{"gene":"LHFPL5","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2005,"finding":"TMHS (LHFPL5) is a tetraspan transmembrane protein localized to the apical membrane and hair bundles of inner ear hair cells; loss-of-function (missense C→F substitution) causes disorganized hair bundles, progressive hair cell loss, deafness, and vestibular dysfunction in mice, establishing its role in hair bundle morphogenesis/stereocilia development.","method":"Positional cloning, immunofluorescence with specific polyclonal antibodies, scanning electron microscopy of cochleae from Tmhs mutant (hscy) mice","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — clean KO/mutant with specific cellular phenotype, direct localization by immunofluorescence, replicated in subsequent studies","pmids":["15905332"],"is_preprint":false},{"year":2007,"finding":"Targeted null mutation of Tmhs (LHFPL5) phenocopies the hscy missense mutation, confirming that loss of LHFPL5 alone causes deafness and vestibular dysfunction; lacZ reporter shows expression peaks around P0 and is absent by P15, consistent with a role in stereocilia development.","method":"Targeted gene knockout (Tmhs tm1Kjn), lacZ reporter driven by Tmhs promoter, beta-galactosidase activity visualization, auditory/vestibular phenotyping","journal":"Mammalian genome : official journal of the International Mammalian Genome Society","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined phenotype and reporter-based temporal expression analysis, confirming previous findings","pmids":["17876667"],"is_preprint":false},{"year":2012,"finding":"TMHS (LHFPL5) physically binds to the tip-link component PCDH15, regulates tip-link assembly, controls transducer channel conductance, and is required for fast channel adaptation; it functions as an integral component of the hair cell mechanotransduction machinery analogous to TARP subunits of AMPA receptors.","method":"Co-immunoprecipitation, electrophysiology (mechanotransduction recordings), genetic knockout mice (Tmhs-/-), immunofluorescence, deafness mutation analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 — reciprocal Co-IP, electrophysiology, KO mice with multiple orthogonal readouts; highly cited foundational study replicated by later work","pmids":["23217710"],"is_preprint":false},{"year":2017,"finding":"LHFPL5 localization to stereocilia tips requires PCDH15; in PCDH15-deficient mice, LHFPL5 fails to reach tips and instead distributes to unranked stereocilia and lower lateral links. LHFPL5 is present in the MET apparatus as early as P0 and shows higher expression in apical than basal bundles.","method":"Immunofluorescence and immunogold transmission electron microscopy in wild-type and PCDH15-deficient mice across developmental time points (P0–P21)","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — direct localization experiment with genetic manipulation (PCDH15 KO) and functional consequence for tip localization, using immunogold EM","pmids":["29069081"],"is_preprint":false},{"year":2018,"finding":"Crystal/cryo structure of the PCDH15–LHFPL5 complex reveals a heterotetramer (two PCDH15 and two LHFPL5 subunits) with a 2-fold symmetric 'collar' near the membrane; LHFPL5 forms extensive interactions with PCDH15 transmembrane helices, stabilizing the overall assembly and placing deafness mutations at critical interfaces.","method":"X-ray crystallography and cryo-EM structural determination, analytical ultracentrifugation (AUC), biochemical reconstitution of PCDH15–LHFPL5 complex","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 — high-resolution structure with biochemical validation; single rigorous paper with multiple orthogonal structural and biophysical methods","pmids":["30070639"],"is_preprint":false},{"year":2019,"finding":"TMC1 and LHFPL5 co-localize at the tips of shorter stereocilia rows in neonatal hair cells; in adult inner hair cells, LHFPL5 distributes uniformly across shorter stereocilia rows while TMC1 distributes to all rows, suggesting distinct regulation in mature cells.","method":"Immunofluorescence, super-resolution microscopy, fractionation/localization in neonatal and adult mouse cochlear hair cells","journal":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization with developmental comparison, single lab","pmids":["30808210"],"is_preprint":false},{"year":2020,"finding":"LHFPL5 physically interacts with TMC1 and stabilizes TMC1 protein expression in both heterologous cells and native hair cells (soma and hair bundle); the semidominant deafness mutation D572N in human TMC1 (D569N in mouse) severely disrupts LHFPL5 binding and destabilizes TMC1.","method":"Single-molecule pulldown (SiMPull) assay, co-immunoprecipitation, heterologous expression systems, immunofluorescence in hair cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (SiMPull, Co-IP, native hair cell analysis) with mutagenesis functional validation","pmids":["33168709"],"is_preprint":false},{"year":2020,"finding":"In zebrafish, Lhfpl5a/b localization at stereocilia tips requires tip-link cadherins Pcdh15a and Cdh23, as well as the Myo7aa motor protein; however, in contrast to mice, TMC1/TMC2b localization to stereocilia does not depend on Lhfpl5, revealing species-specific differences in MET complex assembly.","method":"Genetic mutant analysis (lhfpl5a/b knockout zebrafish), GFP-tagged transgene localization, hair cell