Accelerated disassembly of IgE-receptor complexes by a disruptive macromolecular inhibitor.
Nature
; 491(7425): 613-7, 2012 Nov 22.
Article
em En
| MEDLINE
| ID: mdl-23103871
ABSTRACT
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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas Recombinantes de Fusão
/
Imunoglobulina E
/
Receptores de IgE
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article