{"gene":"SGK1","run_date":"2026-06-10T07:46:31","timeline":{"discoveries":[{"year":2001,"finding":"SGK1 phosphorylates the forkhead transcription factor FKHRL1 (FOXO3a) at Thr-32 and Ser-315, promoting FKHRL1 nuclear exit and inactivation, thereby promoting cell survival. SGK1 shows a marked preference for Ser-315 whereas Akt favors Ser-253.","method":"In vitro kinase assay, phosphosite mutagenesis, cell survival assays, nuclear translocation experiments","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay with mutagenesis of specific phosphorylation sites, multiple orthogonal methods in one study","pmids":["11154281"],"is_preprint":false},{"year":1999,"finding":"SGK1 is activated downstream of PI3-kinase via phosphorylation at Thr256 and Ser422; PDK1 directly interacts with the catalytic domain of SGK1 (GST pulldown) and phosphorylates/activates it; treatment with protein phosphatase 2A inactivates SGK1. Growth factor stimulation induces SGK1 hyperphosphorylation and nuclear translocation, both blocked by wortmannin.","method":"Peptide kinase assay, GST pulldown, phosphatase treatment, inhibitor studies (LY294002, wortmannin), co-transfection with PDK1, subcellular fractionation","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (kinase assay, pulldown, phosphatase inactivation, mutagenesis) in one study with rigorous controls","pmids":["10357815"],"is_preprint":false},{"year":1999,"finding":"Yeast Ypk1 and Ykr2 are functional counterparts of SGK; rat SGK (but not mouse PKB or rat p70 S6 kinase) rescues otherwise inviable ypk1Δ ykr2Δ yeast cells. Yeast Pkh1 (PDK1 counterpart) activates mammalian SGK by phosphorylating the same residue as PDK1, and this activation does not require phosphatidylinositol 3,4,5-trisphosphate, consistent with the absence of a pleckstrin homology domain in SGK.","method":"Genetic complementation in yeast, in vitro kinase assay with purified Pkh1 and SGK, deletion mutant rescue","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 1 / Strong — genetic complementation combined with in vitro reconstitution of kinase activation, rigorous controls","pmids":["10074427"],"is_preprint":false},{"year":2004,"finding":"SGK and PKA both phosphorylate Nedd4-2 at overlapping sites (Ser-327, Ser-221, Thr-246) to inhibit its binding to ENaC, thereby increasing ENaC surface expression and Na+ transport. SGK overexpression blunts ENaC stimulation by cAMP, and cAMP agonists decrease ENaC stimulation by SGK, indicating convergent regulation through Nedd4-2.","method":"In vitro phosphorylation assay, RNA interference, dominant-negative constructs, electrophysiology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay with site-specific mutations, RNAi, dominant-negative constructs, and functional Na+ transport readout in one study","pmids":["15328345"],"is_preprint":false},{"year":2001,"finding":"SGK1 phosphorylates and negatively regulates B-Raf kinase activity by phosphorylating a single Akt consensus site, Ser364, in B-Raf's amino-terminal regulatory domain. SGK displays stronger inhibitory effect on B-Raf than Akt, and enhanced association between SGK and B-Raf (vs. Akt preference for FKHR) explains the selective substrate specificity.","method":"In vitro kinase assay, co-immunoprecipitation, phosphosite mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with defined phosphosite, co-IP for substrate association, single laboratory","pmids":["11410590"],"is_preprint":false},{"year":2002,"finding":"SGK1 steady-state protein levels are kept low by polyubiquitination and subsequent degradation by the 26S proteasome. Deletion of the N-terminal 60 amino acids prevents polyubiquitination and proteasomal degradation. A fraction of SGK1 localizes to the plasma membrane and the polyubiquitin-modified form is enriched in the membrane-associated fraction.","method":"Ubiquitination assays, proteasome inhibitor treatment, truncation mutants, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct ubiquitination assay with deletion mutants and proteasome inhibitor, multiple orthogonal approaches, single laboratory","pmids":["12218062"],"is_preprint":false},{"year":2004,"finding":"Nedd4-2 mediates ubiquitin-dependent degradation of SGK1 in a feedback loop: SGK1 phosphorylates Nedd4-2, and this phosphorylation increases Nedd4-2-mediated ubiquitination and proteasomal degradation of SGK. Nedd4-2 overexpression decreases SGK steady-state levels, and Nedd4-2 knockdown by RNAi stabilizes SGK.","method":"Co-expression ubiquitination assays, RNA interference, SGK half-life measurement, mutants blocking phosphorylation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ubiquitination assay, RNAi knockdown, phosphorylation site mutants, multiple orthogonal methods, single laboratory","pmids":["15576372"],"is_preprint":false},{"year":2006,"finding":"The E3 ubiquitin ligase CHIP forms a complex with SGK-1, mediates its ubiquitin modification and rapid proteasomal degradation, and co-localizes with SGK-1 at or near the endoplasmic reticulum. CHIP-mediated regulation of SGK-1 levels alters its kinase activity.","method":"Co-immunoprecipitation, ubiquitination assay, immunofluorescence co-localization","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assay, and localization data, single laboratory","pmids":["16895519"],"is_preprint":false},{"year":2005,"finding":"WNK1 activates SGK1 through a PI3K-dependent but non-catalytic mechanism; neither WNK1 kinase activity nor its kinase domain is required—rather the N-terminal 220 residues of WNK1 are necessary and sufficient for SGK1 activation. WNK1 phosphorylation at Thr-58 contributes to SGK1 activation. WNK1 is required for IGF-1-stimulated SGK1 activation.","method":"SGK1 activity assay, WNK1 deletion/kinase-dead mutants, PI3K inhibitor studies, siRNA knockdown of WNK1","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — kinase activity assay with domain deletion and kinase-dead mutants plus inhibitor and siRNA, multiple orthogonal approaches, single laboratory","pmids":["16081417"],"is_preprint":false},{"year":2010,"finding":"All four WNK family members (WNK1-4) can activate SGK1 through their N-terminal regions, and all four increase amiloride-sensitive sodium current (ENaC) in reconstitution experiments. Nedd4-2 binds to WNK1, and endogenous SGK1 has reduced activity when WNK1 is knocked down by siRNA.","method":"SGK1 activity assay, electrophysiology (amiloride-sensitive current), Co-IP of WNK1 and Nedd4-2, siRNA knockdown","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase activity assay, electrophysiology, Co-IP, siRNA, single laboratory with multiple methods","pmids":["20525693"],"is_preprint":false},{"year":2001,"finding":"SGK1 stimulates ENaC-mediated Na+ transport in a PI3K-dependent manner; PI3K inhibition blocks both SGK phosphorylation and mineralocorticoid-induced Na+ transport. In vitro-translated SGK1 directly interacts with ENaC subunits expressed as GST fusion proteins. Insulin augments SGK1 phosphorylation and synergizes with mineralocorticoids in stimulating Na+ transport.","method":"PI3K inhibitor studies in A6 kidney cells and Xenopus oocytes, in vitro pulldown with GST-ENaC subunits, electrophysiology","journal":"American journal of physiology. Renal physiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro direct binding (GST pulldown), electrophysiology, inhibitor studies, multiple orthogonal methods, single laboratory","pmids":["11208606"],"is_preprint":false},{"year":2009,"finding":"SGK1 activates MDM2-dependent p53 ubiquitylation (mono- and polyubiquitylation), thereby reducing p53 levels and contributing to cell survival, cell-cycle progression, and epithelial de-differentiation. SGK1 silencing prevents MDM2-mediated p53 ubiquitylation; dominant-negative SGK1 blocks these effects.","method":"RNA silencing, dominant-negative and wild-type SGK1 stable transfection, ubiquitylation assays, mouse model","journal":"Journal of molecular medicine (Berlin, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi, dominant-negative mutant, ubiquitylation assay, multiple cell lines and a mouse model, single laboratory","pmids":["19756449"],"is_preprint":false},{"year":2006,"finding":"ERK directly phosphorylates SGK1 at Ser78 in vitro; inhibition of ERK (PD98059) decreases SGK phosphorylation at Ser78, Thr256, and Ser422 in vivo following spatial training. ERK activation of SGK1 (via SGK1 Thr256 phosphorylation) is involved in spatial memory formation in rats.","method":"In vitro kinase assay (ERK phosphorylating SGK), pharmacological ERK inhibition (PD98059), phospho-specific immunoblot, site-directed mutagenesis (S78A, T256A), hippocampal DNA transfection in rats","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with site-specific mutants plus in vivo pharmacology and behavioural readout, single laboratory","pmids":["16553792"],"is_preprint":false},{"year":2001,"finding":"SGK1 mediates glucocorticoid-induced upregulation of Kv1.5 channel activity, leading to increased repolarizing K+ current, reduced Ca2+ oscillations, and decreased glucose-induced insulin secretion. This pathway is absent in SGK1 knockout mouse islets, confirming SGK1 as the required intermediary.","method":"Xenopus oocyte co-expression electrophysiology, INS-1 cell patch-clamp, K+ channel blockers, SGK1 knockout mouse islets","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 2 / Strong — electrophysiology in multiple systems, SGK1 KO mouse confirmation, pharmacological K+ channel blockade rescue, replicated across in vitro and in vivo models","pmids":["15793248"],"is_preprint":false},{"year":2003,"finding":"SGK1 contains a nuclear localization signal (NLS) that binds to the importin-α nuclear import receptor, controlling nuclear-cytoplasmic shuttling. This NLS is located at an external surface of the kinase domain based on 3D structural