Affinage

FXYD2

Sodium/potassium-transporting ATPase subunit gamma · UniProt P54710

Length
66 aa
Mass
7.3 kDa
Annotated
2026-06-09
35 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

FXYD2 is the gamma subunit of the Na,K-ATPase, a single-span membrane regulatory protein that modulates ion pump kinetics and tunes Na+/K+ homeostasis across multiple tissues (PMID:15755730, PMID:15280368). In native renal enzyme, FXYD2 lowers the apparent affinity for Na+ and confers thermal/structural stability on the alpha1beta1 complex, such that its loss raises total cortical Na,K-ATPase activity and paradoxically activates the apical sodium transporters NCC and NKCC2 in the distal nephron (PMID:15755730, PMID:25472608). Stress-induced expression of the FXYD2a splice variant acts as an inhibitory brake on Na,K-ATPase Vmax and on cell proliferation, an effect reversible by knockdown (PMID:15280368). FXYD2 forms homo-oligomers; the dominant hypomagnesemia-causing G41R mutant co-oligomerizes with wild-type FXYD2 and impairs its glycosylation and routing to the plasma membrane, providing the dominant-negative basis of inherited renal Mg2+ wasting (PMID:17980699, PMID:18448590). Beyond ion transport, FXYD2 negatively regulates beta cell proliferation through the PI3K-Akt pathway and shapes the beta cell transcriptome for glucose-stimulated insulin secretion via a physical interaction with SRC kinase and a downstream FXYD2-SRC-TEAD1 axis (PMID:23344951, PMID:40467586). In sensory neurons, FXYD2 expression is driven by Runx1/Ret signaling and is required to set the mechanosensory thresholds of Adelta and C fibers and to maintain neuropathic and inflammatory pain, making it a target for antisense-based analgesia (PMID:22253804, PMID:27805035, PMID:37154155). Its expression is transcriptionally controlled in disease contexts by HNF1B in ovarian clear cell carcinoma, where silencing triggers autophagy-mediated tumor cell death (PMID:26910837).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2004 High

    Established that FXYD2 is not merely a constitutive subunit but a stress-responsive inhibitory regulator that couples Na,K-ATPase activity to cell growth.

    Evidence Stress induction, stable transfection, and siRNA knockdown with enzymatic and proliferation readouts in NRK-52E cells

    PMID:15280368

    Open questions at the time
    • Splice-variant-specific regulation not resolved at the protein-interaction level
    • Mechanism linking pump inhibition to slowed division unknown
  2. 2005 High

    Defined the core biochemical function of FXYD2 in native tissue: reducing Na+ affinity and stabilizing the enzyme complex.

    Evidence Fxyd2 knockout mouse with purified renal Na,K-ATPase kinetics and thermal stability assays

    PMID:15755730

    Open questions at the time
    • Structural basis of Na+ affinity modulation not defined
    • Does not address tissue-specific roles beyond kidney
  3. 2007 Medium

    Provided the molecular explanation for dominant inheritance of FXYD2-linked hypomagnesemia via hetero-oligomerization and ER trapping.

    Evidence Reciprocal Co-IP of tagged WT and G41R constructs, glycosylation routing assay, disulfide/cysteine mutagenesis

    PMID:17980699

    Open questions at the time
    • Single lab; oligomer stoichiometry not determined
    • In vivo confirmation of ER trapping not shown
  4. 2007 Medium

    Showed FXYD2 surface expression couples glutamate transport to Na,K-ATPase activation in astrocytes, extending its regulatory role beyond kidney.

    Evidence siRNA knockdown with glutamate uptake and Na,K-ATPase activity assays in human fetal astrocytes

    PMID:17316900

    Open questions at the time
    • Mechanism of GLAST-directed FXYD2 trafficking unknown
    • Single lab
  5. 2008 Medium

    Tested whether FXYD2 itself can conduct ions and whether G41R alters channel-like behavior, linking the mutation to Mg2+ handling.

