Regulation of human cystic fibrosis transmembrane conductance regulator (CFTR) by serum- and glucocorticoid-inducible kinase (SGK1).
BACKGROUND
Serum- and glucocorticoid-inducible kinase-1 (SGK1) increases CFTR Cl currents in Xenopus oocytes by an unknown mechanism. Because SGK increases the plasma membrane expression of other ion channels, the goal of this paper was to test the hypothesis that SGK1 stimulates CFTR Cl currents by increasing the number of CFTR Cl channels in the plasma membrane.


METHODS
CFTR Cl currents were measured in Xenopus oocytes by the two-electrode voltage clamp technique, and CFTR in the plasma membrane was determined by laser scanning confocal microscopy.


RESULTS
wt-SGK1 stimulated CFTR Cl currents by 42% and increased the amount of CFTR in the plasma membrane by 35%. A kinase-dead SGK mutant (K127N) had a dominant-negative effect on CFTR, reducing CFTR Cl currents by 38%. In addition, deletion of the C-terminal PDZ-interacting motif (SGK1-DeltaSFL) increased CFTR Cl currents by 108%. Thus, SGK1-DeltaSFL was more effective than wt-SGK1 in stimulating CFTR Cl currents. Neither wt-SGK nor the K127N mutant had any effect on Cl currents in oocytes when expressed alone in the absence of CFTR.


CONCLUSIONS
SGK1 stimulates CFTR Cl currents in Xenopus oocytes by increasing the number of channels in the plasma membrane. Moreover, the effect of SGK may be mediated by protein-protein interactions involving the PDZ interacting motif.
Sato
J Denry
JD
Mount Desert Island Biological Laboratory, Salisbury Cove, USA.
Chapline
M Christine
MC
Thibodeau
Renee
R
Frizzell
Raymond A
RA
Stanton
Bruce A
BA
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D005260:Female; D023781:Fundulidae / Q000235:genetics; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014981:Xenopus; D000099184:Serum-Glucocorticoid Regulated Kinases
D015056:1-Methyl-3-isobutylxanthine; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D017874:Immediate-Early Proteins; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins; D000099184:Serum-Glucocorticoid Regulated Kinases; C505032:CFTR protein, human