Interferon-Inducible Protein Mx1 Inhibits Influenza Virus by Interfering with Functional Viral Ribonucleoprotein Complex Assembly

Verhelst, Judith; Parthoens, Eef; Schepens, Bert; Fiers, Walter; Saelens, Xavier

doi:10.1128/jvi.01682-12

Cited by 188 publications

(159 citation statements)

References 56 publications

(48 reference statements)

Supporting

Mentioning

154

Contrasting

Order By: Relevance

“…Mx was recently shown to interfere with the interaction of PB2 and NP (50,51). Data from our lab did not confirm direct interaction of MxA with either NP or PB2, and we found no evidence for consistent colocalization of Mx with NP in H7N9-infected cells, as determined by confocal laser scanning microscopy (our unpublished observations).…”

Section: Discussioncontrasting

confidence: 41%

The Nucleoprotein of Newly Emerged H7N9 Influenza A Virus Harbors a Unique Motif Conferring Resistance to Antiviral Human MxA

Riegger

Hai

Dornfeld

et al. 2015

J Virol

View full text Add to dashboard Cite

Interferon-induced Mx proteins show strong antiviral activity against influenza A viruses (IAVs).We recently demonstrated that the viral nucleoprotein (NP) determines resistance of seasonal and pandemic human influenza viruses to Mx, while avian isolates retain Mx sensitivity. We identified a surface-exposed cluster of amino acids in NP of pandemic A/BM/1/1918 (H1N1), comprising isoleucine-100, proline-283, and tyrosine-313, that is essential for reduced Mx sensitivity in cell culture and in vivo. This cluster has been maintained in all descendant seasonal strains, including A/PR/8/34 (PR/8). Accordingly, two substitutions in the NP of PR/8 [PR/8(mut)] to the Mx-sensitive amino acids (P283L and Y313F) led to attenuation in Mx1-positive mice. Serial lung passages of PR/8(mut) in Mx1 mice resulted in a single exchange of tyrosine to asparagine at position 52 in NP (in close proximity to the amino acid cluster at positions 100, 283, and 313), which partially compensates loss of Mx resistance in PR/8(mut). Intriguingly, the NP of the newly emerged avian-origin H7N9 virus also contains an asparagine at position 52 and shows reduced Mx sensitivity. N52Y substitution in NP results in increased sensitivity of the H7N9 virus to human Mx, indicating that this residue is a determinant of Mx resistance in mammals. Our data strengthen the hypothesis that the human Mx protein represents a potent barrier against zoonotic transmission of avian influenza viruses. However, the H7N9 viruses overcome this restriction by harboring an NP that is less sensitive to Mx-mediated host defense. This might contribute to zoonotic transmission of H7N9 and to the severe to fatal outcome of H7N9 infections in humans. IMPORTANCEThe natural host of influenza A viruses (IAVs) are aquatic birds. Occasionally, these viruses cross the species barrier, as in early 2013 when an avian H7N9 virus infected humans in China. Since then, multiple transmissions of H7N9 viruses to humans have occurred, leaving experts puzzled about molecular causes for such efficient crossing of the species barrier compared to other avian influenza viruses. Mx proteins are known restriction factors preventing influenza virus replication. Unfortunately, some viruses (e.g., human IAV) have developed some resistance, which is associated with specific amino acids in their nucleoproteins, the target of Mx function. Here, we demonstrate that the novel H7N9 bird IAV already carries a nucleoprotein that overcomes the inhibition of viral replication by human MxA. This is the first example of an avian IAV that is naturally less sensitive to Mxmediated inhibition and might explain why H7N9 viruses transmitted efficiently to humans. In 2013 a new H7N9 variant of avian influenza A virus (IAV) was transmitted from birds to humans, causing more than 300 cases of severe disease with often fatal outcomes (1, 2). The unusual, relatively high number of human infections caused by this virus correlated with several adaptations to the mammalian host, including changes in the hemagglutinin ...

show abstract

Section: Discussioncontrasting

confidence: 41%

The Nucleoprotein of Newly Emerged H7N9 Influenza A Virus Harbors a Unique Motif Conferring Resistance to Antiviral Human MxA

Riegger

Hai

Dornfeld

et al. 2015

J Virol

View full text Add to dashboard Cite

show abstract

“…We recently demonstrated that Mx1 interacts with both the NP and PB2 proteins and disturbs their interaction by a mechanism that depends on GTP binding and/or GTPase activity. Surprisingly, the interactions of Mx1 with NP and PB2 do not depend on GTPase activity, which is essential for its antiviral activity (94). In the future, it will be interesting to determine if a higher Mx resistance of specific NP variants correlates with a weaker binding to Mx1 (and MxA) to confirm the crucial role of influenza virus NP in Mx1 sensitivity.…”

