Base treatment corrects defects due to misfolding of mutant cystic fibrosis transmembrane conductance regulator.
OBJECTIVE
The most common form of the disease-causing cystic fibrosis transmembrane conductance regulator mutation, DeltaF508, leads to a misfolded protein that undergoes endoplasmic reticulum-associated degradation. Retrieval of misfolded protein from the cis-Golgi or pre-Golgi intermediate compartment is a critical factor in endoplasmic reticulum retention and degradation of DeltaF508 protein. Therefore, the inhibition of retrograde Golgi-to-endoplasmic reticulum traffic by the alkalinization of Golgi lumen may permit functional DeltaF508 protein to reach the cell surface.


METHODS
Functional and biochemical effects of alkaline treatment on misfolded cystic fibrosis transmembrane conductance regulator-induced defects were measured in CFPAC-1 cells, which endogenously express DeltaF508 cystic fibrosis transmembrane conductance regulator, and in CHO cells, which heterologously express DeltaF508 cystic fibrosis transmembrane conductance regulator. The animal survival rate and the functional expression of cystic fibrosis transmembrane conductance regulator proteins were analyzed in homozygous DeltaF508 mice after chronic treatment with weak base NaHCO3.


RESULTS
In CFPAC-1 and CHO cells, intracellular alkalization by reducing carbon dioxide concentrations in a carbon dioxide incubation chamber or intra-Golgi alkalization by bafilomycin A1 treatment increased the membrane expression of DeltaF508 protein and cystic fibrosis transmembrane conductance regulator-dependent anion transport. Notably, chronic administration of NaHCO3 increased the long-term survival of homozygous DeltaF508 mice and induced the functional expression of cystic fibrosis transmembrane conductance regulator in the luminal membrane of intestinal epithelium.


CONCLUSIONS
We found that base treatments correct misfolded cystic fibrosis transmembrane conductance regulator-induced defects in vitro and in vivo. These results imply that the alkalization of intracellular compartments, in particular, Golgi or pre-Golgi intermediate compartments, can be a potential therapeutic target for the loss-of-function type of conformational diseases.
Namkung
Wan
W
Department of Pharmacology, Institute of Gastroenterology, and Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea.
Kim
Kyung Hwan
KH
Lee
Min Goo
MG
D015056:1-Methyl-3-isobutylxanthine / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002460:Cell Line; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000378:metabolism; D003106:Colon / Q000166:cytology / Q000378:metabolism; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004386:Duodenum / Q000166:cytology / Q000378:metabolism; D004594:Electrophysiology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000502:physiology*; D018942:Macrolides / Q000378:metabolism; D051379:Mice; D017510:Protein Folding
D001639:Bicarbonates; D018118:Chloride Channels; D002712:Chlorides; D004791:Enzyme Inhibitors; D018942:Macrolides; C057620:bafilomycin A; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine