Real-time three-dimensional imaging of lipid signal transduction:: apical membrane insertion of epithelial Na+ channels
Real-time three-dimensional imaging of lipid signal transduction:: apical membrane insertion of epithelial Na+ channels
复制标题
DOI：
10.1152/ajpcell.00226.2004
复制
发表时间：
2004-12-01
影响因子：
5.5
通讯作者：
Bacallao, RL
中科院分区：
文献类型：
--
作者：
Blazer-Yost, BL;Vahle, JC;Bacallao, RL
在远端小管中，Na+吸收由上皮Na+通道（ENaC）介导。醛固酮、抗利尿激素和胰岛素等激素调节ENaC膜的靶向、组装和/或动力学活性，从而调节盐和水的内稳态。胰岛素与基膜上的受体结合，启动信号转导级联，迅速导致根尖膜ENaC的增加。目前这种信号通路的模型设想信号中间体从基膜扩散到顶膜。这就需要在三维空间中扩散几个高分子量的信号元件。胰岛素信号的转导涉及磷酸肌苷途径，但这种基于脂质的信号通路如何以及在何处控制ENaC活性尚不清楚。我们使用标记通道、生物传感器脂质探针和活体成像来研究脂质在胰岛素刺激的Na+通量中的作用。胰岛素刺激的细胞内ENaC向根尖膜的传递与质膜限制的脂质组成变化同时发生。值得注意的是，在胰岛素的作用下，磷脂酰肌醇3,4,5-三磷酸（PIP3）在基底外侧膜形成，在双分子层内迅速扩散，并穿过紧密连接进入顶膜。这种新的信号通路利用了质膜内小叶的脂质不受紧密连接约束的事实。因此，PIP3作为信号转导中间体的扩散发生在平面内，从而促进快速反应，限制和控制信号通路。
In the distal tubule, Na+ resorption is mediated by epithelial Na+ channels ( ENaC). Hormones such as aldosterone, vasopressin, and insulin modulate ENaC membrane targeting, assembly, and/or kinetic activity, thereby regulating salt and water homeostasis. Insulin binds to a receptor on the basal membrane to initiate a signal transduction cascade that rapidly results in an increase in apical membrane ENaC. Current models of this signaling pathway envision diffusion of signaling intermediates from the basal to the apical membrane. This necessitates diffusion of several high-molecular-weight signaling elements across a three-dimensional space. Transduction of the insulin signal involves the phosphoinositide pathway, but how and where this lipid-based signaling pathway controls ENaC activity is not known. We used tagged channels, biosensor lipid probes, and intravital imaging to investigate the role of lipids in insulin-stimulated Na+ flux. Insulin-stimulated delivery of intracellular ENaC to apical membranes was concurrent with plasma membrane-limited changes in lipid composition. Notably, in response to insulin, phosphatidylinositol 3,4,5-trisphosphate (PIP3) formed in the basolateral membrane, rapidly diffused within the bilayer, and crossed the tight junction to enter the apical membrane. This novel signaling pathway takes advantage of the fact that the lipids of the plasma membrane's inner leaflet are not constrained by the tight junction. Therefore, diffusion of PIP3 as a signal transduction intermediate occurs within a planar surface, thus facilitating swift responses and confining and controlling the signaling pathway.