{"gene":"MCOLN2","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2006,"finding":"TRPML2 homomultimers localize to lysosomes, and TRPML2 can form homo- and heteromultimers with TRPML1 and TRPML3. When coexpressed, TRPML2 dictates lysosomal localization of TRPML3 (which otherwise resides in the ER), but TRPML3 does not cause retention of TRPML2 in the ER, establishing a hierarchy of subcellular localization control.","method":"Co-immunoprecipitation (homo/heteromultimer formation), fluorescence microscopy of coexpressed proteins, lysosomal targeting mutant analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP for multimerization, systematic coexpression with localization mutants, replicated across multiple TRPML combinations","pmids":["16606612"],"is_preprint":false},{"year":2009,"finding":"Wild-type human TRPML2 is a constitutively active, inwardly rectifying, nonselective cation channel permeable to Ca2+ at the plasma membrane, inhibited by low extracytosolic pH but not regulated by Ca2+. Constitutive activity causes cell death by Ca2+ overload. The varitint-waddler (Va) gain-of-function mutation (Ala→Pro in TM5) renders TRPML2lv constitutively active.","method":"Electrophysiology (whole-cell patch-clamp), site-directed mutagenesis, cell viability assays, heterologous expression in mammalian cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro electrophysiology with mutagenesis, multiple channel properties measured, single lab with orthogonal readouts","pmids":["19940139"],"is_preprint":false},{"year":2009,"finding":"TRPML1 plays a role in the tissue-specific transcriptional regulation of TRPML2: knockdown of endogenous TRPML1 in HEK-293 cells reduces human TRPML2 transcript levels, which are restored by TRPML1 overexpression; conversely, TRPML1 activators (NAADP, H-89) upregulate TRPML2sv transcripts in primary mouse lymphoid cells.","method":"RNA interference, quantitative RT-PCR, pharmacological activation of TRPML1, overexpression rescue","journal":"Pflugers Archiv : European journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi plus rescue plus pharmacological activation, single lab, multiple orthogonal approaches","pmids":["19763610"],"is_preprint":false},{"year":2012,"finding":"TRPML2 is activated by lowering extracellular sodium concentration and by a subset of small chemical compounds (sulfonamide-related) previously identified as TRPML3 activators, confirming functional activity at the plasma membrane and suggesting shared gating mechanisms with TRPML3. Mutagenesis of Glu-361 in the second extracellular loop of TRPML3 significantly impacts sodium-mediated block, pointing to negatively charged extracellular loop residues as determinants of sodium inhibition.","method":"Electrophysiology (whole-cell patch-clamp), site-directed mutagenesis, pharmacological screen with small molecules","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro electrophysiology with mutagenesis for TRPML3 gating mechanism; TRPML2 activation confirmed pharmacologically in same study, single lab","pmids":["22753890"],"is_preprint":false},{"year":2014,"finding":"PAX5 (BSAP) is the transcriptional activator of the MCOLN2 gene. Heterologous PAX5 expression in HEK-293 cells significantly increases endogenous MCOLN2 transcript and TRPML2 protein levels; PAX5 RNAi reduces this effect. Site-directed mutagenesis identified the core promoter and PAX5 binding region between −79 and −60 bp upstream of the transcriptional start site.","method":"Dual-luciferase reporter assay, PAX5 overexpression, RNA interference, site-directed mutagenesis of promoter, RT-PCR and Western blot","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter mutagenesis plus OE plus RNAi rescue, single lab, multiple orthogonal approaches","pmids":["25445271"],"is_preprint":false},{"year":2015,"finding":"Endogenous TRPML2 localizes primarily to recycling endosomes in macrophages (distinct from TRPML1 in late endosomes and TRPML3 in early endosomes). TRPML2 knockout mice show severely reduced production of the chemokine CCL2 and impaired recruitment of peripheral macrophages in response to LPS or live bacteria, establishing a direct role for TRPML2 in the innate immune response.","method":"Immunofluorescence of endogenous protein, TRPML2 knockout mouse generation, cytokine/chemokine measurements, in vivo macrophage recruitment assay (i.p. LPS/bacteria), quantitative RT-PCR","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean knockout mouse with defined in vivo phenotype, endogenous protein localization, multiple orthogonal readouts","pmids":["26432893"],"is_preprint":false},{"year":2018,"finding":"The first isoform-selective TRPML2 agonist, ML2-SA1, directly stimulates release of the chemokine CCL2 from macrophages and stimulates macrophage migration, mimicking CCL2 function. Endolysosomal patch-clamp experiments demonstrate that endogenous TRPML2 is expressed in early/recycling endosomes. ML2-SA1 promotes trafficking through early/recycling endosomes, establishing a direct link between TRPML2 activation and CCL2 secretion via this pathway.","method":"Endolysosomal patch-clamp electrophysiology, pharmacological activation with selective agonist ML2-SA1, chemokine ELISA, macrophage migration assay, fluorescence trafficking assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct electrophysiology of endogenous channel, selective agonist, multiple functional readouts, replicated findings consistent with prior KO study","pmids":["30479274"],"is_preprint":false},{"year":2019,"finding":"Crystal structures of the tetrameric human TRPML2 extracytosolic/lumenal domain (ELD) at pH 6.5 (2.0 Å) and pH 4.5 (2.95 Å) reveal a large domain between TM helices S1 and S2. Isothermal titration calorimetry shows Ca2+ binds to the highly acidic central pre-pore loop of the ELD, and this binding is abrogated at low pH, consistent with pH-dependent channel regulation. Native mass spectrometry shows that changes in pH or Ca2+ can influence ELD oligomer integrity without altering secondary structure.","method":"X-ray crystallography, isothermal titration calorimetry (ITC), small angle X-ray scattering (SAXS), native mass spectrometry","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure at two pH values, Ca2+ binding confirmed by ITC, solution behavior by SAXS and native MS, multiple orthogonal methods","pmids":["31178222"],"is_preprint":false},{"year":2020,"finding":"TRPML2 is a hypotonicity/mechanosensitive cation channel in endolysosomal membranes. The phosphoinositide binding pocket is required for hypotonicity-sensitivity: substitution of L314R completely abrogates hypotonicity-sensitivity. The hypotonicity-insensitive L314R mutant slows the fast recycling pathway in immune cells, establishing that TRPML2 hypotonicity-sensitivity is functionally required for fast endolysosomal recycling.","method":"Endolysosomal patch-clamp electrophysiology, site-directed mutagenesis (L314R), hypotonic stimulation assays, fluorescence-based recycling assays in immune cells","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct electrophysiology with mutagenesis plus functional recycling assay, single lab with multiple orthogonal approaches","pmids":["33177082"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structure of full-length mouse TRPML2 in lipid nanodiscs at 3.14 Å reveals a homotetrameric architecture in an inactive (apo) conformation at pH 7.4, with unique features of the extracytosolic/lumenal domain and voltage sensor-like domain that have implications for the ion-conducting pathway, enabling structural comparisons with TRPML1 and TRPML3.","method":"Cryo-electron microscopy, lipid nanodisc reconstitution","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — near-atomic resolution cryo-EM structure of full-length channel in native-like lipid environment, single study","pmids":["34915027"],"is_preprint":false},{"year":2021,"finding":"MCOLN2/TRPML2 promotes prostate cancer cell proliferation, migration, and invasion, and in vivo xenograft tumor growth. Mechanistically, MCOLN2 promotes production and release of IL-1β, and MCOLN2 activates the NF-κB pathway as demonstrated by luciferase reporter assay and Western blot.","method":"MCOLN2 knockdown/overexpression, cytokine array, ELISA, Ca2+ release experiments, luciferase reporter assay (NF-κB), in vivo xenograft model","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays including luciferase reporter for pathway placement, in vivo data, single lab","pmids":["34548638"],"is_preprint":false},{"year":2023,"finding":"MCOLN2/TRPML2 conducts Mg2+ currents out of endolysosomes and restricts intracellular Salmonella Typhi replication through magnesium deprivation (nutritional immunity). Mg2+ currents through TRPML2 were directly measured by endolysosomal patch-clamping, and manipulation of magnesium availability confirmed the mechanism.","method":"Cellular genome-wide association study (cGWAS), endolysosomal patch-clamp electrophysiology, intracellular S. Typhi transcriptomics, magnesium availability manipulation, genetic knockdown/overexpression","journal":"Cell genomics","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct electrophysiological measurement of Mg2+ currents, cGWAS plus transcriptomics plus direct ion manipulation, multiple orthogonal approaches","pmids":["37228749"],"is_preprint":false},{"year":2022,"finding":"In glioblastoma cells, TRPML2 silencing inhibits expression of the VEGFA/Notch2 angiogenic pathway, while enforced TRPML2 expression or ML2-SA1 agonist stimulation increases VEGFA release and Notch2 activation. TRPML2 silencing also leads to increased invasion capability and altered EMT markers (vimentin, CD44). Cathepsin B-dependent and -independent pRB proteasomal degradation is altered by TRPML2 silencing.","method":"siRNA silencing, TRPML2 overexpression, ML2-SA1 agonist treatment, ddPCR, Western blot, invasion assay, VEGFA ELISA","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA plus OE plus selective agonist with multiple pathway readouts, single lab","pmids":["35054871"],"is_preprint":false},{"year":2022,"finding":"TRPML1 and TRPML2 partially colocalize in ER and lysosomal compartments in glioblastoma cell lines. Silencing of either TRPML1 or TRPML2 reduces the protein level of the other channel, and double knockdown of both channels leads to increased GBM cell survival and improved migration/invasion ability compared to single-channel silencing.","method":"Confocal colocalization, RNA interference (single and double knockdown), RT-PCR, FACS, Western blot, cell viability and invasion assays","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — confocal colocalization plus functional double-KD epistasis, single lab, multiple readouts","pmids":["35887088"],"is_preprint":false},{"year":2026,"finding":"Obinutuzumab (anti-CD20 antibody) internalizes into acidic compartments where it colocalizes with sphingomyelin (SM). SM-dependent inhibition of TRPML2-mediated lysosomal Ca2+ release sensitizes lysosomes to obinutuzumab-induced stress and lysosomal membrane permeabilization (LMP). Restoration of TRPML2 function by SMase treatment or blockade of OBI internalization attenuates LMP, establishing a SM-TRPML2 axis in lysosomal Ca2+ regulation.","method":"Imaging (colocalization), genetic approaches (TRPML2 manipulation), biochemical assays (sphingomyelinase treatment), Ca2+ release measurements, LMP assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal approaches (imaging, genetics, biochemistry, SMase rescue), single lab, mechanistic pathway established","pmids":["41634107"],"is_preprint":false},{"year":2026,"finding":"Two scorpion venom peptides, BmP05 and BmKK12, were identified as TRPML2 agonists by co-immunoprecipitation/LC-MS/MS screening. Calcium imaging confirmed they induce Ca2+ influx via TRPML2 activation. Both peptides inhibited Zika virus replication at non-cytotoxic concentrations in a concentration-dependent manner, while weaker TRPML2 activators (MMTX, BmTX1) did not inhibit ZIKV.","method":"Co-immunoprecipitation combined with LC-MS/MS, molecular docking, calcium imaging, antiviral replication assay, chemical synthesis and characterization of peptides","journal":"Toxins","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP/MS binding identification plus functional Ca2+ imaging, antiviral correlation with agonist potency, single study","pmids":["41745776"],"is_preprint":false}],"current_model":"TRPML2 (MCOLN2) is an inwardly rectifying, nonselective cation channel (permeable to Ca2+, Na+, Fe2+, Mg2+) that resides primarily in recycling endosomes of immune cells, where it is activated by hypotonicity/membrane tension (requiring its phosphoinositide-binding pocket), PI(3,5)P2, low extracellular sodium, and selective agonists; it forms homo- and heteromultimers with TRPML1/3 (with TRPML2 dominating lysosomal targeting of TRPML3), is transcriptionally driven by PAX5 in B-cells and upregulated by TLR signaling, and functions mechanistically to accelerate cargo recycling through early/recycling endosomes—directly promoting CCL2 chemokine secretion and macrophage migration in innate immunity—while also conducting Mg2+ out of endolysosomes to restrict intracellular bacterial replication, and activating downstream IL-1β/NF-κB and VEGFA/Notch2 signaling in cancer contexts."