modeling.","method":"Importin-α binding assay, NLS identification, structural modeling","journal":"Cellular physiology and biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — binding assay for importin-α mentioned in review context; structural claim from computational modeling only","pmids":["12649597"],"is_preprint":false},{"year":2006,"finding":"SGK1 increases GLUT1 plasma membrane abundance and maximal glucose transport rate without altering substrate affinity; constitutively active SGK1 (S422D) stimulates GLUT1 transport while kinase-inactive SGK1 (K127N) does not. The effect is due to increased transporter plasma membrane abundance, not de novo protein synthesis.","method":"Tracer-flux studies in Xenopus oocytes and HEK-293 cells, constitutively active and kinase-dead SGK1 mutants, kinetic analysis","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional transport assay with active vs. inactive mutants, two cell systems, single laboratory","pmids":["16443776"],"is_preprint":false},{"year":2009,"finding":"SGK1 regulates adipocyte differentiation by directly phosphorylating Foxo1, changing its localization from nucleus to cytosol. SGK1-/- cells cannot relocalize Foxo1 to the cytosol in response to dexamethasone, and SGK1 knockdown diminishes adipogenesis while SGK1 overexpression promotes it.","method":"siRNA knockdown, ectopic SGK1 expression, Foxo1 localization (nuclear/cytosolic fractionation), SGK1-/- cells, immunofluorescence","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown, overexpression, and knockout cell systems with localization readout, single laboratory","pmids":["19965929"],"is_preprint":false},{"year":2002,"finding":"SGK1 (and also SGK2 and SGK3) activates voltage-gated K+ channels (Kv1 family) when expressed in HEK293 cells or Xenopus oocytes, as measured by patch-clamp. The current increase is blocked by TEA and partially by the Kv1-specific blocker margatoxin.","method":"Patch-clamp electrophysiology, transfection of SGK isoforms, Xenopus oocyte dual-electrode voltage clamp","journal":"Pflugers Archiv : European journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology in two expression systems with pharmacological validation, single laboratory","pmids":["12397388"],"is_preprint":false},{"year":2013,"finding":"SGK1 potentiates glucocorticoid receptor (GR) function by increasing GR phosphorylation and GR nuclear translocation, even after cortisol withdrawal. SGK1 also acts downstream of GR to regulate Hedgehog pathway-dependent neurogenesis. Pharmacological SGK1 inhibition (GSK650394) blocks cortisol-induced reduction of neurogenesis.","method":"Small molecule inhibitor (GSK650394), GR antagonist (RU486), gene expression and pathway analysis, phospho-GR immunoblot, nuclear translocation assays in human hippocampal progenitor cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition, GR phosphorylation assay, nuclear translocation, multiple pathway analyses, single laboratory","pmids":["23650397"],"is_preprint":false},{"year":2019,"finding":"SGK directly phosphorylates both Cdc25 (activating phosphatase) and Myt1 (inhibitory kinase) to trigger cyclin B-Cdk1 activation at the meiotic G2/M transition in starfish oocytes. SGK is activated by cooperation between the Gβγ-PI3K pathway and an additional atypical Gβγ pathway upon hormonal stimulation.","method":"In vitro kinase assay with purified SGK, phosphosite identification on Cdc25 and Myt1, rescue experiments in starfish oocytes, pathway inhibitor studies","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay demonstrating direct phosphorylation of two substrates, with genetic/pharmacological pathway dissection in a defined cell biology model","pmids":["31537708"],"is_preprint":false},{"year":2022,"finding":"YAP-dependent regulation of SGK1 is required to activate mTORC1/SREBP signaling and stimulate de novo lipogenesis to support cell proliferation and tissue growth.","method":"Loss-of-function experiments (sgk1 knockdown/knockout), mTORC1 signaling assays, lipogenesis measurements, epistasis between YAP and SGK1","journal":"Developmental cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with defined downstream pathway readouts (mTORC1/SREBP/lipogenesis), single laboratory","pmids":["35216681"],"is_preprint":false},{"year":2017,"finding":"SGK1 inhibition (GSK650394 or shRNA) in prostate cancer cells induces G2/M arrest, autophagy, and apoptosis. Autophagy precedes and is required for apoptosis (3-MA inhibition of autophagy attenuates apoptosis). The mechanism involves suppression of mTOR- and Foxo3a-phosphorylation; pFoxo3a(S253) interacts with LC3 and p27.","method":"Flow cytometry, western blotting, immunofluorescence, transmission electron microscopy, SGK1 shRNA, ectopic SGK1 overexpression, xenograft model","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple cellular methods, shRNA and overexpression rescue, in vivo xenograft, single laboratory","pmids":["29017179"],"is_preprint":false},{"year":2018,"finding":"SGK1 in Treg cells prevents Foxo1 nuclear retention, thereby limiting Foxp3 expression and suppressive function of Tregs while promoting Th17 development. SGK1 mediates IL-23R-dependent inhibition of Treg and development of Th17 cells.","method":"Treg cell-specific SGK1 deletion (conditional knockout), Foxo1 nuclear/cytoplasmic localization assays, Foxp3 CNS1 binding assays, T cell differentiation assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional cell-type-specific KO with defined transcription factor localization and gene expression readouts, single laboratory","pmids":["29346764"],"is_preprint":false},{"year":2017,"finding":"Loss of T cell SGK1 blunts hypertensive response to angiotensin II and DOCA-salt, reduces renal and vascular inflammation, prevents endothelial dysfunction and renal injury. The Na+-K+-2Cl- cotransporter NKCC1 is upregulated in Th17 cells and is required for salt-induced increase in SGK1 and IL-23 receptor expression.","method":"T cell-specific SGK1 knockout mice, blood pressure measurement, vascular and renal inflammation quantification, NKCC1 expression analysis","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific KO with multiple phenotypic readouts, NKCC1 identified upstream of SGK1 in salt signaling, single laboratory","pmids":["28679951"],"is_preprint":false},{"year":2010,"finding":"SGK1 knockout in the C57BL/6J background causes embryonic lethality at E10.5-11.5 due to angiogenic defects, increased apoptosis of endothelial and vascular smooth muscle cells, impaired myocardial trabeculation, and reduced Notch signaling (Efnb2, Nrp1 markers).","method":"SGK1 knockout mouse (C57BL/6J background), histology, apoptosis assays, gene expression analysis","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with defined cellular phenotype (apoptosis, vascular defects) and molecular pathway readout (Notch genes), single laboratory","pmids":["20568246"],"is_preprint":false},{"year":2012,"finding":"SGK1 promotes platelet migration by enhancing WASP phosphorylation and reducing vinculin phosphorylation. Platelets from SGK1 knockout mice show reduced SDF-1-stimulated migration and WASP phosphorylation, and less transmigration into inflamed vessel walls in vivo.","method":"SGK1 knockout mouse platelets, phospho-WASP/vinculin immunoblot, migration assay, in vivo intestinal inflammation model with immunohistochemistry","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with defined phospho-substrate and functional migration readouts in vitro and in vivo, single laboratory","pmids":["22759972"],"is_preprint":false},{"year":2021,"finding":"SGK1 promotes glucose uptake (via elevated GLUT1 transcription) and channels carbon flux into the pentose phosphate pathway to support ATP production and cell survival during ECM-detached conditions; SGK1 activation is necessary and sufficient for ATP generation during ECM detachment.","method":"SGK1 knockdown/overexpression, glucose uptake assays, metabolic flux analysis (PPP), anchorage-independent growth assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function with defined metabolic phenotypes and GLUT1 transcription readout, single laboratory","pmids":["33730592"],"is_preprint":false},{"year":2012,"finding":"SGK1 upregulates Orai1 abundance by phosphorylating Nedd4-2, which then binds to 14-3-3 protein and cannot ubiquitinate Orai1, preventing Orai1 degradation. SGK1 also increases Orai1 and STIM1 protein levels by activating NF-κB.","method":"Overexpression of active vs. inactive SGK1 mutants, Nedd4-2 phosphorylation assay, co-immunoprecipitation (Nedd4-2/14-3-3), store-operated Ca2+ entry measurements","journal":"Cell calcium","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway dissection with kinase-active/inactive mutants and protein interaction assay, single laboratory","pmids":["22682960"],"is_preprint":false},{"year":2006,"finding":"SGK protein kinase activity (phosphorylation at Ser422) facilitates expression of long-term potentiation (LTP) in hippocampal neurons. Constitutively active SGK (S422D) upregulates postsynaptic density-95 expression; dominant-negative SGK (S422A) impairs LTP expression but not induction.","method":"Hippocampal slice electrophysiology (LTP recording), dominant-negative and constitutively active SGK mutant transfection, PSD-95 western blot","journal":"Learning & memory (Cold Spring Harbor, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology with defined gain/loss-of-function mutants and downstream molecular readout, single laboratory","pmids":["16585788"],"is_preprint":false},{"year":2015,"finding":"SGK1 mediates the mTORC2-dependent regulation of ENaC; the mTOR catalytic site inhibitor PP242 (not rapamycin) inhibits ENaC and induces natriuresis in wild-type mice but does not further impair Na+ reabsorption in sgk1-/- mice, placing mTORC2 upstream of