{"gene":"LRRC26","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2010,"finding":"LRRC26 is an auxiliary protein of BK (BKα) channels that produces an unprecedented ~140 mV negative shift in voltage dependence, enabling BK channel activation at resting voltage without elevated cytosolic Ca²⁺. The mechanism involves enhanced allosteric coupling between voltage-sensor activation and the channel's closed-open transition.","method":"Electrophysiology (patch-clamp) in LNCaP prostate cancer cells and heterologous expression; functional characterization of BKα–LRRC26 complex","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — foundational electrophysiology with functional reconstitution, replicated across multiple subsequent studies","pmids":["20613726"],"is_preprint":false},{"year":2011,"finding":"LRRC26 selectively alters the pharmacology of BK channels: it strongly inhibits the ability of mallotoxin (MTX) to activate BK channels (reducing MTX-induced voltage shift from ~70 mV to ~6 mV) while having only a small effect on NS-1619 activation, indicating that the accessory protein differentially modulates activator efficacy.","method":"Electrophysiology in native parotid acinar cells and heterologous expression of parSlo ± LRRC26; pharmacological assays with MTX and NS-1619","journal":"Molecular pharmacology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct functional electrophysiology with pharmacological dissection in both native and heterologous systems, single lab","pmids":["21984254"],"is_preprint":false},{"year":2014,"finding":"In arterial smooth muscle cells, LRRC26 co-localizes with and co-immunoprecipitates with plasma membrane BKα subunits. LRRC26 knockdown reduces BK channel voltage sensitivity and apparent Ca²⁺ sensitivity, decreases transient BK current frequency and amplitude, and increases myogenic tone, establishing LRRC26 as a functional BK channel γ subunit in vascular smooth muscle.","method":"Co-immunoprecipitation, FRET microscopy, biotinylation (surface localization), RNAi knockdown, patch-clamp electrophysiology, myogenic tone measurements in cerebral artery myocytes","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, FRET, functional KD with defined electrophysiological and vascular phenotype; single lab but multiple orthogonal methods","pmids":["24906643"],"is_preprint":false},{"year":2017,"finding":"LRRC26 (γ1) co-assembles with BK α-subunits specifically in secretory epithelial cells (lacrimal gland, parotid gland, colon). In LRRC26 KO mice, BK channel gating in acinar cells shifts to resemble α-subunit-only channels (rightward voltage shift), and salivary [K⁺] is reduced, demonstrating LRRC26 is required for BK channel activation at physiological resting potentials to support secretory function.","method":"LRRC26 KO mice with β-gal reporter, co-immunoprecipitation in multiple tissues, patch-clamp in acinar cells, ion composition analysis of saliva","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined electrophysiological and physiological phenotype, co-IP in multiple native tissues, replicated across tissues","pmids":["28416688"],"is_preprint":false},{"year":2019,"finding":"In bronchial smooth muscle cells (BSMCs), LRRC26 (γ1) is highly expressed and interacts with BKα (shown by co-immunoprecipitation and TIRF imaging). BK channel steady-state activation in BSMCs occurs at more negative voltages (resembling BKα/γ1 reconstituted channels) compared to aortic SMCs or BKα-only channels. Mallotoxin (a BK activator selective for channels lacking γ1) activates BK currents in aortic SMCs but not in BSMCs, functionally confirming γ1 occupancy.","method":"Co-immunoprecipitation, total internal reflection fluorescence (TIRF) imaging, whole-cell patch-clamp electrophysiology, real-time PCR, Western blot in bronchial SMCs vs. aortic SMCs","journal":"American journal of physiology. Lung cellular and molecular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, TIRF, and pharmacological functional evidence; single lab","pmids":["31800260"],"is_preprint":false},{"year":2021,"finding":"LRRC26-associated BK channels are present and functionally active specifically in colonic goblet cells (GCs) at physiological conditions; in LRRC26 KO mice, BK channels are present in GCs but not activated under physiological conditions. LRRC26-associated BK channels underlie the resting transepithelial K⁺ current across distal colonic mucosa, and genetic ablation of LRRC26 (or BK α-subunit) dramatically increases susceptibility to DSS-induced colitis.","method":"LRRC26 KO mice, MUC2-fluorescent reporter mice, patch-clamp in isolated GCs, transepithelial current measurements, DSS colitis model","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with electrophysiological and disease phenotype, single-cell functional imaging, multiple orthogonal methods","pmids":["33431687"],"is_preprint":false},{"year":2018,"finding":"LRRC26 negatively regulates NF-κB signaling in triple-negative breast cancer cells. LRRC26 overexpression reduces TNF-α-mediated NF-κB luciferase reporter activity and downstream gene expression (IL-6, IL-8, CXCL1), while LRRC26 knockdown upregulates these NF-κB target genes. LRRC26 knockdown also enhances anchorage-independent growth, invasion, and migration. Loss of LRRC26 expression is associated with promoter methylation (restored by 5-aza-dC treatment).","method":"siRNA knockdown and ectopic overexpression, NF-κB luciferase reporter assay, anchorage-independent growth assay, invasion/migration assays, bisulfite pyrosequencing, 5-aza-dC treatment","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — reporter assay and loss/gain-of-function with multiple functional readouts; single lab","pmids":["29512727"],"is_preprint":false},{"year":2026,"finding":"Using macroscopic, single-channel, and gating-current measurements, LRRC26 (γ1) is shown to increase the equilibrium constant for BK channel closed-open transition by ~106-fold at zero mV by destabilizing the closed state and enhancing voltage-sensor–pore coupling, without affecting voltage-sensor activation per se. This clarifies a mechanistic controversy by identifying that γ1 primarily enhances the channel-opening reaction and energetic coupling, not voltage-sensor movement.","method":"Macroscopic patch-clamp, single-channel recordings, and gating-current measurements in heterologous expression of BKα ± LRRC26 (γ1)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — three orthogonal electrophysiological methods (macroscopic, single-channel, gating currents) directly measuring distinct aspects of gating; single lab","pmids":["41701845"],"is_preprint":false},{"year":2026,"finding":"Using concatenated BKα constructs (tandem dimers and tetramers), a single LRRC26 (γ1) subunit per BKα tetramer is sufficient to fully shift BK channel voltage activation (all-or-none stoichiometry), distinct from the stoichiometrically graded effect of a deep-pore L312A mutation and the all-four-subunit requirement for V288A selectivity filter inactivation.","method":"Concatenated tandem BKα subunit constructs with fused γ1, co-expression, electrophysiology (voltage-clamp) in heterologous expression system","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Moderate — engineered concatenated constructs with controlled stoichiometry plus mutagenesis and functional electrophysiology; single lab, multiple orthogonal approaches within study","pmids":["41784352"],"is_preprint":false}],"current_model":"LRRC26 (γ1) is an auxiliary subunit of large-conductance Ca²⁺- and voltage-activated BK (BKα) channels that produces a ~140 mV leftward shift in voltage-dependent activation by destabilizing the channel's closed state and enhancing voltage-sensor–pore coupling (without altering voltage-sensor movement itself); a single γ1 subunit per α-subunit tetramer is sufficient for full modulation, and this activity enables BK channel opening at physiological resting potentials and Ca²⁺ concentrations in secretory epithelial cells (lacrimal, salivary glands, goblet cells) and smooth muscle cells, supporting K⁺ secretion, transepithelial transport, vasodilation, and protection against colitis, while in cancer cells LRRC26 also suppresses NF-κB signaling to limit invasion and migration."