Endoplasmic reticulum-associated degradation of mutant CFTR requires a guanine nucleotide-sensitive step.
Proteasome degradation of endoplasmic reticulum (ER)-misfolded proteins requires retrograde transport from ER to the cytosol. To date, it is not clear whether this event constitutes the exclusive ER degradation process for non-native membrane proteins. Here we describe the role of GTP in the degradation of DeltaF508-CFTR and the alpha subunit of the T-cell receptor (TCRalpha), representative misfolded ER membrane proteins. Selective intracellular GTP depletion extended the DeltaF508-CFTR half-life sixfold, whereas ATP depletion accelerated its turnover and inhibited only 80% of the proteasome activity that was not affected by GTP depletion. AlF(4)(-), a well-known inhibitor of heterotrimeric G proteins, but not of AlF(3), delayed the mutant CFTR turnover in vivo, in semi-intact cells and in ER-enriched microsomes, without affecting ER to Golgi cargo transport. DeltaF508-CFTR degradation was also inhibited by alkaline stripping of ER-associated membrane proteins. We propose that at the ER, GTP may participate in the disposal of misfolded membrane proteins through activation of heterotrimeric G proteins.
De Keukeleire
Béatrice
B
CNRS, UMR 5249, 17 Rue des Martyrs, Grenoble F-38054, France.
Micoud
Julien
J
Biard
Julie
J
Benharouga
Mohamed
M
D000255:Adenosine Triphosphate / Q000378:metabolism; D017607:Aluminum Compounds / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics* / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005459:Fluorides / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000378:metabolism; D012680:Sensitivity and Specificity
D017607:Aluminum Compounds; D016693:Receptors, Antigen, T-Cell, alpha-beta; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C050992:tetrafluoroaluminate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D046988:Proteasome Endopeptidase Complex; D005459:Fluorides