{"gene":"AQP4","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":1995,"finding":"AQP4 (MIWC) is expressed at the plasma membrane of astrocytes, ependymal cells lining the aqueductal system, skeletal muscle sarcolemma, kidney collecting duct basolateral membranes, gastric parietal cells, and glandular epithelia; its cellular distribution matches precisely the sites where orthogonal arrays of particles (OAPs) are observed by freeze-fracture electron microscopy, suggesting AQP4 is the OAP protein.","method":"Immunogold electron microscopy and immunolocalization in rat tissues","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct immunogold EM localization replicated across multiple tissue types in a focused study; OAP co-localization hypothesis directly supported by morphological data","pmids":["8537439"],"is_preprint":false},{"year":1995,"finding":"AQP4 (MIWC) spans the endoplasmic reticulum membrane with six transmembrane domains and cytoplasmic N- and C-termini (distinct from the four-transmembrane topology of AQP1/CHIP28); membrane integration occurs after synthesis of the first hydrophobic region and N-linked glycosylation occurs at residue N131.","method":"Cell-free translation with ER microsomes, protease protection assays, N-linked glycosylation mapping, and Xenopus oocyte expression using cDNA chimeras with reporter epitopes","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro translation with multiple chimeric constructs, protease accessibility, and glycosylation confirmation; rigorous topology determination","pmids":["7541239"],"is_preprint":false},{"year":1996,"finding":"AQP4 (MIWC) spontaneously assembles into orthogonal arrays of particles (OAPs) in transfected CHO cell plasma membranes, demonstrating that a single aquaporin molecule is sufficient to form OAPs; AQP1 expression does not produce OAPs, showing OAP formation is AQP4-specific.","method":"Stable transfection of CHO cells, freeze-fracture electron microscopy, immunoblot, cell fractionation, stopped-flow light scattering for water permeability","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct reconstitution in heterologous cells with freeze-fracture EM demonstrating OAP morphology identical to native tissue; controlled with AQP1 negative result","pmids":["8617713"],"is_preprint":false},{"year":1996,"finding":"AQP4 is mercurial-insensitive because it lacks a cysteine residue near its NPA motifs; introduction of cysteine mutations at residues 70–73 or 189 (near the NPA motifs) confers HgCl2 sensitivity, identifying these residues as lining the aqueous pore. Bulky tryptophan substitutions at G72 or A188 abolish water transport and exert a dominant-negative effect, indicating AQP4 monomers interact functionally.","method":"Site-directed mutagenesis, Xenopus oocyte expression, osmotic water permeability assay (Pf), HgCl2 dose-response, quantitative immunofluorescence","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis combined with functional assays in oocytes; dominant-negative result confirms monomer-monomer interaction; multiple mutants tested","pmids":["8555225"],"is_preprint":false},{"year":2013,"finding":"AQP4 surface expression in astrocytes is regulated by vesicular trafficking; AQP4e isoform localizes to vesicles whose mobility correlates with AQP4 plasma membrane abundance. Hypoosmotic stimulation (mimicking brain edema) transiently reduces vesicle mobility and transiently changes AQP4 plasma membrane localization; increased cytosolic cAMP (reactive astrocyte model) increases AQP4 surface expression. Actin rearrangement accompanies reactive astrocyte stimulation and vimentin depolymerization accompanies hypoosmotic conditions.","method":"Live-cell imaging of vesicle mobility in cultured rat astrocytes, plasma membrane AQP4 quantification, cytoskeletal analysis under pharmacological and osmotic stimulation","journal":"Glia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct live imaging of vesicle dynamics correlated with membrane localization; single lab, two complementary methods","pmids":["23505074"],"is_preprint":false},{"year":2013,"finding":"AQP4 monomers form tetramers in membranes, and M23-AQP4 tetramers further aggregate into supramolecular orthogonal arrays of particles (OAPs); the M1/M23 isoform ratio controls the extent of OAP assembly, and AQP4-IgG binding and complement-dependent cytotoxicity in NMO are greatly enhanced by OAP formation.","method":"Cell-based assays, complement cytotoxicity assays, isoform expression studies reviewed from multiple independent experiments","journal":"Brain pathology (Zurich, Switzerland)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic conclusions drawn from multiple referenced experimental studies; review synthesis, confidence limited by absence of primary experimental detail in abstract","pmids":["24118484"],"is_preprint":false},{"year":2013,"finding":"AQP4-IgG diagnostic sensitivity is highest with M23-AQP4 expressing cells (97.5%) versus M1-AQP4 (27.5%) in cell-based assays (CBA); the nucleotide at position -3 of the AUG of M1 greatly affects the M1/M23 protein ratio and NMO-IgG binding. An N-terminal fluorescent tag on M23-AQP4 disrupts AQP4 suprastructures and reduces test sensitivity.","method":"Cell-based assay (CBA) with systematic variation of AQP4 isoform, translation initiation signals, fluorescent tag position; NMO patient serum testing","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct experimental manipulation of AQP4 isoform ratios and structural tags with functional readout in CBA; single lab, multiple orthogonal approaches","pmids":["24260168"],"is_preprint":false},{"year":2015,"finding":"AQP4 and TRPV4 colocalize in Müller glial endfeet and radial processes in mouse retina. AQP4-mediated water influx drives TRPV4-mediated calcium entry during hypo-osmotic swelling; conversely, calcium entry through TRPV4 modulates volume regulation and Aqp4 gene expression. In Xenopus oocytes co-expressing both channels, when swelling rate was osmotically matched, TRPV4 activation became independent of AQP4, demonstrating that AQP4's contribution is specifically through accelerating water influx.","method":"Genetic ablation (Trpv4-/- and Aqp4-/- mice), live calcium imaging, cell volume measurements, Xenopus oocyte co-expression, pharmacological TRPV4 agonist/antagonist studies, gene expression analysis","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic knockouts, heterologous oocyte reconstitution, and pharmacological validation across multiple labs; osmotic matching experiment directly establishes mechanism","pmids":["26424896"],"is_preprint":false},{"year":2019,"finding":"AQP4 aggregation state determines glioma cell fate: M23-AQP4 (OAP-forming isoform) triggers F-actin cytoskeletal changes and promotes apoptosis, while M1-AQP4 (tetramer-only) increases cell migration and MMP-9 activity. Two C-terminal proline residues (Pro254 and Pro296) mediate the relationship between AQP4 aggregation state and the actin cytoskeleton.","method":"Selective isoform expression in glioma cell lines, F-actin imaging, apoptosis assays, cell migration/invasion assays, MMP-9 activity assay, proline mutagenesis","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-selective expression with multiple functional readouts and mutagenesis; single lab study","pmids":["30877104"],"is_preprint":false},{"year":2019,"finding":"AQP4 is a novel cargo of the SNX27-retromer complex, which recycles endocytosed AQP4 back to the cell surface and prevents lysosomal degradation. Kidins220 deficiency causes SNX27-retromer downregulation leading to AQP4 lysosomal degradation; SNX27 silencing decreases AQP4 levels in wild-type astrocytes, while SNX27 overexpression restores AQP4 in Kidins220-deficient astrocytes.","method":"Co-immunoprecipitation, SNX27 knockdown and overexpression in astrocytes, lysosome inhibitor (bafilomycin) rescue, mouse genetic model (Kidins220 deficient), human iNPH patient tissue analysis","journal":"Molecular psychiatry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional rescue experiments (SNX27 OE restores AQP4), pharmacological lysosomal block, human tissue validation, and mouse model; multiple orthogonal methods","pmids":["34002021"],"is_preprint":false},{"year":2021,"finding":"In M23-AQP4 null (CRISPR/Cas9) mouse spinal cord, M1-AQP4 protein is drastically reduced without changes in M1-AQP4 transcription, splicing, or protein degradation, indicating translational control. mRNA-protein pulldown and quantitative mass spectrometry identified AQP4 mRNA-binding proteins (RBPs): polypyrimidine tract binding protein 1 (PTBP1, a positive translational regulator) shows increased interaction with AQP4 mRNA in M23-null, and RNA helicase DDX17 shows decreased interaction. DDX17 knockdown upregulates AQP4 protein and increases astrocyte swelling without affecting mRNA levels, identifying DDX17 as a negative translational regulator of AQP4.","method":"CRISPR/Cas9 M23-null mouse model, mRNA-protein pulldown, quantitative mass spectrometry, DDX17 siRNA knockdown, astrocyte primary culture swelling assay, western blot, RT-PCR","journal":"Glia","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution-level identification of RBPs by mass spectrometry combined with loss-of-function knockdown; genetic mouse model validates in vivo relevance; multiple orthogonal methods","pmids":["34038017"],"is_preprint":false},{"year":2020,"finding":"Deletion of astrocytic connexins Cx43 and Cx30 causes substantial reduction of perivascular AQP4, downregulation of total AQP4 protein and mRNA, and isoform-specific effects: M23-AQP4 is reduced while M1-AQP4 and the AQP4ex isoform are increased, demonstrating a complex interdependence between astrocytic gap junction coupling and AQP4 membrane localization and isoform composition.","method":"Quantitative immunogold cytochemistry, isoform-specific western blot, mRNA analysis in connexin Cx43/Cx30 double knockout mice","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative immunogold EM with genetic knockout model; single lab, two orthogonal quantitative methods","pmids":["32046059"],"is_preprint":false},{"year":2022,"finding":"An AQP4-A25Q point mutation that depolymerizes OAPs (confirmed by blue native PAGE, super-resolution imaging, and immunogold EM) without affecting total AQP4 mRNA or protein expression reduces polarized perivascular expression of AQP4 at astrocytic endfeet and is neuroprotective in cerebral edema models (water intoxication and MCAO/reperfusion), demonstrating that OAP structure is required for polarized endfeet localization.","method":"Transgenic knock-in mouse (AQP4-A25Q), blue native PAGE, super-resolution imaging, immunogold EM, brain water content measurement, MCAO stroke model, behavioral scoring","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — genetic knock-in with point mutation, confirmed by three independent structural methods (BN-PAGE, STORM, immunogold EM), functional validation in two disease models","pmids":["36100398"],"is_preprint":false},{"year":2022,"finding":"Disassembly of supramolecular AQP4 complexes and loss of AQP4 from astrocytic endfoot membranes occurs at the border zone one week after ischemic stroke, mechanistically coupled to downregulation of the AQP4ex (readthrough) isoform, suggesting AQP4ex stabilizes OAPs at perivascular endfeet.","method":"Immunofluorescence and confocal analysis of murine stroke model at defined time points post-ischemia; isoform-specific analysis","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment with isoform-specific analysis; correlative mechanistic link between AQP4ex and OAP stability not yet established causally; single lab","pmids":["35163040"],"is_preprint":false},{"year":2023,"finding":"The AQP4ex (readthrough) isoform preferentially localizes around the blood-brain barrier through interaction with the scaffolding protein α-syntrophin. Increasing AQP4ex dose enhances perivascular localization of both α-syntrophin and AQP4 without changing total protein expression. Complete AQP4x loss (NoXHom) alters BBB integrity (increased endothelial budding vesicles, leakier BBB by MRI). AQP4x plays a measurable role in recruiting structural/functional support proteins to blood vessels.","method":"AllX and NoX transgenic mouse lines (quantitative AQP4x modulation), immunofluorescence, electron microscopy, MRI, α-syntrophin colocalization analysis","journal":"Frontiers in cellular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic dose-response model with two complementary knockin/knockout lines; EM and MRI for BBB integrity; single lab","pmids":["38077948"],"is_preprint":false},{"year":2024,"finding":"LRRK2 directly interacts with and phosphorylates AQP4 in vitro and in vivo. LRRK2 R1441G-mediated AQP4 phosphorylation induces AQP4 depolarization and disrupts glymphatic clearance of IFNγ, leading to neuroinflammation and dopaminergic neurodegeneration. LRRK2 inhibition restores AQP4 polarity and improves glymphatic function.","method":"In vitro kinase assay, in vivo phosphorylation in transgenic mice, AQP4 polarization imaging, glymphatic tracer studies, LRRK2 inhibitor treatment, IFNγ clearance measurement","journal":"NPJ Parkinson's disease","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro and in vivo kinase assay establishing phosphorylation, functional rescue with inhibitor, and glymphatic readthrough tracer studies; multiple orthogonal methods","pmids":["38296953"],"is_preprint":false},{"year":2012,"finding":"NFAT5 directly binds the AQP4 gene promoter (between -49 and -38 bp) and is required for transcriptional upregulation of AQP4 in astrocytes under swelling conditions (ammonia treatment). NFAT5 siRNA silencing significantly reduces AQP4 expression, and ChIP assay shows increased NFAT5 binding to the AQP4 promoter after ammonia treatment.","method":"Chromatin immunoprecipitation (ChIP), dual-luciferase reporter assay, siRNA knockdown, in vivo kainic acid brain edema model, immunohistochemistry","journal":"Cellular and molecular neurobiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct promoter binding demonstrated by ChIP and luciferase reporter, causal role confirmed by siRNA knockdown, in vivo validation; multiple orthogonal methods","pmids":["23180003"],"is_preprint":false},{"year":2022,"finding":"TNF-α activates the NF-κB pathway in astrocytes, causing p65 protein to bind the AQP4 gene promoter region, enhancing AQP4 transcription and causing astrocyte edema and reduced viability. The NF-κB inhibitor BAY 11-7082 blocks this effect, and p65 siRNA reduces AQP4 expression and improves astrocyte viability.","method":"Dual-luciferase reporter assay, chromatin immunoprecipitation (ChIP), NF-κB pathway inhibitor (BAY 11-7082), p65 siRNA, western blot, qPCR, cell viability assay (CCK-8)","journal":"Bioscience reports","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct promoter binding by ChIP and luciferase reporter, with pharmacological and genetic loss-of-function rescue; single lab study","pmids":["35260880"],"is_preprint":false},{"year":2024,"finding":"AQP4 endocytosis and lysosomal degradation is regulated by MMP-9 cleavage of β-dystroglycan (β-DG): MMP-9 cleaves β-DG, disrupting its anchorage of AQP4 on the astrocyte plasma membrane, leading to AQP4 endocytosis. Bafilomycin A1 (lysosome inhibitor) reverses AQP4 downregulation in diabetic mice; MMP-9/β-DG inhibition restores AQP4 surface expression and partially alleviates diabetic cognitive dysfunction.","method":"Diabetic mouse model (STZ), lysosome inhibitor rescue (bafilomycin A1), MMP-9 inhibition, β-DG cleavage analysis, western blot, immunofluorescence, behavioral tests","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological rescue of lysosomal degradation, β-DG cleavage mechanistic link established, in vivo model; single lab, MMP-9/β-DG pathway previously known","pmids":["38512439"],"is_preprint":false},{"year":2024,"finding":"MMP-9 activation downstream of oxidative stress in intracerebral hemorrhage cleaves β-dystroglycan, reducing AQP4 polarity. Edaravone (oxygen free radical scavenger) downregulates MMP-9 and upregulates β-DG, maintaining AQP4 polarity and reducing brain edema. MMP-9 inhibitor similarly maintains AQP4 polarity, confirming the OS/MMP9/β-DG/AQP4 pathway.","method":"Autologous blood ICH mouse model, edaravone and MMP9-inh treatment, immunofluorescence, western blot, ELISA, Evans blue permeability, brain water content, intracisternal tracer infusion","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and specific inhibitor experiments in vivo establishing pathway; single lab; convergent evidence from two independent inhibitors","pmids":["38421470"],"is_preprint":false},{"year":2023,"finding":"The circadian protein Per2 directs AQP4 perivascular polarization in astrocytes through interactions with α-dystrobrevin (Dtna), a subunit of the AQP4 anchoring complex. Per2 expression negatively correlates with AQP4 polarization; CUMS mice with disrupted circadian rhythms show impaired AQP4 polarization, which is restored by melatonin treatment that normalizes Per2 expression.","method":"Co-immunoprecipitation of Per2 with Dtna in primary cultured astrocytes, CUMS mouse model, melatonin treatment, EEG sleep analysis, AQP4 polarization imaging, circadian protein expression analysis","journal":"Translational psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishes Per2-Dtna interaction in primary astrocytes; in vivo rescue experiment with melatonin; single lab","pmids":["37802998"],"is_preprint":false},{"year":2025,"finding":"AQP4-M23 isoform is a key regulator of AQP4 polarized distribution in astrocytic endfeet after stroke: M23 overexpression corrects AQP4 mis-localization while M1 overexpression exacerbates edema and motor dysfunction. SNTA1 (syntrophin alpha 1) overexpression enhances AQP4 polarity by modulating AQP4 isoform expression; AQP4 inhibition with TGN-020 restores polarized AQP4 in astrocyte end-feet and improves glymphatic function.","method":"tMCAO mouse model, viral vectors for AQP4 isoforms, SNTA1 overexpression, TGN-020 AQP4 antagonist, MRI glymphatic tracer, western blot, q-PCR, immunofluorescence, TEM, behavioral tests, transcriptomic and metabolomic analyses","journal":"Journal of advanced research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — viral isoform overexpression with functional stroke readouts, SNTA1 mechanistic validation, multiple orthogonal methods; single lab study","pmids":["40403843"],"is_preprint":false},{"year":2008,"finding":"AQP4 is a substrate for ubiquitin-dependent proteasomal degradation in the retina; AQP4 was detected in affinity-purified ubiquitinated proteins using an S5a column. Elevated IOP increased ubiquitination in retinal extracts (correlating with decreased AQP4) but decreased ubiquitination in optic nerve extracts (correlating with increased AQP4 in optic nerve astrocytes).","method":"S5a affinity column purification of ubiquitinated proteins, western blot, Q-PCR, immunohistochemistry in rat retinal injury models (Morrison IOP model and intravitreal endothelin-1)","journal":"Molecular vision","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical demonstration of AQP4 ubiquitination via affinity purification; two independent injury models; single lab","pmids":["18836575"],"is_preprint":false},{"year":2024,"finding":"AQP4 knockout in astrocytes activates autophagy, reduces neuroinflammation and cognitive impairment in sepsis-associated encephalopathy. Mechanistically, AQP4 knockout reduces intracellular Ca2+ accumulation by downregulating Nav1.6 channel activity in astrocytes, which activates PPAR-γ signaling to promote autophagy.","method":"CLP sepsis mouse model, AQP4 knockout, LPS-treated astrocytes in vitro, intracellular Ca2+ measurement, Nav1.6 channel activity assay, PPAR-γ signaling analysis, autophagy markers, behavioral tests","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic AQP4 knockout with mechanistic pathway delineation in vivo and in vitro; single lab, multiple functional readouts","pmids":["36922751"],"is_preprint":false},{"year":2017,"finding":"B cells endogenously express AQP4 upon activation with anti-CD40 and IL-21, and can present self-AQP4 to AQP4-specific T cells. Thymic B cells (which emulate the CD40-stimulated transcriptome including AQP4 expression in both mice and humans) efficiently delete AQP4-reactive thymocytes from the TCR repertoire. Genetic ablation of Aqp4 specifically in B cells rescues AQP4-specific TCRs despite sufficient AQP4 expression in medullary thymic epithelial cells, demonstrating B-cell-dependent (not just mTEC-dependent) central tolerance to AQP4.","method":"B-cell conditional Aqp4 knockout, T cell receptor repertoire analysis, thymic B cell transcriptomics, anti-CD40/IL-21 stimulation of B cells, AQP4-specific T cell challenge, germinal center assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific conditional knockout with TCR repertoire and functional validation; multiple orthogonal methods; high-impact peer-reviewed study","pmids":["38383779"],"is_preprint":false},{"year":2015,"finding":"Genistein promotes AQP4 gene transcription in intestinal cells via PKA-mediated CREB phosphorylation (cAMP/PKA/CREB signaling pathway), reversing the downregulation of AQP4 caused by rotavirus infection in Caco-2 cells.","method":"RT-PCR, western blot, CREB phosphorylation assay, PKA activity assay (PepTag), genistein dose-response in Caco-2 cells infected with rotavirus","journal":"Archives of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct pharmacological pathway activation with CREB phosphorylation readout; single lab, single cell line model","pmids":["25877820"],"is_preprint":false},{"year":2020,"finding":"In hippocampal astrocytes, hypoxia-exposed microglia release TNF-α and IL-6, which upregulate AQP4 expression in astrocytes through p38 MAPK and NF-κB signaling pathways. Co-culture of hypoxia-exposed astrocytes and microglia showed AQP4 upregulation in astrocytes that was prevented by p38 inhibitor, NF-κB inhibitor, or puerarin.","method":"Astrocyte-microglia co-culture under hypoxia, p38 MAPK inhibitor, NF-κB inhibitor, ELISA for cytokines, western blot for AQP4 and signaling molecules, hypobaric rat model","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-culture mechanistic experiment with pharmacological inhibitors identifying paracrine signaling pathway; in vivo validation; single lab","pmids":["29054452"],"is_preprint":false}],"current_model":"AQP4 is a water-selective channel with six transmembrane domains that assembles as tetramers and further organizes into supramolecular orthogonal arrays of particles (OAPs) driven by the M23 isoform; OAP formation depends on residue A25 and is required for polarized perivascular localization in astrocytic endfeet, where AQP4 surface abundance is regulated by vesicular trafficking, the SNX27-retromer recycling pathway (preventing lysosomal degradation via β-dystroglycan anchoring), and post-translational ubiquitination; transcription is controlled by NFAT5 and NF-κB/p65 downstream of osmotic and inflammatory stimuli, with translational control mediated by the RNA helicase DDX17; AQP4 phosphorylation by LRRK2 causes depolarization and glymphatic dysfunction, while Per2 maintains polarity through interaction with α-dystrobrevin; functionally, AQP4-mediated water flux drives TRPV4 channel activation for calcium-dependent volume regulation in glia, and the M23/M1 isoform ratio controls OAP assembly that in turn determines whether glioma cells undergo apoptosis or adopt an invasive phenotype."},"narrative":{"mechanistic_narrative":"AQP4 is the principal water-selective channel of astrocytes and related epithelia, where it governs transmembrane water flux and the structural organization of perivascular membrane domains [PMID:8537439, PMID:8617713]. Unlike AQP1, AQP4 adopts a six-transmembrane topology with cytoplasmic termini and N-glycosylation at N131, and forms an aqueous pore whose conductance depends on residues flanking its NPA motifs; dominant-negative tryptophan substitutions show its monomers interact functionally [PMID:7541239, PMID:8555225]. AQP4 monomers assemble into tetramers, and the M23 isoform drives further aggregation into supramolecular orthogonal arrays of particles (OAPs), with the M1/M23 ratio setting OAP extent [PMID:8617713, PMID:24118484]. OAP integrity, dependent on residue A25, is required for the polarized perivascular localization of AQP4 at astrocytic endfeet and is neuroprotective in edema models [PMID:36100398], and the M23/M1 balance also dictates whether glioma cells undergo apoptosis or adopt a migratory, MMP-9-high phenotype through C-terminal proline-dependent actin remodeling [PMID:30877104, PMID:40403843]. Surface abundance and polarity are set by multiple post-transcriptional routes: SNX27-retromer recycling rescues endocytosed AQP4 from lysosomal degradation [PMID:34002021], MMP-9 cleavage of β-dystroglycan triggers AQP4 endocytosis [PMID:38512439, PMID:38421470], ubiquitin-dependent proteasomal turnover degrades AQP4 [PMID:18836575], the RNA helicase DDX17 represses AQP4 translation [PMID:34038017], and scaffolding through α-syntrophin, SNTA1, and the circadian protein Per2 (via α-dystrobrevin) directs perivascular targeting [PMID:38077948, PMID:37802998, PMID:40403843]. AQP4 transcription is induced by NFAT5 under osmotic stress and by NF-κB/p65 downstream of inflammatory TNF-α signaling [PMID:23180003, PMID:35260880]. Functionally, AQP4-driven water influx accelerates TRPV4-mediated calcium entry for glial volume regulation [PMID:26424896], and AQP4 polarity controls glymphatic clearance, which is disrupted when LRRK2 phosphorylates AQP4 [PMID:38296953].","teleology":[{"year":1995,"claim":"Establishing where AQP4 resides and that its tissue distribution matches orthogonal arrays of particles seeded the hypothesis that AQP4 is itself the OAP-forming protein.","evidence":"Immunogold EM and immunolocalization across rat astrocytes, ependyma, muscle, kidney, and glandular epithelia","pmids":["8537439"],"confidence":"High","gaps":["Co-localization was correlative and did not prove AQP4 alone suffices to form OAPs","Functional role of OAPs in water transport not addressed"]},{"year":1995,"claim":"Determining AQP4's membrane topology distinguished it from AQP1 and defined its biosynthetic insertion and glycosylation, providing the structural framework for later pore and assembly studies.","evidence":"Cell-free translation with ER microsomes, protease protection, glycosylation mapping, and oocyte expression of chimeras","pmids":["7541239"],"confidence":"High","gaps":["Topology determined in vitro and in oocytes, not native astrocytes","Did not address oligomerization or OAP assembly"]},{"year":1996,"claim":"Heterologous expression proved a single aquaporin is sufficient to form OAPs and that this property is AQP4-specific, settling the identity of the OAP protein.","evidence":"Stable CHO transfection with freeze-fracture EM, with AQP1 as negative control","pmids":["8617713"],"confidence":"High","gaps":["Isoform requirement (M1 vs M23) for OAP assembly not yet resolved","Physiological consequence of OAPs unaddressed"]},{"year":1996,"claim":"Mutagenesis mapped the residues lining the water pore and showed dominant-negative behavior, establishing that AQP4 functions as an interacting oligomer rather than independent monomers.","evidence":"Site-directed mutagenesis with oocyte osmotic water permeability and HgCl2 dose-response assays","pmids":["8555225"],"confidence":"High","gaps":["Atomic structure of the pore not determined","Link between oligomerization and OAP suprastructure not made"]},{"year":2013,"claim":"Defining the M23-driven tetramer-to-OAP hierarchy and its M1/M23 control connected AQP4 supramolecular structure to its clinical role as the NMO autoantigen.","evidence":"Cell-based assays, complement cytotoxicity assays, and isoform-ratio manipulation, including review synthesis","pmids":["24118484","24260168"],"confidence":"Medium","gaps":["Quantitative determinants of in vivo M1/M23 ratio not defined","Mechanism by which OAP geometry enhances IgG avidity not resolved structurally"]},{"year":2013,"claim":"Linking AQP4 surface abundance to vesicle mobility under osmotic and cAMP stimulation introduced regulated trafficking as a determinant of channel availability.","evidence":"Live-cell vesicle imaging and membrane AQP4 quantification in rat astrocytes under osmotic and pharmacological stimulation","pmids":["23505074"],"confidence":"Medium","gaps":["Trafficking machinery (motors, adaptors) not identified","Causality between vesicle mobility and membrane abundance correlative"]},{"year":2012,"claim":"Identifying NFAT5 as a direct promoter-binding activator established the transcriptional arm of osmotic AQP4 induction.","evidence":"ChIP, luciferase reporter, siRNA knockdown, and in vivo kainic acid edema model","pmids":["23180003"],"confidence":"High","gaps":["Upstream osmosensing signaling to NFAT5 not delineated","Interaction with other promoter factors unaddressed"]},{"year":2015,"claim":"Reciprocal genetic and oocyte experiments showed AQP4 water influx accelerates TRPV4 calcium entry, defining a functional coupling for glial volume regulation.","evidence":"Trpv4-/- and Aqp4-/- mice, calcium imaging, oocyte co-expression with osmotic matching, and pharmacology","pmids":["26424896"],"confidence":"High","gaps":["Physical proximity/scaffolding between AQP4 and TRPV4 not structurally defined","Downstream effectors of the calcium signal not fully mapped"]},{"year":2008,"claim":"Demonstrating AQP4 as a substrate of ubiquitin-dependent degradation, modulated by intraocular pressure, established proteostatic control of AQP4 levels.","evidence":"S5a affinity purification of ubiquitinated proteins with retinal injury models","pmids":["18836575"],"confidence":"Medium","gaps":["E3 ligase responsible not identified","Ubiquitination sites on AQP4 not mapped"]},{"year":2017,"claim":"Showing B cells express and present AQP4 to delete autoreactive thymocytes revealed an unexpected role for AQP4 in B-cell-dependent central tolerance.","evidence":"B-cell conditional Aqp4 knockout with TCR repertoire analysis and thymic B-cell transcriptomics","pmids":["38383779"],"confidence":"High","gaps":["Relation between this tolerance mechanism and CNS AQP4 channel function not connected","Why AQP4 is induced in activated B cells unexplained"]},{"year":2019,"claim":"Identifying AQP4 as a SNX27-retromer cargo and an isoform-dependent determinant of glioma fate connected recycling and aggregation state to AQP4 abundance and cell behavior.","evidence":"Co-IP, SNX27 knockdown/overexpression rescue, lysosomal block, Kidins220 mouse, and isoform-selective glioma expression with proline mutagenesis","pmids":["34002021","30877104"],"confidence":"High","gaps":["Direct binding interface between AQP4 and SNX27 not mapped","How OAP aggregation state mechanically couples to F-actin not resolved"]},{"year":2020,"claim":"Connexin deletion and microglial cytokine experiments tied astrocytic coupling and paracrine inflammatory signaling to AQP4 isoform composition and expression.","evidence":"Cx43/Cx30 double-knockout immunogold and isoform western blot; astrocyte-microglia hypoxia co-culture with p38/NF-κB inhibitors","pmids":["32046059","29054452"],"confidence":"Medium","gaps":["Mechanism linking gap junction coupling to isoform-specific AQP4 changes unclear","Direct vs indirect transcriptional effects of cytokines not separated"]},{"year":2021,"claim":"The M23-null model revealed translational control of AQP4 and identified DDX17 as a negative regulator and PTBP1 as a positive one, adding RNA-binding control to AQP4 regulation.","evidence":"CRISPR M23-null mouse, mRNA-protein pulldown with mass spectrometry, DDX17 knockdown, and astrocyte swelling assays","pmids":["34038017"],"confidence":"High","gaps":["DDX17 binding site on AQP4 mRNA not mapped","Signals controlling RBP recruitment unknown"]},{"year":2022,"claim":"An OAP-disrupting A25Q knock-in proved that supramolecular structure, independent of expression level, is required for polarized endfeet localization and modulates edema outcome.","evidence":"AQP4-A25Q knock-in mouse with BN-PAGE, STORM, immunogold EM, and edema/MCAO models; plus stroke-associated AQP4ex loss analysis","pmids":["36100398","35163040"],"confidence":"High","gaps":["Molecular anchor reading OAP geometry for polarized targeting not identified","Causal role of AQP4ex in OAP stability remains correlative"]},{"year":2022,"claim":"Defining TNF-α/NF-κB-p65 promoter binding established the inflammatory transcriptional pathway controlling AQP4 and astrocyte edema.","evidence":"Luciferase reporter, ChIP, NF-κB inhibitor, and p65 siRNA in astrocytes","pmids":["35260880"],"confidence":"Medium","gaps":["Interaction with osmotic NFAT5 pathway not addressed","p65 binding site coordinates not finely mapped"]},{"year":2023,"claim":"Identifying AQP4ex/α-syntrophin interactions and Per2/α-dystrobrevin coupling clarified how scaffolding and circadian inputs direct perivascular AQP4 polarity.","evidence":"AQP4x dose-modulating transgenic lines with EM/MRI; Per2-Dtna Co-IP and CUMS/melatonin 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mice.","date":"2023","source":"Journal of neuroimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/37210799","citation_count":17,"is_preprint":false},{"pmid":"38802927","id":"PMC_38802927","title":"NHH promotes Sepsis-associated Encephalopathy with the expression of AQP4 in astrocytes through the gut-brain Axis.","date":"2024","source":"Journal of neuroinflammation","url":"https://pubmed.ncbi.nlm.nih.gov/38802927","citation_count":16,"is_preprint":false},{"pmid":"24582793","id":"PMC_24582793","title":"Association of rs2075575 and rs9951307 polymorphisms of AQP-4 gene with leukoaraiosis.","date":"2014","source":"Journal of stroke and cerebrovascular diseases : the official journal of National Stroke Association","url":"https://pubmed.ncbi.nlm.nih.gov/24582793","citation_count":16,"is_preprint":false},{"pmid":"36819717","id":"PMC_36819717","title":"Moxibustion improves hypothalamus Aqp4 polarization in APP/PS1 mice: Evidence from spatial transcriptomics.","date":"2023","source":"Frontiers 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Bulky tryptophan substitutions at G72 or A188 abolish water transport and exert a dominant-negative effect, indicating AQP4 monomers interact functionally.\",\n      \"method\": \"Site-directed mutagenesis, Xenopus oocyte expression, osmotic water permeability assay (Pf), HgCl2 dose-response, quantitative immunofluorescence\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis combined with functional assays in oocytes; dominant-negative result confirms monomer-monomer interaction; multiple mutants tested\",\n      \"pmids\": [\"8555225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AQP4 surface expression in astrocytes is regulated by vesicular trafficking; AQP4e isoform localizes to vesicles whose mobility correlates with AQP4 plasma membrane abundance. Hypoosmotic stimulation (mimicking brain edema) transiently reduces vesicle mobility and transiently changes AQP4 plasma membrane localization; increased cytosolic cAMP (reactive astrocyte model) increases AQP4 surface expression. Actin rearrangement accompanies reactive astrocyte stimulation and vimentin depolymerization accompanies hypoosmotic conditions.