{"gene":"PTCH1","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2019,"finding":"Cryo-EM structure of human PTCH1 bound to a palmitoylated Sonic hedgehog ligand (ShhNC24II) at 3.4 Å resolution reveals that the membrane-embedded region of PTCH1 is surrounded by 10 sterol molecules at the inner and outer lipid bilayer; these annular sterols interact with both the sterol-sensing domain (SSD) and the SSD-like domain (SSDL) on opposite sides of PTCH1, suggesting a route for sterol translocation across the lipid bilayer.","method":"Cryo-EM structure determination (3.4 Å resolution) with structural analysis of sterol binding sites","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Strong — near-atomic resolution cryo-EM structure with direct identification of sterol interaction sites; rigorous structural data from a single focused study","pmids":["31555730"],"is_preprint":false},{"year":2004,"finding":"PTCH1 is transcriptionally regulated by three independent promoters generating transcripts with alternative first exons. Only one of two putative Gli-binding sites in the promoter region is functional; GLI1, GLI2, and GLI3 bind and activate transcription through this single site. Upstream pathway components SHH and SMO operate exclusively through this functional Gli-binding site, as mutation of it abolishes enhanced transcription induced by Gli proteins, SHH, or SMO.","method":"Promoter-reporter assays, electrophoretic mobility shift assay (EMSA), site-directed mutagenesis of Gli-binding sites, transfection with truncated GLI3","journal":"Gene","confidence":"High","confidence_rationale":"Tier 1 / Moderate — functional mutagenesis of binding site combined with reporter assays and multiple pathway components tested; single lab with multiple orthogonal methods","pmids":["15087129"],"is_preprint":false},{"year":2002,"finding":"PTCH1 encodes multiple isoforms arising from alternative first exons (exon 1, 1A, 1B). All PTCH1 isoforms interact with SMOH in co-transfected cells and can inhibit SHH activity. However, only the PTCH1B isoform fully inhibits SMOH signaling, while other isoforms cannot; the N-terminal region encoded by exon 1B is required for complete SMOH inhibition but not for physical interaction with SMOH.","method":"Co-immunoprecipitation (doubly transfected cells), functional luciferase reporter assays (SHH and SMO inhibition), RT-PCR of tissue expression","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction and functional assays in same study; single lab with two orthogonal methods","pmids":["12203113"],"is_preprint":false},{"year":2004,"finding":"A missense mutation in the sterol-sensing domain of patched (G509V, equivalent in Drosophila ptc) acts as a dominant negative in vivo in Drosophila: ectopic expression causes ectopic activation of Hedgehog target genes and ectopic membrane stabilization of Smoothened. Unlike a C-terminal truncation dominant-negative (which localizes to plasma membrane), G509V shows vesicular localization identical to wild-type, indicating that dominant-negative function can result from disruption of different aspects of Patched protein behavior. A different mutation at the same residue (G509R) did not show dominant-negative activity.","method":"In vivo Drosophila transgenic expression, immunofluorescence localization, genetic analysis of Hh target gene activation","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo functional assay with mutagenesis comparisons in Drosophila ortholog; single lab, multiple mutations tested","pmids":["15042702"],"is_preprint":false},{"year":2015,"finding":"In the vertebrate neural tube, Ptch1 transcriptional upregulation (via Shh-induced Gli activity) contributes to adaptation/attenuation of Shh pathway output over time, alongside Gli2 protein downregulation and differential stability of Gli isoforms. Adaptation continues when the pathway is stimulated downstream of Ptch1, indicating that Ptch1 upregulation is one of multiple mechanisms controlling intracellular Shh signaling dynamics.","method":"Quantitative immunofluorescence of Shh gradient in mouse neural tube, computational modeling, Gli2 protein expression analysis, pathway stimulation downstream of Ptch1 in NIH3T3 cells","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo quantitative measurements combined with computational modeling and cell-based pathway perturbation; single lab, multiple orthogonal methods","pmids":["25833741"],"is_preprint":false},{"year":2014,"finding":"In Ptch1-/- cells, Shh signaling remains ligand-dependent: the Shh-blocking antibody 5E1 inhibits the response in Ptch1-/- cells, and Ptch1-/-;Ptch2-/- double knockout cells cannot further activate the Shh response beyond Ptch1-/- alone. Expression of a dominant-negative Ptch2 (but not dominant-negative Ptch1) in the developing chick neural tube activates the Shh response, demonstrating that Ptch2 mediates the Shh response in the absence of Ptch1 at early developmental stages.","method":"Genetic knockout cells (Ptch1-/-, Ptch1-/-;Ptch2-/-), Shh-blocking antibody (5E1), dominant-negative constructs in chick neural tube in ovo electroporation, migration assays","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genetic approaches (double KO, dominant-negative, antibody blocking) in two model systems; rigorous epistasis analysis","pmids":["25085974"],"is_preprint":false},{"year":2018,"finding":"PTCH1 functions as a multidrug efflux transporter that pumps chemotherapeutic agents such as doxorubicin out of cancer cells using the proton motive force (reversed pH gradient in cancer cells), unlike ABC transporters which use ATP hydrolysis. Inhibition of Ptch1 drug efflux activity enhances cytotoxicity of chemotherapeutics in cancer cell lines overexpressing Ptch1, and in vivo combination with doxorubicin prevented xenografted adrenocortical carcinoma tumor development.","method":"Drug efflux assays in cancer cell lines, chemical library screening for Ptch1 inhibitors, in vivo xenograft mouse model with doxorubicin combination treatment","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based efflux assays and in vivo proof-of-concept; single lab, multiple methods including in vitro and in vivo","pmids":["30110910"],"is_preprint":false},{"year":2005,"finding":"In heterozygous Ptch1 knockout mouse tumors, the wild-type Ptch1 allele is transcriptionally silenced (via promoter methylation sensitivity), while the mutant allele is predominantly expressed. This mutant Ptch1-derived protein is incapable of pathway inhibition. Transcriptional silencing of one Ptch1 allele followed by mutation of the other (or vice versa) constitutes a mechanism of PTCH1/Ptch1 tumor suppressor inactivation that explains retention of one allele in many tumors.","method":"Allele-specific RT-PCR in Ptch1+/- mouse tumors, promoter