electrophysiology (mechanotransduction recordings), FM dye uptake","journal":"Frontiers in molecular neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with GFP reporter, electrophysiology, and multiple mutant backgrounds","pmids":["32009898"],"is_preprint":false},{"year":2023,"finding":"An extracellular loop 1 region of LHFPL5 (which interacts with PCDH15) contains sequences that preclude trafficking to the plasma membrane in heterologous cells; PCDH15 co-expression is required to mask ER retention signals or enable proper folding and trafficking of LHFPL5 to the plasma membrane.","method":"Aquaporin 3-tGFP plasma membrane reporter (AGR) assay, domain deletion and chimeric LHFPL5 constructs in heterologous cell lines, immunofluorescence","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment with reporter construct and domain mapping; single lab","pmids":["36781873"],"is_preprint":false},{"year":2023,"finding":"LHFPL5 directly couples the PCDH15 tip link to the TMC1 MET channel via its N-terminal cytoplasmic domain, which binds an amphipathic helix in TMC1 that is a conserved gating domain; mutations in either the LHFPL5 N-terminus or the TMC1 amphipathic helix that disrupt this interaction reduce channel responses to mechanical force, supporting a tether model for MET channel gating.","method":"Co-immunoprecipitation, electrophysiology (MET channel recordings), site-directed mutagenesis of LHFPL5 N-terminal domain and TMC1 amphipathic helix, mouse knockout/knock-in models","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 — mutagenesis, Co-IP, and electrophysiology with multiple mutant combinations; rigorous mechanistic study","pmids":["36917610"],"is_preprint":false},{"year":2024,"finding":"LHFPL5 is a principal component of the gating spring that transmits tip-link tension to the MET channel: in Lhfpl5-/- outer hair cells, the MET working range more than doubles and single-channel gating force (Z) decreases by >60%, while gating stiffness (inferred from stiffness change upon tip-link destruction) is virtually abolished. The Tmc1 D569N mutation reduces LHFPL5 immunolabeling in stereocilia and similarly doubles the MET working range.","method":"Electrophysiology (MET channel recordings in Lhfpl5-/- and Lhfpl5+/- mice), hair bundle stiffness measurements, immunofluorescence","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 — quantitative electrophysiology with defined KO/heterozygote comparison, stiffness measurements, and mutagenesis; strong mechanistic evidence","pmids":["38194445"],"is_preprint":false},{"year":2025,"finding":"An LHFPL5 mutant lacking just three N-terminal amino acids causes recessive deafness and severely impairs MET channel activation; resting open probability is increased but unitary conductance, adaptation, and tonotopic properties are normal, and MET channel proteins remain in stereocilia at normal levels. This establishes that the LHFPL5 N-terminus is specifically required for maximal mechanical activation of MET channels without affecting channel assembly or adaptation.","method":"Knock-in mouse expressing N-terminal LHFPL5 deletion mutant, electrophysiology (MET recordings), immunofluorescence for MET channel components in stereocilia","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 — targeted knock-in mutagenesis with electrophysiology and localization controls, dissecting distinct functional domains","pmids":["41187086"],"is_preprint":false},{"year":2026,"finding":"Single-molecule pulldown (SiMPull) and single-molecule array (SiMoA) assays applied to native mouse cochlea and utricle establish that the PCDH15–LHFPL5 complex is a heterotetrameric assembly (two PCDH15 and two LHFPL5 subunits), confirming the stoichiometry of the tip-link complex in native tissue.","method":"Single-molecule pulldown (SiMPull), single-molecule array (SiMoA) with native protein from mouse cochlea and utricle","journal":"Biophysical journal","confidence":"High","confidence_rationale":"Tier 1 — single-molecule stoichiometry assays on native tissue, orthogonal to prior structural data","pmids":["41668373"],"is_preprint":false}],"current_model":"LHFPL5 (TMHS) is an integral tetraspan auxiliary subunit of the hair cell mechano-electrical transduction (MET) channel complex that directly binds PCDH15 (tip-link component) via its extracellular loop and TMC1 (pore-forming channel subunit) via its N-terminal cytoplasmic domain, thereby coupling tip-link tension to channel gating as a principal component of the gating spring, stabilizing TMC1 expression, and enabling maximal force sensitivity and fast adaptation of the MET channel."