SGK1 in ENaC regulation.","method":"mTOR inhibitors (PP242, rapamycin) in wild-type and SGK1 knockout mice, isolated perfused tubules, Na+ flux measurements, in vivo natriuresis","journal":"Nephrology, dialysis, transplantation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological epistasis with SGK1 KO mice, functional tubular Na+ transport readout, single laboratory","pmids":["26163195"],"is_preprint":false},{"year":2021,"finding":"Herbacetin (HBT) directly binds SGK1 and inhibits its activity (IC50 752 nmol); site-specific mutation of Asp177 in SGK1 completely abolishes HBT's inhibitory activity, identifying Asp177 as a critical binding residue. HBT decreases SGK1 phosphorylation and downstream FoxO1 signaling, suppressing cardiomyocyte hypertrophy.","method":"Mass spectrometry-based kinase inhibitory assay, thermal shift assay, KINOMEscan in vitro assay, molecular docking, SGK1 Asp177 site-directed mutagenesis, cardiomyocyte hypertrophy assays","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct binding confirmed by thermal shift + KINOMEscan, critical residue identified by mutagenesis, multiple orthogonal biophysical methods, single laboratory","pmids":["34761560"],"is_preprint":false},{"year":2019,"finding":"EPO/EPO-R ligation on CD4+ T cells abrogates SGK1 gene upregulation and blocks p38-mediated SGK1 phosphorylation, thereby inhibiting RORC-mediated transcription of IL-17 and IL-23 receptor genes and preventing Th17 differentiation.","method":"In vitro T cell differentiation assays, SGK1 gene expression and phosphorylation assays, p38 inhibition, EPO-R conditional knockout mice, murine kidney disease models","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway dissection with gene expression, phospho-SGK1 assays, conditional KO, in vivo disease models; single laboratory","pmids":["31013255"],"is_preprint":false},{"year":2015,"finding":"SGK1 inhibition in the rat medial prefrontal cortex causes helplessness- and anhedonic-like behaviors accompanied by abnormal dendritic spine morphology and synaptic dysfunction.","method":"Pharmacological SGK1 inhibition in rat PFC, behavioral tests (helplessness, anhedonia), dendritic spine morphology analysis, electrophysiology","journal":"PLoS biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct inhibition with defined anatomical/cellular and behavioral phenotype readouts, single laboratory","pmids":["26506154"],"is_preprint":false},{"year":2014,"finding":"In C. elegans, SGK-1 loss-of-function recapitulates the lifespan extension phenotype of daf-2 mutants upon prohibitin depletion; mTORC2 (via RICT-1) regulates SGK-1 for mitochondrial homeostasis (UPRmt) in a pathway parallel to DAF-2/insulin signaling. Genetic epistasis places SGK-1 downstream of both DAF-2 and mTORC2 (RICT-1).","method":"C. elegans genetic epistasis, loss-of-function mutants, UPRmt reporter assays, lifespan assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multi-gene epistasis in C. elegans with defined phenotypic readouts (lifespan, UPRmt), single laboratory","pmids":["25265021"],"is_preprint":false}],"current_model":"SGK1 is a serine/threonine kinase activated downstream of PI3K via PDK1-mediated phosphorylation of Thr256 and Ser422 (and additionally by mTORC2 and WNK1), which phosphorylates a broad array of substrates—including FOXO3a/FKHRL1 (nuclear exclusion), Nedd4-2 (inhibiting ENaC ubiquitination to increase Na+ transport), B-Raf (inhibition), MDM2 pathway components (p53 degradation), Cdc25/Myt1 (meiotic G2/M trigger), and GLUT1/Orai1 regulators—while its own protein levels are tightly controlled by polyubiquitination and 26S proteasomal degradation mediated by Nedd4-2 and the chaperone-dependent E3 ligase CHIP."},"narrative":{"mechanistic_narrative":"SGK1 is a serine/threonine kinase that operates downstream of PI3-kinase to couple growth factor, hormonal, and stress signals to ion transport, transcription factor control, protein turnover, and cell survival [PMID:10357815, PMID:11154281]. Its activation requires PDK1, which directly binds the SGK1 catalytic domain and phosphorylates an activating residue; unlike PKB, this activation proceeds without a pleckstrin homology domain or PIP3, as established by yeast complementation in which SGK substitutes for Ypk1/Ykr2 and is activated by the PDK1 counterpart Pkh1 [PMID:10357815, PMID:10074427]. Additional inputs converge on SGK1: WNK family kinases activate it through a non-catalytic mechanism dependent on their N-terminal regions [PMID:16081417, PMID:20525693], ERK phosphorylates it at Ser78 [PMID:16553792], and mTORC2 acts upstream of SGK1 in epithelial sodium handling [PMID:26163195]. A central output is regulation of the ubiquitin ligase Nedd4-2: SGK1 phosphorylates Nedd4-2 to block its inhibition of ENaC, increasing channel surface expression and Na+ transport [PMID:15328345, PMID:11208606], and the same phosphorylation feeds back to drive Nedd4-2-mediated ubiquitination and proteasomal degradation of SGK1 itself, an effect reinforced by the chaperone-associated E3 ligase CHIP near the endoplasmic reticulum [PMID:15576372, PMID:16895519, PMID:12218062]. SGK1 also controls forkhead transcription factors, phosphorylating FOXO3a/FKHRL1 and Foxo1 to drive their nuclear exclusion and thereby promote cell survival, adipocyte differentiation, and T cell fate decisions [PMID:11154281, PMID:19965929, PMID:29346764]. Through these substrates SGK1 governs diverse physiology: it tunes K+ and Ca2+ channels and glucose transporters [PMID:15793248, PMID:12397388, PMID:16443776, PMID:22682960], promotes p53 turnover via MDM2 [PMID:19756449], triggers the meiotic G2/M transition by phosphorylating Cdc25 and Myt1 [PMID:31537708], supports T cell-driven hypertension and Th17 differentiation [PMID:28679951, PMID:29346764, PMID:31013255], and is required for vascular development, with SGK1 knockout causing embryonic lethality from angiogenic and myocardial defects [PMID:20568246]. The kinase can be directly and selectively inhibited at Asp177 by small molecules, linking its activity to cardiomyocyte hypertrophy via FoxO1 [PMID:34761560].","teleology":[{"year":1999,"claim":"Established how SGK1 is switched on, placing it firmly downstream of PI3K and defining PDK1 as its direct activator independent of a PIP3-binding module.","evidence":"Kinase and GST-pulldown assays with PDK1, phosphatase inactivation and wortmannin inhibition; yeast complementation with Pkh1 activation","pmids":["10357815","10074427"],"confidence":"High","gaps":["Did not resolve the relative contribution of distinct upstream activating inputs in mammalian cells","Physiological stimuli driving nuclear translocation not exhaustively mapped"]},{"year":2001,"claim":"Defined SGK1's substrate selectivity, showing it phosphorylates FKHRL1/FOXO3a and B-Raf at sites distinct from Akt preferences, establishing non-redundant survival and signaling roles.","evidence":"In vitro kinase assays, phosphosite mutagenesis, co-IP for substrate association, nuclear translocation and survival readouts","pmids":["11154281","11410590"],"confidence":"High","gaps":["Did not establish the in vivo balance between SGK1 and Akt on shared substrates","Cellular contexts dictating substrate choice not defined"]},{"year":2001,"claim":"Connected SGK1 to epithelial Na+ handling, showing it stimulates ENaC-mediated transport via PI3K-dependent signaling and direct interaction with ENaC subunits.","evidence":"PI3K inhibitor studies in kidney cells and oocytes, GST-ENaC pulldown, electrophysiology","pmids":["11208606"],"confidence":"High","gaps":["Direct vs. indirect regulation of ENaC not yet distinguished from the Nedd4-2 mechanism","Stoichiometry of ENaC interaction unclear"]},{"year":2002,"claim":"Revealed that SGK1 protein abundance is post-translationally constrained, identifying an N-terminal degron required for polyubiquitination and proteasomal turnover.","evidence":"Ubiquitination assays, proteasome inhibitors, N-terminal truncation mutants, subcellular fractionation","pmids":["12218062"],"confidence":"High","gaps":["The E3 ligase was not identified in this study","Signals coupling degradation to activity state unresolved"]},{"year":2004,"claim":"Defined the Nedd4-2 axis in both directions: SGK1 phosphorylates Nedd4-2 to relieve ENaC inhibition, and Nedd4-2 reciprocally ubiquitinates SGK1, creating a self-limiting feedback loop.","evidence":"In vitro phosphorylation with site mutants, RNAi, dominant-negatives, co-expression ubiquitination assays, half-life measurement, electrophysiology","pmids":["15328345","15576372"],"confidence":"High","gaps":["Quantitative kinetics of the feedback loop not modeled","Did not resolve crosstalk with the CHIP-dependent degradation pathway"]},{"year":2005,"claim":"Identified WNK1 as an upstream activator of SGK1 acting through a non-catalytic, PI3K-dependent mechanism, expanding the input network beyond canonical PDK1 signaling.","evidence":"SGK1 activity assays with WNK1 deletion and kinase-dead mutants, PI3K inhibitors, siRNA","pmids":["16081417"],"confidence":"High","gaps":["Molecular mechanism by which the WNK1 N-terminus activates SGK1 not defined","Whether WNK1 acts as a scaffold or allosteric effector unresolved"]},{"year":2006,"claim":"Identified CHIP as a chaperone-dependent E3 ligase controlling SGK1 turnover near the ER, providing a quality-control route distinct from Nedd4-2.","evidence":"Reciprocal Co-IP, ubiquitination assays, immunofluorescence co-localization","pmids":["16895519"],"confidence":"Medium","gaps":["Relative contribution of CHIP versus Nedd4-2 to SGK1 stability not quantified","Single laboratory without independent confirmation"]},{"year":2006,"claim":"Linked SGK1 to neuronal plasticity, showing ERK phosphorylates SGK1 at Ser78 and that SGK1 activity is required for LTP expression and spatial memory.","evidence":"In