},"narrative":{"mechanistic_narrative":"LRRC26 is the prototypical auxiliary γ1 subunit of large-conductance Ca²⁺- and voltage-activated BK (BKα) channels, conferring channel activation at physiological resting potentials without elevated cytosolic Ca²⁺ by producing a ~140 mV leftward shift in voltage-dependent activation [PMID:20613726]. Mechanistically, LRRC26 acts on the channel-opening reaction itself: it increases the closed-open equilibrium constant ~10⁶-fold at zero mV by destabilizing the closed state and enhancing voltage-sensor–pore coupling, without altering voltage-sensor movement per se [PMID:41701845], and a single γ1 subunit per BKα tetramer is sufficient for the full all-or-none gating shift [PMID:41784352]. This modulation also reshapes BK pharmacology, strongly suppressing mallotoxin efficacy [PMID:21984254]. Physiologically, LRRC26 co-assembles with surface BKα in secretory epithelia and smooth muscle, where its loss reverts gating toward α-only behavior: in vascular and bronchial smooth muscle it sets BK voltage and Ca²⁺ sensitivity and limits myogenic tone [PMID:24906643, PMID:31800260], and in secretory epithelial cells (lacrimal, parotid, colonic goblet cells) it is required for BK-dependent K⁺ secretion, transepithelial K⁺ transport, and protection against DSS-induced colitis [PMID:28416688, PMID:33431687]. Beyond its channel role, LRRC26 negatively regulates NF-κB signaling in triple-negative breast cancer cells, where its methylation-associated silencing de-represses inflammatory target genes and promotes invasion and migration [PMID:29512727].","teleology":[{"year":2010,"claim":"Established that LRRC26 is a BK channel auxiliary protein, answering how BK channels can open at resting voltage without high Ca²⁺ by enhancing allosteric voltage-sensor/gate coupling.","evidence":"Patch-clamp electrophysiology of BKα–LRRC26 complexes in LNCaP cells and heterologous expression","pmids":["20613726"],"confidence":"High","gaps":["Did not resolve whether the shift arises from altered voltage-sensor movement vs. the opening reaction","Subunit stoichiometry not defined"]},{"year":2011,"claim":"Showed LRRC26 reshapes BK pharmacology, distinguishing γ1-occupied from α-only channels through differential activator efficacy.","evidence":"Electrophysiology with mallotoxin and NS-1619 in native parotid acinar cells and heterologous parSlo ± LRRC26","pmids":["21984254"],"confidence":"High","gaps":["Structural basis of mallotoxin sensitivity loss unresolved","Single lab"]},{"year":2014,"claim":"Demonstrated LRRC26 functions as a bona fide γ subunit in vascular smooth muscle, controlling myogenic tone.","evidence":"Co-IP, FRET, biotinylation, RNAi knockdown, and patch-clamp with myogenic tone measurement in cerebral artery myocytes","pmids":["24906643"],"confidence":"High","gaps":["In vivo vascular consequences of loss not tested with a genetic model here"]},{"year":2018,"claim":"Identified a channel-independent role: LRRC26 suppresses NF-κB signaling and tumor-cell invasion, and is epigenetically silenced in cancer.","evidence":"siRNA/overexpression, NF-κB luciferase reporter, invasion/migration assays, bisulfite pyrosequencing and 5-aza-dC in triple-negative breast cancer cells","pmids":["29512727"],"confidence":"Medium","gaps":["Molecular mechanism linking LRRC26 to NF-κB is not defined","Whether this is BK-dependent is untested","Single lab"]},{"year":2017,"claim":"Showed via genetic knockout that LRRC26 is required for BK-driven secretory function in epithelia, linking the gating shift to organismal K⁺ secretion.","evidence":"LRRC26 KO mice with β-gal reporter, co-IP across lacrimal/parotid/colon, acinar patch-clamp, and saliva ion analysis","pmids":["28416688"],"confidence":"High","gaps":["Quantitative contribution to fluid secretion across tissues not fully partitioned"]},{"year":2019,"claim":"Extended γ1 occupancy to bronchial smooth muscle, distinguishing it functionally from aortic SMC by gating and mallotoxin response.","evidence":"Co-IP, TIRF imaging, whole-cell patch-clamp, qPCR and Western in bronchial vs. aortic SMCs","pmids":["31800260"],"confidence":"Medium","gaps":["Physiological/airway consequences not tested in vivo","Single lab"]},{"year":2021,"claim":"Connected LRRC26-associated BK activity in colonic goblet cells to transepithelial K⁺ current and protection from colitis.","evidence":"LRRC26 KO and MUC2-reporter mice, goblet-cell patch-clamp, transepithelial current measurements, DSS colitis model","pmids":["33431687"],"confidence":"High","gaps":["Mechanistic link between goblet-cell K⁺ flux and mucosal barrier protection not fully defined"]},{"year":2026,"claim":"Resolved the gating mechanism, showing γ1 acts on the closed-open transition and coupling rather than voltage-sensor movement.","evidence":"Macroscopic, single-channel, and gating-current measurements of BKα ± LRRC26 in heterologous expression","pmids":["41701845"],"confidence":"High","gaps":["Atomic-level