Historical developments in the research of interferon receptors

Plasma membrane nanodeformations promote actin polymerization through CIP4/CDC42 recruitment and regulate type II IFN signaling

In their environment, cells must cope with mechanical stresses constantly. Among these, nanoscale deformations of plasma membrane induced by substrate nanotopography are now largely accepted as a biophysical stimulus influencing cell behavior and function. However, the mechanotransduction cascades involved and their precise molecular effects on cellular physiology are still poorly understood. Here, using homemade fluorescent nanostructured cell culture surfaces, we explored the role of Bin/Amphiphysin/Rvs (BAR) domain proteins as mechanosensors of plasma membrane geometry. Our data reveal that distinct subsets of BAR proteins bind to plasma membrane deformations in a membrane curvature radius-dependent manner. Furthermore, we show that membrane curvature promotes the formation of dynamic actin structures mediated by the Rho GTPase CDC42, the F-BAR protein CIP4, and the presence of PI(4,5)P2. In addition, these actin-enriched nanodomains can serve as platforms to regulate receptor signaling as they appear to contain interferon-γ receptor (IFNγ-R) and to lead to the partial inhibition of IFNγ-induced JAK/STAT signaling.

Insights into the Mechanism of Action of Highly Diluted Biologics

The therapeutic use of Abs in cancer, autoimmunity, transplantation, and other fields is among the major biopharmaceutical advances of the 20th century. Broader use of Ab-based drugs is constrained because of their high production costs and frequent side effects. One promising approach to overcome these limitations is the use of highly diluted Abs, which are produced by gradual reduction of an Ab concentration to an extremely low level. This technology was used to create a group of drugs for the treatment of various diseases, depending on the specificity of the used Abs. Highly diluted Abs to IFN-γ (hd-anti-IFN-γ) have been demonstrated to be efficacious against influenza and other respiratory infections in a variety of preclinical and clinical studies. In the current study, we provide evidence for a possible mechanism of action of hd-anti-IFN-γ. Using high-resolution solution nuclear magnetic resonance spectroscopy, we show that the drug induced conformational changes in the IFN-γ molecule. Chemical shift changes occurred in the amino acids located primarily at the dimer interface and at the C-terminal region of IFN-γ. These molecular changes could be crucial for the function of the protein, as evidenced by an observed hd-anti-IFN-γ-induced increase in the specific binding of IFN-γ to its receptor in U937 cells, enhanced induced production of IFN-γ in human PBMC culture, and increased survival of influenza A-infected mice.

Glycosylation-Dependent IFN-γR Partitioning in Lipid and Actin Nanodomains Is Critical for JAK Activation

Understanding how membrane nanoscale organization controls transmembrane receptors signaling activity remains a challenge. We studied interferon-γ receptor (IFN-γR) signaling in fibroblasts from homozygous patients with a T168N mutation in IFNGR2. By adding a neo-N-glycan on IFN-γR2 subunit, this mutation blocks IFN-γ activity by unknown mechanisms. We show that the lateral diffusion of IFN-γR2 is confined by sphingolipid/cholesterol nanodomains. In contrast, the IFN-γR2 T168N mutant diffusion is confined by distinct actin nanodomains where conformational changes required for Janus-activated tyrosine kinase/signal transducer and activator of transcription (JAK/STAT) activation by IFN-γ could not occur. Removing IFN-γR2 T168N-bound galectins restored lateral diffusion in lipid nanodomains and JAK/STAT signaling in patient cells, whereas adding galectins impaired these processes in control cells. These experiments prove the critical role of dynamic receptor interactions with actin and lipid nanodomains and reveal a new function for receptor glycosylation and galectins. Our study establishes the physiological relevance of membrane nanodomains in the control of transmembrane receptor signaling in vivo. VIDEO ABSTRACT.

Critical role of the endogenous interferon ligand-receptors in type I and type II interferons response

Separate ligand-receptor paradigms are commonly used for each type of interferon (IFN). However, accumulating evidence suggests that type I and type II IFNs may not be restricted to independent pathways. Using different cell types deficient in IFNAR1, IFNAR2, IFNGR1, IFNGR2 and IFN-γ, we evaluated the contribution of each element of the IFN system to the activity of type I and type II IFNs. We show that deficiency in IFNAR1 or IFNAR2 is associated with impairment of type II IFN activity. This impairment, presumably resulting from the disruption of the ligand-receptor complex, is obtained in all cell types tested. However, deficiency of IFNGR1, IFNGR2 or IFN-γ was associated with an impairment of type I IFN activity in spleen cells only, correlating with the constitutive expression of type II IFN (IFN-γ) observed on those cells. Therefore, in vitro the constitutive expression of both the receptors and the ligands of type I or type II IFN is critical for the enhancement of the IFN activity. Any IFN deficiency can totally or partially impair IFN activity, suggesting the importance of type I and type II IFN interactions. Taken together, our results suggest that type I and type II IFNs may regulate biological activities through distinct as well as common IFN receptor complexes.

