Misfolding diverts CFTR from recycling to degradation: quality control at early endosomes.
To investigate the degradation mechanism of misfolded membrane proteins from the cell surface, we used mutant cystic fibrosis transmembrane conductance regulators (CFTRs) exhibiting conformational defects in post-Golgi compartments. Here, we show that the folding state of CFTR determines the post-endocytic trafficking of the channel. Although native CFTR recycled from early endosomes back to the cell surface, misfolding prevented recycling and facilitated lysosomal targeting by promoting the ubiquitination of the channel. Rescuing the folding defect or down-regulating the E1 ubiquitin (Ub)-activating enzyme stabilized the mutant CFTR without interfering with its internalization. These observations with the preferential association of mutant CFTRs with Hrs, STAM-2, TSG101, hVps25, and hVps32, components of the Ub-dependent endosomal sorting machinery, establish a functional link between Ub modification and lysosomal degradation of misfolded CFTR from the cell surface. Our data provide evidence for a novel cellular mechanism of CF pathogenesis and suggest a paradigm for the quality control of plasma membrane proteins involving the coordinated function of ubiquitination and the Ub-dependent endosomal sorting machinery.
Hospital for Sick Children, Program in Cell and Lung Biology, 555 University Ave., Toronto, Ontario M5G 1X8, Canada.
Manu
M
Sharma
Francesca
F
Pampinella
Csilla
C
Nemes
Mohamed
M
Benharouga
Jeffrey
J
So
Kai
K
Du
Kristi G
KG
Bache
Blake
B
Papsin
Noa
N
Zerangue
Harald
H
Stenmark
Gergely L
GL
Lukacs
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D021381:Protein Transport / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism
C505032:CFTR protein, human; D011993:Recombinant Fusion Proteins; D014452:Ubiquitins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator