INVESTIGADORES
D'ALESSIO Cecilia
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.