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Jimah JR, Hinshaw JE. Structural Insights into the Mechanism of Dynamin Superfamily Proteins. Trends Cell Biol 2019; 29:257-273. [DOI: 10.1016/j.tcb.2018.11.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 10/30/2018] [Accepted: 11/02/2018] [Indexed: 12/28/2022]
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Matveeva OV, Chumakov PM. Defects in interferon pathways as potential biomarkers of sensitivity to oncolytic viruses. Rev Med Virol 2018; 28:e2008. [PMID: 30209859 PMCID: PMC6906582 DOI: 10.1002/rmv.2008] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 07/26/2018] [Accepted: 08/03/2018] [Indexed: 12/18/2022]
Abstract
Increased sensitivity of cancer cells to viruses is a prerequisite for the success of oncolytic virotherapy. One of the major causes of such a phenotype is the disruption of innate antiviral defenses associated with dysfunction of type 1 interferons (IFNs) that permits unlimited replication of viruses in cancer cells. Defects in IFN pathways help cancer progression by providing additional advantages to tumor cells. However, while these defects promote the survival and accelerated proliferation of malignant cells, they facilitate viral replication and thus enhance the efficiency of viral oncolysis. This review describes a broad spectrum of defects in genes that participate in IFN induction and IFN response pathways. Expression levels and/or functional activities of these genes are frequently low or absent in cancer cells, making them sensitive to virus infection. Therefore, certain specific defects in IFN signaling cascades might serve as potential biomarkers to help in identifying individual cancer patients who are likely to benefit from oncolytic virotherapy.
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Affiliation(s)
| | - Peter M Chumakov
- Engelhardt Institute of Molecular Biology, Moscow, Russia.,Chumakov Federal Scientific Center for Research and Development of Immune-and-Biological Products, Moscow, Russia
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3
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Hamad M, Amen O, Mahmoud M, Hassanin O, Saif-Edin M. Effectiveness of different avian influenza (H5) vaccination regimens in layer chickens on the humoral immune response and interferon-alpha signalling immune marker. Vet Res Commun 2018; 42:145-152. [PMID: 29619666 DOI: 10.1007/s11259-018-9717-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Accepted: 03/09/2018] [Indexed: 12/15/2022]
Abstract
Avian influenza (AI) vaccines are widely used to control and eliminate the ongoing avian influenza virus epidemic in Egypt. A strict vaccination policy with inactivated AI vaccines has been widely applied, however the virus still circulating, evolving and causing great negative impact to the poultry sector in Egypt. Therefore, an updated poultry vaccination policy using different vaccine technologies might be valuable as an innovative additional control strategy of AIV in Egypt. In the present study, the effectiveness of different avian influenza (AI) vaccination schedules was evaluated in 300 commercial layer chicks (ISA White) using either the oil-emulsion baculovirus-H5-prototype vaccine (baculovirus-H5 prototype) or turkey herpesvirus (HVT) vector vaccine containing the hemagglutinin (HA) gene from H5N1 strain (rHVT-H5), applied alone or in combination and in different settings. Vaccination with either two injections of the baculovirus-H5 prototype, a single injection of rHVT-H5 or priming with rHVT-H5 at 1 day old followed by boosting with the baculovirus-H5 prototype induced AI-HI protective antibody responses starting as early as 3 to 4 weeks of age and lasting up to the end of the rearing period (16 weeks). A single vaccination with the baculovirus-H5 prototype did not generate a protective antibody titre for the entire rearing period. Furthermore, the present study elucidated that vaccination once or twice with the baculovirus-H5 vaccine prototype activated the chicken interferon-alpha (Ch-IFN-alpha) signalling pathway via transduction of antiviral components, e.g., Mx1 and IRF7. Birds immunized once with rHVT-H5 at 1 day old did not show activation of the Mx1 and IRF7 transcripts; however, following boosting with the baculovirus-H5 prototype vaccine, up-regulation of Mx1 and IRF7 was observed. Based on our findings, it can be concluded that either reinforcement with two injections of the baculovirus-H5 prototype or prime-boost vaccination (rHVT-H5 at 1 day old followed by the baculovirus-H5 prototype vaccine at 8 days old) is a successful strategy to induce both innate and humoral immune responses and could be recommended for the layer production sector over the entire rearing period, especially in AI-endemic areas.
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Affiliation(s)
- Mustafa Hamad
- Poultry Diseases Department, Faculty of Veterinary Medicine, Assuit University, Zagazig, Egypt
| | - Omar Amen
- Poultry Diseases Department, Faculty of Veterinary Medicine, Assuit University, Zagazig, Egypt
| | - Mohamed Mahmoud
- Poultry Diseases Department, Faculty of Veterinary Medicine, Assuit University, Zagazig, Egypt
| | - Ola Hassanin
- Avian and Rabbit Diseases Department, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
| | - Mostafa Saif-Edin
- Poultry Diseases Department, Faculty of Veterinary Medicine, Assuit University, Zagazig, Egypt.
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Kar UP, Dey H, Rahaman A. Tetrahymena dynamin-related protein 6 self-assembles independent of membrane association. J Biosci 2017. [DOI: 10.1007/s12038-017-9726-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Rennie ML, McKelvie SA, Bulloch EMM, Kingston RL. Transient dimerization of human MxA promotes GTP hydrolysis, resulting in a mechanical power stroke. Structure 2016; 22:1433-45. [PMID: 25295396 DOI: 10.1016/j.str.2014.08.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 08/14/2014] [Accepted: 08/20/2014] [Indexed: 12/11/2022]
Abstract
Myxovirus resistance (Mx) proteins restrict replication of numerous viruses. They are closely related to membrane-remodeling fission GTPases, such as dynamin. Mx proteins can tubulate lipids and form rings or filaments that may interact directly with viral structures. GTPase domain dimerization is thought to allow crosstalk between the rungs of a tubular or helical assembly, facilitating constriction. We demonstrate that the GTPase domain of MxA dimerizes to facilitate catalysis, in a fashion analogous to dynamin. GTP binding is associated with the lever-like movement of structures adjacent to the GTPase domain, while GTP hydrolysis returns MxA to its resting state. Dimerization is not significantly promoted by substrate binding and occurs only transiently, yet is central to catalytic efficiency. Therefore, we suggest dimerization functions to coordinate the activity of spatially adjacent Mx molecules within an assembly, allowing their mechanical power strokes to be synchronized at key points in the contractile cycle.
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Affiliation(s)
- Martin L Rennie
- Maurice Wilkins Centre, School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
| | - Siri A McKelvie
- Maurice Wilkins Centre, School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
| | - Esther M M Bulloch
- Maurice Wilkins Centre, School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
| | - Richard L Kingston
- Maurice Wilkins Centre, School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand.
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Abdallah F, Hassanin O. Positive regulation of humoral and innate immune responses induced by inactivated Avian Influenza Virus vaccine in broiler chickens. Vet Res Commun 2015; 39:211-6. [PMID: 26329833 DOI: 10.1007/s11259-015-9644-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 08/24/2015] [Indexed: 11/30/2022]
Abstract
Avian Influenza (AI) vaccines are widely used for mammals and birds in a trial to eliminate the Avian Influenza virus (AIV) infection from the world. However and up till now the virus is still existed via modulation of its antigenic structure to evade the pressure of host immune responses. For a complete understanding of the immune responses following AI vaccination in chickens, the modulations of the chickens humoral immune responses and interferon-alpha signaling pathway, as a fundamental part of the innate immune responses, were investigated. In our study, we measured the humoral immune response using hemagglutination-inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) tests. In addition, chicken interferon-alpha pathway components was measured at RNA levels using Quantitative Real-time PCR (qRT-PCR) following one dose of inactivated H5N1 influenza vaccine at 14 days of age. In this study, the protective levels of humoral antibody responses were observed at 14, 21 and 28 days following immunization with inactivated (Re-1/H5N1) AI vaccine. In the chicken spleen cells, up regulation in the chicken interferon-alpha pathway components (MX1 & IRF7) was existed as early as 48 h post vaccination and remained until 28 days post vaccination at the endogenous state. However, after the recall with ex-vivo stimulation, the up regulation was more pronounced in the transcriptional factor (IRF7) compared to the antiviral gene (MX1) at 28 days post vaccination. So far, from our results it appears that the inactivated H5N1 vaccine can trigger the chicken interferon-alpha signaling pathway as well as it can elicit protective humoral antibody responses.