Ligand-independent interaction of the type I interferon receptor complex is necessary to observe its biological activity

Ectopic coexpression of the two chains of the Type I and Type III interferon (IFN) receptor complexes (IFN-αR1 and IFN-αR2c, or IFN-λR1 and IL-10R2) yielded sensitivity to IFN-alpha or IFN-lambda in only some cells. We found that IFN-αR1 and IFN-αR2c exhibit FRET only when expressed at equivalent and low levels. Expanded clonal cell lines expressing both IFN-αR1 and IFN-αR2c were sensitive to IFN-alpha only when IFN-αR1 and IFN-αR2c exhibited FRET in the absence of human IFN-alpha. Coexpression of RACK-1 or Jak1 enhanced the affinity of the interaction between IFN-αR1 and IFN-αR2c. Both IFN-αR1 and IFN-αR2c exhibited FRET with Jak1 and Tyk2. Together with data showing that disruption of the preassociation between the IFN-gamma receptor chains inhibited its biological activity, we propose that biologically active IFN receptors require ligand-independent juxtaposition of IFN receptor chains assisted by their associated cytosolic proteins.

Interferons as biomarkers and effectors: lessons learned from animal models

Interferons (IFNs) comprise type I, II and III families with multiple subtypes. Via transcription of IFN-stimulated genes (ISGs), IFNs can exert multiple biological effects on the cell. In infectious and chronic inflammatory diseases, the IFNs and their ISG sets can be potentially utilized as biomarkers of disease outcome. Animal models allow investigations into disease pathogenesis and gene knockout models have proved cause and effect relationships of molecules related to the IFN response. Sets of IFN subtypes and their ISG products provide immunological signature patterns for different viral and other diseases. In this article, we give an overview of IFNs in several virus infection models and autoimmune diseases of medical relevance. Lessons learned from animal models inform us of IFN system parameters as indicators of disease outcome and whether clinical research is warranted. Moreover, validated IFN biomarkers for prognosis enhance our understanding of therapeutic and vaccine development.

Binding and activity of all human alpha interferon subtypes

Vertebrates have multiple genes encoding Type I interferons (IFN), for reasons that are not fully understood. The Type I IFN appear to bind to the same heterodimeric receptor and the subtypes have been shown to have different potencies in various experimental systems. To put this concept on a quantitative basis, we have determined the binding affinities and rate constants of 12 human Alpha-IFN subtypes to isolated interferon receptor chains 1 and 2. Alpha-IFNs bind IFNAR1 and IFNAR2 at affinities of 0.5-5 μM and 0.4-5 nM respectively (except for IFN-alpha1 - 220 nM). Additionally we have examined the biological activity of these molecules in several antiviral and antiproliferative models. Particularly for antiproliferative potency, the binding affinity and activity correlate. However, the EC50 values differ significantly (1.5 nM versus 0.1 nM for IFN-alpha2 in WISH versus OVCAR cells). For antiviral potency, there are several instances where the relationship appears to be more complicated than simple binding. These results will serve as a point of reference for further understanding of this multiple ligand/receptor system.

Reduced IFN-γ receptor expression and attenuated IFN-γ response by dendritic cells in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is characterized by a predominance of T(H)2 immune reactions but weaker T(H)1 immune responses in acute skin lesions.

OBJECTIVES

To evaluate whether enhanced T(H)2 immunity in patients with AD might impair T(H)1 immune responses by affecting the IFN-γ responsiveness of antigen-presenting cells, we investigated IFN-γ receptor and IL-4 receptor α chain expression, IFN-γ signaling, and the expression of IFN-γ-responsive mediators in dendritic cells (DCs) and their precursors from patients with AD compared with those from healthy subjects.

METHODS

Skin biopsy specimens were obtained and both monocytes and monocyte-derived dendritic cells (MoDCs) from patients with AD (n = 86) and control subjects (n = 84) were analyzed by means of flow cytometry, real-time PCR, ELISA, and HPLC.

RESULTS

We observed lower IFN-γ receptor II expression combined with higher IL-4 receptor α chain expression on epidermal DCs, monocytes, and MoDCs from patients with AD. Induction of IFN-γ-inducible factors, such as interferon regulatory factor 1, interferon-inducible protein 10, and indoleamine 2,3-dioxygenase, was attenuated in IFN-γ-pulsed MoDCs from patients with AD. Weaker signal transducer and activator of transcription 1 activation mirrored by lower phosphorylated signal transducer and activator of transcription 1 levels in response to IFN-γ stimulation could be observed in epidermal DCs, monocytes, and MoDCs from patients with AD.

CONCLUSION

Impaired IFN-γ signaling together with attenuated IFN-γ responses in DCs and their precursor cells might contribute to the T(H)2 bias in patients with AD.

Interferon modulates central nervous system function

The interferons (IFNs) are an endogenous pleiotropic family of cytokines that perform fundamental physiological functions as well as protecting host organisms from disease and in maintaining homeostasis. This review covers the effects of endogenous IFN on the nervous system. It starts with the description of its receptors, followed how it modulate neuronal activity, mood, sleep, temperature, the endocrine system, the opioid system and how it regulate food consumption and the immune system. Similar to other multifunctional cytokines, an excessive or inappropriate activity of IFNs can cause toxicity and even death. Furthermore, IFNs are currently the major treatment modality for several malignant and non-malignant diseases such as chronic hepatitis C and B, multiple sclerosis, hematological malignancies, malignant melanoma, renal cell carcinoma, etc.

How vaccinia virus has evolved to subvert the host immune response

Viruses are obligate intracellular parasites and are some of the most rapidly evolving and diverse pathogens encountered by the host immune system. Large complicated viruses, such as poxviruses, have evolved a plethora of proteins to disrupt host immune signalling in their battle against immune surveillance. Recent X-ray crystallographic analysis of these viral immunomodulators has helped form an emerging picture of the molecular details of virus-host interactions. In this review we consider some of these immune evasion strategies as they apply to poxviruses, from a structural perspective, with specific examples from the European SPINE2-Complexes initiative. Structures of poxvirus immunomodulators reveal the capacity of viruses to mimic and compete against the host immune system, using a diverse range of structural folds that are unique or acquired from their hosts with both enhanced and unexpectedly divergent functions.

Intratumoral injection of interferon-α and systemic delivery of agonist anti-CD137 monoclonal antibodies synergize for immunotherapy

CD137 artificial costimulation results in complete tumor rejection in several mouse models. Type I interferons (IFN) exert antitumor effects through an array of molecular functions on malignant cells, tumor stroma and immune system cells. The fact that agonist anti-CD137 mAb induce tumor regressions in mice deficient in the unique receptor for Type I IFNs (IFNAR(-/-) ) indicated potential for treatment combinations. Indeed, combination of intratumor injections of mouse IFN-α and intraperitoneal injections of anti-CD137 mAb synergized as seen on subcutaneous lesions derived from the MC38 colon carcinoma, which is resistant to each treatment if given separately. Therapeutic activity was achieved both against lesions directly injected with IFN-α and against distant concomitant tumors. Experiments in bone marrow chimeras prepared with IFNAR(-/-) and WT mice concluded that expression of the receptor for Type I interferons is mainly required on cells of the hematopoietic compartment. Synergistic effects correlated with a remarkable cellular hyperplasia of the tumor draining lymph nodes (TDLNs). Enlarged TDLNs contained more plasmacytoid and conventional dendritic cells (DC) that more readily cross-presented. Importantly, numbers of both DC subtypes inversely correlated with the tumor size. Numbers of CD8 T cells specific for a dominant tumor antigen were increased at TDLNs by each separate treatment but only with slight augments due to the combination. Combined antitumor effects of the therapeutic strategy were also seen on subcutaneous TC-1 tumors established for 24 days before treatment onset. The described strategy is realistic because (i) agents of each kind are clinically available and (ii) equivalent procedures in humans are feasible.

Octamer-binding factor 6 (Oct-6/Pou3f1) is induced by interferon and contributes to dsRNA-mediated transcriptional responses

BACKGROUND

Octamer-binding factor 6 (Oct-6, Pou3f1, SCIP, Tst-1) is a transcription factor of the Pit-Oct-Unc (POU) family. POU proteins regulate key developmental processes and have been identified from a diverse range of species. Oct-6 expression is described to be confined to the developing brain, Schwann cells, oligodendrocyte precursors, testes, and skin. Its function is primarily characterised in Schwann cells, where it is required for correctly timed transition to the myelinating state. In the present study, we report that Oct-6 is an interferon (IFN)-inducible protein and show for the first time expression in murine fibroblasts and macrophages.