},"narrative":{"teleology":[{"year":2005,"claim":"Identification of LHFPL5 as a hair-bundle protein whose loss causes deafness established the first genetic link between this tetraspan protein family and inner ear mechanosensory function.","evidence":"Positional cloning of the hscy mouse mutant, immunofluorescence localization to hair bundles, and scanning electron microscopy showing disorganized stereocilia","pmids":["15905332"],"confidence":"High","gaps":["Molecular partners within the MET complex unknown","Whether LHFPL5 is required for mechanotransduction per se versus hair bundle development unclear","No biochemical interaction data"]},{"year":2007,"claim":"A targeted null allele phenocopied the original missense mutation, confirming that LHFPL5 loss alone is sufficient for deafness and revealing a developmental expression window peaking near birth.","evidence":"Tmhs knockout mice with lacZ reporter and auditory/vestibular phenotyping","pmids":["17876667"],"confidence":"High","gaps":["Mechanism of action at the molecular level still unknown","Relationship to MET channel components not tested"]},{"year":2012,"claim":"Demonstration that LHFPL5 physically binds PCDH15, regulates transducer channel conductance, and is required for fast adaptation established it as an integral auxiliary subunit of the MET channel, analogous to TARPs for AMPA receptors.","evidence":"Reciprocal co-immunoprecipitation, mechanotransduction electrophysiology in Tmhs-/- mice, immunofluorescence","pmids":["23217710"],"confidence":"High","gaps":["Structural basis of PCDH15–LHFPL5 interaction unknown","Whether LHFPL5 directly contacts the pore-forming subunit TMC1 not tested","Stoichiometry of the complex undetermined"]},{"year":2017,"claim":"Establishing that PCDH15 is required for LHFPL5 localization to stereocilia tips resolved the epistatic hierarchy of MET complex assembly, placing tip-link formation upstream of LHFPL5 recruitment.","evidence":"Immunogold electron microscopy and immunofluorescence in PCDH15-deficient and wild-type mice across developmental stages","pmids":["29069081"],"confidence":"High","gaps":["Whether LHFPL5 mislocalization alone explains MET loss or additional functions are disrupted","Mechanism by which PCDH15 enables LHFPL5 trafficking unknown"]},{"year":2018,"claim":"Solving the crystal/cryo-EM structure of the PCDH15–LHFPL5 complex revealed a heterotetrameric architecture with deafness mutations mapping to the interface, providing the first atomic framework for understanding how the tip link couples to the channel.","evidence":"X-ray crystallography, cryo-EM, and analytical ultracentrifugation of reconstituted PCDH15–LHFPL5 complex","pmids":["30070639"],"confidence":"High","gaps":["Structure of the full MET complex including TMC1 lacking","Conformational changes during gating not captured","Native stoichiometry not confirmed in vivo"]},{"year":2020,"claim":"Discovery that LHFPL5 directly binds and stabilizes TMC1 protein expression — and that the human deafness mutation TMC1-D572N disrupts this interaction — identified LHFPL5 as the physical link between the tip link and the channel pore.","evidence":"Single-molecule pulldown, co-immunoprecipitation, heterologous expression, and immunofluorescence in native hair cells; combined with zebrafish epistasis showing species-specific assembly differences","pmids":["33168709","32009898"],"confidence":"High","gaps":["Binding interface between LHFPL5 and TMC1 not mapped at residue level","Whether LHFPL5 also contacts TMC2 with similar affinity unknown"]},{"year":2023,"claim":"Mapping the LHFPL5 N-terminal domain as the TMC1-binding element that couples to a conserved gating helix in TMC1, combined with the finding that PCDH15 is required to mask ER-retention signals in LHFPL5, defined the molecular logic of the tripartite PCDH15–LHFPL5–TMC1 force-transmission pathway.","evidence":"Site-directed mutagenesis of LHFPL5 N-terminus and TMC1 amphipathic helix with Co-IP and MET electrophysiology in knock-in mice; AGR trafficking assay with chimeric LHFPL5 constructs in heterologous cells","pmids":["36917610","36781873"],"confidence":"High","gaps":["Structural model of the LHFPL5–TMC1 interface lacking","Trafficking mechanism in native hair cells not directly tested"]},{"year":2024,"claim":"Quantitative biophysical measurements in Lhfpl5-/- hair cells revealed that LHFPL5 contributes the majority of gating-spring stiffness and sets single-channel gating force, establishing it as the principal gating-spring element rather than merely an auxiliary subunit.","evidence":"Hair bundle stiffness measurements and MET channel electrophysiology in Lhfpl5-/- and Lhfpl5+/- outer hair cells; comparison with Tmc1-D569N mutant","pmids":["38194445"],"confidence":"High","gaps":["Whether LHFPL5 contributes elasticity intrinsically or via organizing other elements unclear","No direct measurement of LHFPL5 mechanical compliance"]},{"year":2025,"claim":"A three-amino-acid N-terminal deletion knock-in cleanly separated LHFPL5's force-transmission role from its channel-assembly function, showing that the N-terminus is specifically required for maximal MET activation but dispensable for channel localization and adaptation.","evidence":"Knock-in mouse with minimal N-terminal LHFPL5 deletion, MET electrophysiology, immunofluorescence for MET complex components","pmids":["41187086"],"confidence":"High","gaps":["Whether these three residues directly contact TMC1 amphipathic helix not resolved structurally","Contribution of individual residues not dissected"]},{"year":2026,"claim":"Single-molecule assays on native cochlear and utricular tissue confirmed the 2:2 PCDH15:LHFPL5 heterotetrameric stoichiometry in vivo, validating the structural model in a physiological context.","evidence":"SiMPull and SiMoA applied to native mouse cochlea and utricle protein","pmids":["41668373"],"confidence":"High","gaps":["Full stoichiometry of the complete MET complex (including TMC1/2) in native tissue remains undetermined","Whether stoichiometry differs between vestibular and auditory hair cell types not explored"]},{"year":null,"claim":"A high-resolution structure of the