methylation-reporter assays, functional pathway inhibition assays","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — allele-specific expression analysis in mouse tumors combined with promoter methylation functional assay; single lab, two orthogonal methods","pmids":["16273213"],"is_preprint":false},{"year":2009,"finding":"In heterozygous Ptch1 knockout mice, epigenetic silencing of the intact (wild-type) Ptch1 allele via DNA methylation contributes to tumor formation. Reducing Dnmt1 activity significantly reduced tumor incidence. Combined treatment with the DNA methyltransferase inhibitor 5-aza-dC and the HDAC inhibitor valproic acid reactivated wild-type Ptch1 expression (associated with reduced Ptch1 promoter methylation and histone hyperacetylation) and efficiently prevented medulloblastoma and rhabdomyosarcoma formation.","method":"Genetic reduction of Dnmt1 in Ptch1+/- mice, pharmacological treatment (5-aza-dC + VPA) in vivo, promoter methylation analysis, chromatin immunoprecipitation (histone acetylation)","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic and pharmacological evidence with molecular mechanistic readouts; single lab, multiple orthogonal methods","pmids":["19155313"],"is_preprint":false},{"year":2013,"finding":"MeCP2 (methyl-CpG-binding protein 2) mediates silencing of PTCH1 via DNA methylation in hepatic stellate cells. Hypermethylation of the PTCH1 promoter is associated with HSC activation and liver fibrogenesis. siRNA knockdown of MeCP2 increased PTCH1 mRNA and protein expression in hepatic myofibroblasts, and 5-aza-dC treatment prevented loss of PTCH1 expression during HSC activation.","method":"siRNA knockdown of MeCP2, bisulfite sequencing/MSP of PTCH1 promoter, 5-aza-dC treatment, RT-PCR and Western blot","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown with multiple molecular readouts (methylation, mRNA, protein); single lab","pmids":["23333245"],"is_preprint":false},{"year":2017,"finding":"MeCP2 reduces PTCH1 expression in fibroblast-like synoviocytes of adjuvant arthritis rats through promoter hypermethylation. Knockdown of MeCP2 by siRNA increased PTCH1 expression, which in turn inhibited Hedgehog signaling (decreased Gli1 and Shh) and reduced secretion of inflammatory cytokines IL-6 and TNF-α.","method":"siRNA knockdown of MeCP2, methylation-specific PCR, RT-PCR, Western blot, cytokine measurement (ELISA)","journal":"Inflammation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA knockdown with methylation and functional downstream pathway readouts; single lab, replicated MeCP2-PTCH1 axis from independent group","pmids":["28573530"],"is_preprint":false},{"year":2014,"finding":"PTCH53 (PTCHD4), a p53 target gene homologous to PTCH1, is transcriptionally activated by p53 in response to DNA damage and can repress Hedgehog pathway activation by inhibiting canonical signaling by the GPCR SMO, delineating a novel inducible pathway by which p53 represses Hh signals. (Note: this is about PTCH53/PTCHD4, not PTCH1 itself, but the paper defines functional relationship of PTCH1 homology.)","method":"Luciferase reporter assays, quantitative RT-PCR in TP53-mutant cell lines and human tumors, SMO inhibition assays","journal":"The Journal of biological chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pertains primarily to PTCH53/PTCHD4 (a homolog), not PTCH1 itself; indirect relevance to PTCH1 mechanism","pmids":["25296753"],"is_preprint":false},{"year":2020,"finding":"The G protein-coupled receptor Gpr37l1 interacts with Ptch1 at peri-ciliary membranes in cerebellar astrocytes. In Gpr37l1-/- astrocytes, Ptch1 protein expression and internalization are markedly increased, intracellular cholesterol content rises, ciliary localization of Smo increases, and Shh production is markedly elevated, along with increased astrocyte proliferation. These findings indicate that Gpr37l1 specifically regulates Ptch1 internalization/trafficking, with consequent effects on Shh production and downstream proliferative signaling.","method":"Gpr37l1 null mutant mouse cerebellar primary astrocyte cultures, immunofluorescence of Ptch1 and Smo localization, cholesterol measurement, Shh production quantification, proliferation assays","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO model with multiple cellular and molecular readouts; single lab, multiple orthogonal methods","pmids":["33350496"],"is_preprint":false},{"year":2011,"finding":"In CLL cells with trisomy 12, constitutive Hedgehog pathway activation is driven by autocrine Desert Hedgehog (DHH) ligand secretion, which activates pathway signaling through PTCH1. BM stromal cell-derived DHH activates a non-canonical ERK phosphorylation pathway directly downstream of the PTCH1 receptor without involvement of SMO, conferring resistance to SMO inhibitors; this could be overcome by the HH-blocking antibody 5E1 or combination of SMO and ERK inhibitors.","method":"SMO inhibitor treatment of CLL cells, HH-blocking antibody (5E1), co-culture experiments with DHH-expressing BM stromal cells, phospho-ERK Western blot, GLI1/PTCH1 transcript quantification","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional antibody blocking and pharmacological epistasis establishing non-canonical PTCH1→ERK signaling; single lab, multiple orthogonal methods","pmids":["22130798"],"is_preprint":false},{"year":2020,"finding":"PTCH1 promotes anchorage-independent (spheroid) growth, migration, and invasion of non-small cell lung cancer cells, associated with expression of MMP7 and SOX2. shRNA-mediated PTCH1 knockdown reduced spherical colony formation, migration, and invasion in vitro, and decreased bone destruction and osteoclastogenesis in a mouse bone metastasis model in vivo.","method":"Lentiviral shRNA knockdown of PTCH1, spheroid colony formation assay, migration/invasion assays, mouse bone metastasis model, Western blot (MMP7, SOX2)","journal":"Bone","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined cellular phenotype in vitro and in vivo; single lab, multiple readouts","pmids":["33359005"],"is_preprint":false},{"year":2018,"finding":"miR-155 directly targets the 3'UTR of PTCH1 mRNA (validated by dual-luciferase reporter assay) and downregulates PTCH1 mRNA and protein expression. miR-155-mediated PTCH1 downregulation worsens high glucose-induced endothelial progenitor cell dysfunction (reduced viability, migration, tube formation, NO production; increased apoptosis and ROS); silencing PTCH1 by siRNA abrogated the protective effect of anti-miR-155.","method":"Dual-luciferase reporter assay, miR-155 overexpression/inhibition, PTCH1 siRNA knockdown, cell viability, migration, tube formation, NO, apoptosis, and ROS assays","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct 3'UTR targeting validated by luciferase assay with functional rescue experiment; single lab","pmids":["29545091"],"is_preprint":false}],"current_model":"PTCH1 is a twelve-transmembrane receptor for Sonic Hedgehog (SHH) ligands that normally inhibits Smoothened (SMO) through a sterol-transport mechanism (structurally defined by cryo-EM showing 10 annular sterols interacting with its sterol-sensing domain); SHH binding to PTCH1 relieves SMO inhibition to activate Gli transcription factors, while PTCH1 itself is a transcriptional target of Gli proteins acting through a single functional Gli-binding site, creating a negative feedback loop. PTCH1 additionally functions as a proton-motive-force-driven multidrug efflux transporter in cancer cells, and its internalization and trafficking are regulated by the co-receptor Gpr37l1, with loss of PTCH1 function achievable through mutational inactivation, promoter hypermethylation (mediated by MeCP2), or epigenetic silencing, all of which constitutively activate downstream Hh signaling."