    Evidence Xenopus oocyte voltage clamp and MDCK transepithelial current with site-directed mutagenesis

    PMID:18448590

    Open questions at the time
    • Physiological relevance of the induced currents unconfirmed
    • Direct Mg2+ permeation not demonstrated
  6. 2011 Medium

    Identified a transcript-level mechanism selectively inactivating the FXYD2b variant by exposing an ER retrieval signal.

    Evidence RT-PCR, sequencing, truncated/full-length transfection, and kinetic assays in NRK-52E cells

    PMID:21460224

    Open questions at the time
    • Whether editing occurs in vivo unclear
    • Single cell-line context
  7. 2012 Medium

    Placed FXYD2 downstream of Runx1/Ret signaling in sensory neuron maturation, defining its developmental regulation.

    Evidence In situ hybridization, Runx1 conditional KO, axotomy, and in vivo GDNF rescue

    PMID:22253804

    Open questions at the time
    • Functional consequence in mature neurons not addressed here
    • Direct vs indirect Runx1 regulation unresolved
  8. 2013 High

    Revealed a non-pump role for FXYD2 as a negative regulator of beta cell proliferation through PI3K-Akt signaling.

    Evidence Fxyd2 KO mouse morphometry plus inducible expression and phospho-Akt assays in INS 832/13 cells

    PMID:23344951

    Open questions at the time
    • Link between Akt regulation and Na,K-ATPase activity unclear
    • Mechanism connecting FXYD2 to PI3K-Akt not defined
  9. 2014 Medium

    Demonstrated that loss of FXYD2 elevates renal Na,K-ATPase activity and paradoxically activates apical Na+ transporters, refining the in vivo physiology.

    Evidence Fxyd2 KO mouse with activity assays and phospho-NCC/NKCC2 Western blots

    PMID:25472608

    Open questions at the time
    • Signaling link between pump activity and transporter phosphorylation unknown
    • Single lab
  10. 2016 Medium

    Established FXYD2 as required for setting mechanosensory thresholds and maintaining neuropathic pain, a functional output of its sensory expression.

    Evidence Fxyd2 constitutive KO and acute knockdown with fiber electrophysiology and behavioral assays in SNI model

    PMID:27805035

    Open questions at the time
    • Molecular target setting the threshold not identified
    • Single lab
  11. 2016 Medium

    Connected FXYD2 to HNF1B-driven tumor maintenance and showed its silencing triggers autophagic death in ovarian clear cell carcinoma.

    Evidence siRNA silencing, Na,K-ATPase activity, autophagy and tumor growth assays, HNF1B ChIP/reporter

    PMID:26910837

    Open questions at the time
    • Mechanism linking pump activity to autophagy induction unclear
    • Single lab
  12. 2023 Medium

    Confirmed FXYD2 in DRG neurons as a tractable analgesic target through antisense knockdown.

    Evidence Lipid-modified ASO knockdown in rat neuropathic and inflammatory pain models with behavioral readouts

    PMID:37154155

    Open questions at the time
    • Molecular mechanism of pain maintenance still undefined
    • Off-target effects of ASO not fully excluded
  13. 2025 Medium

    Defined a FXYD2-SRC-TEAD1 transcriptional axis controlling beta cell maturation and insulin secretion via a direct physical interaction with SRC.

    Evidence Co-IP, transcriptomics, hPSC-derived islet differentiation, GSIS, and STZ-diabetic mouse model

    PMID:40467586

    Open questions at the time
    • Reciprocal validation of FXYD2-SRC binding limited
    • How a membrane subunit influences nuclear TEAD1 signaling unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How FXYD2's membrane regulatory role mechanistically connects to its diverse non-pump signaling outputs (Akt, SRC-TEAD1, autophagy, pain threshold setting) remains unresolved.
  • No unified mechanism linking pump regulation to downstream transcriptional/signaling effects
  • Structural basis of partner interactions undefined
  • Tissue-specific splice variant functions incompletely mapped

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 2 GO:0140096 catalytic activity, acting on a protein 1
Localization
GO:0005783 endoplasmic reticulum 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-112316 Neuronal System 2 R-HSA-162582 Signal Transduction 2 R-HSA-382551 Transport of small molecules 2
Partners
ATP1A1ATP1B1GLAST/SLC1A3SRC
Complex memberships
Na,K-ATPase

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2005 Knockout of FXYD2 (gamma subunit) in mice results in purified renal Na,K-ATPase with higher apparent affinity for Na+ (without significant change in K+ affinity) and increased thermal lability, establishing that FXYD2 reduces Na+ affinity and contributes to structural/thermal stability of the enzyme complex in native tissue. Fxyd2 knockout mouse; purified renal Na,K-ATPase kinetic analysis; thermal stability assay The Journal of biological chemistry High 15755730
2004 Stress-induced expression of the FXYD2a splice variant in NRK-52E cells (by hypertonicity, heat shock, oxidative or chemical stress) reduces Na,K-ATPase activity (Vmax) by up to 60% and slows cell division rate; siRNA knockdown of FXYD2a abolishes both effects, establishing that FXYD2a is an inhibitory regulator of Na,K-ATPase activity and cell growth in response to genotoxic stress. Hyperosmotic induction; stable transfection; siRNA knockdown; Na,K-ATPase kinetic assay; cell growth assay The Journal of biological chemistry High 15280368
2007 In human fetal astrocytes, glutamate transporter GLAST/EAAT1 activity directs FXYD2 (gamma subunit) to the cell surface; siRNA knockdown of FXYD2 abolishes glutamate uptake-dependent activation of Na,K-ATPase without affecting GLAST trafficking or activity, demonstrating that FXYD2 surface expression is required for the coupling between glutamate transport and Na,K-ATPase activation. siRNA knockdown; cell surface expression assay; Na,K-ATPase activity assay; glutamate uptake assay Neurochemistry international Medium 17316900
2007 Wild-type FXYD2 proteins form homo-oligomers; the disease-causing G41R mutant also oligomerizes with wild-type FXYD2, and this interaction impairs routing/glycosylation of wild-type FXYD2 to the plasma membrane, providing a molecular explanation for the dominant-negative mechanism of inherited renal hypomagnesemia. Co-immunoprecipitation with tagged FXYD2 constructs; artificial glycosylation routing assay; DTT treatment and C52A mutagenesis to probe disulfide-dependent oligomerization Biochimica et biophysica acta Medium 17980699
2008 Wild-type FXYD2 expressed in Xenopus oocytes induces nonselective ion currents; the G41R mutant additionally induces inward-rectifying cation currents upon hyperpolarization, dependent on a positive charge at position 41 (confirmed by site-directed mutagenesis). In MDCK cells, wild-type FXYD2 (but not G41R) increases transepithelial current in the presence of a Mg2+ gradient at negative potentials, suggesting FXYD2 can mediate basolateral Mg2+ extrusion. Xenopus oocyte expression; two-electrode voltage clamp; site-directed mutagenesis; EDTA injection; transepithelial current measurement in MDCK cells American journal of physiology. Renal physiology Medium 18448590
2013 Global knockout of FXYD2 in mice leads to pancreatic beta cell hyperplasia, increased beta cell mass, elevated circulating insulin, and improved glucose tolerance; FXYD2b splice variant is expressed in wild-type beta cells; Akt phosphorylation is significantly elevated basally in Fxyd2-/- islets, and inducible FXYD2 expression in INS 832/13 cells reduces Akt phosphorylation, establishing that FXYD2 negatively regulates the PI3K-Akt proliferation pathway in beta cells. Fxyd2 knockout mouse; morphometric analysis; RT-PCR; Western blot; immunocytochemistry; inducible expression in INS 832/13 cells; phospho-Akt assay The Journal of biological chemistry High 23344951
2011 A C-to-T base alteration in FXYD2b mRNA (but not FXYD2a) in NRK-52E cells creates a premature stop codon exposing a KKXX ER retrieval signal, causing truncation that disrupts FXYD2b trafficking to the plasma membrane, its association with Na,K-ATPase, and its effects on enzyme kinetics and cell growth; this represents an RNA editing/splicing mechanism that selectively inactivates FXYD2b. RT-PCR; DNA sequencing; transfection with truncated/full-length constructs; error-prone PCR mutagenesis with proliferation selection; Na,K-ATPase kinetic assay The Journal of biological chemistry Medium 21460224
