Ca2+ signaling in microdomains -: Homer1 mediates the interaction between RyR2 and Cav1.2 to regulate excitation-contraction coupling
Ca2+ signaling in microdomains -: Homer1 mediates the interaction between RyR2 and Cav1.2 to regulate excitation-contraction coupling
复制标题
DOI：
10.1074/jbc.m611529200
复制
发表时间：
2007-05-11
影响因子：
4.8
通讯作者：
Zeng, Weizhong
中科院分区：
文献类型：
--
作者：
Huang, Guojin;Kim, Joo Young;Zeng, Weizhong
平滑肌和心肌中的兴奋-收缩（E-C）偶联和Ca 2+诱导的Ca 2+释放由L型Ca 2+通道亚型Ca（v）1.2和兰尼碱受体亚型RyR 2介导。虽然骨骼肌中Ca（v）1.1和RyR 1之间的物理耦合已经建立，但通常认为Ca（v）1.2和RyR 2在E-C耦合期间不会被动或动态地直接通信。在目前的工作中，我们通过研究野生型和Homer 1（-/-）小鼠逼尿肌中的E-C偶联，并通过使用分裂绿色荧光蛋白技术证明Homer 1介导的Ca（v）1.2和RyR 2之间的动态相互作用，重新验证了这一假设。小鼠Homer 1的缺失（但Homer 2或Homer 3的缺失除外）会导致膀胱功能受损，这与逼尿肌对毒蕈碱刺激和膜去极化的更高敏感性有关。这不是由于RyR 2和Ca（v）1.2的表达或功能改变。最值得注意的是，在存在和不存在Homer 1同种型的情况下，用互补的绿色荧光蛋白的C-和N-末端半部分标记的Ca（v）1.2和RyR 2的表达揭示了H1 a和H1b/c调控Ca（v）1.2和RyR 2之间的动态相互作用，以调节Ca 2+诱导的Ca 2+释放的强度及其对膜去极化的依赖性。这些发现定义了Ca（v）1.2和RyR 2的E-C耦合的“双态”模型的分子基础。在一种状态下，Ca（v）1.2通过H1b/c与RyR 2偶联，这导致对膜去极化的响应降低，而在另一种状态下，H1 a使Ca（v）1.2和RyR 2解偶联，以增强对膜去极化的响应。这些发现揭示了Ca（v）1.2和RyR 2之间的一种意想不到的和新颖的相互作用和通信模式，对平滑肌和可能的心肌E-C偶联的调节具有重要意义。
Excitation-contraction (E-C) coupling and Ca2+-induced Ca2+ release in smooth and cardiac muscles is mediated by the L-type Ca2+ channel isoform Ca(v)1.2 and the ryanodine receptor isoform RyR2. Although physical coupling between Ca(v)1.1 and RyR1 in skeletal muscle is well established, it is generally assumed that Ca(v)1.2 and RyR2 do not directly communicate either passively or dynamically during E-C coupling. In the present work, we re-examined this assumption by studying E-C coupling in the detrusor muscle of wild type and Homer1(-/-) mice and by demonstrating a Homer1-mediated dynamic interaction between Ca(v)1.2 and RyR2 using the split green fluorescent protein technique. Deletion of Homer1 in mice (but not of Homer2 or Homer3) resulted in impaired urinary bladder function, which was associated with higher sensitivity of the detrusor muscle to muscarinic stimulation and membrane depolarization. This was not due to an altered expression or function of RyR2 and Ca(v)1.2. Most notably, expression of Ca(v)1.2 and RyR2 tagged with the complementary C- and N- terminal halves of green fluorescent protein and in the presence and absence of Homer1 isoforms revealed that H1a and H1b/c reciprocally modulates a dynamic interaction between Ca(v)1.2 and RyR2 to regulate the intensity of Ca2+-induced Ca2+ release and its dependence on membrane depolarization. These findings define the molecular basis of a "two-state" model of E-C coupling by Ca(v)1.2 and RyR2. In one state, Ca(v)1.2 couples to RyR2 by H1b/c, which results in reduced responsiveness to membrane depolarization and in the other state H1a uncouples Ca(v)1.2 and RyR2 to enhance responsiveness to membrane depolarization. These findings reveal an unexpected and novel mode of interaction and communication between Ca(v)1.2 and RyR2 with important implications for the regulation of smooth and possibly cardiac muscle E-C coupling.