Department of Neurosurgery, Molecular Neuroscience and Vascular Biology Laboratory, University of Kentucky Medical Center, Lexington, Kentucky 40536, USA.
J Cereb Blood Flow Metab. 2010 Mar;30(3):522-33. doi: 10.1038/jcbfm.2009.214. Epub 2009 Sep 30.
The Rho signaling has an essential function in human immunodeficiency virus (HIV)-1-mediated disruption of the integrity of the blood-brain barrier (BBB). However, it is unknown how membrane domains, such as lipid rafts, can influence HIV-1-mediated activation of the Rho pathway and how these processes can affect the expression of the efflux transporters at the BBB level. This study is focused on the function of HIV-1 protein Tat in activation of the Rho signaling and upregulation of P-glycoprotein (P-gp) in human brain endothelial cells. Treatment with Tat markedly elevated GTP-RhoA levels and the potential downstream effectors, such as myosin phosphatase target subunit 1 and myosin light chain. In addition, Tat upregulated expression and promoter activity of P-gp as well as its efflux function. Inhibition of the Rho signaling cascade effectively blocked P-gp overexpression at the level of promoter activity. Disruption of lipid rafts by depletion of membrane cholesterol by methyl-beta-cyclodextrin, but not caveolin-1 silencing, also abolished Tat-mediated RhoA activation and P-gp upregulation. The present data indicate the critical function of intact lipid rafts and the Rho signaling in HIV-1-mediated upregulation of P-gp and potential development of drug resistance in brain endothelial cells.
Rho 信号通路在人类免疫缺陷病毒（HIV）-1 破坏血脑屏障（BBB）完整性的过程中具有重要作用。然而，目前尚不清楚膜域（如脂筏）如何影响 HIV-1 介导的 Rho 通路激活，以及这些过程如何影响 BBB 水平上的外排转运蛋白的表达。本研究集中于 HIV-1 蛋白 Tat 在激活 Rho 信号通路和上调人脑血管内皮细胞中 P-糖蛋白（P-gp）方面的功能。Tat 的处理显著增加了 GTP-RhoA 水平和潜在的下游效应物，如肌球蛋白磷酸酶靶亚基 1 和肌球蛋白轻链。此外，Tat 上调了 P-gp 的表达和启动子活性及其外排功能。Rho 信号级联的抑制通过甲基-β-环糊精耗竭膜胆固醇而非小窝蛋白-1 沉默有效地阻断了 P-gp 在启动子活性水平上的过表达。脂筏的破坏通过甲基-β-环糊精耗竭膜胆固醇，但不是小窝蛋白-1 沉默，也消除了 Tat 介导的 RhoA 激活和 P-gp 上调。这些数据表明，完整的脂筏和 Rho 信号通路在 HIV-1 介导的 P-gp 上调以及脑内皮细胞中潜在的耐药性发展中具有关键作用。
