Sequential proteolytic processing of an interferon-alpha receptor subunit by TNF-alpha converting enzyme and presenilins

IFNAR2 relevance in the clinical outcome of individuals with severe COVID-19

Interferons (IFNs) are a group of cytokines with antiviral, antiproliferative, antiangiogenic, and immunomodulatory activities. Type I IFNs amplify and propagate the antiviral response by interacting with their receptors, IFNAR1 and IFNAR2. In COVID-19, the IFNAR2 (interferon alpha and beta receptor subunit 2) gene has been associated with the severity of the disease, but the soluble receptor (sIFNAR2) levels have not been investigated. We aimed to evaluate the association of IFNAR2 variants (rs2236757, rs1051393, rs3153, rs2834158, and rs2229207) with COVID-19 mortality and to assess if there was a relation between the genetic variants and/or the clinical outcome, with the levels of sIFNAR2 in plasma samples from hospitalized individuals with severe COVID-19. We included 1,202 subjects with severe COVID-19. The genetic variants were determined by employing Taqman® assays. The levels of sIFNAR2 were determined with ELISA in plasma samples from a subgroup of 351 individuals. The rs2236757, rs3153, rs1051393, and rs2834158 variants were associated with mortality risk among patients with severe COVID-19. Higher levels of sIFNAR2 were observed in survivors of COVID-19 compared to the group of non-survivors, which was not related to the studied IFNAR2 genetic variants. IFNAR2, both gene, and soluble protein, are relevant in the clinical outcome of patients hospitalized with severe COVID-19.

Soluble Receptor Isoform of IFN-Beta (sIFNAR2) in Multiple Sclerosis Patients and Their Association With the Clinical Response to IFN-Beta Treatment

Purpose

Interferon beta receptor 2 subunit (IFNAR2) can be produced as a transmembrane protein, but also as a soluble form (sIFNAR2) generated by alternative splicing or proteolytic cleavage, which has both agonist and antagonist activities for IFN-β. However, its role regarding the clinical response to IFN-β for relapsing-remitting multiple sclerosis (RRMS) is unknown. We aim to evaluate the in vitro short-term effects and after 6 and 12 months of IFN-β therapy on sIFNAR2 production and their association with the clinical response in MS patients.

Methods

Ninety-four RRMS patients were included and evaluated at baseline, 6 and 12 months from treatment onset. A subset of 41 patients were classified as responders and non-responders to IFN-β therapy. sIFNAR2 serum levels were measured by ELISA. mRNA expression for IFNAR1, IFNAR2 splice variants, MxA and proteases were assessed by RT-PCR. The short-term effect was evaluated in PBMC from RRMS patients after IFN-β stimulation in vitro.

Results

Protein and mRNA levels of sIFNAR2 increased after IFN-β treatment. According to the clinical response, only non-responders increased sIFNAR2 significantly at both protein and mRNA levels. sIFNAR2 gene expression correlated with the transmembrane isoform expression and was 2.3-fold higher. While MxA gene expression increased significantly after treatment, IFNAR1 and IFNAR2 only slightly increased. After short-term IFN-β in vitro induction of PBMC, 6/7 patients increased the sIFNAR2 expression.

Conclusions

IFN-β administration induces the production of sIFNAR2 in RRMS and higher levels might be associated to the reduction of therapeutic response. Thus, levels of sIFNAR2 could be monitored to optimize an effective response to IFN-β therapy.

Structural integrity with functional plasticity: what type I IFN receptor polymorphisms reveal

