1
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Rao SS, Skinnemoen L, Fond AKS, Haugland GT. Analyses of the Mx family members in lumpfish: Molecular characterization, phylogeny, and gene expression analyses. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2024; 159:105225. [PMID: 38992732 DOI: 10.1016/j.dci.2024.105225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Revised: 07/05/2024] [Accepted: 07/05/2024] [Indexed: 07/13/2024]
Abstract
Members of the myxovirus resistance (Mx) protein family play an essential role in antiviral immunity. They are Dynamin-like GTPases, induced by interferons. In the current study, we have characterized two predicted MX genes (MX1 and MX2) from lumpfish (Cyclopterus lumpus L.), having 12 and 13 exons, respectively. Mx2 has two isoforms (Mx2-X1 and Mx2-X2) which differ in exon 1. The lumpfish Mx proteins contain an N-terminal Dynamin-like GTPase domain, the middle domain (MD) and GTPase effector domain (GED) characteristic for Mx proteins. Phylogenetic analyses grouped all the lumpfish Mx sequences in group 1, and synteny analyses showed that both genes were localized at chromosome 5 in proximity to the genes Tohc7, Atxn7 and Psmd6. In vitro stimulation experiment showed that both MX1 and MX2-X2 were highly upregulated upon exposure to poly(I:C), but not bacteria, 24 h post exposure, indicating their role in antiviral immunity.
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Affiliation(s)
- Shreesha Sadashiva Rao
- Department of Biological Sciences, Bergen High-Technology Centre, University of Bergen, Bergen, 5006, Norway
| | - Linda Skinnemoen
- Department of Biological Sciences, Bergen High-Technology Centre, University of Bergen, Bergen, 5006, Norway
| | - Amanda Kästel Sandal Fond
- Department of Biological Sciences, Bergen High-Technology Centre, University of Bergen, Bergen, 5006, Norway
| | - Gyri Teien Haugland
- Department of Biological Sciences, Bergen High-Technology Centre, University of Bergen, Bergen, 5006, Norway.
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2
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Sehgal PB, Yuan H, Centone A, DiSenso-Browne SV. Oral Antiviral Defense: Saliva- and Beverage-like Hypotonicity Dynamically Regulate Formation of Membraneless Biomolecular Condensates of Antiviral Human MxA in Oral Epithelial Cells. Cells 2024; 13:590. [PMID: 38607029 PMCID: PMC11011872 DOI: 10.3390/cells13070590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 03/22/2024] [Accepted: 03/27/2024] [Indexed: 04/13/2024] Open
Abstract
The oral mucosa represents a defensive barrier between the external environment and the rest of the body. Oral mucosal cells are constantly bathed in hypotonic saliva (normally one-third tonicity compared to plasma) and are repeatedly exposed to environmental stresses of tonicity, temperature, and pH by the drinks we imbibe (e.g., hypotonic: water, tea, and coffee; hypertonic: assorted fruit juices, and red wines). In the mouth, the broad-spectrum antiviral mediator MxA (a dynamin-family large GTPase) is constitutively expressed in healthy periodontal tissues and induced by Type III interferons (e.g., IFN-λ1/IL-29). Endogenously induced human MxA and exogenously expressed human GFP-MxA formed membraneless biomolecular condensates in the cytoplasm of oral carcinoma cells (OECM1 cell line). These condensates likely represent storage granules in equilibrium with antivirally active dispersed MxA. Remarkably, cytoplasmic MxA condensates were exquisitely sensitive sensors of hypotonicity-the condensates in oral epithelium disassembled within 1-2 min of exposure of cells to saliva-like one-third hypotonicity, and spontaneously reassembled in the next 4-7 min. Water, tea, and coffee enhanced this disassembly. Fluorescence changes in OECM1 cells preloaded with calcein-AM (a reporter of cytosolic "macromolecular crowding") confirmed that this process involved macromolecular uncrowding and subsequent recrowding secondary to changes in cell volume. However, hypertonicity had little effect on MxA condensates. The spontaneous reassembly of GFP-MxA condensates in oral epithelial cells, even under continuous saliva-like hypotonicity, was slowed by the protein-phosphatase-inhibitor cyclosporin A (CsA) and by the K-channel-blocker tetraethylammonium chloride (TEA); this is suggestive of the involvement of the volume-sensitive WNK kinase-protein phosphatase (PTP)-K-Cl cotransporter (KCC) pathway in the regulated volume decrease (RVD) during condensate reassembly in oral cells. The present study identifies a novel subcellular consequence of hypotonic stress in oral epithelial cells, in terms of the rapid and dynamic changes in the structure of one class of phase-separated biomolecular condensates in the cytoplasm-the antiviral MxA condensates. More generally, the data raise the possibility that hypotonicity-driven stresses likely affect other intracellular functions involving liquid-liquid phase separation (LLPS) in cells of the oral mucosa.
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Affiliation(s)
- Pravin B. Sehgal
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA;
- Department of Medicine, New York Medical College, Valhalla, NY 10595, USA
| | - Huijuan Yuan
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA;
| | - Anthony Centone
- Department of Pathology, Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA;
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3
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von der Malsburg A, Sapp GM, Zuccaro KE, von Appen A, Moss FR, Kalia R, Bennett JA, Abriata LA, Dal Peraro M, van der Laan M, Frost A, Aydin H. Structural mechanism of mitochondrial membrane remodelling by human OPA1. Nature 2023; 620:1101-1108. [PMID: 37612504 PMCID: PMC10875962 DOI: 10.1038/s41586-023-06441-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 07/14/2023] [Indexed: 08/25/2023]
Abstract
Distinct morphologies of the mitochondrial network support divergent metabolic and regulatory processes that determine cell function and fate1-3. The mechanochemical GTPase optic atrophy 1 (OPA1) influences the architecture of cristae and catalyses the fusion of the mitochondrial inner membrane4,5. Despite its fundamental importance, the molecular mechanisms by which OPA1 modulates mitochondrial morphology are unclear. Here, using a combination of cellular and structural analyses, we illuminate the molecular mechanisms that are key to OPA1-dependent membrane remodelling and fusion. Human OPA1 embeds itself into cardiolipin-containing membranes through a lipid-binding paddle domain. A conserved loop within the paddle domain inserts deeply into the bilayer, further stabilizing the interactions with cardiolipin-enriched membranes. OPA1 dimerization through the paddle domain promotes the helical assembly of a flexible OPA1 lattice on the membrane, which drives mitochondrial fusion in cells. Moreover, the membrane-bending OPA1 oligomer undergoes conformational changes that pull the membrane-inserting loop out of the outer leaflet and contribute to the mechanics of membrane remodelling. Our findings provide a structural framework for understanding how human OPA1 shapes mitochondrial morphology and show us how human disease mutations compromise OPA1 functions.
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Affiliation(s)
- Alexander von der Malsburg
- Medical Biochemistry & Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University Medical School, Homburg, Germany
| | - Gracie M Sapp
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA
| | - Kelly E Zuccaro
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA
| | - Alexander von Appen
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Frank R Moss
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Altos Labs, Bay Area Institute of Science, San Francisco, CA, USA
| | - Raghav Kalia
- Department of Physiology, University of California, San Francisco, San Francisco, CA, USA
| | - Jeremy A Bennett
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA
| | - Luciano A Abriata
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Protein Production and Structure Core Facility, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Matteo Dal Peraro
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Martin van der Laan
- Medical Biochemistry & Molecular Biology, Center for Molecular Signaling, PZMS, Saarland University Medical School, Homburg, Germany
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA.
- Altos Labs, Bay Area Institute of Science, San Francisco, CA, USA.
- Chan Zuckerberg Biohub, San Francisco, CA, USA.
- Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA, USA.
| | - Halil Aydin
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA.
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4
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The Antiviral Activity of Equine Mx1 against Thogoto Virus Is Determined by the Molecular Structure of Its Viral Specificity Region. J Virol 2023; 97:e0193822. [PMID: 36749070 PMCID: PMC9972912 DOI: 10.1128/jvi.01938-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Mammalian myxovirus resistance (Mx) proteins are interferon-induced, large dynamin-like GTPases with a broad antiviral spectrum. Here, we analyzed the antiviral activity of selected mammalian Mx1 proteins against Thogoto virus (THOV). Of those, equine Mx1 (eqMx1) showed antiviral activity comparable to that of the human MX1 gene product, designated huMxA, whereas most Mx1 proteins were antivirally inactive. We previously demonstrated that the flexible loop L4 protruding from the stalk domain of huMxA, and especially the phenylalanine at position 561 (F561), determines its antiviral specificity against THOV (P. S. Mitchell, C. Patzina, M. Emerman, O. Haller, et al., Cell Host Microbe 12:598-604, 2012, https://doi.org/10.1016/j.chom.2012.09.005). However, despite the similar antiviral activity against THOV, the loop L4 sequence of eqMx1 substantially differs from the one of huMxA. Mutational analysis of eqMx1 L4 identified a tryptophan (W562) and the adjacent glycine (G563) as critical antiviral determinants against THOV, whereas the neighboring residues could be exchanged for nonpolar alanines without affecting the antiviral activity. Further mutational analyses revealed that a single bulky residue at position 562 and the adjacent tiny residue G563 were sufficient for antiviral activity. Moreover, this minimal set of L4 amino acids transferred anti-THOV activity to the otherwise inactive bovine Mx1 (boMx1) protein. Taken together, our data suggest a fairly simple architecture of the antiviral loop L4 that could serve as a mutational hot spot in an evolutionary arms race between Mx-escaping viral variants and their hosts. IMPORTANCE Most mammals encode two paralogs of the interferon-induced Mx proteins: Mx1, with antiviral activity largely against RNA viruses, like orthomyxoviruses and bunyaviruses; and Mx2, which is antivirally active against HIV-1 and herpesviruses. The human Mx1 protein, also called huMxA, is the best-characterized example of mammalian Mx1 proteins and was recently shown to prevent zoonotic virus transmissions. To evaluate the antiviral activity of other mammalian Mx1 proteins, we used Thogoto virus, a tick-transmitted orthomyxovirus, which is efficiently blocked by huMxA. Interestingly, we detected antiviral activity only with equine Mx1 (eqMx1) but not with other nonprimate Mx1 proteins. Detailed functional analysis of eqMx1 identified amino acid residues in the unstructured loop L4 of the stalk domain critical for antiviral activity. The structural insights of the present study explain the unique position of eqMx1 antiviral activity within the collection of nonhuman mammalian Mx1 proteins.
