Functional ryanodine receptors in the plasma membrane of RINm5F pancreatic beta-cells.
Functional ryanodine receptors in the plasma membrane of RINm5F pancreatic beta-cells.
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DOI：
10.1074/jbc.m805587200
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发表时间：
2009-02-20
影响因子：
4.8
通讯作者：
Taylor, Colin W.
中科院分区：
文献类型：
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作者：
Rosker, Christian;Meur, Gargi;Taylor, Emily J. A.;Taylor, Colin W.
Ryanodine受体(RyR)是一种钙离子通道，能在不同的细胞内信号作用下，调节细胞内钙离子的释放。在RINm5F胰岛素瘤细胞中，RyR的激动剂咖啡因和4-氯-间甲酚(4CmC)可刺激钙内流，这种内流不依赖于细胞内的钙离子内流，并可被RyR失活的兰诺定预先孵育所阻断。膜片钳记录发现少量大电导(γK=169pS)阳离子通道可被咖啡因、4CmC或低浓度兰尼定激活。在大鼠胰腺β细胞中也检测到类似的通道。在RINm5F细胞中，胞内Ru红可阻断通道，但不能阻断胞外通道。亚细胞分级显示，IP3受体(IP3R3)主要在内质网表达，而RyR2也存在于质膜部分。使用RNAi选择性地降低RyR1、RyR2或IP3R3的表达，我们发现RyR2既介导了钙离子内流，也介导了由RyR激动剂引起的质膜电流。结论：在RINm5F胰腺β-细胞的质膜上有少量RyR2的选择性表达，介导细胞内钙离子内流。
Ryanodine receptors (RyR) are Ca2+ channels that mediate Ca2+ release from intracellular stores in response to diverse intracellular signals. In RINm5F insulinoma cells, caffeine, and 4-chloro-m-cresol (4CmC), agonists of RyR, stimulated Ca2+ entry that was independent of store-operated Ca2+ entry, and blocked by prior incubation with a concentration of ryanodine that inactivates RyR. Patch-clamp recording identified small numbers of large-conductance (γK = 169 pS) cation channels that were activated by caffeine, 4CmC or low concentrations of ryanodine. Similar channels were detected in rat pancreatic β-cells. In RINm5F cells, the channels were blocked by cytosolic, but not extracellular, ruthenium red. Subcellular fractionation showed that type 3 IP3 receptors (IP3R3) were expressed predominantly in endoplasmic reticulum, whereas RyR2 were present also in plasma membrane fractions. Using RNAi selectively to reduce expression of RyR1, RyR2, or IP3R3, we showed that RyR2 mediates both the Ca2+ entry and the plasma membrane currents evoked by agonists of RyR. We conclude that small numbers of RyR2 are selectively expressed in the plasma membrane of RINm5F pancreatic β-cells, where they mediate Ca2+ entry.