The Association of HIV-1 Tat with Nuclei Is Regulated by Ca2+ Ions and Cytosolic Factors

Morgavi, Paola; Bonifaci, Neris; Pagani, Massimiliano; Costigliolo, Sara; Sitia, Roberto; Rubartelli, Anna

doi:10.1074/jbc.272.17.11256

Cited by 8 publications

(8 citation statements)

References 27 publications

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“…Synthetic Tat preparations were purified by reverse phase high pressure liquid chromatography yielding a purity of 96%. The biological activities of synthetic Tat were superimposable to those of natural Tat in different assays (20,21). Recombinant fibronectin type III repeat (Fn-III, from amino acids 1086 -1172) was a kind gift of L. Zardi (National Institute for Cancer Research, Genoa, Italy).…”

Section: Methodsmentioning

confidence: 99%

Involvement of Dihydropyridine-sensitive Calcium Channels in Human Dendritic Cell Function

Poggi¹,

Rubartelli²,

Zocchi³

1998

Journal of Biological Chemistry

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The entry of extracellular calcium in leukocytes mediates several cellular processes; however, unlike in excitable tissues, the underlying molecular mechanisms are poorly defined. In this paper we provide phenotypical and biochemical evidence that peripheral blood-derived human dendritic cells express dihydropyridine-sensitive calcium channels. Exposure to the dihydropyridine drug nifedipine, which binds L-type calcium channels blocking calcium influx, prevents two dendritic cell functions that are dependent on extracellular calcium entry: apoptotic body engulfment and interleukin-12 production induced by cross-linking of the surface lectin NKRP1A. Calcium-linked cellular functions in excitable tissues are mediated by voltage-dependent calcium channels, which participate in the regulation of action potential generation, muscle contraction, and secretion of hormones or neurotransmitters (1). Although in neurons multiple types of calcium channels, which can be distinguished by their pharmacological properties, are expressed, in skeletal and cardiac muscles the principal calcium channels are L-type (1, 2). These channels are composed of three transmembrane subunits (␣1C, ␥, and the ␣2␦ complex) and one cytoplasmic chain (the ␤1 chain). A spectrum of compounds, the dihydropyridine (DHP) 1 derivatives, which specifically bind with high affinity to the ␣1C chain of L-type channels (3, 4), regulating their functional state from blocking to opening, allows both the identification and the functional analysis of this class of molecules (1-4). Cytosolic calcium rise is an important signal also in nonexcitable cells, including immune cells, regulating fundamental processes such as activation, growth, and differentiation (5-7). Increase in free intracellular calcium concentration ([Ca 2ϩ ] i ) may result from calcium mobilization from either intracellular stores or extracellular medium or both (5). Unlike the mechanisms mediating mobilization from intracellular stores, the molecular structures mediating extracellular calcium influxes are still poorly characterized. Recently, the presence of functional calcium channels displaying DHP sensitivity has been observed in B lymphocytes (8), raising the possibility that similar structures are present also in nonexcitable cells. We have previously shown that some functions of dendritic cells (DC) are mediated by [Ca 2ϩ ] i increase. DC are professional antigen presenting cells able to endocytose and process soluble or particulated antigens (9, 10) and prime naive T lymphocytes (9). Activated DC produce IL-12, a cytokine that amplifies the immune response promoting the differentiation of the T helper 1 lymphocyte subset, which in turn substains the natural killer (NK) cell activity (11, 12). We reported that activation of DC by cross-linking of the surface lectin NKRP1A with consequent IL-12 production is accompanied by extracellular calcium influx (13); similarly, apoptotic body engulfment induces and is dependent on calcium entry in phagocytosing DC (10). Interestingly, the HIV-...

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Section: Methodsmentioning

confidence: 99%

Involvement of Dihydropyridine-sensitive Calcium Channels in Human Dendritic Cell Function

Poggi¹,

Rubartelli²,

Zocchi³

1998

Journal of Biological Chemistry

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“…In addition to being a transcriptional regulator of HIV-1 replication, intact and biologically active HIV-1 Tat secretes out of HIV-infected cells (Westendorp et al 1995; Xiao et al 2000) and Tat-expressing cells (Albini et al 1998b; Chang et al 1997; Ensoli et al 1990; Milani et al 1993; Morgavi et al 1997; Zauli et al 1993, 1995). In the central nervous system (CNS), Tat is detected in the brain of patients with HIV-associated dementia (Hudson et al 2000); it can derive from HIV-infected microglia/macrophages and astrocytes in the CNS or HIV-infected monocytes/macrophages and infiltrated CD4 + T lymphocytes (Banks et al 2005; Chang et al 1997; Chen et al 1995; Ensoli et al 1993).…”