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Affiliation(s)
- Fatma Abdallah
- Department of Virology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, 445119, Egypt.
| | - Ola Hassanin
- Department of Avian and Rabbit Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt
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Mx proteins: antiviral gatekeepers that restrain the uninvited. Microbiol Mol Biol Rev 2014; 77:551-66. [PMID: 24296571 DOI: 10.1128/mmbr.00024-13] [Citation(s) in RCA: 207] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Fifty years after the discovery of the mouse Mx1 gene, researchers are still trying to understand the molecular details of the antiviral mechanisms mediated by Mx proteins. Mx proteins are evolutionarily conserved dynamin-like large GTPases, and GTPase activity is required for their antiviral activity. The expression of Mx genes is controlled by type I and type III interferons. A phylogenetic analysis revealed that Mx genes are present in almost all vertebrates, usually in one to three copies. Mx proteins are best known for inhibiting negative-stranded RNA viruses, but they also inhibit other virus families. Recent structural analyses provide hints about the antiviral mechanisms of Mx proteins, but it is not known how they can suppress such a wide variety of viruses lacking an obvious common molecular pattern. Perhaps they interact with a (partially) symmetrical invading oligomeric structure, such as a viral ribonucleoprotein complex. Such an interaction may be of a fairly low affinity, in line with the broad target specificity of Mx proteins, yet it would be strong enough to instigate Mx oligomerization and ring assembly. Such a model is compatible with the broad "substrate" specificity of Mx proteins: depending on the size of the invading viral ribonucleoprotein complexes that need to be wrapped, the assembly process would consume the necessary amount of Mx precursor molecules. These Mx ring structures might then act as energy-consuming wrenches to disassemble the viral target structure.
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Sasaki K, Tungtrakoolsub P, Morozumi T, Uenishi H, Kawahara M, Watanabe T. A single nucleotide polymorphism of porcine MX2 gene provides antiviral activity against vesicular stomatitis virus. Immunogenetics 2013; 66:25-32. [DOI: 10.1007/s00251-013-0745-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 10/28/2013] [Indexed: 01/09/2023]
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Glymph S, Mandal S, Knowell AE, Abebe F, Chaudhary J. The myxovirus resistance A (MxA) gene -88G>T single nucleotide polymorphism is associated with prostate cancer. INFECTION GENETICS AND EVOLUTION 2013; 16:186-90. [PMID: 23438650 DOI: 10.1016/j.meegid.2013.02.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 01/17/2013] [Accepted: 02/05/2013] [Indexed: 12/15/2022]
Abstract
BACKGROUND Myxovirus (influenza virus) resistance A (MxA) is an interferon stimulated antiviral protein that is required for a complete antiviral response. MxA polymorphism (rs2071430) is located within an Interferon Stimulated Response Element (ISRE) at position -88 in the gene's promoter region, and it has been associated with increased susceptibility to infections and various diseases. In general, the low promoter activity genotype (GG) promotes susceptibility, whereas the high promoter activity genotype (TT) confers protection to Hepatitis C viral infection. MxA's role in prostate cancer is not fully understood. Previous literature has shown that MxA may be a mediator of the effect of IFN on normal and tumor cell motility. MxA may act as a tumor suppressor and the level of expression may be a predictor of metastatic potential. Based on this information, in this study we investigated the association of this functional polymorphism (rs2071430) in MxA with prostate cancer. METHODS Sample size and power was calculated using the PGA software. Genomic DNA from a controls (n=140) and prostate cancer patients (n=164) were used for genotyping SNP rs2071430 on all samples. Statistical analysis was performed using logistic regression model. RESULTS A significant association was observed between rs2071430 genotype GG and prostate cancer. Individuals harboring the GG genotype are at an increased risk of prostate cancer. Data stratification reveals that the mutant GT genotype offers either offers some protection against prostate cancer in Caucasians. CONCLUSIONS MxA SNP rs2071430 GG genotype is significantly associated with prostate cancer irrespective of race. However, data stratification also suggests that the GT genotype is under-represented in Caucasian subjects suggesting its role in protection against prostate cancer in Caucasians. Although MxA is primarily implicated in viral infection, but it may be also be associated with prostate cancer. Recent studies have implicated viral and bacterial infections with increased prostate cancer risk. Expression of the high promoter activity genotype may offer resistance to prostate cancer infection and possibly influence clinical outcomes.
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Affiliation(s)
- Shanora Glymph
- Center for Cancer Research and Therapeutics Development, Clark Atlanta University, Atlanta, GA 30314, USA
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von der Malsburg A, Abutbul-Ionita I, Haller O, Kochs G, Danino D. Stalk domain of the dynamin-like MxA GTPase protein mediates membrane binding and liposome tubulation via the unstructured L4 loop. J Biol Chem 2011; 286:37858-65. [PMID: 21900240 DOI: 10.1074/jbc.m111.249037] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The human MxA protein is an interferon-induced large GTPase with antiviral activity against a wide range of viruses, including influenza viruses. Recent structural data demonstrated that MxA oligomerizes into multimeric filamentous or ring-like structures by virtue of its stalk domain. Here, we show that negatively charged lipid membranes support MxA self-assembly. Like dynamin, MxA assembled around spherical liposomes inducing liposome tubulation. Cryo-transmission electron microscopy revealed that MxA oligomers around liposomes have a "T-bar" shape similar to dynamin. Moreover, biochemical assays indicated that the unstructured L4 loop of the MxA stalk serves as the lipid-binding moiety, and mutational analysis of L4 revealed that a stretch of four lysine residues is critical for binding. The orientation of the MxA molecule within the membrane-associated oligomer is in agreement with the proposed topology of MxA oligomers based on crystallographic data. Although oligomerization of wild-type MxA around liposomes led to the creation of helically decorated tubes similar to those formed by dynamin, this lipid interaction did not stimulate GTPase activity, in sharp contrast to the assembly-stimulated nucleotide hydrolysis observed with dynamin. Moreover, MxA readily self-assembles into rings at physiological conditions, as opposed to dynamin which self-assembles only at low salt conditions or onto lipids. Thus, the present results indicate that the oligomeric structures formed by MxA critically differ from those of dynamin.
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Schusser B, Reuter A, von der Malsburg A, Penski N, Weigend S, Kaspers B, Staeheli P, Härtle S. Mx is dispensable for interferon-mediated resistance of chicken cells against influenza A virus. J Virol 2011; 85:8307-15. [PMID: 21632756 PMCID: PMC3147972 DOI: 10.1128/jvi.00535-11] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 05/24/2011] [Indexed: 12/14/2022] Open
Abstract
The type I interferon (IFN) system plays an important role in antiviral defense against influenza A viruses (FLUAV), which are natural chicken pathogens. Studies of mice identified the Mx1 protein as a key effector molecule of the IFN-induced antiviral state against FLUAV. Chicken Mx genes are highly polymorphic, and recent studies suggested that an Asn/Ser polymorphism at amino acid position 631 determines the antiviral activity of the chicken Mx protein. By employing chicken embryo fibroblasts with defined Mx-631 polymorphisms and retroviral vectors for the expression of Mx isoforms in chicken cells and embryonated eggs, we show here that neither the 631Asn nor the 631Ser variant of chicken Mx was able to confer antiviral protection against several lowly and highly pathogenic FLUAV strains. Using a short interfering RNA (siRNA)-mediated knockdown approach, we noted that the antiviral effect of type I IFN in chicken cells was not dependent on Mx, suggesting that some other IFN-induced factors must contribute to the inhibition of FLUAV in chicken cells. Finally, we found that both isoforms of chicken Mx protein appear to lack GTPase activity, which might explain the observed lack of antiviral activity.
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Affiliation(s)
| | - Antje Reuter
- Department of Virology, University Freiburg, Germany
- International Max Planck Research School for Molecular and Cellular Biology, Freiburg, Germany
| | | | - Nicola Penski
- Department of Virology, University Freiburg, Germany
| | - Steffen Weigend
- Institute of Farm Animal Genetics, Friedrich Loeffler Institute, Neustadt-Mariensee, Germany
| | - Bernd Kaspers
- Department of Veterinary Science, University Munich, Germany
| | | | - Sonja Härtle
- Department of Veterinary Science, University Munich, Germany
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12
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Structural and Functional Studies of The Innate Immune Effector Mx Proteins: a Review. PROG BIOCHEM BIOPHYS 2010. [DOI: 10.3724/sp.j.1206.2009.00730] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Haller O, Gao S, von der Malsburg A, Daumke O, Kochs G. Dynamin-like MxA GTPase: structural insights into oligomerization and implications for antiviral activity. J Biol Chem 2010; 285:28419-24. [PMID: 20538602 DOI: 10.1074/jbc.r110.145839] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interferon-inducible MxA GTPase is a key mediator of cell-autonomous innate immunity against a broad range of viruses such as influenza and bunyaviruses. MxA shares a similar domain structure with the dynamin superfamily of mechanochemical enzymes, including an N-terminal GTPase domain, a central middle domain, and a C-terminal GTPase effector domain. Recently, crystal structures of a GTPase domain dimer of dynamin 1 and of the oligomerized stalk of MxA (built by the middle and GTPase effector domains) were determined. These data provide exciting insights into the architecture and antiviral function of the MxA oligomer. Moreover, the structural knowledge paves the way for the development of novel antiviral drugs against influenza and other highly pathogenic viruses.
