Interactions among the components of the interleukin-10 receptor complex

We used fluorescence resonance energy transfer previously to show that the interferon-γ (IFN-γ) receptor complex is a preformed entity mediated by constitutive interactions between the IFN-γR2 and IFN-γR1 chains, and that this preassembled entity changes its structure after the treatment of cells with IFN-γ. We applied this technique to determine the structure of the interleukin-10 (IL-10) receptor complex and whether it undergoes a similar conformational change after treatment of cells with IL-10. We report that, like the IFN-γ receptor complex, the IL-10 receptor complex is preassembled: constitutive but weaker interactions occur between the IL-10R1 and IL-10R2 chains, and between two IL-10R2 chains. The IL-10 receptor complex undergoes no major conformational changes when cells are treated with cellular or Epstein–Barr viral IL-10. Receptor complex preassembly may be an inherent feature of Class 2 cytokine receptor complexes.