{"gene":"TRPM1","run_date":"2026-04-28T21:43:00","timeline":{"discoveries":[{"year":2009,"finding":"TRPM1 is necessary for the depolarizing light response of retinal ON-bipolar cells and is a component of the cation channel that generates this response, as demonstrated by loss of the ERG b-wave and abolition of chemically simulated light responses in patch-clamp recordings from TRPM1-/- mice.","method":"ERG recordings, whole-cell patch-clamp in retinal slices, TRPM1-/- knockout mice, in situ hybridization, immunofluorescence confocal microscopy","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (electrophysiology, KO mouse, localization), replicated independently in same year","pmids":["19861548"],"is_preprint":false},{"year":2009,"finding":"TRPM1 long form (TRPM1-L) is localized to dendritic tips of ON bipolar cells colocalizing with mGluR6, functions as a constitutively active nonselective cation channel, and its activity is negatively regulated by Go in the mGluR6 cascade; TRPM1 null mice completely lose the photoresponse of ON BCs.","method":"Immunofluorescence localization, TRPM1-/- knockout mice, ERG, electrophysiology in TRPM1-L-expressing cells, Go regulation assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods, independent replication, mechanistic cascade defined","pmids":["19966281"],"is_preprint":false},{"year":2009,"finding":"TRPM1 forms ion channels in melanocytes; endogenous TRPM1 current in human neonatal epidermal melanocytes and mouse melanoma cells was abrogated by miRNA directed against TRPM1, and TRPM1 is predominantly found in intracellular vesicular structures with small plasma membrane currents.","method":"Electrophysiology (patch-clamp), miRNA knockdown, subcellular localization imaging","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 1-2 — direct electrophysiological measurement combined with specific knockdown","pmids":["19436059"],"is_preprint":false},{"year":2009,"finding":"TRPM1 knockdown in human melanocytes reduces intracellular Ca2+ and Ca2+ uptake, decreases tyrosinase activity and melanin pigment; p53 induction (by transfection or UVB) represses TRPM1 expression, demonstrating TRPM1's role in Ca2+ homeostasis and melanogenesis.","method":"Lentiviral shRNA knockdown, Ca2+ imaging/measurement, tyrosinase activity assay, p53 transfection, UVB irradiation","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with multiple cellular readouts in single lab","pmids":["19587221"],"is_preprint":false},{"year":2011,"finding":"TRPM1 forms a complex with nyctalopin in mouse retina (identified by proteomic search/Co-IP); nyctalopin also interacts with mGluR6; disruption of mGluR6 prevented targeting of TRPM1 to the postsynaptic compartment of ON-bipolar neurons, revealing a macromolecular signaling complex scaffolded by nyctalopin.","method":"Proteomic search, Co-immunoprecipitation, immunofluorescence, mGluR6-/- mice","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, proteomic identification, genetic validation with KO mouse","pmids":["21832182"],"is_preprint":false},{"year":2011,"finding":"TRPM1 is an ion-conducting plasma membrane channel inhibited by extracellular zinc ions at physiological concentrations; the zinc inhibition is due to a short stretch of seven amino acids unique to the pore region of TRPM1 but not TRPM3; unmodified TRPM1 and TRPM3 form functional heteromultimeric channels.","method":"Heterologous expression, patch-clamp electrophysiology, steroid activation, site-directed mutagenesis of pore region, TRPM1/TRPM3 heteromultimer reconstitution","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution, mutagenesis, and biophysical characterization","pmids":["21278253"],"is_preprint":false},{"year":2012,"finding":"G-protein-mediated inhibition of TRPM1 in ON-bipolar cells requires the Gβγ dimer, not Gαo: dialysis of Gβγ (but not Gαo) closed TRPM1 channels in retinal bipolar cells, melanocytes, and HEK293 cells; activation of an endogenous GPCR pathway releasing Gβγ without activating Go also closed TRPM1.","method":"Patch-clamp electrophysiology (intracellular dialysis of protein subunits), multiple cell types including native bipolar cells and heterologous systems","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — electrophysiology with direct protein dialysis, replicated in multiple cell types","pmids":["22586107"],"is_preprint":false},{"year":2011,"finding":"TRPM1 localized at the ultrastructural level to the tips of ON-bipolar cell dendrites invaginating cone pedicles and rod spherules in human retina; additionally TRPM1 immunoreactivity was found on synaptic ribbons of a subclass of rods, suggesting a dual function in the ON pathway.","method":"Electron microscopy immunohistochemistry, in situ hybridization, laser dissection microscopy/PCR","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 — direct ultrastructural localization with multiple methods","pmids":["21896854"],"is_preprint":false},{"year":2011,"finding":"Deletion of mGluR6 renders TRPM1 channels inactive in rod bipolar cells; mGluR6 null mice show hyperpolarized rod bipolar cells with reduced slope conductance and current noise; TRPM1 immunostaining at dendritic tips is greatly reduced without mGluR6, indicating mGluR6-dependent postsynaptic targeting of TRPM1.","method":"Whole-cell patch-clamp, capsaicin application, immunostaining in mGluR6-/- mice","journal":"Journal of neurophysiology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with electrophysiology and localization, mechanistic conclusion","pmids":["22131384"],"is_preprint":false},{"year":2011,"finding":"Autoantibodies in melanoma-associated retinopathy (MAR) target TRPM1 in retinal ON-bipolar cells; MAR sera stain TRPM1-transfected HEK cells and ON-bipolar cells in TRPM1+/+ but not TRPM1-/- retina; the autoantibody epitope is likely intracellular and antibodies can be internalized by retinal cells.","method":"Immunofluorescence on TRPM1-transfected HEK cells and TRPM1-/- mouse retina, Western blot, confocal colocalization","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — confirmed by TRPM1-KO negative control, Western blot, multiple patient sera","pmids":["21411639"],"is_preprint":false},{"year":2011,"finding":"TRPM1 current in rod bipolar cells is susceptible to voltage-independent inhibition by intracellular magnesium; PKCα activation (via DAG/OAG) relieves this Mg2+ inhibition and potentiates TRPM1 current specifically in rod but not cone ON-bipolar cells, dependent on PIP2 hydrolysis.","method":"Whole-cell patch-clamp, DAG analog (OAG) application, PKCα knockout mice, pharmacological inhibition, PIP2 hydrolysis manipulation","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 — electrophysiology with KO mice and pharmacological dissection, multiple orthogonal approaches","pmids":["21940450"],"is_preprint":false},{"year":2004,"finding":"TRPM1 expression in melanocytes and melanoma is regulated by the transcription factor MITF via a 654 bp upstream sequence containing four E boxes (including an M box); deletion analysis showed that two distal E boxes (E3 and E4) are required for MITF activation and constitutive activity in melanoma.","method":"Promoter-luciferase reporter assay, deletion analysis, Western blot","journal":"Melanoma research","confidence":"Medium","confidence_rationale":"Tier 2 — reporter assay with deletion mapping and protein analysis, single lab","pmids":["15577322"],"is_preprint":false},{"year":2013,"finding":"Human melanocytes express mGluR6, and mGluR6 signaling positively couples to TRPM1 in melanocytes (opposite to the negative coupling in retina); knockdown of TRPM1 or mGluR6 abolished L-AP4-induced Ca2+ influx; forced Gαo expression restored negative coupling; absence of Gαo explains the different coupling polarity in melanocytes versus retina.","method":"shRNA knockdown, Ca2+ imaging, patch-clamp electrophysiology, Gαo overexpression, pertussis toxin treatment","journal":"Pigment cell & melanoma research","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (KD, electrophysiology, overexpression, pharmacology), mechanistic dissection of coupling polarity","pmids":["23452348"],"is_preprint":false},{"year":2013,"finding":"Serum TRPM1 autoantibodies from MAR patients enter retinal ON-bipolar cells after intravitreal injection and attenuate the ERG b-wave in wild-type but not TRPM1-/- mice; the autoantibody epitope is within the amino-terminal cytoplasmic domain of TRPM1.","method":"Intravitreal injection of MAR IgG, ERG recording, immunofluorescence on TRPM1+/+ and TRPM1-/- retinas, TRPM1-transfected CHO cell labeling","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — in vivo functional assay with KO controls, epitope mapping","pmids":["23936334"],"is_preprint":false},{"year":2014,"finding":"Purified recombinant TRPM1 is mostly dimeric (not tetrameric) as determined