},"narrative":{"mechanistic_narrative":"MCOLN2 encodes TRPML2, an inwardly rectifying, nonselective cation channel permeable to Ca2+ that operates in the endolysosomal system of immune cells to control cargo recycling and innate immune signaling [PMID:19940139, PMID:26432893, PMID:30479274]. The channel is constitutively active at the plasma membrane and conducts Ca2+, with constitutive activity sufficient to cause Ca2+-overload cell death, and a varitint-waddler (Ala→Pro) substitution in TM5 produces a gain-of-function channel [PMID:19940139]; gating is tuned by extracytosolic pH, low extracellular sodium, and selective small-molecule agonists shared with TRPML3 [PMID:19940139, PMID:22753890]. Structural work defines a homotetramer whose large extracytosolic/lumenal domain binds Ca2+ at an acidic pre-pore loop in a pH-dependent manner, and full-length cryo-EM captures the inactive apo state and the ion-conducting pathway [PMID:31178222, PMID:34915027]. TRPML2 also behaves as a hypotonicity/mechanosensitive channel that requires an intact phosphoinositide-binding pocket (abolished by L314R), and this mechanosensitivity is functionally needed for fast endolysosomal recycling [PMID:33177082]. In macrophages the endogenous channel localizes to early/recycling endosomes, and its activation—genetically or by the selective agonist ML2-SA1—drives CCL2 chemokine secretion and macrophage migration, with TRPML2-knockout mice showing reduced CCL2 and impaired macrophage recruitment to LPS or bacteria [PMID:26432893, PMID:30479274]. Beyond Ca2+, TRPML2 conducts Mg2+ out of endolysosomes to restrict intracellular Salmonella Typhi replication through magnesium deprivation [PMID:37228749]. TRPML2 forms homo- and heteromultimers with TRPML1 and TRPML3 and dictates lysosomal targeting of TRPML3 [PMID:16606612], and MCOLN2 transcription is driven by PAX5 acting at a proximal promoter element [PMID:25445271]. In cancer contexts TRPML2 activates IL-1β/NF-κB signaling in prostate cancer and the VEGFA/Notch2 axis in glioblastoma [PMID:34548638, PMID:35054871].","teleology":[{"year":2006,"claim":"Established that TRPML2 assembles into homo- and heteromultimers and acts as a dominant determinant of subcellular targeting within the TRPML family, framing it as a lysosomal channel that organizes its paralogs.","evidence":"Reciprocal co-immunoprecipitation and coexpression microscopy with localization mutants across TRPML1/2/3 combinations","pmids":["16606612"],"confidence":"High","gaps":["Did not establish channel activity or physiological function","Localization assessed under overexpression, not endogenous conditions"]},{"year":2009,"claim":"Defined TRPML2 biophysically as a constitutively active, inwardly rectifying, nonselective Ca2+-permeable channel regulated by pH, answering whether MCOLN2 encodes a functional ion channel.","evidence":"Whole-cell patch-clamp electrophysiology with site-directed mutagenesis and viability assays in heterologous mammalian cells","pmids":["19940139"],"confidence":"High","gaps":["Recordings at the plasma membrane rather than the native endolysosomal compartment","Endogenous activators and physiological gating context not defined"]},{"year":2009,"claim":"Linked TRPML2 expression to TRPML1 activity, raising the possibility of cross-regulation within the channel family at the transcriptional level.","evidence":"RNAi knockdown with overexpression rescue and pharmacological TRPML1 activation, monitored by qRT-PCR","pmids":["19763610"],"confidence":"Medium","gaps":["Transcriptional mechanism linking TRPML1 activity to MCOLN2 expression unresolved","Single-lab, cell-type-restricted observation"]},{"year":2012,"claim":"Identified low extracellular sodium and TRPML3-class small molecules as activators, indicating shared gating determinants and providing pharmacological tools.","evidence":"Whole-cell patch-clamp with a small-molecule screen and mutagenesis of extracellular loop residues","pmids":["22753890"],"confidence":"Medium","gaps":["Sodium-block residue mapping done on TRPML3, not directly on TRPML2","Physiological relevance of sodium sensitivity not established"]},{"year":2014,"claim":"Identified PAX5 as the transcriptional activator of MCOLN2, explaining its restricted/immune-cell expression pattern at the promoter level.","evidence":"Luciferase reporter assays, PAX5 overexpression and RNAi, and promoter site-directed mutagenesis","pmids":["25445271"],"confidence":"Medium","gaps":["Direct PAX5 occupancy at the endogenous promoter (e.g. ChIP) not shown","Whether PAX5 fully accounts for tissue specificity unaddressed"]},{"year":2015,"claim":"Placed TRPML2 in recycling endosomes of macrophages and tied it to innate immunity via CCL2 production and macrophage recruitment, defining its first in vivo function.","evidence":"Endogenous immunofluorescence, TRPML2-knockout mice, chemokine measurements, and in vivo macrophage recruitment assays","pmids":["26432893"],"confidence":"High","gaps":["Mechanistic link from channel activity to CCL2 secretion not yet resolved","Ion-flux dependence of the phenotype not directly tested"]},{"year":2018,"claim":"Connected TRPML2 channel activity directly to CCL2 secretion and migration using an isoform-selective agonist, demonstrating that activation accelerates early/recycling endosomal trafficking.","evidence":"Endolysosomal patch-clamp of endogenous channel, ML2-SA1 agonist, chemokine ELISA, migration and fluorescence trafficking assays","pmids":["30479274"],"confidence":"High","gaps":["Cargo identity and the recycling step coupling Ca2+ flux to CCL2 export not defined","Whether Ca2+ versus other ions drives the effect not separated"]},{"year":2019,"claim":"Provided a structural basis for pH-dependent regulation by resolving the extracytosolic/lumenal domain and its acidic Ca2+-binding pre-pore loop.","evidence":"X-ray crystallography at two pH values with ITC, SAXS, and native mass spectrometry","pmids":["31178222"],"confidence":"High","gaps":["Isolated lumenal domain, not the full-length channel in membrane","Gating transitions coupled to Ca2+/pH binding not visualized"]},{"year":2020,"claim":"Identified TRPML2 as a hypotonicity/mechanosensitive channel whose phosphoinositide-binding pocket is required for fast endolysosomal recycling, linking a gating stimulus to a cellular output.","evidence":"Endolysosomal patch-clamp, L314R mutagenesis, hypotonic stimulation, and recycling assays in immune cells","pmids":["33177082"],"confidence":"High","gaps":["How membrane tension is sensed structurally remains undefined","Physiological source of the hypotonic/tension stimulus in vivo unclear"]},{"year":2021,"claim":"Resolved the full-length homotetrameric channel in lipid nanodiscs, defining the apo conformation and ion-conducting pathway and enabling family-wide structural comparison.","evidence":"Cryo-EM of full-length mouse TRPML2 reconstituted in lipid nanodiscs","pmids":["34915027"],"confidence":"High","gaps":["Captured only the inactive apo state; activated/agonist-bound states not solved","Mechanosensory and PIP2-engaged conformations not visualized"]},{"year":2023,"claim":"Demonstrated that TRPML2 conducts Mg2+ out of endolysosomes to restrict intracellular Salmonella replication, extending its ion repertoire and role to nutritional immunity.","evidence":"cGWAS, endolysosomal patch-clamp measurement of Mg2+ currents, bacterial transcriptomics, and magnesium availability manipulation","pmids":["37228749"],"confidence":"High","gaps":["Relationship between Mg2+ conduction and the established Ca2+/recycling functions unresolved","Selectivity mechanism for Mg2+ not structurally defined"]},{"year":2021,"claim":"Implicated TRPML2 in tumor growth via IL-1β production and NF-κB activation, extending its signaling role beyond normal immunity.","evidence":"MCOLN2 knockdown/overexpression, cytokine array/ELISA, Ca2+ release, NF-κB luciferase reporter, and xenograft model","pmids":["34548638"],"confidence":"Medium","gaps":["Direct mechanistic chain from channel flux to NF-κB not dissected","Single-lab, single-cancer-type evidence"]},{"year":2022,"claim":"Tied TRPML2 to VEGFA/Notch2 angiogenic signaling and EMT regulation in glioblastoma, and showed functional interdependence with TRPML1.","evidence":"siRNA single/double knockdown with epistasis, overexpression, ML2-SA1, confocal colocalization, ELISA, and invasion assays","pmids":["35054871","35887088"],"confidence":"Medium","gaps":["Direction of channel-to-pathway causality not fully established","Mutual stabilization mechanism of TRPML1/2 protein levels unknown"]},{"year":2026,"claim":"Defined a sphingomyelin–TRPML2 axis controlling lysosomal Ca2+ release and membrane integrity, relevant to anti-CD20 antibody-induced lysosomal stress.","evidence":"Colocalization imaging, genetic TRPML2 manipulation, sphingomyelinase rescue, Ca2+ release and LMP assays","pmids":["41634107"],"confidence":"Medium","gaps":["Whether sphingomyelin acts directly on the channel or via membrane environment unresolved","Single-study, antibody-specific context"]},{"year":2026,"claim":"Identified scorpion venom peptides as TRPML2 agonists whose potency correlates with antiviral activity against Zika virus, expanding the agonist toolkit and an antiviral link.","evidence":"Co-IP/LC-MS/MS binding screen, molecular docking, calcium imaging, and antiviral replication assays","pmids":["41745776"],"confidence":"Medium","gaps":["Mechanism connecting TRPML2 Ca2+ flux to ZIKV restriction not established","Direct binding site and selectivity over other TRPMLs not defined"]},{"year":null,"claim":"How distinct gating stimuli (pH, mechanical tension, PIP2, sodium, agonists) and distinct conducted ions (Ca2+ versus Mg2+) are integrated to produce specific cargo-recycling and immune outputs remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No activated-state structure linking gating stimuli to pore opening","Cargo/effector machinery coupling channel flux to CCL2 secretion not identified","Functional separation of Ca2+- versus Mg2+-dependent roles not achieved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[1,8,11]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[8,7]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[0]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[5,6]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,3]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,6,11]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[6,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,12]}],"complexes":[],"partners":["MCOLN1","MCOLN3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IZK6","full_name":"Mucolipin-2","aliases":["Transient receptor potential channel mucolipin 2","TRPML2"],"length_aa":566,"mass_kda":65.9,"function":"Nonselective cation channel probably playing a role in the regulation of membrane trafficking events. Acts as a Ca(2+)-permeable cation channel with inwardly rectifying activity (PubMed:19885840, PubMed:19940139). May activate ARF6 and be involved in the trafficking of GPI-anchored cargo proteins to the cell surface via the ARF6-regulated recycling pathway (PubMed:17662026). May play a role in immune processes. In adaptive immunity, TRPML2 and TRPML1 may play redundant roles in the function of the specialized lysosomes of B cells (By similarity). In the innate immune response, may play a role in the regulation of chemokine secretion and macrophage migration (By similarity). Through a possible and probably tissue-specific heteromerization with MCOLN1 may be at least in part involved in many lysosome-dependent cellular events (PubMed:19885840). Also functions as a Fe(2+) permeable channel (By similarity)","subcellular_location":"Cell membrane; Late endosome membrane; Lysosome membrane; Recycling endosome membrane","url":"https://www.uniprot.org/uniprotkb/Q8IZK6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MCOLN2","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MCOLN1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MCOLN2","total_profiled":1310},"omim":[{"mim_id":"607400","title":"MUCOLIPIN 3; MCOLN3","url":"https://www.omim.org/entry/607400"},{"mim_id":"607399","title":"MUCOLIPIN 2; MCOLN2","url":"https://www.omim.org/entry/607399"},{"mim_id":"605248","title":"MUCOLIPIN 1; MCOLN1","url":"https://www.omim.org/entry/605248"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"adrenal gland","ntpm":8.5},{"tissue":"intestine","ntpm":14.1},{"tissue":"lymphoid tissue","ntpm":12.3}],"url":"https://www.proteinatlas.org/search/MCOLN2"},"hgnc":{"alias_symbol":["TRPML2","FLJ36691","TRP-ML2"],"prev_symbol":[]},"alphafold":{"accession":"Q8IZK6","domains":[{"cath_id":"-","chopping":"118-280","consensus_level":"high","plddt":84.7212,"start":118,"end":280},{"cath_id":"1.20.120","chopping":"65-84_285-400","consensus_level":"high","plddt":89.3707,"start":65,"end":400},{"cath_id":"1.10.287","chopping":"407-520","consensus_level":"high","plddt":92.808,"start":407,"end":520}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IZK6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IZK6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IZK6-F1-predicted_aligned_error_v6.png","plddt_mean":82.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MCOLN2","jax_strain_url":"https://www.jax.org/strain/search?query=MCOLN2"},"sequence":{"accession":"Q8IZK6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IZK6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IZK6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IZK6"}},"corpus_meta":[{"pmid":"16606612","id":"PMC_16606612","title":"Lysosomal localization of TRPML3 depends on TRPML2 and the mucolipidosis-associated protein TRPML1.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16606612","citation_count":123,"is_preprint":false},{"pmid":"30479274","id":"PMC_30479274","title":"Selective agonist of TRPML2 reveals direct role in chemokine release from innate immune cells.","date":"2018","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/30479274","citation_count":88,"is_preprint":false},{"pmid":"26432893","id":"PMC_26432893","title":"Novel Role of TRPML2 in the Regulation of the Innate Immune Response.","date":"2015","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/26432893","citation_count":80,"is_preprint":false},{"pmid":"19763610","id":"PMC_19763610","title":"The tissue-specific expression of TRPML2 (MCOLN-2) gene is influenced by the presence of TRPML1.","date":"2009","source":"Pflugers Archiv : European journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/19763610","citation_count":61,"is_preprint":false},{"pmid":"33177082","id":"PMC_33177082","title":"TRPML2 is an osmo/mechanosensitive cation channel in endolysosomal organelles.","date":"2020","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/33177082","citation_count":51,"is_preprint":false},{"pmid":"26336837","id":"PMC_26336837","title":"The mucolipin-2 (TRPML2) ion channel: a tissue-specific protein crucial to normal cell function.","date":"2015","source":"Pflugers Archiv : European journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/26336837","citation_count":45,"is_preprint":false},{"pmid":"19940139","id":"PMC_19940139","title":"Constitutive activity of the human TRPML2 channel induces cell degeneration.