Planès Rémi, Ben Haij Nawal, Leghmari Kaoutar, Serrero Manutea, BenMohamed Lbachir, Bahraoui Elmostafa
CPTP, U1043, INSERM/CNRS/UPS, Toulouse, France.
Université Paul Sabatier Toulouse 3, Toulouse, France.
J Virol. 2016 Jun 10;90(13):5886-5898. doi: 10.1128/JVI.00262-16. Print 2016 Jul 1.
In this study, we show that the HIV-1 Tat protein interacts with rapid kinetics to engage the Toll-like receptor 4 (TLR4) pathway, leading to the production of proinflammatory and anti-inflammatory cytokines. The pretreatment of human monocytes with Tat protein for 10 to 30 min suffices to irreversibly engage the activation of the TLR4 pathway, leading to the production of tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10), two cytokines strongly implicated in the chronic activation and dysregulation of the immune system during HIV-1 infection. Therefore, this study analyzed whether the HIV-1 Tat protein is able to activate these two pathways separately or simultaneously. Using three complementary approaches, including mice deficient in the MyD88, TIRAP/MAL, or TRIF adaptor, biochemical analysis, and the use of specific small interfering RNAs (siRNAs), we demonstrated (i) that Tat was able to activate both the MyD88 and TRIF pathways, (ii) the capacity of Tat to induce TIRAP/MAL degradation, (iii) the crucial role of the MyD88 pathway in the production of Tat-induced TNF-α and IL-10, (iv) a reduction but not abrogation of IL-10 and TNF-α by Tat-stimulated macrophages from mice deficient in TIRAP/MAL, and (v) the crucial role of the TRIF pathway in Tat-induced IL-10 production. Further, we showed that downstream of the MyD88 and TRIF pathways, the Tat protein activated the protein kinase C (PKC) βII isoform, the mitogen-activated protein (MAP) kinases p38 and extracellular signal-regulated kinase 1/2 (ERK1/2), and NF-κB in a TLR4-dependent manner. Collectively, our data show that by recruiting the TLR4 pathway with rapid kinetics, the HIV-1 Tat protein leads to the engagement of both the MyD88 and TRIF pathways and to the activation of PKC, MAP kinase, and NF-κB signaling to induce the production of TNF-α and IL-10.
In this study, we demonstrate that by recruiting the TLR4 pathway with rapid kinetics, the HIV-1 Tat protein leads to the engagement of both the MyD88 and TRIF pathways and to the activation of PKC-βII, MAP kinase, and NF-κB signaling to induce the production of TNF-α and IL-10, two cytokines strongly implicated in the chronic activation and dysregulation of the immune system during HIV-1 infection. Thus, it may be interesting to target Tat as a pathogenic factor early after HIV-1 infection. This could be achieved either by vaccination approaches including Tat as an immunogen in potential candidate vaccines or by developing molecules capable of neutralizing the effect of the Tat protein.
在本研究中，我们表明HIV-1反式激活因子（Tat）蛋白以快速动力学相互作用，参与Toll样受体4（TLR4）信号通路，导致促炎和抗炎细胞因子的产生。用人单核细胞与Tat蛋白预处理10至30分钟足以不可逆地激活TLR4信号通路，导致肿瘤坏死因子α（TNF-α）和白细胞介素-10（IL-10）的产生，这两种细胞因子在HIV-1感染期间免疫系统的慢性激活和失调中起重要作用。因此，本研究分析了HIV-1 Tat蛋白是否能够单独或同时激活这两条信号通路。使用三种互补方法，包括髓样分化因子88（MyD88）、TIR结构域衔接蛋白（TIRAP）/髓样分化因子88激活样蛋白（MAL）或TRIF衔接蛋白缺陷的小鼠、生化分析以及使用特异性小干扰RNA（siRNA），我们证明：（i）Tat能够激活MyD88和TRIF信号通路；（ii）Tat诱导TIRAP/MAL降解的能力；（iii）MyD88信号通路在Tat诱导的TNF-α和IL-10产生中的关键作用；（iv）来自TIRAP/MAL缺陷小鼠的Tat刺激巨噬细胞产生的IL-10和TNF-α减少但未消除；（v）TRIF信号通路在Tat诱导的IL-10产生中的关键作用。此外，我们表明在MyD88和TRIF信号通路的下游，Tat蛋白以TLR4依赖性方式激活蛋白激酶C（PKC）βII亚型、丝裂原活化蛋白（MAP）激酶p38和细胞外信号调节激酶1/2（ERK1/2）以及核因子κB（NF-κB）。总体而言，我们的数据表明，HIV-1 Tat蛋白通过快速动力学募集TLR4信号通路，导致MyD88和TRIF信号通路的参与以及PKC、MAP激酶和NF-κB信号的激活，从而诱导TNF-α和IL-10的产生。
在本研究中，我们证明HIV-1 Tat蛋白通过快速动力学募集TLR4信号通路，导致MyD88和TRIF信号通路的参与以及PKC-βII、MAP激酶和NF-κB信号的激活，从而诱导TNF-α和IL-10的产生，这两种细胞因子在HIV-1感染期间免疫系统的慢性激活和失调中起重要作用。因此，在HIV-1感染后早期将Tat作为致病因子进行靶向治疗可能是有意义的。这可以通过包括将Tat作为潜在候选疫苗中的免疫原的疫苗接种方法来实现，或者通过开发能够中和Tat蛋白作用的分子来实现。
