{"gene":"MAL2","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2002,"finding":"MAL2 is an essential component of the machinery for basolateral-to-apical transcytosis in polarized hepatoma HepG2 cells. MAL2 resides selectively in lipid rafts and is predominantly distributed in a subapical endosome compartment. Depletion of endogenous MAL2 drastically blocked transcytotic transport of polymeric immunoglobulin receptor and GPI-anchored protein CD59 to the apical membrane, causing their accumulation in perinuclear endosome elements accessible to transferrin. Rescue with depletion-resistant exogenous MAL2 restored normal transcytosis.","method":"siRNA depletion, immunofluorescence, subcellular fractionation (raft isolation), exogenous rescue experiment in polarized HepG2 cells","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal rescue experiment, multiple orthogonal methods (knockdown, fractionation, immunofluorescence), foundational mechanistic paper replicated by subsequent studies","pmids":["12370246"],"is_preprint":false},{"year":2001,"finding":"MAL2 was identified as a novel four-transmembrane MAL proteolipid family member that physically interacts with TPD52-like proteins. The interaction was identified by yeast two-hybrid screening and confirmed by GST pull-down assay, where in vitro translated MAL2 specifically bound GST-Tpd52.","method":"Yeast two-hybrid screen, GST pull-down assay, in vitro translation","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus orthogonal GST pull-down confirmation, single lab","pmids":["11549320"],"is_preprint":false},{"year":2006,"finding":"MAL2 is a highly dynamic protein that mediates GPI-anchored protein transcytosis by shuttling between peripheral vesicular clusters and the apical surface. Live-cell imaging showed that after basolateral endocytosis of CD59, a fraction of MAL2 redistributed into peripheral vesicular clusters containing CD59 and transferrin receptor; following transferrin receptor segregation, these clusters fused into a MAL2-positive globular structure that moved toward the apical surface for cargo delivery. All steps were impaired in MAL2-depleted cells.","method":"Live-cell imaging, siRNA knockdown, fluorescence microscopy in polarized HepG2 cells","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — live-cell imaging of trafficking dynamics with loss-of-function validation, multiple cargo molecules tested, mechanistically detailed","pmids":["16445687"],"is_preprint":false},{"year":2010,"finding":"INF2, an atypical formin with actin polymerization and depolymerization activities, is a direct binding partner of MAL2. MAL2-positive vesicular carriers associate with short actin filaments during transcytosis in a process requiring INF2. Cdc42 and INF2 regulate MAL2 dynamics, and all three proteins are sequentially ordered in a pathway: Cdc42 activates INF2 (in a GTP-loaded-dependent manner), which then regulates MAL2-dependent transcytosis and lumen formation.","method":"Co-immunoprecipitation (binding partner identification), live-cell imaging, dominant-negative and knockdown experiments, epistasis analysis, organotypic culture lumen formation assay","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assays, epistasis established by sequential functional rescue, multiple orthogonal methods across two cell systems","pmids":["20493814"],"is_preprint":false},{"year":2010,"finding":"MAL2 selectively mediates delivery of polymeric IgA receptor (pIgA-R) from the Golgi to the plasma membrane in hepatic WIF-B cells. In Clone 9 cells lacking endogenous MAL2, pIgA-R was restricted to the Golgi when expressed alone, but co-expression with MAL2 permitted its delivery to the cell surface; this selectivity was not shared by DPPIV. MAL2 knockdown in WIF-B cells retained pIgA-R in the Golgi and impaired its basolateral delivery, demonstrating a cargo-selective role in biosynthetic trafficking.","method":"MAL2 knockdown (siRNA), overexpression in MAL2-null Clone 9 cells, surface delivery assays, fluorescence microscopy","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function and gain-of-function in MAL2-null cells, quantitative surface delivery assays, selective cargo discrimination demonstrated","pmids":["20444237"],"is_preprint":false},{"year":2011,"finding":"MAL, but not MAL2, self-associates and forms higher-order cholesterol-dependent complexes with apical proteins, and promotes formation of detergent-resistant membranes that recruit apical proteins. MAL2 does not share these biochemical properties, indicating that the two family members have distinct roles: MAL in raft coalescence/stabilization for direct apical trafficking and MAL2 in transcytotic pathway without such raft-organizing activity.","method":"Biochemical fractionation (detergent-resistant membrane isolation), sucrose density gradient centrifugation, co-immunoprecipitation, cholesterol depletion experiments","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical methods in single lab, negative result for MAL2 raft coalescence is informative and internally controlled against MAL","pmids":["21732912"],"is_preprint":false},{"year":2009,"finding":"MUC1 (mucin 1) is a direct binding partner of MAL2 in breast carcinoma cells. Yeast two-hybrid screening identified MUC1, and co-immunoprecipitation confirmed MAL2/MUC1 interaction in myc-tagged MAL2-expressing MCF-10A cells. Deletion mapping showed the first MAL2 transmembrane domain is required for MUC1 binding, whereas the MAL2 N-terminal domain binds D52-like proteins. MAL2 expression was associated with increased MUC1 detection at the cell surface.","method":"Yeast two-hybrid screening, co-immunoprecipitation, deletion mapping, confocal microscopy, sucrose density gradient centrifugation","journal":"BMC cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid confirmed by co-IP with domain mapping, single lab, multiple orthogonal methods","pmids":["19175940"],"is_preprint":false},{"year":2014,"finding":"MAL2 interacts with serine/threonine kinase 16 (STK16), a constitutively active Golgi-associated kinase, and together they function to sort secretory soluble cargo (albumin, haptoglobin) into the constitutive secretory pathway at the trans-Golgi network. Knockdown of MAL2 or expression of kinase-dead STK16 (E202A) impaired secretion and led to lysosomal degradation of albumin without affecting its synthesis or processing.","method":"Split-ubiquitin yeast two-hybrid, co-immunoprecipitation, immunofluorescence co-localization, siRNA knockdown, dominant-negative kinase-dead mutant expression, temperature-block and lysosome deacidification experiments","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid confirmed by co-IP and morphological co-localization, mechanistic follow-up with dominant-negative and knockdown, single lab","pmids":["25084525"],"is_preprint":false},{"year":2010,"finding":"MAL2 is a bona fide membrane constituent of synaptic vesicles (SVs) that is preferentially associated with VGLUT-1-containing (glutamatergic) nerve terminals. Subcellular fractionation and immunolocalization at light and electron microscopic levels confirmed its SV membrane localization, and quantitative proteomics showed selective enrichment in VGLUT-1 vesicle fractions compared to VGAT vesicles.","method":"Quantitative proteomics (SILAC-based), subcellular fractionation, immunolocalization (light and electron microscopy)","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative proteomics plus orthogonal immunolocalization