Section: Introductionmentioning

confidence: 99%

“…In the central nervous system (CNS), Tat is detected in the brain of patients with HIV-associated dementia (Hudson et al 2000); it can derive from HIV-infected microglia/macrophages and astrocytes in the CNS or HIV-infected monocytes/macrophages and infiltrated CD4 + T lymphocytes (Banks et al 2005; Chang et al 1997; Chen et al 1995; Ensoli et al 1993). HIV-1 Tat secretion occurs through unconventional secretory pathways since the gene encoding Tat does not contain a signal sequence (Chang et al 1997; Morgavi et al 1997). Such alternative secretory pathways have been documented for other growth factors, such as interleukin-1β and basic epidermal growth factor (Morgavi et al 1997).…”

Section: Introductionmentioning

confidence: 99%

“…HIV-1 Tat secretion occurs through unconventional secretory pathways since the gene encoding Tat does not contain a signal sequence (Chang et al 1997; Morgavi et al 1997). Such alternative secretory pathways have been documented for other growth factors, such as interleukin-1β and basic epidermal growth factor (Morgavi et al 1997). Several studies including ours have demonstrated that HIV Tat or Tat-derived peptides are capable of entering cells cultured and transactivating the HIV LTR promoter (Bonifaci et al 1995; Frankel and Pabo 1988; Green et al 1989; Liu et al 2000; Mann and Frankel 1991; Viscidi et al 1989).…”

Section: Introductionmentioning

confidence: 99%

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Exosome-associated release, uptake, and neurotoxicity of HIV-1 Tat protein

Rahimian

2016

J. Neurovirol.

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HIV-1 Tat is an indispensible transactivator for HIV gene transcription and replication. It has been shown to exit cells as a free protein and enter neighboring cells or interact with surface receptors of neighboring cells to regulate gene expression and cell function. In this study, we report, for the first time, exosome-associated Tat release and uptake. Using a HIV-1 LTR-driven luciferase reporter-based cell assay and Western blotting or in combination with exosome inhibitor, OptiPrep gradient fractionation, and exosome depletion, we demonstrated significant presence of HIV-1 Tat in exosomes derived from Tat-expressing primary astrocytes, Tat-transfected U373.MG and 293T, and HIV-infected MT4. We further showed that exosome-associated Tat from Tat-expressing astrocytes was capable of causing neurite shortening and neuron death, further supporting that this new form of extracellular Tat is biologically active. Lastly, we constructed a Tat mutant deleted of its basic domain and determined the role of the basic domain in Tat trafficking into exosomes. Basic domain-deleted Tat exhibited no apparent effects on Tat trafficking into exosomes, while maintained its dominant-negative function in Tat-mediated LTR transactivation. Taken together, these results show a significant fraction of Tat is secreted and present in the form of exosomes and may contribute to the stability of extracellular Tat and broaden the spectrum of its target cells.

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“…In independent studies, Morgavi et al (54) found Ca 2 + to be required for Tat nuclear entry in vitro, apparently to activate essential cytosolic components. Ca 2 + -dependent tyrosine phosphorylation/dephosphorylation events appeared to be involved, whereby not Tat, but accessory proteins responsible for relaying Tat to the nucleus, were thought to be the targets of phosphorylation (see Fig.…”

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confidence: 99%

The HIV‐1 Tat Transactivator Protein: a Therapeutic Target?

Fulcher

Jans

2003

IUBMB Life

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The human immunodeficiency virus‐1 (HIV‐1), the causative agent of autoimmune deficiency syndrome (AIDS) is a major health problem world‐wide. Central to HIV infection is the transactivator protein Tat, that plays a critical role in the nucleus during the HIV infectious cycle, by binding the transactivation‐responsive region (TAR) and thereby enhancing transcriptional elongation. Tat appears to gain nuclear entry through a novel mechanism, independent of the normal cellular importin/Ran‐dependent pathways, and regulated by a cytoplasmic retention mechanism. Since blocking Tat nuclear import is likely to prevent HIV infection, detailed delineation of Tat's nuclear import pathway is critical to assessing its viability as a therapeutic target. Other feasible anti‐HIV therapies include approaches to inhibit Tat‐TAR interaction. IUBMB Life, 55: 669‐680, 2003

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The Association of HIV-1 Tat with Nuclei Is Regulated by Ca2+ Ions and Cytosolic Factors

Cited by 8 publications

References 27 publications

Involvement of Dihydropyridine-sensitive Calcium Channels in Human Dendritic Cell Function

Involvement of Dihydropyridine-sensitive Calcium Channels in Human Dendritic Cell Function

Exosome-associated release, uptake, and neurotoxicity of HIV-1 Tat protein

The HIV‐1 Tat Transactivator Protein: a Therapeutic Target?

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