complete PCDH15–LHFPL5–TMC1 ternary complex and direct measurements of LHFPL5's intrinsic mechanical compliance are needed to explain how this protein generates or transmits gating-spring stiffness at the molecular level.","evidence":"","pmids":[],"confidence":"High","gaps":["No ternary complex structure available","Intrinsic elasticity of LHFPL5 not measured","Whether LHFPL5 interacts with TMC2 in the same manner is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[4,10,11]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,6,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,3,5,8]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,3,5]}],"pathway":[{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[0,2,10,11]}],"complexes":["PCDH15–LHFPL5 heterotetramer","MET channel complex (PCDH15–LHFPL5–TMC1)"],"partners":["PCDH15","TMC1","CDH23"],"other_free_text":[]},"mechanistic_narrative":"LHFPL5 (also known as TMHS) is a tetraspan transmembrane auxiliary subunit of the hair cell mechano-electrical transduction (MET) channel complex that physically couples tip-link tension to channel gating in auditory and vestibular sensory cells. LHFPL5 forms a heterotetrameric assembly with PCDH15 (two LHFPL5 and two PCDH15 subunits) through extensive transmembrane and extracellular loop interactions, requiring PCDH15 for proper trafficking to stereocilia tips and plasma membrane insertion [PMID:30070639, PMID:29069081, PMID:36781873, PMID:41668373]. Its N-terminal cytoplasmic domain binds a conserved amphipathic helix in TMC1, the pore-forming channel subunit, stabilizing TMC1 expression and directly transmitting mechanical force to the channel gate; disruption of this interface by point mutations or small N-terminal deletions causes deafness with severely impaired MET activation while leaving channel assembly and adaptation intact [PMID:36917610, PMID:33168709, PMID:41187086]. Loss of LHFPL5 virtually abolishes gating-spring stiffness and reduces single-channel gating force by more than 60%, establishing LHFPL5 as a principal component of the gating spring that sets the force sensitivity and working range of mechanotransduction [PMID:38194445, PMID:15905332]."},"prefetch_data":{"uniprot":{"accession":"Q8TAF8","full_name":"LHFPL tetraspan subfamily member 5 protein","aliases":["Lipoma HMGIC fusion partner-like 5 protein","Tetraspan membrane protein of hair cell stereocilia"],"length_aa":219,"mass_kda":24.2,"function":"Auxiliary subunit of the mechanotransducer (MET) non-specific cation channel complex located at the tips of the shorter stereocilia of cochlear hair cells and that mediates sensory transduction in the auditory system. The MET complex is composed of two dimeric pore-forming ion-conducting transmembrane TMC (TMC1 or TMC2) subunits, and aided by several auxiliary proteins including LHFPL5, TMIE, CIB2/3 and TOMT, and the tip-link PCDH15. Functionally couples PCDH15 to the transduction channel","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q8TAF8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LHFPL5","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/LHFPL5","total_profiled":1310},"omim":[{"mim_id":"614218","title":"WD REPEAT-CONTAINING PROTEIN 81; WDR81","url":"https://www.omim.org/entry/614218"},{"mim_id":"610265","title":"DEAFNESS, AUTOSOMAL RECESSIVE 67; DFNB67","url":"https://www.omim.org/entry/610265"},{"mim_id":"610240","title":"LHFPL TETRASPAN SUBFAMILY, MEMBER 4; LHFPL4","url":"https://www.omim.org/entry/610240"},{"mim_id":"610185","title":"CEREBELLAR ATAXIA, IMPAIRED INTELLECTUAL DEVELOPMENT, AND DYSEQUILIBRIUM SYNDROME 2; CAMRQ2","url":"https://www.omim.org/entry/610185"},{"mim_id":"609427","title":"LHFPL TETRASPAN SUBFAMILY, MEMBER 5; LHFPL5","url":"https://www.omim.org/entry/609427"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"bone marrow","ntpm":17.2},{"tissue":"epididymis","ntpm":11.6}],"url":"https://www.proteinatlas.org/search/LHFPL5"},"hgnc":{"alias_symbol":["MGC33835","dJ510O8.8","Tmhs"],"prev_symbol":["DFNB67"]},"alphafold":{"accession":"Q8TAF8","domains":[{"cath_id":"1.20.140.150","chopping":"47-205","consensus_level":"medium","plddt":93.1394,"start":47,"end":205}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TAF8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TAF8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TAF8-F1-predicted_aligned_error_v6.png","plddt_mean":89.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LHFPL5","jax_strain_url":"https://www.jax.org/strain/search?query=LHFPL5"},"sequence":{"accession":"Q8TAF8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8TAF8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8TAF8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TAF8"}},"corpus_meta":[{"pmid":"23217710","id":"PMC_23217710","title":"TMHS 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LHFPL5.","date":"2018","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/30070639","citation_count":65,"is_preprint":false},{"pmid":"16752389","id":"PMC_16752389","title":"Mutations in the lipoma HMGIC fusion partner-like 5 (LHFPL5) gene cause autosomal recessive nonsyndromic hearing loss.","date":"2006","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/16752389","citation_count":54,"is_preprint":false},{"pmid":"33168709","id":"PMC_33168709","title":"Deafness mutation D572N of TMC1 destabilizes TMC1 expression by disrupting LHFPL5 binding.