Sodium homeostasis in terrestrial and freshwater vertebrates is controlled by the corticosteroid hormones, principally aldosterone, which stimulate electrogenic Na + absorption tight epithelia. Although aldosterone known to increase apical membrane permeability target cells through changes gene transcription, mechanistic basis of this effect remains poorly understood. The predominant early activity epithelial sodium channel (ENaC), although ENaC mRNA protein levels do not change initially....

Mineralocorticoid and glucocorticoid hormones elicit distinct physiologic responses, yet the mineralocorticoid receptor (MR) (GR) bind to activate transcription similarly from a consensus simple hormone response element (HRE). The activities of GR MR at plfG, 25-base pair composite which both steroid receptors factor AP1 can bind, are analyzed here. Under conditions in represses AP1-stimulated was inactive. With use MR-GR chimeras, segment NH2-terminal region (amino acids 105 440) shown be...

Aldosterone controls sodium reabsorption and potassium secretion in the aldosterone-sensitive distal nephron (ASDN). Although clearance measurements have shown that aldosterone induces these transports within 30–60 min, no early effects been demonstrated vivo at level of apical epithelial channel (ENaC), main effector this regulation. Here we show by real-time RT-PCR immunofluorescence an injection adrenalectomized rats α-ENaC subunit expression along entire ASDN 2 h, whereas β- γ-ENaC are...

Corticosteroid hormones, including the mineralocorticoids and glucocorticoids, regulate diverse physiological functions in vertebrates. These hormones act through two classes of corticosteroid receptors (CR) that are ligand-dependent transcription factors: type I or mineralocorticoid receptor (MR) II glucocorticoid (GR). There is substantial overlap binding these types to DNA. In fish, processes controlled by CRs may be different from other vertebrates, as fish thought synthesize only...

Results on the subcellular localization of mineralocorticoid receptor (MR) have been controversial. To determine distribution and trafficking MR in living cells after binding agonists antagonists, we expressed a MR-green fluorescent protein (GFP) chimera mammalian lacking endogenous MR. The GFP-tagged (GFP-MR) remained transcriptionally active, as determined cotransfection experiments with MR-responsive reporter, TAT3-LUC. GFP-MR was monitored by fluorescence time-lapse microscopy. In...

The mineralocorticoid and glucocorticoid receptors (MR GR, respectively) are members of the intracellular receptor superfamily that bind as homodimers to same hormone response elements (HREs). Physiological evidence suggests MR GR interact with each other in cells express both receptors, implying they might directly regulation transcription initiation. Indeed, we have found coexpressed functionally at transcriptional level furthermore physically through heterodimer formation a shared HRE...

DNA regulatory elements frequently harbor multiple recognition sites for several transcriptional activators. The response mounted from such compound is often more pronounced than the simple sum of effects observed at single binding sites. determinants synergy and its control, however, are poorly understood. Through a genetic approach, we have uncovered novel protein motif that limits DNA-binding regulators. Disruption these conserved control motifs (SC motifs) selectively increases activity...

The epithelial Na + channel (ENaC) constitutes the rate-limiting step for transport across tight epithelia and is principal target of hormonal regulation, particularly by insulin mineralocorticoids. Recently, serine-threonine kinase (SGK) was identified as a rapidly mineralocorticoid-responsive gene, product which stimulates ENaC-mediated transport. Like its close relative, protein B (also called Akt), SGK's activity dependent on phosphatidylinositol 3-kinase (PI3K), key mediator signaling....

The target of rapamycin (TOR) kinase coordinately regulates fundamental metabolic and cellular processes to support growth, proliferation, survival, differentiation, consequently it has been proposed as a therapeutic for the treatment cancer, disease, aging. TOR is found in two biochemically functionally distinct complexes, termed TORC1 TORC2. Aided by compound rapamycin, which specifically inhibits TORC1, role regulating translation growth extensively studied. physiological roles TORC2 have...

The androgen and glucocorticoid hormones elicit divergent often opposing effects in cells, tissues, animals. A wide range of physiological molecular biological evidence suggests that the receptors mediate these effects, (AR GR, respectively), influence each other's transcriptional activity. We now show coexpressed AR GR indeed do interact at level this interaction is correlated with their ability to form heterodimers a common DNA site, vitro vivo. Furthermore, mutants cannot heterodimerize...