\",\n      \"method\": \"Live-cell imaging of vesicle mobility in cultured rat astrocytes, plasma membrane AQP4 quantification, cytoskeletal analysis under pharmacological and osmotic stimulation\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct live imaging of vesicle dynamics correlated with membrane localization; single lab, two complementary methods\",\n      \"pmids\": [\"23505074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AQP4 monomers form tetramers in membranes, and M23-AQP4 tetramers further aggregate into supramolecular orthogonal arrays of particles (OAPs); the M1/M23 isoform ratio controls the extent of OAP assembly, and AQP4-IgG binding and complement-dependent cytotoxicity in NMO are greatly enhanced by OAP formation.\",\n      \"method\": \"Cell-based assays, complement cytotoxicity assays, isoform expression studies reviewed from multiple independent experiments\",\n      \"journal\": \"Brain pathology (Zurich, Switzerland)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic conclusions drawn from multiple referenced experimental studies; review synthesis, confidence limited by absence of primary experimental detail in abstract\",\n      \"pmids\": [\"24118484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"AQP4-IgG diagnostic sensitivity is highest with M23-AQP4 expressing cells (97.5%) versus M1-AQP4 (27.5%) in cell-based assays (CBA); the nucleotide at position -3 of the AUG of M1 greatly affects the M1/M23 protein ratio and NMO-IgG binding. An N-terminal fluorescent tag on M23-AQP4 disrupts AQP4 suprastructures and reduces test sensitivity.\",\n      \"method\": \"Cell-based assay (CBA) with systematic variation of AQP4 isoform, translation initiation signals, fluorescent tag position; NMO patient serum testing\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct experimental manipulation of AQP4 isoform ratios and structural tags with functional readout in CBA; single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"24260168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"AQP4 and TRPV4 colocalize in Müller glial endfeet and radial processes in mouse retina. AQP4-mediated water influx drives TRPV4-mediated calcium entry during hypo-osmotic swelling; conversely, calcium entry through TRPV4 modulates volume regulation and Aqp4 gene expression. In Xenopus oocytes co-expressing both channels, when swelling rate was osmotically matched, TRPV4 activation became independent of AQP4, demonstrating that AQP4's contribution is specifically through accelerating water influx.\",\n      \"method\": \"Genetic ablation (Trpv4-/- and Aqp4-/- mice), live calcium imaging, cell volume measurements, Xenopus oocyte co-expression, pharmacological TRPV4 agonist/antagonist studies, gene expression analysis\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic knockouts, heterologous oocyte reconstitution, and pharmacological validation across multiple labs; osmotic matching experiment directly establishes mechanism\",\n      \"pmids\": [\"26424896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"AQP4 aggregation state determines glioma cell fate: M23-AQP4 (OAP-forming isoform) triggers F-actin cytoskeletal changes and promotes apoptosis, while M1-AQP4 (tetramer-only) increases cell migration and MMP-9 activity. Two C-terminal proline residues (Pro254 and Pro296) mediate the relationship between AQP4 aggregation state and the actin cytoskeleton.\",\n      \"method\": \"Selective isoform expression in glioma cell lines, F-actin imaging, apoptosis assays, cell migration/invasion assays, MMP-9 activity assay, proline mutagenesis\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-selective expression with multiple functional readouts and mutagenesis; single lab study\",\n      \"pmids\": [\"30877104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"AQP4 is a novel cargo of the SNX27-retromer complex, which recycles endocytosed AQP4 back to the cell surface and prevents lysosomal degradation. Kidins220 deficiency causes SNX27-retromer downregulation leading to AQP4 lysosomal degradation; SNX27 silencing decreases AQP4 levels in wild-type astrocytes, while SNX27 overexpression restores AQP4 in Kidins220-deficient astrocytes.\",\n      \"method\": \"Co-immunoprecipitation, SNX27 knockdown and overexpression in astrocytes, lysosome inhibitor (bafilomycin) rescue, mouse genetic model (Kidins220 deficient), human iNPH patient tissue analysis\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional rescue experiments (SNX27 OE restores AQP4), pharmacological lysosomal block, human tissue validation, and mouse model; multiple orthogonal methods\",\n      \"pmids\": [\"34002021\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In M23-AQP4 null (CRISPR/Cas9) mouse spinal cord, M1-AQP4 protein is drastically reduced without changes in M1-AQP4 transcription, splicing, or protein degradation, indicating translational control. mRNA-protein pulldown and quantitative mass spectrometry identified AQP4 mRNA-binding proteins (RBPs): polypyrimidine tract binding protein 1 (PTBP1, a positive translational regulator) shows increased interaction with AQP4 mRNA in M23-null, and RNA helicase DDX17 shows decreased interaction. DDX17 knockdown upregulates AQP4 protein and increases astrocyte swelling without affecting mRNA levels, identifying DDX17 as a negative translational regulator of AQP4.\",\n      \"method\": \"CRISPR/Cas9 M23-null mouse model, mRNA-protein pulldown, quantitative mass spectrometry, DDX17 siRNA knockdown, astrocyte primary culture swelling assay, western blot, RT-PCR\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution-level identification of RBPs by mass spectrometry combined with loss-of-function knockdown; genetic mouse model validates in vivo relevance; multiple orthogonal methods\",\n      \"pmids\": [\"34038017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Deletion of astrocytic connexins Cx43 and Cx30 causes substantial reduction of perivascular AQP4, downregulation of total AQP4 protein and mRNA, and isoform-specific effects: M23-AQP4 is reduced while M1-AQP4 and the AQP4ex isoform are increased, demonstrating a complex interdependence between astrocytic gap junction coupling and AQP4 membrane localization and isoform composition.\",\n      \"method\": \"Quantitative immunogold cytochemistry, isoform-specific western blot, mRNA analysis in connexin Cx43/Cx30 double knockout mice\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative immunogold EM with genetic knockout model; single lab, two orthogonal quantitative methods\",\n      \"pmids\": [\"32046059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"An AQP4-A25Q point mutation that depolymerizes OAPs (confirmed by blue native PAGE, super-resolution imaging, and immunogold EM) without affecting total AQP4 mRNA or protein expression reduces polarized perivascular expression of AQP4 at astrocytic endfeet and is neuroprotective in cerebral edema models (water intoxication and MCAO/reperfusion), demonstrating that OAP structure is required for polarized endfeet localization.\",\n      \"method\": \"Transgenic knock-in mouse (AQP4-A25Q), blue native PAGE, super-resolution imaging, immunogold EM, brain water content measurement, MCAO stroke model, behavioral scoring\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — genetic knock-in with point mutation, confirmed by three independent structural methods (BN-PAGE, STORM, immunogold EM), functional validation in two disease models\",\n      \"pmids\": [\"36100398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Disassembly of supramolecular AQP4 complexes and loss of AQP4 from astrocytic endfoot membranes occurs at the border zone one week after ischemic stroke, mechanistically coupled to downregulation of the AQP4ex (readthrough) isoform, suggesting AQP4ex stabilizes OAPs at perivascular endfeet.\",\n      \"method\": \"Immunofluorescence and confocal analysis of murine stroke model at defined time points post-ischemia; isoform-specific analysis\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment with isoform-specific analysis; correlative mechanistic link between AQP4ex and OAP stability not yet established causally; single lab\",\n      \"pmids\": [\"35163040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The AQP4ex (readthrough) isoform preferentially localizes around the blood-brain barrier through interaction with the scaffolding protein α-syntrophin. Increasing AQP4ex dose enhances perivascular localization of both α-syntrophin and AQP4 without changing total protein expression. Complete AQP4x loss (NoXHom) alters BBB integrity (increased endothelial budding vesicles, leakier BBB by MRI). AQP4x plays a measurable role in recruiting structural/functional support proteins to blood vessels.