interface mediating coupling enhancement not defined"]},{"year":2026,"claim":"Defined the functional stoichiometry, showing one γ1 per BKα tetramer suffices for full modulation (all-or-none).","evidence":"Concatenated tandem BKα constructs with fused γ1, mutagenesis, and voltage-clamp in heterologous cells","pmids":["41784352"],"confidence":"High","gaps":["Whether native channels carry one vs. multiple γ1 subunits not measured","Structural arrangement of the single γ1 not resolved"]},{"year":null,"claim":"The molecular mechanism by which LRRC26 suppresses NF-κB signaling, and whether this is separable from its BK channel role, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct LRRC26 binding partner in the NF-κB pathway identified","No structural model of the BKα–γ1 interface","Native subunit stoichiometry in tissue uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,3,7,8]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,3,4]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[3,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,7]}],"complexes":["BK (BKα/Slo1) channel complex"],"partners":["KCNMA1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q2I0M4","full_name":"Leucine-rich repeat-containing protein 26","aliases":["BK channel auxiliary gamma subunit LRRC26","Cytokeratin-associated protein in cancer"],"length_aa":334,"mass_kda":34.9,"function":"Auxiliary protein of the large-conductance, voltage and calcium-activated potassium channel (BK alpha). Required for the conversion of BK alpha channels from a high-voltage to a low-voltage activated channel type in non-excitable cells. These are characterized by negative membrane voltages and constant low levels of calcium","subcellular_location":"Cell membrane; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/Q2I0M4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LRRC26","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/LRRC26","total_profiled":1310},"omim":[{"mim_id":"615218","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 52; LRRC52","url":"https://www.omim.org/entry/615218"},{"mim_id":"615213","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 55; LRRC55","url":"https://www.omim.org/entry/615213"},{"mim_id":"615212","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 38; LRRC38","url":"https://www.omim.org/entry/615212"},{"mim_id":"613505","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 26; LRRC26","url":"https://www.omim.org/entry/613505"},{"mim_id":"600150","title":"POTASSIUM CHANNEL, CALCIUM-ACTIVATED, LARGE CONDUCTANCE, SUBFAMILY M, ALPHA MEMBER 1; KCNMA1","url":"https://www.omim.org/entry/600150"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Nucleoli fibrillar center","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"salivary gland","ntpm":285.7}],"url":"https://www.proteinatlas.org/search/LRRC26"},"hgnc":{"alias_symbol":["bA350O14.10","OTTHUMG00000020980"],"prev_symbol":[]},"alphafold":{"accession":"Q2I0M4","domains":[{"cath_id":"3.80.10.10","chopping":"43-203","consensus_level":"medium","plddt":95.4496,"start":43,"end":203},{"cath_id":"1.20.5","chopping":"254-283","consensus_level":"medium","plddt":81.7137,"start":254,"end":283}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q2I0M4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q2I0M4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q2I0M4-F1-predicted_aligned_error_v6.png","plddt_mean":82.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LRRC26","jax_strain_url":"https://www.jax.org/strain/search?query=LRRC26"},"sequence":{"accession":"Q2I0M4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q2I0M4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q2I0M4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q2I0M4"}},"corpus_meta":[{"pmid":"20613726","id":"PMC_20613726","title":"LRRC26 auxiliary protein allows BK channel activation at resting voltage without calcium.","date":"2010","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/20613726","citation_count":196,"is_preprint":false},{"pmid":"24906643","id":"PMC_24906643","title":"LRRC26 is a functional BK channel auxiliary γ subunit in arterial smooth muscle cells.","date":"2014","source":"Circulation research","url":"https://pubmed.ncbi.nlm.nih.gov/24906643","citation_count":62,"is_preprint":false},{"pmid":"21984254","id":"PMC_21984254","title":"The LRRC26 protein selectively alters the