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Affiliation(s)
- Otto Haller
- Department of Virology, Institute for Medical Microbiology and Hygiene, University of Freiburg, Hermann-Herder-Strasse 11, D-79104 Freiburg, Germany.
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Structural basis of oligomerization in the stalk region of dynamin-like MxA. Nature 2010; 465:502-6. [PMID: 20428112 DOI: 10.1038/nature08972] [Citation(s) in RCA: 191] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 02/25/2010] [Indexed: 12/11/2022]
Abstract
The interferon-inducible dynamin-like myxovirus resistance protein 1 (MxA; also called MX1) GTPase is a key mediator of cell-autonomous innate immunity against pathogens such as influenza viruses. MxA partially localizes to COPI-positive membranes of the smooth endoplasmic reticulum-Golgi intermediate compartment. At the point of infection, it redistributes to sites of viral replication and promotes missorting of essential viral constituents. It has been proposed that the middle domain and the GTPase effector domain of dynamin-like GTPases constitute a stalk that mediates oligomerization and transmits conformational changes from the G domain to the target structure; however, the molecular architecture of this stalk has remained elusive. Here we report the crystal structure of the stalk of human MxA, which folds into a four-helical bundle. This structure tightly oligomerizes in the crystal in a criss-cross pattern involving three distinct interfaces and one loop. Mutations in each of these interaction sites interfere with native assembly, oligomerization, membrane binding and antiviral activity of MxA. On the basis of these results, we propose a structural model for dynamin oligomerization and stimulated GTP hydrolysis that is consistent with previous structural predictions and has functional implications for all members of the dynamin family.
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Wu K, Liu P, Meng XX, Liu L, Li YH, Ge ZZ, Yang JC. Preparation of polyclonal antibody against human MxA protein and its specificity to diversified myxovirus resistant protein A. BIOMEDICAL AND ENVIRONMENTAL SCIENCES : BES 2010; 23:76-82. [PMID: 20486440 DOI: 10.1016/s0895-3988(10)60035-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
OBJECTIVE To study the human myxovirus resistant protein A (MxA), a specifically induced peptide by interferon I, and to use its level as a diagnostic criterion for viral infections. METHODS Anti-MxA antisera from immunized mice were prepared with the expressed MxA protein of pET32a-MxA in E. coli BL-21(DE3). To confirm the antiserum activity and specificity, the expression product of BL21, wild type MxA pEGFP-C1-wMxA and site-directed mutant MxA pEGFP-C1-mMxA(N589S) stably transfected 3T3 cells and induced A549 cells were detected by Western blot with the antisera using non-MxA transfected or non-IFN-beta induced cells, intact A549, NIH 3T3 cells transfected with pEGFP-C1 and pET32a (+)-transformed BL-21 as controls. RESULTS The antisera had specific positive immunoreactivity to the NIH3T3 cells transformed with pEGFP-C1-wMxA and pEGFP-C1-mMxA, INF-beta induced A549 cells and BL21 proteins expressed with pET32a (+)-MxA. The hybridization signals from IFN-beta induced A549 cells depended on the IFN-beta inducing concentrations. Meanwhile, immunohistochemical assay showed that NIH 3T3 cells with pEGFP-C1-wMxA and pEGFP-C1-mMxA had > 98% of positive cells at 1:50 dilution of the serum and A549 cells induced by 20 ng/mL IFN-beta for 48 h showed 95% positive cells. pEGFP-C1-transfected NIH 3T3 cells were all negative. CONCLUSION Anti-sera are highly specific to diversified MxAs. The antibody is detectable by Western blot, immunocytochemistry and immunofluorescence assay.
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Affiliation(s)
- Kang Wu
- School of Basic Medicine and Biology, Suzhou University, Suzhou 215123, Jiangsu, China
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Chugh J, Sharma S, Kumar D, Misra JR, Hosur RV. Effect of a single point mutation on the stability, residual structure and dynamics in the denatured state of GED: relevance to self-assembly. Biophys Chem 2008; 137:13-8. [PMID: 18586378 DOI: 10.1016/j.bpc.2008.06.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 06/05/2008] [Accepted: 06/05/2008] [Indexed: 10/21/2022]
Abstract
The GTPase effector domain (GED) of dynamin forms large soluble oligomers in vitro, while its mutant--I697A--lacks this property at low concentrations. With a view to understand the intrinsic structural characteristics of the polypeptide chain, the global unfolding characteristics of GED wild type (WT) and I697A were compared using biophysical techniques. Quantitative analysis of the CD and fluorescence denaturation profiles revealed that unfolding occurred by a two-state process and the mutant was less stable than the WT. Even in the denatured state, the mutation caused chemical shift perturbations and significant differences were observed in the 15N transverse relaxation rates (R2), not only at the mutation site but all around. These results demonstrate that the hydrophobic change associated with the mutation perturbs the structural and motional preferences locally, which are then relayed via different folding pathways along the chain and the property of oligomerization in the native state is affected.
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Affiliation(s)
- Jeetender Chugh
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400005, India
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Palm M, Leroy M, Thomas A, Linden A, Desmecht D. Differential Anti-Influenza Activity among Allelic Variants at TheSus Scrofa Mx1Locus. J Interferon Cytokine Res 2007; 27:147-55. [PMID: 17316142 DOI: 10.1089/jir.2006.0119] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A promising way to oppose infectious challenges would be to improve the resistance of the target species through genetic selection. Theoretically, a candidate gene is available against influenza viruses since a resistance trait was fortuitously discovered in the A2G mouse strain. This trait was demonstrated to be correlated with the expression of a specific isoform of the type I interferon (IFN)-dependent protein MX, an isoform coded by a specific allele at the mouse Mx1 locus. Two allelic polymorphisms were described recently in the Sus scrofa homologous gene. In this study, the frequencies and distribution of both alleles were evaluated among European domestic pig and wild boar populations by PCR-RFLP, and the anti-influenza activity conferred by both MX1 isoforms was evaluated in vitro using transfection of Vero cells followed by flow cytometric determination of the fraction of influenza virus-infected cells among MX-producing and MX-nonproducing cell populations. A significant difference in the anti-influenza activity brought by the two MX1 isoforms was demonstrated, which suggests that a significant improvement of innate resistance of pigs by genetic selection might be feasible provided the differences found here in vitro are epidemiologically relevant in vivo.
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Affiliation(s)
- M Palm
- Department of Pathology, University of Liège, B-4000 Liège, Belgium
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Abstract
Mammalian cells respond to interferons (IFNs) secreted during infection by the transcriptional upregulation of as many as a thousand genes. This remarkable transition prepares cells and organisms for resistance to infection, and many IFN-regulated gene products are players in well-understood resistance programs. Oddly, however, many of the most abundantly induced proteins are GTPases whose functions are not well understood. Here we review the progress that has been made toward understanding the roles of individual GTPase families in disease resistance and the hints of common mechanisms that are now available.
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Affiliation(s)
- Sascha Martens
- Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom.
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Macia E, Ehrlich M, Massol R, Boucrot E, Brunner C, Kirchhausen T. Dynasore, a Cell-Permeable Inhibitor of Dynamin. Dev Cell 2006; 10:839-50. [PMID: 16740485 DOI: 10.1016/j.devcel.2006.04.002] [Citation(s) in RCA: 1577] [Impact Index Per Article: 87.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Revised: 03/22/2006] [Accepted: 04/03/2006] [Indexed: 11/25/2022]
Abstract
Dynamin is essential for clathrin-dependent coated vesicle formation. It is required for membrane budding at a late stage during the transition from a fully formed pit to a pinched-off vesicle. Dynamin may also fulfill other roles during earlier stages of vesicle formation. We have screened about 16,000 small molecules and have identified 1, named here dynasore, that interferes in vitro with the GTPase activity of dynamin1, dynamin2, and Drp1, the mitochondrial dynamin, but not of other small GTPases. Dynasore acts as a potent inhibitor of endocytic pathways known to depend on dynamin by rapidly blocking coated vesicle formation within seconds of dynasore addition. Two types of coated pit intermediates accumulate during dynasore treatment, U-shaped, half formed pits and O-shaped, fully formed pits, captured while pinching off. Thus, dynamin acts at two steps during clathrin coat formation; GTP hydrolysis is probably needed at both steps.
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Affiliation(s)
- Eric Macia
- Department of Cell Biology, Harvard Medical School and the CBR Institute for Biomedical Research, Inc., 200 Longwood Avenue, Boston, Massachusetts 02115, USA
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Solomaha E, Palfrey H. Conformational changes in dynamin on GTP binding and oligomerization reported by intrinsic and extrinsic fluorescence. Biochem J 2006; 391:601-11. [PMID: 15954862 PMCID: PMC1276961 DOI: 10.1042/bj20050707] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effects of guanine nucleotides on the intrinsic and extrinsic fluorescence properties of dynamin were assessed. The intrinsic Trp (tryptophan) fluorescence spectra of purified recombinant dynamin-1 and -2 were very similar, with a maximum at 332 nm. Collisional quenching by KI was weak (approximately 30%), suggesting that the majority of Trp residues are buried. Binding of guanine nucleotides decreased intrinsic fluorescence by 15-20%. Titration of the effects showed that GTP and GDP bound to a single class of non-interacting sites in dynamin tetramers with apparent dissociation constants (K(d)) values of 5.4 and 7.4 microM (dynamin-1) and 13.2 and 7.1 microM (dynamin-2) respectively. Similar dissociation constant values for both nucleotides were obtained by titrating the quenching of IAEDANS [N-iodoacetyl-N'-(5-sulpho-1-naphthyl)ethylenediamine]-labelled dynamin-2. Despite the similar binding affinities, GTP and GDP result in different conformations of the protein, as revealed by sensitivity to proteinase K fragmentation. Dynamins contain five Trp residues, of which four are in the PH domain (pleckstrin homology domain) and one is in the C-terminal PRD (proline/arginine-rich domain). Guanine nucleotides quenched fluorescence emission from a truncated (DeltaPRD) mutant dynamin-1 to the same extent as in the full-length protein, suggesting conformational coupling between the G (groove)-domain and the PH domain. Efficient resonance energy transfer from PH domain Trp residues to bound mant-GTP [where mant stands for 2'-(3')-O-(N-methylanthraniloyl)] suggests that the G-domain and PH domain are in close proximity (5-6 nm). Promotion of dynamin-2 oligomerization, by reduction in ionic strength or increasing protein concentration, had little effect on intrinsic dynamin fluorescence. However, fluorescence emission from IAEDANS.dynamin-2 showed a significant spectral shift on oligomerization. In addition, energy transfer was observed when oligomerization was promoted in mixtures of IAEDANS.dynamin-2 and 4-(4-dimethylaminophenylazo)benzoic acid-coupled dynamin-2, an effect that was counteracted by GTP but not GDP.
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Affiliation(s)
- Elena Solomaha
- Department of Neurobiology, Pharmacology and Physiology, University of Chicago, 947 E. 58th St., Chicago, IL 60637, U.S.A
| | - H. Clive Palfrey
- Department of Neurobiology, Pharmacology and Physiology, University of Chicago, 947 E. 58th St., Chicago, IL 60637, U.S.A
- To whom correspondence should be addressed (email )
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21
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Martínez-Vicente M, Yim L, Villarroya M, Mellado M, Pérez-Payá E, Björk GR, Armengod ME. Effects of mutagenesis in the switch I region and conserved arginines of Escherichia coli MnmE protein, a GTPase involved in tRNA modification. J Biol Chem 2005; 280:30660-70. [PMID: 15983041 DOI: 10.1074/jbc.m503223200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MnmE is an evolutionarily conserved, three domain GTPase involved in tRNA modification. In contrast to Ras proteins, MnmE exhibits a high intrinsic GTPase activity and requires GTP hydrolysis to be functionally active. Its G domain conserves the GTPase activity of the full protein, and thus, it should contain the catalytic residues responsible for this activity. In this work, mutational analysis of all conserved arginine residues of the MnmE G-domain indicates that MnmE, unlike other GTPases, does not use an arginine finger to drive catalysis. In addition, we show that residues in the G2 motif (249GTTRD253), which resides in the switch I region, are not important for GTP binding but play some role in stabilizing the transition state, specially Gly249 and Thr251. On the other hand, G2 mutations leading to a minor loss of the GTPase activity result in a non-functional MnmE protein. This indicates that GTP hydrolysis is a required but non-sufficient condition so that MnmE can mediate modification of tRNA. The conformational change of the switch I region associated with GTP hydrolysis seems to be crucial for the function of MnmE, and the invariant threonine (Thr251) of the G2 motif would be essential for such a change, because it cannot be substituted by serine. MnmE defects result in impaired growth, a condition that is exacerbated when defects in other genes involved in the decoding process are simultaneously present. This behavior is reminiscent to that found in yeast and stresses the importance of tRNA modification for gene expression.
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Affiliation(s)
- Marta Martínez-Vicente
- Laboratorio de Genética Molecular, Centro de Investigación Príncipe Felipe, Valencia, Spain
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22
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Neuspiel M, Zunino R, Gangaraju S, Rippstein P, McBride H. Activated mitofusin 2 signals mitochondrial fusion, interferes with Bax activation, and reduces susceptibility to radical induced depolarization. J Biol Chem 2005; 280:25060-70. [PMID: 15878861 DOI: 10.1074/jbc.m501599200] [Citation(s) in RCA: 254] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial fusion in higher eukaryotes requires at least two essential GTPases, Mitofusin 1 and Mitofusin 2 (Mfn2). We have created an activated mutant of Mfn2, which shows increased rates of nucleotide exchange and decreased rates of hydrolysis relative to wild type Mfn2. Mitochondrial fusion is stimulated dramatically within heterokaryons expressing this mutant, demonstrating that hydrolysis is not requisite for the fusion event, and supporting a role for Mfn2 as a signaling GTPase. Although steady-state mitochondrial fusion required the conserved intermembrane space tryptophan residue, this requirement was overcome within the context of the hydrolysis-deficient mutant. Furthermore, the punctate localization of Mfn2 is lost in the dominant active mutants, indicating that these sites are functionally controlled by changes in the nucleotide state of Mfn2. Upon staurosporine-stimulated cell death, activated Bax is recruited to the Mfn2-containing puncta; however, Bax activation and cytochrome c release are inhibited in the presence of the dominant active mutants of Mfn2. The dominant active form of Mfn2 also protected the mitochondria against free radical-induced permeability transition. In contrast to staurosporine-induced outer membrane permeability transition, pore opening induced through the introduction of free radicals was dependent upon the conserved intermembrane space residue. This is the first evidence that Mfn2 is a signaling GTPase regulating mitochondrial fusion and that the nucleotide-dependent activation of Mfn2 concomitantly protects the organelle from permeability transition. The data provide new insights into the critical relationship between mitochondrial membrane dynamics and programmed cell death.
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Affiliation(s)
- Margaret Neuspiel
- University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
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23
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Reichelt M, Stertz S, Krijnse-Locker J, Haller O, Kochs G. Missorting of LaCrosse virus nucleocapsid protein by the interferon-induced MxA GTPase involves smooth ER membranes. Traffic 2005; 5:772-84. [PMID: 15355513 DOI: 10.1111/j.1600-0854.2004.00219.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interferon-induced human MxA protein belongs to the class of dynamin-like, large guanosine-5'-triphosphatases that are involved in intracellular vesicle trafficking and organelle homeostasis. MxA shares many properties with the other members of this protein superfamily, including the propensity to self-assemble and to associate with lipid membranes. However, MxA is unique in that it has antiviral activity and inhibits the replication of several RNA viruses. Here, we determined the role of membranes for the antiviral function of MxA using LaCrosse-bunyavirus (LACV). We show that MxA does not affect trafficking and sorting of viral glycoproteins but binds and mislocates the viral nucleocapsid (N) protein into membrane-associated, large perinuclear complexes. We further demonstrate that MxA localizes to a subcompartment of the smooth endoplasmic reticulum where the viral N protein accumulates. In infected MxA-expressing cells, oligomeric MxA/N complexes are formed in close association with COP-I-positive vesicular-tubular membranes. Our results suggest that this membrane compartment is the preferred place where MxA and N interact, leading to efficient sequestration and missorting of an essential viral component.
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Affiliation(s)
- Mike Reichelt
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008 Freiburg, Germany
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24
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Kochs G, Reichelt M, Danino D, Hinshaw JE, Haller O. Assay and Functional Analysis of Dynamin‐Like Mx Proteins. Methods Enzymol 2005; 404:632-43. [PMID: 16413306 DOI: 10.1016/s0076-6879(05)04055-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Mx proteins are interferon-induced large guanosine triphosphatases (GTPases) that share structural and functional properties with dynamin and dynamin-like proteins, such as self-assembly and association with intracellular membranes. A unique property of some Mx proteins is their antiviral activity against a range of RNA viruses, including influenza viruses and members of the bunyavirus family. These viruses are inhibited at an early stage in their life cycle, soon after host cell entry and before genome amplification. The association of the human MxA GTPase with membranes of the endoplasmic reticulum seems to support its antiviral function by providing an interaction platform that facilitates viral target recognition, MxA oligomerization, and missorting of the resulting multiprotein complex into large intracellular aggregates.