},"narrative":{"mechanistic_narrative":"PTCH1 is the receptor that sets the threshold of Hedgehog (Hh) pathway activity, controlling developmental patterning and acting as a tumor suppressor by restraining downstream signaling [PMID:25085974, PMID:16273213]. Its membrane-embedded core is encircled by annular sterols that engage both a sterol-sensing domain (SSD) and an SSD-like domain on opposite faces of the protein, defining a route for sterol translocation across the bilayer that underlies its capacity to inhibit Smoothened (SMO) [PMID:31555730]. PTCH1 physically associates with SMO and inhibits its signaling; an isoform-specific N-terminal region (exon 1B) is required for full SMO inhibition but is dispensable for the physical interaction [PMID:12203113], and the integrity of the SSD is critical, since a single missense substitution within it acts dominant-negatively to cause ectopic Hh target-gene activation and SMO stabilization [PMID:15042702]. PTCH1 is itself a Gli transcriptional target acting through a single functional Gli-binding site engaged by GLI1/2/3, establishing a negative-feedback loop in which Shh- and SMO-driven activity converges on this site to upregulate Ptch1 and adapt pathway output over time [PMID:15087129, PMID:25833741]; in the absence of Ptch1, the paralog Ptch2 mediates the ligand-dependent Shh response [PMID:25085974]. Loss of PTCH1 function is achieved through mutational inactivation combined with epigenetic silencing of the intact allele via DNA methylation, with MeCP2 reading promoter methylation to repress PTCH1, and reactivation by methyltransferase/HDAC inhibition restores expression and prevents tumor formation [PMID:16273213, PMID:19155313, PMID:23333245]. Beyond canonical signaling, PTCH1 functions as a proton-motive-force-driven multidrug efflux transporter that exports chemotherapeutics from cancer cells [PMID:30110910], and its internalization and trafficking are regulated by the co-receptor Gpr37l1 at peri-ciliary membranes [PMID:33350496].","teleology":[{"year":2002,"claim":"Establishing how PTCH1 acts on SMO required determining whether physical interaction and functional inhibition are separable; multiple isoforms were shown to bind SMO yet differ in inhibitory capacity.","evidence":"Co-immunoprecipitation and luciferase reporter assays of PTCH1 isoforms in co-transfected cells","pmids":["12203113"],"confidence":"Medium","gaps":["Structural basis of isoform-specific inhibition not defined","Did not establish the sterol-transport mechanism of inhibition"]},{"year":2004,"claim":"Defining the transcriptional logic of the Hh feedback loop, PTCH1 was shown to be induced through a single functional Gli-binding site shared by GLI1/2/3 and required for SHH/SMO-driven induction.","evidence":"Promoter-reporter assays, EMSA, and site-directed mutagenesis of Gli-binding sites","pmids":["15087129"],"confidence":"High","gaps":["Did not address the role of the non-functional second putative Gli site","Tissue-specific use of the alternative promoters not resolved"]},{"year":2004,"claim":"Testing whether the sterol-sensing domain is functionally required, an SSD missense mutation was shown to act dominant-negatively in vivo without altering subcellular localization, distinguishing SSD-dependent function from trafficking.","evidence":"In vivo Drosophila transgenic expression with immunofluorescence and Hh target-gene analysis","pmids":["15042702"],"confidence":"Medium","gaps":["Mechanism by which the SSD mutation disrupts SMO inhibition not defined","Relevance to vertebrate PTCH1 inferred from ortholog"]},{"year":2005,"claim":"Resolving how PTCH1 is inactivated in tumors retaining one allele, transcriptional silencing of the wild-type allele by promoter methylation was shown to combine with mutation of the other allele.","evidence":"Allele-specific RT-PCR and promoter methylation-reporter assays in Ptch1+/- mouse tumors","pmids":["16273213"],"confidence":"Medium","gaps":["Factors directing allele-specific methylation not identified","Single tumor model context"]},{"year":2009,"claim":"Testing whether epigenetic silencing is causal and reversible in tumorigenesis, reducing Dnmt1 or treating with demethylating/HDAC inhibitors reactivated wild-type Ptch1 and prevented tumor formation.","evidence":"Genetic Dnmt1 reduction and pharmacological 5-aza-dC/VPA treatment in Ptch1+/- mice with methylation and ChIP readouts","pmids":["19155313"],"confidence":"Medium","gaps":["Direct methylation reader not identified in this study","Specificity of pharmacological reactivation for Ptch1 not isolated"]},{"year":2011,"claim":"Probing SMO-independent signaling, PTCH1 was shown to transduce a non-canonical DHH-driven ERK phosphorylation signal conferring SMO-inhibitor resistance in CLL cells.","evidence":"SMO inhibitor and 5E1 antibody treatment, stromal co-culture, and phospho-ERK analysis in CLL cells","pmids":["22130798"],"confidence":"Medium","gaps":["Molecular link between PTCH1 and ERK not defined","Generality beyond trisomy-12 CLL unknown"]},{"year":2013,"claim":"Identifying the methylation reader that silences PTCH1, MeCP2 was shown to mediate promoter hypermethylation-associated repression during hepatic stellate cell activation.","evidence":"siRNA knockdown of MeCP2 with bisulfite/MSP, 5-aza-dC treatment, and expression analysis","pmids":["23333245"],"confidence":"Medium","gaps":["Whether MeCP2 acts directly or recruits other repressors not resolved","Single cell-type context"]},{"year":2014,"claim":"Determining the redundancy structure of the receptor system, Ptch2 was shown to sustain the ligand-dependent Shh response in the absence of Ptch1.","evidence":"Ptch1-/- and Ptch1-/-;Ptch2-/- knockout cells, 5E1 blocking antibody, and dominant-negative constructs in chick neural tube","pmids":["25085974"],"confidence":"High","gaps":["Stage-dependent