{"gene":"TMEM175","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2015,"finding":"TMEM175 forms a major K+-selective channel (KEL) on endosomes and lysosomes. Direct lysosomal patch-clamp recordings showed that lysosomes lacking TMEM175 exhibit no K+ conductance, have markedly depolarized membrane potential, little sensitivity to changes in [K+], and compromised luminal pH stability and abnormal fusion with autophagosomes during autophagy. Unlike canonical K+ channels, TMEM175 has two repeats of 6-transmembrane-spanning segments and lacks the GYG P-loop selectivity filter.","method":"Direct organelle patch-clamp electrophysiology; genetic knockout; lysosomal pH and autophagy assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct electrophysiological reconstitution in isolated lysosomes with genetic KO controls and multiple functional readouts; published in Cell and widely replicated","pmids":["26317472"],"is_preprint":false},{"year":2017,"finding":"TMEM175 deficiency results in unstable lysosomal pH, decreased lysosomal catalytic activity, decreased glucocerebrosidase activity, impaired autophagosome clearance, and decreased mitochondrial respiration. In rat primary neurons, TMEM175 deficiency increased susceptibility to exogenous α-synuclein fibrils and caused increased phosphorylated and detergent-insoluble α-synuclein deposits.","method":"shRNA knockdown in neuronal model; lysosomal pH assays; cathepsin activity assays; GCase activity assay; mitochondrial respiration (Seahorse); α-synuclein fibril treatment with phospho-α-syn immunostaining","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal functional assays in neuronal model with defined phenotypic readouts; independently supported by subsequent studies","pmids":["28193887"],"is_preprint":false},{"year":2017,"finding":"Crystal structure of prokaryotic TMEM175 (CmTMEM175) reveals a novel tetrameric architecture completely different from canonical K+ channels. All six transmembrane helices are tightly packed within each subunit without domain swapping. TM1 acts as the pore-lining inner helix creating an hourglass-shaped ion permeation pathway. Three layers of hydrophobic residues on TM1 form the selectivity filter; mutagenesis showed the first conserved isoleucine layer is primarily responsible for channel selectivity.","method":"X-ray crystallography of prokaryotic TMEM175; site-directed mutagenesis; electrophysiology","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and functional validation; foundational structural paper","pmids":["28723891"],"is_preprint":false},{"year":2019,"finding":"The TMEM175 p.M393T variant (rs34311866) reduces lysosomal pH regulation in response to starvation, reduces lysosomal localization, and increases accumulation of phosphorylated α-synuclein with effects intermediate between WT and knockout. Overexpression of WT TMEM175 reduced p-α-syn, while overexpression of p.M393T did not change α-synuclein phosphorylation. shRNA knockdown of only TMEM175 (not neighboring genes) consistently influenced accumulation of phosphorylated α-synuclein.","method":"shRNA knockdown screen; variant overexpression; lysosomal pH assay; autophagy substrate clearance assay; phospho-α-syn immunostaining; lysosomal localization imaging","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (pH assay, localization, α-syn phosphorylation) in single lab; mechanistically informative variant characterization","pmids":["31261387"],"is_preprint":false},{"year":2019,"finding":"The TMEM175 p.M393T variant creates a polar side-chain in the hydrophobic core of the transmembrane domain predicted to destabilize assembly, maturation, or trafficking, and is associated with reduced glucocerebrosidase (GCase) activity. Lysosomal localization of both p.M393T and p.Q65P variants was not affected. Molecular dynamics simulations suggested p.Q65P may increase stability and ion conductance.","method":"Homology modeling; normal mode analysis; molecular dynamics simulations; lysosomal localization experiments; GCase activity assay in patient cohort","journal":"Annals of neurology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional localization experiment combined with computational modeling; GCase association in patient cohort; single lab","pmids":["31658403"],"is_preprint":false},{"year":2020,"finding":"Cryo-EM structures of human TMEM175 in open and closed conformations (up to 2.6 Å resolution) reveal a homodimeric architecture with a central ion-conduction pore. Conserved isoleucine residues in the center of the pore serve as the gate in the closed conformation and establish a constriction essential for K+ selectivity in the open conformation.","method":"Cryo-EM structure determination; mutagenesis; electrophysiology","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution cryo-EM structures of both open and closed states with mutagenesis validation of gating and selectivity residues","pmids":["32228865"],"is_preprint":false},{"year":2020,"finding":"X-ray structure of a closed bacterial TMEM175 channel in complex with a nanobody fusion-protein revealed bound K+ ions and a highly conserved layer of threonine residues in the pore that confers basal K+ selectivity. An additional layer comprising two serines in human TMEM175 increases selectivity further and renders the channel sensitive to 4-aminopyridine and Zn2+. Large hydrophobic side chains occlude the pore forming a physical gate; channel opening by iris-like motions simultaneously relocates the gate and exposes the selectivity filter.","method":"X-ray crystallography; electrophysiology; mutagenesis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with bound ions plus mutagenesis and electrophysiology; orthogonal to and consistent with cryo-EM studies","pmids":["32267231"],"is_preprint":false},{"year":2020,"finding":"TMEM175 deficiency in neurons inhibits lysosomal hydrolytic function by affecting lysosomal pH, impairs autophagosome-lysosome fusion, and leads to impaired mitochondrial accumulation (failure to clear damaged mitochondria). Exogenous upregulation of TMEM175 reversed OGD/R-induced lysosomal dysfunction in cultured neurons.","method":"Lysosomal pH assay (LysoSensor, acridine orange); cathepsin B and D activity assays; TMEM175 overexpression/knockdown in cultured neurons and in vivo MCAO/R model","journal":"Molecular brain","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple lysosomal functional readouts with gain and loss of function in both in vitro and in vivo models; single lab","pmids":["32799888"],"is_preprint":false},{"year":2022,"finding":"TMEM175 acts as a proton-activated, proton-selective channel (LyPAP) on the lysosomal membrane that mediates the lysosomal H+ leak. Acidification beyond the normal range (below pH 4.5–5.0) potently activated the channel to prevent further lysosomal acidification. An endogenous polyunsaturated fatty acid and synthetic agonists also activated TMEM175 to trigger lysosomal proton release. TMEM175 deficiency caused lysosomal over-acidification, impaired proteolytic activity, and facilitated α-synuclein aggregation in vivo. Mutational analysis showed the H+ conductance is essential for normal lysosome function.","method":"Lysosomal patch-clamp electrophysiology; ion substitution experiments; mutagenesis; lysosomal pH measurement; proteolytic activity assays; in vivo α-synuclein aggregation model","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct electrophysiology with mutagenesis and multiple functional assays including in vivo validation; published in Cell","pmids":["35750034"],"is_preprint":false},{"year":2022,"finding":"Human TMEM175 exhibits pH-dependent structural changes: it constitutively conducts K+ at pH 7.4 but shows reduced K+ permeation at acidic pH, while proton current increases with decreasing pH. Molecular dynamics simulation, structure-based mutagenesis, and electrophysiology indicate K+ ions and protons share the same permeation pathway. The M393T PD-risk variant shows reduced function in both K+ and proton permeation.","method":"Cryo-EM structural analysis; whole-endolysosome patch-clamp electrophysiology; molecular dynamics simulations; site-directed mutagenesis","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure combined with mutagenesis, MD simulation, and electrophysiology in single study","pmids":["35333573"],"is_preprint":false},{"year":2022,"finding":"Bcl-2 binds to and inhibits TMEM175 channel activity. Bcl-2 inhibitors activate TMEM175 in a caspase-independent manner. Increased TMEM175 function inhibits mitophagy, disrupts mitochondrial homeostasis, and increases reactive oxygen species (ROS) production. ROS further activates TMEM175, forming a positive feedback loop to augment apoptosis. In an MPTP mouse model of PD, TMEM175 knockout mitigated motor impairment and dopaminergic neuron loss.","method":"Co-immunoprecipitation (Bcl-2/TMEM175 binding); lysosomal patch-clamp; Bcl-2 inhibitor treatment; ROS measurement; mitophagy assay; TMEM175 KO mouse MPTP model with behavioral and histological readouts","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assay combined with electrophysiology, multiple cellular phenotype readouts, and in vivo KO model","pmids":["35913019"],"is_preprint":false},{"year":2022,"finding":"Higher-resolution cryo-EM structures of open and closed human TMEM175 and molecular dynamics simulations demonstrate that the open-state pore is permeable to both K+ and (to a lesser degree) Na+. Both cations must dehydrate significantly to penetrate the narrow hydrophobic constriction, but ion flow is assisted by a favorable electrostatic field. The balance of ion dehydration energetics explains K+ selectivity over Na+ despite absence of a canonical selectivity filter. Mutagenesis experiments confirmed exquisite sensitivity of channel selectivity to perturbations that mitigate the constriction.","method":"Cryo-EM structure determination (higher resolution than prior); molecular dynamics simulations; mutagenesis; electrophysiology","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — improved-resolution cryo-EM with extensive MD simulation and mutagenesis validation of selectivity mechanism","pmids":["35608336"],"is_preprint":false},{"year":2022,"finding":"Cryo-EM structure of TMEM175 bound to 4-aminopyridine (4-AP) shows that 4-AP binds near the center of the ion conduction pathway in the open state. MD simulations show the binding site is near the middle of the transmembrane potential gradient, explaining voltage-dependent dissociation. Bound 4-AP rapidly switches between three predominant binding poses stabilized by the twofold symmetry of the channel, and prevents both ion permeation and water flow.","method":"Cryo-EM structure of inhibitor-bound TMEM175; molecular dynamics simulations","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure of inhibitor-bound channel combined with MD simulations revealing mechanism of block","pmids":["36279431"],"is_preprint":false},{"year":2021,"finding":"TMEM175 is regulated by protein kinase B (PKB/Akt) and dynamin-dependent endocytosis. Dynamin inhibitors (dynasore, dyngo-4a) substantially increased TMEM175 currents at the plasma membrane by preventing channel internalization. A constitutively active Akt mutant and the Akt activator SC79 increased TMEM175 current, while the allosteric Akt inhibitor MK2206 diminished it. TMEM175 is more permeable to cesium than potassium and is voltage-dependently blocked by 4-AP.","method":"Two-electrode voltage clamp in Xenopus oocytes; dominant-negative dynamin coexpression; immunocytochemistry for surface TMEM175; pharmacological Akt manipulation","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology combined with immunocytochemistry and pharmacological/genetic manipulation of Akt and dynamin; single lab","pmids":["34638858"],"is_preprint":false},{"year":2023,"finding":"TMEM175 mediates both lysosomal H+ influx (refilling) and H+ efflux (releasing) in an asymmetric manner. Using whole-endolysosome patch-clamp in enlarged lysosomes under physiological pH gradient, integrated lysosomal H+ flux signals were recorded. Loss-of-function F39V mutant and the antagonist 2-GBI abolished all lysosomal H+ fluxes. LAMP1 glycosylation modulates these H+ fluxes.","method":"Whole-endolysosome patch-clamp in vacuolin-1-enlarged lysosomes; TMEM175 loss-of-function mutant (F39V); pharmacological block (2-GBI); LAMP1 manipulation","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct organelle electrophysiology with genetic loss-of-function and pharmacological controls; single lab","pmids":["37165739"],"is_preprint":false},{"year":2023,"finding":"Solid-supported membrane-based electrophysiology (SSME) of TMEM175 revealed two distinct conducting states (two-slope I/c curve for K+). H+ flux measurements yielded a permeability ratio PH/PK of ~48,500. Cytosolic pH decrease inhibited both K+ and H+ conductivity of TMEM175, while lysosomal-side pH changes did not have major effects. Tool compounds (4-AP, Zn2+ as inhibitors; DCPIB, arachidonic acid, SC-79 as enhancers) were validated across multiple assay formats.","method":"Solid-supported membrane-based electrophysiology (SSME); automated whole-cell patch-clamp (APC); lysosomal patch-clamp (LPC); pharmacological profiling","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple electrophysiology platforms with pharmacological cross-validation; single study but orthogonal methods","pmids":["37628970"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structures of human TMEM175 bound to selective inhibitors 2-PPA and AP-6 reveal that they act as pore blockers, binding at distinct sites in the pore and occluding the ion permeation pathway. Acute inhibition by these inhibitors increases lysosomal macromolecule catabolism, accelerating macropinocytosis and other digestive processes.","method":"Cryo-EM structure of inhibitor-bound TMEM175; lysosomal catabolism assays; macropinocytosis assay","journal":"Journal of the American Chemical Society","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures of two distinct inhibitor-bound states with functional lysosomal activity readouts","pmids":["39116214"],"is_preprint":false},{"year":2025,"finding":"Rigorous re-examination found that in the lysosome, TMEM175 predominantly conducts K+ and is not a H+-selective channel. The native lysosomal H+ leak is ~0.02 fA, which is remarkably small and argues strongly against major H+ channel contributions. The predominant effect of TMEM175 deficiency is lysosomal alkalinization in challenged cells (not over-acidification), which is consistent with K+ conductance through TMEM175. Lysosomes can be hyper-acidified by manipulations in the presence or absence of TMEM175.","method":"Lysosomal patch-clamp electrophysiology; lysosomal pH measurement; genetic manipulation of TMEM175; ion substitution experiments","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct quantitative electrophysiology with rigorous controls challenging prior proton-channel model; published in JCB with editorial commentary; multiple independent lines of evidence","pmids":["41134537"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structures of human TMEM175 in complex with three agonists (DCY1020, DCY1040, TUG-891) captured an open state of the channel. DCY1020/1040 binds at the interface between two subunits, inducing an open conformation further augmented by synergistic agonist TUG-891. Surface plasmon resonance, systematic mutagenesis, whole-endolysosome patch-clamp, and MD simulations validated the binding sites. These agonists facilitate removal of pathological α-synuclein and restore function of PD-related TMEM175 variants in neurons.","method":"Cryo-EM structure; surface plasmon resonance; mutagenesis; whole-endolysosome patch-clamp; molecular dynamics simulations; α-synuclein clearance assay in neurons","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures of agonist-bound open state combined with SPR, mutagenesis, electrophysiology, MD simulations, and functional cellular assays in single study","pmids":["40865534"],"is_preprint":false},{"year":2025,"finding":"Luminal-side H57 residue acts as a proton sensor critical for proton-selective gating of TMEM175. A pH drop from 7.4 to 4.7 on the luminal side triggers increased inward and outward currents with a transient shift in reversal potential toward H+ equilibrium voltage. H57 forms intra- and inter-subunit salt bridges with D279 and E282, stabilizing the open state. The H57Y mutant shows reduced H+ and K+ conductance and reduced H+/K+ selectivity, confirmed by both whole-cell and lysosomal electrophysiology.","method":"Whole-cell patch-clamp (plasma membrane redistributed TMEM175); lysosomal patch-clamp; molecular dynamics simulations; site-directed mutagenesis (H57Y); reversal potential measurements","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis combined with MD simulations and two independent electrophysiology formats (whole-cell and lysosomal patch-clamp)","pmids":["41533442"],"is_preprint":false},{"year":2025,"finding":"TMEM175 conditional knockout in macrophages promotes anti-tumor immunity through elevated M1-like polarization, reduced M2-like polarization, and facilitated recruitment/activation of T cells and NK cells. The anti-tumor effect is abrogated by caspase-1 inhibitor VX-765, anti-IL-1β, and anti-IL-18. Tmem175-/- BMDMs show enhanced tumor antigen cross-presentation strengthened by IL-1β and IL-18. NLRP3 inflammasome is robustly activated in Tmem175-/- BMDMs via lysosomal permeabilization and cathepsin B leakage.","method":"Conditional macrophage-specific TMEM175 KO mouse; tumor growth/metastasis models; BMDM in vitro assays; caspase-1 inhibitor; neutralizing antibodies; cross-presentation assay; NLRP3 activation assay; cathepsin B leakage measurement","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with multiple mechanistic readouts (inflammasome, cross-presentation, cathepsin B), pharmacological validation, and in vivo tumor models","pmids":["41690940"],"is_preprint":false},{"year":2024,"finding":"TMEM175 deficiency in bone marrow-derived mesenchymal stem cells (BMSCs) suppresses osteoblast differentiation as evidenced by decreased matrix mineralization and lower expression of osteoblast marker genes. TMEM175 deficiency leads to lysosomal dysfunction and partially impairs autophagic clearance during osteoblast differentiation. The TMEM175 inhibitor 4-AP decreased osteoblast differentiation of BMSCs.","method":"TMEM175 knockdown in BMSCs; osteoblast differentiation assay (matrix mineralization, marker gene expression); lysosomal pH and function assays; autophagic flux measurement; 4-AP pharmacological inhibition","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KD and pharmacological inhibition with multiple functional readouts; single lab","pmids":["39426687"],"is_preprint":false},{"year":2026,"finding":"TMEM175 activity in macrophages maintains lysosomal pH and prevents cholesterol accumulation. In BK channel-deficient (BK-/-) macrophages, TMEM175 is upregulated as a compensatory mechanism to maintain lysosomal function. Inhibition of TMEM175 activity in both BK-/- and WT macrophages increased lysosomal pH and reduced silica-induced cell death and IL-1β release, indicating TMEM175 regulates silica-induced inflammatory responses through lysosomal pH control.","method":"BK-/- mouse BMDM; TMEM175 inhibitor treatment; lysosomal pH assay; cholesterol accumulation assay; IL-1β measurement; cell death assay","journal":"Inhalation toxicology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition with lysosomal functional and inflammatory readouts in KO background; single lab","pmids":["40402504"],"is_preprint":false},{"year":2024,"finding":"DABMA activates the endosomal TMEM175 channel with an EC50 of 17.9 μM as measured by organelle patch-clamp. Depletion of TMEM175 significantly decreases the antitoxin activity of DABMA and affects its action on acidic/Rab7-positive endosomes and endolysosomal trafficking, demonstrating that TMEM175 is necessary for DABMA's anti-pathogen activity.","method":"Organelle patch-clamp electrophysiology (EC50 determination); TMEM175 protein depletion; endosomal pH and Rab7 imaging; endolysosomal trafficking assays","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiology combined with genetic depletion and functional trafficking assays; single lab","pmids":["39097908"],"is_preprint":false},{"year":2026,"finding":"TMEM175 overexpression in cardiomyocytes confers cardioprotection after myocardial infarction by restoring lysosomal function (biogenesis, normalized pH, enzyme activities, and autophagic flux). Mechanistically, TMEM175 reduction caused by MI increases mTORC1 phosphorylation on lysosomal membranes and suppresses nuclear translocation of transcription factor EB (TFEB), impairing TFEB's transcriptional regulation of lysosome-associated genes. TMEM175 restoration reverses this cascade.","method":"Gain and loss of function in vivo MI model and in vitro hypoxia model; lysosomal pH/enzyme activity/biogenesis assays; mTORC1 phosphorylation measurement; TFEB nuclear translocation imaging; autophagic flux assay","journal":"Acta pharmacologica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss of function with mechanistic readouts (mTORC1, TFEB) in both in vitro and in vivo models; single lab","pmids":["41741766"],"is_preprint":false},{"year":2025,"finding":"Mutagenesis identified T119 and H449 as structural determinants of TMEM175 activation gating. T119A and H449A mutations decreased apparent potencies of multiple TMEM175 activators (DCPIB, zafirlukast, montelukast). The T119A mutation produced a constitutively open channel phenotype. CysLT1 receptor antagonists (zafirlukast, montelukast, pranlukast) directly activate TMEM175 independently of CysLT1R, and DCPIB/zafirlukast activate TMEM175 independently of AKT, while montelukast activation is partially AKT-dependent.","method":"High-throughput screening; fluorescence assays; automated patch-clamp; mutagenesis (T119A, H449A); AKT inhibitor (MK2206) treatment; computational modeling","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis combined with electrophysiology and pharmacological characterization; multiple activators tested; single lab","pmids":["41670588"],"is_preprint":false},{"year":2023,"finding":"Functional analysis of novel TMEM175 mutations identified in PD patients (including p.R35C, p.R183X, p.A270T, p.P308L, p.S348L, p.L405V, p.R414W, p.P427fs, p.R481W) revealed loss of K+ conductance by patch-clamp and reduced channel affinity for Akt by co-immunoprecipitation. Patient-derived fibroblasts showed impaired autophagic/lysosomal proteolytic flux and increased unfolded protein response markers.","method":"Patch-clamp electrophysiology; co-immunoprecipitation (TMEM175-Akt); autophagic flux assay; UPR marker measurement in patient-derived fibroblasts","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — electrophysiology and binding assay in patient-derived cells; single lab; multiple mutations tested","pmids":["36609826"],"is_preprint":false}],"current_model":"TMEM175 is a non-canonical lysosomal/endosomal cation channel that forms a homodimer (or prokaryotic tetramer) with a novel 6-TM architecture lacking the canonical TVGYG selectivity filter; it primarily conducts K+ through a hydrophobic isoleucine constriction that simultaneously gates and selects ions, maintains lysosomal membrane potential and luminal pH stability, regulates autophagosome-lysosome fusion, and is activated by Akt/PKB and inhibited by Bcl-2, with loss of function causing lysosomal alkalinization, impaired proteolysis, glucocerebrosidase deficiency, mitochondrial dysfunction, and α-synuclein accumulation relevant to Parkinson's disease pathogenesis; the channel also conducts protons through the same pore (with H57 as a key proton-sensing gating residue), though whether this H+ conductance constitutes a major H+ leak pathway remains actively debated."},"narrative":{"mechanistic_narrative":"TMEM175 is a non-canonical lysosomal and endosomal cation channel that sets the ionic and pH environment of the late endo-lysosomal system and thereby controls autophagy, organelle catabolism, and protein quality control [PMID:26317472, PMID:28193887]. Rather than the canonical TVGYG selectivity filter, it uses a novel architecture — a homodimer of two 6-transmembrane repeats in eukaryotes (a tetramer in prokaryotes) — in which TM1 lines an hourglass-shaped pore, and layers of hydrophobic isoleucine residues simultaneously form the gate and the K+ selectivity constriction; threonine and serine layers add to selectivity and confer sensitivity to 4-aminopyridine and Zn2+, and channel opening occurs through iris-like helical motions that relocate the gate and expose the filter [PMID:28723891, PMID:32228865, PMID:32267231, PMID:35608336]. K+ and Na+ permeation is governed by ion-dehydration energetics through the narrow constriction rather than a structured filter, explaining selectivity in the absence of a P-loop [PMID:35608336]. The channel maintains lysosomal membrane potential and luminal pH stability; loss of function destabilizes lysosomal pH, reduces cathepsin and glucocerebrosidase activity, impairs autophagosome-lysosome fusion and autophagic clearance, and depresses mitochondrial respiration, with the predominant pH consequence in challenged cells being alkalinization consistent with K+ conductance [PMID:26317472, PMID:28193887, PMID:41134537]. These defects drive accumulation of phosphorylated, detergent-insoluble α-synuclein, and TMEM175 deficiency or the common p.M393T risk variant — which destabilizes the protein and reduces both K+ and proton permeation — link the channel to Parkinson's disease pathogenesis [PMID:28193887, PMID:31261387, PMID:35333573, PMID:36609826]. TMEM175 activity is regulated by Akt/PKB and dynamin-dependent endocytosis and is inhibited by Bcl-2 binding, coupling channel gating to survival signaling and mitochondrial homeostasis [PMID:35913019, PMID:34638858]. Beyond neurons, TMEM175 governs lysosomal pH in macrophages, where its loss triggers NLRP3 inflammasome activation via cathepsin B leakage, and supports osteoblast differentiation and cardiomyocyte lysosomal function through TFEB-dependent biogenesis [PMID:35913019, PMID:41690940, PMID:39426687, PMID:41741766]. Whether TMEM175 additionally functions as a proton-selective channel mediating a major lysosomal H+ leak is actively debated: direct proton-conduction with H57 as a luminal proton-sensing gating residue has been reported [PMID:35750034, PMID:41533442], while rigorous quantitative re-examination found K+ to be the predominant conducted ion and the native H+ leak negligible [PMID:41134537].","teleology":[{"year":2015,"claim":"Established the founding identity of TMEM175 as the major lysosomal/endosomal K+ channel and tied it to a basic organelle function, answering whether an uncharacterized membrane protein carried lysosomal K+ conductance.","evidence":"Direct lysosomal patch-clamp with genetic knockout plus pH and autophagy assays","pmids":["26317472"],"confidence":"High","gaps":["Molecular basis of selectivity without a GYG filter unresolved","Channel structure unknown","Physiological gating cues not defined"]},{"year":2017,"claim":"Connected channel loss to a defined disease-relevant cascade, showing that TMEM175 deficiency degrades lysosomal proteolysis, GCase activity, and mitochondrial respiration and sensitizes neurons to α-synuclein pathology.","evidence":"shRNA knockdown in neurons with pH, cathepsin, GCase, Seahorse, and phospho-α-syn readouts","pmids":["28193887"],"confidence":"High","gaps":["Causal chain from pH change to α-syn aggregation not dissected","In vivo relevance untested at this stage"]},{"year":2017,"claim":"Solved the first structure, revealing a unique tetrameric architecture with TM1-lined pore and hydrophobic isoleucine selectivity layers — explaining how a channel selects K+ without a canonical filter.","evidence":"X-ray crystallography of prokaryotic CmTMEM175 with mutagenesis and electrophysiology","pmids":["28723891"],"confidence":"High","gaps":["Prokaryotic; human dimeric architecture not yet confirmed","Open vs closed states not both captured"]},{"year":2019,"claim":"Characterized the common p.M393T Parkinson's risk variant mechanistically, showing intermediate loss of pH regulation, reduced GCase, and increased α-syn phosphorylation, linking a genetic risk allele to channel dysfunction.","evidence":"Variant overexpression, knockdown specificity, pH/localization assays, computational modeling, patient GCase cohort","pmids":["31261387","31658403"],"confidence":"High","gaps":["Discordant reports on whether localization is affected","Quantitative effect on conductance not measured here"]},{"year":2020,"claim":"Defined the human channel in open and closed states and pinpointed the isoleucine gate and selectivity constriction plus threonine/serine selectivity layers and pharmacological sensitivities, providing an atomic gating model.","evidence":"Cryo-EM and X-ray structures of human and bacterial channel with bound ions, mutagenesis, and electrophysiology","pmids":["32228865","32267231"],"confidence":"High","gaps":["Energetics of selectivity not quantified","Physiological gating trigger in lysosome unclear"]},{"year":2020,"claim":"Extended the lysosomal dysfunction phenotype to mitophagy and ischemic injury, showing TMEM175 deficiency impairs damaged-mitochondria clearance and that overexpression rescues OGD/R-induced lysosomal failure.","evidence":"pH, cathepsin assays, gain/loss of function in neurons and MCAO/R model","pmids":["32799888"],"confidence":"Medium","gaps":["Single lab","Direct link between channel conductance and mitophagy unresolved"]},{"year":2021,"claim":"Identified upstream regulation by Akt/PKB signaling and dynamin-dependent endocytosis, explaining how channel surface density and activity are dynamically controlled.","evidence":"Two-electrode voltage clamp in oocytes, dominant-negative dynamin, surface immunocytochemistry, Akt pharmacology","pmids":["34638858"],"confidence":"Medium","gaps":["Direct Akt phosphorylation site not mapped here","Oocyte/plasma-membrane context differs from lysosome"]},{"year":2022,"claim":"Proposed a second permeation function — proton-activated, proton-selective conductance mediating the lysosomal H+ leak that prevents over-acidification — reframing TMEM175 as a pH-protective channel.","evidence":"Lysosomal patch-clamp, ion substitution, mutagenesis, PUFA/agonist activation, in vivo α-syn model","pmids":["35750034"],"confidence":"High","gaps":["Magnitude of physiological H+ leak contested","Reconciliation with predominant K+ conductance unresolved"]},{"year":2022,"claim":"Showed K+ and protons share one permeation pathway with pH-dependent structural switching, and that M393T reduces both conductances, unifying the K+ and H+ activities in a single pore.","evidence":"Cryo-EM, whole-endolysosome patch-clamp, MD simulation, mutagenesis","pmids":["35333573"],"confidence":"High","gaps":["Relative physiological contribution of each ion not settled"]},{"year":2022,"claim":"Resolved the biophysical basis of K+-over-Na+ selectivity as dehydration energetics assisted by a favorable electrostatic field, explaining selectivity without a structured filter.","evidence":"Higher-resolution cryo-EM, extensive MD simulation, mutagenesis, electrophysiology","pmids":["35608336"],"confidence":"High","gaps":["In situ ionic conditions modeled, not directly measured"]},{"year":2022,"claim":"Identified Bcl-2 as a direct inhibitory binding partner and embedded TMEM175 in a ROS/apoptosis feedback loop, and showed knockout is protective in an MPTP Parkinson's model.","evidence":"Co-IP, lysosomal patch-clamp, Bcl-2 inhibitors, ROS/mitophagy assays, TMEM175 KO MPTP mouse","pmids":["35913019"],"confidence":"High","gaps":["Bcl-2 binding interface not mapped structurally","Direction of net Parkinson's effect (loss vs gain) context-dependent"]},{"year":2022,"claim":"Mapped the binding site and voltage-dependent block mechanism of the classic inhibitor 4-aminopyridine within the open pore.","evidence":"Cryo-EM of inhibitor-bound channel with MD simulations","pmids":["36279431"],"confidence":"High","gaps":["Therapeutic selectivity not addressed"]},{"year":2023,"claim":"Characterized a panel of PD-patient mutations as loss-of-K+-conductance alleles with reduced Akt affinity and downstream autophagic/UPR defects, strengthening the genetic-functional link to Parkinson's.","evidence":"Patch-clamp, TMEM175-Akt co-IP, autophagic flux and UPR markers in patient fibroblasts","pmids":["36609826"],"confidence":"Medium","gaps":["Single lab","Causality of UPR vs lysosomal defect not separated"]},{"year":2023,"claim":"Quantified asymmetric bidirectional H+ flux and a high PH/PK permeability ratio, and showed cytosolic-side (not luminal-side) pH and LAMP1 glycosylation modulate conductance.","evidence":"Whole-endolysosome and solid-supported-membrane electrophysiology with loss-of-function mutants and pharmacology","pmids":["37165739","37628970"],"confidence":"Medium","gaps":["High PH/PK ratio later contested by quantitative leak measurements","LAMP1 modulation mechanism unclear"]},{"year":2024,"claim":"Established TMEM175 as a tractable drug target, defining cryo-EM-resolved pore-blocker sites whose acute inhibition paradoxically accelerates lysosomal catabolism and macropinocytosis.","evidence":"Cryo-EM of 2-PPA/AP-6-bound states with catabolism and macropinocytosis assays","pmids":["39116214"],"confidence":"High","gaps":["Mechanism by which channel block enhances catabolism not fully explained"]},{"year":2024,"claim":"Extended the channel's roles beyond neurons, showing TMEM175 is required for osteoblast differentiation and for an antitoxin compound's endosomal action, demonstrating tissue-broad lysosomal/endosomal functions.","evidence":"Knockdown/4-AP in BMSCs with differentiation and autophagy assays; organelle patch-clamp EC50 and depletion with trafficking assays for DABMA","pmids":["39426687","39097908"],"confidence":"Medium","gaps":["Single labs","Direct molecular link between channel activity and differentiation/trafficking phenotypes incomplete"]},{"year":2025,"claim":"Rigorously re-examined the proton hypothesis and concluded TMEM175 predominantly conducts K+ with a negligible native H+ leak, and that deficiency causes alkalinization rather than over-acidification — directly challenging the proton-channel model.","evidence":"Quantitative lysosomal patch-clamp, pH measurement, genetic manipulation, ion substitution","pmids":["41134537"],"confidence":"High","gaps":["Reconciliation with prior proton-conduction structural/electrophysiology reports unresolved","Conditions under which H+ conductance becomes relevant undefined"]},{"year":2025,"claim":"Identified luminal H57 as a proton-sensing gating residue forming salt bridges that stabilize the open state, providing a structural mechanism for proton-dependent gating.","evidence":"H57Y mutagenesis, MD simulations, whole-cell and lysosomal patch-clamp, reversal-potential measurements","pmids":["41533442"],"confidence":"High","gaps":["Physiological relevance of proton gating debated given small native leak","Does not resolve K+ vs H+ predominance controversy"]},{"year":2025,"claim":"Captured agonist-bound open states and defined activation determinants, demonstrating that small-molecule activators can restore PD-variant function and clear pathological α-synuclein in neurons — a therapeutic proof of concept.","evidence":"Cryo-EM with SPR, mutagenesis (T119/H449), patch-clamp, MD, and α-syn clearance assays; pharmacological characterization of CysLT antagonist activators","pmids":["40865534","41670588"],"confidence":"High","gaps":["In vivo efficacy of agonists not established here","Relationship of activation to K+ vs H+ conductance not fully resolved"]},{"year":2025,"claim":"Defined an immune and inflammatory role: macrophage TMEM175 loss activates the NLRP3 inflammasome via cathepsin B leakage, promoting anti-tumor immunity, while channel activity restrains silica-induced inflammation through lysosomal pH control.","evidence":"Conditional macrophage KO tumor models, BMDM inflammasome/cross-presentation/cathepsin B assays; BK-/- BMDM with inhibitor and IL-1β readouts","pmids":["41690940","40402504"],"confidence":"High","gaps":["Whether immune effects derive from K+ or H+ conductance unclear","Therapeutic window between neuroprotection and inflammasome activation undefined"]},{"year":2026,"claim":"Linked TMEM175 to cardiac protection via a lysosome-mTORC1-TFEB biogenesis axis, showing channel restoration reverses post-infarction lysosomal failure.","evidence":"Gain/loss of function in MI and hypoxia models with mTORC1 phosphorylation, TFEB translocation, and autophagic flux readouts","pmids":["41741766"],"confidence":"Medium","gaps":["Single lab","Direct coupling of channel conductance to mTORC1/TFEB not mechanistically resolved"]},{"year":null,"claim":"It remains unresolved whether and under what physiological conditions TMEM175's proton conductance constitutes a functionally significant lysosomal H+ leak versus being a minor consequence of a fundamentally K+-conducting channel.","evidence":"Conflicting direct electrophysiology and structural studies on K+ vs H+ predominance","pmids":[],"confidence":"High","gaps":["Quantitative native H+ leak magnitude disputed","Conditions that switch the channel between ion modes undefined","Which conductance drives each disease phenotype unestablished"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,5,6,8,11,17]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,5,6,11]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[8,19]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[0,1,8,17]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[0,23]}],"pathway":[{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[0,1,7,24]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,8,17]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[20,22]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,3,26]}],"complexes":[],"partners":["BCL2","AKT1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BSA9","full_name":"Endosomal/lysosomal proton channel TMEM175","aliases":["Potassium channel TMEM175","Transmembrane protein 175","hTMEM175"],"length_aa":504,"mass_kda":55.6,"function":"Proton-activated proton channel that catalyzes proton efflux from endosomes and lysosomes to maintain a steady-state pH (PubMed:35333573, PubMed:35750034, PubMed:37390818). Activated at low pH (under pH 4.6) by luminal side protons: selectively mediates lysosomal proton release from lysosomes, eliciting a proton leak that balances V-ATPase activity to maintain pH homeostasis (PubMed:35750034). Regulation of lumenal pH stability is required for autophagosome-lysosome fusion (PubMed:26317472, PubMed:32267231). Also acts as a potassium channel at higher pH, regulating potassium conductance in endosomes and lysosomes (PubMed:26317472, PubMed:28723891, PubMed:32228865, PubMed:32267231, PubMed:33505021). Constitutes the pore-forming subunit of the lysoK(GF) complex, a complex activated by extracellular growth factors (PubMed:33505021). The lysoK(GF) complex is composed of TMEM175 and AKT (AKT1, AKT2 or AKT3), a major target of growth factor receptors: in the complex, TMEM175 channel is opened by conformational changes by AKT, leading to its activation (PubMed:33505021). The lysoK(GF) complex is required to protect neurons against stress-induced damage (PubMed:33505021)","subcellular_location":"Endosome membrane; Lysosome membrane","url":"https://www.uniprot.org/uniprotkb/Q9BSA9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TMEM175","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/TMEM175","total_profiled":1310},"omim":[{"mim_id":"616660","title":"TRANSMEMBRANE PROTEIN 175: TMEM175","url":"https://www.omim.org/entry/616660"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nuclear membrane","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TMEM175"},"hgnc":{"alias_symbol":["MGC4618"],"prev_symbol":[]},"alphafold":{"accession":"Q9BSA9","domains":[{"cath_id":"-","chopping":"255-478","consensus_level":"medium","plddt":88.9425,"start":255,"end":478},{"cath_id":"1.20.120","chopping":"30-59_73-228","consensus_level":"medium","plddt":90.2967,"start":30,"end":228}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BSA9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BSA9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BSA9-F1-predicted_aligned_error_v6.png","plddt_mean":81.