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5
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Kar UP, Dey H, Rahaman A. Cardiolipin targets a dynamin-related protein to the nuclear membrane. eLife 2021; 10:64416. [PMID: 33661098 PMCID: PMC7946437 DOI: 10.7554/elife.64416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 03/03/2021] [Indexed: 12/03/2022] Open
Abstract
Dynamins are targeted to specific cellular membranes that they remodel via membrane fusion or fission. The molecular basis of conferring specificity to dynamins for their target membrane selection is not known. Here, we report a mechanism of nuclear membrane recruitment of Drp6, a dynamin member in Tetrahymena thermophila. Recruitment of Drp6 depends on a domain that binds to cardiolipin (CL)-rich bilayers. Consistent with this, nuclear localization of Drp6 was inhibited either by depleting cellular CL or by substituting a single amino acid residue that abolished Drp6 interactions with CL. Inhibition of CL synthesis, or perturbation in Drp6 recruitment to nuclear membrane, caused defects in the formation of new macronuclei post-conjugation. Taken together, our results elucidate a molecular basis of target membrane selection by a nuclear dynamin and establish the importance of a defined membrane-binding domain and its target lipid in facilitating nuclear expansion.
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Affiliation(s)
- Usha Pallabi Kar
- School of Biological Sciences, National Institute of Science Education and Research-HBNI, Bhubaneswar, India
| | - Himani Dey
- School of Biological Sciences, National Institute of Science Education and Research-HBNI, Bhubaneswar, India
| | - Abdur Rahaman
- School of Biological Sciences, National Institute of Science Education and Research-HBNI, Bhubaneswar, India
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6
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Gao S, Hu J. Mitochondrial Fusion: The Machineries In and Out. Trends Cell Biol 2020; 31:62-74. [PMID: 33092941 DOI: 10.1016/j.tcb.2020.09.008] [Citation(s) in RCA: 164] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 09/10/2020] [Accepted: 09/14/2020] [Indexed: 11/15/2022]
Abstract
Mitochondria are highly dynamic organelles that constantly undergo fission and fusion. Disruption of mitochondrial dynamics undermines their function and causes several human diseases. The fusion of the outer (OMM) and inner mitochondrial membranes (IMM) is mediated by two classes of dynamin-like protein (DLP): mitofusin (MFN)/fuzzy onions 1 (Fzo1) and optic atrophy 1/mitochondria genome maintenance 1 (OPA1/Mgm1). Given the lack of structural information on these fusogens, the molecular mechanisms underlying mitochondrial fusion remain unclear, even after 20 years. Here, we review recent advances in structural studies of the mitochondrial fusion machinery, discuss their implication for DLPs, and summarize the pathogenic mechanisms of disease-causing mutations in mitochondrial fusion DLPs.
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Affiliation(s)
- Song Gao
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, 510060 Guangzhou, China; Guangzhou Regenerative Medicine and Health Guangdong Laboratory, 510530 Guangzhou, China.
| | - Junjie Hu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
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7
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Chen J, Wu Y, Wu XD, Zhou J, Liang XD, Baloch AS, Qiu YF, Gao S, Zhou B. The R614E mutation of mouse Mx1 protein contributes to the novel antiviral activity against classical swine fever virus. Vet Microbiol 2020; 243:108621. [PMID: 32273007 DOI: 10.1016/j.vetmic.2020.108621] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/24/2020] [Accepted: 02/24/2020] [Indexed: 01/07/2023]
Abstract
Mx proteins are interferon-induced GTPases that have broad antiviral activity against a wide range of RNA and DNA viruses. We previously demonstrated that porcine Mx1 protein (poMx1) inhibited the replication of classical swine fever virus (CSFV), an economically important Pestivirus, and that mouse Mx1 did so as well. It is unknown why the nucleus-localizing mouse Mx1 inhibits CSFV replication which occurs in the cytoplasm. To the end, we assessed the anti-CSFV actions of wild type mouse Mx1 and seven previously reported mutants (K49A, G83R, A222V, A516V, G540E, R614E and ΔL4) and identified the molecular mechanism of R614E action against CSFV replication. A series of experiments revealed that mmMx1 (R614E) mutant reposted to the cytoplasm and interacted with the CSFV nucleocapsid protein (Core), thereby inhibiting viral replication. These findings broaden our understanding of the function of Mx protein family members against CSFV and suggest that the relative conservation of Mx1 among species is the basis of broad-spectrum antiviral properties.
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Affiliation(s)
- Jing Chen
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Yue Wu
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xu-Dan Wu
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Jing Zhou
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xiao-Dong Liang
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Abdul Sattar Baloch
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Ya-Feng Qiu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, 200241, China
| | - Song Gao
- the Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, and Collaborative Innovation Center for Cancer Medicine, Guangzhou, 510060, China
| | - Bin Zhou
- MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.
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8
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Cao H, Krueger EW, Chen J, Drizyte-Miller K, Schulz ME, McNiven MA. The anti-viral dynamin family member MxB participates in mitochondrial integrity. Nat Commun 2020; 11:1048. [PMID: 32102993 PMCID: PMC7044337 DOI: 10.1038/s41467-020-14727-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 01/23/2020] [Indexed: 12/19/2022] Open
Abstract
The membrane deforming dynamin family members MxA and MxB are large GTPases that convey resistance to a variety of infectious viruses. During viral infection, Mx proteins are known to show markedly increased expression via an interferon-responsive promoter to associate with nuclear pores. In this study we report that MxB is an inner mitochondrial membrane GTPase that plays an important role in the morphology and function of this organelle. Expression of mutant MxB or siRNA knockdown of MxB leads to fragmented mitochondria with disrupted inner membranes that are unable to maintain a proton gradient, while expelling their nucleoid-based genome into the cytoplasm. These findings implicate a dynamin family member in mitochondrial-based changes frequently observed during an interferon-based, anti-viral response. Mx proteins belong to the dynamin family of large GTPases and are highly induced by interferon in virally infected cells. The authors show that uninfected immune cells and hepatocytes also express MxB protein that associates with mitochondria to alter the morphology and genome of this organelle.
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Affiliation(s)
- Hong Cao
- Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA.,Center for Basic Research in Digestive Diseases, Division of Gastroenterology & Hepatology, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA
| | - E W Krueger
- Center for Basic Research in Digestive Diseases, Division of Gastroenterology & Hepatology, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA
| | - Jing Chen
- Center for Basic Research in Digestive Diseases, Division of Gastroenterology & Hepatology, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA
| | - Kristina Drizyte-Miller
- Biochemistry and Molecular Biology Program, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA
| | - Mary E Schulz
- Center for Basic Research in Digestive Diseases, Division of Gastroenterology & Hepatology, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA
| | - Mark A McNiven
- Department of Biochemistry and Molecular Biology, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA. .,Center for Basic Research in Digestive Diseases, Division of Gastroenterology & Hepatology, Mayo Clinic, 200 1st Street SW, Rochester, MN, 55905, USA.
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9
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Haller O, Kochs G. Mx genes: host determinants controlling influenza virus infection and trans-species transmission. Hum Genet 2019; 139:695-705. [PMID: 31773252 PMCID: PMC7087808 DOI: 10.1007/s00439-019-02092-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 11/19/2019] [Indexed: 12/13/2022]
Abstract
The human MxA protein, encoded by the interferon-inducible MX1 gene, is an intracellular influenza A virus (IAV) restriction factor. It can protect transgenic mice from severe IAV-induced disease, indicating a key role of human MxA for host survival and suggesting that natural variations in MX1 may account for inter-individual differences in disease severity among humans. MxA also provides a robust barrier against zoonotic transmissions of avian and swine IAV strains. Therefore, zoonotic IAV must acquire MxA escape mutations to achieve sustained human-to-human transmission. Here, we discuss recent progress in the field.
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Affiliation(s)
- Otto Haller
- Institute of Virology, Medical Center, University of Freiburg, Freiburg, Germany. .,Faculty of Medicine, University of Freiburg, Freiburg, Germany. .,Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.
| | - Georg Kochs
- Institute of Virology, Medical Center, University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
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10
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Human Antiviral Protein MxA Forms Novel Metastable Membraneless Cytoplasmic Condensates Exhibiting Rapid Reversible Tonicity-Driven Phase Transitions. J Virol 2019; 93:JVI.01014-19. [PMID: 31484749 DOI: 10.1128/jvi.01014-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 08/28/2019] [Indexed: 12/13/2022] Open
Abstract
Phase-separated biomolecular condensates of proteins and nucleic acids form functional membrane-less organelles (e.g., stress granules and P-bodies) in the mammalian cell cytoplasm and nucleus. In contrast to the long-standing belief that interferon (IFN)-inducible human myxovirus resistance protein A (MxA) associated with the endoplasmic reticulum (ER) and Golgi apparatus, we report that MxA formed membraneless metastable (shape-changing) condensates in the cytoplasm. In our studies, we used the same cell lines and methods as those used by previous investigators but concluded that wild-type MxA formed variably sized spherical or irregular bodies, filaments, and even a reticulum distinct from that of ER/Golgi membranes. Moreover, in Huh7 cells, MxA structures associated with a novel cytoplasmic reticular meshwork of intermediate filaments. In live-cell assays, 1,6-hexanediol treatment led to rapid disassembly of green fluorescent protein (GFP)-MxA structures; FRAP revealed a relative stiffness with a mobile fraction of 0.24 ± 0.02 within condensates, consistent with a higher-order MxA network structure. Remarkably, in intact cells, GFP-MxA condensates reversibly disassembled/reassembled within minutes of sequential decrease/increase, respectively, in tonicity of extracellular medium, even in low-salt buffers adjusted only with sucrose. Condensates formed from IFN-α-induced endogenous MxA also displayed tonicity-driven disassembly/reassembly. In vesicular stomatitis virus (VSV)-infected Huh7 cells, the nucleocapsid (N) protein, which participates in forming phase-separated viral structures, associated with spherical GFP-MxA condensates in cells showing an antiviral effect. These observations prompt comparisons with the extensive literature on interactions between viruses and stress granules/P-bodies. Overall, the new data correct a long-standing misinterpretation in the MxA literature and provide evidence for membraneless MxA biomolecular condensates in the uninfected cell cytoplasm.IMPORTANCE There is a long-standing belief that interferon (IFN)-inducible human myxovirus resistance protein A (MxA), which displays antiviral activity against several RNA and DNA viruses, associates with the endoplasmic reticulum (ER) and Golgi apparatus. We provide data to correct this misinterpretation and further report that MxA forms membraneless metastable (shape-changing) condensates in the cytoplasm consisting of variably sized spherical or irregular bodies, filaments, and even a reticulum. Remarkably, MxA condensates showed the unique property of rapid (within 1 to 3 min) reversible disassembly and reassembly in intact cells exposed sequentially to hypotonic and isotonic conditions. Moreover, GFP-MxA condensates included the VSV nucleocapsid (N) protein, a protein previously shown to form liquid-like condensates. Since intracellular edema and ionic changes are hallmarks of cytopathic effects of a viral infection, the tonicity-driven regulation of MxA condensates may reflect a mechanism for modulation of MxA function during viral infection.
