Mechanisms of asthma and allergic inflammation
Effect of IL-13 receptor α2 levels on the biological activity of IL-13 variant R110Q

https://doi.org/10.1016/j.jaci.2007.04.026Get rights and content

Background

IL-13 is a key cytokine associated with the asthmatic phenotype. IL-13 signals via its cognate receptor, a complex of IL-13 receptor (IL-13R) α 1 chain with IL-4 receptor α; however, a second protein, IL-13Rα2, also binds IL-13. Recently a polymorphic variant of IL-13 (R110Q) has been shown to be associated with atopy.

Objective

To investigate the binding properties of this IL-13 variant to its cognate receptors.

Methods

We used surface plasmon resonance to measure the binding kinetics of R110Q to its receptors. Primary human fibroblasts were grown from endobronchial biopsies obtained from volunteers. Receptor levels were measured by fluorescence-activated cell sorting.

Results

There was no significant difference in the binding of R110Q with soluble human IL-13Rα1 compared with IL-13 (32 ± 5 nmol/L and 36 ± 7 nmol/L, respectively; P = .625). However, a small but significant difference was observed in the binding of R110Q to soluble human IL-13Rα2 compared with IL-13 (840 ± 87 pmol/L and 1.1 ± .05 nmol/L, respectively; P = .04). We observed that primary human lung fibroblasts expressed different levels of IL-13Rα2. Eotaxin release from fibroblasts expressing low IL-13Rα2 levels was significantly higher in response to R110Q compared with IL-13. This was not evident in cells that had high baseline IL-13Rα2 levels.

Conclusion

These results suggest that relatively small changes in functional properties of a ligand combined with variation in receptor levels in vivo can result in significant differences in responsiveness.

Clinical implications

Expression of R110Q and low IL-13Rα2 levels can result in important biological differences that may have clinical relevance in an atopic environment.

Section snippets

Reagents

CM5 sensor chip, HBS buffer (10 nmol/L HEPES with 0.15 mol/L NaCl, 3.4 mmol/L EDTA, and 0.005% surfactant P20), amine coupling kit, and regeneration agents were supplied by BIAcore (Uppsala, Sweden) unless otherwise stated. The extracellular region of IL-13Rα1 and IL-13Rα2 was fused to the Fc portion of hIgG1 to generate a soluble form of these IL-13 receptors (soluble human [sh] IL-13Rα1.Fc, shIL-13α2.Fc). Eotaxin ELISA kit, recombinant shIL-13Rα1.Fc, shIL-13α2.Fc, and neutralizing IL-13Rα2

Kinetic analysis of R110Q

Previous studies have shown that a soluble form of IL-13Rα2 cannot neutralize the effects of R110Q as efficiently as wild-type IL-13.27, 28 Because both receptor levels and ligand affinity are both key factors in the determining the functional outcome of a receptor mediated response, we first evaluated the binding affinity of R110Q for its cognate receptor chains.

The binding kinetics of IL-13 and R110Q to shIL-13Rα1 and shIL-13Rα2 were analyzed in real time by surface plasmon resonance (SPR)

Discussion

Several studies have established a link between genetic factors such as polymorphic variation in components of the IL-4 and IL-13 pathways and the development of allergic inflammation.32, 33, 34 However, it is an understanding of the functional consequences of these variants that will eventually reveal how these genetic susceptibilities translate into the development of asthma or other allergic diseases. Furthermore, when polymorphic variation occurs in more than 1 component of a pathway, as

References (37)

Cited by (30)

  • The Genetics of Allergic Disease and Asthma

    2016, Pediatric Allergy: Principles and Practice: Third Edition
  • The discovery, engineering and characterisation of a highly potent anti-human IL-13 fab fragment designed for administration by inhalation

    2013, Journal of Molecular Biology
    Citation Excerpt :

    This supported work by Arima et al. who demonstrated that R130Q variant hIL-13 had a lower affinity for IL-13Rα2 than wild-type hIL-13.10 More recently, Andrews et al. have shown that R130Q variant IL-13 was a potent inducer of eotaxin release and STAT-6 phosphorylation in human lung fibroblasts where expression of IL-13Rα2 was low.49 These studies clearly highlight the importance of neutralising both wild type and R130Q variant hIL-13 with an antibody.

  • The Genetics of Allergic Disease and Asthma

    2010, Pediatric Allergy: Principles and Practice Expert Consult: Second Edition
  • New insights into mechanisms of immunoregulation in 2007

    2008, Journal of Allergy and Clinical Immunology
    Citation Excerpt :

    Recently, a polymorphic variant of the IL-13 receptor (R110Q) has been shown to be associated with atopy. Expression of R110Q and low IL-13 receptor α2 levels can result in important biologic differences that might have clinical relevance in an atopic environment.61 Polymorphisms in IL13 are associated with serum total IgE levels and eosinophil counts.62

  • Advances in asthma and allergy genetics in 2007

    2008, Journal of Allergy and Clinical Immunology
    Citation Excerpt :

    Most importantly, the minor A allele at IL13+2044 (rs20541) was also strongly associated with late, but not early, wheezing, raising the possibility that early and late wheezing after RSV LRTI might be caused by distinct pathophysiologic mechanisms. The effect of IL13+2044GA (rs20541) on IL-13 function was further supported by another study showing increased activity of the IL-13 R130Q protein variant on cells expressing low IL-13 receptor α2 levels.31 Replication of results across studies remains the gold standard to assess the robustness of genetic associations.

View all citing articles on Scopus

A.-L. Andrews is an Asthma UK fellow.

Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.

View full text