressed on cardiac myocytes (CM) and is negatively modulating cardiac contractile function. We have also demonstrated that SDF-1/CXCR4 activation prevents the increase in diastolic intracellular calcium levels due to sustained exposure to isoproterenol (ISO), a non-specific 2-adrenergic agonist. Calcium imbalances have been implicated as an underlying mechanism of human cardiac dysfunction. The voltage-dependent calcium channel (VDCC) plays a critical role in calcium regulation in the heart. Thus, aberrant calcium signaling arising from this channel could initiate the calcium imbalances observed in heart failure (HF). 2-adrenorceptor (2AR)-mediated signal transduction mechanism not only regulates the contractile activity of the healthy heart, but it is also considered to play a role during the development of HF. Two major classes of drugs used to treat heart disease; beta-blockers and channel blockers target the regulation of VDCC. This underscores the important role that these channels play in heart function. We have preliminary data that activation of CXCR4, by its ligand, prevents L type VDCC (L-VDCC) internalization/recycling and reduces channel activity. Additionally, we have evidence that CXCR4 activation negatively modulates Ca2+ transient and contractile function in response to the 2-adrenergic agonist. Activation of 2AR is known to lead to an increase in calcium current through Cav1 channels in cardiac cells as a result of phosphorylation by cAMP-dependent protein kinase (PKA). We have recently demonstrated that 2AR activation induces internalization of cardiac CaV1.2 channel complexes through a 2-arrestin 1 mediated pathway. We propose to study the mechanism by which CXCR4 negatively modulates 2AR-induced positive inotropic response in CM. Our data suggest two possibilities for CXCR4 modulatory function in heart: CXCR4-mediated (i) disruption of 2AR signaling, and/or (ii) alteration in agonist-induced internalization/ desensitization of VDCC thus affecting Ca2+ handling and regulating contractile function. Our hypothesis is that SDF-1/CXCR4 activation negatively modulates L-VDCC function of the healthy heart. CXCR4 activation affects 2AR signaling and in turn alters agonist-induced internalization/ trafficking of L-VDCC. The experiments proposed will identify the mechanisms underlying CXCR4 effects on 2AR-induced L-VDCC internalization/desensitization and determine the functional significance of this interaction on calcium current and myocytes inotropic response. PUBLIC HEALTH RELEVANCE: The proposed studies will identify the mechanisms underlying SDF-1 (Stromal Cell Derived Factor-1) and its major receptor, CXCR4, effects on Beta adrenergic-induced calcium channel internalization/desensitization and determine the functional significance of this interaction on calcium current and myocytes inotropic response.