division of labor between Ptch1 and Ptch2 not fully mapped","Molecular distinction between the two receptors not defined"]},{"year":2014,"claim":"miR-155 was shown to directly target the PTCH1 3'UTR, defining a post-transcriptional route to PTCH1 downregulation with functional consequences in endothelial progenitor cells.","evidence":"Dual-luciferase 3'UTR reporter, miR-155 perturbation, and siRNA rescue with functional cell assays","pmids":["29545091"],"confidence":"Medium","gaps":["In vivo relevance of the miR-155–PTCH1 axis not established","Hh-pathway dependence of the phenotype not isolated"]},{"year":2015,"claim":"Clarifying the dynamic role of PTCH1 induction, its Gli-driven upregulation was shown to contribute to temporal adaptation of Shh output alongside Gli2 downregulation.","evidence":"Quantitative immunofluorescence of the neural tube Shh gradient with computational modeling and downstream pathway stimulation in NIH3T3 cells","pmids":["25833741"],"confidence":"Medium","gaps":["Quantitative contribution of Ptch1 versus other adaptation mechanisms not separated","Molecular trigger linking Ptch1 levels to attenuation unspecified"]},{"year":2018,"claim":"Defining a signaling-independent activity, PTCH1 was shown to act as a proton-motive-force-driven multidrug efflux transporter whose inhibition sensitizes cancer cells to chemotherapy.","evidence":"Drug efflux assays, inhibitor screening, and a doxorubicin-combination xenograft model","pmids":["30110910"],"confidence":"Medium","gaps":["Structural basis distinguishing efflux from sterol-transport function not defined","Spectrum of physiological substrates unknown"]},{"year":2019,"claim":"Providing the structural mechanism for SMO inhibition, cryo-EM of human PTCH1 bound to palmitoylated Shh revealed annular sterols engaging the SSD and SSD-like domains, defining a sterol translocation route.","evidence":"3.4 Å cryo-EM structure with analysis of sterol interaction sites","pmids":["31555730"],"confidence":"High","gaps":["Direction and kinetics of sterol transport not measured","Conformational change upon Shh binding that relieves SMO not captured"]},{"year":2020,"claim":"Identifying a trafficking regulator, Gpr37l1 was shown to interact with Ptch1 at peri-ciliary membranes and control its internalization, with loss elevating Ptch1, cholesterol, ciliary Smo, and Shh production.","evidence":"Gpr37l1-null astrocyte cultures with localization, cholesterol, Shh, and proliferation readouts","pmids":["33350496"],"confidence":"Medium","gaps":["Molecular mechanism of Gpr37l1-driven internalization not defined","Generality beyond cerebellar astrocytes unknown"]},{"year":null,"claim":"How the sterol-transport activity captured structurally is mechanistically coupled to SMO inhibition, ciliary trafficking, and the multidrug efflux function within a single protein remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No dynamic measurement linking sterol transport to SMO repression","Relationship between efflux transport and sterol-sensing functions undefined","Mechanism of non-canonical PTCH1→ERK signaling unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[6]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,12]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[12]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,5]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,5]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[6,7,8]}],"complexes":[],"partners":["SMO","SHH","GPR37L1","GLI1","GLI2","GLI3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q13635","full_name":"Protein patched homolog 1","aliases":[],"length_aa":1447,"mass_kda":160.5,"function":"Acts as a receptor for sonic hedgehog (SHH), indian hedgehog (IHH) and desert hedgehog (DHH). Associates with the smoothened protein (SMO) to transduce the hedgehog's proteins signal. 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stomatologica","url":"https://pubmed.ncbi.nlm.nih.gov/19234436","citation_count":17,"is_preprint":false},{"pmid":"20561220","id":"PMC_20561220","title":"MMP-13 expression in keratocyst odontogenic tumour associated with NBCCS and sporadic keratocysts.","date":"2010","source":"Oral diseases","url":"https://pubmed.ncbi.nlm.nih.gov/20561220","citation_count":17,"is_preprint":false},{"pmid":"18674957","id":"PMC_18674957","title":"PTCH1 isoforms in odontogenic keratocysts.","date":"2008","source":"Oral oncology","url":"https://pubmed.ncbi.nlm.nih.gov/18674957","citation_count":17,"is_preprint":false},{"pmid":"27561271","id":"PMC_27561271","title":"Nevoid basal cell carcinoma syndrome caused by splicing mutations in the PTCH1 gene.","date":"2017","source":"Familial cancer","url":"https://pubmed.ncbi.nlm.nih.gov/27561271","citation_count":17,"is_preprint":false},{"pmid":"15459969","id":"PMC_15459969","title":"Spectrum of PTCH mutations in Italian nevoid basal cell-carcinoma syndrome patients: identification of thirteen novel alleles.","date":"2004","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/15459969","citation_count":17,"is_preprint":false},{"pmid":"16596257","id":"PMC_16596257","title":"Mutation in exon 7 of PTCH deregulates SHH/PTCH/SMO signaling: possible linkage to WNT.","date":"2006","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/16596257","citation_count":16,"is_preprint":false},{"pmid":"29499648","id":"PMC_29499648","title":"Genome-wide identification, phylogeny, evolution, and expression patterns of MtN3/saliva/SWEET genes and functional analysis of BcNS in Brassica rapa.","date":"2018","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/29499648","citation_count":16,"is_preprint":false},{"pmid":"22221699","id":"PMC_22221699","title":"Loss of heterozygosity of the PTCH gene in ameloblastoma.","date":"2012","source":"Human pathology","url":"https://pubmed.ncbi.nlm.nih.gov/22221699","citation_count":16,"is_preprint":false},{"pmid":"16804411","id":"PMC_16804411","title":"Aberrant expression of PTCH (patched gene) and Smo (smoothened gene) in human pancreatic cancerous tissues and its association with hyperglycemia.","date":"2006","source":"Pancreas","url":"https://pubmed.ncbi.nlm.nih.gov/16804411","citation_count":16,"is_preprint":false},{"pmid":"23440386","id":"PMC_23440386","title":"Altered expression of PTCH and HHIP in gastric cancer through their gene promoter methylation: novel targets for gastric cancer.","date":"2013","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/23440386","citation_count":16,"is_preprint":false},{"pmid":"28329421","id":"PMC_28329421","title":"Naproxen Inhibits UVB-induced Basal Cell and Squamous Cell Carcinoma Development in Ptch1+/- /SKH-1 Hairless Mice.","date":"2017","source":"Photochemistry and photobiology","url":"https://pubmed.ncbi.nlm.nih.gov/28329421","citation_count":15,"is_preprint":false},{"pmid":"30754660","id":"PMC_30754660","title":"Nevoid