by blue native gels, size exclusion chromatography, cross-linking, and cryo-EM single-particle analysis; native retinal TRPM1 exists in two complexes of distinct sizes, suggesting additional partner subunits participate in the functional transduction channel.","method":"Recombinant protein purification from insect cells, blue native PAGE, size exclusion chromatography, cross-linking, cryo-EM single-particle analysis, antibody-TRPM1 complex EM","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 — purification and structural analysis by multiple methods, but interpretation (dimeric vs tetrameric) was provisional","pmids":["25112866"],"is_preprint":false},{"year":2015,"finding":"LRIT3 is essential for localizing TRPM1 to the dendritic tips of depolarizing bipolar cells; in Lrit3-/- mice, TRPM1 staining is severely decreased at dendritic tips of all depolarizing bipolar cells.","method":"Immunofluorescence confocal microscopy in Lrit3-/- mice versus wild-type","journal":"The European journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with direct localization readout, single lab","pmids":["25997951"],"is_preprint":false},{"year":2016,"finding":"Both the α (Gαo) and βγ (Gβγ) subunits of Go gate TRPM1 in ON-bipolar cells: a constitutively active Gαo mutant closed TRPM1 channels after light activation; phosducin or inactive Gαo (sequestering Gβγ) opened channels in darkness; Co-IP showed TRPM1 interacts with Gβ3 and both active and inactive Gαo; BRET assays showed Gαo interacts with both N- and C-termini of TRPM1 while Gβγ interacts only with the N-terminus.","method":"Intracellular dialysis patch-clamp in rod bipolar cells, Co-immunoprecipitation, bioluminescent energy transfer (BRET)","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (electrophysiology, Co-IP, BRET), mechanistic dissection of subunit binding sites","pmids":["26883481"],"is_preprint":false},{"year":2015,"finding":"Voriconazole inhibits TRPM1 channels in retinal ON-bipolar cells; patch-clamp recording showed voriconazole blocks capsaicin-activated TRPM1 currents in ON-bipolar cells and TRPM3 currents in transfected CHO cells, while only slightly inhibiting mGluR6-mediated GIRK currents.","method":"ERG recordings, whole-cell patch-clamp in retinal slices and transfected CHO cells","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 1-2 — direct electrophysiology in native and heterologous cells with pharmacological dissection","pmids":["25650413"],"is_preprint":false},{"year":2015,"finding":"PIP2 binds to an N-terminal fragment of TRPM1 (residues A451-N566); the basic residue K464 is part of a putative pleckstrin homology domain involved in PIP2 interaction, characterized by biophysical methods and molecular modeling.","method":"Biophysical binding assays, molecular modeling, mutagenesis of K464","journal":"Biophysical chemistry","confidence":"Low","confidence_rationale":"Tier 3 — in vitro binding with N-terminal fragment only, no functional channel validation","pmids":["26544986"],"is_preprint":false},{"year":2016,"finding":"S100A1 binds to the N-terminal L242-E344 region of TRPM1 in a calcium-dependent manner; complex formation requires clusters of positively charged (K271, R273, R274) and hydrophobic (L263, V270, L276) residues, characterized by fluorescence spectroscopy and mutagenesis.","method":"Fluorescence spectroscopy, bioinformatics/structural modeling, mutagenesis","journal":"The international journal of biochemistry & cell biology","confidence":"Low","confidence_rationale":"Tier 3 — in vitro binding characterization with fragment, no functional channel assay","pmids":["27435061"],"is_preprint":false},{"year":2018,"finding":"The majority of TRPM1 in retinal ON-bipolar cells resides in the endoplasmic reticulum (ER), not at the plasma membrane; in heterologous cells, recombinant TRPM1 colocalizes with ER markers; fluorescence protease protection assays showed both N and C termini are cytoplasmic, consistent with TRPM channel topology; the ER extends into axons and dendrites but not dendritic tips.","method":"Immunofluorescence colocalization with ER markers, fluorescence protease protection (FPP) assay, live imaging of ER-fluorescent marker in bipolar cells","journal":"eNeuro","confidence":"Medium","confidence_rationale":"Tier 2 — multiple localization methods in both native and heterologous cells, topology confirmed by FPP","pmids":["30027108"],"is_preprint":false},{"year":2019,"finding":"LRIT3 is expressed presynaptically in rod photoreceptors; restoring LRIT3 expression in Lrit3-/- rods (not DBCs) rescues assembly of the postsynaptic glutamate signalplex (including TRPM1) and rod-driven vision, demonstrating that LRIT3 acts as a transsynaptic organizer of the postsynaptic complex containing TRPM1.","method":"Cell-type-specific LRIT3 rescue by AAV in Lrit3-/- mice, immunofluorescence, ERG","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — genetic rescue experiment with cell-type specificity, functional and structural readouts","pmids":["31189098"],"is_preprint":false},{"year":2012,"finding":"A point mutation in the pore domain of TRPM1 (p.A1068T) causes dominant negative inhibition of TRPM1 channel function; heterozygous Trpm1+/tvrm27 mice show reduced b-wave amplitudes and reduced DBC responses to LY341495 or capsaicin, indicating that the number of functional TRPM1 channels at DBC dendritic tips determines DBC response amplitude.","method":"Chemical mutagenesis screen, genetic complementation, ERG, whole-cell patch-clamp, immunofluorescence","journal":"Journal of neurophysiology","confidence":"High","confidence_rationale":"Tier 1-2 — pore domain mutation with multiple functional readouts, dominant negative mechanism established","pmids":["22896717"],"is_preprint":false},{"year":2017,"finding":"TRPM1 channel opening is required for rod bipolar cell development and synapse formation with AII amacrine cells: TRPM1-/- mice show contracted rod bipolar terminals, fewer synapses with amacrine cells, and reduced AII amacrine cell dendritic complexity; activated Gαo interacts with TRPM1 and induces contraction of rod bipolar terminals; Channelrhodopsin-2 overexpression partially rescues rod bipolar cell development in TRPM1-/- retina.","method":"TRPM1-/- KO mice, immunohistochemistry, morphometric analysis, Co-IP (Gαo-TRPM1), Channelrhodopsin-2 rescue, constitutively closed TRPM1 construct","journal":"The Journal of neuroscience : the official journal of the Society for Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — KO phenotype with multiple readouts, rescue experiments, and protein interaction data","pmids":["28899920"],"is_preprint":false},{"year":2011,"finding":"TRPM1 current desensitization in ON-bipolar cells depends on the strength of presynaptic stimulus; stimuli activating >20% of maximum TRPM1 current cause desensitization that reduces response to ~40% of peak (time constant ~1 s), with slow recovery (>20 s); TRPM1 desensitization augments the sustained component of downstream ganglion cell EPSCs.","method":"Whole-cell patch-clamp of ON-bipolar cells and ganglion cells in retinal slices, dye-filling/morphology","journal":"The Journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 — direct electrophysiology in native cells, single lab","pmids":["22041187"],"is_preprint":false},{"year":2010,"finding":"TRPM1 is the endpoint of the mGluR6 signal transduction cascade; reconstitution in CHO cells expressing TRPM1, mGluR6, and Gαo demonstrated that TRPM1 is negatively regulated by the mGluR6/Go cascade.","method":"Reconstitution in CHO cells expressing TRPM1, mGluR6, and Gαo; electrophysiology","journal":"Handbook of experimental pharmacology","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution of the signaling cascade","pmids":["24756714"],"is_preprint":false},{"year":2022,"finding":"TRPM1 promotes acral melanoma progression via Ca2+/CaMKIIδ/AKT pathway: TRPM1 elevates cytosolic Ca2+, activates CaMKIIδ, promotes CaMKIIδ/AKT interaction and AKT activation; CaMKII inhibitor (KN93) suppressed TRPM1-driven melanoma cell growth in vitro and in vivo xenograft models.","method":"Loss-of-function and gain-of-function (KD/OE), Ca2+ measurement, Western blot for CaMKIIδ/AKT phosphorylation, Co-IP, colony formation, migration/invasion assay, xenograft mouse model","journal":"Journal of advanced research","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods including in vivo validation, single lab","pmids":["36585114"],"is_preprint":false},{"year":2021,"finding":"TRPM1 is a client of the HSP90 chaperone; AUY922 (HSP90 inhibitor) reduces TRPM1 expression by disrupting the CDC37-HSP90 chaperone complex, as demonstrated by co-immunoprecipitation of TRPM1 with HSP90.","method":"Co-immunoprecipitation, proteomic profiling (iTRAQ), Western blot, loss/gain-of-function assays","journal":"Journal of biomedical