Human Myxovirus Resistance Protein Research Articles

IFN-γ–Driven Intratumoral Microenvironment Exhibits Superior Prognostic Effect Compared with an IFN-α–Driven Microenvironment in Patients with Colon Carcinoma

Interferon (IFN)-α and IFN-γ are cytokines with potent immunomodulating and anti-tumor activities. It is unknown which of the two IFNs may be more potent in the regulation of an anti-tumorigenic response in colorectal carcinoma or whether both cytokines cooperate. We, therefore, established human myxovirus resistance protein A and human guanylate-binding protein-1 as markers for the differential detection of IFN-α- and IFN-γ-driven tumor micromilieus, respectively. In vitro studies with different cultures of tumor cells from colorectal carcinoma and stroma cells showed that the expression of myxovirus resistance protein A was exclusively induced by IFN-α, whereas guanylate-binding protein-1 was strongly induced by IFN-γ and only weakly by IFN-α. This expression pattern was used to distinguish cell activation caused by the two cytokines in a clinical cohort of patients with colon carcinoma (n = 378). Patients with primary tumors expressing only guanylate-binding protein-1 exhibited the highest cancer-specific 5-year survival (94.0%, P = 0.006) compared with those expressing both factors (90.3%, P = 0.006), myxovirus resistance protein A alone (83.5%, P = 0.096), or none (72.8%). Our study describes a successful proof-of-principle approach that complex cytokine interaction networks can be dissected in human tissues and demonstrates that an IFN-γ-driven tumor microenvironment exhibits a superior prognostic effect compared with an IFN-α-driven tumor microenvironment in colon carcinoma.

Human Myxovirus Resistance Protein 1 (MxA) as a useful marker in the differential diagnosis of subcutaneous lymphoma vs. lupus erythematosus profundus

Substantial clinicohistologic overlap exists between lupus erythematosus profundus (LEP) and lymphomas involving the subcutis, including subcutaneous panniculitis-like T-cell lymphoma (SPTCL) and primary cutaneous gamma/delta T-cell lymphoma (GDTCL). Unequivocal markers separating the entities are not established. To explore the usefulness of interferon alpha (INF-α)-induced protein, myxovirus resistance protein 1 (MxA), in the differential diagnosis of these entities, as studies show that the expression pattern of MxA follows the distribution of the inflammatory infiltrate in cutaneous lupus, while INF- α is not known to operate in lymphoma. MxA immunohistochemistry was performed on skin biopsies from 5 patients with a clinical and histological diagnosis of SPTCL, 9 patients with GDTCL and 9 patients with LEP. In SPTCL and GDTCL, MxA was primarily seen in macrophages and generally did not exceed 20% of the infiltrate. In contrast, a significant portion of the subcutaneous infiltrate was positive for MxA in LEP, with 50% of the infiltrate staining on average. A greater number of macrophages and lymphocytes stained with a greater intensity as well (P<0.001). Moreover, endothelial cell staining was uniquely identified in LEP but not in lymphoma. Although specificity is not 100%, minimal staining of MxA is a predictor for SPTCL or GDTCL. Conversely, extensive staining for MxA both qualitatively and quantitatively is a feature of LEP. Endothelial staining also appears to be specific for LEP.

Structure of Myxovirus Resistance Protein A Reveals Intra- and Intermolecular Domain Interactions Required for the Antiviral Function

Human myxovirus resistance protein 1 (MxA) is an interferon-induced dynamin-like GTPase that acts as a cell-autonomous host restriction factor against many viral pathogens including influenza viruses. To study the molecular principles of its antiviral activity, we determined the crystal structure of nucleotide-free MxA, which showed an extended three-domain architecture. The central bundle signaling element (BSE) connected the amino-terminal GTPase domain with the stalk via two hinge regions. MxA oligomerized in the crystal via the stalk and the BSE, which in turn interacted with the stalk of theneighboring monomer. We demonstrated that the intra- and intermolecular domain interplay between the BSE and stalk was essential for oligomerization and the antiviral function of MxA. Based on these results, we propose a structural model for the mechano-chemical coupling in ring-like MxA oligomers as the principle mechanism for this unique antiviral effector protein.

Human MxA Protein: An Interferon-Induced Dynamin-Like GTPase with Broad Antiviral Activity

The human myxovirus resistance protein 1 (MxA) is a key mediator of the interferon-induced antiviral response against a wide range of viruses. MxA expression is tightly regulated by type I and type III interferons, requires signal transducer and activator of transcription 1 signaling, and is not inducible directly by viruses or other stimuli. MxA shares many properties with the dynamin superfamily of large GTPases. It consists of 3 domains, namely, an N-terminal GTPase domain that binds and hydrolyses GTP, a middle domain mediating self-assembly, and a carboxy-terminal GTPase effector domain. Like dynamin, MxA has the ability to self-assemble into highly ordered oligomers and to form ring-like structures around liposomes, inducing liposome tubulation. The structural details of MxA oligomerization have recently been elucidated, providing new insights into the antiviral mechanism of this mechanochemical enzyme. The structural and functional data suggest that MxA targets the nucleoprotein of MxA-sensitive viruses. Thus, MxA may form oligomeric rings around tubular nucleocapsid structures, thereby inhibiting their transcriptional and replicative function. Here we briefly review the most salient features of MxA expression and antiviral function.

A Monoclonal Antibody Specific to Human Myxovirus Resistance Protein A

Recombinant human myxovirus resistance protein A (MxA) was successfully expressed by an Escherichia coli expression system. After immunization and cell fusion, a mouse hybridoma (3C2) producing MAbs to MxA was established. Hybridoma 3C2 was further characterized using indirect ELISA, Western blot analysis, immunofluorescent staining, and immunoprecipitation. The ELISA results showed that the titer of 3C2 was between 1:6400 and 1:12800 in ascitic fluids. The isotype of the monoclonal antibody was tested to be IgG1kappa. 3C2 can also specifically recognize human MxA protein in various formats by Western blot analysis, immunofluorescent staining, and immunoprecipitation assay. We further demonstrated that 3C2 could be used to detected MxA expression induce by type I interferon in A549 cell line and human peripheral blood mononuclear cells by Western blot in a dose-dependent manner.