LEFTYA Activates the Epithelial Na+ Channel (ENaC) in Endometrial Cells via Serum and Glucocorticoid Inducible Kinase SGK1.
BACKGROUND
Serum &amp; glucocorticoid inducible kinase (SGK1) regulates several ion channels, including amiloride sensitive epithelial Na+ channel (ENaC). SGK1 and ENaC in the luminal endometrium epithelium, are critically involved in embryo implantation, although little is known about their regulation. The present study explored whether SGK1 and ENaC are modulated by LEFTYA, a negative regulator of uterine receptivity.


METHODS
Expression levels were determined by qRT-PCR and Western blotting, ENaC channel activity by whole cell patch clamp and transepithelial current by Ussing chamber experiments.


RESULTS
Treatment of Ishikawa cells, an endometrial adenocarcinoma model cell line of endometrial epithelial cells, with LEFTYA rapidly up-regulated SGK1 and ENaC transcript and protein levels. Induction of ENaC in response to LEFTYA was blunted upon co-treatment with the SGK1 inhibitor EMD638683. ENaC levels also significantly upregulated upon expression of a constitutively active, but not a kinase dead, SGK1 mutant in Ishikawa cells. LEFTYA increased amiloride sensitive Na+-currents in Ishikawa cells and amiloride sensitive transepithelial current across the murine endometrium. Furthermore, LEFTYA induced the expression of ENaC in the endometrium of wild-type but not of Sgk1-deficient mice.


CONCLUSIONS
LEFTYA regulates the expression and activity of ENaC in endometrial epithelial cells via SGK1. Aberrant regulation of SGK1 and ENaC by LEFTYA could contribute to the pathogenesis of unexplained infertility.
Department of Cardiology, Vascular Medicine and Physiology I, University of Tuebingen, Tuebigen, Germany.
Madhuri S
MS
Salker
Zohreh
Z
Hosseinzadeh
Nour
N
Alowayed
Ni
N
Zeng
Anja T
AT
Umbach
Zoe
Z
Webster
Yogesh
Y
Singh
Jan J
JJ
Brosens
Florian
F
Lang
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D045744:Cell Line, Tumor; D015194:Diffusion Chambers, Culture; D004717:Endometrium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D053503:Epithelial Sodium Channels / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D017874:Immediate-Early Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics*; D055458:Left-Right Determination Factors / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques; D061251:Primary Cell Culture; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D000099184:Serum-Glucocorticoid Regulated Kinases
D000584:Amiloride; D001549:Benzamides; D053503:Epithelial Sodium Channels; D006834:Hydrazines; D017874:Immediate-Early Proteins; D055458:Left-Right Determination Factors; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D000099184:Serum-Glucocorticoid Regulated Kinases; C569030:EMD 638683; C526162:Lefty2 protein, mouse