science","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP plus functional consequence, single lab","pmids":["34301262"],"is_preprint":false},{"year":2016,"finding":"TRPM1 channels are expressed in the lateral amygdala and contribute to capsaicin-induced LTD in the amygdala; using TRPM1-/- mice and pharmacology, capsaicin-induced LTD was absent in TRPM1-/- lateral amygdala; this effect requires group I mGluRs, TRPC5 interaction, and intact GABAergic transmission.","method":"Electrophysiology (LTD recordings), TRPM1-/- mice, pharmacological blockers, TRPV1-/- mice","journal":"Neurobiology of learning and memory","confidence":"Medium","confidence_rationale":"Tier 2 — KO mice with electrophysiology and pharmacological dissection","pmids":["27633915"],"is_preprint":false},{"year":2013,"finding":"Anti-TRPM1 antibodies in MAR patient serum cause acute degeneration and apoptosis of retinal ON-bipolar cells in wild-type but not TRPM1-/- mice after intravitreal injection, with reduced ERG amplitudes persisting at 3 months.","method":"Intravitreal injection, ERG, immunohistochemistry, TUNEL staining, TRPM1-/- controls","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — in vivo functional assay with KO negative controls, multiple histological and physiological readouts","pmids":["24282602"],"is_preprint":false},{"year":2026,"finding":"Cryo-EM structure of TRPM1 reveals a canonical tetrameric fold in the intracellular domain but an inverted transmembrane domain with opposite handedness compared to other related channels; the VSLD and pore domain are arranged domain-swapped but with clockwise geometry, forming a large pore-like structure; single-channel recordings show constitutive activity.","method":"Cryo-EM, single-particle analysis, single-channel electrophysiology","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure with functional validation (electrophysiology), two independent papers with same finding (PMID 41857038 and preprint 41757028)","pmids":["41857038"],"is_preprint":false},{"year":2026,"finding":"Cryo-EM structure of human TRPM1 in conducting state reveals tetrameric assembly with an unexpected clockwise domain-swapped pore module of inverted rotational geometry; this topology is accompanied by a dilated selectivity filter, expanded central cavity, and splayed S6 forming a wide intracellular gate; single-channel recordings confirm constitutive activity.","method":"Cryo-EM, single-channel patch-clamp electrophysiology","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure + functional electrophysiology; corroborated by independent structural study (PMID 41857038)","pmids":["41757028"],"is_preprint":true},{"year":2021,"finding":"TRPM1 has a functional role in iris sphincter muscle cells: Trpm1-/- mice show severely defective pupillary light reflex (PLR) and iris photomechanical response; light-driven iris constriction independent of brain signaling requires Trpm1 expression and is melanopsin-dependent; capsaicin-driven (pain afferent) iris constriction also requires Trpm1.","method":"In vivo PLR measurements in Trpm1-/- mice, isolated eye preparations, pharmacological (capsaicin, melanopsin antagonists)","journal":"Experimental eye research","confidence":"Medium","confidence_rationale":"Tier 2 — KO mice with functional readout in multiple experimental contexts, single lab","pmids":["34954202"],"is_preprint":false},{"year":2018,"finding":"Differential epitope masking by monoclonal antibodies reveals synapse-specific multiprotein complexes of TRPM1 at dendritic tips; antibodies recognizing an N-terminal region (N2d) near the transmembrane domain show reduced labeling at dendritic tips vs. cell bodies, suggesting formation of a synapse-specific complex that masks this epitope.","method":"Monoclonal antibody epitope mapping, immunofluorescence, quantitative immunoblotting of synaptosomes","journal":"Visual neuroscience","confidence":"Low","confidence_rationale":"Tier 3 — differential labeling pattern suggesting complex formation, no direct Co-IP of partner","pmids":["29370879"],"is_preprint":false},{"year":2017,"finding":"MAR autoantibodies recognize an epitope encoded by exons 9 and 10 of TRPM1 that is conserved with TRPM3; MAR sera cross-react with TRPM3 in the retinal pigment epithelium.","method":"Immunofluorescence and Western blot on HEK293 cells transfected with EGFP-TRPM1 deletion constructs, retinal section immunostaining","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2-3 — systematic epitope mapping with truncation constructs, single lab","pmids":["28549093"],"is_preprint":false}],"current_model":"TRPM1 is a constitutively active, Ca2+-permeable nonselective cation channel with an unusual inverted transmembrane domain topology (revealed by cryo-EM) that localizes to the dendritic tips of retinal ON-bipolar cells via a transsynaptic organizing complex involving LRIT3 (presynaptic), nyctalopin, and mGluR6; in darkness, glutamate-activated mGluR6 couples to the heterotrimeric G-protein Gαoβ3γ13, and both the Gβγ dimer and activated Gαo cooperate to close the channel, while light-induced reduction in glutamate release deactivates mGluR6, allowing constitutive TRPM1 opening and ON-bipolar cell depolarization; PKCα relieves Mg2+-dependent TRPM1 inhibition to modulate synaptic gain, and in melanocytes TRPM1 mediates Ca2+ influx that regulates pigmentation in a polarity-inverted (positively coupled) mGluR6-dependent manner compared to the retina."},"narrative":{"teleology":[{"year":2004,"claim":"MITF was identified as a direct transcriptional activator of TRPM1 in melanocytes, establishing how TRPM1 expression is coupled to the melanocyte differentiation program.","evidence":"Promoter-luciferase deletion analysis identified two E-box elements required for MITF-driven TRPM1 transcription in melanoma cells.","pmids":["15577322"],"confidence":"Medium","gaps":["No chromatin-level (ChIP) validation of MITF occupancy","Regulation in retinal ON-bipolar cells not addressed"]},{"year":2009,"claim":"Three independent studies established TRPM1 as the transduction channel of retinal ON-bipolar cells and a Ca²⁺-conducting channel in melanocytes, resolving the molecular identity of the ON pathway channel that had been sought for decades.","evidence":"TRPM1⁻/⁻ mice lacked ERG b-waves and ON-bipolar cell light responses; TRPM1 colocalized with mGluR6 at dendritic tips; constitutive channel activity was demonstrated in heterologous cells and inhibited by Gαo; TRPM1 current was recorded in melanocytes and abolished by miRNA knockdown [PMID:19861548, PMID:19966281, PMID:19436059].","pmids":["19861548","19966281","19436059","19587221"],"confidence":"High","gaps":["Gating mechanism (Gα vs Gβγ) unresolved","Subunit stoichiometry unknown","Mechanism of dendritic tip targeting unclear"]},{"year":2011,"claim":"A macromolecular signaling complex was defined at ON-bipolar cell dendritic tips: nyctalopin scaffolds TRPM1 and mGluR6, mGluR6 is required for TRPM1 trafficking to dendritic tips, and PKCα modulates TRPM1 by relieving Mg²⁺-dependent inhibition—establishing the postsynaptic architecture and a gain-control mechanism.","evidence":"Proteomic/Co-IP identified nyctalopin–TRPM1 and nyctalopin–mGluR6 complexes; mGluR6⁻/⁻ mice showed loss of TRPM1 dendritic tip localization and inactive channels; PKCα activation via DAG relieved intracellular Mg²⁺ block of TRPM1 current in rod bipolar cells [PMID:21832182, PMID:22131384, PMID:21940450].","pmids":["21832182","22131384","21940450"],"confidence":"High","gaps":["Direct binding interface between nyctalopin and TRPM1 not mapped","Mechanism by which PKCα relieves Mg²⁺ block at the channel level unknown"]},{"year":2011,"claim":"TRPM1 was identified as the autoantigen in melanoma-associated retinopathy (MAR), and its biophysical properties—including zinc inhibition and pore-region determinants—were characterized, establishing a disease mechanism and channel pharmacology.","evidence":"MAR sera specifically labeled TRPM1-transfected cells and WT but not TRPM1⁻/⁻ retina; extracellular zinc inhibited TRPM1 via a 7-amino-acid pore sequence; TRPM1/TRPM3 heteromultimeric channels were reconstituted [PMID:21411639, PMID:21278253].","pmids":["21411639","21278253"],"confidence":"High","gaps":["Mechanism of autoantibody internalization into bipolar cells not resolved","Physiological relevance of zinc modulation in vivo unclear"]},{"year":2012,"claim":"Gβγ was identified as the direct inhibitory subunit that closes TRPM1, and a pore-domain dominant-negative mutation (A1068T) showed that the number of functional channel complexes at dendritic tips determines ON-bipolar cell response amplitude.","evidence":"Dialysis of purified Gβγ (but not Gαo) closed TRPM1 in bipolar cells, melanocytes, and HEK293 cells; heterozygous Trpm1-A1068T mice had reduced b-waves proportional to loss of functional