vitro kinase assay with site mutants, ERK inhibition, phospho-immunoblot, dominant-negative/constitutively active mutants, hippocampal electrophysiology and behavior","pmids":["16553792","16585788"],"confidence":"High","gaps":["Synaptic substrates of SGK1 mediating LTP not defined","Causal chain from Ser78 phosphorylation to PSD-95 upregulation incomplete"]},{"year":2009,"claim":"Extended SGK1's survival role to the p53 axis and to Foxo1-dependent differentiation, broadening its impact on cell fate.","evidence":"RNAi, dominant-negative and overexpression, ubiquitylation assays, fractionation, mouse model","pmids":["19756449","19965929"],"confidence":"Medium","gaps":["Whether SGK1 acts directly on MDM2 or upstream regulators not resolved","Direct phosphosites on the p53 pathway not mapped"]},{"year":2012,"claim":"Showed SGK1 controls Ca2+ entry machinery and cytoskeletal dynamics, regulating Orai1/STIM1 abundance via Nedd4-2/14-3-3 and platelet migration via WASP phosphorylation.","evidence":"Active/inactive SGK1 mutants, Nedd4-2/14-3-3 co-IP, store-operated Ca2+ measurements; SGK1 KO platelet migration and phospho-substrate assays in vitro and in vivo","pmids":["22682960","22759972"],"confidence":"Medium","gaps":["Direct vs. indirect effects on WASP not fully separated","Generality of the Nedd4-2/14-3-3 mechanism across cell types untested"]},{"year":2015,"claim":"Placed mTORC2 upstream of SGK1 in renal Na+ regulation through pharmacological epistasis, and implicated SGK1 in prefrontal synaptic function and mood-related behavior.","evidence":"PP242/rapamycin in WT and SGK1 KO mice, perfused tubule Na+ flux; PFC SGK1 inhibition with behavioral, spine morphology, and electrophysiology readouts","pmids":["26163195","26506154"],"confidence":"Medium","gaps":["Direct mTORC2 phosphorylation of SGK1 not demonstrated in these studies","Molecular targets in PFC synapses not identified"]},{"year":2018,"claim":"Defined SGK1 as a node in immune cell fate, restraining Treg suppressive function and promoting Th17 differentiation through Foxo1 localization and IL-23R signaling.","evidence":"Treg-specific conditional knockout, Foxo1 localization and Foxp3 CNS1 binding assays, T cell differentiation; T cell SGK1 KO hypertension and NKCC1 analyses","pmids":["29346764","28679951"],"confidence":"Medium","gaps":["Direct Foxo1 phosphosites in Tregs not mapped","Relationship between salt sensing, NKCC1, and SGK1 activation incompletely defined"]},{"year":2019,"claim":"Established a conserved meiotic role, showing SGK directly phosphorylates Cdc25 and Myt1 to trigger Cdk1 activation at the G2/M transition, and identified EPO-R signaling as a negative regulator of SGK1 in T cells.","evidence":"In vitro kinase assays with purified SGK and phosphosite mapping plus oocyte rescue; T cell differentiation with EPO-R conditional KO and p38 inhibition","pmids":["31537708","31013255"],"confidence":"High","gaps":["Conservation of the Cdc25/Myt1 mechanism in mammalian meiosis not established","How EPO-R suppresses both SGK1 transcription and phosphorylation mechanistically unclear"]},{"year":2021,"claim":"Connected SGK1 to anabolic metabolism, showing it drives glucose uptake into the pentose phosphate pathway and acts downstream of YAP to activate mTORC1/SREBP lipogenesis.","evidence":"SGK1 loss/gain-of-function, glucose uptake and metabolic flux assays, GLUT1 transcription readout; YAP-SGK1 epistasis with mTORC1/SREBP/lipogenesis assays","pmids":["33730592","35216681"],"confidence":"Medium","gaps":["Direct substrates linking SGK1 to mTORC1/SREBP not identified","Mechanism of GLUT1 transcriptional control by SGK1 undefined"]},{"year":2021,"claim":"Demonstrated SGK1 is a druggable target, identifying a direct small-molecule inhibitor whose action depends on Asp177 and which suppresses FoxO1-driven cardiomyocyte hypertrophy.","evidence":"Thermal shift, KINOMEscan, molecular docking, Asp177 site-directed mutagenesis, cardiomyocyte hypertrophy assays","pmids":["34761560"],"confidence":"High","gaps":["Selectivity against related kinases not exhaustively profiled","In vivo efficacy and pharmacokinetics not addressed"]},{"year":null,"claim":"How the multiple upstream inputs (PDK1, mTORC2, WNK1-4, ERK, p38) are integrated to set SGK1 activity in a tissue-specific manner, and which substrates dominate in each physiological context, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified quantitative model of competing activating inputs","Tissue-specific substrate hierarchy not defined","Structural basis of substrate selectivity versus Akt incompletely characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,3,4,12,16,19,25,27]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[1,3,19]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[30]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,14]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5,10]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[7]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[16]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,8,29]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[3,10,15,29]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[5,6,7,11]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[22,23,31]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[15,26,20]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[19,21]}],"complexes":[],"partners":["PDK1","NEDD4L","STUB1","WNK1","BRAF","FOXO3","FOXO1","STIM1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00141","full_name":"Serine/threonine-protein kinase Sgk1","aliases":["Serum/glucocorticoid-regulated kinase 1"],"length_aa":431,"mass_kda":48.9,"function":"Serine/threonine-protein kinase which is involved in the regulation of a wide variety of ion channels, membrane transporters, cellular enzymes, transcription factors, neuronal excitability, cell growth, proliferation, survival, migration and apoptosis. Plays an important role in cellular stress response. Contributes to regulation of renal Na(+) retention, renal K(+) elimination, salt appetite, gastric acid secretion, intestinal Na(+)/H(+) exchange and nutrient transport, insulin-dependent salt sensitivity of blood pressure, salt sensitivity of peripheral glucose uptake, cardiac repolarization and memory consolidation. Up-regulates Na(+) channels: SCNN1A/ENAC, SCN5A and ASIC1/ACCN2, K(+) channels: KCNJ1/ROMK1, KCNA1-5, KCNQ1-5 and KCNE1, epithelial Ca(2+) channels: TRPV5 and TRPV6, chloride channels: BSND, CLCN2 and CFTR, glutamate transporters: SLC1A3/EAAT1, SLC1A2 /EAAT2, SLC1A1/EAAT3, SLC1A6/EAAT4 and SLC1A7/EAAT5, amino acid transporters: SLC1A5/ASCT2, SLC38A1/SN1 and SLC6A19, creatine transporter: SLC6A8, Na(+)/dicarboxylate cotransporter: SLC13A2/NADC1, Na(+)-dependent phosphate cotransporter: SLC34A2/NAPI-2B, glutamate receptor: GRIK2/GLUR6. Up-regulates carriers: SLC9A3/NHE3, SLC12A1/NKCC2, SLC12A3/NCC, SLC5A3/SMIT, SLC2A1/GLUT1, SLC5A1/SGLT1 and SLC15A2/PEPT2. Regulates enzymes: GSK3A/B, PMM2 and Na(+)/K(+) ATPase, and transcription factors: CTNNB1 and nuclear factor NF-kappa-B. Stimulates sodium transport into epithelial cells by enhancing the stability and expression of SCNN1A/ENAC. This is achieved by phosphorylating the NEDD4L ubiquitin E3 ligase, promoting its interaction with 14-3-3 proteins, thereby preventing it from binding to SCNN1A/ENAC and targeting it for degradation. Regulates store-operated Ca(+2) entry (SOCE) by stimulating ORAI1 and STIM1. Regulates KCNJ1/ROMK1 directly via its phosphorylation or indirectly via increased interaction with SLC9A3R2/NHERF2. Phosphorylates MDM2 and activates MDM2-dependent ubiquitination of p53/TP53. Phosphorylates MAPT/TAU and mediates microtubule depolymerization and neurite formation in hippocampal neurons. Phosphorylates SLC2A4/GLUT4 and up-regulates its activity. Phosphorylates APBB1/FE65 and promotes its localization to the nucleus. Phosphorylates MAPK1/ERK2 and activates it by enhancing its interaction with MAP2K1/MEK1 and MAP2K2/MEK2. Phosphorylates FBXW7 and plays an inhibitory role in the NOTCH1 signaling. Phosphorylates FOXO1 resulting in its relocalization from the nucleus to the cytoplasm. Phosphorylates FOXO3, promoting its exit from the nucleus and interference with FOXO3-dependent transcription. Phosphorylates BRAF and MAP3K3/MEKK3 and inhibits their activity. Phosphorylates SLC9A3/NHE3 in response to dexamethasone, resulting in its activation and increased localization at the cell membrane. Phosphorylates CREB1. Necessary for vascular remodeling during angiogenesis. Sustained high levels and activity may contribute to conditions such as hypertension and diabetic nephropathy. Isoform 2 exhibited a greater effect on cell plasma membrane expression of SCNN1A/ENAC and Na(+) transport than isoform 1","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/O00141/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SGK1","classification":"Not Classified","n_dependent_lines":12,"n_total_lines":1208,"dependency_fraction":0.009933774834437087},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SGK1","total_profiled":1310},"omim":[{"mim_id":"618472","title":"ASPARAGINASE; ASPG","url":"https://www.omim.org/entry/618472"},{"mim_id":"617476","title":"CNKSR FAMILY, MEMBER 3; CNKSR3","url":"https://www.omim.org/entry/617476"},{"mim_id":"614389","title":"PREGNANCY LOSS, RECURRENT, SUSCEPTIBILITY TO, 1; RPRGL1","url":"https://www.omim.org/entry/614389"},{"mim_id":"612974","title":"DEP DOMAIN-CONTAINING PROTEIN 6; DEPDC6","url":"https://www.omim.org/entry/612974"},{"mim_id":"609414","title":"PHOSPHOINOSITIDE KINASE, FYVE FINGER-CONTAINING; PIKFYVE","url":"https://www.omim.org/entry/609414"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nuclear speckles","reliability":"Enhanced"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"parathyroid gland","ntpm":946.1}],"url":"https://www.proteinatlas.org/search/SGK1"},"hgnc":{"alias_symbol":[],"prev_symbol":["SGK"]},"alphafold":{"accession":"O00141","domains":[{"cath_id":"3.30.200.20","chopping":"94-178_377-416","consensus_level":"high","plddt":84.4234,"start":94,"end":416},{"cath_id":"1.10.510.10","chopping":"183-364","consensus_level":"high","plddt":95.4511,"start":183,"end":364}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00141","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00141-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00141-F1-predicted_aligned_error_v6.png","plddt_mean":79.