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Redox Biology Jun 2023This study was focused on exploring the role of the HIV-1 Tat protein in mediating microglial ferroptosis. Exposure of mouse primary microglial cells (mPMs) to HIV-1 Tat...
This study was focused on exploring the role of the HIV-1 Tat protein in mediating microglial ferroptosis. Exposure of mouse primary microglial cells (mPMs) to HIV-1 Tat protein resulted in induction of ferroptosis, which was characterized by increased expression of Acyl-CoA synthetase long-chain family member 4 (ACSL4), in turn, leading to increased generation of oxidized phosphatidylethanolamine, elevated levels of lipid peroxidation, upregulated labile iron pool (LIP) and ferritin heavy chain-1 (FTH1), decreased glutathione peroxidase-4 and mitochondrial outer membrane rupture. Also, inhibition of ferroptosis by ferrostatin-1 (Fer-1) or deferoxamine (DFO) treatment suppressed ferroptosis-related changes in mPMs. Similarly, the knockdown of ACSL4 by gene silencing also inhibited ferroptosis induced by HIV-1 Tat. Furthermore, increased lipid peroxidation resulted in increased release of proinflammatory cytokines, such as TNFα, IL6, and IL1β and microglial activation. Pretreatment of mPMs with Fer-1 or DFO further blocked HIV-1 Tat-mediated microglial activation in vitro and reduced the expression and release of proinflammatory cytokines. We identified miR-204 as an upstream modulator of ACSL4, which was downregulated in mPMs exposed to HIV-1 Tat. Transient transfection of mPMs with miR-204 mimics reduced the expression of ACSL4 while inhibiting HIV-1 Tat-mediated ferroptosis and the release of proinflammatory cytokines. These in vitro findings were further validated in HIV-1 transgenic rats as well as HIV + ve human brain samples. Overall, this study underscores a novel mechanism(s) underlying HIV-1 Tat-mediated ferroptosis and microglial activation involving miR-204-ACSL4 signaling.
Topics: Animals; Humans; Mice; Rats; Coenzyme A Ligases; Cytokines; Ferroptosis; Gene Products, tat; HIV-1; Microglia; MicroRNAs; Rats, Transgenic
PubMed: 37023693
DOI: 10.1016/j.redox.2023.102689 -
Aging May 2022
Topics: Aging; HIV Infections; Humans; tat Gene Products, Human Immunodeficiency Virus
PubMed: 35622387
DOI: 10.18632/aging.204105 -
Frontiers in Cellular and Infection... 2020HIV Tat protein is a critical protein that plays multiple roles in HIV pathogenesis. While its role as the transactivator of HIV transcription is well-established, other... (Review)
Review
HIV Tat protein is a critical protein that plays multiple roles in HIV pathogenesis. While its role as the transactivator of HIV transcription is well-established, other non-viral replication-associated functions have been described in several HIV-comorbidities even in the current antiretroviral therapy (ART) era. HIV Tat protein is produced and released into the extracellular space from cells with active HIV replication or from latently HIV-infected cells into neighboring uninfected cells even in the absence of active HIV replication and viral production due to effective ART. Neighboring uninfected and HIV-infected cells can take up the released Tat resulting in the upregulation of inflammatory genes and activation of pathways that leads to cytotoxicity observed in several comorbidities such as HIV associated neurocognitive disorder (HAND), HIV associated cardiovascular impairment, and accelerated aging. Thus, understanding how Tat modulates host and viral response is important in designing novel therapeutic approaches to target the chronic inflammatory effects of soluble viral proteins in HIV infection.
Topics: HIV Infections; HIV-1; Humans; tat Gene Products, Human Immunodeficiency Virus
PubMed: 32158701
DOI: 10.3389/fcimb.2020.00061 -
Nature May 2023Cellular processes are the product of interactions between biomolecules, which associate to form biologically active complexes. These interactions are mediated by...
Cellular processes are the product of interactions between biomolecules, which associate to form biologically active complexes. These interactions are mediated by intermolecular contacts, which if disrupted, lead to alterations in cell physiology. Nevertheless, the formation of intermolecular contacts nearly universally requires changes in the conformations of the interacting biomolecules. As a result, binding affinity and cellular activity crucially depend both on the strength of the contacts and on the inherent propensities to form binding-competent conformational states. Thus, conformational penalties are ubiquitous in biology and must be known in order to quantitatively model binding energetics for protein and nucleic acid interactions. However, conceptual and technological limitations have hindered our ability to dissect and quantitatively measure how conformational propensities affect cellular activity. Here we systematically altered and determined the propensities for forming the protein-bound conformation of HIV-1 TAR RNA. These propensities quantitatively predicted the binding affinities of TAR to the RNA-binding region of the Tat protein and predicted the extent of HIV-1 Tat-dependent transactivation in cells. Our results establish the role of ensemble-based conformational propensities in cellular activity and reveal an example of a cellular process driven by an exceptionally rare and short-lived RNA conformational state.