channels [PMID:22586107, PMID:22896717].","pmids":["22586107","22896717"],"confidence":"High","gaps":["Binding site of Gβγ on TRPM1 not structurally resolved","Whether A1068T disrupts pore gating or assembly not distinguished"]},{"year":2013,"claim":"The coupling polarity between mGluR6 and TRPM1 was shown to be cell-type-dependent: negative in retina (via Gαo) and positive in melanocytes (which lack Gαo), explaining how the same receptor–channel pair produces opposite functional outcomes in different tissues.","evidence":"Knockdown of TRPM1 or mGluR6 in melanocytes abolished L-AP4-induced Ca²⁺ influx; forced Gαo expression in melanocytes restored negative coupling as seen in retina [PMID:23452348].","pmids":["23452348"],"confidence":"High","gaps":["Identity of the G-protein subunit mediating positive coupling in melanocytes not established","Whether additional signaling intermediaries participate is unknown"]},{"year":2013,"claim":"MAR autoantibodies were shown to be pathogenic in vivo: intravitreal injection caused ON-bipolar cell apoptosis and persistent ERG b-wave reduction, dependent on TRPM1 expression, establishing a direct autoimmune mechanism.","evidence":"Purified MAR IgG injected intravitreally reduced b-wave and caused TUNEL-positive bipolar cell death in WT but not TRPM1⁻/⁻ mice [PMID:24282602, PMID:23936334].","pmids":["24282602","23936334"],"confidence":"High","gaps":["Mechanism of antibody-induced cell death (channel block vs complement vs signaling) not determined"]},{"year":2016,"claim":"The initial model of Gβγ-only gating was revised: both Gαo and Gβγ cooperate to close TRPM1, with BRET mapping showing Gαo binds both N- and C-termini while Gβγ binds only the N-terminus, providing a dual-subunit gating model.","evidence":"Constitutively active Gαo closed TRPM1 after light activation; phosducin (sequestering Gβγ) opened channels in darkness; BRET and Co-IP mapped subunit-specific interaction domains [PMID:26883481].","pmids":["26883481"],"confidence":"High","gaps":["Structural basis of dual-subunit gating not resolved","Relative contribution of each subunit to gating kinetics unknown"]},{"year":2017,"claim":"TRPM1 channel activity was shown to be required for postnatal rod bipolar cell development and synaptogenesis with AII amacrine cells, extending TRPM1's role beyond signal transduction to circuit maturation.","evidence":"TRPM1⁻/⁻ mice had contracted rod bipolar terminals and fewer synapses; Channelrhodopsin-2 overexpression partially rescued development [PMID:28899920].","pmids":["28899920"],"confidence":"High","gaps":["Whether the developmental role reflects Ca²⁺ signaling or depolarization per se is unresolved","Downstream transcriptional programs not identified"]},{"year":2019,"claim":"LRIT3 was revealed to act as a presynaptic transsynaptic organizer that directs postsynaptic assembly of the TRPM1-containing signalplex, resolving how the dendritic tip complex is organized across the synapse.","evidence":"AAV-mediated LRIT3 restoration specifically in Lrit3⁻/⁻ rods (not bipolar cells) rescued TRPM1 localization and rod-driven ERG responses [PMID:31189098].","pmids":["31189098"],"confidence":"High","gaps":["Postsynaptic receptor for LRIT3 not identified","Whether LRIT3 directly contacts TRPM1 or acts via nyctalopin/mGluR6 is unresolved"]},{"year":2026,"claim":"The cryo-EM structure of TRPM1 revealed an unprecedented inverted transmembrane topology with clockwise domain-swapped pore modules, a dilated selectivity filter, and a wide intracellular gate, providing a structural basis for constitutive activity and distinguishing TRPM1 from all other structurally characterized TRP channels.","evidence":"Two independent cryo-EM studies resolved the TRPM1 tetramer, confirmed by single-channel electrophysiology showing constitutive openings [PMID:41857038].","pmids":["41857038"],"confidence":"High","gaps":["Structure of TRPM1 in complex with Gαo or Gβγ not determined","Mechanism by which G-protein binding induces channel closure not structurally resolved","No structure with nyctalopin or mGluR6 complex partners"]},{"year":null,"claim":"Key unresolved questions include: the structural basis of G-protein–mediated channel closure, the identity of the postsynaptic receptor for presynaptic LRIT3, the mechanism by which MAR autoantibodies cause bipolar cell death, and whether TRPM1's role in extra-retinal tissues (amygdala, iris) involves the same signaling complex as in ON-bipolar cells.","evidence":"","pmids":[],"confidence":"Low","gaps":["No TRPM1–G-protein co-structure available","Transsynaptic binding partner of LRIT3 on the postsynaptic side unidentified","Pathogenic mechanism of MAR autoantibodies at the molecular level unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,2,5,6,22,30,31]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,5,7,22]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[20]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,1,6,16,23,28]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,6,12,16,25]},{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[0,1,7,8,22,32]}],"complexes":["mGluR6-TRPM1-nyctalopin signalplex","TRPM1-Gαo-Gβ3γ13 complex"],"partners":["GRM6","NYX","LRIT3","GNAO1","GNB3","PRKCA","TRPM3","S100A1"],"other_free_text":[]},"mechanistic_narrative":"TRPM1 is a constitutively active, Ca²⁺-permeable nonselective cation channel that serves as the transduction channel in retinal ON-bipolar cells and regulates Ca²⁺-dependent melanogenesis in melanocytes. In ON-bipolar cells, TRPM1 localizes to dendritic tips via a transsynaptic organizing complex requiring presynaptic LRIT3, postsynaptic nyctalopin, and mGluR6; the mGluR6/Gαo cascade closes the channel in darkness through cooperative action of both Gβγ and Gαo subunits, while light-evoked glutamate reduction permits constitutive channel opening and cell depolarization [PMID:19861548, PMID:22586107, PMID:26883481, PMID:31189098]. Cryo-EM reveals a tetrameric architecture with an unprecedented inverted transmembrane domain topology—clockwise domain-swapped pore modules with a dilated selectivity filter and wide intracellular gate—consistent with its constitutive open state [PMID:41857038]. In melanocytes, TRPM1 mediates Ca²⁺ influx coupled positively (rather than negatively) to mGluR6 owing to the absence of Gαo, thereby promoting tyrosinase activity and melanin synthesis; TRPM1 is also the autoantigen in melanoma-associated retinopathy, where patient autoantibodies enter ON-bipolar cells and cause functional impairment and degeneration [PMID:23452348, PMID:21411639, PMID:24282602]."},"prefetch_data":{"uniprot":{"accession":"Q7Z4N2","full_name":"Transient receptor potential cation channel subfamily M member 1","aliases":["Long transient receptor potential channel 1","LTrpC1","Melastatin-1"],"length_aa":1603,"mass_kda":182.2,"function":"Constitutively open nonselective divalent cation-conducting channels which mediate the influx of Ca(2+), Mg(2+), Mn(2+), Ba(2+), and Ni(2+) into the cytoplasm, leading to membrane depolarization (PubMed:11535825, PubMed:19436059, PubMed:21278253). Impermeable to zinc ions (PubMed:21278253). In addition, forms heteromultimeric ion channels with TRPM3 which are permeable for calcium and zinc ions (PubMed:21278253). Plays an essential role for the depolarizing photoresponse of retinal ON bipolar cells (PubMed:19878917, PubMed:19896109). In the dark, tonic release of glutamate activates the G-protein coupled receptor for glutamate, GRM6, its activation induces the release of G(o) protein and the beta-gamma G protein dimer. Both subunits can interact and inactivate the TRPM1 channel. A light onset, induces decrease in glutamate release and deactivation of GRM6 leading to channel opening and membrane depolarization (By similarity). May play a role in metastasis suppression (PubMed:9537257)","subcellular_location":"Cell membrane; Endoplasmic reticulum membrane; Cell projection, axon","url":"https://www.uniprot.org/uniprotkb/Q7Z4N2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TRPM1","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TRPM1","total_profiled":1310},"omim":[{"mim_id":"615004","title":"LEUCINE-RICH REPEAT, IMMUNOGLOBULIN-LIKE, AND TRANSMEMBRANE DOMAINS-CONTAINING PROTEIN 3; LRIT3","url":"https://www.omim.org/entry/615004"},{"mim_id":"614565","title":"NIGHT BLINDNESS, CONGENITAL STATIONARY, TYPE 1E; CSNB1E","url":"https://www.omim.org/entry/614565"},{"mim_id":"613753","title":"MICRO RNA 211; MIR211","url":"https://www.omim.org/entry/613753"},{"mim_id":"613216","title":"NIGHT BLINDNESS, CONGENITAL STATIONARY, TYPE 1C; CSNB1C","url":"https://www.omim.org/entry/613216"},{"mim_id":"608961","title":"TRANSIENT RECEPTOR POTENTIAL CATION CHANNEL, SUBFAMILY M, MEMBER 3; TRPM3","url":"https://www.omim.org/entry/608961"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Centriolar satellite","reliability":"Uncertain"},{"location":"Golgi apparatus","reliability":"Additional"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"retina","ntpm":16.2},{"tissue":"skin 1","ntpm":4.6}],"url":"https://www.proteinatlas.org/search/TRPM1"},"hgnc":{"alias_symbol":["LTRPC1","CSNB1C"],"prev_symbol":["MLSN1"]},"alphafold":{"accession":"Q7Z4N2","domains":[{"cath_id":"-","chopping":"52-248","consensus_level":"medium","plddt":85.9984,"start":52,"end":248},{"cath_id":"-","chopping":"954-1027_1046-1126_1139-1146","consensus_level":"medium","plddt":80.9556,"start":954,"end":1146},{"cath_id":"1.25.40","chopping":"372-396_452-486","consensus_level":"medium","plddt":81.7013,"start":372,"end":486}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7Z4N2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q7Z4N2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q7Z4N2-F1-predicted_aligned_error_v6.png","plddt_mean":66.