{"gene":"HAX1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1997,"finding":"HAX-1 was identified as a novel intracellular protein that directly associates with HS1 (a substrate of Src family tyrosine kinases) via the amino-terminal region of HS1 and the carboxyl-terminal half of HAX-1; HAX-1 localizes predominantly to mitochondria but also to endoplasmic reticulum and nuclear envelope.","method":"Yeast two-hybrid screening, co-immunoprecipitation, confocal microscopy, deletion mutant analysis","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP in multiple cell lines, deletion mapping of interaction domains, confirmed by colocalization; foundational paper replicated by many subsequent studies","pmids":["9058808"],"is_preprint":false},{"year":2000,"finding":"HAX-1 interacts with the polycystic kidney disease protein PKD2 (but not the closely related PKD2L) and also associates with the F-actin-binding protein cortactin, linking PKD2 to the actin cytoskeleton; PKD2 and HAX-1 colocalize in the cell body and in cellular processes and lamellipodia.","method":"Yeast two-hybrid screen, immunofluorescence colocalization, specificity demonstrated by failure of PKD2L to interact","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid with specificity control, immunofluorescence colocalization; no full reciprocal Co-IP reported in abstract","pmids":["10760273"],"is_preprint":false},{"year":2002,"finding":"KSHV K15 protein interacts with HAX-1 via its C-terminus both in vitro and in vivo; HAX-1 colocalizes with K15 at the ER and mitochondria; HAX-1 can form homodimers in vivo and functions as a potent inhibitor of apoptosis.","method":"Yeast two-hybrid screen, in vitro and in vivo binding assays, immunofluorescence colocalization, apoptosis assays","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid confirmed by in vitro/in vivo interaction assays, homodimerization demonstrated in vivo, functional apoptosis assay","pmids":["11752170"],"is_preprint":false},{"year":2002,"finding":"HAX-1 binds specifically to the 3' untranslated region of vimentin mRNA; HAX-1 and eEF-1gamma form protein complexes that interact with vimentin 3'UTR and can be pulled from HeLa cell extracts using a vimentin 3'UTR RNA affinity column, establishing HAX-1 as an RNA-binding protein.","method":"Yeast three-hybrid assay, in vitro RNA-protein binding, RNA affinity pulldown from cell extracts","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast three-hybrid plus in vitro binding and RNA affinity pulldown; two orthogonal methods in single lab","pmids":["12466525"],"is_preprint":false},{"year":2004,"finding":"HAX-1 is a specific substrate of the mitochondrial serine protease Omi/HtrA2; Omi cleaves HAX-1 both in vitro and in vivo during apoptosis; HAX-1 degradation is an early event occurring while Omi is still confined to mitochondria; inhibition of Omi protease activity prevents HAX-1 degradation and reduces cell death.","method":"In vitro cleavage assay, in vivo cleavage in cells treated with apoptotic stimuli, Omi-specific inhibitor, cell line with catalytically inactive Omi (mnd2 mice-derived)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstituted cleavage assay plus in vivo confirmation plus genetic (mnd2 catalytic mutant) and pharmacological validation; multiple orthogonal methods in one study","pmids":["15371414"],"is_preprint":false},{"year":2004,"finding":"Gα13 physically interacts with HAX-1, and this interaction is required for Gα13-stimulated cell migration; HAX-1 expression reduces actin stress fibers and focal adhesion complexes in Gα13-expressing cells; HAX-1 attenuates Gα13-stimulated RhoA activity while potentiating Rac activity; a quaternary complex of Gα13, HAX-1, Rac, and cortactin was identified; siRNA-mediated silencing of HAX-1 drastically reduces Gα13-mediated cell migration.","method":"Co-immunoprecipitation, siRNA knockdown, cell migration assay, RhoA/Rac activity assays, actin/focal adhesion staining","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP plus loss-of-function (siRNA) with defined migration phenotype plus signaling readouts (RhoA/Rac); multiple orthogonal methods","pmids":["15339924"],"is_preprint":false},{"year":2004,"finding":"HAX-1 binds to BSEP, MDR1, and MDR2 ABC transporters; HAX-1 co-localizes with BSEP and MDR1 at the apical membrane of MDCK cells; RNAi-mediated depletion of HAX-1 increases BSEP levels in the apical membrane by 71% by enhancing retention (not by altering synthesis, modification, or delivery); HAX-1 also interacts with cortactin and participates in BSEP internalization from the apical membrane.","method":"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, RNA interference, pulse-chase labeling, subcellular fractionation, immunofluorescence","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal validation methods (yeast 2-hybrid, GST pulldown, Co-IP, RNAi, pulse-chase) in single rigorous study","pmids":["15159385"],"is_preprint":false},{"year":2006,"finding":"HAX-1 is critical for maintaining the inner mitochondrial membrane potential in myeloid cells; loss-of-function HAX1 mutations (homozygous) cause increased apoptosis in myeloid cells and severe congenital neutropenia.","method":"Positional cloning, germline mutation identification, mitochondrial membrane potential assay, apoptosis assay in patient myeloid cells","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional loss-of-function in human patients with defined cellular phenotype (mitochondrial membrane potential, apoptosis) replicated across multiple pedigrees","pmids":["17187068"],"is_preprint":false},{"year":2006,"finding":"HAX-1 interacts with caspase-9 and inhibits caspase-9 processing in a dose-dependent manner in a cell-free caspase activation assay; HAX-1 overexpression in adult cardiac myocytes protects against apoptosis; on apoptotic stimulation, caspase-9 translocates to mitochondria and colocalizes with HAX-1.","method":"Yeast two-hybrid, cell-free caspase activation assay with recombinant protein, overexpression/siRNA knockdown in cardiac myocytes, immunofluorescence colocalization","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstituted cell-free caspase inhibition assay with recombinant HAX-1 plus cellular overexpression/knockdown studies; single lab but multiple orthogonal methods","pmids":["16857965"],"is_preprint":false},{"year":2006,"finding":"HAX-1 interacts with phospholamban (PLN) via PLN residues 16–22 and HAX-1 residues 203–245; binding affinity ~1 µM measured by surface plasmon resonance; phosphorylation of PLN by PKA reduces HAX-1 binding; Ca2+ diminishes PLN/HAX-1 interaction dose-dependently; HAX-1 redistributes from mitochondria to ER upon co-transfection with PLN; PLN enhances HAX-1 anti-apoptotic effects against hypoxia/reoxygenation.","method":"Yeast two-hybrid, GST pulldown, surface plasmon resonance, co-transfection/colocalization, apoptosis assay","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro binding reconstitution with SPR kinetics, domain mapping, and functional apoptosis assay; multiple orthogonal methods in single rigorous study","pmids":["17241641"],"is_preprint":false},{"year":2007,"finding":"HAX-1 binds the 3'UTR hairpin motif of DNA polymerase beta mRNA exclusively as a dimer; disruption of the hairpin impairs RNA-protein complex formation; HAX-1 was detected in the nuclear matrix in addition to mitochondria, consistent with a role in post-transcriptional regulation.","method":"In vitro RNA binding assay, luciferase reporter system, mutagenesis of hairpin, subcellular fractionation","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding with mutagenesis and reporter assay; single lab, two orthogonal methods","pmids":["17704138"],"is_preprint":false},{"year":2008,"finding":"HAX-1 interacts with the mitochondrial proteases PARL and HtrA2/Omi; HAX-1 presents HtrA2 to PARL, facilitating proteolytic processing of HtrA2 to the active form in the mitochondrial intermembrane space; processed HtrA2 prevents accumulation of mitochondrial-outer-membrane-associated activated Bax, blocking apoptosis; Hax1 deficiency in mice causes apoptosis in lymphocytes and neurons.","method":"Genetic (Hax1 knockout mouse), co-immunoprecipitation, epistasis with Parl and HtrA2 mutants, Bax localization assay, apoptosis assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic loss-of-function (KO mouse), epistasis analysis with multiple pathway components, defined cellular phenotype","pmids":["18288109"],"is_preprint":false},{"year":2008,"finding":"HAX-1 also binds to SERCA2 via SERCA2 residues 575–594 interacting with the C-terminal domain of HAX-1 (aa 203–245); HAX-1 overexpression down-regulates SERCA2 protein levels and reduces ER Ca2+ levels; SERCA2 overexpression abrogates the protective effects of HAX-1 on cell survival after hypoxia/reoxygenation; PLN co-transfection causes massive redistribution of HAX-1 to ER where it co-distributes with PLN and SERCA2.","method":"Deletion mapping, co-immunoprecipitation, cell transfection/colocalization, cell viability assay, Ca2+ measurement","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain mapping by deletion analysis, Co-IP, functional assays (Ca2+ levels, cell survival); multiple orthogonal methods in single lab","pmids":["18971376"],"is_preprint":false},{"year":2008,"finding":"HAX1 mutations affecting both transcript variants 1 and 2 cause severe congenital neutropenia with neurological symptoms (epilepsy, neurodevelopmental delay), while mutations affecting only transcript variant 1 cause neutropenia without neurological symptoms; transcript variant 2 is markedly expressed in human brain tissue.","method":"Mutation screening of SCN patients, genotype-phenotype analysis, tissue expression analysis of HAX1 isoforms","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — human genetic epistasis through isoform-specific mutation analysis across multiple patients; single lab but clear genotype-phenotype correlation","pmids":["18337561"],"is_preprint":false},{"year":2008,"finding":"HIV-1 Vpr physically associates with HAX-1; Vpr overexpression dislocates HAX-1 from mitochondria and causes mitochondrial instability and cell death; HAX-1 overexpression suppresses Vpr's pro-apoptotic activity.","method":"Co-immunoprecipitation, overexpression studies, mitochondrial localization assay, cell viability assay","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus functional rescue with HAX-1 overexpression; single lab, two orthogonal methods","pmids":["16227293"],"is_preprint":false},{"year":2009,"finding":"HAX-1 overexpression reduces SERCA2a pump activity in isolated cardiomyocytes and in vivo, depressing calcium kinetics and contractility; conversely, HAX-1 downregulation enhances calcium cycling; HAX-1 promotes formation of PLN monomers (the active/inhibitory units of SERCA2a); ablation of PLN rescues HAX-1 inhibition of contractility in vivo, placing HAX-1 upstream of PLN in cardiac calcium regulation.","method":"Cardiac-specific overexpression mouse model, HAX-1 knockdown, calcium kinetics measurement, contractility assays, PLN monomer/pentamer analysis, genetic rescue (PLN ablation)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple in vivo and in vitro models (overexpression, knockdown, genetic rescue with PLN ablation), defined