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SGK1","jax_strain_url":"https://www.jax.org/strain/search?query=SGK1"},"sequence":{"accession":"O00141","fasta_url":"https://rest.uniprot.org/uniprotkb/O00141.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00141/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00141"}},"corpus_meta":[{"pmid":"11154281","id":"PMC_11154281","title":"Protein kinase SGK mediates survival signals by phosphorylating the forkhead transcription factor FKHRL1 (FOXO3a).","date":"2001","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11154281","citation_count":727,"is_preprint":false},{"pmid":"10357815","id":"PMC_10357815","title":"Serum and glucocorticoid-inducible kinase (SGK) is a target of the PI 3-kinase-stimulated signaling pathway.","date":"1999","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/10357815","citation_count":475,"is_preprint":false},{"pmid":"23650397","id":"PMC_23650397","title":"Role for the kinase SGK1 in stress, depression, and glucocorticoid effects on hippocampal neurogenesis.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23650397","citation_count":259,"is_preprint":false},{"pmid":"12649597","id":"PMC_12649597","title":"Stimulus-dependent regulation of serum and glucocorticoid inducible protein kinase (SGK) transcription, subcellular localization and enzymatic activity.","date":"2003","source":"Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/12649597","citation_count":232,"is_preprint":false},{"pmid":"10074427","id":"PMC_10074427","title":"Functional counterparts of mammalian protein kinases PDK1 and SGK in budding yeast.","date":"1999","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/10074427","citation_count":225,"is_preprint":false},{"pmid":"15328345","id":"PMC_15328345","title":"cAMP and serum and glucocorticoid-inducible kinase (SGK) regulate the epithelial Na(+) channel through convergent phosphorylation of Nedd4-2.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15328345","citation_count":186,"is_preprint":false},{"pmid":"11208606","id":"PMC_11208606","title":"SGK integrates insulin and mineralocorticoid regulation of epithelial sodium transport.","date":"2001","source":"American journal of physiology. 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at Thr-32 and Ser-315, promoting FKHRL1 nuclear exit and inactivation, thereby promoting cell survival. SGK1 shows a marked preference for Ser-315 whereas Akt favors Ser-253.\",\n      \"method\": \"In vitro kinase assay, phosphosite mutagenesis, cell survival assays, nuclear translocation experiments\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay with mutagenesis of specific phosphorylation sites, multiple orthogonal methods in one study\",\n      \"pmids\": [\"11154281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"SGK1 is activated downstream of PI3-kinase via phosphorylation at Thr256 and Ser422; PDK1 directly interacts with the catalytic domain of SGK1 (GST pulldown) and phosphorylates/activates it; treatment with protein phosphatase 2A inactivates SGK1. Growth factor stimulation induces SGK1 hyperphosphorylation and nuclear translocation, both blocked by wortmannin.\",\n      \"method\": \"Peptide kinase assay, GST pulldown, phosphatase treatment, inhibitor studies (LY294002, wortmannin), co-transfection with PDK1, subcellular fractionation\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (kinase assay, pulldown, phosphatase inactivation, mutagenesis) in one study with rigorous controls\",\n      \"pmids\": [\"10357815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Yeast Ypk1 and Ykr2 are functional counterparts of SGK; rat SGK (but not mouse PKB or rat p70 S6 kinase) rescues otherwise inviable ypk1Δ ykr2Δ yeast cells. Yeast Pkh1 (PDK1 counterpart) activates mammalian SGK by phosphorylating the same residue as PDK1, and this activation does not require phosphatidylinositol 3,4,5-trisphosphate, consistent with the absence of a pleckstrin homology domain in SGK.\",\n      \"method\": \"Genetic complementation in yeast, in vitro kinase assay with purified Pkh1 and SGK, deletion mutant rescue\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genetic complementation combined with in vitro reconstitution of kinase activation, rigorous controls\",\n      \"pmids\": [\"10074427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SGK and PKA both phosphorylate Nedd4-2 at overlapping sites (Ser-327, Ser-221, Thr-246) to inhibit its binding to ENaC, thereby increasing ENaC surface expression and Na+ transport. SGK overexpression blunts ENaC stimulation by cAMP, and cAMP agonists decrease ENaC stimulation by SGK, indicating convergent regulation through Nedd4-2.\",\n      \"method\": \"In vitro phosphorylation assay, RNA interference, dominant-negative constructs, electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay with site-specific mutations, RNAi, dominant-negative constructs, and functional Na+ transport readout in one study\",\n      \"pmids\": [\"15328345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SGK1 phosphorylates and negatively regulates B-Raf kinase activity by phosphorylating a single Akt consensus site, Ser364, in B-Raf's amino-terminal regulatory domain. SGK displays stronger inhibitory effect on B-Raf than Akt, and enhanced association between SGK and B-Raf (vs. Akt preference for FKHR) explains the selective substrate specificity.\",\n      \"method\": \"In vitro kinase assay, co-immunoprecipitation, phosphosite mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with defined phosphosite, co-IP for substrate association, single laboratory\",\n      \"pmids\": [\"11410590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SGK1 steady-state protein levels are kept low by polyubiquitination and subsequent degradation by the 26S proteasome. Deletion of the N-terminal 60 amino acids prevents polyubiquitination and proteasomal degradation. A fraction of SGK1 localizes to the plasma membrane and the polyubiquitin-modified form is enriched in the membrane-associated fraction.\",\n      \"method\": \"Ubiquitination assays, proteasome inhibitor treatment, truncation mutants, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct ubiquitination assay with deletion mutants and proteasome inhibitor, multiple orthogonal approaches, single laboratory\",\n      \"pmids\": [\"12218062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Nedd4-2 mediates ubiquitin-dependent degradation of SGK1 in a feedback loop: SGK1 phosphorylates Nedd4-2, and this phosphorylation increases Nedd4-2-mediated ubiquitination and proteasomal degradation of SGK. Nedd4-2 overexpression decreases SGK steady-state levels, and Nedd4-2 knockdown by RNAi stabilizes SGK.\",\n      \"method\": \"Co-expression ubiquitination assays, RNA interference, SGK half-life measurement, mutants blocking phosphorylation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ubiquitination assay, RNAi knockdown, phosphorylation site mutants, multiple orthogonal methods, single laboratory\",\n      \"pmids\": [\"15576372\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The E3 ubiquitin ligase CHIP forms a complex with SGK-1, mediates its ubiquitin modification and rapid proteasomal degradation, and co-localizes with SGK-1 at or near the endoplasmic reticulum. CHIP-mediated regulation of SGK-1 levels alters its kinase activity.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, immunofluorescence co-localization\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assay, and localization data, single laboratory\",\n      \"pmids\": [\"16895519\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"WNK1 activates SGK1 through a PI3K-dependent but non-catalytic mechanism; neither WNK1 kinase activity nor its kinase domain is required—rather the N-terminal 220 residues of WNK1 are necessary and sufficient for SGK1 activation. WNK1 phosphorylation at Thr-58 contributes to SGK1 activation. WNK1 is required for IGF-1-stimulated SGK1 activation.\",\n      \"method\": \"SGK1 activity assay, WNK1 deletion/kinase-dead mutants, PI3K inhibitor studies, siRNA knockdown of WNK1\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — kinase activity assay with domain deletion and kinase-dead mutants plus inhibitor and siRNA, multiple orthogonal approaches, single laboratory\",\n      \"pmids\": [\"16081417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"All four WNK family members (WNK1-4) can activate SGK1 through their N-terminal regions, and all four increase amiloride-sensitive sodium current (ENaC) in reconstitution experiments. Nedd4-2 binds to WNK1, and endogenous SGK1 has reduced activity when WNK1 is knocked down by siRNA.\",\n      \"method\": \"SGK1 activity assay, electrophysiology (amiloride-sensitive current), Co-IP of WNK1 and Nedd4-2, siRNA knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase activity assay, electrophysiology, Co-IP, siRNA, single laboratory with multiple methods\",\n      \"pmids\": [\"20525693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SGK1 stimulates ENaC-mediated Na+ transport in a PI3K-dependent manner; PI3K inhibition blocks both SGK phosphorylation and mineralocorticoid-induced Na+ transport. In vitro-translated SGK1 directly interacts with ENaC subunits expressed as GST fusion proteins. Insulin augments SGK1 phosphorylation and synergizes with mineralocorticoids in stimulating Na+ transport.