\",\n      \"method\": \"AllX and NoX transgenic mouse lines (quantitative AQP4x modulation), immunofluorescence, electron microscopy, MRI, α-syntrophin colocalization analysis\",\n      \"journal\": \"Frontiers in cellular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic dose-response model with two complementary knockin/knockout lines; EM and MRI for BBB integrity; single lab\",\n      \"pmids\": [\"38077948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"LRRK2 directly interacts with and phosphorylates AQP4 in vitro and in vivo. LRRK2 R1441G-mediated AQP4 phosphorylation induces AQP4 depolarization and disrupts glymphatic clearance of IFNγ, leading to neuroinflammation and dopaminergic neurodegeneration. LRRK2 inhibition restores AQP4 polarity and improves glymphatic function.\",\n      \"method\": \"In vitro kinase assay, in vivo phosphorylation in transgenic mice, AQP4 polarization imaging, glymphatic tracer studies, LRRK2 inhibitor treatment, IFNγ clearance measurement\",\n      \"journal\": \"NPJ Parkinson's disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro and in vivo kinase assay establishing phosphorylation, functional rescue with inhibitor, and glymphatic readthrough tracer studies; multiple orthogonal methods\",\n      \"pmids\": [\"38296953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NFAT5 directly binds the AQP4 gene promoter (between -49 and -38 bp) and is required for transcriptional upregulation of AQP4 in astrocytes under swelling conditions (ammonia treatment). NFAT5 siRNA silencing significantly reduces AQP4 expression, and ChIP assay shows increased NFAT5 binding to the AQP4 promoter after ammonia treatment.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), dual-luciferase reporter assay, siRNA knockdown, in vivo kainic acid brain edema model, immunohistochemistry\",\n      \"journal\": \"Cellular and molecular neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct promoter binding demonstrated by ChIP and luciferase reporter, causal role confirmed by siRNA knockdown, in vivo validation; multiple orthogonal methods\",\n      \"pmids\": [\"23180003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TNF-α activates the NF-κB pathway in astrocytes, causing p65 protein to bind the AQP4 gene promoter region, enhancing AQP4 transcription and causing astrocyte edema and reduced viability. The NF-κB inhibitor BAY 11-7082 blocks this effect, and p65 siRNA reduces AQP4 expression and improves astrocyte viability.\",\n      \"method\": \"Dual-luciferase reporter assay, chromatin immunoprecipitation (ChIP), NF-κB pathway inhibitor (BAY 11-7082), p65 siRNA, western blot, qPCR, cell viability assay (CCK-8)\",\n      \"journal\": \"Bioscience reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct promoter binding by ChIP and luciferase reporter, with pharmacological and genetic loss-of-function rescue; single lab study\",\n      \"pmids\": [\"35260880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AQP4 endocytosis and lysosomal degradation is regulated by MMP-9 cleavage of β-dystroglycan (β-DG): MMP-9 cleaves β-DG, disrupting its anchorage of AQP4 on the astrocyte plasma membrane, leading to AQP4 endocytosis. Bafilomycin A1 (lysosome inhibitor) reverses AQP4 downregulation in diabetic mice; MMP-9/β-DG inhibition restores AQP4 surface expression and partially alleviates diabetic cognitive dysfunction.\",\n      \"method\": \"Diabetic mouse model (STZ), lysosome inhibitor rescue (bafilomycin A1), MMP-9 inhibition, β-DG cleavage analysis, western blot, immunofluorescence, behavioral tests\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological rescue of lysosomal degradation, β-DG cleavage mechanistic link established, in vivo model; single lab, MMP-9/β-DG pathway previously known\",\n      \"pmids\": [\"38512439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MMP-9 activation downstream of oxidative stress in intracerebral hemorrhage cleaves β-dystroglycan, reducing AQP4 polarity. Edaravone (oxygen free radical scavenger) downregulates MMP-9 and upregulates β-DG, maintaining AQP4 polarity and reducing brain edema. MMP-9 inhibitor similarly maintains AQP4 polarity, confirming the OS/MMP9/β-DG/AQP4 pathway.\",\n      \"method\": \"Autologous blood ICH mouse model, edaravone and MMP9-inh treatment, immunofluorescence, western blot, ELISA, Evans blue permeability, brain water content, intracisternal tracer infusion\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and specific inhibitor experiments in vivo establishing pathway; single lab; convergent evidence from two independent inhibitors\",\n      \"pmids\": [\"38421470\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The circadian protein Per2 directs AQP4 perivascular polarization in astrocytes through interactions with α-dystrobrevin (Dtna), a subunit of the AQP4 anchoring complex. Per2 expression negatively correlates with AQP4 polarization; CUMS mice with disrupted circadian rhythms show impaired AQP4 polarization, which is restored by melatonin treatment that normalizes Per2 expression.\",\n      \"method\": \"Co-immunoprecipitation of Per2 with Dtna in primary cultured astrocytes, CUMS mouse model, melatonin treatment, EEG sleep analysis, AQP4 polarization imaging, circadian protein expression analysis\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishes Per2-Dtna interaction in primary astrocytes; in vivo rescue experiment with melatonin; single lab\",\n      \"pmids\": [\"37802998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"AQP4-M23 isoform is a key regulator of AQP4 polarized distribution in astrocytic endfeet after stroke: M23 overexpression corrects AQP4 mis-localization while M1 overexpression exacerbates edema and motor dysfunction. SNTA1 (syntrophin alpha 1) overexpression enhances AQP4 polarity by modulating AQP4 isoform expression; AQP4 inhibition with TGN-020 restores polarized AQP4 in astrocyte end-feet and improves glymphatic function.\",\n      \"method\": \"tMCAO mouse model, viral vectors for AQP4 isoforms, SNTA1 overexpression, TGN-020 AQP4 antagonist, MRI glymphatic tracer, western blot, q-PCR, immunofluorescence, TEM, behavioral tests, transcriptomic and metabolomic analyses\",\n      \"journal\": \"Journal of advanced research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — viral isoform overexpression with functional stroke readouts, SNTA1 mechanistic validation, multiple orthogonal methods; single lab study\",\n      \"pmids\": [\"40403843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"AQP4 is a substrate for ubiquitin-dependent proteasomal degradation in the retina; AQP4 was detected in affinity-purified ubiquitinated proteins using an S5a column. Elevated IOP increased ubiquitination in retinal extracts (correlating with decreased AQP4) but decreased ubiquitination in optic nerve extracts (correlating with increased AQP4 in optic nerve astrocytes).\",\n      \"method\": \"S5a affinity column purification of ubiquitinated proteins, western blot, Q-PCR, immunohistochemistry in rat retinal injury models (Morrison IOP model and intravitreal endothelin-1)\",\n      \"journal\": \"Molecular vision\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical demonstration of AQP4 ubiquitination via affinity purification; two independent injury models; single lab\",\n      \"pmids\": [\"18836575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"AQP4 knockout in astrocytes activates autophagy, reduces neuroinflammation and cognitive impairment in sepsis-associated encephalopathy. Mechanistically, AQP4 knockout reduces intracellular Ca2+ accumulation by downregulating Nav1.6 channel activity in astrocytes, which activates PPAR-γ signaling to promote autophagy.\",\n      \"method\": \"CLP sepsis mouse model, AQP4 knockout, LPS-treated astrocytes in vitro, intracellular Ca2+ measurement, Nav1.6 channel activity assay, PPAR-γ signaling analysis, autophagy markers, behavioral tests\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic AQP4 knockout with mechanistic pathway delineation in vivo and in vitro; single lab, multiple functional readouts\",\n      \"pmids\": [\"36922751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"B cells endogenously express AQP4 upon activation with anti-CD40 and IL-21, and can present self-AQP4 to AQP4-specific T cells. Thymic B cells (which emulate the CD40-stimulated transcriptome including AQP4 expression in both mice and humans) efficiently delete AQP4-reactive thymocytes from the TCR repertoire. Genetic ablation of Aqp4 specifically in B cells rescues AQP4-specific TCRs despite sufficient AQP4 expression in medullary thymic epithelial cells, demonstrating B-cell-dependent (not just mTEC-dependent) central tolerance to AQP4.