Functional IL6R 358Ala Allele Impairs Classical IL-6 Receptor Signaling and Influences Risk of Diverse Inflammatory Diseases

Abstract

Inflammation, which is directly regulated by interleukin-6 (IL-6) signaling, is implicated in the etiology of several chronic diseases. Although a common, non-synonymous variant in the IL-6 receptor gene (IL6R Asp358Ala; rs2228145 A>C) is associated with the risk of several common diseases, with the 358Ala allele conferring protection from coronary heart disease (CHD), rheumatoid arthritis (RA), atrial fibrillation (AF), abdominal aortic aneurysm (AAA), and increased susceptibility to asthma, the variant's effect on IL-6 signaling is not known. Here we provide evidence for the association of this non-synonymous variant with the risk of type 1 diabetes (T1D) in two independent populations and confirm that rs2228145 is the major determinant of the concentration of circulating soluble IL-6R (sIL-6R) levels (34.6% increase in sIL-6R per copy of the minor allele 358Ala; rs2228145 [C]). To further investigate the molecular mechanism of this variant, we analyzed expression of IL-6R in peripheral blood mononuclear cells (PBMCs) in 128 volunteers from the Cambridge BioResource. We demonstrate that, although 358Ala increases transcription of the soluble IL6R isoform (P = 8.3×10−22) and not the membrane-bound isoform, 358Ala reduces surface expression of IL-6R on CD4+ T cells and monocytes (up to 28% reduction per allele; P≤5.6×10−22). Importantly, reduced expression of membrane-bound IL-6R resulted in impaired IL-6 responsiveness, as measured by decreased phosphorylation of the transcription factors STAT3 and STAT1 following stimulation with IL-6 (P≤5.2×10−7). Our findings elucidate the regulation of IL-6 signaling by IL-6R, which is causally relevant to several complex diseases, identify mechanisms for new approaches to target the IL-6/IL-6R axis, and anticipate differences in treatment response to IL-6 therapies based on this common IL6R variant.

Shedding of Endogenous Interleukin-6 Receptor (IL-6R) Is Governed by A Disintegrin and Metalloproteinase (ADAM) Proteases while a Full-length IL-6R Isoform Localizes to Circulating Microvesicles

“…Whereas in humans a substantial fraction of serum sIL-6R can be attributed to alternative splicing of the IL-6R mRNA, the bulk of circulating sIL-6R appears to be generated by mechanisms distinct from differential mRNA splicing (13). A SNP within the ADAM17 cleavage site leads to increased serum sIL-6R levels in SNP carriers suggesting a decisive role of ectodomain shedding in serum sIL-6R generation (14,15). Surprisingly, hypomorphic ADAM17 ex/ex mice, which almost completely lack ADAM17 protein, exhibit unaltered serum sIL-6R levels pointing to the involvement of a different protease in serum sIL-6R generation.…”

“…Serum sIL-6R Is Not Released by ADAM10, ADAM8, Neutrophil Elastase, Cathepsin G, or Proteinase 3-A soluble form of the IL-6R is present in the blood of humans as well as mice and genome-wide association studies have reported a correlation between serum sIL-6R levels and the outcome of autoimmune diseases like asthma, rheumatoid arthritis, and type I diabetes (15,32). In that respect, it has been proposed that sIL-6R in conjunction with soluble gp130 (sgp130) in the blood operates as a buffer against IL-6 preventing global inflammation by overshooting IL-6 (33).…”

Phase II Study of Personalized Peptide Vaccination for Previously Treated Advanced Colorectal Cancer

“…The IL6R 48892C (358Ala) allele has been reported to affect proteolytic cleavage of the membrane-bound IL6R, leading to reduced numbers of the functioning IL6R (32). As a result, this genetic variant is suggested to contribute to anti-inflammatory effect through attenuation of IL6 signaling on cells expressing the membrane-bound IL6R (33)(34)(35). On the basis of our finding, the effect of reduced IL6R expression might be more prominent when the availability of IL6 is limited, whereas it might be overcome by overexpression of IL6.…”

CD126 and Targeted Therapy with Tocilizumab in Chronic Lymphocytic Leukemia

“…The constitutive activation of STAT3 in cancer results from chronic stimulation by extracellular signals in the microenvironment, including IL6 (23), and overexpression of CD126 enhanced IL6/STAT3 responses (16,28). In CLL cells, in vivo constitutively activated STAT3 involves phosphorylation of serine 727 residues (p-STAT3 S727 ) but not tyrosine 705 residues (19).…”