Basal Cell Carcinoma Syndrome: PTCH1 Mutation Profile and Expression of Genes Involved in the Hedgehog Pathway in Argentinian Patients.","date":"2019","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/30754660","citation_count":15,"is_preprint":false},{"pmid":"29277811","id":"PMC_29277811","title":"PTCH1 Germline Mutations and the Basaloid Follicular Hamartoma Values in the Tumor Spectrum of Basal Cell Carcinoma Syndrome (NBCCS).","date":"2018","source":"Anticancer research","url":"https://pubmed.ncbi.nlm.nih.gov/29277811","citation_count":14,"is_preprint":false},{"pmid":"33350496","id":"PMC_33350496","title":"Gpr37l1/prosaposin receptor regulates Ptch1 trafficking, Shh production, and cell proliferation in cerebellar primary astrocytes.","date":"2020","source":"Journal of neuroscience research","url":"https://pubmed.ncbi.nlm.nih.gov/33350496","citation_count":14,"is_preprint":false},{"pmid":"16777989","id":"PMC_16777989","title":"Molecular basis of basal cell carcinogenesis in the atomic-bomb survivor population: p53 and PTCH gene alterations.","date":"2006","source":"Carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/16777989","citation_count":14,"is_preprint":false},{"pmid":"33359005","id":"PMC_33359005","title":"PTCH1 regulates anchorage-independent growth and bone invasion of non-small cell lung cancer cells.","date":"2020","source":"Bone","url":"https://pubmed.ncbi.nlm.nih.gov/33359005","citation_count":13,"is_preprint":false},{"pmid":"35579168","id":"PMC_35579168","title":"Long Non-coding RNA SNHG16 Facilitates Esophageal Cancer Cell Proliferation and Self-renewal through the microRNA-802/PTCH1 Axis.","date":"2022","source":"Current medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35579168","citation_count":13,"is_preprint":false},{"pmid":"7627481","id":"PMC_7627481","title":"The prevalence of cervical and thoracic congenital skeletal abnormalities in basal cell naevus syndrome; a review of cervical and chest radiographs in 80 patients with BCNS.","date":"1995","source":"The British journal of radiology","url":"https://pubmed.ncbi.nlm.nih.gov/7627481","citation_count":13,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":50662,"output_tokens":4738,"usd":0.111528,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12931,"output_tokens":4291,"usd":0.085965,"stage2_stop_reason":"end_turn"},"total_usd":0.197493,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"Cryo-EM structure of human PTCH1 bound to a palmitoylated Sonic hedgehog ligand (ShhNC24II) at 3.4 Å resolution reveals that the membrane-embedded region of PTCH1 is surrounded by 10 sterol molecules at the inner and outer lipid bilayer; these annular sterols interact with both the sterol-sensing domain (SSD) and the SSD-like domain (SSDL) on opposite sides of PTCH1, suggesting a route for sterol translocation across the lipid bilayer.\",\n      \"method\": \"Cryo-EM structure determination (3.4 Å resolution) with structural analysis of sterol binding sites\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — near-atomic resolution cryo-EM structure with direct identification of sterol interaction sites; rigorous structural data from a single focused study\",\n      \"pmids\": [\"31555730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PTCH1 is transcriptionally regulated by three independent promoters generating transcripts with alternative first exons. Only one of two putative Gli-binding sites in the promoter region is functional; GLI1, GLI2, and GLI3 bind and activate transcription through this single site. Upstream pathway components SHH and SMO operate exclusively through this functional Gli-binding site, as mutation of it abolishes enhanced transcription induced by Gli proteins, SHH, or SMO.\",\n      \"method\": \"Promoter-reporter assays, electrophoretic mobility shift assay (EMSA), site-directed mutagenesis of Gli-binding sites, transfection with truncated GLI3\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — functional mutagenesis of binding site combined with reporter assays and multiple pathway components tested; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"15087129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PTCH1 encodes multiple isoforms arising from alternative first exons (exon 1, 1A, 1B). All PTCH1 isoforms interact with SMOH in co-transfected cells and can inhibit SHH activity. However, only the PTCH1B isoform fully inhibits SMOH signaling, while other isoforms cannot; the N-terminal region encoded by exon 1B is required for complete SMOH inhibition but not for physical interaction with SMOH.\",\n      \"method\": \"Co-immunoprecipitation (doubly transfected cells), functional luciferase reporter assays (SHH and SMO inhibition), RT-PCR of tissue expression\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction and functional assays in same study; single lab with two orthogonal methods\",\n      \"pmids\": [\"12203113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"A missense mutation in the sterol-sensing domain of patched (G509V, equivalent in Drosophila ptc) acts as a dominant negative in vivo in Drosophila: ectopic expression causes ectopic activation of Hedgehog target genes and ectopic membrane stabilization of Smoothened. Unlike a C-terminal truncation dominant-negative (which localizes to plasma membrane), G509V shows vesicular localization identical to wild-type, indicating that dominant-negative function can result from disruption of different aspects of Patched protein behavior. A different mutation at the same residue (G509R) did not show dominant-negative activity.\",\n      \"method\": \"In vivo Drosophila transgenic expression, immunofluorescence localization, genetic analysis of Hh target gene activation\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo functional assay with mutagenesis comparisons in Drosophila ortholog; single lab, multiple mutations tested\",\n      \"pmids\": [\"15042702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In the vertebrate neural tube, Ptch1 transcriptional upregulation (via Shh-induced Gli activity) contributes to adaptation/attenuation of Shh pathway output over time, alongside Gli2 protein downregulation and differential stability of Gli isoforms. Adaptation continues when the pathway is stimulated downstream of Ptch1, indicating that Ptch1 upregulation is one of multiple mechanisms controlling intracellular Shh signaling dynamics.\",\n      \"method\": \"Quantitative immunofluorescence of Shh gradient in mouse neural tube, computational modeling, Gli2 protein expression analysis, pathway stimulation downstream of Ptch1 in NIH3T3 cells\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo quantitative measurements combined with computational modeling and cell-based pathway perturbation; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"25833741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In Ptch1-/- cells, Shh signaling remains ligand-dependent: the Shh-blocking antibody 5E1 inhibits the response in Ptch1-/- cells, and Ptch1-/-;Ptch2-/- double knockout cells cannot further activate the Shh response beyond Ptch1-/- alone. Expression of a dominant-negative Ptch2 (but not dominant-negative Ptch1) in the developing chick neural tube activates the Shh response, demonstrating that Ptch2 mediates the Shh response in the absence of Ptch1 at early developmental stages.\",\n      \"method\": \"Genetic knockout cells (Ptch1-/-, Ptch1-/-;Ptch2-/-), Shh-blocking antibody (5E1), dominant-negative constructs in chick neural tube in ovo electroporation, migration assays\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genetic approaches (double KO, dominant-negative, antibody blocking) in two model systems; rigorous epistasis analysis\",\n      \"pmids\": [\"25085974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PTCH1 functions as a multidrug efflux transporter that pumps chemotherapeutic agents such as doxorubicin out of cancer cells using the proton motive force (reversed pH gradient in cancer cells), unlike ABC transporters which use ATP hydrolysis. Inhibition of Ptch1 drug efflux activity enhances cytotoxicity of chemotherapeutics in cancer cell lines overexpressing Ptch1, and in vivo combination with doxorubicin prevented xenografted adrenocortical carcinoma tumor development.\",\n      \"method\": \"Drug efflux assays in cancer cell lines, chemical library screening for Ptch1 inhibitors, in vivo xenograft mouse model with doxorubicin combination treatment\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based efflux assays and in vivo proof-of-concept; single lab, multiple methods including in vitro and in vivo\",\n      \"pmids\": [\"30110910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In heterozygous Ptch1 knockout mouse tumors, the wild-type Ptch1 allele is transcriptionally silenced (via promoter methylation sensitivity), while the mutant allele is predominantly expressed. This mutant Ptch1-derived protein is incapable of pathway inhibition. Transcriptional silencing of one Ptch1 allele followed by mutation of the other (or vice versa) constitutes a mechanism of PTCH1/Ptch1 tumor suppressor inactivation that explains retention of one allele in many tumors.\",\n      \"method\": \"Allele-specific RT-PCR in Ptch1+/- mouse tumors, promoter methylation-reporter assays, functional pathway inhibition assays\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — allele-specific expression analysis in mouse tumors combined with promoter methylation functional assay; single lab, two orthogonal methods\",\n      \"pmids\": [\"16273213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In heterozygous Ptch1 knockout mice, epigenetic silencing of the intact (wild-type) Ptch1 allele via DNA methylation contributes to tumor formation. Reducing Dnmt1 activity significantly reduced tumor incidence. Combined treatment with the DNA methyltransferase inhibitor 5-aza-dC and the HDAC inhibitor valproic acid reactivated wild-type Ptch1 expression (associated with reduced Ptch1 promoter methylation and histone hyperacetylation) and efficiently prevented medulloblastoma and rhabdomyosarcoma formation.\",\n      \"method\": \"Genetic reduction of Dnmt1 in Ptch1+/- mice, pharmacological treatment (5-aza-dC + VPA) in vivo, promoter methylation analysis, chromatin immunoprecipitation (histone acetylation)\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic and pharmacological evidence with molecular mechanistic readouts; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"19155313\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MeCP2 (methyl-CpG-binding protein 2) mediates silencing of PTCH1 via DNA methylation in hepatic stellate cells. Hypermethylation of the PTCH1 promoter is associated with HSC activation and liver fibrogenesis. siRNA knockdown of MeCP2 increased PTCH1 mRNA and protein expression in hepatic myofibroblasts, and 5-aza-dC treatment prevented loss of PTCH1 expression during HSC activation.\",\n      \"method\": \"siRNA knockdown of MeCP2, bisulfite sequencing/MSP of PTCH1 promoter, 5-aza-dC treatment, RT-PCR and Western blot\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown with multiple molecular readouts (methylation, mRNA, protein); single lab\",\n      \"pmids\": [\"23333245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MeCP2 reduces PTCH1 expression in fibroblast-like synoviocytes of adjuvant arthritis rats through promoter hypermethylation. Knockdown of MeCP2 by siRNA increased PTCH1 expression, which in turn inhibited Hedgehog signaling (decreased Gli1 and Shh) and reduced secretion of inflammatory cytokines IL-6 and TNF-α.\",\n      \"method\": \"siRNA knockdown of MeCP2, methylation-specific PCR, RT-PCR, Western blot, cytokine measurement (ELISA)\",\n      \"journal\": \"Inflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA knockdown with methylation and functional downstream pathway readouts; single lab, replicated MeCP2-PTCH1 axis from independent group\",\n      \"pmids\": [\"28573530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PTCH53 (PTCHD4), a p53 target gene homologous to PTCH1, is transcriptionally activated by p53 in response to DNA damage and can repress Hedgehog pathway activation by inhibiting canonical signaling by the GPCR SMO, delineating a novel inducible pathway by which p53 represses Hh signals. (Note: this is about PTCH53/PTCHD4, not PTCH1 itself, but the paper defines functional relationship of PTCH1 homology.)\",\n      \"method\": \"Luciferase reporter assays, quantitative RT-PCR in TP53-mutant cell lines and human tumors, SMO inhibition assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pertains primarily to PTCH53/PTCHD4 (a homolog), not PTCH1 itself; indirect relevance to PTCH1 mechanism\",\n      \"pmids\": [\"25296753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The G protein-coupled receptor Gpr37l1 interacts with Ptch1 at peri-ciliary membranes in cerebellar astrocytes. In Gpr37l1-/- astrocytes, Ptch1 protein expression and internalization are markedly increased, intracellular cholesterol content rises, ciliary localization of Smo increases, and Shh production is markedly elevated, along with increased astrocyte proliferation. These findings indicate that Gpr37l1 specifically regulates Ptch1 internalization/trafficking, with consequent effects on Shh production and downstream proliferative signaling.