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Aging May 2022
Topics: Aging; HIV Infections; Humans; tat Gene Products, Human Immunodeficiency Virus
PubMed: 35622387
DOI: 10.18632/aging.204105 -
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 -
Methods (San Diego, Calif.) Jul 2001Manipulation of mammalian cells has been achieved by the transfection of expression vectors, microinjection, or diffusion of peptidyl mimetics. While these approaches... (Review)
Review
Manipulation of mammalian cells has been achieved by the transfection of expression vectors, microinjection, or diffusion of peptidyl mimetics. While these approaches have been somewhat successful, the classic manipulation methods are not easily regulated and can be laborious. One approach to circumvent these problems is the use of HIV TAT-mediated protein transduction. Although this technology was originally described in 1988, few improvements were reported in the subsequent 10 years. In the last few years, significant steps have been taken to advance this technology into a broadly applicable method that allows for the rapid introduction of full-length proteins into primary and transformed cells. The technology requires the synthesis of a fusion protein, linking the TAT transduction domain to the molecule of interest using a bacterial expression vector, followed by the purification of this fusion protein under either soluble or denaturing conditions. The purified fusion protein can be directly added to mammalian cell culture or injected in vivo into mice. Protein transduction occurs in a concentration-dependent manner, achieving maximum intracellular concentrations in less than 5 min, with nearly equal intracellular concentrations between all cells in the transduced population. Full-length TAT fusion proteins have been used to address a number of biological questions, relating to cell cycle progression, apoptosis, and cellular architecture. Described here are the fundamental requirements for the creation, isolation, and utilization of TAT-fusion proteins to affect mammalian cells. A detailed protocol for production and transduction of TAT-Cdc42 into primary cells is given to illustrate the technique.
Topics: Animals; Cells, Cultured; Gene Products, tat; HIV-1; Humans; Transcriptional Activation; Transduction, Genetic; Transformation, Genetic; Viral Fusion Proteins; tat Gene Products, Human Immunodeficiency Virus
PubMed: 11403574
DOI: 10.1006/meth.2001.1186 -
Advanced Drug Delivery Reviews Feb 2005The Tat protein of HIV-1 is a powerful transactivator of gene expression. By interacting with a structured RNA sequence at the 5' end of the viral mRNA, it promotes the... (Review)
Review
The Tat protein of HIV-1 is a powerful transactivator of gene expression. By interacting with a structured RNA sequence at the 5' end of the viral mRNA, it promotes the remodeling of chromatin and the recruitment of processive RNA polymerase complexes at the viral promoter. In addition to these transcriptional functions, a short amino acid motif, highly enriched in basic amino acids, promotes the export of the protein from the expressing cells. Once in the extracellular environment, the same basic domain of Tat binds to cell surface heparan sulfate proteoglycans; through this interaction, the protein is internalized by a variety of different cell types. Cellular internalization of Tat and Tat fusion proteins requires the integrity of cell membrane lipid rafts and mainly occurs through caveolar endocytosis. The Tat basic domain, when attached to large protein cargos, also mediates their efficient cellular internalization and can be thus utilized for transcellular protein transduction. This property has already been successfully exploited for the delivery of heterologous proteins, nanoparticles, liposomes, phage and viral vectors, and plasmid DNA. The biological significance of intercellular Tat trafficking in the context of viral infection still remains elusive.
Topics: Animals; Cell Membrane; Gene Products, tat; HIV-1; Humans; Protein Transport; Receptors, Cell Surface; Transcriptional Activation; tat Gene Products, Human Immunodeficiency Virus
PubMed: 15722166
DOI: 10.1016/j.addr.2004.10.011 -
Expert Opinion on Biological Therapy Mar 2011HIV-Tat protein displays an array of functions that are essential for HIV replication. The structural flexibility of Tat protein has been regarded as one of the unique... (Review)
Review
INTRODUCTION
HIV-Tat protein displays an array of functions that are essential for HIV replication. The structural flexibility of Tat protein has been regarded as one of the unique features responsible for sustaining diverse functions, from facilitated membrane-crossing ability to strong affinity for RNA binding.
AREAS COVERED
RNA binding ability and presence of multiple interacting domains in the same protein are very important properties of HIV-Tat protein. Tat protein has shown great ability to influence cellular and viral gene expression. We discuss the functions of HIV Tat protein, describing its structural significance, secretion and uptake of HIV Tat protein by immune cells, post-translational modifications and role of HIV Tat protein in HIV pathogenesis.
