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FASEB Journal : Official Publication of... Mar 2020HIV-1 Tat is essential for HIV-1 replication and appears to play an important role in the pathogenesis of HIV-associated neurological complications. Secreted from...
HIV-1 Tat is essential for HIV-1 replication and appears to play an important role in the pathogenesis of HIV-associated neurological complications. Secreted from infected or transfected cells, Tat has the extraordinary ability to cross the plasma membrane. In the brain, Tat can be taken up by CNS cells via receptor-mediated endocytosis. Following endocytosis and its internalization into endolysosomes, Tat must be released in order for it to activate the HIV-1 LTR promoter and facilitate HIV-1 viral replication in the nucleus. However, the underlying mechanisms whereby Tat escapes endolysosomes remain unclear. Because Tat disrupts intracellular calcium homeostasis, we investigated the involvement of calcium in Tat endolysosome escape and subsequent LTR transactivation. We demonstrated that chelating endolysosome calcium with high-affinity rhodamine-dextran or chelating cytosolic calcium with BAPTA-AM attenuated Tat endolysosome escape and LTR transactivation. Significantly, we demonstrated that pharmacologically blocking and knocking down the endolysosome-resident two-pore channels (TPCs) attenuated Tat endolysosome escape and LTR transactivation. This calcium-mediated effect appears to be selective for TPCs because knocking down TRPML1 calcium channels was without effect. Our findings suggest that calcium released from TPCs is involved in Tat endolysosome escape and subsequent LTR transactivation. TPCs might represent a novel therapeutic target against HIV-1 infection and HIV-associated neurological complications.
Topics: Calcium; Cell Line, Tumor; Gene Expression Regulation, Viral; Gene Products, tat; HIV Long Terminal Repeat; HIV-1; Humans; Immunoblotting; Lysosomes; RNA, Small Interfering; Virus Replication
PubMed: 31950548
DOI: 10.1096/fj.201902534R -
Oncotarget Apr 2017The human immunodeficiency virus type I (HIV-1) has developed several strategies to condition the host environment to promote viral replication and spread. Viral... (Review)
Review
The human immunodeficiency virus type I (HIV-1) has developed several strategies to condition the host environment to promote viral replication and spread. Viral proteins have evolved to perform multiple functions, aiding in the replication of the viral genome and modulating the cellular response to the infection. Tat is a small, versatile, viral protein that controls transcription of the HIV genome, regulates cellular gene expression and generates a permissive environment for viral replication by altering the immune response and facilitating viral spread to multiple tissues. Studies carried out utilizing biochemical, cellular, and genomic approaches show that the expression and activity of hundreds of genes and multiple molecular networks are modulated by Tat via multiple mechanisms.
Topics: Animals; Apoptosis; Disease Susceptibility; Gene Expression Regulation; Gene Expression Regulation, Viral; HIV Infections; HIV-1; Host-Pathogen Interactions; Humans; Immunomodulation; MicroRNAs; Protein Transport; Transcriptional Activation; tat Gene Products, Human Immunodeficiency Virus
PubMed: 28187438
DOI: 10.18632/oncotarget.15174 -
Cell Reports Jul 2021Many neurological disorders show an increased prevalence of GluA2-lacking, Ca-permeable AMPA receptors (CP-AMPARs), which dramatically alters synaptic function. However,...
Many neurological disorders show an increased prevalence of GluA2-lacking, Ca-permeable AMPA receptors (CP-AMPARs), which dramatically alters synaptic function. However, the molecular mechanism underlying this distinct synaptic plasticity remains enigmatic. Here, we show that nerve injury potentiates postsynaptic, but not presynaptic, CP-AMPARs in the spinal dorsal horn via α2δ-1. Overexpressing α2δ-1, previously regarded as a Ca channel subunit, augments CP-AMPAR levels at the cell surface and synapse. Mechanistically, α2δ-1 physically interacts with both GluA1 and GluA2 via its C terminus, inhibits the GluA1/GluA2 heteromeric assembly, and increases GluA2 retention in the endoplasmic reticulum. Consequently, α2δ-1 diminishes the availability and synaptic expression of GluA1/GluA2 heterotetramers in the spinal cord in neuropathic pain. Inhibiting α2δ-1 with gabapentin or disrupting the α2δ-1-AMPAR complex fully restores the intracellular assembly and synaptic dominance of heteromeric GluA1/GluA2 receptors. Thus, α2δ-1 is a pivotal AMPAR-interacting protein that controls the subunit composition and Ca permeability of postsynaptic AMPARs.