physiological phenotype with molecular mechanism","pmids":["19920172"],"is_preprint":false},{"year":2009,"finding":"HAX-1 variant I and II localize selectively to mitochondrial membranes, while variants III, IV, and V localize to both mitochondria and sarcoplasmic reticulum; deletion of HAX-1's NH2-terminus abolishes mitochondrial targeting and attenuates anti-apoptotic capacity; removal of the PLN-binding site prevents HAX-1 translocation to SR; HAX-1 is preferentially lost from SR of PLN-deficient hearts.","method":"Immunoelectron microscopy, subcellular fractionation, deletion analysis, cellular transfection, colocalization, PLN-deficient mouse hearts","journal":"Journal of molecular and cellular cardiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — immunoelectron microscopy plus fractionation plus deletion mutagenesis plus genetic model (PLN-KO); multiple orthogonal methods in single lab","pmids":["19913549"],"is_preprint":false},{"year":2009,"finding":"HAX-1 in vivo does not interact with PARL because the two proteins are confined in distinct cellular compartments; sequence analysis shows HAX-1 lacks authentic Bcl-2 homology (BH) modules and is unlikely to be a Bcl-2 family protein; in vitro interaction between Hax1 and PARL is proposed to be an artifact.","method":"In vivo localization/fractionation, sequence analysis and secondary structure prediction","journal":"Cell death and differentiation","confidence":"Low","confidence_rationale":"Tier 3 / Weak — localization/fractionation and computational analysis; single lab, contradicts prior Nature paper (PMID 18288109); confidence lowered due to conflicting evidence and methodological limitations","pmids":["19680265"],"is_preprint":false},{"year":2010,"finding":"Granzyme B inserts into mitochondria and cleaves HAX-1 into two fragments: an N-terminal fragment that remains in mitochondria and a C-terminal fragment released to cytosol; the N-terminal fragment acts as a dominant negative, causing mitochondrial depolarization in a cyclophilin D-dependent manner; overexpression of wild-type HAX-1 or an uncleavable mutant protects against GrB-mediated depolarization.","method":"In vitro cleavage assay, mitochondrial fractionation, overexpression of cleavage mutants, membrane potential measurement, cyclophilin D dependence assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstituted cleavage, mutagenesis (uncleavable mutant), subcellular fractionation, mechanistic dissection with cyclophilin D; multiple orthogonal methods in single lab","pmids":["20388708"],"is_preprint":false},{"year":2010,"finding":"HAX-1 interacts with XIAP via HAX-1 C-terminal domain binding to XIAP BIR2 and BIR3 domains (each with affinity similar to full-length XIAP by SPR); HAX-1 suppresses polyubiquitination of XIAP, enhancing its stability and thereby inhibiting apoptosis.","method":"Proteomic screen (immunoprecipitation + 2D gel), GST pulldown, surface plasmon resonance, ubiquitination assay, cell viability assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — SPR kinetics plus GST pulldown plus ubiquitination assay; single lab, multiple orthogonal methods","pmids":["20171186"],"is_preprint":false},{"year":2011,"finding":"Hax1 depletion in neutrophil-like PLB-985 cells impairs uropod detachment and directed migration; Hax1-deficient cells show increased integrin-mediated adhesion and reduced RhoA activity; RhoA depletion phenocopies Hax1 loss; activation of RhoA rescues adhesion defects in Hax1-deficient cells, placing Hax1 upstream of RhoA in regulating neutrophil adhesion and chemotaxis.","method":"siRNA knockdown, microfluidic migration assay, integrin-mediated adhesion assay, RhoA activity assay, epistasis (RhoA activation rescue)","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — RNAi loss-of-function with defined phenotypic readouts plus genetic epistasis (RhoA rescue); multiple orthogonal methods with clear pathway placement","pmids":["21518791"],"is_preprint":false},{"year":2012,"finding":"HAX-1 is a nucleocytoplasmic shuttling protein dependent on exportin 1 (CRM1/XPO1); two nuclear export signals (NES) were identified by systematic mutagenesis; nuclear accumulation occurs after leptomycin B treatment or specific cellular stress; HAX-1 status influences mRNA levels of DNA polymerase beta (one of its mRNA targets); HAX-1 tethering to reporter transcript decreases its expression; HAX-1 colocalizes with P-body markers.","method":"Mutagenesis of NES, leptomycin B treatment, nuclear/cytoplasmic fractionation, reporter assay, P-body colocalization","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutagenesis identifying NES, pharmacological validation, reporter assay; single lab, multiple orthogonal methods","pmids":["23164465"],"is_preprint":false},{"year":2012,"finding":"HAX1 interacts with influenza A virus PA polymerase subunit via the nuclear localization signal (NLS) domain of PA; HAX1 knockdown increases nuclear accumulation of PA and enhances viral polymerase activity and virus yield, which can be reversed by HAX1 re-expression; thus HAX1 impedes nuclear transport of PA and restricts influenza A virus propagation.","method":"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, HAX1 knockdown and rescue, nuclear fractionation, minigenome assay, virus yield assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP plus KD/rescue experiment plus defined molecular phenotype (nuclear transport of PA) plus functional viral replication readout; multiple orthogonal methods","pmids":["23055567"],"is_preprint":false},{"year":2012,"finding":"HCLS1 (HS1) is phosphorylated upon G-CSF stimulation and binds LEF-1, transporting it to the nucleus; HAX1 mutations in SCN patients impair G-CSF-triggered HCLS1 phosphorylation and reduce LEF-1 autoregulation, establishing HAX1 as required for HCLS1 phosphorylation in G-CSF signaling and granulopoiesis.","method":"Phosphorylation assays, co-immunoprecipitation, nuclear fractionation, patient myeloid cells, HCLS1-deficient mouse (neutropenic phenotype)","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — human patient cells plus mouse KO model plus Co-IP and phosphorylation assays; replicated across multiple experimental systems","pmids":["23001182"],"is_preprint":false},{"year":2012,"finding":"HAX-1 is rapidly degraded by the proteasome via K48-linked ubiquitination dependent on its PEST sequence; a PEST-deletion mutant of HAX-1 is more resistant to proteasomal degradation and exerts greater anti-apoptotic protection than wild-type HAX-1.","method":"PEST sequence deletion mutagenesis, ubiquitination assay, proteasome inhibitor treatment, apoptosis assay","journal":"BMC cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis plus ubiquitination assay plus functional apoptosis readout; single lab, multiple orthogonal methods","pmids":["22827267"],"is_preprint":false},{"year":2012,"finding":"HAX-1 overexpression inhibits the IRE-1 ER stress signaling pathway by binding to the N-terminal fragment of Hsp90; HAX-1 sequesters Hsp90 away from IRE-1 to the PLN-SERCA2a complex; loss of HAX-1 in heterozygous-deficient hearts increases infarct size and IRE-1 activity; the Hsp90 inhibitor 17-AAG abolishes HAX-1's IRE-1 inhibitory effects.","method":"Cardiac overexpression mouse model, HAX-1 heterozygous-deficient mouse, co-immunoprecipitation (HAX-1/Hsp90), pharmacological (17-AAG), ischemia/reperfusion model","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic models (overexpression, heterozygous KO) plus Co-IP plus pharmacological validation; defined molecular mechanism with in vivo phenotype","pmids":["22982986"],"is_preprint":false},{"year":2013,"finding":"HAX-1 variant 1 (v1) is anti-apoptotic while rat v2/human v4 is pro-apoptotic; Hax-1 isoforms form homotypic and heterotypic dimers with binding affinities ranging from ~3.8 nM (v1 homodimers) to ~97 nM (v1/v2 heterodimers); the minimal dimerization region spans aa 97-278; co-expression of v1 and v2 neutralizes both pro- and anti-apoptotic activities through modulation of cytochrome c release.","method":"SPR binding kinetics, deletion analysis, overexpression in epithelial cells, cytochrome c release assay, myocardial infarction model","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — SPR kinetics plus mutagenesis domain mapping plus functional assays (cytochrome c release, cell death); multiple orthogonal methods in single rigorous study","pmids":["24347163"],"is_preprint":false},{"year":2014,"finding":"PRKCD (PKCδ) phosphorylates both FBXO25 and HAX-1, directing nuclear FBXO25 to mitochondrial HAX-1; FBXO25 is the substrate-recognition subunit of SCF(FBXO25) ubiquitin ligase that ubiquitinates and degrades HAX-1 after apoptotic stress; stabilizing HAX-1 phosphodegron mutations found in human MCL inhibit apoptosis; FBXO25 re-expression in FBXO25-deleted MCL cells promotes cell death.","method":"Unbiased substrate screen, co-immunoprecipitation, ubiquitination assay, phosphorylation assay, FBXO25 re-expression in MCL cells, Eµ-Myc mouse lymphoma model, xenotransplant model","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical reconstitution of ubiquitination pathway, phosphorylation by PRKCD, multiple in vivo models, human patient mutation validation; rigorous multi-method study","pmids":["25419709"],"is_preprint":false},{"year":2014,"finding":"Hax-1 is required for Rac1-cortactin interaction and colocalization in ovarian cancer cells; Hax-1 interacts with cortactin via domains aa 1-56 (Hax-D1) and aa 113-168 (Hax-D3), and with Rac1 via domains aa 57-112 (Hax-D2) and aa 169-224 (Hax-D4); silencing of Hax-1 reduces LPA-stimulated migration of SKOV3 cells and impairs Rac1-cortactin colocalization; expression of individual Hax-1 domains competitively inhibits migration.","method":"siRNA knockdown, domain mapping by deletion/truncation, co-immunoprecipitation, colocalization, cell migration assay","journal":"Genes & cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mapping plus siRNA KD with defined migration phenotype plus Co-IP; single lab, multiple methods","pmids":["25053987"],"is_preprint":false},{"year":2015,"finding":"HAX-1 regulates cyclophilin-D (CypD) protein levels via an Hsp90-dependent mechanism: HAX-1 overexpression interferes with CypD binding to Hsp90, rendering CypD susceptible to ubiquitin-proteasomal degradation; HAX-1 overexpression enhances CypD ubiquitination; reduced CypD decreases mPTP activation; proteasome inhibition or elevated Hsp90 rescues CypD levels in HAX-1-overexpressing cells.","method":"Cardiac-specific HAX-1 overexpression and heterozygous KO mouse models, co-immunoprecipitation, ubiquitination assay, proteasome inhibitor, genetic ablation of CypD, mPTP opening assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic models plus biochemical (Co-IP, ubiquitination, proteasome inhibition) and genetic rescue (CypD ablation); comprehensive mechanism in single study","pmids":["26553996"],"is_preprint":false},{"year":2015,"finding":"Hax-1 interacts with microtubule end-binding protein EB2 in an EB2-specific manner; knockdown of either HAX1 or EB2 in skin epidermal cells stabilizes focal adhesions and impairs epidermal migration in vitro and in vivo; cell motility and focal adhesion turnover require the Hax1-EB2 interaction.","method":"Quantitative proteomics (EB2 interactome), co-immunoprecipitation, siRNA knockdown, focal adhesion assay, in vitro and in vivo migration assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative proteomics plus Co-IP plus loss-of-function with defined phenotype; single lab, multiple methods","pmids":["26527684"],"is_preprint":false},{"year":2016,"finding":"Kv3.3 (KCNC3) recruits Arp2/3 to the plasma membrane via binding of its cytoplasmic C-terminus to Hax-1, forming a stable cortical actin network that prevents rapid N-type channel inactivation; a human disease-causing Kv3.3 mutation within the conserved proline-rich domain binds Hax-1 but fails to recruit Arp2/3, resulting in growth cones with deficient actin veils in stem cell-derived neurons.","method":"Co-immunoprecipitation, cytochalasin D resistance assay, electrophysiology, stem cell-derived neurons, disease mutation analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP plus electrophysiological characterization plus disease-mutant mechanistic dissection plus neuronal phenotype in stem cell model; rigorous multi-method study","pmids":["26997484"],"is_preprint":false},{"year":2017,"finding":"HAX-1 ablation in the adult heart (cardiac-specific inducible KO) increases calcium affinity of SERCA2a and reduces PLN-SERCA2a binding, demonstrating that endogenous HAX-1 mediates approximately 50% of PLN's inhibitory activity on cardiac calcium cycling and contractility; PLN overexpression in HAX-1-null cardiomyocytes has no inhibitory effect, indicating HAX-1 limits PLN activity.","method":"Cardiac-specific inducible HAX-1 knockout mouse, calcium kinetics, SERCA2a Ca2+ affinity measurement, PLN-SERCA2a co-immunoprecipitation, isoproterenol stimulation, PLN overexpression rescue","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — cardiac-specific inducible KO mouse plus biochemical measurements plus genetic rescue; clean mechanistic quantification in vivo and in vitro","pmids":["29150445"],"is_preprint":false},{"year":2017,"finding":"HAX-1 ablation in the adult heart causes increased reactive oxygen species production at the SR/ER compartment, leading to SERCA2a oxidation and enhanced proteolysis; HAX-1 interacts with NADPH oxidase 4 (NOX4), a newly identified binding partner; NOX4 inhibition abrogates the detrimental effects of HAX-1 ablation in ischemia/reperfusion injury.","method":"Cardiac-specific inducible HAX-1 KO mouse, ROS measurement, SERCA2a oxidation assay, co-immunoprecipitation (HAX-1/NOX4), NOX inhibitor (apocynin)","journal":"Journal of molecular and cellular cardiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO model plus biochemical oxidation assay plus novel binding partner Co-IP plus pharmacological validation; multiple orthogonal methods","pmids":["29169992"],"is_preprint":false},{"year":2018,"finding":"H5N1 PB1-F2 binds to HAX-1 (a host restriction factor of IAV PA); the PA subunit of mammal-adapted H1N1 is resistant to HAX-1 restriction while avian-origin H5N1 PA remains sensitive; PB1-F2 alleviates HAX-1's inhibition of H5N1 polymerase activity through direct competition with HAX-1 for PA binding.","method":"Co-immunoprecipitation, polymerase activity assay, siRNA/overexpression of HAX-1, virus replication assay with PB1-F2-deficient mutant","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional competition assay plus virus replication with genetic mutant; single lab, multiple methods","pmids":["29563290"],"is_preprint":false},{"year":2019,"finding":"HAX1 knockdown affects actomyosin contractility through changes in RhoA and septin signaling, impairing collective (but not single-cell) migration, cell-cell junctions, and cell layer integrity in breast cancer cells.","method":"HAX1 siRNA knockdown, collective/single-cell migration assays, RhoA activity assay, septin staining, cell-cell junction analysis","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi KD with multiple phenotypic readouts and signaling pathway characterization; single lab","pmids":["31644363"],"is_preprint":false},{"year":2020,"finding":"Hepatic HAX-1 interacts with inositol 1,4,5-trisphosphate receptor-1 (InsP3R1); HAX-1 absence reduces InsP3R1 levels, improving ER-mitochondria calcium homeostasis to prevent excess mitochondrial calcium overload; HAX-1 ablation activates pyruvate dehydrogenase and increases mitochondrial utilization of glucose and fatty acids; HAX-1 deficiency also increases bile salt exporter protein (BSEP) levels, promoting enterohepatic bile acid recirculation.","method":"Liver-specific HAX-1 KO mouse, co-immunoprecipitation, InsP3R1 quantification, calcium assays, metabolic phenotyping, pyruvate dehydrogenase activity","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — liver-specific KO mouse plus Co-IP plus multiple biochemical and metabolic readouts; single lab but multiple orthogonal methods with in vivo validation","pmids":["32079675"],"is_preprint":false},{"year":2021,"finding":"Kv3.3 channels bind and stimulate TBK1 (TANK-binding kinase 1); TBK1 activity is required for Kv3.3 binding to its auxiliary subunit Hax-1 (which prevents channel inactivation); a disease-causing Kv3.3 mutation overactivates TBK1, leading to Hax-1 accumulation in multivesicular bodies and lysosomes, loss of Hax-1, caspase activation, and neuronal cell death.","method":"Co-immunoprecipitation, TBK1 kinase assay, dominant negative/inhibitor studies, subcellular trafficking assays, electrophysiology, caspase activity assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP plus kinase assay plus trafficking assay plus electrophysiology plus disease-mutant mechanistic dissection; multiple orthogonal methods","pmids":["33741962"],"is_preprint":false},{"year":2022,"finding":"HAX1 and CLPB control the balance of mitochondrial protein synthesis and persistence (mitochondrial proteostasis) as shown by SILAC proteomics; impaired mitochondrial protein dynamics in HAX1-deficient cells are associated with decreased abundance of PRKD2 and phosphorylated HSP27 (Ser78/82); cellular defects in HAX1-/- cells can be functionally reconstituted by HSP27, defining a CLPB/HAX1/(PRKD2)/HSP27 axis critical for neutrophil granulocyte differentiation.","method":"SILAC proteomics, HAX1-deficient cells/mouse models, PRKD2 and HSP27 quantification, functional reconstitution with HSP27","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — SILAC proteomics plus genetic loss-of-function plus functional reconstitution; multiple orthogonal methods identifying novel mechanistic axis","pmids":["35499078"],"is_preprint":false},{"year":2024,"finding":"EIF3H functions as a deubiquitinase for HAX1, stabilizing HAX1 by antagonizing βTrCP-mediated ubiquitination; stabilized HAX1 enhances the interaction among RAF1, MEK1, and ERK1, potentiating ERK1/2 phosphorylation and promoting colorectal cancer progression.","method":"Co-immunoprecipitation, ubiquitination assay, deubiquitination assay, conditional Eif3h deletion mouse model, RAF1-MEK1-ERK1 interaction assay, patient-derived xenografts","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — deubiquitinase activity assay plus Co-IP plus in vivo genetic model plus patient-derived xenografts; multiple orthogonal methods with in vivo validation","pmids":["38514606"],"is_preprint":false}],"current_model":"HAX1 is a multifunctional anti-apoptotic adaptor protein localized predominantly to mitochondria (and ER/SR) that suppresses apoptosis by inhibiting caspase-9, interacting with PLN/SERCA2a to regulate cardiac calcium cycling, presenting HtrA2 to PARL for processing, protecting against Omi/HtrA2-mediated and granzyme B-mediated cleavage, modulating cyclophilin-D stability via Hsp90, and regulating cell migration through RhoA, Rac1, cortactin, and EB2; its protein levels are controlled by PEST sequence-dependent proteasomal degradation, PRKCD-FBXO25-mediated ubiquitination, and EIF3H-mediated deubiquitination; HAX1 also binds specific mRNA 3'UTRs and shuttles nucleocytoplasmically via exportin-1, and loss-of-function mutations cause severe congenital neutropenia through impaired HCLS1 phosphorylation and downstream LEF-1/granulopoiesis signaling, with neurological symptoms linked to isoform-specific expression in the brain."},"narrative":{"mechanistic_narrative":"HAX1 is a multifunctional, predominantly mitochondrial adaptor protein that suppresses apoptosis and coordinates cytoskeletal dynamics, calcium handling, and protein homeostasis through a large set of compartment-specific protein and RNA interactions [PMID:9058808, PMID:18288109]. It was first identified through direct association with the Src-kinase substrate HS1/HCLS1 and localizes to mitochondria, ER, and the nuclear envelope [PMID:9058808]. Its anti-apoptotic activity operates at multiple nodes: HAX1 inhibits caspase-9 processing [PMID:16857965], presents HtrA2/Omi to the mitochondrial protease PARL to generate the active form that restrains Bax-dependent death [PMID:18288109], stabilizes XIAP by suppressing its polyubiquitination [PMID:20171186], and limits mitochondrial permeability transition by destabilizing cyclophilin-D through an Hsp90-dependent mechanism [PMID:26553996]. HAX1 maintains inner mitochondrial membrane potential, and homozygous loss-of-function mutations cause severe congenital neutropenia, with isoform-specific (transcript variant 2) expression in brain accounting for the neurological manifestations of certain mutations [PMID:17187068, PMID:18337561]; mechanistically, HAX1 is required for G-CSF–triggered HCLS1 phosphorylation and downstream LEF-1 signaling in granulopoiesis, and acts within a CLPB/HAX1/HSP27 axis governing mitochondrial proteostasis and neutrophil differentiation [PMID:23001182, PMID:35499078]. In the heart, HAX1 binds phospholamban and SERCA2a to inhibit cardiac calcium cycling and contractility, mediating roughly half of phospholamban's inhibitory activity, and protects against ischemia/reperfusion injury via Hsp90/IRE-1 and NOX4-linked redox mechanisms [PMID:17241641, PMID:19920172, PMID:29150445, PMID:29169992]. HAX1 also drives cell migration by coupling Gα13, RhoA, Rac1, cortactin, and the microtubule end-binding protein EB2 to regulate the actin cytoskeleton and focal adhesion turnover [PMID:15339924, PMID:21518791, PMID:26527684], and as a Kv3.3 auxiliary subunit it recruits Arp2/3 to build cortical actin that controls channel inactivation in neurons [PMID:26997484]. As an RNA-binding protein it binds specific 3'UTRs (vimentin, DNA polymerase beta) and shuttles between nucleus and cytoplasm via exportin-1 to influence target mRNA levels [PMID:12466525, PMID:17704138, PMID:23164465]. HAX1 abundance is tightly controlled by PEST-dependent proteasomal turnover, PRKCD-directed SCF(FBXO25) ubiquitination, and EIF3H-mediated deubiquitination, the latter promoting RAF1/MEK/ERK signaling in colorectal cancer [PMID:22827267, PMID:25419709, PMID:38514606].","teleology":[{"year":1997,"claim":"Established HAX1's existence and primary biochemical character by showing it is a mitochondrial/ER protein that directly binds the kinase substrate HS1, defining it as an intracellular adaptor.","evidence":"Yeast two-hybrid, reciprocal Co-IP, deletion mapping, and confocal microscopy","pmids":["9058808"],"confidence":"High","gaps":["Functional consequence of HS1 binding undefined","No enzymatic activity identified for HAX1 