RESULTS

Oct-6 was induced by type I and type II IFN, but not by interleukin-6. Induction of Oct-6 after IFNbeta treatment was mainly dependent on signal transducer and activator of transcription 1 (Stat1) and partially on tyrosine kinase 2 (Tyk2). Chromatin immunopreciptitation experiments revealed binding of Stat1 to the Oct-6 promoter in a region around 500 bp upstream of the transcription start site, a region different from the downstream regulatory element involved in Schwann cell-specific Oct-6 expression. Oct-6 was also induced by dsRNA treatment and during viral infections, in both cases via autocrine/paracrine actions of IFNalpha/beta. Using microarray and RT-qPCR, we furthermore show that Oct-6 is involved in the regulation of transcriptional responses to dsRNA, in particular in the gene regulation of serine/threonine protein kinase 40 (Stk40) and U7 snRNA-associated Sm-like protein Lsm10 (Lsm10).

CONCLUSION

Our data show that Oct-6 expression is not as restricted as previously assumed. Induction of Oct-6 by IFNs and viruses in at least two different cell types, and involvement of Oct-6 in gene regulation after dsRNA treatment, suggest novel functions of Oct-6 in innate immune responses.

The Th17 cytokine IL-22 induces IL-20 production in keratinocytes: a novel immunological cascade with potential relevance in psoriasis

Psoriasis is a common chronic skin disease. Recent studies demonstrated that IL-20 and IL-22, cytokines produced by keratinocytes and T cells, respectively, both inhibit keratinocyte terminal differentiation and induce psoriasis-like epidermis alterations. Here, we investigated the relationship between these mediators. Although IL-20 was not able to regulate IL-22 production, IL-22 induced IL-20 mRNA and protein in human keratinocytes. However, IL-22 had only a minimal effect, if any, on IL-19 and IL-26. Cutaneous IL-20 was also elevated in mice following IL-22 application. Accordingly, some of IL-22's effects on differentiation-regulating genes were partially mediated by an endogenous, secreted protein and attenuated by anti-IL-20 Ab. Like IL-22, IL-17A and TNF-alpha induced IL-20 in keratinocytes, whereas IFN-gamma and IL-20 itself did not. Furthermore, IL-17A and TNF-alpha individually strengthened the IL-22-induced IL-20 production. In lesional skin of psoriasis patients, highly elevated IL-20 levels strongly correlated with IL-22, and to a lesser extent, with IL-17A and TNF-alpha. As previously shown for IL-22, IL-20 blood levels correlated with the disease severity, although with a lower significance. This study demonstrates that a T-cell mediator induces a tissue cell mediator with similar effects to its own and therefore suggests the existence of a novel type of pathogenetic cascade.

The search for the IFN-gamma receptor in fish: Functional and expression analysis of putative binding and signalling chains in rainbow trout Oncorhynchus mykiss

Interferons (IFNs), consisting of three major subfamilies, type I, type II (gamma) and type III (lambda) IFN, activate vertebrate antiviral defences once bound to their receptors. The three IFN subfamilies bind to different receptors, IFNAR1 and IFNAR2 for type I IFNs, IFNgammaR1 and IFNgammaR2 for type II IFN, and IL-28R1 and IL-10R2 for type III IFNs. In fish, although many types I and II IFN genes have been cloned, little is known about their receptors. In this report, two putative IFN-gamma receptor chains were identified and sequenced in rainbow trout (Oncorhynchus mykiss), and found to have many common characteristics with mammalian type II IFN receptor family members. The presented gene synteny analysis, phylogenetic tree analysis and ligand binding analysis all suggest that these molecules are the authentic IFNgammaRs in fish. They are widely expressed in tissues, with IFNgammaR1 typically more highly expressed than IFNgammaR2. Using the trout RTG-2 cell line it was possible to show that the individual chains could be differentially modulated, with rIFN-gamma and rIL-1beta down regulating IFNgammaR1 expression but up regulating IFNgammaR2 expression. Over-expression of the two receptor chains in RTG-2 cells revealed that the level of IFNgammaR2 transcript was crucial for responsiveness to rIFN-gamma, in terms of inducing gammaIP expression. Transfection experiments showed that the two putative receptors specifically bound to rIFN-gamma. These findings are discussed in the context of how the IFNgammaR may bind IFN-gamma in fish and the importance of the individual receptor chains to signal transduction.