at EM level, single study but multiple methods","pmids":["20053882"],"is_preprint":false},{"year":2021,"finding":"MAL2 promotes endocytosis of tumor antigens via direct interaction with the MHC-I complex and endosome-associated RAB proteins, thereby reducing antigen presentation on breast tumor cells. Depletion of MAL2 in breast tumor cells enhanced the cytotoxicity of tumor-infiltrating CD8+ T cells and suppressed breast tumor growth in preclinical models.","method":"Co-immunoprecipitation (MAL2 with MHC-I and RAB proteins), MAL2 depletion, CD8+ T cell cytotoxicity assays, in vivo preclinical tumor models","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding partners identified by co-IP, loss-of-function in multiple in vitro and in vivo models, mechanistic pathway established","pmids":["32990678"],"is_preprint":false},{"year":2021,"finding":"MAL2 mediates the formation of stable HER2 signaling complexes within lipid raft-rich membrane protrusions in breast cancer cells. MAL2 physically interacts with HER2 in lipid rafts (confirmed by proximity ligation assays), and MAL2-mediated lipid raft formation retains HER2 at the plasma membrane and enhances HER2 signaling. The HER2/MAL2 interaction in lipid rafts was enhanced in trastuzumab-resistant breast cancer cells. HER2/Ezrin/NHERF1/PMCA2 complex organization was resolved by super-resolution structured illumination microscopy.","method":"Proximity ligation assay, super-resolution structured illumination microscopy, lipid raft fractionation, calcium imaging","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proximity ligation assay plus super-resolution structural imaging, single lab, mechanistic link to HER2 signaling established","pmids":["34965434"],"is_preprint":false},{"year":2021,"finding":"MAL2 interacts with IQGAP1 to increase ERK1/2 phosphorylation levels and thereby promotes pancreatic cancer progression.","method":"Co-immunoprecipitation (MAL2-IQGAP1 interaction), western blot for ERK1/2 phosphorylation, overexpression and knockdown experiments","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single co-IP with downstream phosphorylation readout, single lab, limited mechanistic detail in abstract","pmids":["33780861"],"is_preprint":false},{"year":2009,"finding":"After differentiation, oligodendrocytic cell lines upregulate MAL2, which accumulates in a peri-centrosomal intracellular compartment sharing features of the apical recycling endosome/subapical compartment (ARE/SAC): co-localization with Rab11a, sensitivity to microtubule disruption by nocodazole, and exclusion of internalized transferrin. This MAL2-positive compartment is proposed as a trafficking station for myelin protein sorting.","method":"Immunofluorescence, confocal microscopy, nocodazole treatment, transferrin uptake assay, differentiation of Oli-neu and HOG cell lines","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment with functional perturbation (nocodazole), multiple markers, two cell lines, single lab","pmids":["19683524"],"is_preprint":false},{"year":2011,"finding":"PLP (proteolipid protein), the major myelin protein, directly interacts with MAL2 in oligodendrocytic HOG cells. Co-immunoprecipitation and immunofluorescence showed interaction and colocalization after PLP internalization from the plasma membrane, and ultrastructural analysis confirmed colocalization in vesicles and tubulovesicular structures.","method":"Co-immunoprecipitation, immunofluorescence, electron microscopy ultrastructural analysis in HOG cells expressing GFP-MAL2","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP confirmed by orthogonal EM ultrastructural colocalization, single lab","pmids":["21573057"],"is_preprint":false},{"year":2020,"finding":"MAL2 promotes actin-based protrusion formation with a reciprocal decrease in invadopodia in hepatocellular carcinoma-derived cells, and this activity requires a putative Ena/VASP homology 1 (EVH1) recognition motif. MAL2 overexpression decreased cell migration, invasion, and proliferation, while loss of MAL2 reversed these phenotypes, suggesting an anti-oncogenic/tumor suppressor role through actin remodeling.","method":"Exogenous MAL2 expression in MAL2-null Clone 9 cells, endogenous overexpression in Hep3B cells, site-directed mutagenesis of EVH1 motif, cell migration/invasion assays, invadopodia quantification","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis identifies functional motif, gain- and loss-of-function with specific morphological and functional readouts, single lab","pmids":["32059473"],"is_preprint":false},{"year":2025,"finding":"MAL2 and rab17 cooperate to selectively redistribute invadopodia proteins to actin- and cholesterol-dependent lateral protrusion tips, correlating with decreased matrix degradation. MAL2-mediated redistribution requires the putative EVH1 recognition motif, while rab17-mediated redistribution is GTP-dependent. MAL2 and rab17 interaction is GTP-dependent but not dependent on MAL2 EVH1 motifs. Both MAL2 and rab17 can redirect trafficking of newly synthesized membrane proteins from the Golgi to induced protrusions.","method":"Exogenous expression in MAL2/rab17-null Clone 9 cells, site-directed mutagenesis (EVH1 motif; GTP-binding mutants), matrix degradation assays, Golgi trafficking assays, fluorescence microscopy","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of functional motifs, gain-of-function in null cells, multiple orthogonal functional readouts, single lab","pmids":["39813085"],"is_preprint":false},{"year":2024,"finding":"MAL2 directly interacts with EGFR and stabilizes EGFR membrane localization in intrahepatic cholangiocarcinoma cells, activating the PI3K/AKT/SREBP-1 axis to promote lipid accumulation. MAL2-EGFR interaction was validated by molecular docking and co-immunoprecipitation.","method":"Co-immunoprecipitation, molecular docking, transcriptomics and metabolomics analyses, ICC organoids, MAL2 knockdown with functional readouts","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP confirmed interaction, orthogonal metabolomics/transcriptomics, organoid validation, single lab","pmids":["38866777"],"is_preprint":false},{"year":2024,"finding":"MAL2 transcription in endometrial cancer is directly activated by the transcription factor RAD21. RAD21 knockdown reduced MAL2 expression; MAL2 knockdown inhibited MHC-I surface expression and impaired antigen presentation-dependent CD8+ T cell cytotoxicity; MAL2 overexpression in the context of RAD21 knockdown restored immune evasion and tumor growth in mice.","method":"shRNA knockdown of MAL2 and RAD21, overexpression rescue experiments, in vivo xenograft model, CD8+ T cell cytotoxicity assays, MHC-I surface expression analysis","journal":"Cytotechnology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established by rescue experiment, in vivo validation, single lab with multiple methods","pmids":["38933871"],"is_preprint":false},{"year":2023,"finding":"MAL2 interacts with β-catenin in breast cancer cells. MAL2 silencing reduced expression of β-catenin and c-Myc; the β-catenin agonist SKL2001 partially rescued c-Myc downregulation and the inhibition of migration and invasion caused by MAL2 knockdown, placing MAL2 upstream of the β-catenin/c-Myc axis.","method":"Co-immunoprecipitation, immunofluorescence colocalization, western blot, β-catenin inhibitor and agonist treatment, siRNA knockdown","journal":"Cancer cell international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP identifies interaction, epistasis