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/33168709","citation_count":29,"is_preprint":false},{"pmid":"29069081","id":"PMC_29069081","title":"Spatiotemporal changes in the distribution of LHFPL5 in mice cochlear hair bundles during development and in the absence of PCDH15.","date":"2017","source":"PloS 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protocadherin-15-LHFPL5 tip link complex is a heterotetrameric assembly in hair cell stereocilia.","date":"2026","source":"Biophysical journal","url":"https://pubmed.ncbi.nlm.nih.gov/41668373","citation_count":0,"is_preprint":false},{"pmid":"41187086","id":"PMC_41187086","title":"LHFPL5 is required for maximal activation of the mechanotransduction channel in cochlear hair cells.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/41187086","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.05.24.595729","title":"Molecular Specializations Underlying Phenotypic Differences in Inner Ear Hair Cells of Zebrafish and Mice","date":"2024-05-26","source":"bioRxiv","url":"https://doi.org/10.1101/2024.05.24.595729","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.25.678357","title":"The longer transmembrane helices of class I viral fusion proteins may facilitate viral fusion","date":"2025-09-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.25.678357","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.05.28.596144","title":"Cotranslational membrane insertion of the voltage-sensitive K<sup>+</sup>channel KvAP","date":"2024-05-29","source":"bioRxiv","url":"https://doi.org/10.1101/2024.05.28.596144","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.05.24.24307866","title":"Tolerability of Long-acting Diquafosol Ophthalmic Solution as per Tear Film and Meibomian Glands Findings","date":"2024-05-25","source":"bioRxiv","url":"https://doi.org/10.1101/2024.05.24.24307866","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13855,"output_tokens":3370,"usd":0.046058},"stage2":{"model":"claude-opus-4-6","input_tokens":6758,"output_tokens":2772,"usd":0.154635},"total_usd":0.200693,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"TMHS (LHFPL5) is a tetraspan transmembrane protein localized to the apical membrane and hair bundles of inner ear hair cells; loss-of-function (missense C→F substitution) causes disorganized hair bundles, progressive hair cell loss, deafness, and vestibular dysfunction in mice, establishing its role in hair bundle morphogenesis/stereocilia development.\",\n      \"method\": \"Positional cloning, immunofluorescence with specific polyclonal antibodies, scanning electron microscopy of cochleae from Tmhs mutant (hscy) mice\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO/mutant with specific cellular phenotype, direct localization by immunofluorescence, replicated in subsequent studies\",\n      \"pmids\": [\"15905332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Targeted null mutation of Tmhs (LHFPL5) phenocopies the hscy missense mutation, confirming that loss of LHFPL5 alone causes deafness and vestibular dysfunction; lacZ reporter shows expression peaks around P0 and is absent by P15, consistent with a role in stereocilia development.\",\n      \"method\": \"Targeted gene knockout (Tmhs tm1Kjn), lacZ reporter driven by Tmhs promoter, beta-galactosidase activity visualization, auditory/vestibular phenotyping\",\n      \"journal\": \"Mammalian genome : official journal of the International Mammalian Genome Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined phenotype and reporter-based temporal expression analysis, confirming previous findings\",\n      \"pmids\": [\"17876667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TMHS (LHFPL5) physically binds to the tip-link component PCDH15, regulates tip-link assembly, controls transducer channel conductance, and is required for fast channel adaptation; it functions as an integral component of the hair cell mechanotransduction machinery analogous to TARP subunits of AMPA receptors.\",\n      \"method\": \"Co-immunoprecipitation, electrophysiology (mechanotransduction recordings), genetic knockout mice (Tmhs-/-), immunofluorescence, deafness mutation analysis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reciprocal Co-IP, electrophysiology, KO mice with multiple orthogonal readouts; highly cited foundational study replicated by later work\",\n      \"pmids\": [\"23217710\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"LHFPL5 localization to stereocilia tips requires PCDH15; in PCDH15-deficient mice, LHFPL5 fails to reach tips and instead distributes to unranked stereocilia and lower lateral links. LHFPL5 is present in the MET apparatus as early as P0 and shows higher expression in apical than basal bundles.\",\n      \"method\": \"Immunofluorescence and immunogold transmission electron microscopy in wild-type and PCDH15-deficient mice across developmental time points (P0–P21)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with genetic manipulation (PCDH15 KO) and functional consequence for tip localization, using immunogold EM\",\n      \"pmids\": [\"29069081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal/cryo structure of the PCDH15–LHFPL5 complex reveals a heterotetramer (two PCDH15 and two LHFPL5 subunits) with a 2-fold symmetric 'collar' near the membrane; LHFPL5 forms extensive interactions with PCDH15 transmembrane helices, stabilizing the overall assembly and placing deafness mutations at critical interfaces.