Topics: Adolescent; Adult; Animals; Calcium; Cell Membrane Permeability; Endoplasmic Reticulum; Female; Gabapentin; Gene Products, tat; HEK293 Cells; Humans; Male; Neuralgia; Peptides; Phenotype; Protein Binding; Protein Subunits; Rats, Sprague-Dawley; Receptors, AMPA; Spinal Cord; Synapses; Young Adult; Rats
PubMed: 34289359
DOI: 10.1016/j.celrep.2021.109396 -
Cell Reports Mar 2023A successful HIV-1 cure strategy may require enhancing HIV-1 latency to silence HIV-1 transcription. Modulators of gene expression show promise as latency-promoting...
A successful HIV-1 cure strategy may require enhancing HIV-1 latency to silence HIV-1 transcription. Modulators of gene expression show promise as latency-promoting agents in vitro and in vivo. Here, we identify Su(var)3-9, enhancer-of-zeste, and trithorax (SET) and myeloid, Nervy, and DEAF-1 (MYND) domain-containing protein 5 (SMYD5) as a host factor required for HIV-1 transcription. SMYD5 is expressed in CD4 T cells and activates the HIV-1 promoter with or without the viral Tat protein, while knockdown of SMYD5 decreases HIV-1 transcription in cell lines and primary T cells. SMYD5 associates in vivo with the HIV-1 promoter and binds the HIV trans-activation response (TAR) element RNA and Tat. Tat is methylated by SMYD5 in vitro, and in cells expressing Tat, SMYD5 protein levels are increased. The latter requires expression of the Tat cofactor and ubiquitin-specific peptidase 11 (USP11). We propose that SMYD5 is a host activator of HIV-1 transcription stabilized by Tat and USP11 and, together with USP11, a possible target for latency-promoting therapy.
Topics: HIV-1; Lysine; Methyltransferases; RNA; RNA, Viral; tat Gene Products, Human Immunodeficiency Virus; Transcription, Genetic
PubMed: 36897778
DOI: 10.1016/j.celrep.2023.112234 -
International Journal of Molecular... Jan 2024Each time the virus starts a new round of expression/replication, even under effective antiretroviral therapy (ART), the transactivator of viral transcription Tat is one... (Review)
Review
Each time the virus starts a new round of expression/replication, even under effective antiretroviral therapy (ART), the transactivator of viral transcription Tat is one of the first HIV-1 protein to be produced, as it is strictly required for HIV replication and spreading. At this stage, most of the Tat protein exits infected cells, accumulates in the extracellular matrix and exerts profound effects on both the virus and neighbor cells, mostly of the innate and adaptive immune systems. Through these effects, extracellular Tat contributes to the acquisition of infection, spreading and progression to AIDS in untreated patients, or to non-AIDS co-morbidities in ART-treated individuals, who experience inflammation and immune activation despite virus suppression. Here, we review the role of extracellular Tat in both the virus life cycle and on cells of the innate and adaptive immune system, and we provide epidemiological and experimental evidence of the importance of targeting Tat to block residual HIV expression and replication. Finally, we briefly review vaccine studies showing that a therapeutic Tat vaccine intensifies ART, while its inclusion in a preventative vaccine may blunt escape from neutralizing antibodies and block early events in HIV acquisition.
Topics: Humans; HIV Infections; HIV-1; tat Gene Products, Human Immunodeficiency Virus; Antibodies, Neutralizing; Vaccines
PubMed: 38338977
DOI: 10.3390/ijms25031704 -
Current Topics in Microbiology and... 2015Antiretroviral therapy (ART) potently suppresses HIV-1 replication, but the virus persists in quiescent infected CD4(+)T cells as a latent integrated provirus, and... (Review)
Review
Antiretroviral therapy (ART) potently suppresses HIV-1 replication, but the virus persists in quiescent infected CD4(+)T cells as a latent integrated provirus, and patients must indefinitely remain on therapy. If ART is terminated, these integrated proviruses can reactivate, driving new rounds of infection. A functional cure for HIV requires eliminating low-level ongoing viral replication that persists in certain tissue sanctuaries and preventing viral reactivation. The HIV Tat protein plays an essential role in HIV transcription by recruiting the kinase activity of the P-TEFb complex to the viral mRNA's stem-bulge-loop structure, TAR, activating transcriptional elongation. Because the Tat-mediated transactivation cascade is critical for robust HIV replication, the Tat/TAR/P-TEFb complex is one of the most attractive targets for drug development. Importantly, compounds that interfere with transcription could impair viral reactivation, low-level ongoing replication, and replenishment of the latent reservoir, thereby reducing the size of the latent reservoir pool. Here, we discuss the potential importance of transcriptional inhibitors in the treatment of latent HIV-1 disease and review recent findings on targeting Tat, TAR, and P-TEFb individually or as part of a complex. Finally, we discuss the impact of extracellular Tat in HIV-associated neurocognitive disorders and cancers.