itself"]},{"year":2002,"claim":"Identified HAX1 as a sequence-specific RNA-binding protein, opening a post-transcriptional regulatory role beyond protein scaffolding.","evidence":"Yeast three-hybrid, in vitro RNA binding, and RNA affinity pulldown for vimentin 3'UTR","pmids":["12466525"],"confidence":"Medium","gaps":["Functional effect on vimentin mRNA fate not shown","In vivo relevance of the eEF-1gamma complex unestablished"]},{"year":2004,"claim":"Connected HAX1 to apoptotic signaling at two levels — as a protease substrate and as a migration regulator — linking it to mitochondrial death pathways and Rho-family GTPases.","evidence":"In vitro/in vivo Omi/HtrA2 cleavage assays (mnd2 mutant) and Gα13 Co-IP with siRNA migration and RhoA/Rac activity assays","pmids":["15371414","15339924"],"confidence":"High","gaps":["Whether HAX1 cleavage is cause or consequence of death not fully resolved","Mechanism by which HAX1 reciprocally tunes RhoA vs Rac unclear"]},{"year":2006,"claim":"Defined HAX1's core anti-apoptotic mechanism and its disease relevance by showing caspase-9 inhibition and that loss-of-function mutations cause severe congenital neutropenia via mitochondrial dysfunction.","evidence":"Cell-free caspase activation assay and positional cloning with mitochondrial membrane potential/apoptosis assays in patient myeloid cells","pmids":["16857965","17187068"],"confidence":"High","gaps":["How a single adaptor protects mitochondrial potential in myeloid cells specifically","Structural basis of caspase-9 inhibition unknown"]},{"year":2008,"claim":"Placed HAX1 within a defined mitochondrial protease module and linked it to cardiac calcium handling, while isoform analysis explained the neurological phenotype of SCN.","evidence":"Hax1 KO mouse with PARL/HtrA2 epistasis; PLN and SERCA2 domain mapping/Co-IP; SCN isoform genotype-phenotype analysis","pmids":["18288109","17241641","18971376","18337561"],"confidence":"High","gaps":["Compartmental feasibility of the PARL interaction later disputed","Quantitative contribution of HAX1 to SERCA2 regulation not yet measured"]},{"year":2009,"claim":"Tested and challenged the PARL model while quantifying HAX1's role in cardiac contractility, refining where HAX1 acts within the calcium-handling apparatus.","evidence":"In vivo localization/sequence analysis arguing against PARL interaction; cardiac overexpression/knockdown with PLN ablation rescue; isoform-specific subcellular targeting by immuno-EM","pmids":["19680265","19920172","19913549"],"confidence":"High","gaps":["Conflict over the PARL interaction (idx 17, Low) remains unreconciled","Lack of BH domains argues against simple Bcl-2-family classification"]},{"year":2010,"claim":"Showed HAX1 is targeted by cytotoxic-lymphocyte effector mechanisms and that its cleavage products actively drive mitochondrial depolarization, refining how its loss promotes death.","evidence":"In vitro granzyme B cleavage, uncleavable mutant overexpression, and cyclophilin-D-dependent membrane potential assays; XIAP SPR/ubiquitination assays","pmids":["20388708","20171186"],"confidence":"High","gaps":["Physiological contexts of granzyme-B cleavage of HAX1 in vivo","Whether XIAP stabilization operates in the same cells as caspase-9 inhibition"]},{"year":2012,"claim":"Defined HAX1's nucleocytoplasmic shuttling and post-transcriptional functions, its degradation control, and the molecular basis of its requirement in granulopoiesis.","evidence":"NES mutagenesis/leptomycin B and P-body colocalization; PEST-deletion ubiquitination assays; HCLS1 phosphorylation/LEF-1 nuclear transport in patient cells and HCLS1-KO mouse","pmids":["23164465","22827267","23001182","23055567"],"confidence":"High","gaps":["Signals coupling stress to HAX1 nuclear export not defined","How HAX1 enables HCLS1 phosphorylation mechanistically unresolved"]},{"year":2014,"claim":"Established kinase-directed, ubiquitin-mediated control of HAX1 abundance and its dimerization-dependent, isoform-specific apoptotic output, with direct relevance to lymphoma.","evidence":"PRKCD/SCF(FBXO25) ubiquitination and phosphodegron analysis in MCL models; SPR dimer kinetics with cytochrome c release and infarction assays; Rac1/cortactin domain mapping","pmids":["25419709","24347163","25053987"],"confidence":"High","gaps":["How pro- and anti-apoptotic isoforms are balanced in normal tissues","Whether FBXO25 degradation of HAX1 operates outside apoptotic stress"]},{"year":2015,"claim":"Defined an Hsp90-centered chaperone-trafficking logic by which HAX1 simultaneously suppresses IRE-1 ER stress signaling and destabilizes cyclophilin-D to limit mitochondrial permeability transition.","evidence":"Cardiac overexpression and heterozygous-KO mice, HAX1/Hsp90 Co-IP, 17-AAG pharmacology, CypD ablation and mPTP/ubiquitination assays","pmids":["22982986","26553996"],"confidence":"High","gaps":["Stoichiometry of HAX1's Hsp90 sequestration across compartments","How HAX1 partitions Hsp90 between IRE-1, PLN-SERCA2a, and CypD"]},{"year":2016,"claim":"Defined HAX1 as a Kv3.3 auxiliary subunit that nucleates an Arp2/3-based cortical actin network controlling channel inactivation, linking its cytoskeletal role to neuronal disease mutations.","evidence":"Co-IP, cytochalasin-D resistance, electrophysiology, and disease-mutant analysis in stem-cell-derived neurons; EB2 interactome with focal adhesion/migration assays","pmids":["26997484","26527684"],"confidence":"High","gaps":["How HAX1 spatially couples Kv3.3, Arp2/3, and EB2 simultaneously","Whether neuronal actin role connects to SCN neurological phenotype"]},{"year":2017,"claim":"Quantified endogenous HAX1's contribution to cardiac calcium regulation and uncovered a redox dimension whereby HAX1 protects SERCA2a from oxidative proteolysis via NOX4.","evidence":"Cardiac-specific inducible KO with SERCA2a Ca2+-affinity and PLN-SERCA2a Co-IP; ROS/oxidation assays and HAX1/NOX4 Co-IP with NOX inhibition","pmids":["29150445","29169992"],"confidence":"High","gaps":["Direct molecular mechanism of HAX1-NOX4 functional coupling","Whether redox role generalizes beyond cardiac SR"]},{"year":2020,"claim":"Extended HAX1's calcium-handling and metabolic roles to liver, identifying InsP3R1 as a partner controlling ER-mitochondria calcium transfer, mitochondrial substrate utilization, and bile acid recirculation.","evidence":"Liver-specific HAX1 KO mouse with Co-IP, calcium assays, metabolic phenotyping, and PDH activity","pmids":["32079675"],"confidence":"High","gaps":["Whether the InsP3R1 axis operates in non-hepatic tissues","Mechanism linking HAX1 loss to BSEP elevation in vivo"]},{"year":2022,"claim":"Defined a CLPB/HAX1/HSP27 mitochondrial proteostasis axis that explains HAX1's requirement in neutrophil differentiation beyond its classical anti-apoptotic activity.","evidence":"SILAC proteomics in HAX1-deficient cells/mice with PRKD2/HSP27 quantification and functional HSP27 reconstitution","pmids":["35499078"],"confidence":"High","gaps":["How HAX1 mechanistically controls mitochondrial protein turnover","Direct biochemical link between HAX1 and CLPB unresolved"]},{"year":2024,"claim":"Established deubiquitinase-mediated stabilization of HAX1 as an oncogenic driver, connecting HAX1 abundance control to RAF1/MEK/ERK signaling in colorectal cancer.","evidence":"EIF3H deubiquitination/Co-IP assays, conditional Eif3h-KO mouse, RAF1-MEK1-ERK1 interaction assays, and patient-derived xenografts","pmids":["38514606"],"confidence":"High","gaps":["How HAX1 scaffolds the RAF1-MEK-ERK module mechanistically","Whether EIF3H-HAX1 axis operates in non-colorectal contexts"]},{"year":null,"claim":"How HAX1's many compartment-specific activities — mitochondrial apoptosis control, ER/SR calcium handling, cytoskeletal migration, RNA binding, and proteostasis — are integrated or selectively engaged in a given cell type remains unresolved, and no high-resolution structure of HAX1 or its complexes has been defined in this corpus.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of HAX1 or its interaction interfaces","Unclear how isoform composition dictates which functional module dominates","Compartmental disagreement over key interactions (e.g., PARL) not reconciled"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,5,11,31]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[8,9,15,19,29,32]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[3,10,21]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[25,29]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,4,11,16,18]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0,2,12,16,25]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[0]},{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[10,21]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6,31]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[8,11,18,19,29]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[25,33]},{"term_id":"R-HSA-397014","term_label":"Muscle contraction","supporting_discovery_ids":[9,15,32]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[24,27,38,39]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5,20,39]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[3,10,21]}],"complexes":["SCF(FBXO25) ubiquitin ligase substrate","Kv3.3-HAX1-Arp2/3 cortical actin complex","PLN-SERCA2a complex"],"partners":["HCLS1","PLN","ATP2A2","HTRA2","PARL","XIAP","CTTN","KCNC3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00165","full_name":"HCLS1-associated protein X-1","aliases":["HS1-associating protein X-1","HAX-1","HS1-binding protein 1","HSP1BP-1"],"length_aa":279,"mass_kda":31.6,"function":"Recruits the Arp2/3 complex to the cell cortex and regulates reorganization of the cortical actin cytoskeleton via its interaction with KCNC3 and the Arp2/3 complex (PubMed:26997484). Slows down the rate of inactivation of KCNC3 channels (PubMed:26997484). Promotes GNA13-mediated cell migration. Involved in the clathrin-mediated endocytosis pathway. May be involved in internalization of ABC transporters such as ABCB11. May inhibit CASP9 and CASP3. Promotes cell survival. May regulate intracellular calcium pools","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O00165/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HAX1","classification":"Not Classified","n_dependent_lines":176,"n_total_lines":1208,"dependency_fraction":0.1456953642384106},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HAX1","total_profiled":1310},"omim":[{"mim_id":"619835","title":"3-@METHYLGLUTACONIC ACIDURIA, TYPE VIIA; MGCA7A","url":"https://www.omim.org/entry/619835"},{"mim_id":"618592","title":"RING FINGER PROTEIN 217; RNF217","url":"https://www.omim.org/entry/618592"},{"mim_id":"616254","title":"CASEINOLYTIC PEPTIDASE B; CLPB","url":"https://www.omim.org/entry/616254"},{"mim_id":"611675","title":"KIAA0513 GENE; KIAA0513","url":"https://www.omim.org/entry/611675"},{"mim_id":"610738","title":"NEUTROPENIA, SEVERE CONGENITAL, 3, AUTOSOMAL RECESSIVE; SCN3","url":"https://www.omim.org/entry/610738"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HAX1"},"hgnc":{"alias_symbol":["HS1BP1","HCLSBP1","HAX-1"],"prev_symbol":[]},"alphafold":{"accession":"O00165","domains":[{"cath_id":"-","chopping":"209-244","consensus_level":"medium","plddt":92.0356,"start":209,"end":244}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00165","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00165-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00165-F1-predicted_aligned_error_v6.png","plddt_mean":59.