via pharmacological rescue is indirect, single lab, limited mechanistic depth","pmids":["37480012"],"is_preprint":false},{"year":2025,"finding":"E2F1 transcriptionally activates MAL2 expression in bladder cancer cells. ChIP and dual-luciferase reporter assays confirmed direct E2F1 binding to the MAL2 promoter. E2F1 overexpression promoted cancer cell malignant behavior and sunitinib resistance in a manner partially dependent on MAL2, as E2F1 silencing effects were rescued by MAL2 overexpression.","method":"Chromatin immunoprecipitation (ChIP), dual-luciferase reporter assay, overexpression and knockdown, xenograft mouse models","journal":"Journal of chemotherapy (Florence, Italy)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct transcriptional regulation confirmed by ChIP and luciferase assay, in vivo validation, single lab","pmids":["41013917"],"is_preprint":false},{"year":2026,"finding":"MAL2 knockdown in hepatocellular carcinoma cells impairs the secretion of CCL22, reducing regulatory T cell recruitment and decreasing production of immunosuppressive cytokines IL-10 and TGF-β, thereby reshaping the tumor immune microenvironment.","method":"shRNA knockdown, ELISA, immunofluorescence staining, mass cytometry, subcutaneous tumor model (H22 cells), scRNA-seq data analysis","journal":"Acta biochimica et biophysica Sinica","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional connection between MAL2 and CCL22 secretion established by knockdown and ELISA, but mechanism linking MAL2 trafficking function to CCL22 secretion is not resolved, single lab","pmids":["42212623"],"is_preprint":false}],"current_model":"MAL2 is a four-transmembrane raft-associated protein that functions as an essential component of the basolateral-to-apical transcytotic trafficking machinery in polarized epithelial cells, acting through dynamic vesicular carriers that require its EVH1 recognition motif for actin remodeling and interacting with binding partners including INF2/Cdc42 (for transcytosis), STK16 (for constitutive secretion at the TGN), RAB proteins, and MHC-I complexes (promoting their endocytosis and degradation to enable tumor immune evasion), while also forming functional complexes with HER2 in lipid rafts and interacting with EGFR, MUC1, TPD52-like proteins, and β-catenin in cancer contexts."},"narrative":{"mechanistic_narrative":"MAL2 is a four-transmembrane, raft-associated proteolipid that serves as an essential component of the basolateral-to-apical transcytotic trafficking machinery in polarized epithelial cells [PMID:12370246]. It resides selectively in lipid rafts and in a subapical endosome compartment, and is required for delivery of cargoes such as the polymeric immunoglobulin receptor and GPI-anchored CD59 to the apical surface; its depletion traps these cargoes in perinuclear endosomes, and depletion-resistant MAL2 restores transport [PMID:12370246]. Mechanistically, MAL2 is a highly dynamic carrier that shuttles between peripheral vesicular clusters and the apical surface, segregating cargo from transferrin receptor before apical delivery [PMID:16445687], and its vesicular carriers associate with short actin filaments through a pathway in which Cdc42 activates the formin INF2, which in turn regulates MAL2 dynamics and lumen formation [PMID:20493814]. Beyond transcytosis, MAL2 acts in cargo-selective biosynthetic and secretory trafficking: it is required for Golgi-to-surface delivery of the pIgA receptor in hepatic cells [PMID:20444237] and partners with the Golgi kinase STK16 to sort soluble secretory cargo (albumin, haptoglobin) into the constitutive secretory pathway at the trans-Golgi network, with loss of function diverting cargo to lysosomal degradation [PMID:25084525]. MAL2 binds TPD52-like proteins through its N-terminal domain [PMID:11549320, PMID:19175940] and shapes actin-based membrane protrusions via a putative EVH1 recognition motif, cooperating with rab17 to redistribute trafficking and reduce matrix-degrading invadopodia [PMID:32059473, PMID:39813085]. In cancer, MAL2 drives immune evasion by directly binding the MHC-I complex and endosomal RAB proteins to promote MHC-I endocytosis and reduce antigen presentation, limiting CD8+ T cell cytotoxicity [PMID:32990678]; this trafficking activity is exploited across tumor types where MAL2 also engages and stabilizes membrane receptors including HER2 in lipid rafts [PMID:34965434] and EGFR [PMID:38866777]. MAL2 expression is transcriptionally driven by RAD21 in endometrial cancer [PMID:38933871] and E2F1 in bladder cancer [PMID:41013917].","teleology":[{"year":2001,"claim":"Established MAL2 as a distinct four-transmembrane MAL-family proteolipid and identified its first molecular partner, framing it as a membrane protein with defined protein interactions.","evidence":"Yeast two-hybrid screen plus GST pull-down with in vitro translated MAL2 binding TPD52-like proteins","pmids":["11549320"],"confidence":"Medium","gaps":["Functional consequence of the TPD52 interaction not defined","No cellular trafficking role demonstrated yet"]},{"year":2002,"claim":"Defined the core function of MAL2 as an essential, raft-localized component of the apical transcytosis machinery, answering what cellular process the protein serves.","evidence":"siRNA depletion with reciprocal rescue, raft fractionation, and cargo trafficking assays in polarized HepG2 cells","pmids":["12370246"],"confidence":"High","gaps":["Molecular machinery downstream of MAL2 not identified","Mechanism of cargo selection unresolved"]},{"year":2006,"claim":"Resolved how MAL2 acts dynamically, showing it shuttles between peripheral vesicular clusters and the apical surface and physically segregates cargo from recycling markers.","evidence":"Live-cell imaging with siRNA knockdown of multiple cargoes in polarized HepG2 cells","pmids":["16445687"],"confidence":"High","gaps":["Cytoskeletal and regulatory machinery driving carrier movement not yet identified"]},{"year":2009,"claim":"Extended MAL2 partners and trafficking to cancer cell surface receptors and to non-epithelial membrane compartments, broadening its functional context.","evidence":"Yeast two-hybrid/co-IP domain mapping of MUC1 binding in breast cells; SILAC proteomics and EM localizing MAL2 to glutamatergic synaptic vesicles; localization to a Rab11a-positive ARE/SAC compartment in oligodendrocytes","pmids":["19175940","20053882","19683524"],"confidence":"Medium","gaps":["Functional role at synaptic vesicles not tested","Significance of MUC1 surface stabilization for tumor biology not established"]},{"year":2010,"claim":"Connected MAL2 trafficking to actin remodeling through a defined Cdc42-INF2-MAL2 epistatic pathway and demonstrated cargo-selective biosynthetic delivery, linking MAL2 to morphogenesis (lumen formation).","evidence":"Co-IP, dominant-negative/knockdown epistasis and organotypic lumen assays for INF2/Cdc42; gain- and loss-of-function for pIgA-R delivery in MAL2-null and WIF-B cells","pmids":["20493814","20444237"],"confidence":"High","gaps":["Structural basis of MAL2 association with actin filaments not resolved","How cargo selectivity is encoded remains unknown"]},{"year":2011,"claim":"Distinguished MAL2 biochemically from its paralog MAL and identified a myelin cargo, clarifying that MAL2 lacks raft-coalescing activity and functions in a distinct trafficking branch.","evidence":"Detergent-resistant membrane and density gradient fractionation comparing MAL vs MAL2; co-IP and EM colocalization of PLP