Topics: HIV Long Terminal Repeat; Nucleic Acid Conformation; RNA, Viral; tat Gene Products, Human Immunodeficiency Virus; Transcriptional Activation; HIV-1
PubMed: 37198487
DOI: 10.1038/s41586-023-06080-x -
FEMS Microbiology Letters Jun 2018The Tat machinery catalyzes the transport of folded proteins across the cytoplasmic membrane in bacteria and the thylakoid membrane in plants. Transport occurs only in... (Review)
Review
The Tat machinery catalyzes the transport of folded proteins across the cytoplasmic membrane in bacteria and the thylakoid membrane in plants. Transport occurs only in the presence of an electric field (Δψ) and/or a pH (ΔpH) gradient, and thus, Tat transport is considered to be dependent on the proton motive force (pmf). This presents a fundamental and major challenge, namely, that the Tat system catalyzes the movement of large folded protein cargos across a membrane without collapse of ion gradients. Current models argue that the active translocon assembles de novo for each cargo transported, thus providing an effective gating mechanism to minimize ion leakage. A limited structural understanding of the intermediates occurring during transport and the role of the pmf in stabilizing and/or driving this process have hindered the development of more detailed models. A fundamental question that remains unanswered is whether the pmf is actually 'consumed', providing an energetic driving force for transport, or alternatively, whether its presence is instead necessary to provide the appropriate environment for the translocon components to become active. Including addressing this issue in greater detail, we explore a series of additional questions that challenge current models, and, hopefully, motivate future work.
Topics: Bacteria; Gene Products, tat; Hydrogen-Ion Concentration; Membrane Potentials; Membrane Transport Proteins; Protein Folding; Protein Sorting Signals; Protein Transport; Proton-Motive Force
PubMed: 29897510
DOI: 10.1093/femsle/fny123 -
Medical Microbiology and Immunology Apr 2019Human immunodeficiency virus type 1 (HIV-1) encodes a transactivator of transcription (Tat) protein, which has several functions that promote viral replication,... (Review)
Review
Human immunodeficiency virus type 1 (HIV-1) encodes a transactivator of transcription (Tat) protein, which has several functions that promote viral replication, pathogenesis, and disease. Amino acid variation within Tat has been observed to alter the functional properties of Tat and, depending on the HIV-1 subtype, may produce Tat phenotypes differing from viruses' representative of each subtype and commonly used in in vivo and in vitro experimentation. The molecular properties of Tat allow for distinctive functional activities to be determined such as the subcellular localization and other intracellular and extracellular functional aspects of this important viral protein influenced by variation within the Tat sequence. Once Tat has been transported into the nucleus and becomes engaged in transactivation of the long terminal repeat (LTR), various Tat variants may differ in their capacity to activate viral transcription. Post-translational modification patterns based on these amino acid variations may alter interactions between Tat and host factors, which may positively or negatively affect this process. In addition, the ability of HIV-1 to utilize or not utilize the transactivation response (TAR) element within the LTR, based on genetic variation and cellular phenotype, adds a layer of complexity to the processes that govern Tat-mediated proviral DNA-driven transcription and replication. In contrast, cytoplasmic or extracellular localization of Tat may cause pathogenic effects in the form of altered cell activation, apoptosis, or neurotoxicity. Tat variants have been shown to differentially induce these processes, which may have implications for long-term HIV-1-infected patient care in the antiretroviral therapy era. Future studies concerning genetic variation of Tat with respect to function should focus on variants derived from HIV-1-infected individuals to efficiently guide Tat-targeted therapies and elucidate mechanisms of pathogenesis within the global patient population.
Topics: Genetic Variation; HIV Infections; HIV-1; Host-Pathogen Interactions; Humans; Transcription, Genetic; tat Gene Products, Human Immunodeficiency Virus
PubMed: 30834965
DOI: 10.1007/s00430-019-00583-z -
Viruses Apr 2020The human immunodeficiency virus type 1 (HIV) establishes a chronic infection that can be well controlled, but not cured, by combined antiretroviral therapy (cART).... (Review)
Review
The human immunodeficiency virus type 1 (HIV) establishes a chronic infection that can be well controlled, but not cured, by combined antiretroviral therapy (cART). Interventions have been explored to accomplish a functional cure, meaning that a patient remains infected but HIV is undetectable in the blood, with the aim of allowing patients to live without cART. Tat, the viral transactivator of transcription protein, plays a critical role in controlling HIV transcription, latency, and viral rebound following the interruption of cART treatment. Therefore, a logical approach for controlling HIV would be to block Tat. Tackling Tat with inhibitors has been a difficult task, but some recent discoveries hold promise. Two anti-HIV proteins, Nullbasic (a mutant of Tat) and HT1 (a fusion of HEXIM1 and Tat functional domains) inhibit viral transcription by interfering with the interaction of Tat and cellular factors. Two small molecules, didehydro-cortistatin A (dCA) and triptolide, inhibit Tat by different mechanisms: dCA through direct binding and triptolide through enhanced proteasomal degradation. Finally, two Tat-based vaccines under development elicit Tat-neutralizing antibodies. These vaccines have increased the levels of CD4 cells and reduced viral loads in HIV-infected people, suggesting that the new vaccines are therapeutic. This review summarizes recent developments of anti-Tat agents and how they could contribute to a functional cure for HIV.