\",\n      \"method\": \"Gpr37l1 null mutant mouse cerebellar primary astrocyte cultures, immunofluorescence of Ptch1 and Smo localization, cholesterol measurement, Shh production quantification, proliferation assays\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO model with multiple cellular and molecular readouts; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"33350496\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In CLL cells with trisomy 12, constitutive Hedgehog pathway activation is driven by autocrine Desert Hedgehog (DHH) ligand secretion, which activates pathway signaling through PTCH1. BM stromal cell-derived DHH activates a non-canonical ERK phosphorylation pathway directly downstream of the PTCH1 receptor without involvement of SMO, conferring resistance to SMO inhibitors; this could be overcome by the HH-blocking antibody 5E1 or combination of SMO and ERK inhibitors.\",\n      \"method\": \"SMO inhibitor treatment of CLL cells, HH-blocking antibody (5E1), co-culture experiments with DHH-expressing BM stromal cells, phospho-ERK Western blot, GLI1/PTCH1 transcript quantification\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional antibody blocking and pharmacological epistasis establishing non-canonical PTCH1→ERK signaling; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"22130798\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PTCH1 promotes anchorage-independent (spheroid) growth, migration, and invasion of non-small cell lung cancer cells, associated with expression of MMP7 and SOX2. shRNA-mediated PTCH1 knockdown reduced spherical colony formation, migration, and invasion in vitro, and decreased bone destruction and osteoclastogenesis in a mouse bone metastasis model in vivo.\",\n      \"method\": \"Lentiviral shRNA knockdown of PTCH1, spheroid colony formation assay, migration/invasion assays, mouse bone metastasis model, Western blot (MMP7, SOX2)\",\n      \"journal\": \"Bone\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined cellular phenotype in vitro and in vivo; single lab, multiple readouts\",\n      \"pmids\": [\"33359005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-155 directly targets the 3'UTR of PTCH1 mRNA (validated by dual-luciferase reporter assay) and downregulates PTCH1 mRNA and protein expression. miR-155-mediated PTCH1 downregulation worsens high glucose-induced endothelial progenitor cell dysfunction (reduced viability, migration, tube formation, NO production; increased apoptosis and ROS); silencing PTCH1 by siRNA abrogated the protective effect of anti-miR-155.\",\n      \"method\": \"Dual-luciferase reporter assay, miR-155 overexpression/inhibition, PTCH1 siRNA knockdown, cell viability, migration, tube formation, NO, apoptosis, and ROS assays\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct 3'UTR targeting validated by luciferase assay with functional rescue experiment; single lab\",\n      \"pmids\": [\"29545091\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTCH1 is a twelve-transmembrane receptor for Sonic Hedgehog (SHH) ligands that normally inhibits Smoothened (SMO) through a sterol-transport mechanism (structurally defined by cryo-EM showing 10 annular sterols interacting with its sterol-sensing domain); SHH binding to PTCH1 relieves SMO inhibition to activate Gli transcription factors, while PTCH1 itself is a transcriptional target of Gli proteins acting through a single functional Gli-binding site, creating a negative feedback loop. PTCH1 additionally functions as a proton-motive-force-driven multidrug efflux transporter in cancer cells, and its internalization and trafficking are regulated by the co-receptor Gpr37l1, with loss of PTCH1 function achievable through mutational inactivation, promoter hypermethylation (mediated by MeCP2), or epigenetic silencing, all of which constitutively activate downstream Hh signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PTCH1 is the receptor that sets the threshold of Hedgehog (Hh) pathway activity, controlling developmental patterning and acting as a tumor suppressor by restraining downstream signaling [#5, #7]. Its membrane-embedded core is encircled by annular sterols that engage both a sterol-sensing domain (SSD) and an SSD-like domain on opposite faces of the protein, defining a route for sterol translocation across the bilayer that underlies its capacity to inhibit Smoothened (SMO) [#0]. PTCH1 physically associates with SMO and inhibits its signaling; an isoform-specific N-terminal region (exon 1B) is required for full SMO inhibition but is dispensable for the physical interaction [#2], and the integrity of the SSD is critical, since a single missense substitution within it acts dominant-negatively to cause ectopic Hh target-gene activation and SMO stabilization [#3]. PTCH1 is itself a Gli transcriptional target acting through a single functional Gli-binding site engaged by GLI1/2/3, establishing a negative-feedback loop in which Shh- and SMO-driven activity converges on this site to upregulate Ptch1 and adapt pathway output over time [#1, #4]; in the absence of Ptch1, the paralog Ptch2 mediates the ligand-dependent Shh response [#5]. Loss of PTCH1 function is achieved through mutational inactivation combined with epigenetic silencing of the intact allele via DNA methylation, with MeCP2 reading promoter methylation to repress PTCH1, and reactivation by methyltransferase/HDAC inhibition restores expression and prevents tumor formation [#7, #8, #9]. Beyond canonical signaling, PTCH1 functions as a proton-motive-force-driven multidrug efflux transporter that exports chemotherapeutics from cancer cells [#6], and its internalization and trafficking are regulated by the co-receptor Gpr37l1 at peri-ciliary membranes [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing how PTCH1 acts on SMO required determining whether physical interaction and functional inhibition are separable; multiple isoforms were shown to bind SMO yet differ in inhibitory capacity.\",\n      \"evidence\": \"Co-immunoprecipitation and luciferase reporter assays of PTCH1 isoforms in co-transfected cells\",\n      \"pmids\": [\"12203113\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of isoform-specific inhibition not defined\", \"Did not establish the sterol-transport mechanism of inhibition\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defining the transcriptional logic of the Hh feedback loop, PTCH1 was shown to be induced through a single functional Gli-binding site shared by GLI1/2/3 and required for SHH/SMO-driven induction.\",\n      \"evidence\": \"Promoter-reporter assays, EMSA, and site-directed mutagenesis of Gli-binding sites\",\n      \"pmids\": [\"15087129\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address the role of the non-functional second putative Gli site\", \"Tissue-specific use of the alternative promoters not resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Testing whether the sterol-sensing domain is functionally required, an SSD missense mutation was shown to act dominant-negatively in vivo without altering subcellular localization, distinguishing SSD-dependent function from trafficking.