Involvement of endoplasmic reticulum chaperones in the folding of hepatitis C virus glycoproteins.
The hepatitis C virus (HCV) genome encodes two envelope glycoproteins (E1 and E2) which interact noncovalently to form a heterodimer (E1-E2). During the folding and assembly of HCV glycoproteins, a large portion of these proteins are trapped in aggregates, reducing the efficiency of native E1-E2 complex assembly. To better understand this phenomenon and to try to increase the efficiency of HCV glycoprotein folding, endoplasmic reticulum chaperones potentially interacting with these proteins were studied. Calnexin, calreticulin, and BiP were shown to interact with E1 and E2, whereas no interaction was detected between GRP94 and HCV glycoproteins. The association of HCV glycoproteins with calnexin and calreticulin was faster than with BiP, and the kinetics of interaction with calnexin and calreticulin were very similar. However, calreticulin and BiP interacted preferentially with aggregates whereas calnexin preferentially associated with monomeric forms of HCV glycoproteins or noncovalent complexes. Tunicamycin treatment inhibited the binding of HCV glycoproteins to calnexin and calreticulin, indicating the importance of N-linked oligosaccharides for these interactions. The effect of the co-overexpression of each chaperone on the folding of HCV glycoproteins was also analyzed. However, the levels of native E1-E2 complexes were not increased. Together, our data suggest that calnexin plays a role in the productive folding of HCV glycoproteins whereas calreticulin and BiP are probably involved in a nonproductive pathway of folding.
Choukhi
A
A
Equipe Hépatite C, CNRS-UMR 319, Institut de Biologie de Lille et Institut Pasteur de Lille, France.
Ung
S
S
Wychowski
C
C
Dubuisson
J
J
D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D037281:Calnexin; D037282:Calreticulin; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007212:Indolizines / Q000494:pharmacology; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014415:Tunicamycin / Q000494:pharmacology; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*; D054836:Indolizidines
D002135:Calcium-Binding Proteins; D037281:Calnexin; D037282:Calreticulin; D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007212:Indolizines; D008565:Membrane Proteins; D018832:Molecular Chaperones; D012261:Ribonucleoproteins; D014415:Tunicamycin; D014759:Viral Envelope Proteins; C087035:E1 protein, Hepatitis C virus; C018551:glucose-regulated proteins; C091015:glycoprotein E2, Hepatitis C virus; C037806:castanospermine; D054836:Indolizidines