A close association of RyRs with highly dense clusters of Ca2+-activated Cl- channels underlies the activation of STICs by Ca2+ sparks in mouse airway smooth muscle.
A close association of RyRs with highly dense clusters of Ca2+-activated Cl- channels underlies the activation of STICs by Ca2+ sparks in mouse airway smooth muscle.
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DOI：
10.1085/jgp.200709933
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发表时间：
2008-07
期刊：
影响因子：
--
通讯作者：
ZhuGe R
中科院分区：
文献类型：
--
作者：
Bao R;Lifshitz LM;Tuft RA;Bellvé K;Fogarty KE;ZhuGe R
钙火花是肌浆网通过兰尼定受体(RyRs)高度局部化、瞬间释放的钙离子。在平滑肌中，钙火花通过开放附近的大电导钙激活的K+通道簇来触发自发的瞬时外向电流(STOC)，也可以通过门控钙激活的氯离子通道(Cl−，CI(Ca))来诱发自发的瞬时内向电流(STIC)。虽然钙离子火花激活STOCs的分子机制已为人所熟知，但有关钙离子火花如何激活STIC的信息却很少。在本研究中，我们研究了RyRs和Cl(Ca)通道在小鼠呼吸道肌细胞放电部位的空间组织。用高速大视野数字显微镜和全细胞膜片钳分别同时记录细胞内钙离子火花和STICs。应用基于图像的方法测量了钙火花下的钙电流(ICA(Spark))，并对NPEGTA闪光光解所表征的内源性固定钙缓冲进行了适当的修正。我们发现，ICa(Spark)在9ms内达到峰值，并以时间常数为12ms的单一指数衰减，这表明Ca~(2+)火花是多个RyR不同时开放和关闭的结果。STIC的开始时间比ICA(火花)的开始时间滞后不到3ms，其上升阶段与ICA(火花)的持续时间相匹配。我们进一步确定，在钙离子放电过程中，氯(Ca)通道平均暴露于2.4μM或更高的[Ca~(2+)]。达到这一水平的质膜面积半径为600 nm，由测量的ICA(Spark)的反应扩散模拟所产生的[Ca~(2+)]的时空分布显示。最后，我们估计了定位于钙离子火花部位的氯(Ca)通道的数量可以解释整个细胞中所有的氯(Ca)通道。综上所述，这些结果导致我们提出了一个模型，在该模型中，钙离子火花位置上的RyRs和Cl(Ca)通道相互靠近，而且，Cl(Ca)通道集中在半径为∼600 nm的区域，其密度高达300Channel/μm2。该模型揭示了氯(钙)通道通过局部钙信号受到钙火花的严格控制。
Ca2+ sparks are highly localized, transient releases of Ca2+ from sarcoplasmic reticulum through ryanodine receptors (RyRs). In smooth muscle, Ca2+ sparks trigger spontaneous transient outward currents (STOCs) by opening nearby clusters of large-conductance Ca2+-activated K+ channels, and also gate Ca2+-activated Cl− (Cl(Ca)) channels to induce spontaneous transient inward currents (STICs). While the molecular mechanisms underlying the activation of STOCs by Ca2+ sparks is well understood, little information is available on how Ca2+ sparks activate STICs. In the present study, we investigated the spatial organization of RyRs and Cl(Ca) channels in spark sites in airway myocytes from mouse. Ca2+ sparks and STICs were simultaneously recorded, respectively, with high-speed, widefield digital microscopy and whole-cell patch-clamp. An image-based approach was applied to measure the Ca2+ current underlying a Ca2+ spark (ICa(spark)), with an appropriate correction for endogenous fixed Ca2+ buffer, which was characterized by flash photolysis of NPEGTA. We found that ICa(spark) rises to a peak in 9 ms and decays with a single exponential with a time constant of 12 ms, suggesting that Ca2+ sparks result from the nonsimultaneous opening and closure of multiple RyRs. The onset of the STIC lags the onset of the ICa(spark) by less than 3 ms, and its rising phase matches the duration of the ICa(spark). We further determined that Cl(Ca) channels on average are exposed to a [Ca2+] of 2.4 μM or greater during Ca2+ sparks. The area of the plasma membrane reaching this level is <600 nm in radius, as revealed by the spatiotemporal profile of [Ca2+] produced by a reaction-diffusion simulation with measured ICa(spark). Finally we estimated that the number of Cl(Ca) channels localized in Ca2+ spark sites could account for all the Cl(Ca) channels in the entire cell. Taken together these results lead us to propose a model in which RyRs and Cl(Ca) channels in Ca2+ spark sites localize near to each other, and, moreover, Cl(Ca) channels concentrate in an area with a radius of ∼600 nm, where their density reaches as high as 300 channels/μm2. This model reveals that Cl(Ca) channels are tightly controlled by Ca2+ sparks via local Ca2+ signaling.
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影响因子：
4.8
作者：
Eghbali, M;Toro, L;Stefani, E
通讯作者：
Stefani, E
影响因子：
3.4
作者：
Laver, Derek R.
通讯作者：
Laver, Derek R.
影响因子：
56.9
作者：
CANNELL, MB;CHENG, H;LEDERER, WJ
通讯作者：
LEDERER, WJ
DOI：
10.1085/jgp.113.2.187
发表时间：
1999-02
期刊：
The Journal of general physiology
影响因子：
--
作者：
Lacampagne A;Ward CW;Klein MG;Schneider MF
通讯作者：
Schneider MF
DOI：
10.1085/jgp.200609507
发表时间：
2006-07
期刊：
The Journal of general physiology
影响因子：
--
作者：
Angermann JE;Sanguinetti AR;Kenyon JL;Leblanc N;Greenwood IA
通讯作者：
Greenwood IA