efficacy of BK channel activators.","date":"2011","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21984254","citation_count":37,"is_preprint":false},{"pmid":"28416688","id":"PMC_28416688","title":"Knockout of the LRRC26 subunit reveals a primary role of LRRC26-containing BK channels in secretory epithelial cells.","date":"2017","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/28416688","citation_count":30,"is_preprint":false},{"pmid":"33431687","id":"PMC_33431687","title":"Goblet cell LRRC26 regulates BK channel activation and protects against colitis in mice.","date":"2021","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/33431687","citation_count":22,"is_preprint":false},{"pmid":"29512727","id":"PMC_29512727","title":"Frequent downregulation of LRRC26 by epigenetic alterations is involved in the malignant progression of triple-negative breast cancer.","date":"2018","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/29512727","citation_count":15,"is_preprint":false},{"pmid":"31800260","id":"PMC_31800260","title":"Roles of LRRC26 as an auxiliary γ1-subunit of large-conductance Ca2+-activated K+ channels in bronchial smooth muscle cells.","date":"2019","source":"American journal of physiology. Lung cellular and molecular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/31800260","citation_count":9,"is_preprint":false},{"pmid":"40950215","id":"PMC_40950215","title":"Tuning the gate and the gear: The LRRC26 (  ) subunit modulates intrinsic gating and voltage-sensor coupling of the BK channel.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40950215","citation_count":1,"is_preprint":false},{"pmid":"41701845","id":"PMC_41701845","title":"Tuning the gate and the gear: The LRRC26 (γ1) subunit modulates intrinsic gating and voltage-sensor coupling of the BK channel.","date":"2026","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/41701845","citation_count":0,"is_preprint":false},{"pmid":"41784352","id":"PMC_41784352","title":"Concatenated modular BK channel constructs reveal divergent stoichiometry in gating control by LRRC26 (γ1), pore, and selectivity filter.","date":"2026","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/41784352","citation_count":0,"is_preprint":false},{"pmid":"31265510","id":"PMC_31265510","title":"Correction to\"The LRRC26 Protein Selectively Alters the Efficacy of BK Channel Activators\".","date":"2016","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/31265510","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7402,"output_tokens":2713,"usd":0.03145,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10067,"output_tokens":2858,"usd":0.060893,"stage2_stop_reason":"end_turn"},"total_usd":0.092343,"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\": 2010,\n      \"finding\": \"LRRC26 is an auxiliary protein of BK (BKα) channels that produces an unprecedented ~140 mV negative shift in voltage dependence, enabling BK channel activation at resting voltage without elevated cytosolic Ca²⁺. The mechanism involves enhanced allosteric coupling between voltage-sensor activation and the channel's closed-open transition.\",\n      \"method\": \"Electrophysiology (patch-clamp) in LNCaP prostate cancer cells and heterologous expression; functional characterization of BKα–LRRC26 complex\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — foundational electrophysiology with functional reconstitution, replicated across multiple subsequent studies\",\n      \"pmids\": [\"20613726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"LRRC26 selectively alters the pharmacology of BK channels: it strongly inhibits the ability of mallotoxin (MTX) to activate BK channels (reducing MTX-induced voltage shift from ~70 mV to ~6 mV) while having only a small effect on NS-1619 activation, indicating that the accessory protein differentially modulates activator efficacy.\",\n      \"method\": \"Electrophysiology in native parotid acinar cells and heterologous expression of parSlo ± LRRC26; pharmacological assays with MTX and NS-1619\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct functional electrophysiology with pharmacological dissection in both native and heterologous systems, single lab\",\n      \"pmids\": [\"21984254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In arterial smooth muscle cells, LRRC26 co-localizes with and co-immunoprecipitates with plasma membrane BKα subunits. LRRC26 knockdown reduces BK channel voltage sensitivity and apparent Ca²⁺ sensitivity, decreases transient BK current frequency and amplitude, and increases myogenic tone, establishing LRRC26 as a functional BK channel γ subunit in vascular smooth muscle.