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11
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Lee S, Ishitsuka A, Noguchi M, Hirohama M, Fujiyasu Y, Petric PP, Schwemmle M, Staeheli P, Nagata K, Kawaguchi A. Influenza restriction factor MxA functions as inflammasome sensor in the respiratory epithelium. Sci Immunol 2019; 4:4/40/eaau4643. [DOI: 10.1126/sciimmunol.aau4643] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 06/21/2019] [Accepted: 09/19/2019] [Indexed: 12/20/2022]
Abstract
The respiratory epithelium is exposed to the environment and initiates inflammatory responses to exclude pathogens. Influenza A virus (IAV) infection triggers inflammatory responses in the respiratory mucosa, but the mechanisms of inflammasome activation are poorly understood. We identified MxA as a functional inflammasome sensor in respiratory epithelial cells that recognizes IAV nucleoprotein and triggers the formation of ASC (apoptosis-associated speck-like protein containing a CARD) specks via interaction of its GTPase domain with the PYD domain of ASC. ASC specks were present in bronchiolar epithelial cells of IAV-infected MxA-transgenic mice, which correlated with early IL-1β production and early recruitment of granulocytes in the lungs of infected mice. Collectively, these results demonstrate that MxA contributes to IAV resistance by triggering a rapid inflammatory response in infected respiratory epithelial cells.
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12
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Smaczynska-de Rooij II, Marklew CJ, Palmer SE, Allwood EG, Ayscough KR. Mutation of key lysine residues in the Insert B region of the yeast dynamin Vps1 disrupts lipid binding and causes defects in endocytosis. PLoS One 2019; 14:e0215102. [PMID: 31009484 PMCID: PMC6476499 DOI: 10.1371/journal.pone.0215102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/26/2019] [Indexed: 12/20/2022] Open
Abstract
The yeast dynamin-like protein Vps1 has roles at multiple stages of membrane trafficking including Golgi to vacuole transport, endosomal recycling, endocytosis and in peroxisomal fission. While the majority of the Vps1 amino acid sequence shows a high level of identity with the classical mammalian dynamins, it does not contain a pleckstrin homology domain (PH domain). The Dyn1 PH domain has been shown to bind to lipids with a preference for PI(4,5)P2 and it is considered central to the function of Dyn1 in endocytosis. The lack of a PH domain in Vps1 has raised questions as to whether the protein can function directly in membrane fusion or fission events. Here we demonstrate that the region Insert B, located in a position equivalent to the dynamin PH domain, is able to bind directly to lipids and that mutation of three lysine residues reduces its capacity to interact with lipids, and in particular with PI(4,5)P2. The Vps1 KKK-AAA mutant shows more diffuse staining but does still show some localization to compartments adjacent to vacuoles and to endocytic sites suggesting that other factors are also involved in its recruitment. This mutant selectively blocks endocytosis, but is functional in other processes tested. While mutant Vps1 can localise to endocytic sites, the mutation results in a significant increase in the lifetime of the endocytic reporter Sla2 and a high proportion of defective scission events. Together our data indicate that the lipid binding capacity of the Insert B region of Vps1 contributes to the ability of the protein to associate with membranes and that its capacity to interact with PI(4,5)P2 is important in facilitating endocytic scission.
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Affiliation(s)
| | | | - Sarah E. Palmer
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Ellen G. Allwood
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail: (EGA); (KRA)
| | - Kathryn R. Ayscough
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- * E-mail: (EGA); (KRA)
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13
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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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14
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Stanishneva-Konovalova TB, Sokolova OS. Effects of PI(4,5)P 2 concentration on the F-BAR domain membrane binding as revealed by coarse-grained simulations. Proteins 2019; 87:561-568. [PMID: 30803020 DOI: 10.1002/prot.25678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 01/22/2019] [Accepted: 02/20/2019] [Indexed: 11/09/2022]
Abstract
Bin/Amphyphysin/Rvs (BAR) domain proteins form a key link between membrane remodeling and cytoskeleton dynamics. They are dimers that bind to membranes via electrostatic interactions with different preferences toward negatively charged lipids. In the present article, we examine the interactions of the F-BAR domain of nervous wreck (Nwk) with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2 )-containing membranes using coarse-grained molecular dynamics. We demonstrated PI(4,5)P2 concentration effects, identified the sequence of events that underlies the protein binding and identified amino acids involved in protein-lipid interactions. Our simulations point out the primary role of the basic stretch at the tips of the dimer, which anchors the protein to the membrane and initiates the binding process. When the PI(4,5)P2 concentration is high, the protein stably associates with the membrane by its concave surface or by the opposite side. At low PI(4,5)P2 concentration, the former orientation becomes more favorable; also a state with only one tip bound is observed, due to the weaker attachment and more pronounced association/dissociation events. Our results provide a theoretical model that describes the lipid-binding behavior of Nwk observed in vitro.
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Affiliation(s)
| | - Olga S Sokolova
- Department of Bioengineering, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
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15
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Zav'yalov VP, Hämäläinen-Laanaya H, Korpela TK, Wahlroos T. Interferon-Inducible Myxovirus Resistance Proteins: Potential Biomarkers for Differentiating Viral from Bacterial Infections. Clin Chem 2018; 65:739-750. [PMID: 30593466 PMCID: PMC7108468 DOI: 10.1373/clinchem.2018.292391] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 08/29/2018] [Indexed: 12/31/2022]
Abstract
BACKGROUND In 2015, the 68th World Health Assembly declared that effective, rapid, low-cost diagnostic tools were needed for guiding optimal use of antibiotics in medicine. This review is devoted to interferon-inducible myxovirus resistance proteins as potential biomarkers for differentiating viral from bacterial infections. CONTENT After viral infection, a branch of the interferon (IFN)-induced molecular reactions is triggered by the binding of IFNs with their receptors, a process leading to the activation of mx1 and mx2, which produce antiviral Mx proteins (MxA and MxB). We summarize current knowledge of the structures and functions of type I and III IFNs. Antiviral mechanisms of Mx proteins are discussed in reference to their structural and functional data to provide an in-depth picture of protection against viral attacks. Knowing such a mechanism may allow the development of countermeasures and the specific detection of any viral infection. Clinical research data indicate that Mx proteins are biomarkers for many virus infections, with some exceptions, whereas C-reactive protein (CRP) and procalcitonin have established positions as general biomarkers for bacterial infections. SUMMARY Mx genes are not directly induced by viruses and are not expressed constitutively; their expression strictly depends on IFN signaling. MxA protein production in peripheral blood cells has been shown to be a clinically sensitive and specific marker for viral infection. Viral infections specifically increase MxA concentrations, whereas viruses have only a modest increase in CRP or procalcitonin concentrations. Therefore, comparison of MxA and CRP and/or procalcitonin values can be used for the differentiation of infectious etiology.
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Affiliation(s)
| | | | - Timo K Korpela
- Department of Future Technologies, University of Turku, Turku, Finland
| | - Tony Wahlroos
- Laboratory of Clinical Research, Labmaster Ltd., Turku, Finland
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16
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Ringer K, Riehl J, Müller M, Dewes J, Hoff F, Jacob R. The large GTPase Mx1 binds Kif5B for cargo transport along microtubules. Traffic 2018; 19:947-964. [DOI: 10.1111/tra.12616] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 09/18/2018] [Accepted: 09/18/2018] [Indexed: 01/29/2023]
Affiliation(s)
- Karina Ringer
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Marburg Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling; Philipps University of Marburg; Marburg Germany
| | - Jana Riehl
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Marburg Germany
| | - Manuel Müller
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Marburg Germany
| | - Jenny Dewes
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Marburg Germany
| | - Florian Hoff
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Marburg Germany
| | - Ralf Jacob
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Marburg Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling; Philipps University of Marburg; Marburg Germany
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17
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Chen S, Zeng M, Liu P, Yang C, Wang M, Jia R, Zhu D, Liu M, Yang Q, Wu Y, Zhao X, Cheng A. The 125th Lys and 145th Thr Amino Acids in the GTPase Domain of Goose Mx Confer Its Antiviral Activity against the Tembusu Virus. Viruses 2018; 10:v10070361. [PMID: 29986463 PMCID: PMC6070871 DOI: 10.3390/v10070361] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 06/29/2018] [Accepted: 07/04/2018] [Indexed: 12/14/2022] Open
Abstract
The Tembusu virus (TMUV) is an avian pathogenic flavivirus that causes a highly contagious disease and catastrophic losses to the poultry industry. The myxovirus resistance protein (Mx) of innate immune effectors is a key antiviral “workhorse” of the interferon (IFN) system. Although mammalian Mx resistance against myxovirus and retrovirus was witnessed for decades, whether or not bird Mx has anti-flavivirus activity remains unknown. In this study, we found that the transcription of goose Mx (goMx) was obviously driven by TMUV infection, both in vivo and in vitro, and that the titers and copies of TMUV were significantly reduced by goMx overexpression. In both primary (goose embryo fibroblasts, GEFs) and passaged cells (baby hamster kidney cells, BHK21, and human fetal kidney cells, HEK 293T), it was shown that goMx was mainly located in the cytoplasm, and sporadically distributed in the nucleus. The intracellular localization of this protein is attributed to the predicted bipartite nuclear localization signal (NLS; 30 residues: the 441st–471st amino acids of goMx). Intuitively, it seems that the cells with a higher level of goMx expression tend to have lower TMUV loads in the cytoplasm, as determined by an immunofluorescence assay. To further explore the antiviral determinants, a panel of variants was constructed. Two amino acids at the 125th (Lys) and 145th (Thr) positions in GTP-binding elements, not in the L4 loop (40 residues: the 532nd–572nd amino acids of goMx), were vital for the antiviral function of goMx against TMUV in vitro. These findings will contribute to our understanding of the functional significance of the antiviral system in aquatic birds, and the development of goMx could be a valuable therapeutic agent against TMUV.
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Affiliation(s)
- Shun Chen
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Miao Zeng
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
| | - Peng Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
| | - Chao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
| | - Mingshu Wang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Renyong Jia
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Dekang Zhu
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Mafeng Liu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Qiao Yang
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Ying Wu
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Xinxin Zhao
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
| | - Anchun Cheng
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang District, Chengdu 611130, Sichuan, China.
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, Sichuan, China.
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18
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Porcine Mx1 Protein Inhibits Classical Swine Fever Virus Replication by Targeting Nonstructural Protein NS5B. J Virol 2018; 92:JVI.02147-17. [PMID: 29343573 DOI: 10.1128/jvi.02147-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 01/09/2018] [Indexed: 12/16/2022] Open
Abstract
Mx proteins are interferon (IFN)-induced GTPases that have broad antiviral activity against a wide range of RNA and DNA viruses; they belong to the dynamin superfamily of large GTPases. In this study, we confirmed the anti-classical swine fever virus (CSFV) activity of porcine Mx1 in vitro and showed that porcine Mx2 (poMx2), human MxA (huMxA), and mouse Mx1 (mmMx1) also have anti-CSFV activity in vitro Small interfering RNA (siRNA) experiments revealed that depletion of endogenous poMx1 or poMx2 enhanced CSFV replication, suggesting that porcine Mx proteins are responsible for the antiviral activity of interferon alpha (IFN-α) against CSFV infection. Confocal microscopy, immunoprecipitation, glutathione S-transferase (GST) pulldown, and bimolecular fluorescence complementation (BiFC) demonstrated that poMx1 associated with NS5B, the RNA-dependent RNA polymerase (RdRp) of CSFV. We used mutations in the poMx1 protein to elucidate the mechanism of their anti-CSFV activity and found that mutants that disrupted the association with NS5B lost all anti-CSV activity. Moreover, an RdRp activity assay further revealed that poMx1 undermined the RdRp activities of NS5B. Together, these results indicate that porcine Mx proteins exert their antiviral activity against CSFV by interacting with NS5B.IMPORTANCE Our previous studies have shown that porcine Mx1 (poMx1) inhibits classical swine fever virus (CSFV) replication in vitro and in vivo, but the molecular mechanism of action remains largely unknown. In this study, we dissect the molecular mechanism of porcine Mx1 and Mx2 against CSFV in vitro Our results show that poMx1 associates with NS5B, the RNA-dependent RNA polymerase of CSFV, resulting in the reduction of CSFV replication. Moreover, the mutants of poMx1 further elucidate the mechanism of their anti-CSFV activities.
