Das Chinmayee, Vijayan Mathilakath M
Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
Biology (Basel). 2023 Feb 14;12(2):311. doi: 10.3390/biology12020311.
Glucocorticoids (GCs) stimulate rapid cell signalling by activating the membrane-anchored intracellular glucocorticoid receptor (GR). However, the recruitment of the GR to the plasma membrane to facilitate nongenomic signalling is far from clear. As cytosolic free calcium ([Ca]i) is involved in intracellular protein dynamics, we tested the hypothesis that acute elevation in cortisol levels rapidly stimulates GR translocation to the plasma membrane via a calcium-dependent process in rainbow trout () hepatocytes. To test this, we monitored temporal changes in intracellular GR distribution in response to cortisol exposure. Immunofluorescence labelling showed that the GR was present in cytosolic and nuclear compartments in trout hepatocytes. However, upon cortisol exposure, the GR rapidly (within 5 min) formed punctate and colocalized with caveolin-1, suggesting plasma membrane localization of the receptor. This redistribution of the GR to the plasma membrane was transient and lasted for 30 min and was evident even upon exposure to cortisol-BSA, a membrane-impermeable analogue of the steroid. The rapid cortisol-mediated GR translocation to the plasma membrane involved F-actin polymerization and was completely abolished in the presence of either EGTA or Cpd5J-4, a calcium release-activated calcium (CRAC) channel blocker. Additionally, the modulation of the biophysical properties of the plasma membrane by cholesterol or methyl β-cyclodextrin, which led to changes in ([Ca]i) levels, modified GR translocation to the plasma membrane. Altogether, acute cortisol-mediated rise in ([Ca]i) levels rapidly stimulated the translocation of intracellular GR to the plasma membrane, and we propose this as a mechanism promoting the nongenomic action of the GR for hepatocyte stress resistance.
糖皮质激素（GCs）通过激活膜锚定的细胞内糖皮质激素受体（GR）来刺激快速的细胞信号传导。然而，GR募集到质膜以促进非基因组信号传导的机制尚不清楚。由于胞质游离钙（[Ca]i）参与细胞内蛋白质动态变化，我们测试了这样一个假设：皮质醇水平的急性升高通过虹鳟（Oncorhynchus mykiss）肝细胞中依赖钙的过程迅速刺激GR易位到质膜。为了验证这一点，我们监测了皮质醇暴露后细胞内GR分布的时间变化。免疫荧光标记显示，GR存在于虹鳟肝细胞的胞质和核区室中。然而，在皮质醇暴露后，GR迅速（在5分钟内）形成点状并与小窝蛋白-1共定位，表明该受体定位于质膜。GR向质膜的这种重新分布是短暂的，持续30分钟，即使在暴露于皮质醇-BSA（一种类固醇的膜不可渗透类似物）时也很明显。皮质醇介导的GR迅速易位到质膜涉及F-肌动蛋白聚合，并且在EGTA或钙释放激活钙（CRAC）通道阻滞剂Cpd5J-4存在下完全被消除。此外，胆固醇或甲基-β-环糊精对质膜生物物理特性的调节导致（[Ca]i）水平变化，改变了GR向质膜的易位。总之，皮质醇介导的（[Ca]i）水平急性升高迅速刺激细胞内GR向质膜易位，我们认为这是一种促进GR对肝细胞应激抵抗的非基因组作用的机制。