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Affiliation(s)
- Georg Kochs
- Department of Virology, University of Freiburg, Germany
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25
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Praefcke GJK, Kloep S, Benscheid U, Lilie H, Prakash B, Herrmann C. Identification of residues in the human guanylate-binding protein 1 critical for nucleotide binding and cooperative GTP hydrolysis. J Mol Biol 2004; 344:257-69. [PMID: 15504415 DOI: 10.1016/j.jmb.2004.09.026] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Revised: 09/14/2004] [Accepted: 09/14/2004] [Indexed: 11/27/2022]
Abstract
The guanylate-binding proteins (GBPs) form a group of interferon-gamma inducible GTP-binding proteins which belong to the family of dynamin-related proteins. Like other members of this family, human guanylate-binding protein 1 (hGBP1) shows nucleotide-dependent oligomerisation that stimulates the GTPase activity of the protein. A unique feature of the GBPs is their ability to hydrolyse GTP to GDP and GMP. In order to elucidate the relationship between these findings, we designed point mutants in the phosphate-binding loop (P-loop) as well as in the switch I and switch II regions of the protein based on the crystal structure of hGBP1. These mutant proteins were analysed for their interaction with guanine nucleotides labeled with a fluorescence dye and for their ability to hydrolyse GTP in a cooperative manner. We identified mutations of amino acid residues that decrease GTPase activity by orders of magnitude a part of which are conserved in GTP-binding proteins. In addition, mutants in the P-loop were characterized that strongly impair binding of nucleotide. In consequence, together with altered GTPase activity and given cellular nucleotide concentrations this results in hGBP1 mutants prevailingly resting in the nucleotide-free (K51A and S52N) or the GTP bound form (R48A), respectively. Using size-exclusion chromatography and analytical ultracentrifugation we addressed the impact on protein oligomerisation. In summary, mutants of hGBP1 were identified and biochemically characterized providing hGBP1 locked in defined states in order to investigate their functional role in future cell biology studies.
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Affiliation(s)
- Gerrit J K Praefcke
- Abteilung Strukturelle Biologie, Max-Planck-Institut für Molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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26
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Ogata S, Ogata A, Schneider-Schaulies S, Schneider-Schaulies S, Schneider-Schaulies J. Expression of the interferon-alpha/beta-inducible MxA protein in brain lesions of subacute sclerosing panencephalitis. J Neurol Sci 2004; 223:113-9. [PMID: 15337611 DOI: 10.1016/j.jns.2004.04.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Revised: 04/20/2004] [Accepted: 04/21/2004] [Indexed: 10/26/2022]
Abstract
The type-I interferon (IFN) inducible human MxA protein exhibits antiviral activity against a variety of RNA viruses including the measles virus (MV). In this study, we investigated the association between the expression of MV antigens and MxA in subacute sclerosing panencephalitis (SSPE) brains. We analyzed the MxA expression in and around lesions in brains of three SSPE patients and compared it with normal brains. Double staining with antibodies against MxA and the MV nucleocapsid revealed that MxA was highly expressed in a belt surrounding MV-antigen-positive lesions in SSPE brains. In normal appearing regions distant from a lesion in SSPE brains and in normal brains, MxA was not detected. Furthermore, MxA was often less or not expressed in the center of lesions expressing high amounts of MV antigens. Such a pattern of MxA expression in SSPE brains clearly indicates that newly infected cells release type I IFN and will become demarcated by a protecting barrier of MxA expressing cells. Double staining with antibodies against MxA and glial fibrillary acidic protein (GFAP) showed that the MxA protein was expressed mainly in the cytoplasm of astrocytes. MxA expression did not correlate with the presence of cellular infiltrates of inflammatory cells, although some lymphoid cells were also positive for MxA. Since MxA inhibits the replication of MV, these findings suggest that the IFN-induced MxA protein plays an important role in slowing down the viral spread in SSPE brains and by doing so may contribute to the persistence of the MV-infection.
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Affiliation(s)
- Seiko Ogata
- Institut für Virologie und Immunbiologie, Versbacher Strasse. 7, D-97078 Würzburg, Germany
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27
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Praefcke GJK, McMahon HT. The dynamin superfamily: universal membrane tubulation and fission molecules? Nat Rev Mol Cell Biol 2004; 5:133-47. [PMID: 15040446 DOI: 10.1038/nrm1313] [Citation(s) in RCA: 1042] [Impact Index Per Article: 52.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Dynamins are large GTPases that belong to a protein superfamily that, in eukaryotic cells, includes classical dynamins, dynamin-like proteins, OPA1, Mx proteins, mitofusins and guanylate-binding proteins/atlastins. They are involved in many processes including budding of transport vesicles, division of organelles, cytokinesis and pathogen resistance. With sequenced genomes from Homo sapiens, Drosophila melanogaster, Caenorhabditis elegans, yeast species and Arabidopsis thaliana, we now have a complete picture of the members of the dynamin superfamily from different organisms. Here, we review the superfamily of dynamins and their related proteins, and propose that a common mechanism leading to membrane tubulation and/or fission could encompass their many varied functions.
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Affiliation(s)
- Gerrit J K Praefcke
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
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28
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Song BD, Yarar D, Schmid SL. An assembly-incompetent mutant establishes a requirement for dynamin self-assembly in clathrin-mediated endocytosis in vivo. Mol Biol Cell 2004; 15:2243-52. [PMID: 15004222 PMCID: PMC404019 DOI: 10.1091/mbc.e04-01-0015] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Dynamin GTPase activity is required for its biological function in clathrin-mediated endocytosis; however, the role of self-assembly has not been unambiguously established. Indeed, overexpression of a dynamin mutant, Dyn1-K694A, with impaired ability to self-assemble has been shown to stimulate endocytosis in HeLa cells (Sever et al., Nature 1999, 398, 481). To identify new, assembly-incompetent mutants of dynamin 1, we made point mutations in the GTPase effector/assembly domain (GED) and tested for their effects on self-assembly and clathrin-mediated endocytosis. Mutation of three residues, I690, K694, and I697, suggests that interactions with an amphipathic helix in GED are required for self-assembly. In particular, Dyn1-I690K failed to exhibit detectable assembly-stimulated GTPase activity under all assay conditions. Overexpression of this assembly-incompetent mutant inhibited transferrin endocytosis as potently as the GTPase-defective dominant-negative mutant, Dyn1-K44A. However, worm-like endocytic intermediates accumulated in cells expressing Dyn1-I690K that were structurally distinct from long tubules that accumulated in cells expressing Dyn1-K44A. Together these results provide new structural insight into the role of GED in self-assembly and assembly-stimulated GTPase activity and establish that dynamin self-assembly is essential for clathrin-mediated endocytosis.
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Affiliation(s)
- Byeong Doo Song
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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29
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Uthaiah RC, Praefcke GJK, Howard JC, Herrmann C. IIGP1, an interferon-gamma-inducible 47-kDa GTPase of the mouse, showing cooperative enzymatic activity and GTP-dependent multimerization. J Biol Chem 2003; 278:29336-43. [PMID: 12732635 DOI: 10.1074/jbc.m211973200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
IIGP1 belongs to a well defined family of 47-kDa GTPases whose members are present at low resting levels in mouse cells but are strongly induced transcriptionally by interferons and are implicated in cell-autonomous resistance to intracellular pathogens. Recombinant IIGP1 was expressed in Escherichia coli and purified to homogeneity. Here we present a detailed biochemical characterization of IIGP1 using various biochemical and biophysical methods. IIGP1 binds to GTP and GDP with dissociation constants in the micromolar range with at least 10 times higher affinity for GDP than for GTP. IIGP1 hydrolyzes GTP to GDP, and the GTPase activity is concentration-dependent with a GTP turnover rate of 2 min-1 under saturating protein concentrations. Functional interaction between IIGP1 molecules is shown by nucleotide-dependent oligomerization in vitro. Both cooperative hydrolysis of GTP and GTP-dependent oligomerization are blocked in a mutant form of IIGP1 modified at the C terminus. IIGP1 shares micromolar nucleotide affinities and oligomerization-dependent hydrolytic activity with the 67-kDa GTPase hGBP1 (induced by type I and type II interferons), with the antiviral Mx proteins (interferon type I-induced) and with the paradigm of the self-activating large GTPases, the dynamins, with which Mx proteins show homology. The higher relative affinity for GDP and the relatively low GTPase activity distinguish IIGP1, but this study clearly adds IIGP1 and thus the p47 GTPases to the small group of cooperative GTPase families that appear to characterize the development of intracellular resistance during the interferon response to infection. The present analysis provides essential parameters to understand the molecular mechanism by which IIGP1 participates in this complex resistance program.
