Vpr protein of human immunodeficiency virus type 1 forms cation-selective channels in planar lipid bilayers.

Piller, Sabine C.; Ewart, Gary; Premkumar, Anita; Cox, G B; Gage, Peter W.

doi:10.1073/pnas.93.1.111

Cited by 116 publications

(99 citation statements)

References 22 publications

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“…Membrane-spanning domains inserted into lipid bilayers also give rise to similar conductance levels (24,(26)(27)(28). Vpr, another HIV-1 auxiliary protein, induces channel activity when inserted in lipid bilayers (29). In this case, activity occurs in bursts with conductance levels between 20 and 100 pS.…”

Section: N-7-oxanonyl-6-deoxy-dgjmentioning

confidence: 99%

The hepatitis C virus p7 protein forms an ion channel that is inhibited by long-alkyl-chain iminosugar derivatives

Pavlović

Neville²,

Argaud³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

333

302

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We show that hepatitis C virus (HCV) p7 protein forms ion channels in black lipid membranes. HCV p7 ion channels are inhibited by long-alkyl-chain iminosugar derivatives, which have antiviral activity against the HCV surrogate bovine viral diarrhea virus. HCV p7 presents a potential target for antiviral therapy.H epatitis C virus (HCV) is the major cause of chronic hepatitis with a significant risk of end-stage liver cirrhosis and hepatocellular carcinoma (1). HCV belongs to the family Flaviviridae, which consists of three genera: flaviviruses, pestiviruses, and hepaciviruses. In the absence of both a suitable small animal model and a reliable in vitro infectivity assay for HCV, potential antiviral drugs initially have been tested by using a related pestivirus, bovine viral diarrhea virus (BVDV) (2). BVDV in vitro infectivity assays were used to demonstrate that long-alkyl-chain iminosugar derivatives containing either the glucose analogue deoxynojirimycin (DNJ) or the galactose analogue deoxygalactonojirimycin (DGJ) are potent antiviral inhibitors (3).DNJ derivatives inhibit endoplasmic reticulum (ER) ␣-glucosidases I and II (4, 5), and this inhibition leads to the misfolding of many host-and virus-encoded glycoproteins, including the envelope glycoproteins of BVDV (6) and HCV (7). Previous experiments have shown that the antiviral effect of the longalkyl-chain derivative N-nonyl-DNJ (NN-DNJ) is more pronounced than that of the short-alkyl-chain derivative N-butyl-DNJ (NB-DNJ), although the latter achieves a more effective ER ␣-glucosidase inhibition in cellulo. In addition, long-alkylchain DGJ derivatives that are not recognized by and do not inhibit ER ␣-glucosidases also show potent antiviral activity (3). Therefore, ER ␣-glucosidase inhibition does not correlate directly with the observed antiviral effect and is ruled out as the sole antiviral mechanism.The additional mechanism of action apparently is associated with the length of the alkyl side chain, because the short-chain N-butyl-DGJ (NB-DGJ) shows no antiviral activity, whereas the long-alkyl-chain derivative NN-DGJ is a potent inhibitor (3).The predominant antiviral mechanism is proposed to be mediated directly or indirectly by an effect of the long-alkyl side chains on the membrane and͞or membrane proteins, because treatment with long-alkyl-chain iminosugars affects the dimerization of viral membrane glycoproteins and alters the membrane glycoprotein composition of secreted BVDV virions but does not influence either viral RNA replication or protein synthesis (3).We decided to investigate the small membrane-spanning protein p7 as a potential target of long-alkyl-chain iminosugar derivatives, because flaviviruses such as dengue virus and Japanese encephalitis virus (8), which do not contain p7, are not inhibited by long-alkyl-chain DGJ derivatives, whereas pestiviruses are (3). Pesti-and hepaciviruses both contain the p7 protein.Most functional data about p7 are derived from the pestivirus p7, a 70-aa protein very similar to HCV p7. Functional data hav...

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Section: N-7-oxanonyl-6-deoxy-dgjmentioning

confidence: 99%

The hepatitis C virus p7 protein forms an ion channel that is inhibited by long-alkyl-chain iminosugar derivatives

Pavlović

Neville²,

Argaud³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

333

302

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“…The Kcv protein of Paramecium bursaria chlorella virus forms a potassium channel (12), whereas the M2 protein of influenza virus forms a proton channel (19). Two other viral proteins, Vpu and Vpr of HIV, have also been reported to have channel activity (20,21). The functions of these ion channels vary among one another.…”

Section: Sars-cov Is a Newly Identified Coronavirus In Humans That Lementioning

confidence: 99%

Severe acute respiratory syndrome-associated coronavirus 3a protein forms an ion channel and modulates virus release