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19940139","citation_count":41,"is_preprint":false},{"pmid":"16137664","id":"PMC_16137664","title":"Differential expression and molecular characterisation of Lmo7, Myo1e, Sash1, and Mcoln2 genes in Btk-defective B-cells.","date":"2005","source":"Cellular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/16137664","citation_count":36,"is_preprint":false},{"pmid":"22753890","id":"PMC_22753890","title":"Constitutive activity of TRPML2 and TRPML3 channels versus activation by low extracellular sodium and small molecules.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22753890","citation_count":28,"is_preprint":false},{"pmid":"24756724","id":"PMC_24756724","title":"TRPML2 and mucolipin evolution.","date":"2014","source":"Handbook of experimental 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Treatment.","date":"2022","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/35053255","citation_count":7,"is_preprint":false},{"pmid":"35054871","id":"PMC_35054871","title":"Functional In Vitro Assessment of VEGFA/NOTCH2 Signaling Pathway and pRB Proteasomal Degradation and the Clinical Relevance of Mucolipin TRPML2 Overexpression in Glioblastoma Patients.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35054871","citation_count":7,"is_preprint":false},{"pmid":"35887088","id":"PMC_35887088","title":"Coexpression of TRPML1 and TRPML2 Mucolipin Channels Affects the Survival of Glioblastoma Patients.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35887088","citation_count":6,"is_preprint":false},{"pmid":"38901736","id":"PMC_38901736","title":"Zika virus replication is impaired by a selective agonist of the TRPML2 ion channel.","date":"2024","source":"Antiviral research","url":"https://pubmed.ncbi.nlm.nih.gov/38901736","citation_count":6,"is_preprint":false},{"pmid":"38306561","id":"PMC_38306561","title":"Role of PAX6, TRPA1, BCL11B, MCOLN2, CUX1, EMX1 in colorectal cancer and osteosarcoma.","date":"2024","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38306561","citation_count":4,"is_preprint":false},{"pmid":"41634107","id":"PMC_41634107","title":"Obinutuzumab induces lysosomal destabilization via sphingomyelin-dependent inhibition of TRPML2.","date":"2026","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/41634107","citation_count":0,"is_preprint":false},{"pmid":"41745776","id":"PMC_41745776","title":"Discovery of Two Novel Scorpion Venom Peptides Activating TRPML2 to Impair ZIKV Internalization.","date":"2026","source":"Toxins","url":"https://pubmed.ncbi.nlm.nih.gov/41745776","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":14206,"output_tokens":4581,"usd":0.055667,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12552,"output_tokens":4792,"usd":0.09128,"stage2_stop_reason":"end_turn"},"total_usd":0.146947,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"TRPML2 homomultimers localize to lysosomes, and TRPML2 can form homo- and heteromultimers with TRPML1 and TRPML3. When coexpressed, TRPML2 dictates lysosomal localization of TRPML3 (which otherwise resides in the ER), but TRPML3 does not cause retention of TRPML2 in the ER, establishing a hierarchy of subcellular localization control.\",\n      \"method\": \"Co-immunoprecipitation (homo/heteromultimer formation), fluorescence microscopy of coexpressed proteins, lysosomal targeting mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP for multimerization, systematic coexpression with localization mutants, replicated across multiple TRPML combinations\",\n      \"pmids\": [\"16606612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Wild-type human TRPML2 is a constitutively active, inwardly rectifying, nonselective cation channel permeable to Ca2+ at the plasma membrane, inhibited by low extracytosolic pH but not regulated by Ca2+. Constitutive activity causes cell death by Ca2+ overload. The varitint-waddler (Va) gain-of-function mutation (Ala→Pro in TM5) renders TRPML2lv constitutively active.\",\n      \"method\": \"Electrophysiology (whole-cell patch-clamp), site-directed mutagenesis, cell viability assays, heterologous expression in mammalian cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro electrophysiology with mutagenesis, multiple channel properties measured, single lab with orthogonal readouts\",\n      \"pmids\": [\"19940139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TRPML1 plays a role in the tissue-specific transcriptional regulation of TRPML2: knockdown of endogenous TRPML1 in HEK-293 cells reduces human TRPML2 transcript levels, which are restored by TRPML1 overexpression; conversely, TRPML1 activators (NAADP, H-89) upregulate TRPML2sv transcripts in primary mouse lymphoid cells.\",\n      \"method\": \"RNA interference, quantitative RT-PCR, pharmacological activation of TRPML1, overexpression rescue\",\n      \"journal\": \"Pflugers Archiv : European journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi plus rescue plus pharmacological activation, single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"19763610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TRPML2 is activated by lowering extracellular sodium concentration and by a subset of small chemical compounds (sulfonamide-related) previously identified as TRPML3 activators, confirming functional activity at the plasma membrane and suggesting shared gating mechanisms with TRPML3. Mutagenesis of Glu-361 in the second extracellular loop of TRPML3 significantly impacts sodium-mediated block, pointing to negatively charged extracellular loop residues as determinants of sodium inhibition.\",\n      \"method\": \"Electrophysiology (whole-cell patch-clamp), site-directed mutagenesis, pharmacological screen with small molecules\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro electrophysiology with mutagenesis for TRPML3 gating mechanism; TRPML2 activation confirmed pharmacologically in same study, single lab\",\n      \"pmids\": [\"22753890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PAX5 (BSAP) is the transcriptional activator of the MCOLN2 gene. Heterologous PAX5 expression in HEK-293 cells significantly increases endogenous MCOLN2 transcript and TRPML2 protein levels; PAX5 RNAi reduces this effect. Site-directed mutagenesis identified the core promoter and PAX5 binding region between −79 and −60 bp upstream of the transcriptional start site.\",\n      \"method\": \"Dual-luciferase reporter assay, PAX5 overexpression, RNA interference, site-directed mutagenesis of promoter, RT-PCR and Western blot\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter mutagenesis plus OE plus RNAi rescue, single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"25445271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Endogenous TRPML2 localizes primarily to recycling endosomes in macrophages (distinct from TRPML1 in late endosomes and TRPML3 in early endosomes). TRPML2 knockout mice show severely reduced production of the chemokine CCL2 and impaired recruitment of peripheral macrophages in response to LPS or live bacteria, establishing a direct role for TRPML2 in the innate immune response.