IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Substrate recognition by ER chaperones in vivo is determined by their conformational status
Autor/es:
LABRIOLA, C.A.; STIGLIANO, I.D.; VILLAMIL GIRALDO, A.; D'ALESSIO, C.; PARODI, A.J.; CARAMELO, JJ
Lugar:
Tucumán, Argentina
Reunión:
Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009
Institución organizadora:
Sociedad Argentina de Investigación en Bioquímica y Biología Molecular
Resumen:
Protein folding in the cell is a complex process highly prone to fall into irreversible errors. After their synthesis, proteins adopt diverse structural intermediates before attaining their native conformation. Several chaperones and folding assisting enzymes are in place to increase the efficiency of this process. Although we know the structural determinants recognized by many chaperones in cell free systems, the conformational pattern recognized in vivo remains mostly unknown. The most abundant chaperones in the endoplasmic reticulum of T. cruzi are BiP (homologue of HSP70), and calreticulin (CRT, a lectin-chaperone central in the glycoprotein folding quality control system). Here we show that in vivo these chaperones display a sharp difference regarding the folding status of their substrates. As a model substrate we employed cruzipaine, an abundant lysosome protease, and we followed its maturation in vivo and its association with different chaperones by using a combination of thiol group modification and co-immunoprecipitation. We found that BiP binds cruzipaine during its firsts folding stages, when the protein adopts an expanded conformation, while CRT binding occurs during more advanced stages, when the protein adopts a compact conformation. This sequential action of chaperone and their different specificity ensures the optimal assistance all along the protein folding pathway. In addition, a parasite in which the access to CRT has been abolished displays a much more lasting BiP association, illustrating the competition and cooperation between both folding systems.