Serum- and glucocorticoid-regulated kinase 1 (SGK1) is an aldosterone-regulated early response gene product that regulates the activity of several ion transport proteins, most notably epithelial sodium channel (ENaC). Recent evidence has established SGK1 phosphorylates inhibits Nedd4-2 (neural precursor cell-expressed, developmentally down-regulated protein 4-2), a ubiquitin ligase decreases cell surface expression possibly stimulates its degradation. The mechanistic basis for this...

The steroid hormone aldosterone stimulates sodium (Na+) transport in tight epithelia by altering the expression of target genes that regulate activity and trafficking epithelial channel (ENaC). We performed microarray analysis to identify aldosterone-regulated transcripts mammalian kidney cells (mpkC-CD(c14)). One target, glucocorticoid-induced leucine zipper protein (GILZ), was previously identified serial gene (SAGE); however, its function ion unknown. Here we show GILZ is rapidly...

Abstract Aldosterone plays a major role in regulating sodium and potassium flux epithelial tissues such as kidney colon. Recent evidence suggests that serum- glucocorticoid-regulated kinase (SGK) is induced by aldosterone acts key mediator of action tissues. Induction SGK messenger RNA (mRNA) has previously been shown within 30 min addition supraphysiological doses to Xenopus A6 cells 4 h rat vivo. In this study we determined the time course induction, at physiological range, colon, using...

We recently found that the metabolic sensor AMP-activated kinase (AMPK) inhibits epithelial Na+ channel (ENaC) through decreased plasma membrane ENaC expression, an effect requiring presence of a binding motif in cytoplasmic tail beta-ENaC subunit for ubiquitin ligase Nedd4-2. To further examine role Nedd4-2 regulation by AMPK, we studied effects AMPK activation on currents Xenopus oocytes co-expressing and wild-type (WT) or mutant forms inhibition was preserved expressing WT but blocked...

ABSTRACT. Mineralocorticoids stimulate Na+ reabsorption and K+ secretion in principal cells of connecting tubule collecting duct. The involved ion channels are ENaC ROMK1, respectively. In Xenopus oocytes, the serum glucocorticoid-sensitive kinase SGK1 has been shown to increase activity by enhancing its abundance plasma membrane. With same method, ROMK1 appeared be insensitive regulation SGK1. On other hand, colocalize with NHERF2, a protein mediating targeting trafficking transport...

The serum- and glucocorticoid-induced kinase 1 (SGK1) plays a central role in hormone regulation of epithelial sodium (Na+) channel (ENaC)-dependent Na+ transport the distal nephron. Phosphorylation within carboxy-terminal domain, designated hydrophobic motif (HM), determines activity SGK1, but identity HM is unknown. Here, we show that highly conserved serine-threonine mammalian target rapamycin (mTOR) essential for phosphorylation SGK1 activation ENaC. We observed mTOR, conjunction with...

Hormonal control of transepithelial sodium (Na + ) transport utilizes phosphatidylinositide 3′-kinase (PI3K) and Raf–MAPK/ERK kinase (MEK)–ERK-dependent signaling pathways, which impact numerous cell functions. How signals transmitted by these pathways are sorted appropriately to alter Na without altering other physiologic processes is not well understood. Here, we report the identification a complex that selectively modulates surface expression epithelial channel (ENaC), an ion essential...

The epithelial Na+ channel (ENaC) is essential for homeostasis, and dysregulation of this underlies many forms hypertension. Recent studies suggest that mTOR regulates phosphorylation activation serum/glucocorticoid regulated kinase 1 (SGK1), which known to inhibit ENaC internalization degradation; however, it not clear whether contributes the regulation renal tubule ion transport. Here, we evaluated effect selective inhibitors on kidney K+ transport in WT Sgk1–/– mice, as well isolated...

Potassium (K+) secretion by kidney tubule cells is central to electrolyte homeostasis in mammals. In the K+-secreting principal of distal nephron, electrogenic Na+ transport epithelial sodium channel (ENaC) generates electrical driving force for K+ across apical membrane. Regulation this process attributable part aldosterone, which stimulates gene transcription ENaC-regulatory kinase, SGK1. However, a wide range evidence supports conclusion that an unidentified aldosterone-independent...

Significance Statement Rapid renal responses to ingested potassium are essential prevent hyperkalemia and also play a central role in blood pressure regulation. Although local extracellular K + concentration kidney tissue is increasingly recognized as an important regulator of secretion, the underlying mechanisms that relevant vivo remain controversial. To assess signaling kinase mTOR complex-2 (mTORC2), authors compared effects administered by gavage wild-type mice knockout with...