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TMEM175","jax_strain_url":"https://www.jax.org/strain/search?query=TMEM175"},"sequence":{"accession":"Q9BSA9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BSA9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BSA9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BSA9"}},"corpus_meta":[{"pmid":"28193887","id":"PMC_28193887","title":"TMEM175 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Direct lysosomal patch-clamp recordings showed that lysosomes lacking TMEM175 exhibit no K+ conductance, have markedly depolarized membrane potential, little sensitivity to changes in [K+], and compromised luminal pH stability and abnormal fusion with autophagosomes during autophagy. Unlike canonical K+ channels, TMEM175 has two repeats of 6-transmembrane-spanning segments and lacks the GYG P-loop selectivity filter.\",\n      \"method\": \"Direct organelle patch-clamp electrophysiology; genetic knockout; lysosomal pH and autophagy assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct electrophysiological reconstitution in isolated lysosomes with genetic KO controls and multiple functional readouts; published in Cell and widely replicated\",\n      \"pmids\": [\"26317472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TMEM175 deficiency results in unstable lysosomal pH, decreased lysosomal catalytic activity, decreased glucocerebrosidase activity, impaired autophagosome clearance, and decreased mitochondrial respiration. In rat primary neurons, TMEM175 deficiency increased susceptibility to exogenous α-synuclein fibrils and caused increased phosphorylated and detergent-insoluble α-synuclein deposits.\",\n      \"method\": \"shRNA knockdown in neuronal model; lysosomal pH assays; cathepsin activity assays; GCase activity assay; mitochondrial respiration (Seahorse); α-synuclein fibril treatment with phospho-α-syn immunostaining\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal functional assays in neuronal model with defined phenotypic readouts; independently supported by subsequent studies\",\n      \"pmids\": [\"28193887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structure of prokaryotic TMEM175 (CmTMEM175) reveals a novel tetrameric architecture completely different from canonical K+ channels. All six transmembrane helices are tightly packed within each subunit without domain swapping. TM1 acts as the pore-lining inner helix creating an hourglass-shaped ion permeation pathway. Three layers of hydrophobic residues on TM1 form the selectivity filter; mutagenesis showed the first conserved isoleucine layer is primarily responsible for channel selectivity.\",\n      \"method\": \"X-ray crystallography of prokaryotic TMEM175; site-directed mutagenesis; electrophysiology\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and functional validation; foundational structural paper\",\n      \"pmids\": [\"28723891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The TMEM175 p.M393T variant (rs34311866) reduces lysosomal pH regulation in response to starvation, reduces lysosomal localization, and increases accumulation of phosphorylated α-synuclein with effects intermediate between WT and knockout. Overexpression of WT TMEM175 reduced p-α-syn, while overexpression of p.M393T did not change α-synuclein phosphorylation. shRNA knockdown of only TMEM175 (not neighboring genes) consistently influenced accumulation of phosphorylated α-synuclein.\",\n      \"method\": \"shRNA knockdown screen; variant overexpression; lysosomal pH assay; autophagy substrate clearance assay; phospho-α-syn immunostaining; lysosomal localization imaging\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (pH assay, localization, α-syn phosphorylation) in single lab; mechanistically informative variant characterization\",\n      \"pmids\": [\"31261387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The TMEM175 p.M393T variant creates a polar side-chain in the hydrophobic core of the transmembrane domain predicted to destabilize assembly, maturation, or trafficking, and is associated with reduced glucocerebrosidase (GCase) activity. Lysosomal localization of both p.M393T and p.Q65P variants was not affected. Molecular dynamics simulations suggested p.Q65P may increase stability and ion conductance.\",\n      \"method\": \"Homology modeling; normal mode analysis; molecular dynamics simulations; lysosomal localization experiments; GCase activity assay in patient cohort\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional localization experiment combined with computational modeling; GCase association in patient cohort; single lab\",\n      \"pmids\": [\"31658403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Cryo-EM structures of human TMEM175 in open and closed conformations (up to 2.6 Å resolution) reveal a homodimeric architecture with a central ion-conduction pore. Conserved isoleucine residues in the center of the pore serve as the gate in the closed conformation and establish a constriction essential for K+ selectivity in the open conformation.\",\n      \"method\": \"Cryo-EM structure determination; mutagenesis; electrophysiology\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution cryo-EM structures of both open and closed states with mutagenesis validation of gating and selectivity residues\",\n      \"pmids\": [\"32228865\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"X-ray structure of a closed bacterial TMEM175 channel in complex with a nanobody fusion-protein revealed bound K+ ions and a highly conserved layer of threonine residues in the pore that confers basal K+ selectivity. An additional layer comprising two serines in human TMEM175 increases selectivity further and renders the channel sensitive to 4-aminopyridine and Zn2+. Large hydrophobic side chains occlude the pore forming a physical gate; channel opening by iris-like motions simultaneously relocates the gate and exposes the selectivity filter.\",\n      \"method\": \"X-ray crystallography; electrophysiology; mutagenesis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with bound ions plus mutagenesis and electrophysiology; orthogonal to and consistent with cryo-EM studies\",\n      \"pmids\": [\"32267231\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TMEM175 deficiency in neurons inhibits lysosomal hydrolytic function by affecting lysosomal pH, impairs autophagosome-lysosome fusion, and leads to impaired mitochondrial accumulation (failure to clear damaged mitochondria). Exogenous upregulation of TMEM175 reversed OGD/R-induced lysosomal dysfunction in cultured neurons.\",\n      \"method\": \"Lysosomal pH assay (LysoSensor, acridine orange); cathepsin B and D activity assays; TMEM175 overexpression/knockdown in cultured neurons and in vivo MCAO/R model\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple lysosomal functional readouts with gain and loss of function in both in vitro and in vivo models; single lab\",\n      \"pmids\": [\"32799888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TMEM175 acts as a proton-activated, proton-selective channel (LyPAP) on the lysosomal membrane that mediates the lysosomal H+ leak. Acidification beyond the normal range (below pH 4.5–5.0) potently activated the channel to prevent further lysosomal acidification. An endogenous polyunsaturated fatty acid and synthetic agonists also activated TMEM175 to trigger lysosomal proton release. TMEM175 deficiency caused lysosomal over-acidification, impaired proteolytic activity, and facilitated α-synuclein aggregation in vivo. Mutational analysis showed the H+ conductance is essential for normal lysosome function.\",\n      \"method\": \"Lysosomal patch-clamp electrophysiology; ion substitution experiments; mutagenesis; lysosomal pH measurement; proteolytic activity assays; in vivo α-synuclein aggregation model\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct electrophysiology with mutagenesis and multiple functional assays including in vivo validation; published in Cell\",\n      \"pmids\": [\"35750034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Human TMEM175 exhibits pH-dependent structural changes: it constitutively conducts K+ at pH 7.4 but shows reduced K+ permeation at acidic pH, while proton current increases with decreasing pH. Molecular dynamics simulation, structure-based mutagenesis, and electrophysiology indicate K+ ions and protons share the same permeation pathway. The M393T PD-risk variant shows reduced function in both K+ and proton permeation.\",\n      \"method\": \"Cryo-EM structural analysis; whole-endolysosome patch-clamp electrophysiology; molecular dynamics simulations; site-directed mutagenesis\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure combined with mutagenesis, MD simulation, and electrophysiology in single study\",\n      \"pmids\": [\"35333573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Bcl-2 binds to and inhibits TMEM175 channel activity. Bcl-2 inhibitors activate TMEM175 in a caspase-independent manner. Increased TMEM175 function inhibits mitophagy, disrupts mitochondrial homeostasis, and increases reactive oxygen species (ROS) production. ROS further activates TMEM175, forming a positive feedback loop to augment apoptosis. In an MPTP mouse model of PD, TMEM175 knockout mitigated motor impairment and dopaminergic neuron loss.\",\n      \"method\": \"Co-immunoprecipitation (Bcl-2/TMEM175 binding); lysosomal patch-clamp; Bcl-2 inhibitor treatment; ROS measurement; mitophagy assay; TMEM175 KO mouse MPTP model with behavioral and histological readouts\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assay combined with electrophysiology, multiple cellular phenotype readouts, and in vivo KO model\",\n      \"pmids\": [\"35913019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Higher-resolution cryo-EM structures of open and closed human TMEM175 and molecular dynamics simulations demonstrate that the open-state pore is permeable to both K+ and (to a lesser degree) Na+. Both cations must dehydrate significantly to penetrate the narrow hydrophobic constriction, but ion flow is assisted by a favorable electrostatic field. The balance of ion dehydration energetics explains K+ selectivity over Na+ despite absence of a canonical selectivity filter. Mutagenesis experiments confirmed exquisite sensitivity of channel selectivity to perturbations that mitigate the constriction.