\",\n      \"method\": \"PI3K inhibitor studies in A6 kidney cells and Xenopus oocytes, in vitro pulldown with GST-ENaC subunits, electrophysiology\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro direct binding (GST pulldown), electrophysiology, inhibitor studies, multiple orthogonal methods, single laboratory\",\n      \"pmids\": [\"11208606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SGK1 activates MDM2-dependent p53 ubiquitylation (mono- and polyubiquitylation), thereby reducing p53 levels and contributing to cell survival, cell-cycle progression, and epithelial de-differentiation. SGK1 silencing prevents MDM2-mediated p53 ubiquitylation; dominant-negative SGK1 blocks these effects.\",\n      \"method\": \"RNA silencing, dominant-negative and wild-type SGK1 stable transfection, ubiquitylation assays, mouse model\",\n      \"journal\": \"Journal of molecular medicine (Berlin, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi, dominant-negative mutant, ubiquitylation assay, multiple cell lines and a mouse model, single laboratory\",\n      \"pmids\": [\"19756449\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ERK directly phosphorylates SGK1 at Ser78 in vitro; inhibition of ERK (PD98059) decreases SGK phosphorylation at Ser78, Thr256, and Ser422 in vivo following spatial training. ERK activation of SGK1 (via SGK1 Thr256 phosphorylation) is involved in spatial memory formation in rats.\",\n      \"method\": \"In vitro kinase assay (ERK phosphorylating SGK), pharmacological ERK inhibition (PD98059), phospho-specific immunoblot, site-directed mutagenesis (S78A, T256A), hippocampal DNA transfection in rats\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with site-specific mutants plus in vivo pharmacology and behavioural readout, single laboratory\",\n      \"pmids\": [\"16553792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SGK1 mediates glucocorticoid-induced upregulation of Kv1.5 channel activity, leading to increased repolarizing K+ current, reduced Ca2+ oscillations, and decreased glucose-induced insulin secretion. This pathway is absent in SGK1 knockout mouse islets, confirming SGK1 as the required intermediary.\",\n      \"method\": \"Xenopus oocyte co-expression electrophysiology, INS-1 cell patch-clamp, K+ channel blockers, SGK1 knockout mouse islets\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — electrophysiology in multiple systems, SGK1 KO mouse confirmation, pharmacological K+ channel blockade rescue, replicated across in vitro and in vivo models\",\n      \"pmids\": [\"15793248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"SGK1 contains a nuclear localization signal (NLS) that binds to the importin-α nuclear import receptor, controlling nuclear-cytoplasmic shuttling. This NLS is located at an external surface of the kinase domain based on 3D structural modeling.\",\n      \"method\": \"Importin-α binding assay, NLS identification, structural modeling\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — binding assay for importin-α mentioned in review context; structural claim from computational modeling only\",\n      \"pmids\": [\"12649597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"SGK1 increases GLUT1 plasma membrane abundance and maximal glucose transport rate without altering substrate affinity; constitutively active SGK1 (S422D) stimulates GLUT1 transport while kinase-inactive SGK1 (K127N) does not. The effect is due to increased transporter plasma membrane abundance, not de novo protein synthesis.\",\n      \"method\": \"Tracer-flux studies in Xenopus oocytes and HEK-293 cells, constitutively active and kinase-dead SGK1 mutants, kinetic analysis\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional transport assay with active vs. inactive mutants, two cell systems, single laboratory\",\n      \"pmids\": [\"16443776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SGK1 regulates adipocyte differentiation by directly phosphorylating Foxo1, changing its localization from nucleus to cytosol. SGK1-/- cells cannot relocalize Foxo1 to the cytosol in response to dexamethasone, and SGK1 knockdown diminishes adipogenesis while SGK1 overexpression promotes it.\",\n      \"method\": \"siRNA knockdown, ectopic SGK1 expression, Foxo1 localization (nuclear/cytosolic fractionation), SGK1-/- cells, immunofluorescence\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown, overexpression, and knockout cell systems with localization readout, single laboratory\",\n      \"pmids\": [\"19965929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SGK1 (and also SGK2 and SGK3) activates voltage-gated K+ channels (Kv1 family) when expressed in HEK293 cells or Xenopus oocytes, as measured by patch-clamp. The current increase is blocked by TEA and partially by the Kv1-specific blocker margatoxin.\",\n      \"method\": \"Patch-clamp electrophysiology, transfection of SGK isoforms, Xenopus oocyte dual-electrode voltage clamp\",\n      \"journal\": \"Pflugers Archiv : European journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology in two expression systems with pharmacological validation, single laboratory\",\n      \"pmids\": [\"12397388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SGK1 potentiates glucocorticoid receptor (GR) function by increasing GR phosphorylation and GR nuclear translocation, even after cortisol withdrawal. SGK1 also acts downstream of GR to regulate Hedgehog pathway-dependent neurogenesis. Pharmacological SGK1 inhibition (GSK650394) blocks cortisol-induced reduction of neurogenesis.\",\n      \"method\": \"Small molecule inhibitor (GSK650394), GR antagonist (RU486), gene expression and pathway analysis, phospho-GR immunoblot, nuclear translocation assays in human hippocampal progenitor cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition, GR phosphorylation assay, nuclear translocation, multiple pathway analyses, single laboratory\",\n      \"pmids\": [\"23650397\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SGK directly phosphorylates both Cdc25 (activating phosphatase) and Myt1 (inhibitory kinase) to trigger cyclin B-Cdk1 activation at the meiotic G2/M transition in starfish oocytes. SGK is activated by cooperation between the Gβγ-PI3K pathway and an additional atypical Gβγ pathway upon hormonal stimulation.\",\n      \"method\": \"In vitro kinase assay with purified SGK, phosphosite identification on Cdc25 and Myt1, rescue experiments in starfish oocytes, pathway inhibitor studies\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay demonstrating direct phosphorylation of two substrates, with genetic/pharmacological pathway dissection in a defined cell biology model\",\n      \"pmids\": [\"31537708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"YAP-dependent regulation of SGK1 is required to activate mTORC1/SREBP signaling and stimulate de novo lipogenesis to support cell proliferation and tissue growth.\",\n      \"method\": \"Loss-of-function experiments (sgk1 knockdown/knockout), mTORC1 signaling assays, lipogenesis measurements, epistasis between YAP and SGK1\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with defined downstream pathway readouts (mTORC1/SREBP/lipogenesis), single laboratory\",\n      \"pmids\": [\"35216681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SGK1 inhibition (GSK650394 or shRNA) in prostate cancer cells induces G2/M arrest, autophagy, and apoptosis. Autophagy precedes and is required for apoptosis (3-MA inhibition of autophagy attenuates apoptosis). The mechanism involves suppression of mTOR- and Foxo3a-phosphorylation; pFoxo3a(S253) interacts with LC3 and p27.\",\n      \"method\": \"Flow cytometry, western blotting, immunofluorescence, transmission electron microscopy, SGK1 shRNA, ectopic SGK1 overexpression, xenograft model\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple cellular methods, shRNA and overexpression rescue, in vivo xenograft, single laboratory\",\n      \"pmids\": [\"29017179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SGK1 in Treg cells prevents Foxo1 nuclear retention, thereby limiting Foxp3 expression and suppressive function of Tregs while promoting Th17 development. SGK1 mediates IL-23R-dependent inhibition of Treg and development of Th17 cells.\",\n      \"method\": \"Treg cell-specific SGK1 deletion (conditional knockout), Foxo1 nuclear/cytoplasmic localization assays, Foxp3 CNS1 binding assays, T cell differentiation assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional cell-type-specific KO with defined transcription factor localization and gene expression readouts, single laboratory\",\n      \"pmids\": [\"29346764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Loss of T cell SGK1 blunts hypertensive response to angiotensin II and DOCA-salt, reduces renal and vascular inflammation, prevents endothelial dysfunction and renal injury. The Na+-K+-2Cl- cotransporter NKCC1 is upregulated in Th17 cells and is required for salt-induced increase in SGK1 and IL-23 receptor expression.\",\n      \"method\": \"T cell-specific SGK1 knockout mice, blood pressure measurement, vascular and renal inflammation quantification, NKCC1 expression analysis\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific KO with multiple phenotypic readouts, NKCC1 identified upstream of SGK1 in salt signaling, single laboratory\",\n      \"pmids\": [\"28679951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SGK1 knockout in the C57BL/6J background causes embryonic lethality at E10.5-11.5 due to angiogenic defects, increased apoptosis of endothelial and vascular smooth muscle cells, impaired myocardial trabeculation, and reduced Notch signaling (Efnb2, Nrp1 markers).