\",\n      \"method\": \"B-cell conditional Aqp4 knockout, T cell receptor repertoire analysis, thymic B cell transcriptomics, anti-CD40/IL-21 stimulation of B cells, AQP4-specific T cell challenge, germinal center assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific conditional knockout with TCR repertoire and functional validation; multiple orthogonal methods; high-impact peer-reviewed study\",\n      \"pmids\": [\"38383779\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Genistein promotes AQP4 gene transcription in intestinal cells via PKA-mediated CREB phosphorylation (cAMP/PKA/CREB signaling pathway), reversing the downregulation of AQP4 caused by rotavirus infection in Caco-2 cells.\",\n      \"method\": \"RT-PCR, western blot, CREB phosphorylation assay, PKA activity assay (PepTag), genistein dose-response in Caco-2 cells infected with rotavirus\",\n      \"journal\": \"Archives of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct pharmacological pathway activation with CREB phosphorylation readout; single lab, single cell line model\",\n      \"pmids\": [\"25877820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In hippocampal astrocytes, hypoxia-exposed microglia release TNF-α and IL-6, which upregulate AQP4 expression in astrocytes through p38 MAPK and NF-κB signaling pathways. Co-culture of hypoxia-exposed astrocytes and microglia showed AQP4 upregulation in astrocytes that was prevented by p38 inhibitor, NF-κB inhibitor, or puerarin.\",\n      \"method\": \"Astrocyte-microglia co-culture under hypoxia, p38 MAPK inhibitor, NF-κB inhibitor, ELISA for cytokines, western blot for AQP4 and signaling molecules, hypobaric rat model\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-culture mechanistic experiment with pharmacological inhibitors identifying paracrine signaling pathway; in vivo validation; single lab\",\n      \"pmids\": [\"29054452\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"AQP4 is a water-selective channel with six transmembrane domains that assembles as tetramers and further organizes into supramolecular orthogonal arrays of particles (OAPs) driven by the M23 isoform; OAP formation depends on residue A25 and is required for polarized perivascular localization in astrocytic endfeet, where AQP4 surface abundance is regulated by vesicular trafficking, the SNX27-retromer recycling pathway (preventing lysosomal degradation via β-dystroglycan anchoring), and post-translational ubiquitination; transcription is controlled by NFAT5 and NF-κB/p65 downstream of osmotic and inflammatory stimuli, with translational control mediated by the RNA helicase DDX17; AQP4 phosphorylation by LRRK2 causes depolarization and glymphatic dysfunction, while Per2 maintains polarity through interaction with α-dystrobrevin; functionally, AQP4-mediated water flux drives TRPV4 channel activation for calcium-dependent volume regulation in glia, and the M23/M1 isoform ratio controls OAP assembly that in turn determines whether glioma cells undergo apoptosis or adopt an invasive phenotype.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"AQP4 is the principal water-selective channel of astrocytes and related epithelia, where it governs transmembrane water flux and the structural organization of perivascular membrane domains [#0, #2]. Unlike AQP1, AQP4 adopts a six-transmembrane topology with cytoplasmic termini and N-glycosylation at N131, and forms an aqueous pore whose conductance depends on residues flanking its NPA motifs; dominant-negative tryptophan substitutions show its monomers interact functionally [#1, #3]. AQP4 monomers assemble into tetramers, and the M23 isoform drives further aggregation into supramolecular orthogonal arrays of particles (OAPs), with the M1/M23 ratio setting OAP extent [#2, #5]. OAP integrity, dependent on residue A25, is required for the polarized perivascular localization of AQP4 at astrocytic endfeet and is neuroprotective in edema models [#12], and the M23/M1 balance also dictates whether glioma cells undergo apoptosis or adopt a migratory, MMP-9-high phenotype through C-terminal proline-dependent actin remodeling [#8, #21]. Surface abundance and polarity are set by multiple post-transcriptional routes: SNX27-retromer recycling rescues endocytosed AQP4 from lysosomal degradation [#9], MMP-9 cleavage of \\u03b2-dystroglycan triggers AQP4 endocytosis [#18, #19], ubiquitin-dependent proteasomal turnover degrades AQP4 [#22], the RNA helicase DDX17 represses AQP4 translation [#10], and scaffolding through \\u03b1-syntrophin, SNTA1, and the circadian protein Per2 (via \\u03b1-dystrobrevin) directs perivascular targeting [#14, #20, #21]. AQP4 transcription is induced by NFAT5 under osmotic stress and by NF-\\u03baB/p65 downstream of inflammatory TNF-\\u03b1 signaling [#16, #17]. Functionally, AQP4-driven water influx accelerates TRPV4-mediated calcium entry for glial volume regulation [#7], and AQP4 polarity controls glymphatic clearance, which is disrupted when LRRK2 phosphorylates AQP4 [#15].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Establishing where AQP4 resides and that its tissue distribution matches orthogonal arrays of particles seeded the hypothesis that AQP4 is itself the OAP-forming protein.\",\n      \"evidence\": \"Immunogold EM and immunolocalization across rat astrocytes, ependyma, muscle, kidney, and glandular epithelia\",\n      \"pmids\": [\"8537439\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Co-localization was correlative and did not prove AQP4 alone suffices to form OAPs\", \"Functional role of OAPs in water transport not addressed\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Determining AQP4's membrane topology distinguished it from AQP1 and defined its biosynthetic insertion and glycosylation, providing the structural framework for later pore and assembly studies.\",\n      \"evidence\": \"Cell-free translation with ER microsomes, protease protection, glycosylation mapping, and oocyte expression of chimeras\",\n      \"pmids\": [\"7541239\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Topology determined in vitro and in oocytes, not native astrocytes\", \"Did not address oligomerization or OAP assembly\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Heterologous expression proved a single aquaporin is sufficient to form OAPs and that this property is AQP4-specific, settling the identity of the OAP protein.\",\n      \"evidence\": \"Stable CHO transfection with freeze-fracture EM, with AQP1 as negative control\",\n      \"pmids\": [\"8617713\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Isoform requirement (M1 vs M23) for OAP assembly not yet resolved\", \"Physiological consequence of OAPs unaddressed\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Mutagenesis mapped the residues lining the water pore and showed dominant-negative behavior, establishing that AQP4 functions as an interacting oligomer rather than independent monomers.\",\n      \"evidence\": \"Site-directed mutagenesis with oocyte osmotic water permeability and HgCl2 dose-response assays\",\n      \"pmids\": [\"8555225\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of the pore not determined\", \"Link between oligomerization and OAP suprastructure not made\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defining the M23-driven tetramer-to-OAP hierarchy and its M1/M23 control connected AQP4 supramolecular structure to its clinical role as the NMO autoantigen.\",\n      \"evidence\": \"Cell-based assays, complement cytotoxicity assays, and isoform-ratio manipulation, including review synthesis\",\n      \"pmids\": [\"24118484\", \"24260168\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative determinants of in vivo M1/M23 ratio not defined\", \"Mechanism by which OAP geometry enhances IgG avidity not resolved structurally\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linking AQP4 surface abundance to vesicle mobility under osmotic and cAMP stimulation introduced regulated trafficking as a determinant of channel availability.\",\n      \"evidence\": \"Live-cell vesicle imaging and membrane AQP4 quantification in rat astrocytes under osmotic and pharmacological stimulation\",\n      \"pmids\": [\"23505074\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking machinery (motors, adaptors) not identified\", \"Causality between vesicle mobility and membrane abundance correlative\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identifying NFAT5 as a direct promoter-binding activator established the transcriptional arm of osmotic AQP4 induction.