\",\n      \"method\": \"Cryo-EM structure determination (higher resolution than prior); molecular dynamics simulations; mutagenesis; electrophysiology\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — improved-resolution cryo-EM with extensive MD simulation and mutagenesis validation of selectivity mechanism\",\n      \"pmids\": [\"35608336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Cryo-EM structure of TMEM175 bound to 4-aminopyridine (4-AP) shows that 4-AP binds near the center of the ion conduction pathway in the open state. MD simulations show the binding site is near the middle of the transmembrane potential gradient, explaining voltage-dependent dissociation. Bound 4-AP rapidly switches between three predominant binding poses stabilized by the twofold symmetry of the channel, and prevents both ion permeation and water flow.\",\n      \"method\": \"Cryo-EM structure of inhibitor-bound TMEM175; molecular dynamics simulations\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure of inhibitor-bound channel combined with MD simulations revealing mechanism of block\",\n      \"pmids\": [\"36279431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TMEM175 is regulated by protein kinase B (PKB/Akt) and dynamin-dependent endocytosis. Dynamin inhibitors (dynasore, dyngo-4a) substantially increased TMEM175 currents at the plasma membrane by preventing channel internalization. A constitutively active Akt mutant and the Akt activator SC79 increased TMEM175 current, while the allosteric Akt inhibitor MK2206 diminished it. TMEM175 is more permeable to cesium than potassium and is voltage-dependently blocked by 4-AP.\",\n      \"method\": \"Two-electrode voltage clamp in Xenopus oocytes; dominant-negative dynamin coexpression; immunocytochemistry for surface TMEM175; pharmacological Akt manipulation\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology combined with immunocytochemistry and pharmacological/genetic manipulation of Akt and dynamin; single lab\",\n      \"pmids\": [\"34638858\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TMEM175 mediates both lysosomal H+ influx (refilling) and H+ efflux (releasing) in an asymmetric manner. Using whole-endolysosome patch-clamp in enlarged lysosomes under physiological pH gradient, integrated lysosomal H+ flux signals were recorded. Loss-of-function F39V mutant and the antagonist 2-GBI abolished all lysosomal H+ fluxes. LAMP1 glycosylation modulates these H+ fluxes.\",\n      \"method\": \"Whole-endolysosome patch-clamp in vacuolin-1-enlarged lysosomes; TMEM175 loss-of-function mutant (F39V); pharmacological block (2-GBI); LAMP1 manipulation\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct organelle electrophysiology with genetic loss-of-function and pharmacological controls; single lab\",\n      \"pmids\": [\"37165739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Solid-supported membrane-based electrophysiology (SSME) of TMEM175 revealed two distinct conducting states (two-slope I/c curve for K+). H+ flux measurements yielded a permeability ratio PH/PK of ~48,500. Cytosolic pH decrease inhibited both K+ and H+ conductivity of TMEM175, while lysosomal-side pH changes did not have major effects. Tool compounds (4-AP, Zn2+ as inhibitors; DCPIB, arachidonic acid, SC-79 as enhancers) were validated across multiple assay formats.\",\n      \"method\": \"Solid-supported membrane-based electrophysiology (SSME); automated whole-cell patch-clamp (APC); lysosomal patch-clamp (LPC); pharmacological profiling\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple electrophysiology platforms with pharmacological cross-validation; single study but orthogonal methods\",\n      \"pmids\": [\"37628970\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structures of human TMEM175 bound to selective inhibitors 2-PPA and AP-6 reveal that they act as pore blockers, binding at distinct sites in the pore and occluding the ion permeation pathway. Acute inhibition by these inhibitors increases lysosomal macromolecule catabolism, accelerating macropinocytosis and other digestive processes.\",\n      \"method\": \"Cryo-EM structure of inhibitor-bound TMEM175; lysosomal catabolism assays; macropinocytosis assay\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures of two distinct inhibitor-bound states with functional lysosomal activity readouts\",\n      \"pmids\": [\"39116214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Rigorous re-examination found that in the lysosome, TMEM175 predominantly conducts K+ and is not a H+-selective channel. The native lysosomal H+ leak is ~0.02 fA, which is remarkably small and argues strongly against major H+ channel contributions. The predominant effect of TMEM175 deficiency is lysosomal alkalinization in challenged cells (not over-acidification), which is consistent with K+ conductance through TMEM175. Lysosomes can be hyper-acidified by manipulations in the presence or absence of TMEM175.\",\n      \"method\": \"Lysosomal patch-clamp electrophysiology; lysosomal pH measurement; genetic manipulation of TMEM175; ion substitution experiments\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct quantitative electrophysiology with rigorous controls challenging prior proton-channel model; published in JCB with editorial commentary; multiple independent lines of evidence\",\n      \"pmids\": [\"41134537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structures of human TMEM175 in complex with three agonists (DCY1020, DCY1040, TUG-891) captured an open state of the channel. DCY1020/1040 binds at the interface between two subunits, inducing an open conformation further augmented by synergistic agonist TUG-891. Surface plasmon resonance, systematic mutagenesis, whole-endolysosome patch-clamp, and MD simulations validated the binding sites. These agonists facilitate removal of pathological α-synuclein and restore function of PD-related TMEM175 variants in neurons.\",\n      \"method\": \"Cryo-EM structure; surface plasmon resonance; mutagenesis; whole-endolysosome patch-clamp; molecular dynamics simulations; α-synuclein clearance assay in neurons\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures of agonist-bound open state combined with SPR, mutagenesis, electrophysiology, MD simulations, and functional cellular assays in single study\",\n      \"pmids\": [\"40865534\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Luminal-side H57 residue acts as a proton sensor critical for proton-selective gating of TMEM175. A pH drop from 7.4 to 4.7 on the luminal side triggers increased inward and outward currents with a transient shift in reversal potential toward H+ equilibrium voltage. H57 forms intra- and inter-subunit salt bridges with D279 and E282, stabilizing the open state. The H57Y mutant shows reduced H+ and K+ conductance and reduced H+/K+ selectivity, confirmed by both whole-cell and lysosomal electrophysiology.\",\n      \"method\": \"Whole-cell patch-clamp (plasma membrane redistributed TMEM175); lysosomal patch-clamp; molecular dynamics simulations; site-directed mutagenesis (H57Y); reversal potential measurements\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis combined with MD simulations and two independent electrophysiology formats (whole-cell and lysosomal patch-clamp)\",\n      \"pmids\": [\"41533442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TMEM175 conditional knockout in macrophages promotes anti-tumor immunity through elevated M1-like polarization, reduced M2-like polarization, and facilitated recruitment/activation of T cells and NK cells. The anti-tumor effect is abrogated by caspase-1 inhibitor VX-765, anti-IL-1β, and anti-IL-18. Tmem175-/- BMDMs show enhanced tumor antigen cross-presentation strengthened by IL-1β and IL-18. NLRP3 inflammasome is robustly activated in Tmem175-/- BMDMs via lysosomal permeabilization and cathepsin B leakage.\",\n      \"method\": \"Conditional macrophage-specific TMEM175 KO mouse; tumor growth/metastasis models; BMDM in vitro assays; caspase-1 inhibitor; neutralizing antibodies; cross-presentation assay; NLRP3 activation assay; cathepsin B leakage measurement\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with multiple mechanistic readouts (inflammasome, cross-presentation, cathepsin B), pharmacological validation, and in vivo tumor models\",\n      \"pmids\": [\"41690940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TMEM175 deficiency in bone marrow-derived mesenchymal stem cells (BMSCs) suppresses osteoblast differentiation as evidenced by decreased matrix mineralization and lower expression of osteoblast marker genes. TMEM175 deficiency leads to lysosomal dysfunction and partially impairs autophagic clearance during osteoblast differentiation. The TMEM175 inhibitor 4-AP decreased osteoblast differentiation of BMSCs.\",\n      \"method\": \"TMEM175 knockdown in BMSCs; osteoblast differentiation assay (matrix mineralization, marker gene expression); lysosomal pH and function assays; autophagic flux measurement; 4-AP pharmacological inhibition\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KD and pharmacological inhibition with multiple functional readouts; single lab\",\n      \"pmids\": [\"39426687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"TMEM175 activity in macrophages maintains lysosomal pH and prevents cholesterol accumulation. In BK channel-deficient (BK-/-) macrophages, TMEM175 is upregulated as a compensatory mechanism to maintain lysosomal function. Inhibition of TMEM175 activity in both BK-/- and WT macrophages increased lysosomal pH and reduced silica-induced cell death and IL-1β release, indicating TMEM175 regulates silica-induced inflammatory responses through lysosomal pH control.