with MAL2 in oligodendrocytic HOG cells","pmids":["21732912","21573057"],"confidence":"Medium","gaps":["Mechanism by which MAL2 mediates transcytosis without raft coalescence unclear","Physiological role in myelination not demonstrated in vivo"]},{"year":2014,"claim":"Identified a TGN-associated kinase partner and a constitutive secretory function, showing MAL2 sorts soluble cargo and prevents its lysosomal degradation.","evidence":"Split-ubiquitin Y2H, co-IP, kinase-dead STK16 and MAL2 knockdown with secretion and lysosome-deacidification assays","pmids":["25084525"],"confidence":"Medium","gaps":["How STK16 phosphorylation regulates MAL2 not defined","Direct substrate of STK16 in this pathway unknown"]},{"year":2020,"claim":"Mapped a functional EVH1 recognition motif and revealed a protrusion-promoting, anti-invasive role in liver cancer cells, suggesting context-dependent tumor-suppressive actin remodeling.","evidence":"Gain/loss-of-function and EVH1 site-directed mutagenesis in MAL2-null and Hep3B cells with migration/invasion and invadopodia assays","pmids":["32059473"],"confidence":"Medium","gaps":["EVH1 ligand partner not identified","Reconciliation with oncogenic roles in other cancers unresolved"]},{"year":2021,"claim":"Established MAL2 as a driver of tumor immune evasion through MHC-I endocytosis and linked it to receptor signaling complexes, defining its oncogenic mechanism.","evidence":"Co-IP of MAL2 with MHC-I/RAB proteins plus depletion, CD8+ T cell cytotoxicity and in vivo tumor models; PLA and super-resolution imaging of HER2/MAL2 lipid raft complexes; co-IP linking MAL2-IQGAP1 to ERK phosphorylation","pmids":["32990678","34965434","33780861"],"confidence":"High","gaps":["Which RAB proteins route MHC-I to degradation not specified","IQGAP1/ERK link rests on single co-IP without reciprocal validation"]},{"year":2024,"claim":"Expanded MAL2 receptor-stabilizing activity to EGFR and defined its transcriptional upstream regulators, connecting MAL2 expression to oncogenic signaling and immune evasion programs.","evidence":"Co-IP and molecular docking of MAL2-EGFR with metabolomics in ICC organoids; ChIP/luciferase for E2F1 and rescue experiments for RAD21 regulation of MAL2 with in vivo validation","pmids":["38866777","38933871","41013917"],"confidence":"Medium","gaps":["Whether receptor stabilization reflects MAL2 trafficking activity vs scaffolding not distinguished","Generality of transcriptional control across tissues unknown"]},{"year":2025,"claim":"Refined the protrusion mechanism by showing MAL2 cooperates with rab17 to redirect Golgi-derived cargo and invadopodia proteins to protrusion tips, separating EVH1-dependent and GTP-dependent steps.","evidence":"Site-directed mutagenesis of EVH1 and GTP-binding motifs in MAL2/rab17-null cells with matrix degradation and Golgi trafficking assays","pmids":["39813085"],"confidence":"Medium","gaps":["Direct EVH1 binding partner still unidentified","In vivo relevance of protrusion redistribution untested"]},{"year":2026,"claim":"Connected MAL2 to immunosuppressive cytokine secretion, suggesting it shapes the tumor immune microenvironment beyond MHC-I internalization.","evidence":"shRNA knockdown with ELISA, mass cytometry and tumor models linking MAL2 to CCL22 secretion and Treg recruitment in HCC","pmids":["42212623"],"confidence":"Low","gaps":["Mechanism linking MAL2 trafficking function to CCL22 secretion not resolved","Single-lab functional association without reciprocal validation"]},{"year":null,"claim":"How a single raft proteolipid integrates apical transcytosis, constitutive secretion, receptor stabilization, and immune-modulatory cargo trafficking through a common molecular mechanism remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of MAL2 or its cargo/EVH1 recognition","Mechanism of cargo selectivity across transcytotic vs biosynthetic routes unknown","Direct biophysical demonstration that MAL2 deforms or organizes carrier membranes lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,9,7]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[3,14,15]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0,2,12]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4,10]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[4,7,15]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[2,8,13]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[0,2,4]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,2,7]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[9,17]}],"complexes":[],"partners":["TPD52","MUC1","INF2","STK16","HER2","EGFR","RAB17","PLP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q969L2","full_name":"Protein MAL2","aliases":[],"length_aa":176,"mass_kda":19.1,"function":"Member of the machinery of polarized transport. Required for the indirect transcytotic route at the step of the egress of the transcytosing cargo from perinuclear endosomes in order for it to travel to the apical surface via a raft-dependent pathway","subcellular_location":"Cell membrane; Apical cell membrane; Endomembrane system; Cytoplasm, perinuclear region","url":"https://www.uniprot.org/uniprotkb/Q969L2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MAL2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":74,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MAL2","total_profiled":1310},"omim":[{"mim_id":"610982","title":"INVERTED FORMIN 2; INF2","url":"https://www.omim.org/entry/610982"},{"mim_id":"609684","title":"MAL PROTEOLIPID PROTEIN 2; MAL2","url":"https://www.omim.org/entry/609684"},{"mim_id":"188860","title":"MYELIN AND LYMPHOCYTE PROTEIN; MAL","url":"https://www.omim.org/entry/188860"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"esophagus","ntpm":238.5}],"url":"https://www.proteinatlas.org/search/MAL2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q969L2","domains":[{"cath_id":"1.20.120","chopping":"28-128_141-173","consensus_level":"high","plddt":91.5817,"start":28,"end":173}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q969L2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q969L2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q969L2-F1-predicted_aligned_error_v6.png","plddt_mean":84.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MAL2","jax_strain_url":"https://www.jax.org/strain/search?query=MAL2"},"sequence":{"accession":"Q969L2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q969L2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q969L2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q969L2"}},"corpus_meta":[{"pmid":"20053882","id":"PMC_20053882","title":"Quantitative comparison of glutamatergic and GABAergic synaptic vesicles unveils selectivity for few proteins including MAL2, a novel synaptic vesicle protein.","date":"2010","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/20053882","citation_count":150,"is_preprint":false},{"pmid":"12370246","id":"PMC_12370246","title":"MAL2, a novel raft protein of the MAL family, is an essential component of the machinery for transcytosis in hepatoma HepG2 cells.","date":"2002","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/12370246","citation_count":112,"is_preprint":false},{"pmid":"32990678","id":"PMC_32990678","title":"MAL2 drives immune evasion in breast cancer by suppressing tumor antigen presentation.","date":"2021","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/32990678","citation_count":97,"is_preprint":false},{"pmid":"20493814","id":"PMC_20493814","title":"The formin INF2 regulates basolateral-to-apical