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Interferon-induced human protein MxA is a GTPase which binds transiently to cellular proteins.

ABSTRACT: MxA is an abundant and ubiquitous cytoplasmic protein induced by alpha/beta interferon in human cells. Upon full induction, it can constitute 0.5 to 1% of cytosolic proteins. MxA can bind elements of the cytoskeleton, such as actin and tubulins, and several larger cellular proteins. However, these protein-protein interactions seem to be transitory. The human MxA protein contains a tripartite GTP-binding domain consisting of GxxxxGKS, DxxG, and TKxD, where x is any amino acid. It is shown here that the native MxA protein has GTPase activity (GTP----GDP) when purified by immunoprecipitation with affinity-purified polyclonal antibodies directed against the C-terminal domain of MxA. The GTPase activity is greatly diminished by polyclonal antibodies directed against the N-terminal domain of MxA (the domain which contains the GTP-binding consensus elements). Amino acid substitution within the GTP-binding domain abolished the GTPase activity of the mutated MxA protein expressed in transfected CHO cells. The reaction is specific for GTP, and the approximate Km is 0.1 mM. The reaction has an absolute requirement for Mg2+. The turnover number is approximately 70 molecules of GTP hydrolyzed per min per MxA molecule. It is suggested that the human MxA protein has certain characteristics of the stress proteins.

SUBMITTER: Horisberger MA

PROVIDER: S-EPMC241296 | biostudies-other | 1992 Aug

REPOSITORIES: biostudies-other

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Interferon-induced human protein MxA is a GTPase which binds transiently to cellular proteins.

Horisberger M A MA

Journal of virology 19920801 8

MxA is an abundant and ubiquitous cytoplasmic protein induced by alpha/beta interferon in human cells. Upon full induction, it can constitute 0.5 to 1% of cytosolic proteins. MxA can bind elements of the cytoskeleton, such as actin and tubulins, and several larger cellular proteins. However, these protein-protein interactions seem to be transitory. The human MxA protein contains a tripartite GTP-binding domain consisting of GxxxxGKS, DxxG, and TKxD, where x is any amino acid. It is shown here th ...[more]

PMID: 1629950

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Project description:UnlabelledMany viruses trigger the type I interferon (IFN) pathway upon infection, resulting in the transcription of hundreds of interferon-stimulated genes (ISGs), which define the antiviral state of the host. Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), a highly contagious viral disease endangering the pig industry in many countries. However, anti-CSFV ISGs are poorly documented. Here we screened 20 ISGs that are commonly induced by type I IFNs against CSFV in lentivirus-delivered cell lines, resulting in the identification of guanylate-binding protein 1 (GBP1) as a potent anti-CSFV ISG. We observed that overexpression of GBP1, an IFN-induced GTPase, remarkably suppressed CSFV replication, whereas knockdown of endogenous GBP1 expression by small interfering RNAs significantly promoted CSFV growth. Furthermore, we demonstrated that GBP1 acted mainly on the early phase of CSFV replication and inhibited the translation efficiency of the internal ribosome entry site of CSFV. In addition, we found that GBP1 was upregulated at the transcriptional level in CSFV-infected PK-15 cells and in various organs of CSFV-infected pigs. Coimmunoprecipitation and glutathione S-transferase (GST) pulldown assays revealed that GBP1 interacted with the NS5A protein of CSFV, and this interaction was mapped in the N-terminal globular GTPase domain of GBP1. Interestingly, the K51 of GBP1, which is crucial for its GTPase activity, was essential for the inhibition of CSFV replication. We showed further that the NS5A-GBP1 interaction inhibited GTPase activity, which was critical for its antiviral effect. Taking our findings together, GBP1 is an anti-CSFV ISG whose action depends on its GTPase activity.ImportanceClassical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), an economically important viral disease affecting the pig industry in many countries. To date, only a few host restriction factors against CSFV, including interferon-stimulated genes (ISGs), have been characterized. Using a minilibrary of porcine ISGs, we identify porcine guanylate-binding protein 1 (GBP1) as a potent antiviral ISG against CSFV. We further show that the anti-CSFV action of GBP1 depends on its GTPase activity. The K51 of GBP1, critical for its GTPase activity, is essential for the antiviral action of GBP1 against CSFV replication, and the binding of the NS5A protein to GBP1 antagonizes the GTPase activity and thus the antiviral effect. This study will facilitate the development of anti-CSFV therapeutic agents by targeting host factors and may provide a new strategy for the control of CSF.

Dataset Information

Interferon-induced human protein MxA is a GTPase which binds transiently to cellular proteins.

Publications

Interferon-induced human protein MxA is a GTPase which binds transiently to cellular proteins.

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