\",\n      \"method\": \"X-ray crystallography and cryo-EM structural determination, analytical ultracentrifugation (AUC), biochemical reconstitution of PCDH15–LHFPL5 complex\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution structure with biochemical validation; single rigorous paper with multiple orthogonal structural and biophysical methods\",\n      \"pmids\": [\"30070639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TMC1 and LHFPL5 co-localize at the tips of shorter stereocilia rows in neonatal hair cells; in adult inner hair cells, LHFPL5 distributes uniformly across shorter stereocilia rows while TMC1 distributes to all rows, suggesting distinct regulation in mature cells.\",\n      \"method\": \"Immunofluorescence, super-resolution microscopy, fractionation/localization in neonatal and adult mouse cochlear hair cells\",\n      \"journal\": \"FASEB journal : official publication of the Federation of American Societies for Experimental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization with developmental comparison, single lab\",\n      \"pmids\": [\"30808210\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"LHFPL5 physically interacts with TMC1 and stabilizes TMC1 protein expression in both heterologous cells and native hair cells (soma and hair bundle); the semidominant deafness mutation D572N in human TMC1 (D569N in mouse) severely disrupts LHFPL5 binding and destabilizes TMC1.\",\n      \"method\": \"Single-molecule pulldown (SiMPull) assay, co-immunoprecipitation, heterologous expression systems, immunofluorescence in hair cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (SiMPull, Co-IP, native hair cell analysis) with mutagenesis functional validation\",\n      \"pmids\": [\"33168709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In zebrafish, Lhfpl5a/b localization at stereocilia tips requires tip-link cadherins Pcdh15a and Cdh23, as well as the Myo7aa motor protein; however, in contrast to mice, TMC1/TMC2b localization to stereocilia does not depend on Lhfpl5, revealing species-specific differences in MET complex assembly.\",\n      \"method\": \"Genetic mutant analysis (lhfpl5a/b knockout zebrafish), GFP-tagged transgene localization, hair cell electrophysiology (mechanotransduction recordings), FM dye uptake\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with GFP reporter, electrophysiology, and multiple mutant backgrounds\",\n      \"pmids\": [\"32009898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"An extracellular loop 1 region of LHFPL5 (which interacts with PCDH15) contains sequences that preclude trafficking to the plasma membrane in heterologous cells; PCDH15 co-expression is required to mask ER retention signals or enable proper folding and trafficking of LHFPL5 to the plasma membrane.\",\n      \"method\": \"Aquaporin 3-tGFP plasma membrane reporter (AGR) assay, domain deletion and chimeric LHFPL5 constructs in heterologous cell lines, immunofluorescence\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with reporter construct and domain mapping; single lab\",\n      \"pmids\": [\"36781873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LHFPL5 directly couples the PCDH15 tip link to the TMC1 MET channel via its N-terminal cytoplasmic domain, which binds an amphipathic helix in TMC1 that is a conserved gating domain; mutations in either the LHFPL5 N-terminus or the TMC1 amphipathic helix that disrupt this interaction reduce channel responses to mechanical force, supporting a tether model for MET channel gating.\",\n      \"method\": \"Co-immunoprecipitation, electrophysiology (MET channel recordings), site-directed mutagenesis of LHFPL5 N-terminal domain and TMC1 amphipathic helix, mouse knockout/knock-in models\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mutagenesis, Co-IP, and electrophysiology with multiple mutant combinations; rigorous mechanistic study\",\n      \"pmids\": [\"36917610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"LHFPL5 is a principal component of the gating spring that transmits tip-link tension to the MET channel: in Lhfpl5-/- outer hair cells, the MET working range more than doubles and single-channel gating force (Z) decreases by >60%, while gating stiffness (inferred from stiffness change upon tip-link destruction) is virtually abolished. The Tmc1 D569N mutation reduces LHFPL5 immunolabeling in stereocilia and similarly doubles the MET working range.\",\n      \"method\": \"Electrophysiology (MET channel recordings in Lhfpl5-/- and Lhfpl5+/- mice), hair bundle stiffness measurements, immunofluorescence\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — quantitative electrophysiology with defined KO/heterozygote comparison, stiffness measurements, and mutagenesis; strong mechanistic evidence\",\n      \"pmids\": [\"38194445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"An LHFPL5 mutant lacking just three N-terminal amino acids causes recessive deafness and severely impairs MET channel activation; resting open probability is increased but unitary conductance, adaptation, and tonotopic properties are normal, and MET channel proteins remain in stereocilia at normal levels. This establishes that the LHFPL5 N-terminus is specifically required for maximal mechanical activation of MET channels without affecting channel assembly or adaptation.