Interaction of mumps virus V protein variants with STAT1-STAT2 heterodimer: experimental and theoretical studies

Nora H Rosas-Murrieta,Irma Herrera-Camacho,Helen Palma-Ocampo,Julio Reyes-Leyva,Gerardo Santos-López

doi:10.1186/1743-422x-7-263

Nora H Rosas-Murrieta, Irma Herrera-Camacho + Show 3 more

Open Access

https://doi.org/10.1186/1743-422x-7-263

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Abstract

BackgroundMumps virus V protein has the ability to inhibit the interferon-mediated antiviral response by inducing degradation of STAT proteins. Two virus variants purified from Urabe AM9 mumps virus vaccine differ in their replication and transcription efficiency in cells primed with interferon. Virus susceptibility to IFN was associated with insertion of a non-coded glycine at position 156 in the V protein (VGly) of one virus variant, whereas resistance to IFN was associated with preservation of wild-type phenotype in the V protein (VWT) of the other variant.ResultsVWT and VGly variants of mumps virus were cloned and sequenced from Urabe AM9 vaccine strain. VGly differs from VWT protein because it possesses an amino acid change Gln103Pro (Pro103) and the Gly156 insertion. The effect of V protein variants on components of the interferon-stimulated gene factor 3 (ISGF3), STAT1 and STAT2 proteins were experimentally tested in cervical carcinoma cell lines. Expression of VWT protein decreased STAT1 phosphorylation, whereas VGly had no inhibitory effect on either STAT1 or STAT2 phosphorylation. For theoretical analysis of the interaction between V proteins and STAT proteins, 3D structural models of VWT and VGly were predicted by comparing with simian virus 5 (SV5) V protein structure in complex with STAT1-STAT2 heterodimer. In silico analysis showed that VWT-STAT1-STAT2 complex occurs through the V protein Trp-motif (W174, W178, W189) and Glu95 residue close to the Arg409 and Lys415 of the nuclear localization signal (NLS) of STAT2, leaving exposed STAT1 Lys residues (K85, K87, K296, K413, K525, K679, K685), which are susceptible to proteasome degradation. In contrast, the interaction between VGly and STAT1-STAT2 heterodimer occurs in a region far from the NLS of STAT2 without blocking of Lys residues in both STAT1 and STAT2.ConclusionsOur results suggest that VWT protein of Urabe AM9 strain of mumps virus may be more efficient than VGly to inactivate both the IFN signaling pathway and antiviral response due to differences in their finest molecular interaction with STAT proteins.

Highlights

Mumps virus V protein has the ability to inhibit the interferon-mediated antiviral response by inducing degradation of STAT proteins
It begins with attachment of IFN-a or -b to heterodimeric receptors composed of IFNAR1 and IFNAR2 subunits whose intracellular domains are associated with Tyk2 and Jak1 tyrosine kinases, respectively [1]
Heterodimer with IRF9 constitutes the IFN-stimulated gene factor 3 (ISGF3) transcription factor, which binds to IFN-stimulated response elements (ISRE) at IFN-stimulated genes (ISG)

Summary

Introduction

Mumps virus V protein has the ability to inhibit the interferon-mediated antiviral response by inducing degradation of STAT proteins. Interferon induces the major defense against viral infections It begins with attachment of IFN-a or -b to heterodimeric receptors composed of IFNAR1 and IFNAR2 subunits whose intracellular domains are associated with Tyk and Jak tyrosine kinases, respectively [1]. The final step of this signaling pathway is the induction of gene transcription whose expression establishes the antiviral state [2,7]. Several viruses have evolved strategies to circumvent the antiviral state stimulated by IFN through the expression of proteins that antagonize some components of the IFN signaling pathway such as the V protein of paramyxoviruses [8]. Mumps virus V protein is a nonstructural protein that counteracts the IFN-induced antiviral response [11]

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