Abstract
The cytokine interleukin (IL)-21 exerts pleiotropic effects acting through innate as well as adaptive immune responses. The activities of IL-21 are mediated through binding to its cognate receptor complex composed of the IL-21 receptor private chain (IL-21Ralpha) and the common gamma-chain (gammaC), the latter being shared by IL-2, IL-4, IL-7, IL-9, and IL-15. The binding energy of the IL-21 ternary complex is predominantly provided by the high affinity interaction between IL-21 and IL-21Ralpha, whereas the interaction between IL-21 and gammaC, albeit essential for signaling, is rather weak. The design of IL-21 analogues, which have lost most or all affinity toward the signaling gammaC chain, while simultaneously maintaining a tight interaction with the private chain, would in theory represent candidates for IL-21 antagonists. We predicted the IL-21 residues, which compose the gammaC binding epitope using homology modeling and alignment with the related cytokines, IL-2 and IL-4. Next we systematically analyzed the predicted binding epitope by a mutagenesis study. Indeed two mutants, which have significantly impaired gammaC affinity with undiminished IL-21Ralpha affinity, were successfully identified. Functional studies confirmed that these two novel hIL-21 double mutants do act as hIL-21 antagonists.
Original language | English |
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Journal | Journal of Biological Chemistry |
Volume | 285 |
Issue | 16 |
Pages (from-to) | 12223-31 |
Number of pages | 9 |
ISSN | 0021-9258 |
DOIs | |
Publication status | Published - 16 Apr 2010 |
Keywords
- Amino Acid Sequence
- Amino Acid Substitution
- Binding Sites
- Cell Line
- Drug Design
- Epitopes
- Humans
- Interleukin-2
- Interleukin-4
- Interleukins
- Models, Molecular
- Molecular Sequence Data
- Multiprotein Complexes
- Mutagenesis, Site-Directed
- Protein Interaction Domains and Motifs
- Receptors, Interleukin-21
- Recombinant Proteins
- Sequence Homology, Amino Acid
- Structural Homology, Protein