EXPERT OPINION
Perturbation in expression of many cytokines and chemokines by HIV-Tat protein exhibits downstream immune suppressive function as well as activation of several apoptotic genes. This explains the massive death of immune cells due to bystander effect of HIV Tat protein among HIV-infected patients.
Topics: Animals; Binding Sites; Gene Expression Regulation, Viral; Genome, Viral; Genotype; HIV-1; Humans; Immune Tolerance; Protein Conformation; Protein Processing, Post-Translational; RNA; RNA-Binding Proteins; Structure-Activity Relationship; Virus Replication; tat Gene Products, Human Immunodeficiency Virus
PubMed: 21204735
DOI: 10.1517/14712598.2011.546339 -
Cartilage Dec 2021Intra-articular drug delivery holds great promise for the treatment of joint diseases such as osteoarthritis. The objective of this study was to evaluate the TAT peptide...
OBJECTIVE
Intra-articular drug delivery holds great promise for the treatment of joint diseases such as osteoarthritis. The objective of this study was to evaluate the TAT peptide transduction domain (TAT-PTD) as a potential intra-articular drug delivery technology for synovial joints.
DESIGN
Experiments examined the ability of TAT conjugates to associate with primary chondrocytes and alter cellular function both and . Further experiments examined the ability of the TAT-PTD to bind to human osteoarthritic cartilage.
RESULTS
The results show that the TAT-PTD associates with chondrocytes, is capable of delivering siRNA for chondrocyte gene knockdown, and that the recombinant enzyme TAT-Cre is capable of inducing genetic recombination within the knee joint in a reporter mouse model. Last, binding studies show that osteoarthritic cartilage preferentially uptakes the TAT-PTD from solution.
CONCLUSIONS
The results suggest that the TAT-PTD is a promising delivery strategy for intra-articular therapeutics.
Topics: Animals; Cartilage; Chondrocytes; Gene Products, tat; Mice; Osteoarthritis; Technology
PubMed: 32954793
DOI: 10.1177/1947603520959392 -
Biochemical Pharmacology Nov 1999Tat proteins (trans-activating proteins) are present in all known lentiviruses and are early RNA binding proteins that regulate transcription. Tat from the human... (Review)
Review
Tat proteins (trans-activating proteins) are present in all known lentiviruses and are early RNA binding proteins that regulate transcription. Tat from the human immunodeficiency virus type-1 is a protein comprising 86 amino acids and encoded by 2 exons. The first 72 amino acids are encoded by exon 1 and exhibit full trans-activating activity. The second exon encodes a 14-amino-acid C-terminal sequence that is not required for trans-activation but does contain an RGD motif, which is important in binding to alphavbeta3 and alpha5beta1 integrins. Tat has an unusual property for a transcription factor; it can be released and enter cells freely, yet still retain its activity, enabling it to up-regulate a number of genes. Tat also has an angiogenic effect; it is a potent growth factor for Kaposi sarcoma-derived spindle cells, and, separately, it has been shown to bind to a specific receptor, Flk-1/KDR, on vascular smooth muscle cells, as well as to integrin-like receptors present on rat skeletal muscle cells and the lymphocyte cell line H9. It appears that the basic domain of tat is important, not only for translocation but also for nuclear localisation and trans-activation of cellular genes. As such, targeting of tat protein or, more simply, the basic domain provides great scope for therapeutic intervention in HIV-1 infection. There is also opportunity for tat to be used as a molecular tool; the protein can be manipulated to deliver non-permeable compounds into cells, an approach that already has been employed using ovalbumin, beta-galactosidase, horseradish peroxidase, and caspase-3.