transcytosis and lumen formation in association with Cdc42 and MAL2.","date":"2010","source":"Developmental cell","url":"https://pubmed.ncbi.nlm.nih.gov/20493814","citation_count":83,"is_preprint":false},{"pmid":"11549320","id":"PMC_11549320","title":"Identification of MAL2, a novel member of the mal proteolipid family, though interactions with TPD52-like proteins in the yeast two-hybrid system.","date":"2001","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/11549320","citation_count":80,"is_preprint":false},{"pmid":"20846453","id":"PMC_20846453","title":"MAL2 and tumor protein D52 (TPD52) are frequently overexpressed in ovarian carcinoma, but differentially associated with histological subtype and patient outcome.","date":"2010","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/20846453","citation_count":56,"is_preprint":false},{"pmid":"15168355","id":"PMC_15168355","title":"Expression of MAL and MAL2, two elements of the protein machinery for raft-mediated transport, in normal and neoplastic human tissue.","date":"2004","source":"Histology and histopathology","url":"https://pubmed.ncbi.nlm.nih.gov/15168355","citation_count":40,"is_preprint":false},{"pmid":"30195491","id":"PMC_30195491","title":"MAL2 promotes proliferation, migration, and invasion through regulating epithelial-mesenchymal transition in breast cancer cell lines.","date":"2018","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/30195491","citation_count":38,"is_preprint":false},{"pmid":"25190476","id":"PMC_25190476","title":"Establishment of novel in vitro mouse chief cell and SPEM cultures identifies MAL2 as a marker of metaplasia in the stomach.","date":"2014","source":"American journal of physiology. 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\"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"MAL2 is an essential component of the machinery for basolateral-to-apical transcytosis in polarized hepatoma HepG2 cells. MAL2 resides selectively in lipid rafts and is predominantly distributed in a subapical endosome compartment. Depletion of endogenous MAL2 drastically blocked transcytotic transport of polymeric immunoglobulin receptor and GPI-anchored protein CD59 to the apical membrane, causing their accumulation in perinuclear endosome elements accessible to transferrin. Rescue with depletion-resistant exogenous MAL2 restored normal transcytosis.\",\n      \"method\": \"siRNA depletion, immunofluorescence, subcellular fractionation (raft isolation), exogenous rescue experiment in polarized HepG2 cells\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal rescue experiment, multiple orthogonal methods (knockdown, fractionation, immunofluorescence), foundational mechanistic paper replicated by subsequent studies\",\n      \"pmids\": [\"12370246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MAL2 was identified as a novel four-transmembrane MAL proteolipid family member that physically interacts with TPD52-like proteins. The interaction was identified by yeast two-hybrid screening and confirmed by GST pull-down assay, where in vitro translated MAL2 specifically bound GST-Tpd52.\",\n      \"method\": \"Yeast two-hybrid screen, GST pull-down assay, in vitro translation\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus orthogonal GST pull-down confirmation, single lab\",\n      \"pmids\": [\"11549320\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MAL2 is a highly dynamic protein that mediates GPI-anchored protein transcytosis by shuttling between peripheral vesicular clusters and the apical surface. Live-cell imaging showed that after basolateral endocytosis of CD59, a fraction of MAL2 redistributed into peripheral vesicular clusters containing CD59 and transferrin receptor; following transferrin receptor segregation, these clusters fused into a MAL2-positive globular structure that moved toward the apical surface for cargo delivery. All steps were impaired in MAL2-depleted cells.\",\n      \"method\": \"Live-cell imaging, siRNA knockdown, fluorescence microscopy in polarized HepG2 cells\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live-cell imaging of trafficking dynamics with loss-of-function validation, multiple cargo molecules tested, mechanistically detailed\",\n      \"pmids\": [\"16445687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"INF2, an atypical formin with actin polymerization and depolymerization activities, is a direct binding partner of MAL2. MAL2-positive vesicular carriers associate with short actin filaments during transcytosis in a process requiring INF2. Cdc42 and INF2 regulate MAL2 dynamics, and all three proteins are sequentially ordered in a pathway: Cdc42 activates INF2 (in a GTP-loaded-dependent manner), which then regulates MAL2-dependent transcytosis and lumen formation.\",\n      \"method\": \"Co-immunoprecipitation (binding partner identification), live-cell imaging, dominant-negative and knockdown experiments, epistasis analysis, organotypic culture lumen formation assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assays, epistasis established by sequential functional rescue, multiple orthogonal methods across two cell systems\",\n      \"pmids\": [\"20493814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MAL2 selectively mediates delivery of polymeric IgA receptor (pIgA-R) from the Golgi to the plasma membrane in hepatic WIF-B cells. In Clone 9 cells lacking endogenous MAL2, pIgA-R was restricted to the Golgi when expressed alone, but co-expression with MAL2 permitted its delivery to the cell surface; this selectivity was not shared by DPPIV. MAL2 knockdown in WIF-B cells retained pIgA-R in the Golgi and impaired its basolateral delivery, demonstrating a cargo-selective role in biosynthetic trafficking.\",\n      \"method\": \"MAL2 knockdown (siRNA), overexpression in MAL2-null Clone 9 cells, surface delivery assays, fluorescence microscopy\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function and gain-of-function in MAL2-null cells, quantitative surface delivery assays, selective cargo discrimination demonstrated\",\n      \"pmids\": [\"20444237\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MAL, but not MAL2, self-associates and forms higher-order cholesterol-dependent complexes with apical proteins, and promotes formation of detergent-resistant membranes that recruit apical proteins. MAL2 does not share these biochemical properties, indicating that the two family members have distinct roles: MAL in raft coalescence/stabilization for direct apical trafficking and MAL2 in transcytotic pathway without such raft-organizing activity.\",\n      \"method\": \"Biochemical fractionation (detergent-resistant membrane isolation), sucrose density gradient centrifugation, co-immunoprecipitation, cholesterol depletion experiments\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical methods in single lab, negative result for MAL2 raft coalescence is informative and internally controlled against MAL\",\n      \"pmids\": [\"21732912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MUC1 (mucin 1) is a direct binding partner of MAL2 in breast carcinoma cells. Yeast two-hybrid screening identified MUC1, and co-immunoprecipitation confirmed MAL2/MUC1 interaction in myc-tagged MAL2-expressing MCF-10A cells. Deletion mapping showed the first MAL2 transmembrane domain is required for MUC1 binding, whereas the MAL2 N-terminal domain binds D52-like proteins. MAL2 expression was associated with increased MUC1 detection at the cell surface.