Kinetic Analysis of the Interleukin-13 Receptor Complex

Abstract

Interleukin (IL)-13 is a key cytokine associated with the asthmatic phenotype. It signals via its cognate receptor, a complex of IL-13 receptor ␣1 chain (IL-13R␣1) with IL-4R␣; however, a second protein, IL-13R␣2, also binds IL-13. To determine the binding contributions of the individual components of the IL-13 receptor to IL-13, we have employed surface plasmon resonance and equilibrium binding assays to investigate the ligand binding characteristics of shIL-13R␣1, shIL-13R␣2, and IL-4R␣. shIL-13R␣1 bound IL-13 with moderate affinity (K D ‫؍‬ 37.8 ؎ 1.8 nM, n ‫؍‬ 10), whereas no binding was observed for hIL-4R␣. In contrast, shIL-13R␣2 produced a high affinity interaction with IL-13 (K D ‫؍‬ 2.49 ؎ 0.94 nM n ‫؍‬ 10). IL-13R␣2 exhibited the binding characteristics of a negative regulator with a fast association rate and an exceptional slow dissociation rate. Although IL-13 interacted weakly with IL-4R␣ on its own (K D > 50 M), the presence of hIL-4R␣ significantly increased the affinity of shIL-13R␣1 for IL-13 but had no effect on the binding affinity of IL-13R␣2. Detailed kinetic analyses of the binding properties of the heteromeric complexes suggested a sequential mechanism for the binding of IL-13 to its signaling receptor, in which IL-13 first binds to IL-13R␣1 and this then recruits IL-4R␣ to stabilize a high affinity interaction.

Distinct Structural Requirements for Interleukin-4 (IL-4) and IL-13 Binding to the Shared IL-13 Receptor Facilitate Cellular Tuning of Cytokine Responsiveness

“…IL-4 first binds to IL-4R␣ with high affinity (K d ϭ 1 nM), followed by recruitment of IL-13R␣1 with low affinity. In contrast, IL-13 first binds to IL-13R␣1 with low affinity (K d ϭ 30 -37 nM), and then the complex recruits IL-4R␣, forming a high affinity receptor (K d ϭ 0.03-0.4 nM (6,7)). This means that, although both IL-4 and IL-13 use IL-4R␣ and IL-13R␣1, the roles of IL-4R␣ and IL-13R␣1 as the primary or secondary binding unit are the opposite of those for IL-4 and IL-13.…”

The association of the cytoplasmic domains of interleukin 4 receptor alpha and interleukin 13 receptor alpha 2 regulates interleukin 4 signaling

“…[13][14][15] Consistent with this, IL-13Ra2 has been shown to have the characteristics of a negative regulator, with a fast association rate but an exceptionally slow dissociation rate. 16 IL-13Ra2 has a short cytoplasmic tail that lacks any obvious signaling motif and is unable to initiate a signal through the STAT6 pathway. However it has been reported that glioblastoma cells express abnormally high levels of IL-13Ra2 that serve to inhibit IL-4 signaling and overcome IL-4 mediated growth arrest.…”

Interleukin-13 Pathway Alterations Impair Invariant Natural Killer T-Cell–Mediated Regulation of Effector T Cells in Type 1 Diabetes

“…IL-13 binds to two cell surface receptors: type 1 (IL13Ra1/IL4Ra) and type 2 (IL13Ra2). The IL13Ra1 monomer binds IL-13 before dimerizing with the IL-4Ra chain to transduce intracellular signals through STAT6 phosphorylation (24). IL13Ra2 binds IL-13 with higher affinity than IL13Ra1, but its signaling properties are less known.…”