\",\n      \"method\": \"Knock-in mouse expressing N-terminal LHFPL5 deletion mutant, electrophysiology (MET recordings), immunofluorescence for MET channel components in stereocilia\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — targeted knock-in mutagenesis with electrophysiology and localization controls, dissecting distinct functional domains\",\n      \"pmids\": [\"41187086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Single-molecule pulldown (SiMPull) and single-molecule array (SiMoA) assays applied to native mouse cochlea and utricle establish that the PCDH15–LHFPL5 complex is a heterotetrameric assembly (two PCDH15 and two LHFPL5 subunits), confirming the stoichiometry of the tip-link complex in native tissue.\",\n      \"method\": \"Single-molecule pulldown (SiMPull), single-molecule array (SiMoA) with native protein from mouse cochlea and utricle\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — single-molecule stoichiometry assays on native tissue, orthogonal to prior structural data\",\n      \"pmids\": [\"41668373\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LHFPL5 (TMHS) is an integral tetraspan auxiliary subunit of the hair cell mechano-electrical transduction (MET) channel complex that directly binds PCDH15 (tip-link component) via its extracellular loop and TMC1 (pore-forming channel subunit) via its N-terminal cytoplasmic domain, thereby coupling tip-link tension to channel gating as a principal component of the gating spring, stabilizing TMC1 expression, and enabling maximal force sensitivity and fast adaptation of the MET channel.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"LHFPL5 (also known as TMHS) is a tetraspan transmembrane auxiliary subunit of the hair cell mechano-electrical transduction (MET) channel complex that physically couples tip-link tension to channel gating in auditory and vestibular sensory cells. LHFPL5 forms a heterotetrameric assembly with PCDH15 (two LHFPL5 and two PCDH15 subunits) through extensive transmembrane and extracellular loop interactions, requiring PCDH15 for proper trafficking to stereocilia tips and plasma membrane insertion [PMID:30070639, PMID:29069081, PMID:36781873, PMID:41668373]. Its N-terminal cytoplasmic domain binds a conserved amphipathic helix in TMC1, the pore-forming channel subunit, stabilizing TMC1 expression and directly transmitting mechanical force to the channel gate; disruption of this interface by point mutations or small N-terminal deletions causes deafness with severely impaired MET activation while leaving channel assembly and adaptation intact [PMID:36917610, PMID:33168709, PMID:41187086]. Loss of LHFPL5 virtually abolishes gating-spring stiffness and reduces single-channel gating force by more than 60%, establishing LHFPL5 as a principal component of the gating spring that sets the force sensitivity and working range of mechanotransduction [PMID:38194445, PMID:15905332].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of LHFPL5 as a hair-bundle protein whose loss causes deafness established the first genetic link between this tetraspan protein family and inner ear mechanosensory function.\",\n      \"evidence\": \"Positional cloning of the hscy mouse mutant, immunofluorescence localization to hair bundles, and scanning electron microscopy showing disorganized stereocilia\",\n      \"pmids\": [\"15905332\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular partners within the MET complex unknown\", \"Whether LHFPL5 is required for mechanotransduction per se versus hair bundle development unclear\", \"No biochemical interaction data\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"A targeted null allele phenocopied the original missense mutation, confirming that LHFPL5 loss alone is sufficient for deafness and revealing a developmental expression window peaking near birth.\",\n      \"evidence\": \"Tmhs knockout mice with lacZ reporter and auditory/vestibular phenotyping\",\n      \"pmids\": [\"17876667\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of action at the molecular level still unknown\", \"Relationship to MET channel components not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstration that LHFPL5 physically binds PCDH15, regulates transducer channel conductance, and is required for fast adaptation established it as an integral auxiliary subunit of the MET channel, analogous to TARPs for AMPA receptors.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, mechanotransduction electrophysiology in Tmhs-/- mice, immunofluorescence\",\n      \"pmids\": [\"23217710\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PCDH15–LHFPL5 interaction unknown\", \"Whether LHFPL5 directly contacts the pore-forming subunit TMC1 not tested\", \"Stoichiometry of the complex undetermined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Establishing that PCDH15 is required for LHFPL5 localization to stereocilia tips resolved the epistatic hierarchy of MET complex assembly, placing tip-link formation upstream of LHFPL5 recruitment.