Topics: Anti-HIV Agents; Cell Division; Gene Products, tat; HIV-1; HeLa Cells; Humans; Paracrine Communication; Transcription, Genetic; Transcriptional Activation; tat Gene Products, Human Immunodeficiency Virus
PubMed: 10535742
DOI: 10.1016/s0006-2952(99)00209-9 -
Neurotoxicity Research Oct 2009The Tat protein of the human immunodeficiency virus (HIV) has been implicated in the pathophysiology of the neurocognitive deficits associated with HIV infection. This... (Review)
Review
The Tat protein of the human immunodeficiency virus (HIV) has been implicated in the pathophysiology of the neurocognitive deficits associated with HIV infection. This is the earliest protein to be produced by the proviral DNA in the infected cell. The protein not only drives the regulatory regions of the virus but may also be actively released from the cell and then interact with the cell surface receptors of other uninfected cells in the brain leading to cellular dysfunction. It may also be taken up by these cells and can then activate a number of host genes. The Tat protein is highly potent and has the unique ability to travel along neuronal pathways. Importantly, its production is not impacted by the use of antiretroviral drugs once the proviral DNA has been formed. This article reviews the pleomorphic actions of Tat protein and the evidence supporting its central role in the neuropathogenesis of the HIV infection.
Topics: Animals; Brain Diseases; Gene Expression Regulation, Viral; Gene Products, tat; HIV Infections; Humans; Neuroglia; Neurons
PubMed: 19526283
DOI: 10.1007/s12640-009-9047-8 -
Leukemia & Lymphoma Nov 1996Tat protein of human immunodeficiency virus type-1 (HIV-1) plays a central role in viral replication and shows pleiotropic effects on the survival and growth of... (Review)
Review
Tat protein of human immunodeficiency virus type-1 (HIV-1) plays a central role in viral replication and shows pleiotropic effects on the survival and growth of different cell types. Remarkably, Tat represents the first example of a viral protein, that can also be actively secreted by infected cells and shows a cytokine-like activity on both HIV-1 infected and uninfected cells. We previously reported that the stable expression of tat cDNA rescues Jurkat cell lines from apoptosis induced by a variety of stimuli, such as serum withdrawal, engagement of fas antigen or even a productive infection with HIV-1. These findings suggested that Tat was able to modulate the expression of one or more gene(s) relevant for the control of cell survival/death. Consistently, Jurkat cells stably transfected with tat show an upregulated expression of bcl-2. It is still unsettled whether Tat affects cell survival and bcl-2 expression directly or indirectly, modulating the expression of other cellular genes involved in the control of cell survival or encoding for cytokines. Blocking experiments performed with anti-Tat neutralizing antibodies revealed that TAt increases bcl-2 expression and prevent lymphoid T cells from apoptosis by acting, at least in part, through an autocrine/paracrine loop. While high (nM-microM) concentrations of extracellular Tat display a cytotoxic activity on the antigen-mediated induction of T cell proliferation, low (pM) concentrations of Tat were able to protect both Jurkat cells and primary peripheral blood mononuclear cells from apoptosis. Significantly, pM concentrations of Tat were detected in the sera of some HIV-1 infected individuals as well as in the culture supernatant of HIV-1 infected cells, raising the possibility that these levels of Tat protein may be present physiologically in vivo. The potential relevance of Tat-mediated upregulation of bcl-2 for the pathogenesis of HIV-1 disease is discussed.
Topics: Gene Expression; Gene Products, tat; HIV Infections; HIV-1; Humans; Proto-Oncogene Proteins c-bcl-2; tat Gene Products, Human Immunodeficiency Virus
PubMed: 9031086
DOI: 10.3109/10428199609054864 -
Cell Biochemistry and Function 2005The authors have reviewed some biological properties of HIV-1 Tat protein, and have also reported some personal data. This viral regulatory protein is endowed with... (Review)
Review
The authors have reviewed some biological properties of HIV-1 Tat protein, and have also reported some personal data. This viral regulatory protein is endowed with multifunctional activities, acting as an endogenous factor in the infected cells and exogenously, on those uninfected. In particular, Tat-induced proliferation and differentiation of HIV target cells which promotes viral infection, is discussed in this review. However, exogenous Tat protein can sometimes also produce, directly or indirectly, damaging effects in different organs and host systems, such as myocardium, kidney, liver and central nervous system (CNS). For example some data also demonstrate an increase in the apoptotic index induced by Tat at various levels, including the immune system. The effective role of HIV-1 Tat protein in promoting viral replication and its high immunogenicity suggest useful employment of this protein for therapeutic or preventive vaccine preparations.
Topics: Gene Products, tat; HIV Infections; HIV-1; Humans; Virus Replication; tat Gene Products, Human Immunodeficiency Virus
PubMed: 15473004
DOI: 10.1002/cbf.1147