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TRPM1","jax_strain_url":"https://www.jax.org/strain/search?query=TRPM1"},"sequence":{"accession":"Q7Z4N2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q7Z4N2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q7Z4N2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q7Z4N2"}},"corpus_meta":[{"pmid":"19861548","id":"PMC_19861548","title":"TRPM1 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TRPM1 null mice completely lose the photoresponse of ON BCs.\",\n      \"method\": \"Immunofluorescence localization, TRPM1-/- knockout mice, ERG, electrophysiology in TRPM1-L-expressing cells, Go regulation assay\",\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, independent replication, mechanistic cascade defined\",\n      \"pmids\": [\"19966281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TRPM1 forms ion channels in melanocytes; endogenous TRPM1 current in human neonatal epidermal melanocytes and mouse melanoma cells was abrogated by miRNA directed against TRPM1, and TRPM1 is predominantly found in intracellular vesicular structures with small plasma membrane currents.\",\n      \"method\": \"Electrophysiology (patch-clamp), miRNA knockdown, subcellular localization imaging\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct electrophysiological measurement combined with specific knockdown\",\n      \"pmids\": [\"19436059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TRPM1 knockdown in human melanocytes reduces intracellular Ca2+ and Ca2+ uptake, decreases tyrosinase activity and melanin pigment; p53 induction (by transfection or UVB) represses TRPM1 expression, demonstrating TRPM1's role in Ca2+ homeostasis and melanogenesis.\",\n      \"method\": \"Lentiviral shRNA knockdown, Ca2+ imaging/measurement, tyrosinase activity assay, p53 transfection, UVB irradiation\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with multiple cellular readouts in single lab\",\n      \"pmids\": [\"19587221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TRPM1 forms a complex with nyctalopin in mouse retina (identified by proteomic search/Co-IP); nyctalopin also interacts with mGluR6; disruption of mGluR6 prevented targeting of TRPM1 to the postsynaptic compartment of ON-bipolar neurons, revealing a macromolecular signaling complex scaffolded by nyctalopin.\",\n      \"method\": \"Proteomic search, Co-immunoprecipitation, immunofluorescence, mGluR6-/- mice\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, proteomic identification, genetic validation with KO mouse\",\n      \"pmids\": [\"21832182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TRPM1 is an ion-conducting plasma membrane channel inhibited by extracellular zinc ions at physiological concentrations; the zinc inhibition is due to a short stretch of seven amino acids unique to the pore region of TRPM1 but not TRPM3; unmodified TRPM1 and TRPM3 form functional heteromultimeric channels.\",\n      \"method\": \"Heterologous expression, patch-clamp electrophysiology, steroid activation, site-directed mutagenesis of pore region, TRPM1/TRPM3 heteromultimer reconstitution\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution, mutagenesis, and biophysical characterization\",\n      \"pmids\": [\"21278253\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"G-protein-mediated inhibition of TRPM1 in ON-bipolar cells requires the Gβγ dimer, not Gαo: dialysis of Gβγ (but not Gαo) closed TRPM1 channels in retinal bipolar cells, melanocytes, and HEK293 cells; activation of an endogenous GPCR pathway releasing Gβγ without activating Go also closed TRPM1.\",\n      \"method\": \"Patch-clamp electrophysiology (intracellular dialysis of protein subunits), multiple cell types including native bipolar cells and heterologous systems\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — electrophysiology with direct protein dialysis, replicated in multiple cell types\",\n      \"pmids\": [\"22586107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TRPM1 localized at the ultrastructural level to the tips of ON-bipolar cell dendrites invaginating cone pedicles and rod spherules in human retina; additionally TRPM1 immunoreactivity was found on synaptic ribbons of a subclass of rods, suggesting a dual function in the ON pathway.\",\n      \"method\": \"Electron microscopy immunohistochemistry, in situ hybridization, laser dissection microscopy/PCR\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct ultrastructural localization with multiple methods\",\n      \"pmids\": [\"21896854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Deletion of mGluR6 renders TRPM1 channels inactive in rod bipolar cells; mGluR6 null mice show hyperpolarized rod bipolar cells with reduced slope conductance and current noise; TRPM1 immunostaining at dendritic tips is greatly reduced without mGluR6, indicating mGluR6-dependent postsynaptic targeting of TRPM1.\",\n      \"method\": \"Whole-cell patch-clamp, capsaicin application, immunostaining in mGluR6-/- mice\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with electrophysiology and localization, mechanistic conclusion\",\n      \"pmids\": [\"22131384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Autoantibodies in melanoma-associated retinopathy (MAR) target TRPM1 in retinal ON-bipolar cells; MAR sera stain TRPM1-transfected HEK cells and ON-bipolar cells in TRPM1+/+ but not TRPM1-/- retina; the autoantibody epitope is likely intracellular and antibodies can be internalized by retinal cells.\",\n      \"method\": \"Immunofluorescence on TRPM1-transfected HEK cells and TRPM1-/- mouse retina, Western blot, confocal colocalization\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — confirmed by TRPM1-KO negative control, Western blot, multiple patient sera\",\n      \"pmids\": [\"21411639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TRPM1 current in rod bipolar cells is susceptible to voltage-independent inhibition by intracellular magnesium; PKCα activation (via DAG/OAG) relieves this Mg2+ inhibition and potentiates TRPM1 current specifically in rod but not cone ON-bipolar cells, dependent on PIP2 hydrolysis.\",\n      \"method\": \"Whole-cell patch-clamp, DAG analog (OAG) application, PKCα knockout mice, pharmacological inhibition, PIP2 hydrolysis manipulation\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — electrophysiology with KO mice and pharmacological dissection, multiple orthogonal approaches\",\n      \"pmids\": [\"21940450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"TRPM1 expression in melanocytes and melanoma is regulated by the transcription factor MITF via a 654 bp upstream sequence containing four E boxes (including an M box); deletion analysis showed that two distal E boxes (E3 and E4) are required for MITF activation and constitutive activity in melanoma.\",\n      \"method\": \"Promoter-luciferase reporter assay, deletion analysis, Western blot\",\n      \"journal\": \"Melanoma research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reporter assay with deletion mapping and protein analysis, single lab\",\n      \"pmids\": [\"15577322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Human melanocytes express mGluR6, and mGluR6 signaling positively couples to TRPM1 in melanocytes (opposite to the negative coupling in retina); knockdown of TRPM1 or mGluR6 abolished L-AP4-induced Ca2+ influx; forced Gαo expression restored negative coupling; absence of Gαo explains the different coupling polarity in melanocytes versus retina.\",\n      \"method\": \"shRNA knockdown, Ca2+ imaging, patch-clamp electrophysiology, Gαo overexpression, pertussis toxin treatment\",\n      \"journal\": \"Pigment cell & melanoma research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (KD, electrophysiology, overexpression, pharmacology), mechanistic dissection of coupling polarity\",\n      \"pmids\": [\"23452348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Serum TRPM1 autoantibodies from MAR patients enter retinal ON-bipolar cells after intravitreal injection and attenuate the ERG b-wave in wild-type but not TRPM1-/- mice; the autoantibody epitope is within the amino-terminal cytoplasmic domain of TRPM1.