Divalent cations differentially regulate integrin alphaIIb cytoplasmic tail binding to beta3 and to calcium- and integrin-binding protein.
J Biol Chem
; 274(24): 17257-66, 1999 Jun 11.
Article
en En
| MEDLINE
| ID: mdl-10358085
We have used recombinant or synthetic alphaIIb and beta3 integrin cytoplasmic peptides to study their in vitro complexation and ligand binding capacity by surface plasmon resonance. alpha.beta heterodimerization occurred in a 1:1 stoichiometry with a weak KD in the micromolar range. Divalent cations were not required for this association but stabilized the alpha.beta complex by decreasing the dissociation rate. alpha.beta complexation was impaired by the R995A substitution or the KVGFFKR deletion in alphaIIb but not by the beta3 S752P mutation. Recombinant calcium- and integrin-binding protein (CIB), an alphaIIb-specific ligand, bound to the alphaIIb cytoplasmic peptide in a Ca2+- or Mn2+-independent, one-to-one reaction with a KD value of 12 microM. In contrast, in vitro liquid phase binding of CIB to intact alphaIIbbeta3 occurred preferentially with Mn2+-activated alphaIIbbeta3 conformers, as demonstrated by enhanced coimmunoprecipitation of CIB with PAC-1-captured Mn2+-activated alphaIIbbeta3, suggesting that Mn2+ activation of intact alphaIIbbeta3 induces the exposure of a CIB-binding site, spontaneously exposed by the free alphaIIb peptide. Since CIB did not stimulate PAC-1 binding to inactive alphaIIbbeta3 nor prevented activated alphaIIbbeta3 occupancy by PAC-1, we conclude that CIB does not regulate alphaIIbbeta3 inside-out signaling, but rather is involved in an alphaIIbbeta3 post-receptor occupancy event.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Proteínas de Unión al Calcio
/
Glicoproteínas de Membrana Plaquetaria
/
Proteínas Portadoras
/
Antígenos CD
/
Complejo GPIIb-IIIa de Glicoproteína Plaquetaria
Límite:
Humans
Idioma:
En
Revista:
J Biol Chem
Año:
1999
Tipo del documento:
Article
Pais de publicación:
Estados Unidos