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19
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Kar UP, Dey H, Rahaman A. Tetrahymena dynamin-related protein 6 self-assembles independent of membrane association. J Biosci 2018; 43:139-148. [PMID: 29485122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Self-assembly on target membranes is one of the important properties of all dynamin family proteins. Drp6, a dynaminrelated protein in Tetrahymena, controls nuclear remodelling and undergoes cycles of assembly/disassembly on the nuclear envelope. To elucidate the mechanism of Drp6 function, we have characterized its biochemical and biophysical properties using size exclusion chromatography, chemical cross-linking and electron microscopy. The results demonstrate that Drp6 readily forms high-molecular-weight self-assembled structures as determined by size exclusion chromatography and chemical cross-linking. Negative stain electron microscopy revealed that Drp6 assembles into rings and spirals at physiological ionic strength. We have also shown that the recombinant Drp6 expressed in bacteria is catalytically active and its GTPase activity is not enhanced by low salt. These results suggest that, in contrast to dynamins but similar to MxA, Drp6 self-assembles in the absence of membrane templates, and its GTPase activity is not affected by ionic strength of the buffer. We discuss the self-assembly structure of Drp6 and explain the basis for lack of membrane-stimulated GTPase activity.
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Affiliation(s)
- Usha P Kar
- School of Biological Sciences, National Institute of Science Education and Research-HBNI, Bhubaneswar, India
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20
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Dornfeld D, Dudek AH, Vausselin T, Günther SC, Hultquist JF, Giese S, Khokhlova-Cubberley D, Chew YC, Pache L, Krogan NJ, Garcia-Sastre A, Schwemmle M, Shaw ML. SMARCA2-regulated host cell factors are required for MxA restriction of influenza A viruses. Sci Rep 2018; 8:2092. [PMID: 29391557 PMCID: PMC5794779 DOI: 10.1038/s41598-018-20458-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 01/18/2018] [Indexed: 11/29/2022] Open
Abstract
The human interferon (IFN)-induced MxA protein is a key antiviral host restriction factor exhibiting broad antiviral activity against many RNA viruses, including highly pathogenic avian influenza A viruses (IAV) of the H5N1 and H7N7 subtype. To date the mechanism for how MxA exerts its antiviral activity is unclear, however, additional cellular factors are believed to be essential for this activity. To identify MxA cofactors we performed a genome-wide siRNA-based screen in human airway epithelial cells (A549) constitutively expressing MxA using an H5N1 reporter virus. These data were complemented with a proteomic screen to identify MxA-interacting proteins. The combined data identified SMARCA2, the ATPase subunit of the BAF chromatin remodeling complex, as a crucial factor required for the antiviral activity of MxA against IAV. Intriguingly, our data demonstrate that although SMARCA2 is essential for expression of some IFN-stimulated genes (ISGs), and the establishment of an antiviral state, it is not required for expression of MxA, suggesting an indirect effect on MxA activity. Transcriptome analysis of SMARCA2-depleted A549-MxA cells identified a small set of SMARCA2-regulated factors required for activity of MxA, in particular IFITM2 and IGFBP3. These findings reveal that several virus-inducible factors work in concert to enable MxA restriction of IAV.
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Affiliation(s)
- Dominik Dornfeld
- Institute of Virology, Medical Center, University of Freiburg, 79104, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany
| | - Alexandra H Dudek
- Institute of Virology, Medical Center, University of Freiburg, 79104, Freiburg, Germany
- Spemann Graduate School of Biology and Medicine, University of Freiburg, 79104, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany
- Faculty of Biology, University of Freiburg, 79104, Freiburg, Germany
| | - Thibaut Vausselin
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Sira C Günther
- Institute of Virology, Medical Center, University of Freiburg, 79104, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany
| | - Judd F Hultquist
- Quantitative Biosciences Institute, QBI, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, 94158, USA
- J. David Gladstone Institutes, San Francisco, CA, 94158, USA
| | - Sebastian Giese
- Institute of Virology, Medical Center, University of Freiburg, 79104, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany
| | | | - Yap C Chew
- Zymo Research Corp, Irvine, CA, 92614, USA
| | - Lars Pache
- Sanford Burnham Prebys Medical Discovery Institute, Infectious and Inflammatory Disease Center, 10901 North Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Nevan J Krogan
- Quantitative Biosciences Institute, QBI, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA, 94158, USA
- J. David Gladstone Institutes, San Francisco, CA, 94158, USA
| | - Adolfo Garcia-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
- Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
- Department of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
| | - Martin Schwemmle
- Institute of Virology, Medical Center, University of Freiburg, 79104, Freiburg, Germany.
- Faculty of Medicine, University of Freiburg, 79104, Freiburg, Germany.
| | - Megan L Shaw
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
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21
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Interferon induced Mx protein from Indian snow trout Schizothorax richardsonii (Gray) lacks critical functional features unlike its mammalian homologues. Comput Biol Chem 2018; 73:31-40. [PMID: 29413814 DOI: 10.1016/j.compbiolchem.2017.12.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 11/16/2017] [Accepted: 12/30/2017] [Indexed: 11/21/2022]
Abstract
Viral attack within host cells triggers the production of type I interferons and leads to the induction of interferon stimulated genes (ISGs). One of the ISG Mx, encodes type I interferon inducible GTPase that is responsible for the establishment of an anti-viral state within cells. Intriguingly, several isoforms of Mx have been reported in fish, but the structural analysis of fish Mx proteins remains unexplored. For the first time, we have identified and unraveled the molecular structure of Mx protein from Indian snow trout, Schizothorax richardsonii (Gray) a Coldwater fish that inhabits the water bodies in the sub-Himalayan region. The snow trout Mx coding region consists of 2518 nucleotides with an open reading frame (ORF) of 1854 nucleotides. It codes for a polypeptide of 617 amino acids with a predicted molecular weight of 70 kDa. In silico analysis of snow trout Mx protein revealed signature of dynamin family (LPRGTGIVTR) along with a tripartite GTP-binding domain (GDQSSGKS, DLPG, and TKPD). Homology modelling established that the Mx protein is an elongated structure with a G domain, bundle signaling element (BSE) and a GTPase effector domain (GED). Moreover, the GED of Mx contains two highly conserved leucine zippers at the COOH-terminal of the protein suggesting its structural similarity with human homologues. However, snow trout Mx lacks the essential features of its mammalian homologues questioning its functional characteristics. Further, a ligand binding site in the said protein has also been predicted adjacent to the GTPase switch within the G domain.
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22
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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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23
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Conformational dynamics of dynamin-like MxA revealed by single-molecule FRET. Nat Commun 2017; 8:15744. [PMID: 28548099 PMCID: PMC5458555 DOI: 10.1038/ncomms15744] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 04/25/2017] [Indexed: 12/14/2022] Open
Abstract
Human myxovirus resistance protein 1 (MxA) restricts a wide range of viruses and is closely related to the membrane-remodelling GTPase dynamin. The functions of MxA rely on domain rearrangements coupled with GTP hydrolysis cycles. To gain insight into this process, we studied real-time domain dynamics of MxA by single-molecule fluorescence resonance energy transfer. We find that the GTPase domain-bundle-signalling-element (BSE) region can adopt either an ‘open' or a ‘closed' conformation in all nucleotide-loading conditions. Whereas the open conformation is preferred in nucleotide-free, GDP·AlF4−-bound and GDP-bound forms, loading of GTP activates the relative movement between the two domains and alters the conformational preference to the ‘closed' state. Moreover, frequent relative movement was observed between BSE and stalk via hinge 1. On the basis of these results, we suggest how MxA molecules within a helical polymer collectively generate a stable torque through random GTP hydrolysis cycles. Our study provides mechanistic insights into fundamental cellular events such as viral resistance and endocytosis. MxA (myxovirus resistance protein A) is a viral restriction factor whose activity depends on self-assembly into polymeric rings and helical filaments. Here the authors reveal the conformational movements involved in generating torque within polymeric MxA molecules and the dynamic conformational changes that occur upon GTP loading and hydrolysis.
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24
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Zhou J, Wang SQ, Wei JC, Zhang XM, Gao ZC, Liu K, Ma ZY, Chen PY, Zhou B. Mx Is Not Responsible for the Antiviral Activity of Interferon-α against Japanese Encephalitis Virus. Viruses 2017; 9:v9010005. [PMID: 28075421 PMCID: PMC5294974 DOI: 10.3390/v9010005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 12/14/2016] [Accepted: 12/28/2016] [Indexed: 12/11/2022] Open
Abstract
Mx proteins are interferon (IFN)-induced dynamin-like GTPases that are present in all vertebrates and inhibit the replication of myriad viruses. However, the role Mx proteins play in IFN-mediated suppression of Japanese encephalitis virus (JEV) infection is unknown. In this study, we set out to investigate the effects of Mx1 and Mx2 expression on the interferon-α (IFNα) restriction of JEV replication. To evaluate whether the inhibitory activity of IFNα on JEV is dependent on Mx1 or Mx2, we knocked down Mx1 or Mx2 with siRNA in IFNα-treated PK-15 cells and BHK-21 cells, then challenged them with JEV; the production of progeny virus was assessed by plaque assay, RT-qPCR, and Western blotting. Our results demonstrated that depletion of Mx1 or Mx2 did not affect JEV restriction imposed by IFNα, although these two proteins were knocked down 66% and 79%, respectively. Accordingly, expression of exogenous Mx1 or Mx2 did not change the inhibitory activity of IFNα to JEV. In addition, even though virus-induced membranes were damaged by Brefeldin A (BFA), overexpressing porcine Mx1 or Mx2 did not inhibit JEV proliferation. We found that BFA inhibited JEV replication, not maturation, suggesting that BFA could be developed into a novel antiviral reagent. Collectively, our findings demonstrate that IFNα inhibits JEV infection by Mx-independent pathways.