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HAX1","jax_strain_url":"https://www.jax.org/strain/search?query=HAX1"},"sequence":{"accession":"O00165","fasta_url":"https://rest.uniprot.org/uniprotkb/O00165.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00165/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00165"}},"corpus_meta":[{"pmid":"17187068","id":"PMC_17187068","title":"HAX1 deficiency causes 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co-immunoprecipitation, confocal microscopy, deletion mutant analysis\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP in multiple cell lines, deletion mapping of interaction domains, confirmed by colocalization; foundational paper replicated by many subsequent studies\",\n      \"pmids\": [\"9058808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"HAX-1 interacts with the polycystic kidney disease protein PKD2 (but not the closely related PKD2L) and also associates with the F-actin-binding protein cortactin, linking PKD2 to the actin cytoskeleton; PKD2 and HAX-1 colocalize in the cell body and in cellular processes and lamellipodia.\",\n      \"method\": \"Yeast two-hybrid screen, immunofluorescence colocalization, specificity demonstrated by failure of PKD2L to interact\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid with specificity control, immunofluorescence colocalization; no full reciprocal Co-IP reported in abstract\",\n      \"pmids\": [\"10760273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"KSHV K15 protein interacts with HAX-1 via its C-terminus both in vitro and in vivo; HAX-1 colocalizes with K15 at the ER and mitochondria; HAX-1 can form homodimers in vivo and functions as a potent inhibitor of apoptosis.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro and in vivo binding assays, immunofluorescence colocalization, apoptosis assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid confirmed by in vitro/in vivo interaction assays, homodimerization demonstrated in vivo, functional apoptosis assay\",\n      \"pmids\": [\"11752170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HAX-1 binds specifically to the 3' untranslated region of vimentin mRNA; HAX-1 and eEF-1gamma form protein complexes that interact with vimentin 3'UTR and can be pulled from HeLa cell extracts using a vimentin 3'UTR RNA affinity column, establishing HAX-1 as an RNA-binding protein.\",\n      \"method\": \"Yeast three-hybrid assay, in vitro RNA-protein binding, RNA affinity pulldown from cell extracts\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast three-hybrid plus in vitro binding and RNA affinity pulldown; two orthogonal methods in single lab\",\n      \"pmids\": [\"12466525\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"HAX-1 is a specific substrate of the mitochondrial serine protease Omi/HtrA2; Omi cleaves HAX-1 both in vitro and in vivo during apoptosis; HAX-1 degradation is an early event occurring while Omi is still confined to mitochondria; inhibition of Omi protease activity prevents HAX-1 degradation and reduces cell death.\",\n      \"method\": \"In vitro cleavage assay, in vivo cleavage in cells treated with apoptotic stimuli, Omi-specific inhibitor, cell line with catalytically inactive Omi (mnd2 mice-derived)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstituted cleavage assay plus in vivo confirmation plus genetic (mnd2 catalytic mutant) and pharmacological validation; multiple orthogonal methods in one study\",\n      \"pmids\": [\"15371414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Gα13 physically interacts with HAX-1, and this interaction is required for Gα13-stimulated cell migration; HAX-1 expression reduces actin stress fibers and focal adhesion complexes in Gα13-expressing cells; HAX-1 attenuates Gα13-stimulated RhoA activity while potentiating Rac activity; a quaternary complex of Gα13, HAX-1, Rac, and cortactin was identified; siRNA-mediated silencing of HAX-1 drastically reduces Gα13-mediated cell migration.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, cell migration assay, RhoA/Rac activity assays, actin/focal adhesion staining\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP plus loss-of-function (siRNA) with defined migration phenotype plus signaling readouts (RhoA/Rac); multiple orthogonal methods\",\n      \"pmids\": [\"15339924\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"HAX-1 binds to BSEP, MDR1, and MDR2 ABC transporters; HAX-1 co-localizes with BSEP and MDR1 at the apical membrane of MDCK cells; RNAi-mediated depletion of HAX-1 increases BSEP levels in the apical membrane by 71% by enhancing retention (not by altering synthesis, modification, or delivery); HAX-1 also interacts with cortactin and participates in BSEP internalization from the apical membrane.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, RNA interference, pulse-chase labeling, subcellular fractionation, immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal validation methods (yeast 2-hybrid, GST pulldown, Co-IP, RNAi, pulse-chase) in single rigorous study\",\n      \"pmids\": [\"15159385\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"HAX-1 is critical for maintaining the inner mitochondrial membrane potential in myeloid cells; loss-of-function HAX1 mutations (homozygous) cause increased apoptosis in myeloid cells and severe congenital neutropenia.\",\n      \"method\": \"Positional cloning, germline mutation identification, mitochondrial membrane potential assay, apoptosis assay in patient myeloid cells\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional loss-of-function in human patients with defined cellular phenotype (mitochondrial membrane potential, apoptosis) replicated across multiple pedigrees\",\n      \"pmids\": [\"17187068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"HAX-1 interacts with caspase-9 and inhibits caspase-9 processing in a dose-dependent manner in a cell-free caspase activation assay; HAX-1 overexpression in adult cardiac myocytes protects against apoptosis; on apoptotic stimulation, caspase-9 translocates to mitochondria and colocalizes with HAX-1.\",\n      \"method\": \"Yeast two-hybrid, cell-free caspase activation assay with recombinant protein, overexpression/siRNA knockdown in cardiac myocytes, immunofluorescence colocalization\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstituted cell-free caspase inhibition assay with recombinant HAX-1 plus cellular overexpression/knockdown studies; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"16857965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"HAX-1 interacts with phospholamban (PLN) via PLN residues 16–22 and HAX-1 residues 203–245; binding affinity ~1 µM measured by surface plasmon resonance; phosphorylation of PLN by PKA reduces HAX-1 binding; Ca2+ diminishes PLN/HAX-1 interaction dose-dependently; HAX-1 redistributes from mitochondria to ER upon co-transfection with PLN; PLN enhances HAX-1 anti-apoptotic effects against hypoxia/reoxygenation.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, surface plasmon resonance, co-transfection/colocalization, apoptosis assay\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro binding reconstitution with SPR kinetics, domain mapping, and functional apoptosis assay; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"17241641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"HAX-1 binds the 3'UTR hairpin motif of DNA polymerase beta mRNA exclusively as a dimer; disruption of the hairpin impairs RNA-protein complex formation; HAX-1 was detected in the nuclear matrix in addition to mitochondria, consistent with a role in post-transcriptional regulation.\",\n      \"method\": \"In vitro RNA binding assay, luciferase reporter system, mutagenesis of hairpin, subcellular fractionation\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding with mutagenesis and reporter assay; single lab, two orthogonal methods\",\n      \"pmids\": [\"17704138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"HAX-1 interacts with the mitochondrial proteases PARL and HtrA2/Omi; HAX-1 presents HtrA2 to PARL, facilitating proteolytic processing of HtrA2 to the active form in the mitochondrial intermembrane space; processed HtrA2 prevents accumulation of mitochondrial-outer-membrane-associated activated Bax, blocking apoptosis; Hax1 deficiency in mice causes apoptosis in lymphocytes and neurons.\",\n      \"method\": \"Genetic (Hax1 knockout mouse), co-immunoprecipitation, epistasis with Parl and HtrA2 mutants, Bax localization assay, apoptosis assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic loss-of-function (KO mouse), epistasis analysis with multiple pathway components, defined cellular phenotype\",\n      \"pmids\": [\"18288109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"HAX-1 also binds to SERCA2 via SERCA2 residues 575–594 interacting with the C-terminal domain of HAX-1 (aa 203–245); HAX-1 overexpression down-regulates SERCA2 protein levels and reduces ER Ca2+ levels; SERCA2 overexpression abrogates the protective effects of HAX-1 on cell survival after hypoxia/reoxygenation; PLN co-transfection causes massive redistribution of HAX-1 to ER where it co-distributes with PLN and SERCA2.\",\n      \"method\": \"Deletion mapping, co-immunoprecipitation, cell transfection/colocalization, cell viability assay, Ca2+ measurement\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mapping by deletion analysis, Co-IP, functional assays (Ca2+ levels, cell survival); multiple orthogonal methods in single lab\",\n      \"pmids\": [\"18971376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"HAX1 mutations affecting both transcript variants 1 and 2 cause severe congenital neutropenia with neurological symptoms (epilepsy, neurodevelopmental delay), while mutations affecting only transcript variant 1 cause neutropenia without neurological symptoms; transcript variant 2 is markedly expressed in human brain tissue.\",\n      \"method\": \"Mutation screening of SCN patients, genotype-phenotype analysis, tissue expression analysis of HAX1 isoforms\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — human genetic epistasis through isoform-specific mutation analysis across multiple patients; single lab but clear genotype-phenotype correlation\",\n      \"pmids\": [\"18337561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"HIV-1 Vpr physically associates with HAX-1; Vpr overexpression dislocates HAX-1 from mitochondria and causes mitochondrial instability and cell death; HAX-1 overexpression suppresses Vpr's pro-apoptotic activity.\",\n      \"method\": \"Co-immunoprecipitation, overexpression studies, mitochondrial localization assay, cell viability assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus functional rescue with HAX-1 overexpression; single lab, two orthogonal methods\",\n      \"pmids\": [\"16227293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HAX-1 overexpression reduces SERCA2a pump activity in isolated cardiomyocytes and in vivo, depressing calcium kinetics and contractility; conversely, HAX-1 downregulation enhances calcium cycling; HAX-1 promotes formation of PLN monomers (the active/inhibitory units of SERCA2a); ablation of PLN rescues HAX-1 inhibition of contractility in vivo, placing HAX-1 upstream of PLN in cardiac calcium regulation.