\",\n      \"method\": \"Immunofluorescence of endogenous protein, TRPML2 knockout mouse generation, cytokine/chemokine measurements, in vivo macrophage recruitment assay (i.p. LPS/bacteria), quantitative RT-PCR\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean knockout mouse with defined in vivo phenotype, endogenous protein localization, multiple orthogonal readouts\",\n      \"pmids\": [\"26432893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The first isoform-selective TRPML2 agonist, ML2-SA1, directly stimulates release of the chemokine CCL2 from macrophages and stimulates macrophage migration, mimicking CCL2 function. Endolysosomal patch-clamp experiments demonstrate that endogenous TRPML2 is expressed in early/recycling endosomes. ML2-SA1 promotes trafficking through early/recycling endosomes, establishing a direct link between TRPML2 activation and CCL2 secretion via this pathway.\",\n      \"method\": \"Endolysosomal patch-clamp electrophysiology, pharmacological activation with selective agonist ML2-SA1, chemokine ELISA, macrophage migration assay, fluorescence trafficking assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct electrophysiology of endogenous channel, selective agonist, multiple functional readouts, replicated findings consistent with prior KO study\",\n      \"pmids\": [\"30479274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Crystal structures of the tetrameric human TRPML2 extracytosolic/lumenal domain (ELD) at pH 6.5 (2.0 Å) and pH 4.5 (2.95 Å) reveal a large domain between TM helices S1 and S2. Isothermal titration calorimetry shows Ca2+ binds to the highly acidic central pre-pore loop of the ELD, and this binding is abrogated at low pH, consistent with pH-dependent channel regulation. Native mass spectrometry shows that changes in pH or Ca2+ can influence ELD oligomer integrity without altering secondary structure.\",\n      \"method\": \"X-ray crystallography, isothermal titration calorimetry (ITC), small angle X-ray scattering (SAXS), native mass spectrometry\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure at two pH values, Ca2+ binding confirmed by ITC, solution behavior by SAXS and native MS, multiple orthogonal methods\",\n      \"pmids\": [\"31178222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TRPML2 is a hypotonicity/mechanosensitive cation channel in endolysosomal membranes. The phosphoinositide binding pocket is required for hypotonicity-sensitivity: substitution of L314R completely abrogates hypotonicity-sensitivity. The hypotonicity-insensitive L314R mutant slows the fast recycling pathway in immune cells, establishing that TRPML2 hypotonicity-sensitivity is functionally required for fast endolysosomal recycling.\",\n      \"method\": \"Endolysosomal patch-clamp electrophysiology, site-directed mutagenesis (L314R), hypotonic stimulation assays, fluorescence-based recycling assays in immune cells\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct electrophysiology with mutagenesis plus functional recycling assay, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"33177082\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structure of full-length mouse TRPML2 in lipid nanodiscs at 3.14 Å reveals a homotetrameric architecture in an inactive (apo) conformation at pH 7.4, with unique features of the extracytosolic/lumenal domain and voltage sensor-like domain that have implications for the ion-conducting pathway, enabling structural comparisons with TRPML1 and TRPML3.\",\n      \"method\": \"Cryo-electron microscopy, lipid nanodisc reconstitution\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — near-atomic resolution cryo-EM structure of full-length channel in native-like lipid environment, single study\",\n      \"pmids\": [\"34915027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MCOLN2/TRPML2 promotes prostate cancer cell proliferation, migration, and invasion, and in vivo xenograft tumor growth. Mechanistically, MCOLN2 promotes production and release of IL-1β, and MCOLN2 activates the NF-κB pathway as demonstrated by luciferase reporter assay and Western blot.\",\n      \"method\": \"MCOLN2 knockdown/overexpression, cytokine array, ELISA, Ca2+ release experiments, luciferase reporter assay (NF-κB), in vivo xenograft model\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays including luciferase reporter for pathway placement, in vivo data, single lab\",\n      \"pmids\": [\"34548638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MCOLN2/TRPML2 conducts Mg2+ currents out of endolysosomes and restricts intracellular Salmonella Typhi replication through magnesium deprivation (nutritional immunity). Mg2+ currents through TRPML2 were directly measured by endolysosomal patch-clamping, and manipulation of magnesium availability confirmed the mechanism.\",\n      \"method\": \"Cellular genome-wide association study (cGWAS), endolysosomal patch-clamp electrophysiology, intracellular S. Typhi transcriptomics, magnesium availability manipulation, genetic knockdown/overexpression\",\n      \"journal\": \"Cell genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct electrophysiological measurement of Mg2+ currents, cGWAS plus transcriptomics plus direct ion manipulation, multiple orthogonal approaches\",\n      \"pmids\": [\"37228749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In glioblastoma cells, TRPML2 silencing inhibits expression of the VEGFA/Notch2 angiogenic pathway, while enforced TRPML2 expression or ML2-SA1 agonist stimulation increases VEGFA release and Notch2 activation. TRPML2 silencing also leads to increased invasion capability and altered EMT markers (vimentin, CD44). Cathepsin B-dependent and -independent pRB proteasomal degradation is altered by TRPML2 silencing.\",\n      \"method\": \"siRNA silencing, TRPML2 overexpression, ML2-SA1 agonist treatment, ddPCR, Western blot, invasion assay, VEGFA ELISA\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA plus OE plus selective agonist with multiple pathway readouts, single lab\",\n      \"pmids\": [\"35054871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TRPML1 and TRPML2 partially colocalize in ER and lysosomal compartments in glioblastoma cell lines. Silencing of either TRPML1 or TRPML2 reduces the protein level of the other channel, and double knockdown of both channels leads to increased GBM cell survival and improved migration/invasion ability compared to single-channel silencing.