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Affiliation(s)
- Jing Zhou
- Key Laboratory of Animal Diseases Diagnosis and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
| | - Shi-Qi Wang
- Key Laboratory of Animal Diseases Diagnosis and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
| | - Jian-Chao Wei
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Science, Shanghai 200241, China.
| | - Xiao-Min Zhang
- Key Laboratory of Animal Diseases Diagnosis and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
| | - Zhi-Can Gao
- Key Laboratory of Animal Diseases Diagnosis and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
| | - Ke Liu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Science, Shanghai 200241, China.
| | - Zhi-Yong Ma
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Science, Shanghai 200241, China.
| | - Pu-Yan Chen
- Key Laboratory of Animal Diseases Diagnosis and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
| | - Bin Zhou
- Key Laboratory of Animal Diseases Diagnosis and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China.
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25
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Yuan H, Sehgal PB. MxA Is a Novel Regulator of Endosome-Associated Transcriptional Signaling by Bone Morphogenetic Proteins 4 and 9 (BMP4 and BMP9). PLoS One 2016; 11:e0166382. [PMID: 27875556 PMCID: PMC5119740 DOI: 10.1371/journal.pone.0166382] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/27/2016] [Indexed: 01/02/2023] Open
Abstract
There is confusion about the role that IFN-α plays in the pathogenesis of pulmonary arterial hypertension (PAH) with different investigators reporting a causative or a protective role. There is now clear evidence in PAH pathogenesis for the involvement of BMP4 and BMP9 signaling, and its disruption by mutations in BMPR2. In the present study, we investigated MxA, an IFN-α-inducible cytoplasmic dynamin-family GTPase for effects on BMP4/9 signaling, including in the presence of PAH-disease-associated mutants of BMPR2. In human pulmonary arterial endothelial cells (HPAECs), IFN-α-induced endogenous as well as exogenously expressed MxA was associated with endosomes that aligned alongside microtubules and tubules of the endoplasmic reticulum (ER). Moreover, IFN-α and MxA stimulated basal and BMP4/9 signaling to a Smad1/5/8-responsive pBRE-Luc reporter. In HEK293T cells, immunoelectron microscopy confirmed the association of MxA with endosomes, and immunofluorescence methods showed these to be positive for early endosome markers (early endosomal antigen 1, clathrin light chain and Rab5) and RSmad1/5/8. Functionally, using different genetic and inhibitor approaches, we observed that clathrin-mediated endocytosis enhanced and caveolin-mediated endocytosis inhibited the transcriptional response to BMP4 and BMP9. MxA produced a further 3-4-fold enhancement of the BMP-induced response in a clathrin-endocytosis dependent manner. The microtubule inhibitor nocodazole and stabilizer paclitaxel respectively attenuated and enhanced the effect of MxA, implicating microtubule integrity in this process. MxA enhanced BMP-induced signaling in the presence of wild-type BMPR2, and partially rescued signaling from some PAH-disease-associated BMPR2 mutants. Taken together, the data identify MxA as a novel stimulator of BMP4 and BMP9 transcriptional signaling, and suggest it to be a candidate IFN-α-inducible mechanism that might have a protective role against development of PAH and other vascular diseases.
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Affiliation(s)
- Huijuan Yuan
- Department of. Cell Biology & Anatomy, New York Medical College, Valhalla, New York, United States of America
| | - Pravin B. Sehgal
- Department of. Cell Biology & Anatomy, and Department of Medicine, New York Medical College, Valhalla, New York, United States of America
- * E-mail:
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Abstract
Myxovirus resistance proteins represent a family of interferon-induced restriction factors of the innate and adaptive immune system. Human MxB acts as a novel restriction factor with antiviral activity against a range of HIV-1 and other retroviruses mainly by inhibiting the uncoating process after reverse transcription but prior to integration. Based on published data and conservation analysis, we propose a novel hypothesis, in which MxB dimers form higher order oligomers that restrict retroviral replication by binding to the viral capsid. Insights into the mechanistic basis of structural and functional characteristics of MxB will greatly advance our understanding of MxB.
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Affiliation(s)
- Jia Kong
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.,School of Life Sciences, Tianjin University, Tianjin 300072, China.,State Key Laboratory of Medicinal Chemical Biology, NanKai University, Tianjin 300071, China
| | - Min Ma
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.,School of Life Sciences, Tianjin University, Tianjin 300072, China.,State Key Laboratory of Medicinal Chemical Biology, NanKai University, Tianjin 300071, China
| | - Shuangyi He
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.,School of Life Sciences, Tianjin University, Tianjin 300072, China.,State Key Laboratory of Medicinal Chemical Biology, NanKai University, Tianjin 300071, China
| | - Xiaohong Qin
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.,School of Life Sciences, Tianjin University, Tianjin 300072, China.,State Key Laboratory of Medicinal Chemical Biology, NanKai University, Tianjin 300071, China
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27
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Daumke O, Praefcke GJK. Invited review: Mechanisms of GTP hydrolysis and conformational transitions in the dynamin superfamily. Biopolymers 2016; 105:580-93. [PMID: 27062152 PMCID: PMC5084822 DOI: 10.1002/bip.22855] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/31/2016] [Accepted: 04/01/2016] [Indexed: 12/29/2022]
Abstract
Dynamin superfamily proteins are multidomain mechano-chemical GTPases which are implicated in nucleotide-dependent membrane remodeling events. A prominent feature of these proteins is their assembly- stimulated mechanism of GTP hydrolysis. The molecular basis for this reaction has been initially clarified for the dynamin-related guanylate binding protein 1 (GBP1) and involves the transient dimerization of the GTPase domains in a parallel head-to-head fashion. A catalytic arginine finger from the phosphate binding (P-) loop is repositioned toward the nucleotide of the same molecule to stabilize the transition state of GTP hydrolysis. Dynamin uses a related dimerization-dependent mechanism, but instead of the catalytic arginine, a monovalent cation is involved in catalysis. Still another variation of the GTP hydrolysis mechanism has been revealed for the dynamin-like Irga6 which bears a glycine at the corresponding position in the P-loop. Here, we highlight conserved and divergent features of GTP hydrolysis in dynamin superfamily proteins and show how nucleotide binding and hydrolysis are converted into mechano-chemical movements. We also describe models how the energy of GTP hydrolysis can be harnessed for diverse membrane remodeling events, such as membrane fission or fusion. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 580-593, 2016.
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Affiliation(s)
- Oliver Daumke
- Kristallographie, Max-Delbrück Centrum Für Molekulare Medizin, Robert-Rössle-Straße 10, Berlin, 13125, Germany
- Institut Für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195, Germany
| | - Gerrit J K Praefcke
- Abteilung Hämatologie/Transfusionsmedizin, Paul-Ehrlich-Institut, Paul-Ehrlich-Straße 51-59, Langen, 63225, Germany
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28
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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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29
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Hu JL, Hua YJ, Chen Y, Yu B, Gao S. Structural analysis of tumor-related single amino acid mutations in human MxA protein. CHINESE JOURNAL OF CANCER 2015; 34:583-93. [PMID: 26411585 PMCID: PMC4593380 DOI: 10.1186/s40880-015-0055-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 09/13/2015] [Indexed: 12/21/2022]
Abstract
Background Human myxovirus resistant protein A (MxA), encoded by the myxovirus resistance 1 (Mx1) gene, is an interferon (IFN)-triggered dynamin-like multi-domain GTPase involved in innate immune responses against viral infections. Recent studies suggest that MxA is associated with several human cancers and may be a tumor suppressor and a promising biomarker for IFN therapy. Mx1 gene mutations in the coding region for MxA have been discovered in many types of cancer, suggesting potential biological associations between mutations in MxA protein and corresponding cancers. In this study, we performed a systematic analysis based on the crystal structures of MxA and elucidated how these mutations specifically affect the structure and therefore the function of MxA protein. Methods Cancer-associated Mx1 mutations were collected and screened from the COSMIC database. Twenty-two unique mutations that cause single amino acid alterations in the MxA protein were chosen for the analysis. Amino acid sequence alignment was performed using Clustal W to check the conservation level of mutation sites in Mx proteins and dynamins. Structural analysis of the mutants was carried out with Coot. Structural models of selected mutants were generated by the SWISS-MODEL server for comparison with the corresponding non-mutated structures. All structural figures were generated using PyMOL. Results We analyzed the conservation level of the single-point mutation sites and mapped them on different domains of MxA. Through individual structural analysis, we found that some mutations severely affect the stability and function of MxA either by disrupting the intra-/inter-molecular interactions supported by the original residues or by incurring unfavorable configuration alterations, whereas other mutations lead to gentle or no interference to the protein stability and function because of positions or polarity features. The potential clinical value of the mutations that lead to drastic influence on MxA protein is also assessed. Conclusions Among all of the reported tumor-associated single-point mutations, seven of them notably affect the structure and function of MxA and therefore deserve more attention with respect to potential clinical applications. Our research provides an example for systematic analysis and consequence evaluation of single-point mutations on a given cancer-related protein.
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Affiliation(s)
- Jia-Li Hu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong, 510060, P.R. China.
| | - Yi-Jun Hua
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong, 510060, P.R. China.
| | - Yang Chen
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong, 510060, P.R. China.
| | - Bing Yu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong, 510060, P.R. China.
| | - Song Gao
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, Guangdong, 510060, P.R. China.
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30
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Dick A, Graf L, Olal D, von der Malsburg A, Gao S, Kochs G, Daumke O. Role of nucleotide binding and GTPase domain dimerization in dynamin-like myxovirus resistance protein A for GTPase activation and antiviral activity. J Biol Chem 2015; 290:12779-92. [PMID: 25829498 DOI: 10.1074/jbc.m115.650325] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Indexed: 12/28/2022] Open
Abstract
Myxovirus resistance (Mx) GTPases are induced by interferon and inhibit multiple viruses, including influenza and human immunodeficiency viruses. They have the characteristic domain architecture of dynamin-related proteins with an N-terminal GTPase (G) domain, a bundle signaling element, and a C-terminal stalk responsible for self-assembly and effector functions. Human MxA (also called MX1) is expressed in the cytoplasm and is partly associated with membranes of the smooth endoplasmic reticulum. It shows a protein concentration-dependent increase in GTPase activity, indicating regulation of GTP hydrolysis via G domain dimerization. Here, we characterized a panel of G domain mutants in MxA to clarify the role of GTP binding and the importance of the G domain interface for the catalytic and antiviral function of MxA. Residues in the catalytic center of MxA and the nucleotide itself were essential for G domain dimerization and catalytic activation. In pulldown experiments, MxA recognized Thogoto virus nucleocapsid proteins independently of nucleotide binding. However, both nucleotide binding and hydrolysis were required for the antiviral activity against Thogoto, influenza, and La Crosse viruses. We further demonstrate that GTP binding facilitates formation of stable MxA assemblies associated with endoplasmic reticulum membranes, whereas nucleotide hydrolysis promotes dynamic redistribution of MxA from cellular membranes to viral targets. Our study highlights the role of nucleotide binding and hydrolysis for the intracellular dynamics of MxA during its antiviral action.