\",\n      \"method\": \"Co-immunoprecipitation, FRET microscopy, biotinylation (surface localization), RNAi knockdown, patch-clamp electrophysiology, myogenic tone measurements in cerebral artery myocytes\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, FRET, functional KD with defined electrophysiological and vascular phenotype; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"24906643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"LRRC26 (γ1) co-assembles with BK α-subunits specifically in secretory epithelial cells (lacrimal gland, parotid gland, colon). In LRRC26 KO mice, BK channel gating in acinar cells shifts to resemble α-subunit-only channels (rightward voltage shift), and salivary [K⁺] is reduced, demonstrating LRRC26 is required for BK channel activation at physiological resting potentials to support secretory function.\",\n      \"method\": \"LRRC26 KO mice with β-gal reporter, co-immunoprecipitation in multiple tissues, patch-clamp in acinar cells, ion composition analysis of saliva\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined electrophysiological and physiological phenotype, co-IP in multiple native tissues, replicated across tissues\",\n      \"pmids\": [\"28416688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In bronchial smooth muscle cells (BSMCs), LRRC26 (γ1) is highly expressed and interacts with BKα (shown by co-immunoprecipitation and TIRF imaging). BK channel steady-state activation in BSMCs occurs at more negative voltages (resembling BKα/γ1 reconstituted channels) compared to aortic SMCs or BKα-only channels. Mallotoxin (a BK activator selective for channels lacking γ1) activates BK currents in aortic SMCs but not in BSMCs, functionally confirming γ1 occupancy.\",\n      \"method\": \"Co-immunoprecipitation, total internal reflection fluorescence (TIRF) imaging, whole-cell patch-clamp electrophysiology, real-time PCR, Western blot in bronchial SMCs vs. aortic SMCs\",\n      \"journal\": \"American journal of physiology. Lung cellular and molecular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, TIRF, and pharmacological functional evidence; single lab\",\n      \"pmids\": [\"31800260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"LRRC26-associated BK channels are present and functionally active specifically in colonic goblet cells (GCs) at physiological conditions; in LRRC26 KO mice, BK channels are present in GCs but not activated under physiological conditions. LRRC26-associated BK channels underlie the resting transepithelial K⁺ current across distal colonic mucosa, and genetic ablation of LRRC26 (or BK α-subunit) dramatically increases susceptibility to DSS-induced colitis.\",\n      \"method\": \"LRRC26 KO mice, MUC2-fluorescent reporter mice, patch-clamp in isolated GCs, transepithelial current measurements, DSS colitis model\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with electrophysiological and disease phenotype, single-cell functional imaging, multiple orthogonal methods\",\n      \"pmids\": [\"33431687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"LRRC26 negatively regulates NF-κB signaling in triple-negative breast cancer cells. LRRC26 overexpression reduces TNF-α-mediated NF-κB luciferase reporter activity and downstream gene expression (IL-6, IL-8, CXCL1), while LRRC26 knockdown upregulates these NF-κB target genes. LRRC26 knockdown also enhances anchorage-independent growth, invasion, and migration. Loss of LRRC26 expression is associated with promoter methylation (restored by 5-aza-dC treatment).\",\n      \"method\": \"siRNA knockdown and ectopic overexpression, NF-κB luciferase reporter assay, anchorage-independent growth assay, invasion/migration assays, bisulfite pyrosequencing, 5-aza-dC treatment\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — reporter assay and loss/gain-of-function with multiple functional readouts; single lab\",\n      \"pmids\": [\"29512727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Using macroscopic, single-channel, and gating-current measurements, LRRC26 (γ1) is shown to increase the equilibrium constant for BK channel closed-open transition by ~106-fold at zero mV by destabilizing the closed state and enhancing voltage-sensor–pore coupling, without affecting voltage-sensor activation per se. This clarifies a mechanistic controversy by identifying that γ1 primarily enhances the channel-opening reaction and energetic coupling, not voltage-sensor movement.