Topics: Animals; Anti-HIV Agents; Gene Expression Regulation, Viral; HIV Infections; HIV-1; Host-Pathogen Interactions; Humans; RNA-Binding Proteins; Recombinant Fusion Proteins; Transcription Factors; Transcription, Genetic; Virus Replication; tat Gene Products, Human Immunodeficiency Virus
PubMed: 32276443
DOI: 10.3390/v12040415 -
Current Opinion in Structural Biology Aug 2014The Tat protein transport system is found in the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. Unusually, the Tat system... (Review)
Review
The Tat protein transport system is found in the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. Unusually, the Tat system translocates proteins only after they have folded. Proteins are targeted to the Tat system by specific N-terminal signal peptides. High resolution structures have recently been determined for the TatA and TatC proteins that form the Tat translocation site. These structures provide a molecular framework for understanding the mechanism of Tat transport. The interactions between TatC and the signal peptide of the substrate protein can be provisionally modelled. However, the way that TatA and TatC combine in the active translocation site remains to be definitively established.
Topics: Gene Products, tat; Protein Sorting Signals; Protein Transport
PubMed: 24709396
DOI: 10.1016/j.sbi.2014.03.003 -
Journal of Neurovirology Feb 2021The transactivator of transcription (Tat) is a key HIV regulatory protein. We aimed to identify the frequency of key polymorphisms in HIV-1C compared with HIV-1B Tat... (Observational Study)
Observational Study
The transactivator of transcription (Tat) is a key HIV regulatory protein. We aimed to identify the frequency of key polymorphisms in HIV-1C compared with HIV-1B Tat protein, chiefly in the cysteine-, arginine-, and glutamine-rich domains and identify novel point mutations in HIV-1B and C sequences from Southern Brazil. This study was the first to investigate the genetic diversity and point mutations within HIV-1 Tat C in a Brazilian cohort. This was an observational, cross-sectional study, which included sequences of HIV-1B (n = 20) and HIV-1C (n = 21) from Southern Brazil. Additionally, 344 HIV-1C sequences were obtained from the Los Alamos database: 29 from Brazil and 315 from Africa, Asia, and Europe. The frequency of C31S substitution on HIV-1 Tat C in Brazil was 82% vs. 10% in the HIV-1B group (p < 0.0001). The frequency of the R57S substitution among the HIV-1C sequences from Brazil was 74% vs. 20% in HIV-1B (p = 0.004), and that of substitution Q63E in HIV-1C was 80% and 20% in HIV-1B (p < 0.0001). The mutation P60Q was more frequent in HIV-1B than in HIV-1C (55% and 6.12%, respectively, p < 0.0001)). Novel point mutations in the HIV-1C and B Tat functional domains were described. The frequency of C31S and other key point mutations in HIV-1 Tat C in Brazil were similar to those described in Africa, although lower than those in India. The Tat-B and C sequences found in Southern Brazil are consistent with biological differences and have potential implications for HIV-1 subtype pathogenesis.
Topics: Adult; Brazil; Cross-Sectional Studies; Female; HIV-1; Humans; Male; Middle Aged; Polymorphism, Single Nucleotide; tat Gene Products, Human Immunodeficiency Virus
PubMed: 33462791
DOI: 10.1007/s13365-020-00935-z -
Pharmacology & Therapeutics Mar 2018HIV-associated neurocognitive disorder (HAND) remains highly prevalent in HIV infected individuals and represents a special group of neuropathological disorders, which... (Review)
Review
HIV-associated neurocognitive disorder (HAND) remains highly prevalent in HIV infected individuals and represents a special group of neuropathological disorders, which are associated with HIV-1 viral proteins, such as transactivator of transcription (Tat) protein. Cocaine abuse increases the incidence of HAND and exacerbates its severity by enhancing viral replication. Perturbation of dopaminergic transmission has been implicated as a risk factor of HAND. The presynaptic dopamine (DA) transporter (DAT) is essential for DA homeostasis and dopaminergic modulation of the brain function including cognition. Tat and cocaine synergistically elevate synaptic DA levels by acting directly on human DAT (hDAT), ultimately leading to dysregulation of DA transmission. Through integrated computational modeling and experimental validation, key residues have been identified in hDAT that play a critical role in Tat-induced inhibition of DAT and induce transporter conformational transitions. This review presents current information regarding neurological changes in DAT-mediated dopaminergic system associated with HIV infection, DAT-mediated adaptive responses to Tat as well as allosteric modulatory effects of novel compounds on hDAT. Understanding the molecular mechanisms by which Tat induces DAT-mediated dysregulation of DA system is of great clinical interest for identifying new targets for an early therapeutic intervention for HAND.
Topics: AIDS Dementia Complex; Animals; Dopamine; Dopamine Plasma Membrane Transport Proteins; Humans; tat Gene Products, Human Immunodeficiency Virus
PubMed: 28987321
DOI: 10.1016/j.pharmthera.2017.10.007