2014 In Fxyd2-/- mouse kidney, total cortical Na,K-ATPase activity is increased without changes in alpha1beta1 subunit expression; NCC (sodium chloride cotransporter) total protein increases ~30% and phosphorylation at T53/S71 (active states) increases 4-6 fold; NKCC2 phosphorylation also increases at least twofold, demonstrating that loss of FXYD2 leads to elevated Na,K-ATPase activity and paradoxical activation of apical sodium transporters in the distal nephron. Fxyd2 knockout mouse; Na,K-ATPase activity assay; Western blot for NCC, phospho-NCC, NKCC2, phospho-NKCC2; immunofluorescence; blood pressure measurement Physiological reports Medium 25472608
2012 FXYD2 expression in dorsal root ganglia is restricted to TrkB-expressing mechanoreceptors and Ret-positive/IB4-binding non-peptidergic nociceptors; the transcription factor Runx1 controls FXYD2 expression during somatosensory maturation partly through regulation of Ret; axotomy downregulates FXYD2, and this is reversed by in vivo delivery of GDNF family ligands, placing FXYD2 downstream of the Ret signaling pathway in nociceptor maturation. In situ hybridization; immunofluorescence; Runx1 conditional KO mouse; axotomy model; in vivo GDNF delivery; RT-PCR PloS one Medium 22253804
2016 Fxyd2-/- mice show altered mechanosensitivity of Adelta-fiber low-threshold mechanoreceptors and C-fiber nociceptor subpopulations; constitutive or acute knockdown of Fxyd2 in the spared nerve injury neuropathic pain model alleviates mechanical hypersensitivity (allodynia), establishing that FXYD2 is required for setting mechanosensory thresholds and maintaining neuropathic pain. Fxyd2 constitutive KO mouse; spared nerve injury neuropathic pain model in rats; acute Fxyd2 knockdown; electrophysiological recording of Adelta and C fibers; behavioral pain assays Scientific reports Medium 27805035
2016 Silencing of FXYD2 in ovarian clear cell carcinoma (OCCC) cells inhibits Na+/K+-ATPase enzyme activity and suppresses tumor growth via induction of autophagy-mediated cell death; FXYD2 expression in OCCC is transcriptionally regulated by the transcription factor HNF1B. siRNA silencing; Na,K-ATPase activity assay; tumor growth assay in vitro and in vivo; autophagy assay; ChIP/reporter assay for HNF1B regulation Oncotarget Medium 26910837
2025 FXYD2 physically interacts with SRC proto-oncogene (non-receptor tyrosine kinase) in pancreatic beta cells and regulates a FXYD2-SRC-TEAD1 signaling axis that controls the beta cell transcriptome necessary for glucose-stimulated insulin secretion; FXYD2High hiPSC-derived islet organoids show superior glucose-stimulated insulin secretion and improve hyperglycemia in diabetic mice compared to FXYD2Low counterparts. Co-immunoprecipitation (FXYD2-SRC interaction); transcriptomic analysis; hPSC-derived beta cell differentiation; GSIS assay; in vivo STZ-diabetic mouse model Nature communications Medium 40467586
2024 The transcription factor SIX2, reactivated in LPS-stimulated microglia, suppresses neuroinflammation by upregulating FXYD2 expression; RNA-seq analysis of inflammatory microglia identified FXYD2 as a downstream effector of SIX2-mediated anti-inflammatory signaling, placing FXYD2 in the SIX2-neuroinflammation pathway. LPS stimulation of microglia; SIX2 overexpression; RNA-seq; Cx3cr1-CreERT2 in vivo mouse model; conditioned media toxicity assay Brain research bulletin Low 38688414
2018 FXYD2 (G41R) mutation and mutations in transcription factors HNF-1B and PCBD1 that affect FXYD2 expression result in impaired interactions of FXYD2 with Na,K-ATPase, leading to destabilization/inactivation of the pump; FXYD2 also stabilizes Na,K-ATPase by amplifying interactions with phosphatidylserine and cholesterol in the membrane; loss of this stabilization explains Mg2+ wasting in DCT. Review integrating in vitro binding/stability studies, patient mutation analysis, and functional Na,K-ATPase assays (cited across literature) Physiological reports Low 30175537
2023 Intrathecal or intravenous injection of lipid-modified antisense oligonucleotides (FXYD2-LASO) targeting FXYD2 mRNA in rat neuropathic and inflammatory pain models leads to virtually complete alleviation of pain symptoms; chemically stabilized FXYD2-LASO-Gapmer prolongs therapeutic effect to 10 days after a single injection, confirming FXYD2 expression in DRG neurons is required for maintenance of chronic pain. Antisense oligonucleotide (ASO) knockdown in rat neuropathic (SNI) and inflammatory pain models; behavioral pain testing; intrathecal and intravenous administration JCI insight Medium 37154155