\",\n      \"method\": \"Intravitreal injection of MAR IgG, ERG recording, immunofluorescence on TRPM1+/+ and TRPM1-/- retinas, TRPM1-transfected CHO cell labeling\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo functional assay with KO controls, epitope mapping\",\n      \"pmids\": [\"23936334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Purified recombinant TRPM1 is mostly dimeric (not tetrameric) as determined by blue native gels, size exclusion chromatography, cross-linking, and cryo-EM single-particle analysis; native retinal TRPM1 exists in two complexes of distinct sizes, suggesting additional partner subunits participate in the functional transduction channel.\",\n      \"method\": \"Recombinant protein purification from insect cells, blue native PAGE, size exclusion chromatography, cross-linking, cryo-EM single-particle analysis, antibody-TRPM1 complex EM\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — purification and structural analysis by multiple methods, but interpretation (dimeric vs tetrameric) was provisional\",\n      \"pmids\": [\"25112866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"LRIT3 is essential for localizing TRPM1 to the dendritic tips of depolarizing bipolar cells; in Lrit3-/- mice, TRPM1 staining is severely decreased at dendritic tips of all depolarizing bipolar cells.\",\n      \"method\": \"Immunofluorescence confocal microscopy in Lrit3-/- mice versus wild-type\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with direct localization readout, single lab\",\n      \"pmids\": [\"25997951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Both the α (Gαo) and βγ (Gβγ) subunits of Go gate TRPM1 in ON-bipolar cells: a constitutively active Gαo mutant closed TRPM1 channels after light activation; phosducin or inactive Gαo (sequestering Gβγ) opened channels in darkness; Co-IP showed TRPM1 interacts with Gβ3 and both active and inactive Gαo; BRET assays showed Gαo interacts with both N- and C-termini of TRPM1 while Gβγ interacts only with the N-terminus.\",\n      \"method\": \"Intracellular dialysis patch-clamp in rod bipolar cells, Co-immunoprecipitation, bioluminescent energy transfer (BRET)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (electrophysiology, Co-IP, BRET), mechanistic dissection of subunit binding sites\",\n      \"pmids\": [\"26883481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Voriconazole inhibits TRPM1 channels in retinal ON-bipolar cells; patch-clamp recording showed voriconazole blocks capsaicin-activated TRPM1 currents in ON-bipolar cells and TRPM3 currents in transfected CHO cells, while only slightly inhibiting mGluR6-mediated GIRK currents.\",\n      \"method\": \"ERG recordings, whole-cell patch-clamp in retinal slices and transfected CHO cells\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — direct electrophysiology in native and heterologous cells with pharmacological dissection\",\n      \"pmids\": [\"25650413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PIP2 binds to an N-terminal fragment of TRPM1 (residues A451-N566); the basic residue K464 is part of a putative pleckstrin homology domain involved in PIP2 interaction, characterized by biophysical methods and molecular modeling.\",\n      \"method\": \"Biophysical binding assays, molecular modeling, mutagenesis of K464\",\n      \"journal\": \"Biophysical chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — in vitro binding with N-terminal fragment only, no functional channel validation\",\n      \"pmids\": [\"26544986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"S100A1 binds to the N-terminal L242-E344 region of TRPM1 in a calcium-dependent manner; complex formation requires clusters of positively charged (K271, R273, R274) and hydrophobic (L263, V270, L276) residues, characterized by fluorescence spectroscopy and mutagenesis.\",\n      \"method\": \"Fluorescence spectroscopy, bioinformatics/structural modeling, mutagenesis\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — in vitro binding characterization with fragment, no functional channel assay\",\n      \"pmids\": [\"27435061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The majority of TRPM1 in retinal ON-bipolar cells resides in the endoplasmic reticulum (ER), not at the plasma membrane; in heterologous cells, recombinant TRPM1 colocalizes with ER markers; fluorescence protease protection assays showed both N and C termini are cytoplasmic, consistent with TRPM channel topology; the ER extends into axons and dendrites but not dendritic tips.\",\n      \"method\": \"Immunofluorescence colocalization with ER markers, fluorescence protease protection (FPP) assay, live imaging of ER-fluorescent marker in bipolar cells\",\n      \"journal\": \"eNeuro\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple localization methods in both native and heterologous cells, topology confirmed by FPP\",\n      \"pmids\": [\"30027108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LRIT3 is expressed presynaptically in rod photoreceptors; restoring LRIT3 expression in Lrit3-/- rods (not DBCs) rescues assembly of the postsynaptic glutamate signalplex (including TRPM1) and rod-driven vision, demonstrating that LRIT3 acts as a transsynaptic organizer of the postsynaptic complex containing TRPM1.\",\n      \"method\": \"Cell-type-specific LRIT3 rescue by AAV in Lrit3-/- mice, immunofluorescence, ERG\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic rescue experiment with cell-type specificity, functional and structural readouts\",\n      \"pmids\": [\"31189098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A point mutation in the pore domain of TRPM1 (p.A1068T) causes dominant negative inhibition of TRPM1 channel function; heterozygous Trpm1+/tvrm27 mice show reduced b-wave amplitudes and reduced DBC responses to LY341495 or capsaicin, indicating that the number of functional TRPM1 channels at DBC dendritic tips determines DBC response amplitude.\",\n      \"method\": \"Chemical mutagenesis screen, genetic complementation, ERG, whole-cell patch-clamp, immunofluorescence\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — pore domain mutation with multiple functional readouts, dominant negative mechanism established\",\n      \"pmids\": [\"22896717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TRPM1 channel opening is required for rod bipolar cell development and synapse formation with AII amacrine cells: TRPM1-/- mice show contracted rod bipolar terminals, fewer synapses with amacrine cells, and reduced AII amacrine cell dendritic complexity; activated Gαo interacts with TRPM1 and induces contraction of rod bipolar terminals; Channelrhodopsin-2 overexpression partially rescues rod bipolar cell development in TRPM1-/- retina.\",\n      \"method\": \"TRPM1-/- KO mice, immunohistochemistry, morphometric analysis, Co-IP (Gαo-TRPM1), Channelrhodopsin-2 rescue, constitutively closed TRPM1 construct\",\n      \"journal\": \"The Journal of neuroscience : the official journal of the Society for Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO phenotype with multiple readouts, rescue experiments, and protein interaction data\",\n      \"pmids\": [\"28899920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TRPM1 current desensitization in ON-bipolar cells depends on the strength of presynaptic stimulus; stimuli activating >20% of maximum TRPM1 current cause desensitization that reduces response to ~40% of peak (time constant ~1 s), with slow recovery (>20 s); TRPM1 desensitization augments the sustained component of downstream ganglion cell EPSCs.\",\n      \"method\": \"Whole-cell patch-clamp of ON-bipolar cells and ganglion cells in retinal slices, dye-filling/morphology\",\n      \"journal\": \"The Journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct electrophysiology in native cells, single lab\",\n      \"pmids\": [\"22041187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TRPM1 is the endpoint of the mGluR6 signal transduction cascade; reconstitution in CHO cells expressing TRPM1, mGluR6, and Gαo demonstrated that TRPM1 is negatively regulated by the mGluR6/Go cascade.\",\n      \"method\": \"Reconstitution in CHO cells expressing TRPM1, mGluR6, and Gαo; electrophysiology\",\n      \"journal\": \"Handbook of experimental pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution of the signaling cascade\",\n      \"pmids\": [\"24756714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TRPM1 promotes acral melanoma progression via Ca2+/CaMKIIδ/AKT pathway: TRPM1 elevates cytosolic Ca2+, activates CaMKIIδ, promotes CaMKIIδ/AKT interaction and AKT activation; CaMKII inhibitor (KN93) suppressed TRPM1-driven melanoma cell growth in vitro and in vivo xenograft models.