\",\n      \"method\": \"SGK1 knockout mouse (C57BL/6J background), histology, apoptosis assays, gene expression analysis\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with defined cellular phenotype (apoptosis, vascular defects) and molecular pathway readout (Notch genes), single laboratory\",\n      \"pmids\": [\"20568246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SGK1 promotes platelet migration by enhancing WASP phosphorylation and reducing vinculin phosphorylation. Platelets from SGK1 knockout mice show reduced SDF-1-stimulated migration and WASP phosphorylation, and less transmigration into inflamed vessel walls in vivo.\",\n      \"method\": \"SGK1 knockout mouse platelets, phospho-WASP/vinculin immunoblot, migration assay, in vivo intestinal inflammation model with immunohistochemistry\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with defined phospho-substrate and functional migration readouts in vitro and in vivo, single laboratory\",\n      \"pmids\": [\"22759972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SGK1 promotes glucose uptake (via elevated GLUT1 transcription) and channels carbon flux into the pentose phosphate pathway to support ATP production and cell survival during ECM-detached conditions; SGK1 activation is necessary and sufficient for ATP generation during ECM detachment.\",\n      \"method\": \"SGK1 knockdown/overexpression, glucose uptake assays, metabolic flux analysis (PPP), anchorage-independent growth assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function with defined metabolic phenotypes and GLUT1 transcription readout, single laboratory\",\n      \"pmids\": [\"33730592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"SGK1 upregulates Orai1 abundance by phosphorylating Nedd4-2, which then binds to 14-3-3 protein and cannot ubiquitinate Orai1, preventing Orai1 degradation. SGK1 also increases Orai1 and STIM1 protein levels by activating NF-κB.\",\n      \"method\": \"Overexpression of active vs. inactive SGK1 mutants, Nedd4-2 phosphorylation assay, co-immunoprecipitation (Nedd4-2/14-3-3), store-operated Ca2+ entry measurements\",\n      \"journal\": \"Cell calcium\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway dissection with kinase-active/inactive mutants and protein interaction assay, single laboratory\",\n      \"pmids\": [\"22682960\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"SGK protein kinase activity (phosphorylation at Ser422) facilitates expression of long-term potentiation (LTP) in hippocampal neurons. Constitutively active SGK (S422D) upregulates postsynaptic density-95 expression; dominant-negative SGK (S422A) impairs LTP expression but not induction.\",\n      \"method\": \"Hippocampal slice electrophysiology (LTP recording), dominant-negative and constitutively active SGK mutant transfection, PSD-95 western blot\",\n      \"journal\": \"Learning & memory (Cold Spring Harbor, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology with defined gain/loss-of-function mutants and downstream molecular readout, single laboratory\",\n      \"pmids\": [\"16585788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SGK1 mediates the mTORC2-dependent regulation of ENaC; the mTOR catalytic site inhibitor PP242 (not rapamycin) inhibits ENaC and induces natriuresis in wild-type mice but does not further impair Na+ reabsorption in sgk1-/- mice, placing mTORC2 upstream of SGK1 in ENaC regulation.\",\n      \"method\": \"mTOR inhibitors (PP242, rapamycin) in wild-type and SGK1 knockout mice, isolated perfused tubules, Na+ flux measurements, in vivo natriuresis\",\n      \"journal\": \"Nephrology, dialysis, transplantation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological epistasis with SGK1 KO mice, functional tubular Na+ transport readout, single laboratory\",\n      \"pmids\": [\"26163195\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Herbacetin (HBT) directly binds SGK1 and inhibits its activity (IC50 752 nmol); site-specific mutation of Asp177 in SGK1 completely abolishes HBT's inhibitory activity, identifying Asp177 as a critical binding residue. HBT decreases SGK1 phosphorylation and downstream FoxO1 signaling, suppressing cardiomyocyte hypertrophy.\",\n      \"method\": \"Mass spectrometry-based kinase inhibitory assay, thermal shift assay, KINOMEscan in vitro assay, molecular docking, SGK1 Asp177 site-directed mutagenesis, cardiomyocyte hypertrophy assays\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct binding confirmed by thermal shift + KINOMEscan, critical residue identified by mutagenesis, multiple orthogonal biophysical methods, single laboratory\",\n      \"pmids\": [\"34761560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"EPO/EPO-R ligation on CD4+ T cells abrogates SGK1 gene upregulation and blocks p38-mediated SGK1 phosphorylation, thereby inhibiting RORC-mediated transcription of IL-17 and IL-23 receptor genes and preventing Th17 differentiation.\",\n      \"method\": \"In vitro T cell differentiation assays, SGK1 gene expression and phosphorylation assays, p38 inhibition, EPO-R conditional knockout mice, murine kidney disease models\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway dissection with gene expression, phospho-SGK1 assays, conditional KO, in vivo disease models; single laboratory\",\n      \"pmids\": [\"31013255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SGK1 inhibition in the rat medial prefrontal cortex causes helplessness- and anhedonic-like behaviors accompanied by abnormal dendritic spine morphology and synaptic dysfunction.\",\n      \"method\": \"Pharmacological SGK1 inhibition in rat PFC, behavioral tests (helplessness, anhedonia), dendritic spine morphology analysis, electrophysiology\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct inhibition with defined anatomical/cellular and behavioral phenotype readouts, single laboratory\",\n      \"pmids\": [\"26506154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In C. elegans, SGK-1 loss-of-function recapitulates the lifespan extension phenotype of daf-2 mutants upon prohibitin depletion; mTORC2 (via RICT-1) regulates SGK-1 for mitochondrial homeostasis (UPRmt) in a pathway parallel to DAF-2/insulin signaling. Genetic epistasis places SGK-1 downstream of both DAF-2 and mTORC2 (RICT-1).\",\n      \"method\": \"C. elegans genetic epistasis, loss-of-function mutants, UPRmt reporter assays, lifespan assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multi-gene epistasis in C. elegans with defined phenotypic readouts (lifespan, UPRmt), single laboratory\",\n      \"pmids\": [\"25265021\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SGK1 is a serine/threonine kinase activated downstream of PI3K via PDK1-mediated phosphorylation of Thr256 and Ser422 (and additionally by mTORC2 and WNK1), which phosphorylates a broad array of substrates—including FOXO3a/FKHRL1 (nuclear exclusion), Nedd4-2 (inhibiting ENaC ubiquitination to increase Na+ transport), B-Raf (inhibition), MDM2 pathway components (p53 degradation), Cdc25/Myt1 (meiotic G2/M trigger), and GLUT1/Orai1 regulators—while its own protein levels are tightly controlled by polyubiquitination and 26S proteasomal degradation mediated by Nedd4-2 and the chaperone-dependent E3 ligase CHIP.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SGK1 is a serine/threonine kinase that operates downstream of PI3-kinase to couple growth factor, hormonal, and stress signals to ion transport, transcription factor control, protein turnover, and cell survival [#1, #0]. Its activation requires PDK1, which directly binds the SGK1 catalytic domain and phosphorylates an activating residue; unlike PKB, this activation proceeds without a pleckstrin homology domain or PIP3, as established by yeast complementation in which SGK substitutes for Ypk1/Ykr2 and is activated by the PDK1 counterpart Pkh1 [#1, #2]. Additional inputs converge on SGK1: WNK family kinases activate it through a non-catalytic mechanism dependent on their N-terminal regions [#8, #9], ERK phosphorylates it at Ser78 [#12], and mTORC2 acts upstream of SGK1 in epithelial sodium handling [#29]. A central output is regulation of the ubiquitin ligase Nedd4-2: SGK1 phosphorylates Nedd4-2 to block its inhibition of ENaC, increasing channel surface expression and Na+ transport [#3, #10], and the same phosphorylation feeds back to drive Nedd4-2-mediated ubiquitination and proteasomal degradation of SGK1 itself, an effect reinforced by the chaperone-associated E3 ligase CHIP near the endoplasmic reticulum [#6, #7, #5]. SGK1 also controls forkhead transcription factors, phosphorylating FOXO3a/FKHRL1 and Foxo1 to drive their nuclear exclusion and thereby promote cell survival, adipocyte differentiation, and T cell fate decisions [#0, #16, #22]. Through these substrates SGK1 governs diverse physiology: it tunes K+ and Ca2+ channels and glucose transporters [#13, #17, #15, #27], promotes p53 turnover via MDM2 [#11], triggers the meiotic G2/M transition by phosphorylating Cdc25 and Myt1 [#19], supports T cell-driven hypertension and Th17 differentiation [#23, #22, #31], and is required for vascular development, with SGK1 knockout causing embryonic lethality from angiogenic and myocardial defects [#24]. The kinase can be directly and selectively inhibited at Asp177 by small molecules, linking its activity to cardiomyocyte hypertrophy via FoxO1 [#30].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established how SGK1 is switched on, placing it firmly downstream of PI3K and defining PDK1 as its direct activator independent of a PIP3-binding module.