Source papers

Stage 0 corpus · 35 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Na,K-ATPase from mice lacking the gamma subunit (FXYD2) exhibits altered Na+ affinity and decreased thermal stability. The Journal of biological chemistry 69 15755730
2004 Stress-induced expression of the gamma subunit (FXYD2) modulates Na,K-ATPase activity and cell growth. The Journal of biological chemistry 46 15280368
2015 Recurrent FXYD2 p.Gly41Arg mutation in patients with isolated dominant hypomagnesaemia. Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association 45 25765846
2007 Glutamate transporter GLAST/EAAT1 directs cell surface expression of FXYD2/gamma subunit of Na, K-ATPase in human fetal astrocytes. Neurochemistry international 44 17316900
2000 Genomic organization of the human FXYD2 gene encoding the gamma subunit of the Na,K-ATPase. Biochemical and biophysical research communications 42 11112438
2010 A genomic-based approach identifies FXYD domain containing ion transport regulator 2 (FXYD2)gammaa as a pancreatic beta cell-specific biomarker. Diabetologia 38 20379810
2009 Differential cellular expression of FXYD1 (phospholemman) and FXYD2 (gamma subunit of Na, K-ATPase) in normal human tissues: a study using high density human tissue microarrays. Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft 36 19879113
2013 Hyperplasia of pancreatic beta cells and improved glucose tolerance in mice deficient in the FXYD2 subunit of Na,K-ATPase. The Journal of biological chemistry 30 23344951
2005 Splice variants of the gamma subunit (FXYD2) and their significance in regulation of the Na, K-ATPase in kidney. Journal of bioenergetics and biomembranes 30 16691469
2016 Targeting FXYD2 by cardiac glycosides potently blocks tumor growth in ovarian clear cell carcinoma. Oncotarget 29 26910837
2001 The mouse Na+-K+-ATPase gamma-subunit gene (Fxyd2) encodes three developmentally regulated transcripts. Physiological genomics 25 11526196
2008 Human FXYD2 G41R mutation responsible for renal hypomagnesemia behaves as an inward-rectifying cation channel. American journal of physiology. Renal physiology 24 18448590
2018 Renal Mg handling, FXYD2 and the central role of the Na,K-ATPase. Physiological reports 23 30175537
2016 Fxyd2 regulates Aδ- and C-fiber mechanosensitivity and is required for the maintenance of neuropathic pain. Scientific reports 21 27805035
2012 Identification of a crab gill FXYD2 protein and regulation of crab microsomal Na,K-ATPase activity by mammalian FXYD2 peptide. Biochimica et biophysica acta 21 22588134
2015 Development of a peptide-functionalized imaging nanoprobe for the targeting of (FXYD2)γa as a highly specific biomarker of pancreatic beta cells. Contrast media & molecular imaging 20 25930968
2012 Regulation of the Na,K-ATPase gamma-subunit FXYD2 by Runx1 and Ret signaling in normal and injured non-peptidergic nociceptive sensory neurons. PloS one 18 22253804
2007 Impaired routing of wild type FXYD2 after oligomerisation with FXYD2-G41R might explain the dominant nature of renal hypomagnesemia. Biochimica et biophysica acta 18 17980699