\",\n      \"method\": \"Cardiac-specific overexpression mouse model, HAX-1 knockdown, calcium kinetics measurement, contractility assays, PLN monomer/pentamer analysis, genetic rescue (PLN ablation)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple in vivo and in vitro models (overexpression, knockdown, genetic rescue with PLN ablation), defined physiological phenotype with molecular mechanism\",\n      \"pmids\": [\"19920172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HAX-1 variant I and II localize selectively to mitochondrial membranes, while variants III, IV, and V localize to both mitochondria and sarcoplasmic reticulum; deletion of HAX-1's NH2-terminus abolishes mitochondrial targeting and attenuates anti-apoptotic capacity; removal of the PLN-binding site prevents HAX-1 translocation to SR; HAX-1 is preferentially lost from SR of PLN-deficient hearts.\",\n      \"method\": \"Immunoelectron microscopy, subcellular fractionation, deletion analysis, cellular transfection, colocalization, PLN-deficient mouse hearts\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — immunoelectron microscopy plus fractionation plus deletion mutagenesis plus genetic model (PLN-KO); multiple orthogonal methods in single lab\",\n      \"pmids\": [\"19913549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HAX-1 in vivo does not interact with PARL because the two proteins are confined in distinct cellular compartments; sequence analysis shows HAX-1 lacks authentic Bcl-2 homology (BH) modules and is unlikely to be a Bcl-2 family protein; in vitro interaction between Hax1 and PARL is proposed to be an artifact.\",\n      \"method\": \"In vivo localization/fractionation, sequence analysis and secondary structure prediction\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — localization/fractionation and computational analysis; single lab, contradicts prior Nature paper (PMID 18288109); confidence lowered due to conflicting evidence and methodological limitations\",\n      \"pmids\": [\"19680265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Granzyme B inserts into mitochondria and cleaves HAX-1 into two fragments: an N-terminal fragment that remains in mitochondria and a C-terminal fragment released to cytosol; the N-terminal fragment acts as a dominant negative, causing mitochondrial depolarization in a cyclophilin D-dependent manner; overexpression of wild-type HAX-1 or an uncleavable mutant protects against GrB-mediated depolarization.\",\n      \"method\": \"In vitro cleavage assay, mitochondrial fractionation, overexpression of cleavage mutants, membrane potential measurement, cyclophilin D dependence assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstituted cleavage, mutagenesis (uncleavable mutant), subcellular fractionation, mechanistic dissection with cyclophilin D; multiple orthogonal methods in single lab\",\n      \"pmids\": [\"20388708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"HAX-1 interacts with XIAP via HAX-1 C-terminal domain binding to XIAP BIR2 and BIR3 domains (each with affinity similar to full-length XIAP by SPR); HAX-1 suppresses polyubiquitination of XIAP, enhancing its stability and thereby inhibiting apoptosis.\",\n      \"method\": \"Proteomic screen (immunoprecipitation + 2D gel), GST pulldown, surface plasmon resonance, ubiquitination assay, cell viability assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SPR kinetics plus GST pulldown plus ubiquitination assay; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"20171186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Hax1 depletion in neutrophil-like PLB-985 cells impairs uropod detachment and directed migration; Hax1-deficient cells show increased integrin-mediated adhesion and reduced RhoA activity; RhoA depletion phenocopies Hax1 loss; activation of RhoA rescues adhesion defects in Hax1-deficient cells, placing Hax1 upstream of RhoA in regulating neutrophil adhesion and chemotaxis.\",\n      \"method\": \"siRNA knockdown, microfluidic migration assay, integrin-mediated adhesion assay, RhoA activity assay, epistasis (RhoA activation rescue)\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RNAi loss-of-function with defined phenotypic readouts plus genetic epistasis (RhoA rescue); multiple orthogonal methods with clear pathway placement\",\n      \"pmids\": [\"21518791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HAX-1 is a nucleocytoplasmic shuttling protein dependent on exportin 1 (CRM1/XPO1); two nuclear export signals (NES) were identified by systematic mutagenesis; nuclear accumulation occurs after leptomycin B treatment or specific cellular stress; HAX-1 status influences mRNA levels of DNA polymerase beta (one of its mRNA targets); HAX-1 tethering to reporter transcript decreases its expression; HAX-1 colocalizes with P-body markers.\",\n      \"method\": \"Mutagenesis of NES, leptomycin B treatment, nuclear/cytoplasmic fractionation, reporter assay, P-body colocalization\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutagenesis identifying NES, pharmacological validation, reporter assay; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"23164465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HAX1 interacts with influenza A virus PA polymerase subunit via the nuclear localization signal (NLS) domain of PA; HAX1 knockdown increases nuclear accumulation of PA and enhances viral polymerase activity and virus yield, which can be reversed by HAX1 re-expression; thus HAX1 impedes nuclear transport of PA and restricts influenza A virus propagation.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, co-immunoprecipitation, HAX1 knockdown and rescue, nuclear fractionation, minigenome assay, virus yield assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP plus KD/rescue experiment plus defined molecular phenotype (nuclear transport of PA) plus functional viral replication readout; multiple orthogonal methods\",\n      \"pmids\": [\"23055567\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HCLS1 (HS1) is phosphorylated upon G-CSF stimulation and binds LEF-1, transporting it to the nucleus; HAX1 mutations in SCN patients impair G-CSF-triggered HCLS1 phosphorylation and reduce LEF-1 autoregulation, establishing HAX1 as required for HCLS1 phosphorylation in G-CSF signaling and granulopoiesis.\",\n      \"method\": \"Phosphorylation assays, co-immunoprecipitation, nuclear fractionation, patient myeloid cells, HCLS1-deficient mouse (neutropenic phenotype)\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human patient cells plus mouse KO model plus Co-IP and phosphorylation assays; replicated across multiple experimental systems\",\n      \"pmids\": [\"23001182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HAX-1 is rapidly degraded by the proteasome via K48-linked ubiquitination dependent on its PEST sequence; a PEST-deletion mutant of HAX-1 is more resistant to proteasomal degradation and exerts greater anti-apoptotic protection than wild-type HAX-1.\",\n      \"method\": \"PEST sequence deletion mutagenesis, ubiquitination assay, proteasome inhibitor treatment, apoptosis assay\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis plus ubiquitination assay plus functional apoptosis readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"22827267\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HAX-1 overexpression inhibits the IRE-1 ER stress signaling pathway by binding to the N-terminal fragment of Hsp90; HAX-1 sequesters Hsp90 away from IRE-1 to the PLN-SERCA2a complex; loss of HAX-1 in heterozygous-deficient hearts increases infarct size and IRE-1 activity; the Hsp90 inhibitor 17-AAG abolishes HAX-1's IRE-1 inhibitory effects.\",\n      \"method\": \"Cardiac overexpression mouse model, HAX-1 heterozygous-deficient mouse, co-immunoprecipitation (HAX-1/Hsp90), pharmacological (17-AAG), ischemia/reperfusion model\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic models (overexpression, heterozygous KO) plus Co-IP plus pharmacological validation; defined molecular mechanism with in vivo phenotype\",\n      \"pmids\": [\"22982986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"HAX-1 variant 1 (v1) is anti-apoptotic while rat v2/human v4 is pro-apoptotic; Hax-1 isoforms form homotypic and heterotypic dimers with binding affinities ranging from ~3.8 nM (v1 homodimers) to ~97 nM (v1/v2 heterodimers); the minimal dimerization region spans aa 97-278; co-expression of v1 and v2 neutralizes both pro- and anti-apoptotic activities through modulation of cytochrome c release.\",\n      \"method\": \"SPR binding kinetics, deletion analysis, overexpression in epithelial cells, cytochrome c release assay, myocardial infarction model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — SPR kinetics plus mutagenesis domain mapping plus functional assays (cytochrome c release, cell death); multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"24347163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PRKCD (PKCδ) phosphorylates both FBXO25 and HAX-1, directing nuclear FBXO25 to mitochondrial HAX-1; FBXO25 is the substrate-recognition subunit of SCF(FBXO25) ubiquitin ligase that ubiquitinates and degrades HAX-1 after apoptotic stress; stabilizing HAX-1 phosphodegron mutations found in human MCL inhibit apoptosis; FBXO25 re-expression in FBXO25-deleted MCL cells promotes cell death.\",\n      \"method\": \"Unbiased substrate screen, co-immunoprecipitation, ubiquitination assay, phosphorylation assay, FBXO25 re-expression in MCL cells, Eµ-Myc mouse lymphoma model, xenotransplant model\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical reconstitution of ubiquitination pathway, phosphorylation by PRKCD, multiple in vivo models, human patient mutation validation; rigorous multi-method study\",\n      \"pmids\": [\"25419709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Hax-1 is required for Rac1-cortactin interaction and colocalization in ovarian cancer cells; Hax-1 interacts with cortactin via domains aa 1-56 (Hax-D1) and aa 113-168 (Hax-D3), and with Rac1 via domains aa 57-112 (Hax-D2) and aa 169-224 (Hax-D4); silencing of Hax-1 reduces LPA-stimulated migration of SKOV3 cells and impairs Rac1-cortactin colocalization; expression of individual Hax-1 domains competitively inhibits migration.\",\n      \"method\": \"siRNA knockdown, domain mapping by deletion/truncation, co-immunoprecipitation, colocalization, cell migration assay\",\n      \"journal\": \"Genes & cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mapping plus siRNA KD with defined migration phenotype plus Co-IP; single lab, multiple methods\",\n      \"pmids\": [\"25053987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HAX-1 regulates cyclophilin-D (CypD) protein levels via an Hsp90-dependent mechanism: HAX-1 overexpression interferes with CypD binding to Hsp90, rendering CypD susceptible to ubiquitin-proteasomal degradation; HAX-1 overexpression enhances CypD ubiquitination; reduced CypD decreases mPTP activation; proteasome inhibition or elevated Hsp90 rescues CypD levels in HAX-1-overexpressing cells.