Interferon-induced Mx proteins in brain tissue of multiple sclerosis patients

BACKGROUND AND PURPOSE

Recombinant interferon-beta is proven as an effective long-term treatment in patients with multiple sclerosis (MS). Unlike in other chronic inflammatory diseases, endogenous synthesis of type I interferons (IFN-alpha and IFN-beta) has not been studied extensively in MS. Mx proteins A and B (MxA and MxB) are intracellular proteins that are induced exclusively by type I IFNs. We investigated the expression of Mx proteins in post-mortem brain tissue of IFN-beta-naïve MS patients as a marker for endogenous synthesis of type I IFNs.

METHODS

By employing monoclonal antibodies specific for MxA and MxB positive staining was detectable predominantly in reactive astrocytes within the MS plaques but also in endothelial and ependymal cells as well as in lymphocytic infiltrates.

RESULTS

This is of interest in view of results previously published by our group and others that Mx protein concentrations measured by ELISA increase in blood samples from MS patients after IFN-beta therapy.

CONCLUSIONS

In MS, Mx proteins are detectable in plaques suggesting endogenous synthesis of type I IFNs as part of the acute inflammatory process.

Dimeric quaternary structure of the prototypical dual specificity phosphatase VH1

The Vaccinia virus H1 gene product, VH1, is a dual specificity phosphatase that down-regulates the cellular antiviral response by dephosphorylating STAT1. The crystal structure of VH1, determined at 1.32 A resolution, reveals a novel dimeric quaternary structure, which exposes two active sites spaced approximately 39 A away from each other. VH1 forms a stable dimer via an extensive domain swap of the N-terminal helix (residues 1-20). In vitro, VH1 can dephosphorylate activated STAT1, in a reaction that is competed by the nuclear transport adapter importin alpha5. Interestingly, VH1 is inactive with respect to STAT1 bound to DNA, suggesting that the viral phosphatase acts predominantly on the cytoplasmic pool of activated STAT1. We propose that the dimeric quaternary structure of VH1 is essential for specific recognition of activated STAT1, which prevents its nuclear translocation, thus blocking interferon-gamma signal transduction and antiviral response.

Polymorphisms of interferons and their receptors in the genetics of severe RSV-associated diseases

Because of their important role in the pathophysiology of severe RSV infection, IFNs represent an ideal group of candidate genes for determining RSV disease severity. We studied 14 polymorphisms within 7 genes involved in IFNs signalling. Our study populations consisted of 156 infants with severe RSV infection and 296 healthy control children. None of the genes showed association with severe RSV infection in children. Thus, despite the involvement of different IFNs in the pathophysiology of RSV infection, genetic variants in IFNG and related genes might not alter the risk for the development of severe RSV-associated diseases.

Tyrosine phosphorylation regulates the partitioning of STAT1 between different dimer conformations

The activation/inactivation cycle of STAT transcription factors entails their transition between different dimer conformations. Unphosphorylated STATs can dimerize in an antiparallel conformation via extended interfaces of the globular N-domains, whereas STAT activation triggers a parallel dimer conformation with mutual phosphortyrosine:SH2 domain interactions, resulting in DNA-binding and nuclear retention. However, despite the crucial role of STAT tyrosine phosphorylation in cytokine signaling, it has not been determined how this modification affects the stability and the conformational flexibility of STAT dimers. Here, we use analytical ultracentrifugation and electrophoretic mobility shift assay (EMSA) to study the association of STAT1 in solution before and after tyrosine phosphorylation. It is revealed that STAT1 formed high-affinity dimers (K(d) of approximately 50 nM) with estimated half-lives of 20-40 min irrespective of the phosphorylation status. Our results demonstrate that parallel and antiparallel conformations of STAT1 were present simultaneously, supported by mutually exclusive interfaces; and the transition between conformations occurred through affinity-driven dissociation/association reactions. Therefore, tyrosine phosphorylation was dispensable for DNA binding, but the phosphorylation enforced preformed SH2 domain-mediated dimers, thus enhancing the DNA-binding activity of STAT1 >200-fold. Moreover, upon STAT1 activation the N-domains adopted an open conformation and engaged in interdimer interactions, as demonstrated by their participation in tetramerization instead of dimerization. Yet, homotypic N-domain interactions are not conserved in the STAT family, because the N-domain dissociation constants of STAT1, STAT3, and STAT4 differed by more than three orders of magnitude. In conclusion, STAT1 constantly oscillated between different dimer conformations, whereby the abundance of the dimerization interfaces was determined by tyrosine phosphorylation.