Intact Lipid Rafts Regulate HIV-1 Tat Protein-Induced Activation of the Rho Signaling and Upregulation of P-Glycoprotein in Brain Endothelial Cells

Abstract

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 GTPRhoA 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.

The Basic Domain of HIV-Tat Transactivating Protein Is Essential for Its Targeting to Lipid Rafts and Regulating Fibroblast Growth Factor-2 Signaling in Podocytes Isolated from Children with HIV-1–Associated Nephropathy

“…These findings indicate that the CRAC sequence alone is not sufficient to warrant cholesterol binding and that other structural factors are needed for this process. 32 Tat Basic Binding Domain Modulates Rho-A Signaling and the Expression of Matrix Metalloproteinase-9 in LRs Rho-A signaling and matrix metalloproteinases (MMPs) modulate the migration of HIV-infected cells 26 and facilitate the release of FGF-2 in patients with Kaposi's sarcoma. 34,35 Children with HIVAN excrete high urinary levels of MMPs and FGF-2, which is in correlation with the progression of Methods.…”

“…Tat Basic Domain Modulates the Expression of pERK, Rho-A, pMLC 2 , and MMP-9 in the Kidneys of Young HIV-Tg 26 Mice To determine the role of the Tat basic domain in vivo, we used an adenoviral gene transferring technique developed in our laboratory 37 to express Tat in the kidney of young mice (Supplemental Figures 5 and 6). As shown in Figure 7, both WTand HIV-Tg 26 mice infected with Ad-Tat-WT-HIVAN showed a significant upregulation of renal pERK, Rho-A, pMLC, and MMP-9 compared with mice infected with Ad-Tat-BDM1-HIVAN.…”

“…23 In fact, activation of G protein-coupled receptors by HIV-Tat in brain endothelial cells results in the stimulation of small guanosine 59-triphosphatase of the Rhofamily, which in turn, activate Rho-kinase and the myosin binding subunit of the myosin light chain (MLC). 26,27 Moreover, activation of the Rho-A pathway in podocytes can cause chronic renal failure in transgenic mice. 28 Therefore, we carried out this study to determine whether Tat, alone or combined with FGF-2, can induce cytoskeletal changes in cultured podocytes acting through an LR-mediated Rho-signaling mechanism and to define the Tat binding motif regulating this process in podocytes harvested from children with HIVAN.…”

Rho’ing in and out of cells

“…208,209 The Tat protein of HIV is of particular importance in this respect, as it may affect BBB integrity through several mechanisms, including decreasing occludin expression through activation of the RhoA/ROCK signaling pathway, altering the expression of ZO-1 (another tight junction protein) through induction of RhoA signaling and phosphorylation and activation of transcription factor cAMP responsive element binding protein (CREB) and translocating ZO-1 to the nucleus through Rac1 activation. 210,211 On the other hand, promotor activity and expression of the P-glycoprotein (P-gp), an ATP-dependent exporter essential for the proper function of the BBB, are upregulated upon Tat-mediated RhoA-expression.…”

Antiretroviral Therapy and HIV-Associated Neurocognitive Disorders

“…However, the ability of ritonavir to increase the expression of p-gp can limit CNS access of concomitantly administered ARVs that are also p-gp substrates. Further, HIV infection can increase p-gp expression in T cells and monocytic cell lines and this capacity may extend to other cell-types, further contributing to the limited penetrance of ARVs to the CNS (Zhong, Hennig et al 2010). MRP-1 provides an additional level of regulation of drug concentrations in the CNS.…”