Section: Antiviral Activity Against Orthomyxoviridaementioning

confidence: 99%

Mx Proteins: Antiviral Gatekeepers That Restrain the Uninvited

Verhelst

Hulpiau

Saelens

2013

Microbiol Mol Biol Rev

Self Cite

241

158

View full text Add to dashboard Cite

SUMMARY 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.

show abstract

“…Overexpression of NP Interferes with the Antiviral Function of Human MxA-We and others have shown previously that overexpression of PB2 and NP interfered with the antiviral function of mouse Mx1 (15)(16)(17). Therefore, we next wanted to test whether the activity of MxA could be overcome by increased expression of NP and/or PB2.…”

Section: Mxa Inhibits Iav Replication At Amentioning

confidence: 99%

“…Previous studies have demonstrated that GTP binding is required for its efficient antiviral activity against vesicular stomatitis virus and IAV (6,14). In the case of IAV, several previous studies have demonstrated that ectopic expression of the nucleocapsid protein (NP) or the polymerase subunit 2 (PB2) of the virus partially abrogated the antiviral activity of mouse Mx1 (15)(16)(17). Moreover, human IAV strains are partially resistant to the activity of MxA, whereas non-adapted avian IAV strains such as H5N1 are highly sensitive to MxA.…”

mentioning

confidence: 99%

Oligomerization and GTP-binding Requirements of MxA for Viral Target Recognition and Antiviral Activity against Influenza A Virus

Nigg

Pavlovic

2015

Journal of Biological Chemistry

View full text Add to dashboard Cite

The IFN-induced human myxovirus resistance protein A (MxA) exhibits a broad antiviral activity against many viruses, including influenza A virus (IAV). MxA belongs to the family of dynamin-like GTPases and assembles in vitro into dimers, tetramers, and oligomeric ring-like structures. The molecular mechanism of action remains to be elucidated. Furthermore, it is not clear whether MxA exerts its antiviral activity in a monomeric and/or multimeric form. Using a set of MxA mutants that form complexes with defined stoichiometry, we observed that, in the presence of guanosine 5-O-(thiotriphosphate), purified MxA disassembled into tetramers and dimers. Dimeric forms did not further disassemble into monomers. Infection experiments revealed that besides wild-type MxA, dimeric and monomeric variants of MxA also efficiently restricted IAV at a replication step after primary transcription. Moreover, only dimeric MxA was able to form stable complexes with the nucleoprotein (NP) of IAV. MxA interacted with NP independently of other viral components. Interestingly, the dimeric form of MxA was able to efficiently bind to NP from several MxA-sensitive strains but interacted much more weakly with NP from the MxA-resistant PR8 strain derived from the H1N1 1918 lineage. Taken together, these data suggest that, during infection, a fraction of MxA disassembles into dimers that bind to NP synthesized following primary transcription in the cytoplasm, thereby preventing viral replication.The interferon system plays a pivotal role in the defense against viral infection. Interferons type I and III induce the expression of more than 300 proteins, many of them exhibiting intrinsic antiviral activity (1-3). The human myxovirus resistance protein A (MxA) 3 protein is induced exclusively by type I and type III interferons and restricts the replication of a large variety of RNA and DNA viruses (reviewed in Ref. 4). Mx proteins are members of the dynamin superfamily of large GTPases. They contain an amino-terminal globular GTPase (G) domain and a carboxy-terminal stalk domain (5, 6). The stalk domain harbors the GTPase effector domain and additional structural elements, including the L4 loop required for antiviral activity and target specificity (7-9). The G and stalk domains are connected via the bundle signaling element (BSE), which strongly resembles the BSE responsible for intramolecular signaling in dynamin (10). Mx proteins exhibit a high intrinsic rate of GTP hydrolysis, although the affinity to GTP is weak (11). Moreover, the human MxA protein forms dimers and tetramers and has the capacity to form higher oligomeric ringlike structures through a series of intra-and intermolecular interactions (5, 6, 12, 13). Introduction of mutations into the interfaces of the intermolecular interaction sites or hinge regions of MxA prevents assembly into higher-order multimeric forms. These mutations lead to the formation of MxA into tetramers, dimers, and monomers (5, 12).So far, little is known about the molecular mechanism of action of the human MxA...

show abstract

Interferon-Inducible Protein Mx1 Inhibits Influenza Virus by Interfering with Functional Viral Ribonucleoprotein Complex Assembly

Cited by 188 publications

References 56 publications

The Nucleoprotein of Newly Emerged H7N9 Influenza A Virus Harbors a Unique Motif Conferring Resistance to Antiviral Human MxA

The Nucleoprotein of Newly Emerged H7N9 Influenza A Virus Harbors a Unique Motif Conferring Resistance to Antiviral Human MxA

Mx Proteins: Antiviral Gatekeepers That Restrain the Uninvited

Oligomerization and GTP-binding Requirements of MxA for Viral Target Recognition and Antiviral Activity against Influenza A Virus

Contact Info

Product

Resources

About