\",\n      \"method\": \"Loss-of-function and gain-of-function (KD/OE), Ca2+ measurement, Western blot for CaMKIIδ/AKT phosphorylation, Co-IP, colony formation, migration/invasion assay, xenograft mouse model\",\n      \"journal\": \"Journal of advanced research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including in vivo validation, single lab\",\n      \"pmids\": [\"36585114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TRPM1 is a client of the HSP90 chaperone; AUY922 (HSP90 inhibitor) reduces TRPM1 expression by disrupting the CDC37-HSP90 chaperone complex, as demonstrated by co-immunoprecipitation of TRPM1 with HSP90.\",\n      \"method\": \"Co-immunoprecipitation, proteomic profiling (iTRAQ), Western blot, loss/gain-of-function assays\",\n      \"journal\": \"Journal of biomedical science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP plus functional consequence, single lab\",\n      \"pmids\": [\"34301262\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TRPM1 channels are expressed in the lateral amygdala and contribute to capsaicin-induced LTD in the amygdala; using TRPM1-/- mice and pharmacology, capsaicin-induced LTD was absent in TRPM1-/- lateral amygdala; this effect requires group I mGluRs, TRPC5 interaction, and intact GABAergic transmission.\",\n      \"method\": \"Electrophysiology (LTD recordings), TRPM1-/- mice, pharmacological blockers, TRPV1-/- mice\",\n      \"journal\": \"Neurobiology of learning and memory\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mice with electrophysiology and pharmacological dissection\",\n      \"pmids\": [\"27633915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Anti-TRPM1 antibodies in MAR patient serum cause acute degeneration and apoptosis of retinal ON-bipolar cells in wild-type but not TRPM1-/- mice after intravitreal injection, with reduced ERG amplitudes persisting at 3 months.\",\n      \"method\": \"Intravitreal injection, ERG, immunohistochemistry, TUNEL staining, TRPM1-/- controls\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo functional assay with KO negative controls, multiple histological and physiological readouts\",\n      \"pmids\": [\"24282602\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Cryo-EM structure of TRPM1 reveals a canonical tetrameric fold in the intracellular domain but an inverted transmembrane domain with opposite handedness compared to other related channels; the VSLD and pore domain are arranged domain-swapped but with clockwise geometry, forming a large pore-like structure; single-channel recordings show constitutive activity.\",\n      \"method\": \"Cryo-EM, single-particle analysis, single-channel electrophysiology\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with functional validation (electrophysiology), two independent papers with same finding (PMID 41857038 and preprint 41757028)\",\n      \"pmids\": [\"41857038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Cryo-EM structure of human TRPM1 in conducting state reveals tetrameric assembly with an unexpected clockwise domain-swapped pore module of inverted rotational geometry; this topology is accompanied by a dilated selectivity filter, expanded central cavity, and splayed S6 forming a wide intracellular gate; single-channel recordings confirm constitutive activity.\",\n      \"method\": \"Cryo-EM, single-channel patch-clamp electrophysiology\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure + functional electrophysiology; corroborated by independent structural study (PMID 41857038)\",\n      \"pmids\": [\"41757028\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TRPM1 has a functional role in iris sphincter muscle cells: Trpm1-/- mice show severely defective pupillary light reflex (PLR) and iris photomechanical response; light-driven iris constriction independent of brain signaling requires Trpm1 expression and is melanopsin-dependent; capsaicin-driven (pain afferent) iris constriction also requires Trpm1.\",\n      \"method\": \"In vivo PLR measurements in Trpm1-/- mice, isolated eye preparations, pharmacological (capsaicin, melanopsin antagonists)\",\n      \"journal\": \"Experimental eye research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mice with functional readout in multiple experimental contexts, single lab\",\n      \"pmids\": [\"34954202\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Differential epitope masking by monoclonal antibodies reveals synapse-specific multiprotein complexes of TRPM1 at dendritic tips; antibodies recognizing an N-terminal region (N2d) near the transmembrane domain show reduced labeling at dendritic tips vs. cell bodies, suggesting formation of a synapse-specific complex that masks this epitope.\",\n      \"method\": \"Monoclonal antibody epitope mapping, immunofluorescence, quantitative immunoblotting of synaptosomes\",\n      \"journal\": \"Visual neuroscience\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — differential labeling pattern suggesting complex formation, no direct Co-IP of partner\",\n      \"pmids\": [\"29370879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MAR autoantibodies recognize an epitope encoded by exons 9 and 10 of TRPM1 that is conserved with TRPM3; MAR sera cross-react with TRPM3 in the retinal pigment epithelium.\",\n      \"method\": \"Immunofluorescence and Western blot on HEK293 cells transfected with EGFP-TRPM1 deletion constructs, retinal section immunostaining\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — systematic epitope mapping with truncation constructs, single lab\",\n      \"pmids\": [\"28549093\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TRPM1 is a constitutively active, Ca2+-permeable nonselective cation channel with an unusual inverted transmembrane domain topology (revealed by cryo-EM) that localizes to the dendritic tips of retinal ON-bipolar cells via a transsynaptic organizing complex involving LRIT3 (presynaptic), nyctalopin, and mGluR6; in darkness, glutamate-activated mGluR6 couples to the heterotrimeric G-protein Gαoβ3γ13, and both the Gβγ dimer and activated Gαo cooperate to close the channel, while light-induced reduction in glutamate release deactivates mGluR6, allowing constitutive TRPM1 opening and ON-bipolar cell depolarization; PKCα relieves Mg2+-dependent TRPM1 inhibition to modulate synaptic gain, and in melanocytes TRPM1 mediates Ca2+ influx that regulates pigmentation in a polarity-inverted (positively coupled) mGluR6-dependent manner compared to the retina.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TRPM1 is a constitutively active, Ca²⁺-permeable nonselective cation channel that serves as the transduction channel in retinal ON-bipolar cells and regulates Ca²⁺-dependent melanogenesis in melanocytes. In ON-bipolar cells, TRPM1 localizes to dendritic tips via a transsynaptic organizing complex requiring presynaptic LRIT3, postsynaptic nyctalopin, and mGluR6; the mGluR6/Gαo cascade closes the channel in darkness through cooperative action of both Gβγ and Gαo subunits, while light-evoked glutamate reduction permits constitutive channel opening and cell depolarization [PMID:19861548, PMID:22586107, PMID:26883481, PMID:31189098]. Cryo-EM reveals a tetrameric architecture with an unprecedented inverted transmembrane domain topology—clockwise domain-swapped pore modules with a dilated selectivity filter and wide intracellular gate—consistent with its constitutive open state [PMID:41857038]. In melanocytes, TRPM1 mediates Ca²⁺ influx coupled positively (rather than negatively) to mGluR6 owing to the absence of Gαo, thereby promoting tyrosinase activity and melanin synthesis; TRPM1 is also the autoantigen in melanoma-associated retinopathy, where patient autoantibodies enter ON-bipolar cells and cause functional impairment and degeneration [PMID:23452348, PMID:21411639, PMID:24282602].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"MITF was identified as a direct transcriptional activator of TRPM1 in melanocytes, establishing how TRPM1 expression is coupled to the melanocyte differentiation program.\",\n      \"evidence\": \"Promoter-luciferase deletion analysis identified two E-box elements required for MITF-driven TRPM1 transcription in melanoma cells.\",\n      \"pmids\": [\"15577322\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No chromatin-level (ChIP) validation of MITF occupancy\", \"Regulation in retinal ON-bipolar cells not addressed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Three independent studies established TRPM1 as the transduction channel of retinal ON-bipolar cells and a Ca²⁺-conducting channel in melanocytes, resolving the molecular identity of the ON pathway channel that had been sought for decades.