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation, deletion mapping, confocal microscopy, sucrose density gradient centrifugation\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid confirmed by co-IP with domain mapping, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"19175940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MAL2 interacts with serine/threonine kinase 16 (STK16), a constitutively active Golgi-associated kinase, and together they function to sort secretory soluble cargo (albumin, haptoglobin) into the constitutive secretory pathway at the trans-Golgi network. Knockdown of MAL2 or expression of kinase-dead STK16 (E202A) impaired secretion and led to lysosomal degradation of albumin without affecting its synthesis or processing.\",\n      \"method\": \"Split-ubiquitin yeast two-hybrid, co-immunoprecipitation, immunofluorescence co-localization, siRNA knockdown, dominant-negative kinase-dead mutant expression, temperature-block and lysosome deacidification experiments\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid confirmed by co-IP and morphological co-localization, mechanistic follow-up with dominant-negative and knockdown, single lab\",\n      \"pmids\": [\"25084525\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MAL2 is a bona fide membrane constituent of synaptic vesicles (SVs) that is preferentially associated with VGLUT-1-containing (glutamatergic) nerve terminals. Subcellular fractionation and immunolocalization at light and electron microscopic levels confirmed its SV membrane localization, and quantitative proteomics showed selective enrichment in VGLUT-1 vesicle fractions compared to VGAT vesicles.\",\n      \"method\": \"Quantitative proteomics (SILAC-based), subcellular fractionation, immunolocalization (light and electron microscopy)\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative proteomics plus orthogonal immunolocalization at EM level, single study but multiple methods\",\n      \"pmids\": [\"20053882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MAL2 promotes endocytosis of tumor antigens via direct interaction with the MHC-I complex and endosome-associated RAB proteins, thereby reducing antigen presentation on breast tumor cells. Depletion of MAL2 in breast tumor cells enhanced the cytotoxicity of tumor-infiltrating CD8+ T cells and suppressed breast tumor growth in preclinical models.\",\n      \"method\": \"Co-immunoprecipitation (MAL2 with MHC-I and RAB proteins), MAL2 depletion, CD8+ T cell cytotoxicity assays, in vivo preclinical tumor models\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding partners identified by co-IP, loss-of-function in multiple in vitro and in vivo models, mechanistic pathway established\",\n      \"pmids\": [\"32990678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MAL2 mediates the formation of stable HER2 signaling complexes within lipid raft-rich membrane protrusions in breast cancer cells. MAL2 physically interacts with HER2 in lipid rafts (confirmed by proximity ligation assays), and MAL2-mediated lipid raft formation retains HER2 at the plasma membrane and enhances HER2 signaling. The HER2/MAL2 interaction in lipid rafts was enhanced in trastuzumab-resistant breast cancer cells. HER2/Ezrin/NHERF1/PMCA2 complex organization was resolved by super-resolution structured illumination microscopy.\",\n      \"method\": \"Proximity ligation assay, super-resolution structured illumination microscopy, lipid raft fractionation, calcium imaging\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proximity ligation assay plus super-resolution structural imaging, single lab, mechanistic link to HER2 signaling established\",\n      \"pmids\": [\"34965434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MAL2 interacts with IQGAP1 to increase ERK1/2 phosphorylation levels and thereby promotes pancreatic cancer progression.\",\n      \"method\": \"Co-immunoprecipitation (MAL2-IQGAP1 interaction), western blot for ERK1/2 phosphorylation, overexpression and knockdown experiments\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single co-IP with downstream phosphorylation readout, single lab, limited mechanistic detail in abstract\",\n      \"pmids\": [\"33780861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"After differentiation, oligodendrocytic cell lines upregulate MAL2, which accumulates in a peri-centrosomal intracellular compartment sharing features of the apical recycling endosome/subapical compartment (ARE/SAC): co-localization with Rab11a, sensitivity to microtubule disruption by nocodazole, and exclusion of internalized transferrin. This MAL2-positive compartment is proposed as a trafficking station for myelin protein sorting.\",\n      \"method\": \"Immunofluorescence, confocal microscopy, nocodazole treatment, transferrin uptake assay, differentiation of Oli-neu and HOG cell lines\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment with functional perturbation (nocodazole), multiple markers, two cell lines, single lab\",\n      \"pmids\": [\"19683524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PLP (proteolipid protein), the major myelin protein, directly interacts with MAL2 in oligodendrocytic HOG cells. Co-immunoprecipitation and immunofluorescence showed interaction and colocalization after PLP internalization from the plasma membrane, and ultrastructural analysis confirmed colocalization in vesicles and tubulovesicular structures.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, electron microscopy ultrastructural analysis in HOG cells expressing GFP-MAL2\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP confirmed by orthogonal EM ultrastructural colocalization, single lab\",\n      \"pmids\": [\"21573057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MAL2 promotes actin-based protrusion formation with a reciprocal decrease in invadopodia in hepatocellular carcinoma-derived cells, and this activity requires a putative Ena/VASP homology 1 (EVH1) recognition motif. MAL2 overexpression decreased cell migration, invasion, and proliferation, while loss of MAL2 reversed these phenotypes, suggesting an anti-oncogenic/tumor suppressor role through actin remodeling.\",\n      \"method\": \"Exogenous MAL2 expression in MAL2-null Clone 9 cells, endogenous overexpression in Hep3B cells, site-directed mutagenesis of EVH1 motif, cell migration/invasion assays, invadopodia quantification\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis identifies functional motif, gain- and loss-of-function with specific morphological and functional readouts, single lab\",\n      \"pmids\": [\"32059473\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MAL2 and rab17 cooperate to selectively redistribute invadopodia proteins to actin- and cholesterol-dependent lateral protrusion tips, correlating with decreased matrix degradation. MAL2-mediated redistribution requires the putative EVH1 recognition motif, while rab17-mediated redistribution is GTP-dependent. MAL2 and rab17 interaction is GTP-dependent but not dependent on MAL2 EVH1 motifs. Both MAL2 and rab17 can redirect trafficking of newly synthesized membrane proteins from the Golgi to induced protrusions.