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Affiliation(s)
- Alexej Dick
- From the Max-Delbrück Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany, the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany
| | - Laura Graf
- the Institute of Virology, University Medical Center, Hermann-Herder-Strasse 11, 79104 Freiburg, Germany, the Spemann Graduate School of Biology and Medicine, University of Freiburg, Albertstrasse 19a, 79104 Freiburg, Germany, and
| | - Daniel Olal
- From the Max-Delbrück Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Alexander von der Malsburg
- the Institute of Virology, University Medical Center, Hermann-Herder-Strasse 11, 79104 Freiburg, Germany
| | - Song Gao
- the Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, and Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China
| | - Georg Kochs
- the Institute of Virology, University Medical Center, Hermann-Herder-Strasse 11, 79104 Freiburg, Germany, the Spemann Graduate School of Biology and Medicine, University of Freiburg, Albertstrasse 19a, 79104 Freiburg, Germany, and
| | - Oliver Daumke
- From the Max-Delbrück Centrum für Molekulare Medizin, Robert-Rössle-Strasse 10, 13125 Berlin, Germany, the Institute of Chemistry and Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany,
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31
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Rujiviphat J, Wong MK, Won A, Shih YL, Yip CM, McQuibban GA. Mitochondrial Genome Maintenance 1 (Mgm1) Protein Alters Membrane Topology and Promotes Local Membrane Bending. J Mol Biol 2015; 427:2599-609. [PMID: 25784211 DOI: 10.1016/j.jmb.2015.03.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 11/25/2022]
Abstract
Large GTPases of the dynamin superfamily promote membrane fusion and division, processes that are crucial for intracellular trafficking and organellar dynamics. To promote membrane scission, dynamin proteins polymerize, wrap around, and constrict the membrane; however, the mechanism underlying their role in membrane fusion remains unclear. We previously reported that the mitochondrial dynamin-related protein mitochondrial genome maintenance 1 (Mgm1) mediates fusion by first tethering opposing membranes and then undergoing a nucleotide-dependent structural transition. However, it is still unclear how Mgm1 directly affects the membrane to drive fusion of tethered membranes. Here, we show that Mgm1 association with the membrane alters the topography of the membrane, promoting local membrane bending. We also demonstrate that Mgm1 creates membrane ruffles resulting in the formation of tubular structures on both supported lipid bilayers and liposomes. These data suggest that Mgm1 membrane interactions impose a mechanical force on the membrane to overcome the hydrophilic repulsion of the phospholipid head groups and initiate the fusion reaction. The work reported here provides new insights into a possible mechanism of Mgm1-driven mitochondrial membrane fusion and sheds light into how members of the dynamin superfamily function as fusion molecules.
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Affiliation(s)
- Jarungjit Rujiviphat
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Michael K Wong
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9
| | - Amy Won
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9
| | - Yu-Ling Shih
- Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Christopher M Yip
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada M5S 3G9; Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3E5
| | - G Angus McQuibban
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
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Haller O, Staeheli P, Schwemmle M, Kochs G. Mx GTPases: dynamin-like antiviral machines of innate immunity. Trends Microbiol 2015; 23:154-63. [PMID: 25572883 DOI: 10.1016/j.tim.2014.12.003] [Citation(s) in RCA: 323] [Impact Index Per Article: 35.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 11/28/2014] [Accepted: 12/03/2014] [Indexed: 01/09/2023]
Abstract
The Mx dynamin-like GTPases are key antiviral effector proteins of the type I and type III interferon (IFN) systems. They inhibit several different viruses by blocking early steps of the viral replication cycle. We focus on new structural and functional insights and discuss recent data revealing that human MxA (MX1) provides a safeguard against introduction of avian influenza A viruses (FLUAV) into the human population. The related human MxB (MX2) serves as restriction factor for HIV-1 and other primate lentiviruses.
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Affiliation(s)
- Otto Haller
- Institute of Virology, University Medical Center Freiburg, Freiburg, Germany.
| | - Peter Staeheli
- Institute of Virology, University Medical Center Freiburg, Freiburg, Germany.
| | - Martin Schwemmle
- Institute of Virology, University Medical Center Freiburg, Freiburg, Germany
| | - Georg Kochs
- Institute of Virology, University Medical Center Freiburg, Freiburg, Germany
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Abstract
Influenza viruses pose a substantial threat to human and animal health worldwide. Recent studies in mouse models have revealed an indispensable role for the innate immune system in defense against influenza virus. Recognition of the virus by innate immune receptors in a multitude of cell types activates intricate signaling networks, functioning to restrict viral replication. Downstream effector mechanisms include activation of innate immune cells and, induction and regulation of adaptive immunity. However, uncontrolled innate responses are associated with exaggerated disease, especially in pandemic influenza virus infection. Despite advances in the understanding of innate response to influenza in the mouse model, there is a large knowledge gap in humans, particularly in immunocompromised groups such as infants and the elderly. We propose here, the need for further studies in humans to decipher the role of innate immunity to influenza virus, particularly at the site of infection. These studies will complement the existing work in mice and facilitate the quest to design improved vaccines and therapeutic strategies against influenza.
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Affiliation(s)
- Michael B. A. Oldstone
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California USA
| | - Richard W. Compans
- IDepartment of Microbiology and Immunology, Emory University, Atlanta, Georgia USA
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Matreyek KA, Wang W, Serrao E, Singh PK, Levin HL, Engelman A. Host and viral determinants for MxB restriction of HIV-1 infection. Retrovirology 2014; 11:90. [PMID: 25348155 PMCID: PMC4213484 DOI: 10.1186/s12977-014-0090-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 10/08/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Interferon-induced cellular proteins play important roles in the host response against viral infection. The Mx family of dynamin-like GTPases, which include MxA and MxB, target a wide variety of viruses. Despite considerable evidence demonstrating the breadth of antiviral activity of MxA, human MxB was only recently discovered to specifically inhibit lentiviruses. Here we assess both host and viral determinants that underlie MxB restriction of HIV-1 infection. RESULTS Heterologous expression of MxB in human osteosarcoma cells potently inhibited HIV-1 infection (~12-fold), yet had little to no effect on divergent retroviruses. The anti-HIV effect manifested as a partial block in the formation of 2-long terminal repeat circle DNA and hence nuclear import, and we accordingly found evidence for an additional post-nuclear entry block. A large number of previously characterized capsid mutations, as well as mutations that abrogated integrase activity, counteracted MxB restriction. MxB expression suppressed integration into gene-enriched regions of chromosomes, similar to affects observed previously when cells were depleted for nuclear transport factors such as transportin 3. MxB activity did not require predicted GTPase active site residues or a series of unstructured loops within the stalk domain that confer functional oligomerization to related dynamin family proteins. In contrast, we observed an N-terminal stretch of residues in MxB to harbor key determinants. Protein localization conferred by a nuclear localization signal (NLS) within the N-terminal 25 residues, which was critical, was fully rescuable by a heterologous NLS. Consistent with this observation, a heterologous nuclear export sequence (NES) abolished full-length MxB activity. We additionally mapped sub-regions within amino acids 26-90 that contribute to MxB activity, finding sequences present within residues 27-50 particularly important. CONCLUSIONS MxB inhibits HIV-1 by interfering with minimally two steps of infection, nuclear entry and post-nuclear trafficking and/or integration, without destabilizing the inherent catalytic activity of viral preintegration complexes. Putative MxB GTPase active site residues and stalk domain Loop 4 -- both previously shown to be necessary for MxA function -- were dispensable for MxB antiviral activity. Instead, we highlight subcellular localization and a yet-determined function(s) present in the unique MxB N-terminal region to be required for HIV-1 restriction.
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Affiliation(s)
- Kenneth A Matreyek
- Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute and Department of Medicine, Harvard Medical School, Boston, MA, 02215, USA. .,Present address: Department of Genome Sciences, University of Washington, Seattle, WA, 98195, USA.
| | - Weifeng Wang
- Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute and Department of Medicine, Harvard Medical School, Boston, MA, 02215, USA.
| | - Erik Serrao
- Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute and Department of Medicine, Harvard Medical School, Boston, MA, 02215, USA.
| | - Parmit Kumar Singh
- Section on Eukaryotic Transposable Elements, Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Henry L Levin
- Section on Eukaryotic Transposable Elements, Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Alan Engelman
- Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute and Department of Medicine, Harvard Medical School, Boston, MA, 02215, USA.
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Bustillo-Zabalbeitia I, Montessuit S, Raemy E, Basañez G, Terrones O, Martinou JC. Specific interaction with cardiolipin triggers functional activation of Dynamin-Related Protein 1. PLoS One 2014; 9:e102738. [PMID: 25036098 PMCID: PMC4103857 DOI: 10.1371/journal.pone.0102738] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 06/23/2014] [Indexed: 11/18/2022] Open
Abstract
Dynamin-Related Protein 1 (Drp1), a large GTPase of the dynamin superfamily, is required for mitochondrial fission in healthy and apoptotic cells. Drp1 activation is a complex process that involves translocation from the cytosol to the mitochondrial outer membrane (MOM) and assembly into rings/spirals at the MOM, leading to membrane constriction/division. Similar to dynamins, Drp1 contains GTPase (G), bundle signaling element (BSE) and stalk domains. However, instead of the lipid-interacting Pleckstrin Homology (PH) domain present in the dynamins, Drp1 contains the so-called B insert or variable domain that has been suggested to play an important role in Drp1 regulation. Different proteins have been implicated in Drp1 recruitment to the MOM, although how MOM-localized Drp1 acquires its fully functional status remains poorly understood. We found that Drp1 can interact with pure lipid bilayers enriched in the mitochondrion-specific phospholipid cardiolipin (CL). Building on our previous study, we now explore the specificity and functional consequences of this interaction. We show that a four lysine module located within the B insert of Drp1 interacts preferentially with CL over other anionic lipids. This interaction dramatically enhances Drp1 oligomerization and assembly-stimulated GTP hydrolysis. Our results add significantly to a growing body of evidence indicating that CL is an important regulator of many essential mitochondrial functions.
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Affiliation(s)
- Itsasne Bustillo-Zabalbeitia
- Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Sylvie Montessuit
- Department of Cell Biology, University of Geneva, Geneva, Switzerland
| | - Etienne Raemy
- Department of Cell Biology, University of Geneva, Geneva, Switzerland
| | - Gorka Basañez
- Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Oihana Terrones
- Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
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Hoff F, Greb C, Hollmann C, Hönig E, Jacob R. The Large GTPase Mx1 Is Involved in Apical Transport in MDCK Cells. Traffic 2014; 15:983-96. [DOI: 10.1111/tra.12186] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 12/14/2022]
Affiliation(s)
- Florian Hoff
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Robert-Koch-Str. 6 35037 Marburg Germany
| | - Christoph Greb
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Robert-Koch-Str. 6 35037 Marburg Germany
| | - Christina Hollmann
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Robert-Koch-Str. 6 35037 Marburg Germany
| | - Ellena Hönig
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Robert-Koch-Str. 6 35037 Marburg Germany
| | - Ralf Jacob
- Department of Cell Biology and Cell Pathology; Philipps University of Marburg; Robert-Koch-Str. 6 35037 Marburg Germany
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Gu C, Chang J, Shchedrina VA, Pham VA, Hartwig JH, Suphamungmee W, Lehman W, Hyman BT, Bacskai BJ, Sever S. Regulation of dynamin oligomerization in cells: the role of dynamin-actin interactions and its GTPase activity. Traffic 2014; 15:819-38. [PMID: 24891099 DOI: 10.1111/tra.12178] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 05/26/2014] [Accepted: 05/28/2014] [Indexed: 01/22/2023]
Abstract
Dynamin is a 96-kDa protein that has multiple oligomerization states that influence its GTPase activity. A number of different dynamin effectors, including lipids, actin filaments, and SH3-domain-containing proteins, have been implicated in the regulation of dynamin oligomerization, though their roles in influencing dynamin oligomerization have been studied predominantly in vitro using recombinant proteins. Here, we identify higher order dynamin oligomers such as rings and helices in vitro and in live cells using fluorescence lifetime imaging microscopy (FLIM). FLIM detected GTP- and actin-dependent dynamin oligomerization at distinct cellular sites, including the cell membrane and transition zones where cortical actin transitions into stress fibers. Our study identifies a major role for direct dynamin-actin interactions and dynamin's GTPase activity in the regulation of dynamin oligomerization in cells.