\",\n      \"evidence\": \"TRPM1⁻/⁻ mice lacked ERG b-waves and ON-bipolar cell light responses; TRPM1 colocalized with mGluR6 at dendritic tips; constitutive channel activity was demonstrated in heterologous cells and inhibited by Gαo; TRPM1 current was recorded in melanocytes and abolished by miRNA knockdown [PMID:19861548, PMID:19966281, PMID:19436059].\",\n      \"pmids\": [\"19861548\", \"19966281\", \"19436059\", \"19587221\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Gating mechanism (Gα vs Gβγ) unresolved\", \"Subunit stoichiometry unknown\", \"Mechanism of dendritic tip targeting unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"A macromolecular signaling complex was defined at ON-bipolar cell dendritic tips: nyctalopin scaffolds TRPM1 and mGluR6, mGluR6 is required for TRPM1 trafficking to dendritic tips, and PKCα modulates TRPM1 by relieving Mg²⁺-dependent inhibition—establishing the postsynaptic architecture and a gain-control mechanism.\",\n      \"evidence\": \"Proteomic/Co-IP identified nyctalopin–TRPM1 and nyctalopin–mGluR6 complexes; mGluR6⁻/⁻ mice showed loss of TRPM1 dendritic tip localization and inactive channels; PKCα activation via DAG relieved intracellular Mg²⁺ block of TRPM1 current in rod bipolar cells [PMID:21832182, PMID:22131384, PMID:21940450].\",\n      \"pmids\": [\"21832182\", \"22131384\", \"21940450\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct binding interface between nyctalopin and TRPM1 not mapped\", \"Mechanism by which PKCα relieves Mg²⁺ block at the channel level unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"TRPM1 was identified as the autoantigen in melanoma-associated retinopathy (MAR), and its biophysical properties—including zinc inhibition and pore-region determinants—were characterized, establishing a disease mechanism and channel pharmacology.\",\n      \"evidence\": \"MAR sera specifically labeled TRPM1-transfected cells and WT but not TRPM1⁻/⁻ retina; extracellular zinc inhibited TRPM1 via a 7-amino-acid pore sequence; TRPM1/TRPM3 heteromultimeric channels were reconstituted [PMID:21411639, PMID:21278253].\",\n      \"pmids\": [\"21411639\", \"21278253\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of autoantibody internalization into bipolar cells not resolved\", \"Physiological relevance of zinc modulation in vivo unclear\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Gβγ was identified as the direct inhibitory subunit that closes TRPM1, and a pore-domain dominant-negative mutation (A1068T) showed that the number of functional channel complexes at dendritic tips determines ON-bipolar cell response amplitude.\",\n      \"evidence\": \"Dialysis of purified Gβγ (but not Gαo) closed TRPM1 in bipolar cells, melanocytes, and HEK293 cells; heterozygous Trpm1-A1068T mice had reduced b-waves proportional to loss of functional channels [PMID:22586107, PMID:22896717].\",\n      \"pmids\": [\"22586107\", \"22896717\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding site of Gβγ on TRPM1 not structurally resolved\", \"Whether A1068T disrupts pore gating or assembly not distinguished\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The coupling polarity between mGluR6 and TRPM1 was shown to be cell-type-dependent: negative in retina (via Gαo) and positive in melanocytes (which lack Gαo), explaining how the same receptor–channel pair produces opposite functional outcomes in different tissues.\",\n      \"evidence\": \"Knockdown of TRPM1 or mGluR6 in melanocytes abolished L-AP4-induced Ca²⁺ influx; forced Gαo expression in melanocytes restored negative coupling as seen in retina [PMID:23452348].\",\n      \"pmids\": [\"23452348\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the G-protein subunit mediating positive coupling in melanocytes not established\", \"Whether additional signaling intermediaries participate is unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"MAR autoantibodies were shown to be pathogenic in vivo: intravitreal injection caused ON-bipolar cell apoptosis and persistent ERG b-wave reduction, dependent on TRPM1 expression, establishing a direct autoimmune mechanism.\",\n      \"evidence\": \"Purified MAR IgG injected intravitreally reduced b-wave and caused TUNEL-positive bipolar cell death in WT but not TRPM1⁻/⁻ mice [PMID:24282602, PMID:23936334].\",\n      \"pmids\": [\"24282602\", \"23936334\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of antibody-induced cell death (channel block vs complement vs signaling) not determined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The initial model of Gβγ-only gating was revised: both Gαo and Gβγ cooperate to close TRPM1, with BRET mapping showing Gαo binds both N- and C-termini while Gβγ binds only the N-terminus, providing a dual-subunit gating model.\",\n      \"evidence\": \"Constitutively active Gαo closed TRPM1 after light activation; phosducin (sequestering Gβγ) opened channels in darkness; BRET and Co-IP mapped subunit-specific interaction domains [PMID:26883481].\",\n      \"pmids\": [\"26883481\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of dual-subunit gating not resolved\", \"Relative contribution of each subunit to gating kinetics unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"TRPM1 channel activity was shown to be required for postnatal rod bipolar cell development and synaptogenesis with AII amacrine cells, extending TRPM1's role beyond signal transduction to circuit maturation.\",\n      \"evidence\": \"TRPM1⁻/⁻ mice had contracted rod bipolar terminals and fewer synapses; Channelrhodopsin-2 overexpression partially rescued development [PMID:28899920].\",\n      \"pmids\": [\"28899920\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the developmental role reflects Ca²⁺ signaling or depolarization per se is unresolved\", \"Downstream transcriptional programs not identified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"LRIT3 was revealed to act as a presynaptic transsynaptic organizer that directs postsynaptic assembly of the TRPM1-containing signalplex, resolving how the dendritic tip complex is organized across the synapse.\",\n      \"evidence\": \"AAV-mediated LRIT3 restoration specifically in Lrit3⁻/⁻ rods (not bipolar cells) rescued TRPM1 localization and rod-driven ERG responses [PMID:31189098].\",\n      \"pmids\": [\"31189098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Postsynaptic receptor for LRIT3 not identified\", \"Whether LRIT3 directly contacts TRPM1 or acts via nyctalopin/mGluR6 is unresolved\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"The cryo-EM structure of TRPM1 revealed an unprecedented inverted transmembrane topology with clockwise domain-swapped pore modules, a dilated selectivity filter, and a wide intracellular gate, providing a structural basis for constitutive activity and distinguishing TRPM1 from all other structurally characterized TRP channels.\",\n      \"evidence\": \"Two independent cryo-EM studies resolved the TRPM1 tetramer, confirmed by single-channel electrophysiology showing constitutive openings [PMID:41857038].\",\n      \"pmids\": [\"41857038\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of TRPM1 in complex with Gαo or Gβγ not determined\", \"Mechanism by which G-protein binding induces channel closure not structurally resolved\", \"No structure with nyctalopin or mGluR6 complex partners\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis of G-protein–mediated channel closure, the identity of the postsynaptic receptor for presynaptic LRIT3, the mechanism by which MAR autoantibodies cause bipolar cell death, and whether TRPM1's role in extra-retinal tissues (amygdala, iris) involves the same signaling complex as in ON-bipolar cells.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No TRPM1–G-protein co-structure available\", \"Transsynaptic binding partner of LRIT3 on the postsynaptic side unidentified\", \"Pathogenic mechanism of MAR autoantibodies at the molecular level unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 2, 5, 6, 22, 30, 31]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 5, 7, 22]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [20]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 6, 16, 23, 28]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 6, 12, 16, 25]},\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [0, 1, 7, 8, 22, 32]}\n    ],\n    \"complexes\": [\n      \"mGluR6-TRPM1-nyctalopin signalplex\",\n      \"TRPM1-Gαo-Gβ3γ13 complex\"\n    ],\n    \"partners\": [\n      \"GRM6\",\n      \"NYX\",\n      \"LRIT3\",\n      \"GNAO1\",\n      \"GNB3\",\n      \"PRKCA\",\n      \"TRPM3\",\n      \"S100A1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}