\",\n      \"method\": \"Exogenous expression in MAL2/rab17-null Clone 9 cells, site-directed mutagenesis (EVH1 motif; GTP-binding mutants), matrix degradation assays, Golgi trafficking assays, fluorescence microscopy\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of functional motifs, gain-of-function in null cells, multiple orthogonal functional readouts, single lab\",\n      \"pmids\": [\"39813085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MAL2 directly interacts with EGFR and stabilizes EGFR membrane localization in intrahepatic cholangiocarcinoma cells, activating the PI3K/AKT/SREBP-1 axis to promote lipid accumulation. MAL2-EGFR interaction was validated by molecular docking and co-immunoprecipitation.\",\n      \"method\": \"Co-immunoprecipitation, molecular docking, transcriptomics and metabolomics analyses, ICC organoids, MAL2 knockdown with functional readouts\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP confirmed interaction, orthogonal metabolomics/transcriptomics, organoid validation, single lab\",\n      \"pmids\": [\"38866777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MAL2 transcription in endometrial cancer is directly activated by the transcription factor RAD21. RAD21 knockdown reduced MAL2 expression; MAL2 knockdown inhibited MHC-I surface expression and impaired antigen presentation-dependent CD8+ T cell cytotoxicity; MAL2 overexpression in the context of RAD21 knockdown restored immune evasion and tumor growth in mice.\",\n      \"method\": \"shRNA knockdown of MAL2 and RAD21, overexpression rescue experiments, in vivo xenograft model, CD8+ T cell cytotoxicity assays, MHC-I surface expression analysis\",\n      \"journal\": \"Cytotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by rescue experiment, in vivo validation, single lab with multiple methods\",\n      \"pmids\": [\"38933871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MAL2 interacts with β-catenin in breast cancer cells. MAL2 silencing reduced expression of β-catenin and c-Myc; the β-catenin agonist SKL2001 partially rescued c-Myc downregulation and the inhibition of migration and invasion caused by MAL2 knockdown, placing MAL2 upstream of the β-catenin/c-Myc axis.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence colocalization, western blot, β-catenin inhibitor and agonist treatment, siRNA knockdown\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP identifies interaction, epistasis via pharmacological rescue is indirect, single lab, limited mechanistic depth\",\n      \"pmids\": [\"37480012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"E2F1 transcriptionally activates MAL2 expression in bladder cancer cells. ChIP and dual-luciferase reporter assays confirmed direct E2F1 binding to the MAL2 promoter. E2F1 overexpression promoted cancer cell malignant behavior and sunitinib resistance in a manner partially dependent on MAL2, as E2F1 silencing effects were rescued by MAL2 overexpression.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), dual-luciferase reporter assay, overexpression and knockdown, xenograft mouse models\",\n      \"journal\": \"Journal of chemotherapy (Florence, Italy)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct transcriptional regulation confirmed by ChIP and luciferase assay, in vivo validation, single lab\",\n      \"pmids\": [\"41013917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"MAL2 knockdown in hepatocellular carcinoma cells impairs the secretion of CCL22, reducing regulatory T cell recruitment and decreasing production of immunosuppressive cytokines IL-10 and TGF-β, thereby reshaping the tumor immune microenvironment.\",\n      \"method\": \"shRNA knockdown, ELISA, immunofluorescence staining, mass cytometry, subcutaneous tumor model (H22 cells), scRNA-seq data analysis\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional connection between MAL2 and CCL22 secretion established by knockdown and ELISA, but mechanism linking MAL2 trafficking function to CCL22 secretion is not resolved, single lab\",\n      \"pmids\": [\"42212623\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MAL2 is a four-transmembrane raft-associated protein that functions as an essential component of the basolateral-to-apical transcytotic trafficking machinery in polarized epithelial cells, acting through dynamic vesicular carriers that require its EVH1 recognition motif for actin remodeling and interacting with binding partners including INF2/Cdc42 (for transcytosis), STK16 (for constitutive secretion at the TGN), RAB proteins, and MHC-I complexes (promoting their endocytosis and degradation to enable tumor immune evasion), while also forming functional complexes with HER2 in lipid rafts and interacting with EGFR, MUC1, TPD52-like proteins, and β-catenin in cancer contexts.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MAL2 is a four-transmembrane, raft-associated proteolipid that serves as an essential component of the basolateral-to-apical transcytotic trafficking machinery in polarized epithelial cells [#0]. It resides selectively in lipid rafts and in a subapical endosome compartment, and is required for delivery of cargoes such as the polymeric immunoglobulin receptor and GPI-anchored CD59 to the apical surface; its depletion traps these cargoes in perinuclear endosomes, and depletion-resistant MAL2 restores transport [#0]. Mechanistically, MAL2 is a highly dynamic carrier that shuttles between peripheral vesicular clusters and the apical surface, segregating cargo from transferrin receptor before apical delivery [#2], and its vesicular carriers associate with short actin filaments through a pathway in which Cdc42 activates the formin INF2, which in turn regulates MAL2 dynamics and lumen formation [#3]. Beyond transcytosis, MAL2 acts in cargo-selective biosynthetic and secretory trafficking: it is required for Golgi-to-surface delivery of the pIgA receptor in hepatic cells [#4] and partners with the Golgi kinase STK16 to sort soluble secretory cargo (albumin, haptoglobin) into the constitutive secretory pathway at the trans-Golgi network, with loss of function diverting cargo to lysosomal degradation [#7]. MAL2 binds TPD52-like proteins through its N-terminal domain [#1, #6] and shapes actin-based membrane protrusions via a putative EVH1 recognition motif, cooperating with rab17 to redistribute trafficking and reduce matrix-degrading invadopodia [#14, #15]. In cancer, MAL2 drives immune evasion by directly binding the MHC-I complex and endosomal RAB proteins to promote MHC-I endocytosis and reduce antigen presentation, limiting CD8+ T cell cytotoxicity [#9]; this trafficking activity is exploited across tumor types where MAL2 also engages and stabilizes membrane receptors including HER2 in lipid rafts [#10] and EGFR [#16]. MAL2 expression is transcriptionally driven by RAD21 in endometrial cancer [#17] and E2F1 in bladder cancer [#19].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established MAL2 as a distinct four-transmembrane MAL-family proteolipid and identified its first molecular partner, framing it as a membrane protein with defined protein interactions.\",\n      \"evidence\": \"Yeast two-hybrid screen plus GST pull-down with in vitro translated MAL2 binding TPD52-like proteins\",\n      \"pmids\": [\"11549320\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the TPD52 interaction not defined\", \"No cellular trafficking role demonstrated yet\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined the core function of MAL2 as an essential, raft-localized component of the apical transcytosis machinery, answering what cellular process the protein serves.