Highly Ca2+-selective TRPM channels regulate IP3-dependent oscillatory Ca2+ signaling in the C-elegans intestine
Highly Ca2+-selective TRPM channels regulate IP3-dependent oscillatory Ca2+ signaling in the C-elegans intestine
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DOI：
10.1085/jgp.200709914
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发表时间：
2008-03-01
影响因子：
3.8
通讯作者：
Strange, Kevin
中科院分区：
文献类型：
--
作者：
Xing, Juan;Yan, Xiaohui;Strange, Kevin
秀丽隐杆线虫的后体壁肌肉收缩（pBoc）每45-50秒有节奏地发生，并介导排便。pBoc由肠中肌醇-1，4，5-三磷酸（IP 3）依赖性Ca 2+振荡控制。肠上皮细胞可以通过膜片钳电生理学、Ca 2+成像、全基因组反向遗传分析、正向遗传学和分子生物学进行研究，从而提供了一个强大的模型来开发一个完整的系统水平的非兴奋性细胞振荡Ca 2+信号通路的理解。肠细胞表达一个向外整流钙（ORCa）电流的生物物理特性类似的TRPM通道。两种TRPM同源物GON-2和GTL-1在肠中表达。使用gtl-1和gon-2基因的缺失和功能严重丧失的等位基因，我们在这里证明GON-2和GTL-1都是维持节律性pBoc和肠道Ca 2+振荡所必需的。GTL-1和GON- 2功能的丧失分别抑制了类似于70%和类似于90%的I-ORCa。在gon-2; gtl-1双突变细胞中检测不到I-ORCa。这些结果表明，（a）GON-2和GTL-1都是ORCa通道功能所需的，（B）GON- 2和GTL-1可以独立地作为离子通道发挥功能，但它们在介导I-ORCa中的功能是相互依赖的。I-ORCa、I（GON-2）和IGTL-1具有几乎相同的生物物理性质。重要的是，所有三个通道对Ca 2+的渗透性至少是Na+的60倍。上位性分析表明，GON- 2和GTL-1在IP 3信号通路中发挥作用，调节肠道Ca 2+振荡。我们推测GON- 2和GTL-1形成异聚体ORCa通道，其介导选择性Ca 2+内流并起调节IP 3受体活性和可能再填充ER Ca 2+商店的作用。
Posterior body wall muscle contraction (pBoc) in the nematode Caenorhabditis elegans occurs rhythmically every 45-50 s and mediates defecation. pBoc is controlled by inositol-1,4,5-trisphosphate (IP3)-dependent Ca2+ oscillations in the intestine. The intestinal epithelium can be studied by patch clamp electrophysiology, Ca2+ imaging, genome-wide reverse genetic analysis, forward genetics, and molecular biology and thus provides a powerful model to develop an integrated systems level understanding of a nonexcitable cell oscillatory Ca2+ signaling pathway. Intestinal cells express an outwardly rectifying Ca2+ (ORCa) current with biophysical properties resembling those of TRPM channels. Two TRPM homologues, GON-2 and GTL-1, are expressed in the intestine. Using deletion and severe loss-of-function alleles of the gtl-1 and gon-2 genes, we demonstrate here that GON-2 and GTL-1 are both required for maintaining rhythmic pBoc and intestinal Ca2+ oscillations. Loss of GTL-1 and GON- 2 function inhibits I-ORCa similar to 70% and similar to 90%, respectively. I-ORCa is undetectable in gon-2; gtl-1 double mutant cells. These results demonstrate that (a) both gon-2 and gtl-1 are required for ORCa channel function, and (b) GON- 2 and GTL-1 can function independently as ion channels, but that their functions in mediating I-ORCa are interdependent. I-ORCa, I (GON-2), and IGTL-1 have nearly identical biophysical properties. Importantly, all three channels are at least 60-fold more permeable to Ca2+ than Na+. Epistasis analysis suggests that GON- 2 and GTL-1 function in the IP3 signaling pathway to regulate intestinal Ca2+ oscillations. We postulate that GON- 2 and GTL-1 form heteromeric ORCa channels that mediate selective Ca2+ influx and function to regulate IP3 receptor activity and possibly to refill ER Ca2+ stores.