| Autor: |
Kim B; Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA., Eggel A, Tarchevskaya SS, Vogel M, Prinz H, Jardetzky TS |
| Jazyk: |
angličtina |
| Zdroj: |
Nature [Nature] 2012 Nov 22; Vol. 491 (7425), pp. 613-7. Date of Electronic Publication: 2012 Oct 28. |
| DOI: |
10.1038/nature11546 |
| Abstrakt: |
IgE antibodies bind the high-affinity IgE Fc receptor (FcεRI), found primarily on mast cells and basophils, and trigger inflammatory cascades of the allergic response. Inhibitors of IgE-FcεRI binding have been identified and an anti-IgE therapeutic antibody (omalizumab) is used to treat severe allergic asthma. However, preformed IgE-FcεRI complexes that prime cells before allergen exposure dissociate extremely slowly and cannot be disrupted by strictly competitive inhibitors. IgE-Fc conformational flexibility indicated that inhibition could be mediated by allosteric or other non-classical mechanisms. Here we demonstrate that an engineered protein inhibitor, DARPin E2_79 (refs 9, 10, 11), acts through a non-classical inhibition mechanism, not only blocking IgE-FcεRI interactions, but actively stimulating the dissociation of preformed ligand-receptor complexes. The structure of the E2_79-IgE-Fc(3-4) complex predicts the presence of two non-equivalent E2_79 sites in the asymmetric IgE-FcεRI complex, with site 1 distant from the receptor and site 2 exhibiting partial steric overlap. Although the structure is indicative of an allosteric inhibition mechanism, mutational studies and quantitative kinetic modelling indicate that E2_79 acts through a facilitated dissociation mechanism at site 2 alone. These results demonstrate that high-affinity IgE-FcεRI complexes can be actively dissociated to block the allergic response and suggest that protein-protein complexes may be more generally amenable to active disruption by macromolecular inhibitors. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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