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Affiliation(s)
- Changkyu Gu
- Division of Nephrology, Massachusetts General Hospital, Charlestown, MA, 02129, USA
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Transfer of the amino-terminal nuclear envelope targeting domain of human MX2 converts MX1 into an HIV-1 resistance factor. J Virol 2014; 88:9017-26. [PMID: 24899177 DOI: 10.1128/jvi.01269-14] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED The myxovirus resistance 2 (MX2) protein of humans has been identified recently as an interferon (IFN)-inducible inhibitor of human immunodeficiency virus type 1 (HIV-1) that acts at a late postentry step of infection to prevent the nuclear accumulation of viral cDNA (C. Goujon et al., Nature 502:559-562, 2013, http://dx.doi.org/10.1038/nature12542; M. Kane et al., Nature 502:563-566, 2013, http://dx.doi.org/10.1038/nature12653; Z. Liu et al., Cell Host Microbe 14:398-410, 2013, http://dx.doi.org/10.1016/j.chom.2013.08.015). In contrast, the closely related human MX1 protein, which suppresses infection by a range of RNA and DNA viruses (such as influenza A virus [FluAV]), is ineffective against HIV-1. Using a panel of engineered chimeric MX1/2 proteins, we demonstrate that the amino-terminal 91-amino-acid domain of MX2 confers full anti-HIV-1 function when transferred to the amino terminus of MX1, and that this fusion protein retains full anti-FluAV activity. Confocal microscopy experiments further show that this MX1/2 fusion, similar to MX2 but not MX1, can localize to the nuclear envelope (NE), linking HIV-1 inhibition with MX accumulation at the NE. MX proteins are dynamin-like GTPases, and while MX1 antiviral function requires GTPase activity, neither MX2 nor MX1/2 chimeras require this attribute to inhibit HIV-1. This key discrepancy between the characteristics of MX1- and MX2-mediated viral resistance, together with previous observations showing that the L4 loop of the stalk domain of MX1 is a critical determinant of viral substrate specificity, presumably reflect fundamental differences in the mechanisms of antiviral suppression. Accordingly, we propose that further comparative studies of MX proteins will help illuminate the molecular basis and subcellular localization requirements for implementing the noted diversity of virus inhibition by MX proteins. IMPORTANCE Interferon (IFN) elicits an antiviral state in cells through the induction of hundreds of IFN-stimulated genes (ISGs). The human MX2 protein has been identified as a key effector in the suppression of HIV-1 infection by IFN. Here, we describe a molecular genetic approach, using a collection of chimeric MX proteins, to identify protein domains of MX2 that specify HIV-1 inhibition. The amino-terminal 91-amino-acid domain of human MX2 confers HIV-1 suppressor capabilities upon human and mouse MX proteins and also promotes protein accumulation at the nuclear envelope. Therefore, these studies correlate the cellular location of MX proteins with anti-HIV-1 function and help establish a framework for future mechanistic analyses of MX-mediated virus control.
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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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Shah C, Hegde BG, Morén B, Behrmann E, Mielke T, Moenke G, Spahn CMT, Lundmark R, Daumke O, Langen R. Structural insights into membrane interaction and caveolar targeting of dynamin-like EHD2. Structure 2014; 22:409-420. [PMID: 24508342 DOI: 10.1016/j.str.2013.12.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 12/16/2013] [Accepted: 12/21/2013] [Indexed: 01/17/2023]
Abstract
The dynamin-related Eps15-homology domain-containing protein 2 (EHD2) is a membrane-remodeling ATPase that regulates the dynamics of caveolae. Here, we established an electron paramagnetic resonance (EPR) approach to characterize structural features of membrane-bound EHD2. We show that residues at the tip of the helical domain can insert into the membrane and may create membrane curvature by a wedging mechanism. Using EPR and X-ray crystallography, we found that the N terminus is folded into a hydrophobic pocket of the GTPase domain in solution and can be released into the membrane. Cryoelectron microscopy demonstrated that the N terminus is not essential for oligomerization of EHD2 into a membrane-anchored scaffold. Instead, we found a function of the N terminus in regulating targeting and stable association of EHD2 to caveolae. Our data uncover an unexpected, membrane-induced regulatory switch in EHD2 and demonstrate the versatility of EPR to study structure and function of dynamin superfamily proteins.
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Affiliation(s)
- Claudio Shah
- Max-Delbrück-Center for Molecular Medicine, Crystallography, Robert-Rössle-Straße 10, 13092 Berlin, Germany.,Institute of Chemistry and Biochemistry, Free University Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Balachandra G Hegde
- Post Graduate Department of Physics, Rani Channamma University, Vidyasangama, Belagavi-591156, India
| | - Björn Morén
- Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
| | - Elmar Behrmann
- Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany
| | - Thorsten Mielke
- Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany.,UltraStrukturNetzwerk, Max-Planck-Institute for Molecular Genetics, Ihnestraße 73, 14195 Berlin
| | - Gregor Moenke
- Max-Delbrück-Center for Molecular Medicine, Crystallography, Robert-Rössle-Straße 10, 13092 Berlin, Germany
| | - Christian M T Spahn
- Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany
| | - Richard Lundmark
- Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
| | - Oliver Daumke
- Max-Delbrück-Center for Molecular Medicine, Crystallography, Robert-Rössle-Straße 10, 13092 Berlin, Germany.,Institute of Medical Physics and Biophysics, Charité, Charitéplatz 1, 10117 Berlin, Germany
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, 1501 San Pablo Street, Los Angeles, CA 90033, USA
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Patzina C, Haller O, Kochs G. Structural requirements for the antiviral activity of the human MxA protein against Thogoto and influenza A virus. J Biol Chem 2014; 289:6020-7. [PMID: 24448803 DOI: 10.1074/jbc.m113.543892] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The interferon-induced dynamin-like MxA protein has broad antiviral activity against many viruses, including orthomyxoviruses such as influenza A and Thogoto virus and bunyaviruses such as La Crosse virus. MxA consists of an N-terminal globular GTPase domain, a connecting bundle signaling element, and the C-terminal stalk that mediates oligomerization and antiviral specificity. We previously reported that the disordered loop L4 that protrudes from the compact stalk is a key determinant of antiviral specificity against influenza A and Thogoto virus. However, the role of individual amino acids for viral target recognition remained largely undefined. By mutational analyses, we identified two regions in the C-terminal part of L4 that contribute to an antiviral interface. Mutations in the proximal motif, at positions 561 and 562, abolished antiviral activity against orthomyxoviruses but not bunyaviruses. In contrast, mutations in the distal motif, around position 577, abolished antiviral activity against both viruses. These results indicate that at least two structural elements in L4 are responsible for antiviral activity and that the proximal motif determines specificity for orthomyxoviruses, whereas the distal sequence serves a conserved structural function.
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Affiliation(s)
- Corinna Patzina
- From the Institute of Virology, University of Freiburg, 79008 Freiburg, Germany
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Ciencewicki JM, Wang X, Marzec J, Serra ME, Bell DA, Polack FP, Kleeberger SR. A genetic model of differential susceptibility to human respiratory syncytial virus (RSV) infection. FASEB J 2014; 28:1947-56. [PMID: 24421397 DOI: 10.1096/fj.13-239855] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Respiratory syncytial virus (RSV) is the primary cause of lower respiratory tract infection during childhood and causes severe symptoms in some patients, which may cause hospitalization and death. Mechanisms for differential responses to RSV are unknown. Our objective was to develop an in vitro model of RSV infection to evaluate interindividual variation in response to RSV and identify susceptibility genes. Populations of human-derived HapMap lymphoblastoid cell lines (LCLs) were infected with RSV. Compared with controls, RSV-G mRNA expression varied from ~1- to 400-fold between LCLs. Basal expression of a number of gene transcripts, including myxovirus (influenza virus) resistance 1 (MX1), significantly correlated with RSV-G expression in HapMap LCLs. Individuals in a case-control population of RSV-infected children who were homozygous (n=94) or heterozygous (n=172) for the predicted deleterious A allele in a missense G/A SNP in MX1 had significantly greater risk for developing severe RSV disease relative to those with the major allele (n=108) (χ(2)=5.305, P=0.021; OR: 1.750, 95% CI: 1.110, 2.758, P=0.021). We conclude that genetically diverse human LCLs enable identification of susceptibility genes (e.g., MX1) for RSV disease severity in children, providing insight for disease risk.
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Affiliation(s)
- Jonathan M Ciencewicki
- 1Laboratory of Respiratory Biology National Institute of Environmental Health Sciences, 111 T. W. Alexander Dr., Bldg. 101, MD D-201, Research Triangle Park, NC 27709, USA.
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Issman L, Brenner B, Talmon Y, Aharon A. Cryogenic transmission electron microscopy nanostructural study of shed microparticles. PLoS One 2013; 8:e83680. [PMID: 24386253 PMCID: PMC3873325 DOI: 10.1371/journal.pone.0083680] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 11/06/2013] [Indexed: 11/21/2022] Open
Abstract
Microparticles (MPs) are sub-micron membrane vesicles (100–1000 nm) shed from normal and pathologic cells due to stimulation or apoptosis. MPs can be found in the peripheral blood circulation of healthy individuals, whereas elevated concentrations are found in pregnancy and in a variety of diseases. Also, MPs participate in physiological processes, e.g., coagulation, inflammation, and angiogenesis. Since their clinical properties are important, we have developed a new methodology based on nano-imaging that provides significant new data on MPs nanostructure, their composition and function. We are among the first to characterize by direct-imaging cryogenic transmitting electron microscopy (cryo-TEM) the near-to-native nanostructure of MP systems isolated from different cell types and stimulation procedures. We found that there are no major differences between the MP systems we have studied, as most particles were spherical, with diameters from 200 to 400 nm. However, each MP population is very heterogeneous, showing diverse morphologies. We investigated by cryo-TEM the effects of standard techniques used to isolate and store MPs, and found that either high-g centrifugation of MPs for isolation purposes, or slow freezing to –80°C for storage introduce morphological artifacts, which can influence MP nanostructure, and thus affect the efficiency of these particles as future diagnostic tools.