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Affiliation(s)
- Revathy C Uthaiah
- Institute for Genetics, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany
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30
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Nie Z, Stanley KT, Stauffer S, Jacques KM, Hirsch DS, Takei J, Randazzo PA. AGAP1, an endosome-associated, phosphoinositide-dependent ADP-ribosylation factor GTPase-activating protein that affects actin cytoskeleton. J Biol Chem 2002; 277:48965-75. [PMID: 12388557 DOI: 10.1074/jbc.m202969200] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have identified three members of the AGAP subfamily of ASAP family ADP-ribosylation factor GTPase-activating proteins (Arf GAPs). In addition to the Arf GAP domain, these proteins contain GTP-binding protein-like, ankyrin repeat and pleckstrin homology domains. Here, we have characterized the ubiquitously expressed AGAP1/KIAA1099. AGAP1 had Arf GAP activity toward Arf1>Arf5>Arf6. Phosphatidylinositol 4,5-bisphosphate and phosphatidic acid synergistically stimulated GAP activity. As found for other ASAP family Arf GAPs, the pleckstrin homology domain was necessary for activity. Deletion of the GTP-binding protein-like domain affected lipid dependence of Arf GAP activity. In vivo effects of AGAP1 were distinct from other ASAP family Arf GAPs. Overexpressed AGAP1 induced the formation of and was associated with punctate structures containing the endocytic markers transferrin and Rab4. AP1 was redistributed from the trans-Golgi to the punctate structures. Like other ASAP family members, AGAP1 overexpression inhibited the formation of PDGF-induced ruffles. However, distinct from other ASAP family members, AGAP1 also induced the loss of actin stress fibers. Thus, AGAP1 is a phosphoinositide-dependent Arf GAP that impacts both the endocytic compartment and actin.
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Affiliation(s)
- Zhongzhen Nie
- Laboratories of Cellular Oncology and Biochemistry, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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31
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Marlovits TC, Haase W, Herrmann C, Aller SG, Unger VM. The membrane protein FeoB contains an intramolecular G protein essential for Fe(II) uptake in bacteria. Proc Natl Acad Sci U S A 2002; 99:16243-8. [PMID: 12446835 PMCID: PMC138596 DOI: 10.1073/pnas.242338299] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
G proteins are critical for the regulation of membrane protein function and signal transduction. Nevertheless, coupling between G proteins and membrane proteins with multiple membrane-spanning domains has so far been observed only in higher organisms. Here we show that the polytopic membrane protein FeoB, which is essential for Fe(II) uptake in bacteria, contains a guanine-nucleotide-specific nucleotide binding site. We identify the G4-motif, NXXD, responsible for guanine nucleotide specificity, and show that GTP hydrolysis occurs very slowly. In contrast to typical G proteins, the association and dissociation of GDP were found to be faster than for GTP, suggesting that in the absence of additional factors, FeoB's G protein domain may exist mostly in the GTP-bound form. Furthermore, the binding of GTP is required for efficient Fe(II) uptake through the FeoB-dependent system. Notably, even in bacteria, this covalent linkage between a G protein and a polytopic membrane protein appears, to our knowledge, to be unique. These findings raise the intriguing question whether FeoB represents a primordial archetype of G protein-regulated membrane proteins.
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Affiliation(s)
- Thomas C Marlovits
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, P.O. Box 208024, New Haven, CT 06520-8024, USA
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32
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Accola MA, Huang B, Al Masri A, McNiven MA. The antiviral dynamin family member, MxA, tubulates lipids and localizes to the smooth endoplasmic reticulum. J Biol Chem 2002; 277:21829-35. [PMID: 11916975 DOI: 10.1074/jbc.m201641200] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mx proteins are induced by type I interferon and inhibit a broad range of viruses by undefined mechanisms. They are included within the dynamin family of large GTPases, which are involved in vesicle trafficking and share common biophysical features. These properties include the propensity to self-assemble, an affinity for lipids, and the ability to tubulate membranes. In this report we establish that human MxA, despite sharing only 30% homology with conventional dynamin, possesses many of these properties. We demonstrate for the first time that MxA self-assembles into rings that tubulate lipids in vitro, and associates with a specific membrane compartment in cells, the smooth endoplasmic reticulum.
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Affiliation(s)
- Molly A Accola
- Center for Basic Research in Digestive Diseases and Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA
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33
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Kochs G, Haener M, Aebi U, Haller O. Self-assembly of human MxA GTPase into highly ordered dynamin-like oligomers. J Biol Chem 2002; 277:14172-6. [PMID: 11847228 DOI: 10.1074/jbc.m200244200] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human MxA protein is a member of the interferon-induced Mx protein family and an important component of the innate host defense against RNA viruses. The Mx family belongs to a superfamily of large GTPases that also includes the dynamins and the interferon-regulated guanylate-binding proteins. A common feature of these large GTPases is their ability to form high molecular weight oligomers. Here we determined the capacity of MxA to self-assemble into homo-oligomers in vitro. We show that recombinant MxA protein assembles into long filamentous structures with a diameter of about 20 nm at physiological salt concentration as demonstrated by sedimentation assays and electron microscopy. In the presence of guanosine nucleotides the filaments rearranged into rings and more compact helical arrays. Our data indicate that binding and hydrolysis of GTP induce conformational changes in MxA that may be essential for viral target recognition and antiviral activity.
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Affiliation(s)
- Georg Kochs
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008 Freiburg, Germany.
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34
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Varne A, Muthukumaraswamy K, Jatiani SS, Mittal R. Conformational analysis of the GTP-binding protein MxA using limited proteolysis. FEBS Lett 2002; 516:129-32. [PMID: 11959118 DOI: 10.1016/s0014-5793(02)02519-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Guanosine triphosphate (GTP)-binding proteins are known to function as molecular switches that cycle between GTP-bound and guanosine diphosphate (GDP)-bound states. Switching is achieved by the fact that G-proteins in the GTP-bound conformation can interact with a certain set of effector molecules while they interact with a different set of partners in their GDP-bound conformation. The antiviral properties of the interferon-induced MxA protein are critically dependent on the ability of MxA to bind GTP. Using limited proteolysis we analyzed the conformations of the MxA protein under nucleotide-free, GDP-bound, and GTP-bound conditions. We find that whereas the conformations of nucleotide-free MxA and GDP-bound MxA are essentially similar, GTP-binding causes a dramatic change in the conformation of MxA.
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Affiliation(s)
- Anjali Varne
- Tata Institute of Fundamental Research, Bombay, India
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35
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Abstract
Tremendous progress has been made in understanding the molecular basis of the antiviral actions of interferons (IFNs), as well as strategies evolved by viruses to antagonize the actions of IFNs. Furthermore, advances made while elucidating the IFN system have contributed significantly to our understanding in multiple areas of virology and molecular cell biology, ranging from pathways of signal transduction to the biochemical mechanisms of transcriptional and translational control to the molecular basis of viral pathogenesis. IFNs are approved therapeutics and have moved from the basic research laboratory to the clinic. Among the IFN-induced proteins important in the antiviral actions of IFNs are the RNA-dependent protein kinase (PKR), the 2',5'-oligoadenylate synthetase (OAS) and RNase L, and the Mx protein GTPases. Double-stranded RNA plays a central role in modulating protein phosphorylation and RNA degradation catalyzed by the IFN-inducible PKR kinase and the 2'-5'-oligoadenylate-dependent RNase L, respectively, and also in RNA editing by the IFN-inducible RNA-specific adenosine deaminase (ADAR1). IFN also induces a form of inducible nitric oxide synthase (iNOS2) and the major histocompatibility complex class I and II proteins, all of which play important roles in immune response to infections. Several additional genes whose expression profiles are altered in response to IFN treatment and virus infection have been identified by microarray analyses. The availability of cDNA and genomic clones for many of the components of the IFN system, including IFN-alpha, IFN-beta, and IFN-gamma, their receptors, Jak and Stat and IRF signal transduction components, and proteins such as PKR, 2',5'-OAS, Mx, and ADAR, whose expression is regulated by IFNs, has permitted the generation of mutant proteins, cells that overexpress different forms of the proteins, and animals in which their expression has been disrupted by targeted gene disruption. The use of these IFN system reagents, both in cell culture and in whole animals, continues to provide important contributions to our understanding of the virus-host interaction and cellular antiviral response.
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Affiliation(s)
- C E Samuel
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106-9610, USA.
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36
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Schneider K, Klaas R, Kaspers B, Staeheli P. Chicken interleukin-6. cDNA structure and biological properties. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:4200-6. [PMID: 11488913 DOI: 10.1046/j.1432-1327.2001.02334.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Suppression subtractive hybridization technology was used to identify differentially expressed genes in spleens of chickens that had been treated with the synthetic immune modifier S-28463. One induced chicken gene encoded a protein with about 35% sequence identity to human interleukin-6 (IL-6). It consists of 241 amino acids including a putative N-terminal signal peptide of 47 residues. Bacterially expressed chicken IL-6 (ChIL-6) carrying a histidine tag in place of the signal peptide was biologically active: it induced proliferation of the IL-6-dependent murine hybridoma cell line 7TD1. The concentration of ChIL-6 required for half-maximal proliferative response was approximately 60 pg.mL-1. When injected intravenously into adult chickens, purified recombinant ChIL-6 induced an increase in serum corticosterone levels. Supernatants of chicken LMH and monkey COS-7 cells transiently transfected with a ChIL-6 expression construct induced proliferation of 7TD1 cells, demonstrating that recombinant ChIL-6 from eukaryotic cells is also active.