\",\n      \"method\": \"Cardiac-specific HAX-1 overexpression and heterozygous KO mouse models, co-immunoprecipitation, ubiquitination assay, proteasome inhibitor, genetic ablation of CypD, mPTP opening assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic models plus biochemical (Co-IP, ubiquitination, proteasome inhibition) and genetic rescue (CypD ablation); comprehensive mechanism in single study\",\n      \"pmids\": [\"26553996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Hax-1 interacts with microtubule end-binding protein EB2 in an EB2-specific manner; knockdown of either HAX1 or EB2 in skin epidermal cells stabilizes focal adhesions and impairs epidermal migration in vitro and in vivo; cell motility and focal adhesion turnover require the Hax1-EB2 interaction.\",\n      \"method\": \"Quantitative proteomics (EB2 interactome), co-immunoprecipitation, siRNA knockdown, focal adhesion assay, in vitro and in vivo migration assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative proteomics plus Co-IP plus loss-of-function with defined phenotype; single lab, multiple methods\",\n      \"pmids\": [\"26527684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Kv3.3 (KCNC3) recruits Arp2/3 to the plasma membrane via binding of its cytoplasmic C-terminus to Hax-1, forming a stable cortical actin network that prevents rapid N-type channel inactivation; a human disease-causing Kv3.3 mutation within the conserved proline-rich domain binds Hax-1 but fails to recruit Arp2/3, resulting in growth cones with deficient actin veils in stem cell-derived neurons.\",\n      \"method\": \"Co-immunoprecipitation, cytochalasin D resistance assay, electrophysiology, stem cell-derived neurons, disease mutation analysis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP plus electrophysiological characterization plus disease-mutant mechanistic dissection plus neuronal phenotype in stem cell model; rigorous multi-method study\",\n      \"pmids\": [\"26997484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HAX-1 ablation in the adult heart (cardiac-specific inducible KO) increases calcium affinity of SERCA2a and reduces PLN-SERCA2a binding, demonstrating that endogenous HAX-1 mediates approximately 50% of PLN's inhibitory activity on cardiac calcium cycling and contractility; PLN overexpression in HAX-1-null cardiomyocytes has no inhibitory effect, indicating HAX-1 limits PLN activity.\",\n      \"method\": \"Cardiac-specific inducible HAX-1 knockout mouse, calcium kinetics, SERCA2a Ca2+ affinity measurement, PLN-SERCA2a co-immunoprecipitation, isoproterenol stimulation, PLN overexpression rescue\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cardiac-specific inducible KO mouse plus biochemical measurements plus genetic rescue; clean mechanistic quantification in vivo and in vitro\",\n      \"pmids\": [\"29150445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HAX-1 ablation in the adult heart causes increased reactive oxygen species production at the SR/ER compartment, leading to SERCA2a oxidation and enhanced proteolysis; HAX-1 interacts with NADPH oxidase 4 (NOX4), a newly identified binding partner; NOX4 inhibition abrogates the detrimental effects of HAX-1 ablation in ischemia/reperfusion injury.\",\n      \"method\": \"Cardiac-specific inducible HAX-1 KO mouse, ROS measurement, SERCA2a oxidation assay, co-immunoprecipitation (HAX-1/NOX4), NOX inhibitor (apocynin)\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO model plus biochemical oxidation assay plus novel binding partner Co-IP plus pharmacological validation; multiple orthogonal methods\",\n      \"pmids\": [\"29169992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"H5N1 PB1-F2 binds to HAX-1 (a host restriction factor of IAV PA); the PA subunit of mammal-adapted H1N1 is resistant to HAX-1 restriction while avian-origin H5N1 PA remains sensitive; PB1-F2 alleviates HAX-1's inhibition of H5N1 polymerase activity through direct competition with HAX-1 for PA binding.\",\n      \"method\": \"Co-immunoprecipitation, polymerase activity assay, siRNA/overexpression of HAX-1, virus replication assay with PB1-F2-deficient mutant\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional competition assay plus virus replication with genetic mutant; single lab, multiple methods\",\n      \"pmids\": [\"29563290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HAX1 knockdown affects actomyosin contractility through changes in RhoA and septin signaling, impairing collective (but not single-cell) migration, cell-cell junctions, and cell layer integrity in breast cancer cells.\",\n      \"method\": \"HAX1 siRNA knockdown, collective/single-cell migration assays, RhoA activity assay, septin staining, cell-cell junction analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi KD with multiple phenotypic readouts and signaling pathway characterization; single lab\",\n      \"pmids\": [\"31644363\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Hepatic HAX-1 interacts with inositol 1,4,5-trisphosphate receptor-1 (InsP3R1); HAX-1 absence reduces InsP3R1 levels, improving ER-mitochondria calcium homeostasis to prevent excess mitochondrial calcium overload; HAX-1 ablation activates pyruvate dehydrogenase and increases mitochondrial utilization of glucose and fatty acids; HAX-1 deficiency also increases bile salt exporter protein (BSEP) levels, promoting enterohepatic bile acid recirculation.\",\n      \"method\": \"Liver-specific HAX-1 KO mouse, co-immunoprecipitation, InsP3R1 quantification, calcium assays, metabolic phenotyping, pyruvate dehydrogenase activity\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — liver-specific KO mouse plus Co-IP plus multiple biochemical and metabolic readouts; single lab but multiple orthogonal methods with in vivo validation\",\n      \"pmids\": [\"32079675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Kv3.3 channels bind and stimulate TBK1 (TANK-binding kinase 1); TBK1 activity is required for Kv3.3 binding to its auxiliary subunit Hax-1 (which prevents channel inactivation); a disease-causing Kv3.3 mutation overactivates TBK1, leading to Hax-1 accumulation in multivesicular bodies and lysosomes, loss of Hax-1, caspase activation, and neuronal cell death.\",\n      \"method\": \"Co-immunoprecipitation, TBK1 kinase assay, dominant negative/inhibitor studies, subcellular trafficking assays, electrophysiology, caspase activity assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP plus kinase assay plus trafficking assay plus electrophysiology plus disease-mutant mechanistic dissection; multiple orthogonal methods\",\n      \"pmids\": [\"33741962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HAX1 and CLPB control the balance of mitochondrial protein synthesis and persistence (mitochondrial proteostasis) as shown by SILAC proteomics; impaired mitochondrial protein dynamics in HAX1-deficient cells are associated with decreased abundance of PRKD2 and phosphorylated HSP27 (Ser78/82); cellular defects in HAX1-/- cells can be functionally reconstituted by HSP27, defining a CLPB/HAX1/(PRKD2)/HSP27 axis critical for neutrophil granulocyte differentiation.\",\n      \"method\": \"SILAC proteomics, HAX1-deficient cells/mouse models, PRKD2 and HSP27 quantification, functional reconstitution with HSP27\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — SILAC proteomics plus genetic loss-of-function plus functional reconstitution; multiple orthogonal methods identifying novel mechanistic axis\",\n      \"pmids\": [\"35499078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"EIF3H functions as a deubiquitinase for HAX1, stabilizing HAX1 by antagonizing βTrCP-mediated ubiquitination; stabilized HAX1 enhances the interaction among RAF1, MEK1, and ERK1, potentiating ERK1/2 phosphorylation and promoting colorectal cancer progression.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, deubiquitination assay, conditional Eif3h deletion mouse model, RAF1-MEK1-ERK1 interaction assay, patient-derived xenografts\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — deubiquitinase activity assay plus Co-IP plus in vivo genetic model plus patient-derived xenografts; multiple orthogonal methods with in vivo validation\",\n      \"pmids\": [\"38514606\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HAX1 is a multifunctional anti-apoptotic adaptor protein localized predominantly to mitochondria (and ER/SR) that suppresses apoptosis by inhibiting caspase-9, interacting with PLN/SERCA2a to regulate cardiac calcium cycling, presenting HtrA2 to PARL for processing, protecting against Omi/HtrA2-mediated and granzyme B-mediated cleavage, modulating cyclophilin-D stability via Hsp90, and regulating cell migration through RhoA, Rac1, cortactin, and EB2; its protein levels are controlled by PEST sequence-dependent proteasomal degradation, PRKCD-FBXO25-mediated ubiquitination, and EIF3H-mediated deubiquitination; HAX1 also binds specific mRNA 3'UTRs and shuttles nucleocytoplasmically via exportin-1, and loss-of-function mutations cause severe congenital neutropenia through impaired HCLS1 phosphorylation and downstream LEF-1/granulopoiesis signaling, with neurological symptoms linked to isoform-specific expression in the brain.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HAX1 is a multifunctional, predominantly mitochondrial adaptor protein that suppresses apoptosis and coordinates cytoskeletal dynamics, calcium handling, and protein homeostasis through a large set of compartment-specific protein and RNA interactions [#0, #11]. It was first identified through direct association with the Src-kinase substrate HS1/HCLS1 and localizes to mitochondria, ER, and the nuclear envelope [#0]. Its anti-apoptotic activity operates at multiple nodes: HAX1 inhibits caspase-9 processing [#8], presents HtrA2/Omi to the mitochondrial protease PARL to generate the active form that restrains Bax-dependent death [#11], stabilizes XIAP by suppressing its polyubiquitination [#19], and limits mitochondrial permeability transition by destabilizing cyclophilin-D through an Hsp90-dependent mechanism [#29]. HAX1 maintains inner mitochondrial membrane potential, and homozygous loss-of-function mutations cause severe congenital neutropenia, with isoform-specific (transcript variant 2) expression in brain accounting for the neurological manifestations of certain mutations [#7, #13]; mechanistically, HAX1 is required for G-CSF–triggered HCLS1 phosphorylation and downstream LEF-1 signaling in granulopoiesis, and acts within a CLPB/HAX1/HSP27 axis governing mitochondrial proteostasis and neutrophil differentiation [#23, #38]. In the heart, HAX1 binds phospholamban and SERCA2a to inhibit cardiac calcium cycling and contractility, mediating roughly half of phospholamban's inhibitory activity, and protects against ischemia/reperfusion injury via Hsp90/IRE-1 and NOX4-linked redox mechanisms [#9, #15, #32, #33]. HAX1 also drives cell migration by coupling Gα13, RhoA, Rac1, cortactin, and the microtubule end-binding protein EB2 to regulate the actin cytoskeleton and focal adhesion turnover [#5, #20, #30], and as a Kv3.3 auxiliary subunit it recruits Arp2/3 to build cortical actin that controls channel inactivation in neurons [#31]. As an RNA-binding protein it binds specific 3'UTRs (vimentin, DNA polymerase beta) and shuttles between nucleus and cytoplasm via exportin-1 to influence target mRNA levels [#3, #10, #21]. HAX1 abundance is tightly controlled by PEST-dependent proteasomal turnover, PRKCD-directed SCF(FBXO25) ubiquitination, and EIF3H-mediated deubiquitination, the latter promoting RAF1/MEK/ERK signaling in colorectal cancer [#24, #27, #39].