\",\n      \"method\": \"Macroscopic patch-clamp, single-channel recordings, and gating-current measurements in heterologous expression of BKα ± LRRC26 (γ1)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — three orthogonal electrophysiological methods (macroscopic, single-channel, gating currents) directly measuring distinct aspects of gating; single lab\",\n      \"pmids\": [\"41701845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Using concatenated BKα constructs (tandem dimers and tetramers), a single LRRC26 (γ1) subunit per BKα tetramer is sufficient to fully shift BK channel voltage activation (all-or-none stoichiometry), distinct from the stoichiometrically graded effect of a deep-pore L312A mutation and the all-four-subunit requirement for V288A selectivity filter inactivation.\",\n      \"method\": \"Concatenated tandem BKα subunit constructs with fused γ1, co-expression, electrophysiology (voltage-clamp) in heterologous expression system\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — engineered concatenated constructs with controlled stoichiometry plus mutagenesis and functional electrophysiology; single lab, multiple orthogonal approaches within study\",\n      \"pmids\": [\"41784352\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LRRC26 (γ1) is an auxiliary subunit of large-conductance Ca²⁺- and voltage-activated BK (BKα) channels that produces a ~140 mV leftward shift in voltage-dependent activation by destabilizing the channel's closed state and enhancing voltage-sensor–pore coupling (without altering voltage-sensor movement itself); a single γ1 subunit per α-subunit tetramer is sufficient for full modulation, and this activity enables BK channel opening at physiological resting potentials and Ca²⁺ concentrations in secretory epithelial cells (lacrimal, salivary glands, goblet cells) and smooth muscle cells, supporting K⁺ secretion, transepithelial transport, vasodilation, and protection against colitis, while in cancer cells LRRC26 also suppresses NF-κB signaling to limit invasion and migration.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"LRRC26 is the prototypical auxiliary γ1 subunit of large-conductance Ca²⁺- and voltage-activated BK (BKα) channels, conferring channel activation at physiological resting potentials without elevated cytosolic Ca²⁺ by producing a ~140 mV leftward shift in voltage-dependent activation [#0]. Mechanistically, LRRC26 acts on the channel-opening reaction itself: it increases the closed-open equilibrium constant ~10⁶-fold at zero mV by destabilizing the closed state and enhancing voltage-sensor–pore coupling, without altering voltage-sensor movement per se [#7], and a single γ1 subunit per BKα tetramer is sufficient for the full all-or-none gating shift [#8]. This modulation also reshapes BK pharmacology, strongly suppressing mallotoxin efficacy [#1]. Physiologically, LRRC26 co-assembles with surface BKα in secretory epithelia and smooth muscle, where its loss reverts gating toward α-only behavior: in vascular and bronchial smooth muscle it sets BK voltage and Ca²⁺ sensitivity and limits myogenic tone [#2, #4], and in secretory epithelial cells (lacrimal, parotid, colonic goblet cells) it is required for BK-dependent K⁺ secretion, transepithelial K⁺ transport, and protection against DSS-induced colitis [#3, #5]. Beyond its channel role, LRRC26 negatively regulates NF-κB signaling in triple-negative breast cancer cells, where its methylation-associated silencing de-represses inflammatory target genes and promotes invasion and migration [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Established that LRRC26 is a BK channel auxiliary protein, answering how BK channels can open at resting voltage without high Ca²⁺ by enhancing allosteric voltage-sensor/gate coupling.\",\n      \"evidence\": \"Patch-clamp electrophysiology of BKα–LRRC26 complexes in LNCaP cells and heterologous expression\",\n      \"pmids\": [\"20613726\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether the shift arises from altered voltage-sensor movement vs. the opening reaction\", \"Subunit stoichiometry not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed LRRC26 reshapes BK pharmacology, distinguishing γ1-occupied from α-only channels through differential activator efficacy.