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Affiliation(s)
- K Schneider
- Department of Virology, Institut für Medizinische Mikrobiologie und Hygiene, University of Freiburg, Germany
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37
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Krishnan KS, Rikhy R, Rao S, Shivalkar M, Mosko M, Narayanan R, Etter P, Estes PS, Ramaswami M. Nucleoside diphosphate kinase, a source of GTP, is required for dynamin-dependent synaptic vesicle recycling. Neuron 2001; 30:197-210. [PMID: 11343655 DOI: 10.1016/s0896-6273(01)00273-2] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nucleoside diphosphate kinase (NDK), an enzyme encoded by the Drosophila abnormal wing discs (awd) or human nm23 tumor suppressor genes, generates nucleoside triphosphates from respective diphosphates. We demonstrate that NDK regulates synaptic vesicle internalization at the stage where function of the dynamin GTPase is required. awd mutations lower the temperature at which behavioral paralysis, synaptic failure, and blocked membrane internalization occur at dynamin-deficient, shi(ts), mutant nerve terminals. Hypomorphic awd alleles display shi(ts)-like defects. NDK is present at synapses and its enzymatic activity is essential for normal presynaptic function. We suggest a model in which dynamin activity in nerve terminals is highly dependent on NDK-mediated supply of GTP. This connection between NDK and membrane internalization further strengthens an emerging hypothesis that endocytosis, probably of activated growth factor receptors, is an important tumor suppressor activity in vivo.
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Affiliation(s)
- K S Krishnan
- Department of Biological Sciences, Tata Institute for Fundamental Research, Homi Bhabha Road, 400005, Colaba, Bombay, India
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38
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Angell JE, Lindner DJ, Shapiro PS, Hofmann ER, Kalvakolanu DV. Identification of GRIM-19, a novel cell death-regulatory gene induced by the interferon-beta and retinoic acid combination, using a genetic approach. J Biol Chem 2000; 275:33416-26. [PMID: 10924506 DOI: 10.1074/jbc.m003929200] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We show here that the combination of interferon-beta (IFN-beta) and all-trans-retinoic acid (RA) induces the death of tumor cells. To understand the molecular basis for synergistic growth-suppressive action and to identify the gene products that participate in this process, we have employed an antisense knock-out technique. This approach permits the isolation of cell death-associated genes based on their selective inactivation by overexpression of antisense cDNAs. Because the antisense mRNA inactivates gene expression of death-specific genes, transfected cells survive in the presence death inducers. Several Genes associated with Retinoid-IFN-induced Mortality (GRIM) were identified using this approach. Here we report the isolation of a novel GRIM gene, GRIM-19. This 552-base pair cDNA encodes a 16-kDa protein. Antisense expression of GRIM-19 confers a strong resistance against IFN/RA-induced death by reducing the intracellular levels of GRIM-19 protein. Overexpression of GRIM-19 enhances cell death in response to IFN/RA. GRIM-19 is primarily a nuclear protein whose expression is induced by the IFN/RA combination. Together, our studies identify a novel cell death-regulatory molecule.
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Affiliation(s)
- J E Angell
- Greenebaum Cancer Center, Department of Microbiology and Immunology, Molecular and Cellular Biology Program, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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39
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Abstract
MxA is a large, interferon-induced GTPase with antiviral activity against RNA viruses. It forms large oligomers, but whether oligomerization and GTPase activity are important for antiviral function is not known. The mutant protein MxA(L612K) carries a lysine-for-leucine substitution at position 612 and fails to form oligomers. Here we show that monomeric MxA(L612K) lacks detectable GTPase activity but is capable of inhibiting Thogoto virus in transiently transfected Vero cells or in a Thogoto virus minireplicon system. Likewise, MxA(L612K) inhibited vesicular stomatitis virus multiplication. These findings indicate that MxA monomers are antivirally active and suggest that GTP hydrolysis may not be required for antiviral activity. MxA(L612K) is rapidly degraded in cells, whereas wild-type MxA is stable. We propose that high-molecular-weight MxA oligomers represent a stable intracellular pool from which active MxA monomers are recruited.
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Affiliation(s)
- C Janzen
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008 Freiburg, Germany
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40
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Jensen V, Robertsen B. Cloning of an Mx cDNA from Atlantic halibut (Hippoglossus hippoglossus) and characterization of Mx mRNA expression in response to double-stranded RNA or infectious pancreatic necrosis virus. J Interferon Cytokine Res 2000; 20:701-10. [PMID: 10954913 DOI: 10.1089/10799900050116408] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mx proteins are GTPases that are specifically induced by type I interferons (IFN) in vertebrates. Some mammalian Mx proteins have antiviral activity against certain RNA viruses. A 2.3-kb full-length cDNA clone of an Atlantic halibut Mx gene was isolated from a liver cDNA library. The open reading frame (ORF) predicts a 622 amino acid protein of 71.2 kDa possessing a tripartite GTP binding motif, a dynamin signature, and a leucine zipper motif, which are conserved in all known Mx proteins. The C-terminal half contains a putative bipartite nuclear localization signal. The deduced halibut Mx protein showed approximately 76% sequence identity with the Atlantic salmon and rainbow trout Mx proteins, 55% identity with the human MxA, and 48% identity with the chicken Mx protein. Based on sequence comparison of 554-bp Mx cDNA fragments, the Atlantic halibut Mx showed more relationship with the perch and turbot than the salmonid Mx genes. Halibut appears to possess at least two Mx loci, as suggested by Southern blot analysis of genomic DNA. Two halibut Mx transcripts (2.2 kb and 2.6 kb) were strongly induced in vivo by the double-stranded RNA (dsRNA) poly I:C or infectious pancreatic necrosis virus (IPNV) in all organs studied.
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Affiliation(s)
- V Jensen
- The Norwegian College of Fishery Science, University of Tromsø
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41
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Marschall M, Zach A, Hechtfischer A, Foerst G, Meier-Ewert H, Haller O. Inhibition of influenza C viruses by human MxA protein. Virus Res 2000; 67:179-88. [PMID: 10867197 DOI: 10.1016/s0168-1702(00)00140-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Human MxA protein was analyzed for its ability to inhibit the replication of different influenza C viruses. Three laboratory derivatives of viral strain C/Ann Arbor/1/50 were investigated, namely the parental wild-type virus C/AA-wt, the persistent variant C/AA-pi and the highly cytopathogenic variant C/AA-cyt. In addition, strain C/Paris/214/91 isolated from an influenza patient was used. Multiplication of all four viruses was suppressed in MxA-expressing Vero cells, as indicated by a decrease in viral RNA synthesis, viral protein synthesis, virion production and induction of a cytopathic effect. Inhibition correlated with the level of MxA expression. Furthermore, inhibition was independent of cell clone-specific differences in expression of virus receptors, as demonstrated by receptor reconstitution experiments. Thus, human MxA protein has antiviral activity against influenza C viruses.
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Affiliation(s)
- M Marschall
- Institut für Klinische und Molekulare Virologie, Universität Erlangen-Nürnberg, Germany.
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42
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Abstract
Dynamin, a 100-kDa GTPase, is an essential component of vesicle formation in receptor-mediated endocytosis, synaptic vesicle recycling, caveolae internalization, and possibly vesicle trafficking in and out of the Golgi. In addition to the GTPase domain, dynamin also contains a pleckstrin homology domain (PH) implicated in membrane binding, a GTPase effector domain (GED) shown to be essential for self-assembly and stimulated GTPase activity, and a C-terminal proline-rich domain (PRD), which contains several SH3-binding sites. Dynamin partners bind to the PRD and may either stimulate dynamin's GTPase activity or target dynamin to the plasma membrane. Purified dynamin readily self-assembles into rings or spirals. This striking structural property supports the hypothesis that dynamin wraps around the necks of budding vesicles where it plays a key role in membrane fission. The focus of this review is on the relationship between the GTPase and self-assembly properties of dynamin and its cellular function.
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Affiliation(s)
- J E Hinshaw
- Laboratory of Cell Biochemistry and Biology, National Institutes of Health, Bethesda, Maryland 20892, USA.
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43
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Flohr F, Schneider-Schaulies S, Haller O, Kochs G. The central interactive region of human MxA GTPase is involved in GTPase activation and interaction with viral target structures. FEBS Lett 1999; 463:24-8. [PMID: 10601631 DOI: 10.1016/s0014-5793(99)01598-7] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
To define domains of the human MxA GTPase involved in GTP hydrolysis and antiviral activity, we used two monoclonal antibodies (mAb) directed against different regions of the molecule. mAb 2C12 recognizes an epitope in the central interactive region of MxA, whereas mAb M143 is directed against the N-terminal G domain. mAb 2C12 greatly stimulated MxA GTPase activity, suggesting that antibody-mediated crosslinking enhances GTP hydrolysis. In contrast, monovalent Fab fragments of 2C12 abolished GTPase activity, most likely by blocking intramolecular interactions required for GTPase activation. Interestingly, intact IgG molecules and Fab fragments of 2C12 both prevented association of MxA with viral nucleocapsids and neutralized MxA antiviral activity in vivo. mAb M143 had no effect on MxA function, indicating that this antibody binds outside functional regions. These data demonstrate that the central region recognized by 2C12 is critical for regulation of GTPase activity and viral target recognition.