Topics: Acquired Immunodeficiency Syndrome; Anti-HIV Agents; HIV Long Terminal Repeat; HIV-1; Humans; Positive Transcriptional Elongation Factor B; tat Gene Products, Human Immunodeficiency Virus
PubMed: 25731772
DOI: 10.1007/82_2015_435 -
Molecules (Basel, Switzerland) Mar 2020The proteasome is a pivotal element of controlled proteolysis, responsible for the catabolic arm of proteostasis. By inducing apoptosis, small molecule inhibitors of...
The proteasome is a pivotal element of controlled proteolysis, responsible for the catabolic arm of proteostasis. By inducing apoptosis, small molecule inhibitors of proteasome peptidolytic activities are successfully utilized in treatment of blood cancers. However, the clinical potential of proteasome activation remains relatively unexplored. In this work, we introduce short TAT peptides derived from HIV-1 Tat protein and modified with synthetic turn-stabilizing residues as proteasome agonists. Molecular docking and biochemical studies point to the α1/α2 pocket of the core proteasome α ring as the binding site of TAT peptides. We postulate that the TATs' pharmacophore consists of an N-terminal basic pocket-docking "activation anchor" connected via a β turn inducer to a C-terminal "specificity clamp" that binds on the proteasome α surface. By allosteric effects-including destabilization of the proteasomal gate-the compounds substantially augment activity of the core proteasome in vitro. Significantly, this activation is preserved in the lysates of cultured cells treated with the compounds. We propose that the proteasome-stimulating TAT pharmacophore provides an attractive lead for future clinical use.
Topics: Allosteric Regulation; Binding Sites; Cell Line, Tumor; Chymotrypsin; Cytoplasm; Humans; Microscopy, Atomic Force; Molecular Docking Simulation; Peptide Hydrolases; Peptides; Proteasome Endopeptidase Complex; tat Gene Products, Human Immunodeficiency Virus
PubMed: 32235805
DOI: 10.3390/molecules25061439 -
Viruses Oct 2021The HIV-1 Tat protein interacts with TAR RNA and recruits CDK9/cyclin T1 and other host factors to induce HIV-1 transcription. Thus, Tat-TAR RNA interaction, which is...
The HIV-1 Tat protein interacts with TAR RNA and recruits CDK9/cyclin T1 and other host factors to induce HIV-1 transcription. Thus, Tat-TAR RNA interaction, which is unique for HIV-1, represents an attractive target for anti-HIV-1 therapeutics. To target Tat-TAR RNA interaction, we used a crystal structure of acetylpromazine bound to the bulge of TAR RNA, to dock compounds from the Enamine database containing over two million individual compounds. The docking procedure identified 173 compounds that were further analyzed for the inhibition of HIV-1 infection. The top ten inhibitory compounds with IC ≤ 6 µM were selected and the three least toxic compounds, T6780107 (IC = 2.97 μM), T0516-4834 (IC = 0.2 μM) and T5628834 (IC = 3.46 μM), were further tested for HIV-1 transcription inhibition. Only the T0516-4834 compound showed selective inhibition of Tat-induced HIV-1 transcription, whereas the T6780107 compound inhibited equally basal and Tat-induced transcription and the T5628834 compound only inhibited basal HIV-1 transcription. The compounds were tested for the inhibition of translation and showed minimal (<25%) effect. The T0516-4834 compound also showed the strongest inhibition of HIV-1 RNA expression and p24 production in CEM T cells and peripheral blood mononuclear cells infected with HIV-1 IIIB. Of the three compounds, only the T0516-4834 compound significantly disrupted Tat-TAR RNA interaction. Additionally, of the three tested compounds, T5628834 and, to a lesser extent, T0516-4834 disrupted Tat-CDK9/cyclin T1 interaction. None of the three compounds showed significant inhibition of the cellular CDK9 and cyclin T1 levels. In silico modelling showed that the T0516-4834 compound interacted with TAR RNA by binding to the bulge formed by U23, U25, C39, G26,C39 and U40 residues. Taken together, our study identified a novel benzoxazole compound that disrupted Tat-TAR RNA interaction and inhibited Tat-induced transcription and HIV-1 infection, suggesting that this compound might serve as a new lead for anti-HIV-1 therapeutics.
