title: The human DnaJ homologue (Hdj)-1/heat-shock protein (Hsp) 40 co-chaperone is required for the in vivo stabilization of the cystic fibrosis transmembrane conductance regulator by Hsp70.
abstract: The CFTR (cystic fibrosis transmembrane conductance regulator) gene, defective in cystic fibrosis, codes for a polytopic apical membrane protein functioning as a chloride channel. Wild-type (wt) CFTR matures inefficiently and CFTR with a deletion of Phe-508 (F508del), the most frequent mutation, is substantially retained as a core-glycosylated intermediate in the endoplasmic reticulum (ER), probably due to misfolding that is recognized by the cellular quality control machinery involving molecular chaperones. Here, we overexpressed the heat-shock protein (Hsp) 70 chaperone in vivo and observed no changes in degradation rate of the core-glycosylated form, nor in the efficiency of its conversion into the fully glycosylated form, for either wt- or F508del-CFTR, contrary to previous in vitro studies on the affect of heat-shock cognate (Hsc) 70 on part of the first nucleotide-binding domain of CFTR. Co-transfection of Hsp70 with its co-chaperone human DnaJ homologue (Hdj)-1/Hsp40, however, stabilizes the immature form of wt-CFTR, but not of F508del-CFTR, suggesting that these chaperones act on a wt-specific conformation. As the efficiency of conversion into the fully glycosylated form is not increased under Hsp70/Hdj-1 overexpression, the lack of these two chaperones does not seem to be critical for CFTR maturation and ER retention. The effects of 4-phenylbutyrate and deoxyspergualin, described previously to interfere with Hsp70 binding, were also tested upon CFTR degradation and processing. The sole effect observed was destabilization of F508del-CFTR.
authors.affiliation: Centro de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Av. Padre Cruz, 1649-016 Lisboa, Portugal.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Farinha
authors.forename: Paulo
authors.initials: P
authors.lastname: Nogueira
authors.forename: Filipa
authors.initials: F
authors.lastname: Mendes
authors.forename: Deborah
authors.initials: D
authors.lastname: Penque
authors.forename: Margarida D
authors.initials: MD
authors.lastname: Amaral
mesh_terms: D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D003720:Densitometry; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006031:Glycosylation; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D018832:Molecular Chaperones / Q000378:metabolism; D009154:Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D017510:Protein Folding; D013997:Time Factors; D014162:Transfection
chemical_list: C505032:CFTR protein, human; D018076:DNA, Complementary; C494647:DNAJB1 protein, human; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D019005:Cystic Fibrosis Transmembrane Conductance Regulator