LEFTYA Activates the Epithelial Na+ Channel (ENaC) in Endometrial Cells via Serum and Glucocorticoid Inducible Kinase SGK1

Abstract

Background: Serum & 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.

Environmentally relevant levels of bisphenol A affect uterine decidualization and embryo implantation through the estrogen receptor/serum and glucocorticoid-regulated kinase 1/epithelial sodium ion channel α-subunit pathway in a mouse model

“…The epithelial sodium channel (ENaC) is required for uterine decidualization and embryo implantation (35). Serum and glucocorticoid-induced kinase-1 (SGK1) is a potent regulator of ENaC (37)(38)(39), and can up-regulate ENaC and increase ENaC membrane abundance (40) and activity (41,42). It was reported that 17b-estradiol could stimulate SGK1 mRNA and protein expression through ERb (estrogen receptor b) in the endometrial tissues of endometriosis patients (43).…”

Downregulation of endometrial mesenchymal marker SUSD2 causes cell senescence and cell death in endometrial carcinoma cells

“…Detection of gene expression was performed with KapaFast-SYBRGreen (#KAPBKK4606, Peqlab VWR, Germany) and quantitative RT-PCR was performed on a BioRad iCycler iQ ™ Real-Time PCR Detection System (Bio-Rad Laboratories, Germany) as described earlier [ 30 ]. The expression levels of the samples were calculated by the 2 -ΔΔ Ct method using L19 to normalize for variances in input cDNA and expressed as arbitrary units.…”

Serum and Glucocorticoid Inducible Kinase 1-Sensitive Survival, Proliferation and Migration of Rhabdomyosarcoma Cells

“…The RMS cell lines were treated with the SGK1 inhibitor EMD638683 (APExBIO, Houston, Texas, USA, IC50 3µM) in the absence and presence of doxorubicin for the indicated periods and with the indicated concentrations. The concentration of EMD638683 has previously been shown to be effective [20, 33, 34]. …”