\",\n      \"evidence\": \"Immunogold electron microscopy and immunofluorescence in PCDH15-deficient and wild-type mice across developmental stages\",\n      \"pmids\": [\"29069081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LHFPL5 mislocalization alone explains MET loss or additional functions are disrupted\", \"Mechanism by which PCDH15 enables LHFPL5 trafficking unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Solving the crystal/cryo-EM structure of the PCDH15–LHFPL5 complex revealed a heterotetrameric architecture with deafness mutations mapping to the interface, providing the first atomic framework for understanding how the tip link couples to the channel.\",\n      \"evidence\": \"X-ray crystallography, cryo-EM, and analytical ultracentrifugation of reconstituted PCDH15–LHFPL5 complex\",\n      \"pmids\": [\"30070639\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the full MET complex including TMC1 lacking\", \"Conformational changes during gating not captured\", \"Native stoichiometry not confirmed in vivo\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Discovery that LHFPL5 directly binds and stabilizes TMC1 protein expression — and that the human deafness mutation TMC1-D572N disrupts this interaction — identified LHFPL5 as the physical link between the tip link and the channel pore.\",\n      \"evidence\": \"Single-molecule pulldown, co-immunoprecipitation, heterologous expression, and immunofluorescence in native hair cells; combined with zebrafish epistasis showing species-specific assembly differences\",\n      \"pmids\": [\"33168709\", \"32009898\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding interface between LHFPL5 and TMC1 not mapped at residue level\", \"Whether LHFPL5 also contacts TMC2 with similar affinity unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Mapping the LHFPL5 N-terminal domain as the TMC1-binding element that couples to a conserved gating helix in TMC1, combined with the finding that PCDH15 is required to mask ER-retention signals in LHFPL5, defined the molecular logic of the tripartite PCDH15–LHFPL5–TMC1 force-transmission pathway.\",\n      \"evidence\": \"Site-directed mutagenesis of LHFPL5 N-terminus and TMC1 amphipathic helix with Co-IP and MET electrophysiology in knock-in mice; AGR trafficking assay with chimeric LHFPL5 constructs in heterologous cells\",\n      \"pmids\": [\"36917610\", \"36781873\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural model of the LHFPL5–TMC1 interface lacking\", \"Trafficking mechanism in native hair cells not directly tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Quantitative biophysical measurements in Lhfpl5-/- hair cells revealed that LHFPL5 contributes the majority of gating-spring stiffness and sets single-channel gating force, establishing it as the principal gating-spring element rather than merely an auxiliary subunit.\",\n      \"evidence\": \"Hair bundle stiffness measurements and MET channel electrophysiology in Lhfpl5-/- and Lhfpl5+/- outer hair cells; comparison with Tmc1-D569N mutant\",\n      \"pmids\": [\"38194445\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LHFPL5 contributes elasticity intrinsically or via organizing other elements unclear\", \"No direct measurement of LHFPL5 mechanical compliance\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A three-amino-acid N-terminal deletion knock-in cleanly separated LHFPL5's force-transmission role from its channel-assembly function, showing that the N-terminus is specifically required for maximal MET activation but dispensable for channel localization and adaptation.\",\n      \"evidence\": \"Knock-in mouse with minimal N-terminal LHFPL5 deletion, MET electrophysiology, immunofluorescence for MET complex components\",\n      \"pmids\": [\"41187086\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether these three residues directly contact TMC1 amphipathic helix not resolved structurally\", \"Contribution of individual residues not dissected\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Single-molecule assays on native cochlear and utricular tissue confirmed the 2:2 PCDH15:LHFPL5 heterotetrameric stoichiometry in vivo, validating the structural model in a physiological context.\",\n      \"evidence\": \"SiMPull and SiMoA applied to native mouse cochlea and utricle protein\",\n      \"pmids\": [\"41668373\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full stoichiometry of the complete MET complex (including TMC1/2) in native tissue remains undetermined\", \"Whether stoichiometry differs between vestibular and auditory hair cell types not explored\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of the complete PCDH15–LHFPL5–TMC1 ternary complex and direct measurements of LHFPL5's intrinsic mechanical compliance are needed to explain how this protein generates or transmits gating-spring stiffness at the molecular level.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No ternary complex structure available\", \"Intrinsic elasticity of LHFPL5 not measured\", \"Whether LHFPL5 interacts with TMC2 in the same manner is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [4, 10, 11]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 6, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3, 5, 8]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 3, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [0, 2, 10, 11]}\n    ],\n    \"complexes\": [\n      \"PCDH15–LHFPL5 heterotetramer\",\n      \"MET channel complex (PCDH15–LHFPL5–TMC1)\"\n    ],\n    \"partners\": [\n      \"PCDH15\",\n      \"TMC1\",\n      \"CDH23\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}