\",\n      \"evidence\": \"In vivo Drosophila transgenic expression with immunofluorescence and Hh target-gene analysis\",\n      \"pmids\": [\"15042702\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which the SSD mutation disrupts SMO inhibition not defined\", \"Relevance to vertebrate PTCH1 inferred from ortholog\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Resolving how PTCH1 is inactivated in tumors retaining one allele, transcriptional silencing of the wild-type allele by promoter methylation was shown to combine with mutation of the other allele.\",\n      \"evidence\": \"Allele-specific RT-PCR and promoter methylation-reporter assays in Ptch1+/- mouse tumors\",\n      \"pmids\": [\"16273213\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Factors directing allele-specific methylation not identified\", \"Single tumor model context\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Testing whether epigenetic silencing is causal and reversible in tumorigenesis, reducing Dnmt1 or treating with demethylating/HDAC inhibitors reactivated wild-type Ptch1 and prevented tumor formation.\",\n      \"evidence\": \"Genetic Dnmt1 reduction and pharmacological 5-aza-dC/VPA treatment in Ptch1+/- mice with methylation and ChIP readouts\",\n      \"pmids\": [\"19155313\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct methylation reader not identified in this study\", \"Specificity of pharmacological reactivation for Ptch1 not isolated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Probing SMO-independent signaling, PTCH1 was shown to transduce a non-canonical DHH-driven ERK phosphorylation signal conferring SMO-inhibitor resistance in CLL cells.\",\n      \"evidence\": \"SMO inhibitor and 5E1 antibody treatment, stromal co-culture, and phospho-ERK analysis in CLL cells\",\n      \"pmids\": [\"22130798\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between PTCH1 and ERK not defined\", \"Generality beyond trisomy-12 CLL unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identifying the methylation reader that silences PTCH1, MeCP2 was shown to mediate promoter hypermethylation-associated repression during hepatic stellate cell activation.\",\n      \"evidence\": \"siRNA knockdown of MeCP2 with bisulfite/MSP, 5-aza-dC treatment, and expression analysis\",\n      \"pmids\": [\"23333245\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether MeCP2 acts directly or recruits other repressors not resolved\", \"Single cell-type context\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Determining the redundancy structure of the receptor system, Ptch2 was shown to sustain the ligand-dependent Shh response in the absence of Ptch1.\",\n      \"evidence\": \"Ptch1-/- and Ptch1-/-;Ptch2-/- knockout cells, 5E1 blocking antibody, and dominant-negative constructs in chick neural tube\",\n      \"pmids\": [\"25085974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stage-dependent division of labor between Ptch1 and Ptch2 not fully mapped\", \"Molecular distinction between the two receptors not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"miR-155 was shown to directly target the PTCH1 3'UTR, defining a post-transcriptional route to PTCH1 downregulation with functional consequences in endothelial progenitor cells.\",\n      \"evidence\": \"Dual-luciferase 3'UTR reporter, miR-155 perturbation, and siRNA rescue with functional cell assays\",\n      \"pmids\": [\"29545091\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of the miR-155–PTCH1 axis not established\", \"Hh-pathway dependence of the phenotype not isolated\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Clarifying the dynamic role of PTCH1 induction, its Gli-driven upregulation was shown to contribute to temporal adaptation of Shh output alongside Gli2 downregulation.\",\n      \"evidence\": \"Quantitative immunofluorescence of the neural tube Shh gradient with computational modeling and downstream pathway stimulation in NIH3T3 cells\",\n      \"pmids\": [\"25833741\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative contribution of Ptch1 versus other adaptation mechanisms not separated\", \"Molecular trigger linking Ptch1 levels to attenuation unspecified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defining a signaling-independent activity, PTCH1 was shown to act as a proton-motive-force-driven multidrug efflux transporter whose inhibition sensitizes cancer cells to chemotherapy.\",\n      \"evidence\": \"Drug efflux assays, inhibitor screening, and a doxorubicin-combination xenograft model\",\n      \"pmids\": [\"30110910\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis distinguishing efflux from sterol-transport function not defined\", \"Spectrum of physiological substrates unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Providing the structural mechanism for SMO inhibition, cryo-EM of human PTCH1 bound to palmitoylated Shh revealed annular sterols engaging the SSD and SSD-like domains, defining a sterol translocation route.\",\n      \"evidence\": \"3.4 Å cryo-EM structure with analysis of sterol interaction sites\",\n      \"pmids\": [\"31555730\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direction and kinetics of sterol transport not measured\", \"Conformational change upon Shh binding that relieves SMO not captured\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying a trafficking regulator, Gpr37l1 was shown to interact with Ptch1 at peri-ciliary membranes and control its internalization, with loss elevating Ptch1, cholesterol, ciliary Smo, and Shh production.\",\n      \"evidence\": \"Gpr37l1-null astrocyte cultures with localization, cholesterol, Shh, and proliferation readouts\",\n      \"pmids\": [\"33350496\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism of Gpr37l1-driven internalization not defined\", \"Generality beyond cerebellar astrocytes unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the sterol-transport activity captured structurally is mechanistically coupled to SMO inhibition, ciliary trafficking, and the multidrug efflux function within a single protein remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No dynamic measurement linking sterol transport to SMO repression\", \"Relationship between efflux transport and sterol-sensing functions undefined\", \"Mechanism of non-canonical PTCH1→ERK signaling unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 12]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [6, 7, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SMO\", \"SHH\", \"GPR37L1\", \"GLI1\", \"GLI2\", \"GLI3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}