\",\n      \"method\": \"Confocal colocalization, RNA interference (single and double knockdown), RT-PCR, FACS, Western blot, cell viability and invasion assays\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — confocal colocalization plus functional double-KD epistasis, single lab, multiple readouts\",\n      \"pmids\": [\"35887088\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Obinutuzumab (anti-CD20 antibody) internalizes into acidic compartments where it colocalizes with sphingomyelin (SM). SM-dependent inhibition of TRPML2-mediated lysosomal Ca2+ release sensitizes lysosomes to obinutuzumab-induced stress and lysosomal membrane permeabilization (LMP). Restoration of TRPML2 function by SMase treatment or blockade of OBI internalization attenuates LMP, establishing a SM-TRPML2 axis in lysosomal Ca2+ regulation.\",\n      \"method\": \"Imaging (colocalization), genetic approaches (TRPML2 manipulation), biochemical assays (sphingomyelinase treatment), Ca2+ release measurements, LMP assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal approaches (imaging, genetics, biochemistry, SMase rescue), single lab, mechanistic pathway established\",\n      \"pmids\": [\"41634107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Two scorpion venom peptides, BmP05 and BmKK12, were identified as TRPML2 agonists by co-immunoprecipitation/LC-MS/MS screening. Calcium imaging confirmed they induce Ca2+ influx via TRPML2 activation. Both peptides inhibited Zika virus replication at non-cytotoxic concentrations in a concentration-dependent manner, while weaker TRPML2 activators (MMTX, BmTX1) did not inhibit ZIKV.\",\n      \"method\": \"Co-immunoprecipitation combined with LC-MS/MS, molecular docking, calcium imaging, antiviral replication assay, chemical synthesis and characterization of peptides\",\n      \"journal\": \"Toxins\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP/MS binding identification plus functional Ca2+ imaging, antiviral correlation with agonist potency, single study\",\n      \"pmids\": [\"41745776\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TRPML2 (MCOLN2) is an inwardly rectifying, nonselective cation channel (permeable to Ca2+, Na+, Fe2+, Mg2+) that resides primarily in recycling endosomes of immune cells, where it is activated by hypotonicity/membrane tension (requiring its phosphoinositide-binding pocket), PI(3,5)P2, low extracellular sodium, and selective agonists; it forms homo- and heteromultimers with TRPML1/3 (with TRPML2 dominating lysosomal targeting of TRPML3), is transcriptionally driven by PAX5 in B-cells and upregulated by TLR signaling, and functions mechanistically to accelerate cargo recycling through early/recycling endosomes—directly promoting CCL2 chemokine secretion and macrophage migration in innate immunity—while also conducting Mg2+ out of endolysosomes to restrict intracellular bacterial replication, and activating downstream IL-1β/NF-κB and VEGFA/Notch2 signaling in cancer contexts.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MCOLN2 encodes TRPML2, an inwardly rectifying, nonselective cation channel permeable to Ca2+ that operates in the endolysosomal system of immune cells to control cargo recycling and innate immune signaling [#1, #5, #6]. The channel is constitutively active at the plasma membrane and conducts Ca2+, with constitutive activity sufficient to cause Ca2+-overload cell death, and a varitint-waddler (Ala\\u2192Pro) substitution in TM5 produces a gain-of-function channel [#1]; gating is tuned by extracytosolic pH, low extracellular sodium, and selective small-molecule agonists shared with TRPML3 [#1, #3]. Structural work defines a homotetramer whose large extracytosolic/lumenal domain binds Ca2+ at an acidic pre-pore loop in a pH-dependent manner, and full-length cryo-EM captures the inactive apo state and the ion-conducting pathway [#7, #9]. TRPML2 also behaves as a hypotonicity/mechanosensitive channel that requires an intact phosphoinositide-binding pocket (abolished by L314R), and this mechanosensitivity is functionally needed for fast endolysosomal recycling [#8]. In macrophages the endogenous channel localizes to early/recycling endosomes, and its activation\\u2014genetically or by the selective agonist ML2-SA1\\u2014drives CCL2 chemokine secretion and macrophage migration, with TRPML2-knockout mice showing reduced CCL2 and impaired macrophage recruitment to LPS or bacteria [#5, #6]. Beyond Ca2+, TRPML2 conducts Mg2+ out of endolysosomes to restrict intracellular Salmonella Typhi replication through magnesium deprivation [#11]. TRPML2 forms homo- and heteromultimers with TRPML1 and TRPML3 and dictates lysosomal targeting of TRPML3 [#0], and MCOLN2 transcription is driven by PAX5 acting at a proximal promoter element [#4]. In cancer contexts TRPML2 activates IL-1\\u03b2/NF-\\u03baB signaling in prostate cancer and the VEGFA/Notch2 axis in glioblastoma [#10, #12].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established that TRPML2 assembles into homo- and heteromultimers and acts as a dominant determinant of subcellular targeting within the TRPML family, framing it as a lysosomal channel that organizes its paralogs.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation and coexpression microscopy with localization mutants across TRPML1/2/3 combinations\",\n      \"pmids\": [\"16606612\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish channel activity or physiological function\", \"Localization assessed under overexpression, not endogenous conditions\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined TRPML2 biophysically as a constitutively active, inwardly rectifying, nonselective Ca2+-permeable channel regulated by pH, answering whether MCOLN2 encodes a functional ion channel.\",\n      \"evidence\": \"Whole-cell patch-clamp electrophysiology with site-directed mutagenesis and viability assays in heterologous mammalian cells\",\n      \"pmids\": [\"19940139\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Recordings at the plasma membrane rather than the native endolysosomal compartment\", \"Endogenous activators and physiological gating context not defined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linked TRPML2 expression to TRPML1 activity, raising the possibility of cross-regulation within the channel family at the transcriptional level.\",\n      \"evidence\": \"RNAi knockdown with overexpression rescue and pharmacological TRPML1 activation, monitored by qRT-PCR\",\n      \"pmids\": [\"19763610\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcriptional mechanism linking TRPML1 activity to MCOLN2 expression unresolved\", \"Single-lab, cell-type-restricted observation\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified low extracellular sodium and TRPML3-class small molecules as activators, indicating shared gating determinants and providing pharmacological tools.\",\n      \"evidence\": \"Whole-cell patch-clamp with a small-molecule screen and mutagenesis of extracellular loop residues\",\n      \"pmids\": [\"22753890\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Sodium-block residue mapping done on TRPML3, not directly on TRPML2\", \"Physiological relevance of sodium sensitivity not established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified PAX5 as the transcriptional activator of MCOLN2, explaining its restricted/immune-cell expression pattern at the promoter level.