Rho-family GTPases require the Arp2/3 complex to stimulate actin polymerization in Acanthamoeba extracts.
Curr Biol
; 9(8): 405-15, 1999 Apr 22.
Article
en En
| MEDLINE
| ID: mdl-10226024
BACKGROUND: Actin filaments polymerize in vivo primarily from their fast-growing barbed ends. In cells and extracts, GTPgammaS and Rho-family GTPases, including Cdc42, stimulate barbed-end actin polymerization; however, the mechanism responsible for the initiation of polymerization is unknown. There are three formal possibilities for how free barbed ends may be generated in response to cellular signals: uncapping of existing filaments; severing of existing filaments; or de novo nucleation. The Arp2/3 complex localizes to regions of dynamic actin polymerization, including the leading edges of motile cells and motile actin patches in yeast, and in vitro it nucleates the formation of actin filaments with free barbed ends. Here, we investigated actin polymerization in soluble extracts of Acanthamoeba. RESULTS: Addition of actin filaments with free barbed ends to Acanthamoeba extracts is sufficient to induce polymerization of endogenous actin. Addition of activated Cdc42 or activation of Rho-family GTPases in these extracts by the non-hydrolyzable GTP analog GTPgammaS stimulated barbed-end polymerization, whereas immunodepletion of Arp2 or sequestration of Arp2 using solution-binding antibodies blocked Rho-family GTPase-induced actin polymerization. CONCLUSIONS: For this system, we conclude that the accessibility of free barbed ends regulates actin polymerization, that Rho-family GTPases stimulate polymerization catalytically by de novo nucleation of free barbed ends and that the primary nucleation factor in this pathway is the Arp2/3 complex.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Acanthamoeba
/
Actinas
/
Proteínas del Citoesqueleto
/
GTP Fosfohidrolasas
Límite:
Animals
Idioma:
En
Revista:
Curr Biol
Asunto de la revista:
BIOLOGIA
Año:
1999
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Reino Unido