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Affiliation(s)
- F Flohr
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008, Freiburg, Germany
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44
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Praefcke GJ, Geyer M, Schwemmle M, Robert Kalbitzer H, Herrmann C. Nucleotide-binding characteristics of human guanylate-binding protein 1 (hGBP1) and identification of the third GTP-binding motif. J Mol Biol 1999; 292:321-32. [PMID: 10493878 DOI: 10.1006/jmbi.1999.3062] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
hGBP1 is a GTPase with antiviral activity encoded by an interferon- activated human gene. Specific binding of hGBP1 to guanine nucleotides has been established although only two classical GTP-binding motifs were found in its primary sequence. The unique position of hGBP1 amongst known GTPases is further demonstrated by the hydrolysis of GTP to GDP and GMP. Although subsequent cleavage of orthophosphates rather than pyrophosphate was demonstrated, GDP coming from bulk solution cannot serve as a substrate. The relation of guanine nucleotide binding and hydrolysis to the antiviral function of hGBP1 is unknown. Here we show similar binding affinities for all three guanine nucleotides and the ability of both products, GDP and GMP, to compete with GTP binding. Fluorimetry and isothermal titration calorimetry were applied to prove that only one nucleotide binding site is present in hGBP1. Furthermore, we identified the third canonical GTP-binding motif and verified its role in nucleotide recognition by mutational analysis. The high guanine nucleotide dissociation rates measured by stopped-flow kinetics are responsible for the weak affinities to hGBP1 when compared to other GTPases like Ras or Galpha. By means of fluorescence and NMR spectroscopy it is demonstrated that aluminium fluoride forms a complex with hGBP1 only in the GDP state, presumably mimicking the transition state of GTP hydrolysis. Tentatively, the involvement of a GAP domain in hGBP1 in GTP hydrolysis is suggested. These results will serve as a basis for the determination of the differential biological functions of the three nucleotide states and for the elucidation of the unique mechanism of nucleotide hydrolysis catalysed by hGBP1.
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Affiliation(s)
- G J Praefcke
- Abteilung Strukturelle Biologie, Max-Planck-Institut für Molekulare Physiologie, Dortmund, 44202, Germany
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45
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Kochs G, Haller O. Interferon-induced human MxA GTPase blocks nuclear import of Thogoto virus nucleocapsids. Proc Natl Acad Sci U S A 1999; 96:2082-6. [PMID: 10051598 PMCID: PMC26740 DOI: 10.1073/pnas.96.5.2082] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Interferon-induced human MxA protein belongs to the dynamin superfamily of large GTPases. It exhibits antiviral activity against a variety of RNA viruses, including Thogoto virus, an influenza virus-like orthomyxovirus transmitted by ticks. Here, we report that MxA blocks the transport of Thogoto virus nucleocapsids into the nucleus, thereby preventing transcription of the viral genome. This interaction can be abolished by a mAb that neutralizes the antiviral activity of MxA. Our results reveal an antiviral mechanism whereby an interferon-induced protein traps the incoming virus and interferes with proper transport of the viral genome to its ultimate target compartment within the infected cell.
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Affiliation(s)
- G Kochs
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008 Freiburg, Germany
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46
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Abstract
The function of the GTPase dynamin has been discussed for several years. It clearly plays a role in vesicle budding, but, despite recent insights, precisely how it functions in this process is still a matter of debate. In addition, it is now clear that dynamin is a member of a large protein family, present in a variety of cellular locations where members apparently perform a range of functions. This article describes current understanding of the structure and function of the various dynamin family members.
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Affiliation(s)
- A M van der Bliek
- Dept of Biological Chemistry, UCLA School of Medicine 90095-1737, USA.
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47
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Kochs G, Haller O. GTP-bound human MxA protein interacts with the nucleocapsids of Thogoto virus (Orthomyxoviridae). J Biol Chem 1999; 274:4370-6. [PMID: 9933640 DOI: 10.1074/jbc.274.7.4370] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Human MxA protein is an interferon-induced member of the dynamin superfamily of large GTPases. MxA inhibits the multiplication of several RNA viruses, including Thogoto virus, an influenza virus-like orthomyxovirus transmitted by ticks. Previous studies have indicated that GTP binding is required for antiviral activity, but the mechanism of action is still unknown. Here, we have used an in vitro cosedimentation assay to demonstrate, for the first time, a GTP-dependent interaction between MxA GTPase and a viral target structure. The assay is based on highly active MxA GTPase as effector molecules, Thogoto virus nucleocapsids as viral targets, and guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) as a stabilizing factor. We show that MxA tightly interacts with viral nucleocapsids by binding to the nucleoprotein component. This interaction requires the presence of GTPgammaS and is mediated by domains in the carboxyl-terminal moiety of MxA. We propose that GTP-bound MxA adopts an antivirally active conformation that allows interaction with viral nucleocapsids, thereby impairing their normal function.
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Affiliation(s)
- G Kochs
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008 Freiburg, Germany.
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48
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Abstract
Mx proteins are members of a family of interferon-inducible genes expressed when cells are treated with double-stranded RNA or virus infection. These proteins are important components of the antiviral response and form the first line of the body's defense against virus infections. The exact mechanism of action for these proteins has not been discovered, but mice missing the Mx genes are extremely sensitive to influenza virus infection. Mammals have between two and three Mx genes whose functions may vary with regard to the inhibition of a specific virus, cellular localization, and activity. The cDNA of three rainbow trout Mx proteins has been cloned and a comparison of their sequences with that of avian and mammalian species reveals striking conservation of domains. They all maintain the tripartite ATP/GTP binding domain and the dynamin family signature in the amino terminal half of the protein. In the carboxyl terminal half of the Mx proteins are the localization signals and the leucine zipper motifs which account for the trimerization of Mx in the cell. Like the rat and human Mx proteins, the different trout Mx proteins exhibit distinctly different immunohistochemical staining patterns in cells transfected with plasmids expressing RBTMx1, RBTMx2, or RBTMx3. To date, the antiviral function of the trout Mx proteins has not been satisfactorily established.
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Affiliation(s)
- J C Leong
- Department of Microbiology, Oregon State University, Corvallis, USA.
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49
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Schumacher B, Staeheli P. Domains mediating intramolecular folding and oligomerization of MxA GTPase. J Biol Chem 1998; 273:28365-70. [PMID: 9774462 DOI: 10.1074/jbc.273.43.28365] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MxA is an interferon-induced GTPase of human cells that inhibits the multiplication of several RNA viruses by a still poorly understood mechanism. Previous biochemical studies indicated that the C terminus of MxA folds back to form a functional GTP-binding pocket, and that an internal fragment contains a domain required for oligomerization. Using the yeast two-hybrid system, we have now mapped these domains. MxA sequences located downstream of amino acid 564 were found to strongly interact with an internal domain that includes amino acids 372 to 540. This interaction was abolished by mutating phenylalanine 382 or leucine 612, which is part of a leucine zipper motif. Neither the C-terminal nor the internal MxA fragments formed homo-oligomers. Using a mammalian nuclear transport assay that can detect protein-protein interactions, we further found that full-length MxA forms complexes with MxA fragments that include amino acids 372 to 540. This interaction was not observed when phenylalanine 382 was exchanged for alanine or arginine. Furthermore, interaction of two full-length MxA molecules occurred only if at least one of them carried a functional C-terminal leucine zipper motif. These results suggest that C-terminal back-folding and oligomerization are two alternative outcomes of the same type of interaction between the C-terminal and the internal domains of MxA. Intramolecular interaction is believed to result in the formation of MxA monomers, whereas intermolecular interaction may induce the formation of large MxA oligomers.
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Affiliation(s)
- B Schumacher
- Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, University of Freiburg, 79008 Freiburg, Germany
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50
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Abstract
Interferons play key roles in mediating antiviral and antigrowth responses and in modulating immune response. The main signaling pathways are rapid and direct. They involve tyrosine phosphorylation and activation of signal transducers and activators of transcription factors by Janus tyrosine kinases at the cell membrane, followed by release of signal transducers and activators of transcription and their migration to the nucleus, where they induce the expression of the many gene products that determine the responses. Ancillary pathways are also activated by the interferons, but their effects on cell physiology are less clear. The Janus kinases and signal transducers and activators of transcription, and many of the interferon-induced proteins, play important alternative roles in cells, raising interesting questions as to how the responses to the interferons intersect with more general aspects of cellular physiology and how the specificity of cytokine responses is maintained.
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Affiliation(s)
- G R Stark
- Lerner Research Institute, Cleveland Clinic Foundation, Ohio 44195, USA.
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