The type I IFNs activate an array of signaling pathways, which are initiated after IFNs bind their cognate receptors, IFNα/β receptor (IFNAR)1 and IFNAR2. These signals contribute to many aspects of human health including defense against pathogens, cancer immunosurveillance, and regulation of inflammation. How these cytokines interact with their receptors influences the quality of these signals. As such, the integrity of receptor structure is pivotal to maintaining human health and the response to immune stimuli. This review brings together genome wide association studies and clinical reports describing the association of nonsynonymous IFNAR1 and IFNAR2 polymorphisms with clinical disease, including altered susceptibility to viral and bacterial pathogens, autoimmune diseases, cancer, and adverse reactions to live-attenuated vaccines. We describe the amino acid substitutions or truncations induced by these polymorphisms and, using the knowledge of IFNAR conformational changes, IFNAR-IFN interfaces and overall structure-function relationship of the signaling complexes, we hypothesize the effect of these polymorphisms on receptor structure. That these predicted changes to IFNAR structure are associated with clinical manifestations of human disease, highlights the importance of IFNAR structural integrity to maintaining functional quality of these receptor-mediated responses. Type I IFNs are pivotal to innate immune responses and ultimately, to human health. Understanding the consequences of altered structure on the actions of these clinically significant cell receptors provides important information on the roles of IFNARs in health and disease.

An Essential Role for Perforin-2 in Type I IFN Signaling

Type I IFNs play a complex role in determining the fate of microbial pathogens and may also be deleterious to the host during bacterial and viral infections. Upon ligand binding, a receptor proximal complex consisting of IFN-α and -β receptors 1 and 2 (IFNAR1, IFNAR2, respectively), tyrosine kinase 2 (Tyk2), Jak1, and STAT2 are assembled and promote the phosphorylation of STAT1 and STAT2. However, how the IFNARs proximal complex is assembled upon binding to IFN is poorly understood. In this study, we show that the membrane-associated pore-forming protein Perforin-2 (P2) is critical for LPS-induced endotoxic shock in wild-type mice. Type I IFN-mediated JAK-STAT signaling is severely impaired, and activation of MAPKs and PI3K signaling pathways are delayed in P2-deficient mouse bone marrow-derived macrophages, mouse embryonic fibroblasts (MEFs), and human HeLa cells upon IFN stimulation. The P2 N-glycosylated extracellular membrane attack complex/perforin domain and the P2 domain independently associate with the extracellular regions of IFNAR1 and IFNAR2, respectively, in resting MEFs. In addition, the P2 cytoplasmic tail domain mediated the constitutive interaction between STAT2 and IFNAR2 in resting MEFs, an interaction that is dependent on the association of the extracellular regions of P2 and IFNAR2. Finally, the constitutive association of P2 with both receptors and STAT2 is critical for the receptor proximal complex assembly and reciprocal transphosphorylation of Jak1 and Tyk2 as well as the phosphorylation and activation of STAT1 and STAT2 upon IFN-β stimulation.

Decreased soluble IFN-β receptor (sIFNAR2) in multiple sclerosis patients: A potential serum diagnostic biomarker

Background:

The soluble isoform of the interferon-β (IFN-β) receptor (sIFNAR2) could modulate the activity of both endogenous and systemically administered IFN-β. Previously, we described lower serum sIFNAR2 levels in untreated multiple sclerosis (MS) than in healthy controls (HCs).

Objective:

To assess sIFNAR2 levels in a new cohort of MS patients and HCs, as well as in patients with clinically isolated syndrome (CIS) and with other inflammatory neurological disorders (OIND) and to assess its ability as a diagnostic biomarker.

Methods:

The cross-sectional study included 148 MS (84 treatment naive and 64 treated), 87 CIS, 42 OIND, and 96 HCs. Longitudinal study included 94 MS pretreatment and after 1 year of therapy with IFN-β, glatiramer acetate (GA), or natalizumab. sIFNAR2 serum levels were measured by a quantitative ELISA developed and validated in our laboratory.

Results:

Naive MS and CIS patients showed significantly lower sIFNAR2 levels than HCs and OIND patients. The sensitivity and specificity to discriminate between MS and OIND, for a sIFNAR2 cutoff value of 122.02 ng/mL, were 70.1%, and 79.4%, respectively. sIFNAR2 increased significantly in IFN-β-treated patients during the first year of therapy in contrast to GA- and natalizumab-treated patients who showed non-significant changes.

Conclusion:

The results suggest that sIFNAR2 could be a potential diagnostic biomarker for MS.