\",\n      \"evidence\": \"siRNA depletion with reciprocal rescue, raft fractionation, and cargo trafficking assays in polarized HepG2 cells\",\n      \"pmids\": [\"12370246\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery downstream of MAL2 not identified\", \"Mechanism of cargo selection unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Resolved how MAL2 acts dynamically, showing it shuttles between peripheral vesicular clusters and the apical surface and physically segregates cargo from recycling markers.\",\n      \"evidence\": \"Live-cell imaging with siRNA knockdown of multiple cargoes in polarized HepG2 cells\",\n      \"pmids\": [\"16445687\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cytoskeletal and regulatory machinery driving carrier movement not yet identified\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extended MAL2 partners and trafficking to cancer cell surface receptors and to non-epithelial membrane compartments, broadening its functional context.\",\n      \"evidence\": \"Yeast two-hybrid/co-IP domain mapping of MUC1 binding in breast cells; SILAC proteomics and EM localizing MAL2 to glutamatergic synaptic vesicles; localization to a Rab11a-positive ARE/SAC compartment in oligodendrocytes\",\n      \"pmids\": [\"19175940\", \"20053882\", \"19683524\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role at synaptic vesicles not tested\", \"Significance of MUC1 surface stabilization for tumor biology not established\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Connected MAL2 trafficking to actin remodeling through a defined Cdc42-INF2-MAL2 epistatic pathway and demonstrated cargo-selective biosynthetic delivery, linking MAL2 to morphogenesis (lumen formation).\",\n      \"evidence\": \"Co-IP, dominant-negative/knockdown epistasis and organotypic lumen assays for INF2/Cdc42; gain- and loss-of-function for pIgA-R delivery in MAL2-null and WIF-B cells\",\n      \"pmids\": [\"20493814\", \"20444237\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MAL2 association with actin filaments not resolved\", \"How cargo selectivity is encoded remains unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Distinguished MAL2 biochemically from its paralog MAL and identified a myelin cargo, clarifying that MAL2 lacks raft-coalescing activity and functions in a distinct trafficking branch.\",\n      \"evidence\": \"Detergent-resistant membrane and density gradient fractionation comparing MAL vs MAL2; co-IP and EM colocalization of PLP with MAL2 in oligodendrocytic HOG cells\",\n      \"pmids\": [\"21732912\", \"21573057\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which MAL2 mediates transcytosis without raft coalescence unclear\", \"Physiological role in myelination not demonstrated in vivo\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified a TGN-associated kinase partner and a constitutive secretory function, showing MAL2 sorts soluble cargo and prevents its lysosomal degradation.\",\n      \"evidence\": \"Split-ubiquitin Y2H, co-IP, kinase-dead STK16 and MAL2 knockdown with secretion and lysosome-deacidification assays\",\n      \"pmids\": [\"25084525\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How STK16 phosphorylation regulates MAL2 not defined\", \"Direct substrate of STK16 in this pathway unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped a functional EVH1 recognition motif and revealed a protrusion-promoting, anti-invasive role in liver cancer cells, suggesting context-dependent tumor-suppressive actin remodeling.\",\n      \"evidence\": \"Gain/loss-of-function and EVH1 site-directed mutagenesis in MAL2-null and Hep3B cells with migration/invasion and invadopodia assays\",\n      \"pmids\": [\"32059473\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"EVH1 ligand partner not identified\", \"Reconciliation with oncogenic roles in other cancers unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established MAL2 as a driver of tumor immune evasion through MHC-I endocytosis and linked it to receptor signaling complexes, defining its oncogenic mechanism.\",\n      \"evidence\": \"Co-IP of MAL2 with MHC-I/RAB proteins plus depletion, CD8+ T cell cytotoxicity and in vivo tumor models; PLA and super-resolution imaging of HER2/MAL2 lipid raft complexes; co-IP linking MAL2-IQGAP1 to ERK phosphorylation\",\n      \"pmids\": [\"32990678\", \"34965434\", \"33780861\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which RAB proteins route MHC-I to degradation not specified\", \"IQGAP1/ERK link rests on single co-IP without reciprocal validation\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Expanded MAL2 receptor-stabilizing activity to EGFR and defined its transcriptional upstream regulators, connecting MAL2 expression to oncogenic signaling and immune evasion programs.\",\n      \"evidence\": \"Co-IP and molecular docking of MAL2-EGFR with metabolomics in ICC organoids; ChIP/luciferase for E2F1 and rescue experiments for RAD21 regulation of MAL2 with in vivo validation\",\n      \"pmids\": [\"38866777\", \"38933871\", \"41013917\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether receptor stabilization reflects MAL2 trafficking activity vs scaffolding not distinguished\", \"Generality of transcriptional control across tissues unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Refined the protrusion mechanism by showing MAL2 cooperates with rab17 to redirect Golgi-derived cargo and invadopodia proteins to protrusion tips, separating EVH1-dependent and GTP-dependent steps.\",\n      \"evidence\": \"Site-directed mutagenesis of EVH1 and GTP-binding motifs in MAL2/rab17-null cells with matrix degradation and Golgi trafficking assays\",\n      \"pmids\": [\"39813085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct EVH1 binding partner still unidentified\", \"In vivo relevance of protrusion redistribution untested\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Connected MAL2 to immunosuppressive cytokine secretion, suggesting it shapes the tumor immune microenvironment beyond MHC-I internalization.\",\n      \"evidence\": \"shRNA knockdown with ELISA, mass cytometry and tumor models linking MAL2 to CCL22 secretion and Treg recruitment in HCC\",\n      \"pmids\": [\"42212623\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Mechanism linking MAL2 trafficking function to CCL22 secretion not resolved\", \"Single-lab functional association without reciprocal validation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single raft proteolipid integrates apical transcytosis, constitutive secretion, receptor stabilization, and immune-modulatory cargo trafficking through a common molecular mechanism remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of MAL2 or its cargo/EVH1 recognition\", \"Mechanism of cargo selectivity across transcytotic vs biosynthetic routes unknown\", \"Direct biophysical demonstration that MAL2 deforms or organizes carrier membranes lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 9, 7]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [3, 14, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0, 2, 12]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 10]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [4, 7, 15]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [2, 8, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 2, 7]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [9, 17]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TPD52\", \"MUC1\", \"INF2\", \"STK16\", \"HER2\", \"EGFR\", \"RAB17\", \"PLP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}