\",\n      \"evidence\": \"Luciferase reporter assays, PAX5 overexpression and RNAi, and promoter site-directed mutagenesis\",\n      \"pmids\": [\"25445271\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct PAX5 occupancy at the endogenous promoter (e.g. ChIP) not shown\", \"Whether PAX5 fully accounts for tissue specificity unaddressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Placed TRPML2 in recycling endosomes of macrophages and tied it to innate immunity via CCL2 production and macrophage recruitment, defining its first in vivo function.\",\n      \"evidence\": \"Endogenous immunofluorescence, TRPML2-knockout mice, chemokine measurements, and in vivo macrophage recruitment assays\",\n      \"pmids\": [\"26432893\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link from channel activity to CCL2 secretion not yet resolved\", \"Ion-flux dependence of the phenotype not directly tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected TRPML2 channel activity directly to CCL2 secretion and migration using an isoform-selective agonist, demonstrating that activation accelerates early/recycling endosomal trafficking.\",\n      \"evidence\": \"Endolysosomal patch-clamp of endogenous channel, ML2-SA1 agonist, chemokine ELISA, migration and fluorescence trafficking assays\",\n      \"pmids\": [\"30479274\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cargo identity and the recycling step coupling Ca2+ flux to CCL2 export not defined\", \"Whether Ca2+ versus other ions drives the effect not separated\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Provided a structural basis for pH-dependent regulation by resolving the extracytosolic/lumenal domain and its acidic Ca2+-binding pre-pore loop.\",\n      \"evidence\": \"X-ray crystallography at two pH values with ITC, SAXS, and native mass spectrometry\",\n      \"pmids\": [\"31178222\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Isolated lumenal domain, not the full-length channel in membrane\", \"Gating transitions coupled to Ca2+/pH binding not visualized\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified TRPML2 as a hypotonicity/mechanosensitive channel whose phosphoinositide-binding pocket is required for fast endolysosomal recycling, linking a gating stimulus to a cellular output.\",\n      \"evidence\": \"Endolysosomal patch-clamp, L314R mutagenesis, hypotonic stimulation, and recycling assays in immune cells\",\n      \"pmids\": [\"33177082\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How membrane tension is sensed structurally remains undefined\", \"Physiological source of the hypotonic/tension stimulus in vivo unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Resolved the full-length homotetrameric channel in lipid nanodiscs, defining the apo conformation and ion-conducting pathway and enabling family-wide structural comparison.\",\n      \"evidence\": \"Cryo-EM of full-length mouse TRPML2 reconstituted in lipid nanodiscs\",\n      \"pmids\": [\"34915027\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Captured only the inactive apo state; activated/agonist-bound states not solved\", \"Mechanosensory and PIP2-engaged conformations not visualized\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated that TRPML2 conducts Mg2+ out of endolysosomes to restrict intracellular Salmonella replication, extending its ion repertoire and role to nutritional immunity.\",\n      \"evidence\": \"cGWAS, endolysosomal patch-clamp measurement of Mg2+ currents, bacterial transcriptomics, and magnesium availability manipulation\",\n      \"pmids\": [\"37228749\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship between Mg2+ conduction and the established Ca2+/recycling functions unresolved\", \"Selectivity mechanism for Mg2+ not structurally defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Implicated TRPML2 in tumor growth via IL-1\\u03b2 production and NF-\\u03baB activation, extending its signaling role beyond normal immunity.\",\n      \"evidence\": \"MCOLN2 knockdown/overexpression, cytokine array/ELISA, Ca2+ release, NF-\\u03baB luciferase reporter, and xenograft model\",\n      \"pmids\": [\"34548638\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanistic chain from channel flux to NF-\\u03baB not dissected\", \"Single-lab, single-cancer-type evidence\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Tied TRPML2 to VEGFA/Notch2 angiogenic signaling and EMT regulation in glioblastoma, and showed functional interdependence with TRPML1.\",\n      \"evidence\": \"siRNA single/double knockdown with epistasis, overexpression, ML2-SA1, confocal colocalization, ELISA, and invasion assays\",\n      \"pmids\": [\"35054871\", \"35887088\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direction of channel-to-pathway causality not fully established\", \"Mutual stabilization mechanism of TRPML1/2 protein levels unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Defined a sphingomyelin\\u2013TRPML2 axis controlling lysosomal Ca2+ release and membrane integrity, relevant to anti-CD20 antibody-induced lysosomal stress.\",\n      \"evidence\": \"Colocalization imaging, genetic TRPML2 manipulation, sphingomyelinase rescue, Ca2+ release and LMP assays\",\n      \"pmids\": [\"41634107\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether sphingomyelin acts directly on the channel or via membrane environment unresolved\", \"Single-study, antibody-specific context\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified scorpion venom peptides as TRPML2 agonists whose potency correlates with antiviral activity against Zika virus, expanding the agonist toolkit and an antiviral link.\",\n      \"evidence\": \"Co-IP/LC-MS/MS binding screen, molecular docking, calcium imaging, and antiviral replication assays\",\n      \"pmids\": [\"41745776\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting TRPML2 Ca2+ flux to ZIKV restriction not established\", \"Direct binding site and selectivity over other TRPMLs not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How distinct gating stimuli (pH, mechanical tension, PIP2, sodium, agonists) and distinct conducted ions (Ca2+ versus Mg2+) are integrated to produce specific cargo-recycling and immune outputs remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No activated-state structure linking gating stimuli to pore opening\", \"Cargo/effector machinery coupling channel flux to CCL2 secretion not identified\", \"Functional separation of Ca2+- versus Mg2+-dependent roles not achieved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [1, 8, 11]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [8, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [5, 6]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 6, 11]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 12]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MCOLN1\", \"MCOLN3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}