Transactive response DNA-binding Protein (TDP-43) regulates early HIV-1 entry and infection

Abstract

The transactive response DNA-binding protein (TDP-43) is an important regulator of mRNA, being reported to stabilize the anti-HIV factor, histone deacetylase 6 (HDAC6). However, little is known about the role of TDP-43 in HIV infection. In this work, we seek for the TDP-43 function on regulating CD4+ T cell permissibility to HIV infection. We observed that over-expression of wt-TDP-43 in CD4+ T cells stabilized HDAC6, increasing mRNA and the protein levels of this antiviral enzyme. Under this experimental condition, HIV-1 infection was impaired, independently of the viral envelope glycoprotein (Env) complex tropism. The results obtained by using an HIV-1 Env-mediated cell-to-cell fusion model, under the same experimental conditions, suggest that the increase in TDP-43 levels negatively affects the viral Env fusion capacity. Moreover, the specific siRNA silencing of endogenous TDP-43 in target cells lead to a significant decrease in the levels of HDAC6 which consistently induces an increase in the fusogenic and infection activities of the HIV-1 Env. These observations were confirmed by using primary viral Envs from HIV+ individuals with different clinical phenotypes. An increase in the level of expression of wt-TDP-43 strongly reduced the Envs infection activity of viremic non-progressors (VNP) and rapid progressors (RP) HIV+ individuals down to the levels of the inefficient HIV-1 Envs from long-term non-progressor elite controllers (LTNP-EC) individuals. On the contrary, low levels of endogenous TDP-43, obtained after specific siRNA-TDP-43 knocking-down, significantly favors the infection activity of primary HIV-1 Envs of VNP and RP individuals, leading to an increase in the infection ability of the primary HIV-1/LTNP-EC Envs. Based on this evidence, we interpret that TDP-43 conditions cell permissibility to HIV infection by affecting viral Env fusion and infection capacities, at least by altering the cellular levels of the antiviral enzyme HDAC6.

The ZIKV NS5 Protein Aberrantly Alters the Tubulin Cytoskeleton, Induces the Accumulation of Autophagic p62 and Affects IFN Production: HDAC6 Has Emerged as an Anti-NS5/ZIKV Factor

“…Our results indicate that the ZIKV NS5 protein mainly accumulates in nuclear structures, as previously reported [64,65,117,118], and promotes the acetylation of MTs that aberrantly reorganize in nested-like structures organized at the cell periphery. Similarly, we observed that the p62 protein, a marker of autophagy flux [97][98][99][100][101][102][103], accumulated in cells overexpressing the ZIKV NS5 protein. Notably, these data indicate that NS5 alters cell events that are under the control of the antiviral tubulin deacetylase and the autophagyassociated enzyme HDAC6 [91,[98][99][100][101][104][105][106][107][108]].…”

“…Similarly, we observed that the p62 protein, a marker of autophagy flux [97][98][99][100][101][102][103], accumulated in cells overexpressing the ZIKV NS5 protein. Notably, these data indicate that NS5 alters cell events that are under the control of the antiviral tubulin deacetylase and the autophagyassociated enzyme HDAC6 [91,[98][99][100][101][104][105][106][107][108]]. HDAC6 appears to degrade NS5 by autophagy in a deacetylase-and BUZ (binder of or bound to ubiquitin zinc finger [119,120]) domain-dependent manner and by controlling the cytoplasmic expression of NS5.…”

“…Twentyfour hours later, the cells were transfected with siRNAs, and the same cells were subjected to a second round of treatment with FuGENE HD Transfection reagent for transient expression of viral NS5 or pcDNA TM 3.1(+) empty vector under control conditions and incubated for 24 h to complete a 48 h interval of HDAC6 silencing, when the siRNAs for HDAC6 induced specific interference with protein expression. Cells were then lysed and analysed with specific Abs by Western blotting to validate endogenous HDAC6 silencing, as well as the associated expression of the studied cell and viral proteins, as similarly described [98][99][100][101]106].…”

“…First, we examined the subcellular localization of the ZIKV NS5 protein in HEK-293T cells, a model for ZIKV and other RNA virus infection and production [98][99][100][101][125][126][127], which were transfected with the NS5-myc construct. At 48 h posttransfection (Figure 1a), ZIKV NS5 protein was mainly localized to the nucleus, as observed by biochemical analysis of cell fractioning (Figure 1b) and by immunofluorescence of transfected cells (Figure 1c).…”

“…In this sense, nonstructural protein 5 (NS5) of ZIKV appears to interact with components of the cilium base that are associated with MTs, promoting ciliopathy and premature neurogenesis [96]. However, little is known about the functional involvement of the NS5 protein in altering tubulin cytoskeleton dynamics or sequestosome 1 (SQSTM1)/p62-associated autophagy flux [97][98][99][100][101][102][103], key events for cell permissivity and survival that are regulated by the antiviral factor histone deacetylase 6 (HDAC6) [91,94,[98][99][100][101][104][105][106][107][108].…”