\",\n      \"method\": \"BK-/- mouse BMDM; TMEM175 inhibitor treatment; lysosomal pH assay; cholesterol accumulation assay; IL-1β measurement; cell death assay\",\n      \"journal\": \"Inhalation toxicology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition with lysosomal functional and inflammatory readouts in KO background; single lab\",\n      \"pmids\": [\"40402504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DABMA activates the endosomal TMEM175 channel with an EC50 of 17.9 μM as measured by organelle patch-clamp. Depletion of TMEM175 significantly decreases the antitoxin activity of DABMA and affects its action on acidic/Rab7-positive endosomes and endolysosomal trafficking, demonstrating that TMEM175 is necessary for DABMA's anti-pathogen activity.\",\n      \"method\": \"Organelle patch-clamp electrophysiology (EC50 determination); TMEM175 protein depletion; endosomal pH and Rab7 imaging; endolysosomal trafficking assays\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiology combined with genetic depletion and functional trafficking assays; single lab\",\n      \"pmids\": [\"39097908\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"TMEM175 overexpression in cardiomyocytes confers cardioprotection after myocardial infarction by restoring lysosomal function (biogenesis, normalized pH, enzyme activities, and autophagic flux). Mechanistically, TMEM175 reduction caused by MI increases mTORC1 phosphorylation on lysosomal membranes and suppresses nuclear translocation of transcription factor EB (TFEB), impairing TFEB's transcriptional regulation of lysosome-associated genes. TMEM175 restoration reverses this cascade.\",\n      \"method\": \"Gain and loss of function in vivo MI model and in vitro hypoxia model; lysosomal pH/enzyme activity/biogenesis assays; mTORC1 phosphorylation measurement; TFEB nuclear translocation imaging; autophagic flux assay\",\n      \"journal\": \"Acta pharmacologica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss of function with mechanistic readouts (mTORC1, TFEB) in both in vitro and in vivo models; single lab\",\n      \"pmids\": [\"41741766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Mutagenesis identified T119 and H449 as structural determinants of TMEM175 activation gating. T119A and H449A mutations decreased apparent potencies of multiple TMEM175 activators (DCPIB, zafirlukast, montelukast). The T119A mutation produced a constitutively open channel phenotype. CysLT1 receptor antagonists (zafirlukast, montelukast, pranlukast) directly activate TMEM175 independently of CysLT1R, and DCPIB/zafirlukast activate TMEM175 independently of AKT, while montelukast activation is partially AKT-dependent.\",\n      \"method\": \"High-throughput screening; fluorescence assays; automated patch-clamp; mutagenesis (T119A, H449A); AKT inhibitor (MK2206) treatment; computational modeling\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis combined with electrophysiology and pharmacological characterization; multiple activators tested; single lab\",\n      \"pmids\": [\"41670588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Functional analysis of novel TMEM175 mutations identified in PD patients (including p.R35C, p.R183X, p.A270T, p.P308L, p.S348L, p.L405V, p.R414W, p.P427fs, p.R481W) revealed loss of K+ conductance by patch-clamp and reduced channel affinity for Akt by co-immunoprecipitation. Patient-derived fibroblasts showed impaired autophagic/lysosomal proteolytic flux and increased unfolded protein response markers.\",\n      \"method\": \"Patch-clamp electrophysiology; co-immunoprecipitation (TMEM175-Akt); autophagic flux assay; UPR marker measurement in patient-derived fibroblasts\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiology and binding assay in patient-derived cells; single lab; multiple mutations tested\",\n      \"pmids\": [\"36609826\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TMEM175 is a non-canonical lysosomal/endosomal cation channel that forms a homodimer (or prokaryotic tetramer) with a novel 6-TM architecture lacking the canonical TVGYG selectivity filter; it primarily conducts K+ through a hydrophobic isoleucine constriction that simultaneously gates and selects ions, maintains lysosomal membrane potential and luminal pH stability, regulates autophagosome-lysosome fusion, and is activated by Akt/PKB and inhibited by Bcl-2, with loss of function causing lysosomal alkalinization, impaired proteolysis, glucocerebrosidase deficiency, mitochondrial dysfunction, and α-synuclein accumulation relevant to Parkinson's disease pathogenesis; the channel also conducts protons through the same pore (with H57 as a key proton-sensing gating residue), though whether this H+ conductance constitutes a major H+ leak pathway remains actively debated.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TMEM175 is a non-canonical lysosomal and endosomal cation channel that sets the ionic and pH environment of the late endo-lysosomal system and thereby controls autophagy, organelle catabolism, and protein quality control [#0, #1]. Rather than the canonical TVGYG selectivity filter, it uses a novel architecture — a homodimer of two 6-transmembrane repeats in eukaryotes (a tetramer in prokaryotes) — in which TM1 lines an hourglass-shaped pore, and layers of hydrophobic isoleucine residues simultaneously form the gate and the K+ selectivity constriction; threonine and serine layers add to selectivity and confer sensitivity to 4-aminopyridine and Zn2+, and channel opening occurs through iris-like helical motions that relocate the gate and expose the filter [#2, #5, #6, #11]. K+ and Na+ permeation is governed by ion-dehydration energetics through the narrow constriction rather than a structured filter, explaining selectivity in the absence of a P-loop [#11]. The channel maintains lysosomal membrane potential and luminal pH stability; loss of function destabilizes lysosomal pH, reduces cathepsin and glucocerebrosidase activity, impairs autophagosome-lysosome fusion and autophagic clearance, and depresses mitochondrial respiration, with the predominant pH consequence in challenged cells being alkalinization consistent with K+ conductance [#0, #1, #17]. These defects drive accumulation of phosphorylated, detergent-insoluble α-synuclein, and TMEM175 deficiency or the common p.M393T risk variant — which destabilizes the protein and reduces both K+ and proton permeation — link the channel to Parkinson's disease pathogenesis [#1, #3, #9, #26]. TMEM175 activity is regulated by Akt/PKB and dynamin-dependent endocytosis and is inhibited by Bcl-2 binding, coupling channel gating to survival signaling and mitochondrial homeostasis [#10, #13]. Beyond neurons, TMEM175 governs lysosomal pH in macrophages, where its loss triggers NLRP3 inflammasome activation via cathepsin B leakage, and supports osteoblast differentiation and cardiomyocyte lysosomal function through TFEB-dependent biogenesis [#10, #20, #21, #24]. Whether TMEM175 additionally functions as a proton-selective channel mediating a major lysosomal H+ leak is actively debated: direct proton-conduction with H57 as a luminal proton-sensing gating residue has been reported [#8, #19], while rigorous quantitative re-examination found K+ to be the predominant conducted ion and the native H+ leak negligible [#17].\",\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Established the founding identity of TMEM175 as the major lysosomal/endosomal K+ channel and tied it to a basic organelle function, answering whether an uncharacterized membrane protein carried lysosomal K+ conductance.\",\n      \"evidence\": \"Direct lysosomal patch-clamp with genetic knockout plus pH and autophagy assays\",\n      \"pmids\": [\"26317472\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of selectivity without a GYG filter unresolved\", \"Channel structure unknown\", \"Physiological gating cues not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected channel loss to a defined disease-relevant cascade, showing that TMEM175 deficiency degrades lysosomal proteolysis, GCase activity, and mitochondrial respiration and sensitizes neurons to α-synuclein pathology.\",\n      \"evidence\": \"shRNA knockdown in neurons with pH, cathepsin, GCase, Seahorse, and phospho-α-syn readouts\",\n      \"pmids\": [\"28193887\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal chain from pH change to α-syn aggregation not dissected\", \"In vivo relevance untested at this stage\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Solved the first structure, revealing a unique tetrameric architecture with TM1-lined pore and hydrophobic isoleucine selectivity layers — explaining how a channel selects K+ without a canonical filter.\",\n      \"evidence\": \"X-ray crystallography of prokaryotic CmTMEM175 with mutagenesis and electrophysiology\",\n      \"pmids\": [\"28723891\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Prokaryotic; human dimeric architecture not yet confirmed\", \"Open vs closed states not both captured\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Characterized the common p.M393T Parkinson's risk variant mechanistically, showing intermediate loss of pH regulation, reduced GCase, and increased α-syn phosphorylation, linking a genetic risk allele to channel dysfunction.\",\n      \"evidence\": \"Variant overexpression, knockdown specificity, pH/localization assays, computational modeling, patient GCase cohort\",\n      \"pmids\": [\"31261387\", \"31658403\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Discordant reports on whether localization is affected\", \"Quantitative effect on conductance not measured here\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the human channel in open and closed states and pinpointed the isoleucine gate and selectivity constriction plus threonine/serine selectivity layers and pharmacological sensitivities, providing an atomic gating model.