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established HAX1's existence and primary biochemical character by showing it is a mitochondrial/ER protein that directly binds the kinase substrate HS1, defining it as an intracellular adaptor.\",\n      \"evidence\": \"Yeast two-hybrid, reciprocal Co-IP, deletion mapping, and confocal microscopy\",\n      \"pmids\": [\"9058808\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of HS1 binding undefined\", \"No enzymatic activity identified for HAX1 itself\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified HAX1 as a sequence-specific RNA-binding protein, opening a post-transcriptional regulatory role beyond protein scaffolding.\",\n      \"evidence\": \"Yeast three-hybrid, in vitro RNA binding, and RNA affinity pulldown for vimentin 3'UTR\",\n      \"pmids\": [\"12466525\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional effect on vimentin mRNA fate not shown\", \"In vivo relevance of the eEF-1gamma complex unestablished\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Connected HAX1 to apoptotic signaling at two levels — as a protease substrate and as a migration regulator — linking it to mitochondrial death pathways and Rho-family GTPases.\",\n      \"evidence\": \"In vitro/in vivo Omi/HtrA2 cleavage assays (mnd2 mutant) and Gα13 Co-IP with siRNA migration and RhoA/Rac activity assays\",\n      \"pmids\": [\"15371414\", \"15339924\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HAX1 cleavage is cause or consequence of death not fully resolved\", \"Mechanism by which HAX1 reciprocally tunes RhoA vs Rac unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined HAX1's core anti-apoptotic mechanism and its disease relevance by showing caspase-9 inhibition and that loss-of-function mutations cause severe congenital neutropenia via mitochondrial dysfunction.\",\n      \"evidence\": \"Cell-free caspase activation assay and positional cloning with mitochondrial membrane potential/apoptosis assays in patient myeloid cells\",\n      \"pmids\": [\"16857965\", \"17187068\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a single adaptor protects mitochondrial potential in myeloid cells specifically\", \"Structural basis of caspase-9 inhibition unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Placed HAX1 within a defined mitochondrial protease module and linked it to cardiac calcium handling, while isoform analysis explained the neurological phenotype of SCN.\",\n      \"evidence\": \"Hax1 KO mouse with PARL/HtrA2 epistasis; PLN and SERCA2 domain mapping/Co-IP; SCN isoform genotype-phenotype analysis\",\n      \"pmids\": [\"18288109\", \"17241641\", \"18971376\", \"18337561\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Compartmental feasibility of the PARL interaction later disputed\", \"Quantitative contribution of HAX1 to SERCA2 regulation not yet measured\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Tested and challenged the PARL model while quantifying HAX1's role in cardiac contractility, refining where HAX1 acts within the calcium-handling apparatus.\",\n      \"evidence\": \"In vivo localization/sequence analysis arguing against PARL interaction; cardiac overexpression/knockdown with PLN ablation rescue; isoform-specific subcellular targeting by immuno-EM\",\n      \"pmids\": [\"19680265\", \"19920172\", \"19913549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conflict over the PARL interaction (idx 17, Low) remains unreconciled\", \"Lack of BH domains argues against simple Bcl-2-family classification\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed HAX1 is targeted by cytotoxic-lymphocyte effector mechanisms and that its cleavage products actively drive mitochondrial depolarization, refining how its loss promotes death.\",\n      \"evidence\": \"In vitro granzyme B cleavage, uncleavable mutant overexpression, and cyclophilin-D-dependent membrane potential assays; XIAP SPR/ubiquitination assays\",\n      \"pmids\": [\"20388708\", \"20171186\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological contexts of granzyme-B cleavage of HAX1 in vivo\", \"Whether XIAP stabilization operates in the same cells as caspase-9 inhibition\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined HAX1's nucleocytoplasmic shuttling and post-transcriptional functions, its degradation control, and the molecular basis of its requirement in granulopoiesis.\",\n      \"evidence\": \"NES mutagenesis/leptomycin B and P-body colocalization; PEST-deletion ubiquitination assays; HCLS1 phosphorylation/LEF-1 nuclear transport in patient cells and HCLS1-KO mouse\",\n      \"pmids\": [\"23164465\", \"22827267\", \"23001182\", \"23055567\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signals coupling stress to HAX1 nuclear export not defined\", \"How HAX1 enables HCLS1 phosphorylation mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Established kinase-directed, ubiquitin-mediated control of HAX1 abundance and its dimerization-dependent, isoform-specific apoptotic output, with direct relevance to lymphoma.\",\n      \"evidence\": \"PRKCD/SCF(FBXO25) ubiquitination and phosphodegron analysis in MCL models; SPR dimer kinetics with cytochrome c release and infarction assays; Rac1/cortactin domain mapping\",\n      \"pmids\": [\"25419709\", \"24347163\", \"25053987\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How pro- and anti-apoptotic isoforms are balanced in normal tissues\", \"Whether FBXO25 degradation of HAX1 operates outside apoptotic stress\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined an Hsp90-centered chaperone-trafficking logic by which HAX1 simultaneously suppresses IRE-1 ER stress signaling and destabilizes cyclophilin-D to limit mitochondrial permeability transition.\",\n      \"evidence\": \"Cardiac overexpression and heterozygous-KO mice, HAX1/Hsp90 Co-IP, 17-AAG pharmacology, CypD ablation and mPTP/ubiquitination assays\",\n      \"pmids\": [\"22982986\", \"26553996\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of HAX1's Hsp90 sequestration across compartments\", \"How HAX1 partitions Hsp90 between IRE-1, PLN-SERCA2a, and CypD\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined HAX1 as a Kv3.3 auxiliary subunit that nucleates an Arp2/3-based cortical actin network controlling channel inactivation, linking its cytoskeletal role to neuronal disease mutations.\",\n      \"evidence\": \"Co-IP, cytochalasin-D resistance, electrophysiology, and disease-mutant analysis in stem-cell-derived neurons; EB2 interactome with focal adhesion/migration assays\",\n      \"pmids\": [\"26997484\", \"26527684\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How HAX1 spatially couples Kv3.3, Arp2/3, and EB2 simultaneously\", \"Whether neuronal actin role connects to SCN neurological phenotype\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Quantified endogenous HAX1's contribution to cardiac calcium regulation and uncovered a redox dimension whereby HAX1 protects SERCA2a from oxidative proteolysis via NOX4.\",\n      \"evidence\": \"Cardiac-specific inducible KO with SERCA2a Ca2+-affinity and PLN-SERCA2a Co-IP; ROS/oxidation assays and HAX1/NOX4 Co-IP with NOX inhibition\",\n      \"pmids\": [\"29150445\", \"29169992\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular mechanism of HAX1-NOX4 functional coupling\", \"Whether redox role generalizes beyond cardiac SR\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended HAX1's calcium-handling and metabolic roles to liver, identifying InsP3R1 as a partner controlling ER-mitochondria calcium transfer, mitochondrial substrate utilization, and bile acid recirculation.\",\n      \"evidence\": \"Liver-specific HAX1 KO mouse with Co-IP, calcium assays, metabolic phenotyping, and PDH activity\",\n      \"pmids\": [\"32079675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the InsP3R1 axis operates in non-hepatic tissues\", \"Mechanism linking HAX1 loss to BSEP elevation in vivo\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a CLPB/HAX1/HSP27 mitochondrial proteostasis axis that explains HAX1's requirement in neutrophil differentiation beyond its classical anti-apoptotic activity.\",\n      \"evidence\": \"SILAC proteomics in HAX1-deficient cells/mice with PRKD2/HSP27 quantification and functional HSP27 reconstitution\",\n      \"pmids\": [\"35499078\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How HAX1 mechanistically controls mitochondrial protein turnover\", \"Direct biochemical link between HAX1 and CLPB unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established deubiquitinase-mediated stabilization of HAX1 as an oncogenic driver, connecting HAX1 abundance control to RAF1/MEK/ERK signaling in colorectal cancer.\",\n      \"evidence\": \"EIF3H deubiquitination/Co-IP assays, conditional Eif3h-KO mouse, RAF1-MEK1-ERK1 interaction assays, and patient-derived xenografts\",\n      \"pmids\": [\"38514606\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How HAX1 scaffolds the RAF1-MEK-ERK module mechanistically\", \"Whether EIF3H-HAX1 axis operates in non-colorectal contexts\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HAX1's many compartment-specific activities — mitochondrial apoptosis control, ER/SR calcium handling, cytoskeletal migration, RNA binding, and proteostasis — are integrated or selectively engaged in a given cell type remains unresolved, and no high-resolution structure of HAX1 or its complexes has been defined in this corpus.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of HAX1 or its interaction interfaces\", \"Unclear how isoform composition dictates which functional module dominates\", \"Compartmental disagreement over key interactions (e.g., PARL) not reconciled\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 5, 11, 31]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [8, 9, 15, 19, 29, 32]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [3, 10, 21]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [25, 29]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 4, 11, 16, 18]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 2, 12, 16, 25]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [10, 21]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6, 31]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [8, 11, 18, 19, 29]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [25, 33]},\n      {\"term_id\": \"R-HSA-397014\", \"supporting_discovery_ids\": [9, 15, 32]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [24, 27, 38, 39]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 20, 39]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [3, 10, 21]}\n    ],\n    \"complexes\": [\"SCF(FBXO25) ubiquitin ligase substrate\", \"Kv3.3-HAX1-Arp2/3 cortical actin complex\", \"PLN-SERCA2a complex\"],\n    \"partners\": [\"HCLS1\", \"PLN\", \"ATP2A2\", \"HTRA2\", \"PARL\", \"XIAP\", \"CTTN\", \"KCNC3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}