\",\n      \"evidence\": \"ChIP, luciferase reporter, siRNA knockdown, and in vivo kainic acid edema model\",\n      \"pmids\": [\"23180003\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream osmosensing signaling to NFAT5 not delineated\", \"Interaction with other promoter factors unaddressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Reciprocal genetic and oocyte experiments showed AQP4 water influx accelerates TRPV4 calcium entry, defining a functional coupling for glial volume regulation.\",\n      \"evidence\": \"Trpv4-/- and Aqp4-/- mice, calcium imaging, oocyte co-expression with osmotic matching, and pharmacology\",\n      \"pmids\": [\"26424896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physical proximity/scaffolding between AQP4 and TRPV4 not structurally defined\", \"Downstream effectors of the calcium signal not fully mapped\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrating AQP4 as a substrate of ubiquitin-dependent degradation, modulated by intraocular pressure, established proteostatic control of AQP4 levels.\",\n      \"evidence\": \"S5a affinity purification of ubiquitinated proteins with retinal injury models\",\n      \"pmids\": [\"18836575\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase responsible not identified\", \"Ubiquitination sites on AQP4 not mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Showing B cells express and present AQP4 to delete autoreactive thymocytes revealed an unexpected role for AQP4 in B-cell-dependent central tolerance.\",\n      \"evidence\": \"B-cell conditional Aqp4 knockout with TCR repertoire analysis and thymic B-cell transcriptomics\",\n      \"pmids\": [\"38383779\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relation between this tolerance mechanism and CNS AQP4 channel function not connected\", \"Why AQP4 is induced in activated B cells unexplained\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identifying AQP4 as a SNX27-retromer cargo and an isoform-dependent determinant of glioma fate connected recycling and aggregation state to AQP4 abundance and cell behavior.\",\n      \"evidence\": \"Co-IP, SNX27 knockdown/overexpression rescue, lysosomal block, Kidins220 mouse, and isoform-selective glioma expression with proline mutagenesis\",\n      \"pmids\": [\"34002021\", \"30877104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding interface between AQP4 and SNX27 not mapped\", \"How OAP aggregation state mechanically couples to F-actin not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Connexin deletion and microglial cytokine experiments tied astrocytic coupling and paracrine inflammatory signaling to AQP4 isoform composition and expression.\",\n      \"evidence\": \"Cx43/Cx30 double-knockout immunogold and isoform western blot; astrocyte-microglia hypoxia co-culture with p38/NF-\\u03baB inhibitors\",\n      \"pmids\": [\"32046059\", \"29054452\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking gap junction coupling to isoform-specific AQP4 changes unclear\", \"Direct vs indirect transcriptional effects of cytokines not separated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"The M23-null model revealed translational control of AQP4 and identified DDX17 as a negative regulator and PTBP1 as a positive one, adding RNA-binding control to AQP4 regulation.\",\n      \"evidence\": \"CRISPR M23-null mouse, mRNA-protein pulldown with mass spectrometry, DDX17 knockdown, and astrocyte swelling assays\",\n      \"pmids\": [\"34038017\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DDX17 binding site on AQP4 mRNA not mapped\", \"Signals controlling RBP recruitment unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"An OAP-disrupting A25Q knock-in proved that supramolecular structure, independent of expression level, is required for polarized endfeet localization and modulates edema outcome.\",\n      \"evidence\": \"AQP4-A25Q knock-in mouse with BN-PAGE, STORM, immunogold EM, and edema/MCAO models; plus stroke-associated AQP4ex loss analysis\",\n      \"pmids\": [\"36100398\", \"35163040\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular anchor reading OAP geometry for polarized targeting not identified\", \"Causal role of AQP4ex in OAP stability remains correlative\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defining TNF-\\u03b1/NF-\\u03baB-p65 promoter binding established the inflammatory transcriptional pathway controlling AQP4 and astrocyte edema.\",\n      \"evidence\": \"Luciferase reporter, ChIP, NF-\\u03baB inhibitor, and p65 siRNA in astrocytes\",\n      \"pmids\": [\"35260880\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interaction with osmotic NFAT5 pathway not addressed\", \"p65 binding site coordinates not finely mapped\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identifying AQP4ex/\\u03b1-syntrophin interactions and Per2/\\u03b1-dystrobrevin coupling clarified how scaffolding and circadian inputs direct perivascular AQP4 polarity.\",\n      \"evidence\": \"AQP4x dose-modulating transgenic lines with EM/MRI; Per2-Dtna Co-IP and CUMS/melatonin rescue\",\n      \"pmids\": [\"38077948\", \"37802998\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding of AQP4ex to \\u03b1-syntrophin not biochemically resolved\", \"How Per2 mechanistically regulates the anchoring complex unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrating LRRK2 directly phosphorylates AQP4 to cause depolarization linked a Parkinson's-associated kinase to glymphatic dysfunction and neuroinflammation.\",\n      \"evidence\": \"In vitro and in vivo kinase assays, LRRK2 R1441G mice, glymphatic tracer studies, and LRRK2 inhibitor rescue\",\n      \"pmids\": [\"38296953\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"AQP4 phosphosite(s) targeted by LRRK2 not specified\", \"How phosphorylation disrupts OAP/anchoring mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defining the MMP-9/\\u03b2-dystroglycan axis and an AQP4-Nav1.6-PPAR\\u03b3-autophagy circuit expanded the post-translational and downstream signaling control of AQP4 polarity and astrocyte fate.\",\n      \"evidence\": \"Diabetic and ICH models with MMP-9 inhibition, bafilomycin rescue, edaravone; AQP4 knockout with Ca2+/Nav1.6/PPAR-\\u03b3 analysis in sepsis encephalopathy\",\n      \"pmids\": [\"38512439\", \"38421470\", \"36922751\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether \\u03b2-DG cleavage directly releases OAPs vs tetramers not resolved\", \"Causal chain from AQP4 to Nav1.6 regulation incompletely defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Isoform overexpression after stroke confirmed M23 corrects and M1 worsens AQP4 mis-localization, with SNTA1 enhancing polarity, reinforcing isoform balance as a therapeutic lever for glymphatic function.\",\n      \"evidence\": \"tMCAO mouse model with viral AQP4 isoform and SNTA1 overexpression, TGN-020 antagonist, MRI glymphatic tracer, and multi-omics\",\n      \"pmids\": [\"40403843\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which SNTA1 modulates isoform expression not defined\", \"Single-lab stroke-model findings\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple regulatory layers \\u2014 transcriptional, translational, trafficking, scaffolding, phosphorylation, and OAP assembly \\u2014 are integrated into a single quantitative control of perivascular AQP4 polarity, and the atomic structure governing OAP-dependent targeting, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model linking OAP geometry to its anchoring/targeting machinery\", \"No unified hierarchy among the competing regulators of AQP4 surface polarity\", \"Phosphosite and ubiquitination site maps incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [2, 3, 7]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 2, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 9, 18]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [9, 18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [2, 3, 7]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [16, 17]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [9, 12, 21]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [10, 18, 22]}\n    ],\n    \"complexes\": [\n      \"orthogonal arrays of particles (OAPs)\",\n      \"SNX27-retromer complex\",\n      \"dystrophin-associated (\\u03b1-syntrophin/\\u03b1-dystrobrevin/\\u03b2-dystroglycan) anchoring complex\"\n    ],\n    \"partners\": [\n      \"TRPV4\",\n      \"SNX27\",\n      \"DDX17\",\n      \"PTBP1\",\n      \"LRRK2\",\n      \"SNTA1\",\n      \"DTNA\",\n      \"Per2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}