Topics: Cyclin T; Cyclin-Dependent Kinase 9; Gene Expression; Gene Expression Regulation, Viral; HEK293 Cells; HIV Infections; HIV Long Terminal Repeat; HIV-1; Humans; Leukocytes, Mononuclear; Molecular Docking Simulation; Phosphorylation; Protein Binding; RNA, Viral; Small Molecule Libraries; Virus Replication; tat Gene Products, Human Immunodeficiency Virus
PubMed: 34696435
DOI: 10.3390/v13102004 -
BMB Reports Apr 2023Thioredoxin-like protein 1 (TXNL1), one of the thioredoxin superfamily known as redox-regulator, plays an essential in maintaining cell survival via various antioxidant...
Thioredoxin-like protein 1 (TXNL1), one of the thioredoxin superfamily known as redox-regulator, plays an essential in maintaining cell survival via various antioxidant and anti-apoptotic mechanisms. It is well known that relationship between ischemia and oxidative stress, however, the role of TXNL1 protein in ischemic damage has not been fully investigated. In the present study, we aimed to determine the protective role of TXNL1 against on ischemic injury in vitro and in vivo using cell permeable Tat-TXNL1 fusion protein. Transduced Tat-TXNL1 inhibited ROS production and cell death in HO-exposed hippocampal neuronal (HT-22) cells and modulated MAPKs and Akt activation, and pro-apoptotic protein expression levels in the cells. In an ischemia animal model, Tat-TXNL1 markedly decreased hippocampal neuronal cell death and the activation of astrocytes and microglia. These findings indicate that cell permeable Tat-TXNL1 protects against oxidative stress in vitro and in vivo ischemic animal model. Therefore, we suggest Tat-TXNL1 can be a potential therapeutic protein for ischemic injury. [BMB Reports 2023; 56(4): 234-239].
Topics: Animals; Hydrogen Peroxide; Cell Line; Apoptosis; Oxidative Stress; Gene Products, tat; Ischemia; Thioredoxins; Brain Injuries; Recombinant Fusion Proteins
PubMed: 36571143
DOI: 10.5483/BMBRep.2022-0184 -
Molecular Neurobiology Feb 2021HIV infection and drugs of abuse induce oxidative stress and redox imbalance, which cause neurodegeneration. The mechanisms by which HIV infection and cocaine...
HIV infection and drugs of abuse induce oxidative stress and redox imbalance, which cause neurodegeneration. The mechanisms by which HIV infection and cocaine consumption affect astrocyte energy metabolism, and how this leads to neurodegenerative dysfunction, remain poorly understood. Presently, we investigated how oxidative injury causes the depletion of energy resources and glutathione synthetase (GSS), which in turn activates 5' AMP-activated protein kinase (AMPK), glycolytic enzymes, and mitochondrial biogenesis, finally resulting in nuclear factor erythroid (NRF) transcription in astrocytes. Both human primary astrocytes incubated with HIV-1 Tat protein in vitro and HIV-inducible Tat (iTat) mice exposed to cocaine showed decreased levels of GSS and increased superoxide dismutase (SOD) levels. These changes, in turn, significantly activated AMPK and raised the concentrations of several glycolytic enzymes, along with oxidative phosphorylation, the mitochondrial biogenesis of peroxisome proliferator-activated receptor-γ coactivator (PGC-1α) and mitochondrial transcription factor (TFAM), and Nrf1 and Nrf2 gene transcription and protein expression. Moreover, neurons exposed to HIV-1Tat/cocaine-conditioned media showed reductions in dendritic formation, spine density, and neuroplasticity compared with control neurons. These results suggest that redox inhibition of GSS altered AMPK activation and mitochondrial biogenesis to influence Nrf transcription. These processes are important components of the astrocyte signaling network regulating brain energy metabolism in HIV-positive cocaine users. In conclusion, HIV-1 Tat alters redox inhibition, thus increasing glycolytic metabolic profiles and mitochondrial biogenesis, leading to Nrf transcription, and ultimately impacting astrocyte energy resource and metabolism. Cocaine exacerbated these effects, leading to a worsening of neurodegeneration.
Topics: AMP-Activated Protein Kinases; Animals; Astrocytes; Brain; Cells, Cultured; Cocaine; Dendritic Spines; Energy Metabolism; Gene Expression Regulation; Glycolysis; Humans; Male; Mice, Transgenic; NF-E2-Related Factor 2; Nerve Degeneration; Neuronal Plasticity; Nuclear Respiratory Factor 1; Organelle Biogenesis; Oxidation-Reduction; Oxidative Phosphorylation; Transcription, Genetic; tat Gene Products, Human Immunodeficiency Virus
PubMed: 32978730
DOI: 10.1007/s12035-020-02131-w