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Affiliation(s)
- Liron Issman
- Department of Chemical Engineering and The Russell Berrie Nanotechnology Institute (RBNI), Technion-Israel Institute of Technology, Haifa, Israel
- * E-mail: (LI); (YT)
| | - Benjamin Brenner
- The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
- Thrombosis and Hemostasis Unit, Department of Hematology, Rambam Health Care Campus, Haifa, Israel
| | - Yeshayahu Talmon
- Department of Chemical Engineering and The Russell Berrie Nanotechnology Institute (RBNI), Technion-Israel Institute of Technology, Haifa, Israel
- * E-mail: (LI); (YT)
| | - Anat Aharon
- The Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
- Thrombosis and Hemostasis Unit, Department of Hematology, Rambam Health Care Campus, Haifa, Israel
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Wenger J, Klinglmayr E, Fröhlich C, Eibl C, Gimeno A, Hessenberger M, Puehringer S, Daumke O, Goettig P. Functional mapping of human dynamin-1-like GTPase domain based on x-ray structure analyses. PLoS One 2013; 8:e71835. [PMID: 23977156 PMCID: PMC3747075 DOI: 10.1371/journal.pone.0071835] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 07/03/2013] [Indexed: 11/18/2022] Open
Abstract
Human dynamin-1-like protein (DNM1L) is a GTP-driven molecular machine that segregates mitochondria and peroxisomes. To obtain insights into its catalytic mechanism, we determined crystal structures of a construct comprising the GTPase domain and the bundle signaling element (BSE) in the nucleotide-free and GTP-analogue-bound states. The GTPase domain of DNM1L is structurally related to that of dynamin and binds the nucleotide 5′-Guanylyl-imidodiphosphate (GMP-PNP) via five highly conserved motifs, whereas the BSE folds into a pocket at the opposite side. Based on these structures, the GTPase center was systematically mapped by alanine mutagenesis and kinetic measurements. Thus, residues essential for the GTPase reaction were characterized, among them Lys38, Ser39 and Ser40 in the phosphate binding loop, Thr59 from switch I, Asp146 and Gly149 from switch II, Lys216 and Asp218 in the G4 element, as well as Asn246 in the G5 element. Also, mutated Glu81 and Glu82 in the unique 16-residue insertion of DNM1L influence the activity significantly. Mutations of Gln34, Ser35, and Asp190 in the predicted assembly interface interfered with dimerization of the GTPase domain induced by a transition state analogue and led to a loss of the lipid-stimulated GTPase activity. Our data point to related catalytic mechanisms of DNM1L and dynamin involving dimerization of their GTPase domains.
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Affiliation(s)
- Julia Wenger
- Department of Molecular Biology, University of Salzburg, Salzburg, Austria
| | - Eva Klinglmayr
- Department of Molecular Biology, University of Salzburg, Salzburg, Austria
| | - Chris Fröhlich
- Crystallography, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Clarissa Eibl
- Department of Molecular Biology, University of Salzburg, Salzburg, Austria
| | - Ana Gimeno
- Department of Molecular Biology, University of Salzburg, Salzburg, Austria
| | | | - Sandra Puehringer
- Macromolecular Crystallography, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
- Department of Biology and Chemistry, Freie Universität Berlin, Berlin, Germany
| | - Oliver Daumke
- Crystallography, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
| | - Peter Goettig
- Department of Molecular Biology, University of Salzburg, Salzburg, Austria
- * E-mail:
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Mitchell PS, Emerman M, Malik HS. An evolutionary perspective on the broad antiviral specificity of MxA. Curr Opin Microbiol 2013; 16:493-9. [PMID: 23725670 PMCID: PMC3763691 DOI: 10.1016/j.mib.2013.04.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/18/2013] [Accepted: 04/22/2013] [Indexed: 11/28/2022]
Abstract
Germ line encoded antiviral defenses in vertebrate cells tend to be either broadly acting factors that exploit general features of viral replication or effectors with strong pathogen preference by virtue of specific recognition of viral proteins. The Mx GTPases, however, are atypical since they have broad antiviral activity against a wide range of RNA and DNA viruses despite specifically targeting different proteins across virus families. This review presents recent advances in understanding the biochemical properties and evolution of the primate ortholog MxA, and discusses how this information begins to provide molecular insights into the mechanisms behind the intriguing conundrum of how MxA is able to engage a diversity of viral proteins yet elicit antiviral breadth.
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Affiliation(s)
- Patrick S Mitchell
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98185, USA
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Interferon-beta therapy in multiple sclerosis: the short-term and long-term effects on the patients' individual gene expression in peripheral blood. Mol Neurobiol 2013; 48:737-56. [PMID: 23636981 DOI: 10.1007/s12035-013-8463-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 04/16/2013] [Indexed: 01/17/2023]
Abstract
Therapy with interferon-beta (IFN-beta) is a mainstay in the management of relapsing-remitting multiple sclerosis (MS), with proven long-term effectiveness and safety. Much has been learned about the molecular mechanisms of action of IFN-beta in the past years. Previous studies described more than a hundred genes to be modulated in expression in blood cells in response to the therapy. However, for many of these genes, the precise temporal expression pattern and the therapeutic relevance are unclear. We used Affymetrix microarrays to investigate in more detail the gene expression changes in peripheral blood mononuclear cells from MS patients receiving subcutaneous IFN-beta-1a. The blood samples were obtained longitudinally at five different time points up to 2 years after the start of therapy, and the patients were clinically followed up for 5 years. We examined the functions of the genes that were upregulated or downregulated at the transcript level after short-term or long-term treatment. Moreover, we analyzed their mutual interactions and their regulation by transcription factors. Compared to pretreatment levels, 96 genes were identified as highly differentially expressed, many of them already after the first IFN-beta injection. The interactions between these genes form a large network with multiple feedback loops, indicating the complex crosstalk between innate and adaptive immune responses during therapy. We discuss the genes and biological processes that might be important to reduce disease activity by attenuating the proliferation of autoreactive immune cells and their migration into the central nervous system. In summary, we present novel insights that extend the current knowledge on the early and late pharmacodynamic effects of IFN-beta therapy and describe gene expression differences between the individual patients that reflect clinical heterogeneity.
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Fröhlich C, Grabiger S, Schwefel D, Faelber K, Rosenbaum E, Mears J, Rocks O, Daumke O. Structural insights into oligomerization and mitochondrial remodelling of dynamin 1-like protein. EMBO J 2013; 32:1280-92. [PMID: 23584531 DOI: 10.1038/emboj.2013.74] [Citation(s) in RCA: 219] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 03/13/2013] [Indexed: 01/09/2023] Open
Abstract
Dynamin 1-like protein (DNM1L) mediates fission of mitochondria and peroxisomes, and dysfunction of DNM1L has been implicated in several neurological disorders. To study the molecular basis of mitochondrial remodelling, we determined the crystal structure of DNM1L that is comprised of a G domain, a bundle signalling element and a stalk. DNM1L assembled via a central stalk interface, and mutations in this interface disrupted dimerization and interfered with membrane binding and mitochondrial targeting. Two sequence stretches at the tip of the stalk were shown to be required for ordered assembly of DNM1L on membranes and its function in mitochondrial fission. In the crystals, DNM1L dimers further assembled via a second, previously undescribed, stalk interface to form a linear filament. Mutations in this interface interfered with liposome tubulation and mitochondrial remodelling. Based on these results and electron microscopy reconstructions, we propose an oligomerization mode for DNM1L which differs from that of dynamin and might be adapted to the remodelling of mitochondria.
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Affiliation(s)
- Chris Fröhlich
- Crystallography, Max-Delbrück-Center for Molecular Medicine, Berlin, Germany
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48
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Mitchell PS, Patzina C, Emerman M, Haller O, Malik HS, Kochs G. Evolution-guided identification of antiviral specificity determinants in the broadly acting interferon-induced innate immunity factor MxA. Cell Host Microbe 2013; 12:598-604. [PMID: 23084925 PMCID: PMC3540999 DOI: 10.1016/j.chom.2012.09.005] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 06/27/2012] [Accepted: 09/18/2012] [Indexed: 02/02/2023]
Abstract
MxA is an interferon-induced dynamin-like GTPase with wide-ranging antiviral activity, which hinges upon detection of unique viral structures that differ across virus families. Despite elucidation of its structure, the basis of MxA antiviral specificity remains enigmatic. We used an evolution-guided approach to identify the loop L4 of MxA as a hotspot for recurrent positive selection in primates. Further, we show that single amino acid changes in L4 are necessary and sufficient to explain dramatic differences in species-specific antiviral activity of primate MxA proteins against the orthomyxoviruses Thogoto virus and influenza A virus. Taken together, our findings identify a genetic determinant of MxA target recognition and suggest a model by which MxA achieves antiviral breadth without compromising viral specificity.
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Affiliation(s)
- Patrick S. Mitchell
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA 98185, USA
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Corinna Patzina
- Department of Virology, Institute for Medical Microbiology and Hygiene, University of Freiburg, 79104 Freiburg, Germany
- International Max Planck Research School for Molecular and Cellular Biology, Freiburg, Germany
| | - Michael Emerman
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Otto Haller
- Department of Virology, Institute for Medical Microbiology and Hygiene, University of Freiburg, 79104 Freiburg, Germany
| | - Harmit S. Malik
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
- Correspondence: . Phone: (206) 667-4512. Fax: (206) 667-6522. . Phone: 49-761-2036623. Fax: 49-761-2036562
| | - Georg Kochs
- Department of Virology, Institute for Medical Microbiology and Hygiene, University of Freiburg, 79104 Freiburg, Germany
- Correspondence: . Phone: (206) 667-4512. Fax: (206) 667-6522. . Phone: 49-761-2036623. Fax: 49-761-2036562
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Faelber K, Gao S, Held M, Posor Y, Haucke V, Noé F, Daumke O. Oligomerization of dynamin superfamily proteins in health and disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 117:411-43. [PMID: 23663977 DOI: 10.1016/b978-0-12-386931-9.00015-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Proteins of the dynamin superfamily are mechanochemical GTPases, which mediate nucleotide-dependent membrane remodeling events. The founding member dynamin is recruited to the neck of clathrin-coated endocytic vesicles where it oligomerizes into helical filaments. Nucleotide-hydrolysis-induced conformational changes in the oligomer catalyze scission of the vesicle neck. Here, we review recent insights into structure, function, and oligomerization of dynamin superfamily proteins and their roles in human diseases. We describe in detail the molecular mechanisms how dynamin oligomerizes at membranes and introduce a model how oligomerization is linked to membrane fission. Finally, we discuss molecular mechanisms how mutations in dynamin could lead to the congenital diseases, Centronuclear Myopathy and Charcot-Marie Tooth disease.
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Affiliation(s)
- Katja Faelber
- Max-Delbrück-Centrum for Molecular Medicine, Crystallography, Berlin, Germany
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