2012 Expression of the Na+/K+-transporting ATPase gamma subunit FXYD2 in renal tumors. Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc 15 23196795
2020 Osmotic and ionic regulation, and modulation by protein kinases, FXYD2 peptide and ATP of gill (Na+, K+)-ATPase activity, in the swamp ghost crab Ucides cordatus (Brachyura, Ocypodidae). Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology 13 32956795
2016 Beneficial Renal and Pancreatic Phenotypes in a Mouse Deficient in FXYD2 Regulatory Subunit of Na,K-ATPase. Frontiers in physiology 13 27014088
2014 Paradoxical activation of the sodium chloride cotransporter (NCC) without hypertension in kidney deficient in a regulatory subunit of Na,K-ATPase, FXYD2. Physiological reports 13 25472608
2024 Molecular Basis of Na, K-ATPase Regulation of Diseases: Hormone and FXYD2 Interactions. International journal of molecular sciences 11 39769162
2011 Post-transcriptional control of Na,K-ATPase activity and cell growth by a splice variant of FXYD2 protein with modified mRNA. The Journal of biological chemistry 11 21460224
2021 FXYD2 mRNA expression represents a new independent factor that affects survival of glioma patients and predicts chemosensitivity of patients to temozolomide. BMC neurology 10 34753441
2021 An integrated microfluidic platform for detection of ovarian clear cell carcinoma mRNA biomarker FXYD2. Lab on a chip 9 34013940
2009 FXYD2 and Na,K-ATPase expression in isolated human proximal tubular cells: disturbed upregulation on renal hypomagnesemia? The Journal of membrane biology 9 19865785
2003 Exclusion of mutations in FXYD2, CLDN16 and SLC12A3 in two families with primary renal Mg2+ loss. Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association 9 12584272
2001 Expression of a novel member of the ATP1G1/PLM/MAT8 family, phospholemman-like protein (PLP) gene, in the developmental process of mouse cerebellum. Gene 9 11733139
2023 FXYD2 antisense oligonucleotide provides an efficient approach for long-lasting relief of chronic peripheral pain. JCI insight 7 37154155
2022 Salinity-dependent modulation by protein kinases and the FXYD2 peptide of gill (Na+, K+)-ATPase activity in the freshwater shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae). Biochimica et biophysica acta. Biomembranes 7 35671812
2024 Microglial SIX2 suppresses lipopolysaccharide (LPS)-induced neuroinflammation by up-regulating FXYD2 expression. Brain research bulletin 6 38688414
2025 FXYD2 marks and regulates maturity of β cells via ion channel-mediated signal transduction. Nature communications 5 40467586
2025 The Metabolic Consequences of Pathogenic Variant in FXYD2 Gene Encoding the Gamma Subunit of Sodium/Potassium-Transporting ATPase in Two Siblings with Sodium-Dependent Defect of Fructose, Galactose and Glucose Renal Reabsorption. Genes 1 40428357
2025 Knockdown of FXYD2 inhibits mepivacaine-induced cardiomyocyte injury by activating the PI3K/AKT signaling pathway. European journal of medical research 0 41413828

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