\",\n      \"evidence\": \"Electrophysiology with mallotoxin and NS-1619 in native parotid acinar cells and heterologous parSlo ± LRRC26\",\n      \"pmids\": [\"21984254\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of mallotoxin sensitivity loss unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated LRRC26 functions as a bona fide γ subunit in vascular smooth muscle, controlling myogenic tone.\",\n      \"evidence\": \"Co-IP, FRET, biotinylation, RNAi knockdown, and patch-clamp with myogenic tone measurement in cerebral artery myocytes\",\n      \"pmids\": [\"24906643\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo vascular consequences of loss not tested with a genetic model here\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified a channel-independent role: LRRC26 suppresses NF-κB signaling and tumor-cell invasion, and is epigenetically silenced in cancer.\",\n      \"evidence\": \"siRNA/overexpression, NF-κB luciferase reporter, invasion/migration assays, bisulfite pyrosequencing and 5-aza-dC in triple-negative breast cancer cells\",\n      \"pmids\": [\"29512727\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism linking LRRC26 to NF-κB is not defined\", \"Whether this is BK-dependent is untested\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Showed via genetic knockout that LRRC26 is required for BK-driven secretory function in epithelia, linking the gating shift to organismal K⁺ secretion.\",\n      \"evidence\": \"LRRC26 KO mice with β-gal reporter, co-IP across lacrimal/parotid/colon, acinar patch-clamp, and saliva ion analysis\",\n      \"pmids\": [\"28416688\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution to fluid secretion across tissues not fully partitioned\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended γ1 occupancy to bronchial smooth muscle, distinguishing it functionally from aortic SMC by gating and mallotoxin response.\",\n      \"evidence\": \"Co-IP, TIRF imaging, whole-cell patch-clamp, qPCR and Western in bronchial vs. aortic SMCs\",\n      \"pmids\": [\"31800260\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological/airway consequences not tested in vivo\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Connected LRRC26-associated BK activity in colonic goblet cells to transepithelial K⁺ current and protection from colitis.\",\n      \"evidence\": \"LRRC26 KO and MUC2-reporter mice, goblet-cell patch-clamp, transepithelial current measurements, DSS colitis model\",\n      \"pmids\": [\"33431687\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between goblet-cell K⁺ flux and mucosal barrier protection not fully defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Resolved the gating mechanism, showing γ1 acts on the closed-open transition and coupling rather than voltage-sensor movement.\",\n      \"evidence\": \"Macroscopic, single-channel, and gating-current measurements of BKα ± LRRC26 in heterologous expression\",\n      \"pmids\": [\"41701845\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-level interface mediating coupling enhancement not defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Defined the functional stoichiometry, showing one γ1 per BKα tetramer suffices for full modulation (all-or-none).\",\n      \"evidence\": \"Concatenated tandem BKα constructs with fused γ1, mutagenesis, and voltage-clamp in heterologous cells\",\n      \"pmids\": [\"41784352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether native channels carry one vs. multiple γ1 subunits not measured\", \"Structural arrangement of the single γ1 not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which LRRC26 suppresses NF-κB signaling, and whether this is separable from its BK channel role, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct LRRC26 binding partner in the NF-κB pathway identified\", \"No structural model of the BKα–γ1 interface\", \"Native subunit stoichiometry in tissue uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 3, 7, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"complexes\": [\"BK (BKα/Slo1) channel complex\"],\n    \"partners\": [\"KCNMA1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}