\",\n      \"evidence\": \"Cryo-EM and X-ray structures of human and bacterial channel with bound ions, mutagenesis, and electrophysiology\",\n      \"pmids\": [\"32228865\", \"32267231\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Energetics of selectivity not quantified\", \"Physiological gating trigger in lysosome unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended the lysosomal dysfunction phenotype to mitophagy and ischemic injury, showing TMEM175 deficiency impairs damaged-mitochondria clearance and that overexpression rescues OGD/R-induced lysosomal failure.\",\n      \"evidence\": \"pH, cathepsin assays, gain/loss of function in neurons and MCAO/R model\",\n      \"pmids\": [\"32799888\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Direct link between channel conductance and mitophagy unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified upstream regulation by Akt/PKB signaling and dynamin-dependent endocytosis, explaining how channel surface density and activity are dynamically controlled.\",\n      \"evidence\": \"Two-electrode voltage clamp in oocytes, dominant-negative dynamin, surface immunocytochemistry, Akt pharmacology\",\n      \"pmids\": [\"34638858\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct Akt phosphorylation site not mapped here\", \"Oocyte/plasma-membrane context differs from lysosome\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Proposed a second permeation function — proton-activated, proton-selective conductance mediating the lysosomal H+ leak that prevents over-acidification — reframing TMEM175 as a pH-protective channel.\",\n      \"evidence\": \"Lysosomal patch-clamp, ion substitution, mutagenesis, PUFA/agonist activation, in vivo α-syn model\",\n      \"pmids\": [\"35750034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Magnitude of physiological H+ leak contested\", \"Reconciliation with predominant K+ conductance unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed K+ and protons share one permeation pathway with pH-dependent structural switching, and that M393T reduces both conductances, unifying the K+ and H+ activities in a single pore.\",\n      \"evidence\": \"Cryo-EM, whole-endolysosome patch-clamp, MD simulation, mutagenesis\",\n      \"pmids\": [\"35333573\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative physiological contribution of each ion not settled\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the biophysical basis of K+-over-Na+ selectivity as dehydration energetics assisted by a favorable electrostatic field, explaining selectivity without a structured filter.\",\n      \"evidence\": \"Higher-resolution cryo-EM, extensive MD simulation, mutagenesis, electrophysiology\",\n      \"pmids\": [\"35608336\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In situ ionic conditions modeled, not directly measured\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified Bcl-2 as a direct inhibitory binding partner and embedded TMEM175 in a ROS/apoptosis feedback loop, and showed knockout is protective in an MPTP Parkinson's model.\",\n      \"evidence\": \"Co-IP, lysosomal patch-clamp, Bcl-2 inhibitors, ROS/mitophagy assays, TMEM175 KO MPTP mouse\",\n      \"pmids\": [\"35913019\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Bcl-2 binding interface not mapped structurally\", \"Direction of net Parkinson's effect (loss vs gain) context-dependent\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Mapped the binding site and voltage-dependent block mechanism of the classic inhibitor 4-aminopyridine within the open pore.\",\n      \"evidence\": \"Cryo-EM of inhibitor-bound channel with MD simulations\",\n      \"pmids\": [\"36279431\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Therapeutic selectivity not addressed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Characterized a panel of PD-patient mutations as loss-of-K+-conductance alleles with reduced Akt affinity and downstream autophagic/UPR defects, strengthening the genetic-functional link to Parkinson's.\",\n      \"evidence\": \"Patch-clamp, TMEM175-Akt co-IP, autophagic flux and UPR markers in patient fibroblasts\",\n      \"pmids\": [\"36609826\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Causality of UPR vs lysosomal defect not separated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Quantified asymmetric bidirectional H+ flux and a high PH/PK permeability ratio, and showed cytosolic-side (not luminal-side) pH and LAMP1 glycosylation modulate conductance.\",\n      \"evidence\": \"Whole-endolysosome and solid-supported-membrane electrophysiology with loss-of-function mutants and pharmacology\",\n      \"pmids\": [\"37165739\", \"37628970\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"High PH/PK ratio later contested by quantitative leak measurements\", \"LAMP1 modulation mechanism unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established TMEM175 as a tractable drug target, defining cryo-EM-resolved pore-blocker sites whose acute inhibition paradoxically accelerates lysosomal catabolism and macropinocytosis.\",\n      \"evidence\": \"Cryo-EM of 2-PPA/AP-6-bound states with catabolism and macropinocytosis assays\",\n      \"pmids\": [\"39116214\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which channel block enhances catabolism not fully explained\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the channel's roles beyond neurons, showing TMEM175 is required for osteoblast differentiation and for an antitoxin compound's endosomal action, demonstrating tissue-broad lysosomal/endosomal functions.\",\n      \"evidence\": \"Knockdown/4-AP in BMSCs with differentiation and autophagy assays; organelle patch-clamp EC50 and depletion with trafficking assays for DABMA\",\n      \"pmids\": [\"39426687\", \"39097908\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single labs\", \"Direct molecular link between channel activity and differentiation/trafficking phenotypes incomplete\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Rigorously re-examined the proton hypothesis and concluded TMEM175 predominantly conducts K+ with a negligible native H+ leak, and that deficiency causes alkalinization rather than over-acidification — directly challenging the proton-channel model.\",\n      \"evidence\": \"Quantitative lysosomal patch-clamp, pH measurement, genetic manipulation, ion substitution\",\n      \"pmids\": [\"41134537\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reconciliation with prior proton-conduction structural/electrophysiology reports unresolved\", \"Conditions under which H+ conductance becomes relevant undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified luminal H57 as a proton-sensing gating residue forming salt bridges that stabilize the open state, providing a structural mechanism for proton-dependent gating.\",\n      \"evidence\": \"H57Y mutagenesis, MD simulations, whole-cell and lysosomal patch-clamp, reversal-potential measurements\",\n      \"pmids\": [\"41533442\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological relevance of proton gating debated given small native leak\", \"Does not resolve K+ vs H+ predominance controversy\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Captured agonist-bound open states and defined activation determinants, demonstrating that small-molecule activators can restore PD-variant function and clear pathological α-synuclein in neurons — a therapeutic proof of concept.\",\n      \"evidence\": \"Cryo-EM with SPR, mutagenesis (T119/H449), patch-clamp, MD, and α-syn clearance assays; pharmacological characterization of CysLT antagonist activators\",\n      \"pmids\": [\"40865534\", \"41670588\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo efficacy of agonists not established here\", \"Relationship of activation to K+ vs H+ conductance not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined an immune and inflammatory role: macrophage TMEM175 loss activates the NLRP3 inflammasome via cathepsin B leakage, promoting anti-tumor immunity, while channel activity restrains silica-induced inflammation through lysosomal pH control.\",\n      \"evidence\": \"Conditional macrophage KO tumor models, BMDM inflammasome/cross-presentation/cathepsin B assays; BK-/- BMDM with inhibitor and IL-1β readouts\",\n      \"pmids\": [\"41690940\", \"40402504\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether immune effects derive from K+ or H+ conductance unclear\", \"Therapeutic window between neuroprotection and inflammasome activation undefined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Linked TMEM175 to cardiac protection via a lysosome-mTORC1-TFEB biogenesis axis, showing channel restoration reverses post-infarction lysosomal failure.\",\n      \"evidence\": \"Gain/loss of function in MI and hypoxia models with mTORC1 phosphorylation, TFEB translocation, and autophagic flux readouts\",\n      \"pmids\": [\"41741766\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Direct coupling of channel conductance to mTORC1/TFEB not mechanistically resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved whether and under what physiological conditions TMEM175's proton conductance constitutes a functionally significant lysosomal H+ leak versus being a minor consequence of a fundamentally K+-conducting channel.\",\n      \"evidence\": \"Conflicting direct electrophysiology and structural studies on K+ vs H+ predominance\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative native H+ leak magnitude disputed\", \"Conditions that switch the channel between ion modes undefined\", \"Which conductance drives each disease phenotype unestablished\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 5, 6, 8, 11, 17]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 5, 6, 11]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [8, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [0, 1, 8, 17]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [0, 23]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [0, 1, 7, 24]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 8, 17]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [20, 22]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 3, 26]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"BCL2\", \"AKT1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}