A phosphoinositide 3-kinase (PI3K)-serum- and glucocorticoid-inducible kinase 1 (SGK1) pathway promotes Kv7.1 channel surface expression by inhibiting Nedd4-2 protein.
Epithelial cell polarization involves several kinase signaling cascades that eventually divide the surface membrane into an apical and a basolateral part. One kinase, which is activated during the polarization process, is phosphoinositide 3-kinase (PI3K). In MDCK cells, the basolateral potassium channel Kv7.1 requires PI3K activity for surface-expression during the polarization process. Here, we demonstrate that Kv7.1 surface expression requires tonic PI3K activity as PI3K inhibition triggers endocytosis of these channels in polarized MDCK. Pharmacological inhibition of SGK1 gave similar results as PI3K inhibition, whereas overexpression of constitutively active SGK1 overruled it, suggesting that SGK1 is the primary downstream target of PI3K in this process. Furthermore, knockdown of the ubiquitin ligase Nedd4-2 overruled PI3K inhibition, whereas a Nedd4-2 interaction-deficient Kv7.1 mutant was resistant to both PI3K and SGK1 inhibition. Altogether, these data suggest that a PI3K-SGK1 pathway stabilizes Kv7.1 surface expression by inhibiting Nedd4-2-dependent endocytosis and thereby demonstrates that Nedd4-2 is a key regulator of Kv7.1 localization and turnover in epithelial cells.
From The Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark and.
Martin Nybo
MN
Andersen
Katarzyna
K
Krzystanek
Frederic
F
Petersen
Sofia Hammami
SH
Bomholtz
Søren-Peter
SP
Olesen
Hugues
H
Abriel
Thomas
T
Jespersen
Hanne Borger
HB
Rasmussen
D000818:Animals; D004285:Dogs; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051657:KCNQ1 Potassium Channel / Q000096:biosynthesis* / Q000235:genetics; D061985:Madin Darby Canine Kidney Cells; D009154:Mutation; D000075702:Nedd4 Ubiquitin Protein Ligases; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D000099184:Serum-Glucocorticoid Regulated Kinases
D056827:Endosomal Sorting Complexes Required for Transport; D004791:Enzyme Inhibitors; D017874:Immediate-Early Proteins; D051657:KCNQ1 Potassium Channel; D000075702:Nedd4 Ubiquitin Protein Ligases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D044767:Ubiquitin-Protein Ligases; D000099184:Serum-Glucocorticoid Regulated Kinases; C496909:KCNQ1 protein, human; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human
E3 Ubiquitin Ligase; Endocytosis; Ion Channels; KCNQ1; PI 3-Kinase (PI3K); Trafficking