Zheng

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

286

395

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Fourteen ORFs have been identified in the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) genome. ORF 3a of SARS-CoV codes for a recently identified transmembrane protein, but its function remains unknown. In this study we confirmed the 3a protein expression and investigated its localization at the surface of SARS-CoV-infected or 3a-cDNA-transfected cells. Our experiments showed that recombinant 3a protein can form a homotetramer complex through interprotein disulfide bridges in 3a-cDNA-transfected cells, providing a clue to ion channel function. The putative ion channel activity of this protein was assessed in 3a-complement RNA-injected Xenopus oocytes by two-electrode voltage clamp. The results suggest that 3a protein forms a potassium sensitive channel, which can be efficiently inhibited by barium. After FRhK-4 cells were transfected with an siRNA, which is known to suppress 3a expression, followed by infection with SARS-CoV, the released virus was significantly decreased, whereas the replication of the virus in the infected cells was not changed. Our observation suggests that SARS-CoV ORF 3a functions as an ion channel that may promote virus release. This finding will help to explain the highly pathogenic nature of SARS-CoV and to develop new strategies for treatment of SARS infection. caused alarm all over the world. The newly discovered human coronavirus named SARS-associated coronavirus (SARS-CoV) was identified as the causative agent for this disease (1, 2). SARSCoV has a large single-positive-strand RNA genome that contains 14 ORFs. Some of these ORFs encode viral structural proteins, such as spike protein, membrane protein, small envelope protein, and nucleocapsid protein, as well as viral replicase and protease (3). Those proteins play important roles in viral infection and replication. However, functions for other ORFs are not clear. Therefore, identification and characterization of new functional proteins from the ORFs will be helpful for understanding the pathogenesis of SARS-CoV. Up to now there are still no effective drugs or vaccines against SARS-CoV. The identification of new viral proteins and the elucidation of their functions will provide potential targets for design of drugs or vaccines against SARS.Our previous work has revealed that ORF 3a of SARS-CoV is such a viral protein (4). Since then, other publications have concurred in this observation and have shown that it is a structural protein (5-8). ORF 3a is located between the S and E protein loci and encodes a protein of 274 aa. The only available information based on proteomics and immunoblotting suggests that 3a protein is structural in nature, but its localization, topology, and biological function have not been identified.A computed biology analysis of the amino acid sequence of the 3a protein revealed that it has low similarity with any other known protein. Its C-terminal region shares Ϸ50% similarity to Plasmodium calcium pump protein and to the Shewanella outer-membrane porin. Interestingly, comparison of ORFs ...

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“…Electrophysical Measurements with Artificial Membranes-Artificial lipid bilayers were made with phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) dissolved in ndecane and painted across a small aperture in the wall of a 2-ml Delrin cup separating cis and trans chambers containing salt solutions (23). The membranes formed in these experiments were made in two compositions, PS:PE:PC 2:2:1 and PE:PC 2:1.…”

Section: Methodsmentioning

confidence: 99%

The Cytotoxic Plant Protein, β-Purothionin, Forms Ion Channels in Lipid Membranes

Hughes¹,

Dennis²,

Whitecross³

et al. 2000

Journal of Biological Chemistry

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Thionins are small cysteine-containing, amphipathic plant proteins found in seeds and vegetative tissues of a number of plant genera. Many of them have been shown to be toxic to microorganisms such as fungi, yeast, and bacteria and also to mammalian cells. It has been suggested that thionins are present in seeds to protect them, and the germinating seedling, from attack by phytopathogenic microorganisms, but the mechanism by which they kill cells remains unclear. Using electrophysiological measurements, we have shown that ␤-purothionin from wheat flour can form cation-selective ion channels in artificial lipid bilayer membranes and in the plasmalemma of rat hippocampal neurons. We suggest that the generalized toxicity of thionins is due to their ability to generate ion channels in cell membranes, resulting in the dissipation of ion concentration gradients essential for the maintenance of cellular homeostasis.

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Vpr protein of human immunodeficiency virus type 1 forms cation-selective channels in planar lipid bilayers.

Cited by 116 publications

References 22 publications

The hepatitis C virus p7 protein forms an ion channel that is inhibited by long-alkyl-chain iminosugar derivatives

The hepatitis C virus p7 protein forms an ion channel that is inhibited by long-alkyl-chain iminosugar derivatives

Severe acute respiratory syndrome-associated coronavirus 3a protein forms an ion channel and modulates virus release

The Cytotoxic Plant Protein, β-Purothionin, Forms Ion Channels in Lipid Membranes

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