C1q protein binds to the apoptotic nucleolus and causes C1 protease degradation of nucleolar proteins.
J Biol Chem
; 290(37): 22570-80, 2015 Sep 11.
Article
en En
| MEDLINE
| ID: mdl-26231209
In infection, complement C1q recognizes pathogen-congregated antibodies and elicits complement activation. Among endogenous ligands, C1q binds to DNA and apoptotic cells, but whether C1q binds to nuclear DNA in apoptotic cells remains to be investigated. With UV irradiation-induced apoptosis, C1q initially bound to peripheral cellular regions in early apoptotic cells. By 6 h, binding concentrated in the nuclei to the nucleolus but not the chromatins. When nucleoli were isolated from non-apoptotic cells, C1q also bound to these structures. In vivo, C1q exists as the C1 complex (C1qC1r2C1s2), and C1q binding to ligands activates the C1r/C1s proteases. Incubation of nucleoli with C1 caused degradation of the nucleolar proteins nucleolin and nucleophosmin 1. This was inhibited by the C1 inhibitor. The nucleoli are abundant with autoantigens. C1q binding and C1r/C1s degradation of nucleolar antigens during cell apoptosis potentially reduces autoimmunity. These findings help us to understand why genetic C1q and C1r/C1s deficiencies cause systemic lupus erythematosus.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Fosfoproteínas
/
Rayos Ultravioleta
/
Proteínas Nucleares
/
Complemento C1q
/
Complemento C1r
/
Nucléolo Celular
/
Complemento C1s
/
Proteínas de Unión al ARN
/
Apoptosis
/
Proteolisis
Tipo de estudio:
Etiology_studies
Límite:
Humans
Idioma:
En
Revista:
J Biol Chem
Año:
2015
Tipo del documento:
Article
Pais de publicación:
Estados Unidos