\",\n      \"evidence\": \"Kinase and GST-pulldown assays with PDK1, phosphatase inactivation and wortmannin inhibition; yeast complementation with Pkh1 activation\",\n      \"pmids\": [\"10357815\", \"10074427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the relative contribution of distinct upstream activating inputs in mammalian cells\", \"Physiological stimuli driving nuclear translocation not exhaustively mapped\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined SGK1's substrate selectivity, showing it phosphorylates FKHRL1/FOXO3a and B-Raf at sites distinct from Akt preferences, establishing non-redundant survival and signaling roles.\",\n      \"evidence\": \"In vitro kinase assays, phosphosite mutagenesis, co-IP for substrate association, nuclear translocation and survival readouts\",\n      \"pmids\": [\"11154281\", \"11410590\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish the in vivo balance between SGK1 and Akt on shared substrates\", \"Cellular contexts dictating substrate choice not defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Connected SGK1 to epithelial Na+ handling, showing it stimulates ENaC-mediated transport via PI3K-dependent signaling and direct interaction with ENaC subunits.\",\n      \"evidence\": \"PI3K inhibitor studies in kidney cells and oocytes, GST-ENaC pulldown, electrophysiology\",\n      \"pmids\": [\"11208606\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs. indirect regulation of ENaC not yet distinguished from the Nedd4-2 mechanism\", \"Stoichiometry of ENaC interaction unclear\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Revealed that SGK1 protein abundance is post-translationally constrained, identifying an N-terminal degron required for polyubiquitination and proteasomal turnover.\",\n      \"evidence\": \"Ubiquitination assays, proteasome inhibitors, N-terminal truncation mutants, subcellular fractionation\",\n      \"pmids\": [\"12218062\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The E3 ligase was not identified in this study\", \"Signals coupling degradation to activity state unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined the Nedd4-2 axis in both directions: SGK1 phosphorylates Nedd4-2 to relieve ENaC inhibition, and Nedd4-2 reciprocally ubiquitinates SGK1, creating a self-limiting feedback loop.\",\n      \"evidence\": \"In vitro phosphorylation with site mutants, RNAi, dominant-negatives, co-expression ubiquitination assays, half-life measurement, electrophysiology\",\n      \"pmids\": [\"15328345\", \"15576372\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative kinetics of the feedback loop not modeled\", \"Did not resolve crosstalk with the CHIP-dependent degradation pathway\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified WNK1 as an upstream activator of SGK1 acting through a non-catalytic, PI3K-dependent mechanism, expanding the input network beyond canonical PDK1 signaling.\",\n      \"evidence\": \"SGK1 activity assays with WNK1 deletion and kinase-dead mutants, PI3K inhibitors, siRNA\",\n      \"pmids\": [\"16081417\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which the WNK1 N-terminus activates SGK1 not defined\", \"Whether WNK1 acts as a scaffold or allosteric effector unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified CHIP as a chaperone-dependent E3 ligase controlling SGK1 turnover near the ER, providing a quality-control route distinct from Nedd4-2.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination assays, immunofluorescence co-localization\",\n      \"pmids\": [\"16895519\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of CHIP versus Nedd4-2 to SGK1 stability not quantified\", \"Single laboratory without independent confirmation\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linked SGK1 to neuronal plasticity, showing ERK phosphorylates SGK1 at Ser78 and that SGK1 activity is required for LTP expression and spatial memory.\",\n      \"evidence\": \"In vitro kinase assay with site mutants, ERK inhibition, phospho-immunoblot, dominant-negative/constitutively active mutants, hippocampal electrophysiology and behavior\",\n      \"pmids\": [\"16553792\", \"16585788\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Synaptic substrates of SGK1 mediating LTP not defined\", \"Causal chain from Ser78 phosphorylation to PSD-95 upregulation incomplete\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extended SGK1's survival role to the p53 axis and to Foxo1-dependent differentiation, broadening its impact on cell fate.\",\n      \"evidence\": \"RNAi, dominant-negative and overexpression, ubiquitylation assays, fractionation, mouse model\",\n      \"pmids\": [\"19756449\", \"19965929\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SGK1 acts directly on MDM2 or upstream regulators not resolved\", \"Direct phosphosites on the p53 pathway not mapped\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed SGK1 controls Ca2+ entry machinery and cytoskeletal dynamics, regulating Orai1/STIM1 abundance via Nedd4-2/14-3-3 and platelet migration via WASP phosphorylation.\",\n      \"evidence\": \"Active/inactive SGK1 mutants, Nedd4-2/14-3-3 co-IP, store-operated Ca2+ measurements; SGK1 KO platelet migration and phospho-substrate assays in vitro and in vivo\",\n      \"pmids\": [\"22682960\", \"22759972\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs. indirect effects on WASP not fully separated\", \"Generality of the Nedd4-2/14-3-3 mechanism across cell types untested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Placed mTORC2 upstream of SGK1 in renal Na+ regulation through pharmacological epistasis, and implicated SGK1 in prefrontal synaptic function and mood-related behavior.\",\n      \"evidence\": \"PP242/rapamycin in WT and SGK1 KO mice, perfused tubule Na+ flux; PFC SGK1 inhibition with behavioral, spine morphology, and electrophysiology readouts\",\n      \"pmids\": [\"26163195\", \"26506154\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mTORC2 phosphorylation of SGK1 not demonstrated in these studies\", \"Molecular targets in PFC synapses not identified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined SGK1 as a node in immune cell fate, restraining Treg suppressive function and promoting Th17 differentiation through Foxo1 localization and IL-23R signaling.\",\n      \"evidence\": \"Treg-specific conditional knockout, Foxo1 localization and Foxp3 CNS1 binding assays, T cell differentiation; T cell SGK1 KO hypertension and NKCC1 analyses\",\n      \"pmids\": [\"29346764\", \"28679951\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct Foxo1 phosphosites in Tregs not mapped\", \"Relationship between salt sensing, NKCC1, and SGK1 activation incompletely defined\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established a conserved meiotic role, showing SGK directly phosphorylates Cdc25 and Myt1 to trigger Cdk1 activation at the G2/M transition, and identified EPO-R signaling as a negative regulator of SGK1 in T cells.\",\n      \"evidence\": \"In vitro kinase assays with purified SGK and phosphosite mapping plus oocyte rescue; T cell differentiation with EPO-R conditional KO and p38 inhibition\",\n      \"pmids\": [\"31537708\", \"31013255\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conservation of the Cdc25/Myt1 mechanism in mammalian meiosis not established\", \"How EPO-R suppresses both SGK1 transcription and phosphorylation mechanistically unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Connected SGK1 to anabolic metabolism, showing it drives glucose uptake into the pentose phosphate pathway and acts downstream of YAP to activate mTORC1/SREBP lipogenesis.\",\n      \"evidence\": \"SGK1 loss/gain-of-function, glucose uptake and metabolic flux assays, GLUT1 transcription readout; YAP-SGK1 epistasis with mTORC1/SREBP/lipogenesis assays\",\n      \"pmids\": [\"33730592\", \"35216681\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct substrates linking SGK1 to mTORC1/SREBP not identified\", \"Mechanism of GLUT1 transcriptional control by SGK1 undefined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated SGK1 is a druggable target, identifying a direct small-molecule inhibitor whose action depends on Asp177 and which suppresses FoxO1-driven cardiomyocyte hypertrophy.\",\n      \"evidence\": \"Thermal shift, KINOMEscan, molecular docking, Asp177 site-directed mutagenesis, cardiomyocyte hypertrophy assays\",\n      \"pmids\": [\"34761560\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Selectivity against related kinases not exhaustively profiled\", \"In vivo efficacy and pharmacokinetics not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple upstream inputs (PDK1, mTORC2, WNK1-4, ERK, p38) are integrated to set SGK1 activity in a tissue-specific manner, and which substrates dominate in each physiological context, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified quantitative model of competing activating inputs\", \"Tissue-specific substrate hierarchy not defined\", \"Structural basis of substrate selectivity versus Akt incompletely characterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 3, 4, 12, 16, 19, 25, 27]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [1, 3, 19]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [30]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 14]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5, 10]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 8, 29]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [3, 10, 15, 29]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [5, 6, 7, 11]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [22, 23, 31]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [15, 26, 20]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [19, 21]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PDK1\", \"NEDD4L\", \"STUB1\", \"WNK1\", \"BRAF\", \"FOXO3\", \"FOXO1\", \"STIM1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}