CaMKII in Sinus Node Physiology and Disease

摘要 令人兴奋的最新证据支持这样一种观点，即窦房结(SAN)心脏起搏细胞导致 肌浆网(SR)钙离子释放增加和肌浆网钙离子释放增加 去极化内向电流由肌膜Na+/Ca~(2+)交换器(NCX)携带。专属蛋白质 收缩心肌细胞的兴奋收缩偶联和细胞内钙循环 在窦房结细胞中，我们的研究表明，窦房结细胞和心室肌细胞具有相似的SR钙含量， 以细胞膜电容为指标，尽管事实上SAN细胞表现出最小的机械 活动。多功能钙调素依赖的蛋白激酶II(CaMKII)是一种丝氨酸和钙调素依赖的蛋白激酶II。 调节SR相关钙稳态蛋白的苏氨酸激酶，磷蛋白 和兰尼定受体(RyR)。我们的新数据支持这样一种观点，即CaMKII在 肾上腺素能受体(？AR)介导窦房结‘打或逃’的生理反应。此外，在 过度、病理性AR刺激条件下抑制CaMKII可提高SAN细胞存活率 并能预防心律失常。我们假设：1)CaMKII调节肌质网钙摄取和 释放作为生理窦房结对AR刺激反应的细胞机制的一部分；2)CaMKII 抑制通过抑制肌浆网钙离子保护窦房结心律失常、窦房结细胞死亡和肥大 超负荷和减少肌浆网钙离子泄漏；3)内向Ncx电流是肌膜激活的主要靶点 通过肌质网钙离子释放，导致4相细胞膜去极化增强和心率加快。 本实验室已适应并开发了可靠分离小鼠和兔SAN的新方法 细胞，并进行体内病毒基因转移到SAN和体外病毒基因转移培养 SAN细胞。这些创新方法将使我们能够全面测试CaMKII、SR的作用 Ca~(2+)和Ncx在心脏起搏中的作用。

Abstract Exciting recent evidence supports a view that sinoatrial node (SAN) cardiac pacemaker cells cause heart rate increases by enhancement of sarcoplasmic reticulum (SR) Ca2+ release and augmentation of depolarizing inward current carried by the sarcolemmal Na+/Ca2+ exchanger (NCX). Proteins dedicated to excitation-contraction coupling and cellular Ca2+ cycling in contracting cardiomyocytes are preserved in SAN cells, and our studies show SAN cells and ventricular myocytes have similar SR Ca2+ content, indexed for cell membrane capacitance, despite the fact that SAN cells exhibit minimal mechanical activity. The multifunctional Ca2+ and calmodulin-dependent protein kinase II (CaMKII) is a serine- threonine kinase that regulates the SR-associated Ca2+ homeostatic proteins, phospholamban (PLN) and ryanodine receptors (RyR). Our new data support a view that CaMKII plays a central role in ¿ adrenergic receptor (¿AR) mediated SAN 'fight or flight' physiological responses. Furthermore, under conditions of excessive, pathological ¿AR stimulation, CaMKII inhibition enhances SAN cell survival and protects against SAN arrhythmias. We hypothesize that 1) CaMKII regulates SR Ca2+ uptake and release as part of a cellular mechanism for physiological SAN responses to ¿AR stimulation; 2) CaMKII inhibition protects against SAN arrhythmias, SAN cell death and hypertrophy by preventing SR Ca2+ overload and reducing SR Ca2+ leak; 3) inward NCX current is the major sarcolemmal target activated by SR Ca2+ release, leading to enhanced phase 4 cell membrane depolarization and faster heart rates. Our laboratory has adapted and developed new methods for reliably isolating mouse and rabbit SAN cells, and performing in vivo viral gene transfer to the SAN and in vitro viral gene transfer to cultured SAN cells. These innovative approaches will allow us to comprehensively test the role of CaMKII, SR Ca2+ and NCX in cardiac pacing.