Modulation of epithelial sodium channel trafficking and function by sodium 4-phenylbutyrate in human nasal epithelial cells.
Sodium 4-phenylbutyrate (4-PBA) has been shown to correct the cellular trafficking of several mutant or nonmutant plasma membrane proteins such as cystic fibrosis transmembrane conductance regulator through the expression of 70-kDa heat shock proteins. The objective of the study was to determine whether 4-PBA may influence the functional expression of epithelial sodium channels (ENaC) in human nasal epithelial cells (HNEC). Using primary cultures of HNEC, we demonstrate that 4-PBA (5 mm for 6 h) markedly stimulated amiloride-sensitive sodium channel activity and that this was related to an increased abundance of alpha-, beta-, and gamma-ENaC subunits in the apical membrane. The increase in ENaC cell surface expression (i) was due to insertion of newly ENaC subunits as determined by brefeldin A experiments and (ii) was not associated with cell surface retention of ENaC subunits because endocytosis of ENaC subunits was unchanged. In addition, we find that ENaC co-immunoprecipitated with the heat shock protein constitutively expressed Hsc70, that has been reported to modulate ENaC trafficking, and that 4-PBA decreased Hsc70 protein level. Finally, we report that in cystic fibrosis HNEC obtained from two cystic fibrosis patients, 4-PBA increased functional expression of ENaC as demonstrated by the increase in amiloride-sensitive sodium transport and in alpha-, beta-, and gamma-ENaC subunit expression in the apical membrane. Our results suggest that in HNEC, 4-PBA increases the functional expression of ENaC through the insertion of new alpha-, beta-, and gamma-ENaC subunits into the apical membrane and also suggest that 4-PBA could modify ENaC trafficking by reducing Hsc70 protein expression.
Prulière-Escabasse
Virginie
V
INSERM Unit 841, Université Paris 12, Créteil, France. virginie.pruliere@creteil.inserm.fr
Planès
Carole
C
Escudier
Estelle
E
Fanen
Pascale
P
Coste
André
A
Clerici
Christine
C
D000970:Antineoplastic Agents / Q000494:pharmacology*; D020126:Brefeldin A / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D003550:Cystic Fibrosis / Q000378:metabolism* / Q000473:pathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D005786:Gene Expression Regulation; D050883:HSC70 Heat-Shock Proteins / Q000096:biosynthesis; D006801:Humans; D009297:Nasal Mucosa / Q000378:metabolism* / Q000473:pathology; D010654:Phenylbutyrates / Q000494:pharmacology*; D021122:Protein Subunits / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D015222:Sodium Channels / Q000378:metabolism*
D000970:Antineoplastic Agents; D050883:HSC70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D010654:Phenylbutyrates; D021122:Protein Subunits; D011500:Protein Synthesis Inhibitors; D015222:Sodium Channels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D020126:Brefeldin A; C075773:4-phenylbutyric acid