{"gene":"MC5R","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2016,"finding":"MC5R and MC1R from barfin flounder form heterodimers at the plasma membrane. Co-immunoprecipitation showed bfMC1R and bfMC5R physically interact, and heterodimerization produces ligand-dependent inhibition of cAMP accumulation: α-MSH-induced cAMP was suppressed by coexpression of both receptors, whereas desacetyl-α-MSH was not inhibitory. This provides a mechanism for selective pigment dispersion in different chromatophore types.","method":"Co-immunoprecipitation, immunofluorescence co-localization, cAMP accumulation assay in CHO cells","journal":"General and comparative endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus functional cAMP assay in a single study; single lab, two orthogonal methods","pmids":["27080548"],"is_preprint":false},{"year":2017,"finding":"Cell surface targeting of MC5R requires two serine-rich motifs in the N-terminal domain (residues Ser4/Ser5 and Ser17/Glu18). Site-directed mutagenesis of these residues caused retention of MC5R at the ER/Golgi complex rather than delivery to the plasma membrane. The first 21 amino acids contain the information required for correct trafficking, and homodimerization was unaffected by these mutations, indicating that surface targeting and dimerization are independent processes.","method":"N-terminal deletion analysis, site-directed mutagenesis, fluorescence microscopy of ER/Golgi vs. plasma membrane localization","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis plus subcellular localization imaging with functional trafficking readout; single lab, two orthogonal methods","pmids":["28396017"],"is_preprint":false},{"year":2011,"finding":"MC5R expression is required on APCs (not T cells) to promote regulatory immunity in the spleen of EAU-recovering mice. APCs from wild-type EAU-recovering mice induced TGF-β expression and FoxP3+CD25+CD4+ Treg cell activation in IRBP-specific effector T cells from MC5r-/- mice, whereas APCs from MC5r-/- mice failed to do so. Adoptive transfer confirmed the APC-intrinsic dependence on MC5r.","method":"MC5r-/- mouse model, APC isolation, co-culture cytokine assays (ELISA, flow cytometry), adoptive transfer","journal":"Investigative ophthalmology & visual science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout epistasis plus adoptive transfer with functional readout; single lab, multiple orthogonal methods","pmids":["21989727"],"is_preprint":false},{"year":2013,"finding":"MC5r-dependent regulatory immunity in post-EAU spleen requires adenosine 2A receptor (A2Ar) expression on T cells. MC5r-dependent APCs were identified as CD11b+F4/80+Ly-6C(low)Ly-6G+CD39+CD73+ cells, and these APCs use the adenosinergic pathway to activate autoantigen-specific FoxP3+CD25+CD4+ regulatory T cells. Both MC5r and A2Ar are required for EAU-suppressing regulatory immunity.","method":"MC5r-/- and A2Ar-/- mouse models, flow cytometry, functional assays of Treg induction","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — dual genetic knockout epistasis with defined cellular phenotype; single lab, multiple orthogonal methods","pmids":["24043903"],"is_preprint":false},{"year":2023,"finding":"The melanocortin/MC5R axis regulates proliferation of hematopoietic stem cells (HSCs) after irradiation via activation of the PI3K/AKT and MAPK signaling pathways. MC5R knockout aggravated irradiation-induced myelosuppression due to impaired HSC proliferation and reconstitution, and α-MSH treatment accelerated hematopoietic recovery in irradiated mice.","method":"MC5R knockout mouse model, irradiation injury model, pathway inhibitor assays (PI3K/AKT, MAPK), α-MSH treatment, colony/reconstitution assays","journal":"Blood advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout plus pharmacological rescue with pathway-level readout; single lab, multiple methods","pmids":["36920787"],"is_preprint":false},{"year":2025,"finding":"Peripheral α-MSH promotes glucose uptake in skeletal muscle via an MC5R-dependent mechanism. A selective MC5R agonist (PG-901) reduced blood glucose during a glucose tolerance test in wild-type mice but had no effect in MC5R-deficient mice. Both α-MSH and PG-901 directly induced glucose uptake in primary human and non-human primate myotubes in vitro, and the pathway was functional in healthy human volunteers.","method":"MC5R knockout mouse model, glucose tolerance test, in vitro glucose uptake assay in primary human myotubes, human oral glucose tolerance test with α-MSH administration","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout abolishes effect, selective agonist in multiple species including human; single study, multiple orthogonal methods; preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.03.26.645414"],"is_preprint":true},{"year":2025,"finding":"Podocyte MC5R intercepts the complement amplification loop in membranous nephropathy by inhibiting podocyte expression of complement factors B and D via a PPARγ-dependent mechanism. MC5R knockout exacerbated glomerular C5b-9 and C3 fixation, whereas MC5R agonism diminished it. Podocyte-specific reconstitution of MC5R in MC5R knockout mice restored melanocortin therapeutic efficacy, establishing podocyte MC5R as the critical cell-autonomous effector.","method":"MC5R knockout mouse model, podocyte-specific MC5R reconstitution, selective MC5R agonist (PG-901), complement cascade analysis, PPARγ pathway analysis, cultured podocyte assays","journal":"Molecular therapy","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific reconstitution plus pharmacological agonism/antagonism, multiple orthogonal mechanistic readouts (complement factors, PPARγ), single rigorous study","pmids":["40739753"],"is_preprint":false},{"year":2018,"finding":"MC5R stimulation in high-glucose-exposed cardiac H9c2 cells reduces hypertrophy by activating PI3K signaling and decreasing the GLUT1/GLUT4 ratio on the cell membrane, mediated by a reduction in miR-133a levels.","method":"MC5R agonist (α-MSH, PG-901) treatment of H9c2 cells, PI3K activity assay, GLUT1/GLUT4 quantification, miR-133a measurement, streptozotocin-diabetic rat echocardiography","journal":"Frontiers in physiology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pharmacological agonism with pathway readouts but no receptor-specific genetic ablation; single lab, mechanistic pathway partially characterized","pmids":["30416452"],"is_preprint":false},{"year":2000,"finding":"MC5-R in bovine adrenal glomerulosa cells is upregulated by ACTH, α-MSH, and angiotensin II (7-, 5-, and 4.5-fold respectively) at the mRNA level, and MC5-R is expressed exclusively in the glomerulosa zone (not fasciculata) of adult adrenal cortex, at levels at least 100-fold lower than MC2-R.","method":"Semi-quantitative RT-PCR, RNase protection assay, primary adrenocortical cell culture with hormone treatment","journal":"Molecular and cellular endocrinology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — expression/regulation in primary cells by semi-quantitative methods; single lab, no functional downstream mechanism defined","pmids":["10687856"],"is_preprint":false},{"year":2021,"finding":"MC5R deficiency in mice leads to impaired epidermal barrier function, characterized by increased transepidermal water loss, fewer lamellar granules, reduced lipid secretion, and expansion of the trans-Golgi network in epidermal cells. MC5R-deficient mice also showed increased UVB sensitivity with enhanced inflammatory cell infiltration and elevated IL-6 but reduced IL-10.","method":"MC5R knockout mouse model, transepidermal water loss measurement, dye exclusion assay, transmission electron microscopy, cytokine measurement","journal":"JID innovations","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with ultrastructural (TEM) and functional barrier readouts; single lab, multiple orthogonal methods","pmids":["34909724"],"is_preprint":false}],"current_model":"MC5R is a G protein-coupled receptor that signals through cAMP and PI3K/AKT/MAPK pathways; its cell surface trafficking requires N-terminal Ser4/Ser5 and Ser17/Glu18 motifs; it acts on APCs to promote adenosinergic Treg induction during ocular autoimmunity; it mediates α-MSH-driven glucose uptake in skeletal muscle; it protects podocytes in membranous nephropathy by suppressing complement factors B and D via a PPARγ-dependent mechanism; and it supports hematopoietic stem cell proliferation and epidermal barrier function under stress conditions."},"narrative":{"mechanistic_narrative":"MC5R is a melanocortin G protein-coupled receptor that couples α-MSH and related melanocortin ligands to cAMP and PI3K/AKT/MAPK signaling to control diverse peripheral cellular responses [PMID:36920787, PMID:10687856]. Its activity is set at the cell surface: delivery of MC5R to the plasma membrane requires two N-terminal serine-rich motifs (Ser4/Ser5 and Ser17/Glu18), and mutation of these residues traps the receptor at the ER/Golgi, a process independent of its capacity to dimerize [PMID:28396017]. MC5R can engage other melanocortin receptors physically, forming heterodimers with MC1R that confer ligand-dependent suppression of cAMP signaling [PMID:27080548]. Functionally, MC5R operates as a cell-autonomous effector across tissues: on antigen-presenting cells it drives adenosinergic induction of FoxP3+ regulatory T cells via A2A receptor signaling to enforce ocular regulatory immunity [PMID:21989727, PMID:24043903]; in skeletal muscle it mediates melanocortin-driven glucose uptake [PMID:bio_10.1101_2025.03.26.645414]; in podocytes it suppresses complement factors B and D through a PPARγ-dependent mechanism to intercept the complement amplification loop in membranous nephropathy [PMID:40739753]; and it supports hematopoietic stem cell proliferation after irradiation through PI3K/AKT and MAPK activation [PMID:36920787]. MC5R is also required for epidermal barrier integrity and lamellar granule-mediated lipid secretion [PMID:34909724]. No structural model of human MC5R or its signaling complex is characterized in the available corpus.","teleology":[{"year":2000,"claim":"Established that MC5R is expressed and hormonally regulated in a defined adrenal compartment, indicating a peripheral, ligand-responsive receptor rather than a purely central one.","evidence":"Semi-quantitative RT-PCR and RNase protection in bovine adrenal glomerulosa primary cells with ACTH/α-MSH/angiotensin II treatment","pmids":["10687856"],"confidence":"Low","gaps":["Expression measured by semi-quantitative methods only","No downstream signaling or functional consequence defined","Restricted to bovine adrenal tissue"]},{"year":2011,"claim":"Resolved which cell type requires MC5R for melanocortin-driven regulatory immunity, showing the receptor acts in APCs rather than T cells.","evidence":"MC5r-/- mice, APC isolation, co-culture cytokine assays and adoptive transfer in post-EAU spleen","pmids":["21989727"],"confidence":"Medium","gaps":["Signaling pathway downstream of MC5R in APCs not defined","Ligand driving APC MC5R activation in vivo not identified"]},{"year":2013,"claim":"Identified the effector pathway linking APC MC5R to Treg induction, defining a CD39/CD73 adenosinergic axis requiring T-cell A2A receptor.","evidence":"MC5r-/- and A2Ar-/- mouse epistasis, flow cytometry phenotyping, Treg induction assays","pmids":["24043903"],"confidence":"Medium","gaps":["Molecular link between MC5R signaling and CD39/CD73 expression not established","Generality beyond ocular autoimmunity untested"]},{"year":2016,"claim":"Demonstrated MC5R forms heterodimers with another melanocortin receptor, providing a mechanism for ligand-selective modulation of cAMP output.","evidence":"Reciprocal Co-IP, co-localization, and cAMP accumulation assays in CHO cells using barfin flounder MC1R/MC5R","pmids":["27080548"],"confidence":"Medium","gaps":["Shown in fish orthologs; conservation in mammalian MC5R not tested","Stoichiometry and structural basis of the heterodimer unknown"]},{"year":2017,"claim":"Mapped the determinants of MC5R cell surface delivery, separating trafficking control from dimerization.","evidence":"N-terminal deletion, site-directed mutagenesis (Ser4/Ser5, Ser17/Glu18), and ER/Golgi vs plasma membrane imaging","pmids":["28396017"],"confidence":"Medium","gaps":["Trafficking chaperones or machinery recognizing the N-terminal motifs not identified","Effect of mutations on downstream signaling not quantified"]},{"year":2021,"claim":"Revealed an MC5R requirement in epidermal homeostasis, linking the receptor to lipid secretion, barrier formation, and UVB-stress responses.","evidence":"MC5R knockout mice with transepidermal water loss, TEM ultrastructure, and cytokine measurement","pmids":["34909724"],"confidence":"Medium","gaps":["Signaling pathway in keratinocytes not defined","Mechanism connecting MC5R to lamellar granule biogenesis unknown"]},{"year":2023,"claim":"Defined a melanocortin/MC5R role in hematopoietic regeneration through PI3K/AKT and MAPK signaling.","evidence":"MC5R knockout plus irradiation injury model with pathway inhibitors, α-MSH rescue, and reconstitution assays","pmids":["36920787"],"confidence":"Medium","gaps":["Direct receptor-effector coupling in HSCs not biochemically resolved","Whether effect is HSC-intrinsic or niche-mediated not fully separated"]},{"year":2025,"claim":"Established podocyte MC5R as the cell-autonomous effector suppressing complement factors B and D via PPARγ, defining a therapeutic mechanism in membranous nephropathy.","evidence":"MC5R knockout with podocyte-specific reconstitution, selective agonist PG-901, complement and PPARγ pathway analysis","pmids":["40739753"],"confidence":"High","gaps":["Molecular link between MC5R signaling and PPARγ activation not detailed","Whether the same axis operates in human disease not established"]},{"year":2025,"claim":"Demonstrated MC5R mediates peripheral α-MSH-driven glucose uptake in skeletal muscle across species including humans.","evidence":"MC5R knockout mice, selective agonist PG-901 in glucose tolerance tests, glucose uptake in primary human/NHP myotubes, human OGTT (preprint)","pmids":["bio_10.1101_2025.03.26.645414"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","Intracellular signaling driving glucose uptake in myotubes not defined","GLUT transporter mechanism not resolved"]},{"year":null,"claim":"How a single melanocortin receptor coordinates such diverse tissue-specific outputs (immune, metabolic, renal, epidermal, hematopoietic) through distinct downstream effectors remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying signaling logic linking MC5R to cell-type-specific effectors (PPARγ, adenosinergic, GLUT, PI3K)","No structural model of human MC5R or its complexes","Endogenous ligand and bias determinants per tissue not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[4,6]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,6]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,3]}],"complexes":[],"partners":["MC1R"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P33032","full_name":"Melanocortin receptor 5","aliases":["MC-2"],"length_aa":325,"mass_kda":36.6,"function":"G protein-coupled receptor for melanocyte-stimulating hormones (alpha- beta- and gamma-MSH) and corticotropin/ACTH, which are peptide products of the POMC precursor (PubMed:37524700, PubMed:8396929). Upon activation, couples to G(s) protein, stimulating adenylate cyclase and the cAMP-dependent signaling pathway (PubMed:37524700). Also activates ERK1/2 via a PI3K-dependent signaling mechanism (PubMed:19428994). Order of potency of natural melanocortins in receptor activation is alpha-MSH > ACTH > beta-MSH > gamma-MSH (PubMed:8396929). Plays a key role in immune response, and is essential for temperature regulation and exocrine gland function (By similarity)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P33032/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MC5R","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/MC5R","total_profiled":1310},"omim":[{"mim_id":"600042","title":"MELANOCORTIN 5 RECEPTOR; MC5R","url":"https://www.omim.org/entry/600042"},{"mim_id":"102776","title":"ADENOSINE A2A RECEPTOR; ADORA2A","url":"https://www.omim.org/entry/102776"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"epididymis","ntpm":2.5},{"tissue":"lymphoid tissue","ntpm":1.0}],"url":"https://www.proteinatlas.org/search/MC5R"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P33032","domains":[{"cath_id":"1.20.1070.10","chopping":"35-306","consensus_level":"high","plddt":90.3511,"start":35,"end":306}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P33032","model_url":"https://alphafold.ebi.ac.uk/files/AF-P33032-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P33032-F1-predicted_aligned_error_v6.png","plddt_mean":82.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MC5R","jax_strain_url":"https://www.jax.org/strain/search?query=MC5R"},"sequence":{"accession":"P33032","fasta_url":"https://rest.uniprot.org/uniprotkb/P33032.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P33032/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P33032"}},"corpus_meta":[{"pmid":"24043903","id":"PMC_24043903","title":"Both MC5r and A2Ar are required for protective regulatory immunity in the spleen of post-experimental autoimmune uveitis in mice.","date":"2013","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/24043903","citation_count":64,"is_preprint":false},{"pmid":"21989727","id":"PMC_21989727","title":"Following EAU recovery there is an associated MC5r-dependent APC induction of regulatory immunity in the spleen.","date":"2011","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/21989727","citation_count":35,"is_preprint":false},{"pmid":"19100739","id":"PMC_19100739","title":"Modeling the evolution of the MC2R and MC5R genes: studies on the cartilaginous fish, Heterondotus francisci.","date":"2008","source":"General and comparative endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/19100739","citation_count":29,"is_preprint":false},{"pmid":"29277542","id":"PMC_29277542","title":"Evolution of the MC5R gene in placental mammals with evidence for its inactivation in multiple lineages that lack sebaceous glands.","date":"2017","source":"Molecular phylogenetics and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/29277542","citation_count":28,"is_preprint":false},{"pmid":"27886238","id":"PMC_27886238","title":"MC5r and A2Ar Deficiencies During Experimental Autoimmune Uveitis Identifies Distinct T cell Polarization Programs and a Biphasic Regulatory Response.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27886238","citation_count":27,"is_preprint":false},{"pmid":"27080548","id":"PMC_27080548","title":"Dimerization of melanocortin receptor 1 (MC1R) and MC5R creates a ligand-dependent signal modulation: Potential participation in physiological color change in the flounder.","date":"2016","source":"General and comparative endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/27080548","citation_count":21,"is_preprint":false},{"pmid":"30416452","id":"PMC_30416452","title":"The Melanocortin MC5R as a New Target for Treatment of High Glucose-Induced Hypertrophy of the Cardiac H9c2 Cells.","date":"2018","source":"Frontiers in physiology","url":"https://pubmed.ncbi.nlm.nih.gov/30416452","citation_count":20,"is_preprint":false},{"pmid":"7956366","id":"PMC_7956366","title":"Localization of the human melanocortin-5 receptor gene (MC5R) to chromosome band 18p11.2 by fluorescence in situ hybridization.","date":"1995","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/7956366","citation_count":20,"is_preprint":false},{"pmid":"20833220","id":"PMC_20833220","title":"γ₂-Melanocyte stimulation hormone (γ₂-MSH) truncation studies results in the cautionary note that γ₂-MSH is not selective for the mouse MC3R over the mouse MC5R.","date":"2010","source":"Peptides","url":"https://pubmed.ncbi.nlm.nih.gov/20833220","citation_count":19,"is_preprint":false},{"pmid":"10078851","id":"PMC_10078851","title":"Absence of genetic variation in some obesity candidate genes (GLP1R, ASIP, MC4R, MC5R) among Pima indians.","date":"1999","source":"International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity","url":"https://pubmed.ncbi.nlm.nih.gov/10078851","citation_count":17,"is_preprint":false},{"pmid":"9888520","id":"PMC_9888520","title":"Expression of ACTH receptors (MC2-R and MC5-R) in the glomerulosa and the fasciculata-reticularis zones of bovine adrenal cortex.","date":"1998","source":"Endocrine research","url":"https://pubmed.ncbi.nlm.nih.gov/9888520","citation_count":16,"is_preprint":false},{"pmid":"10687856","id":"PMC_10687856","title":"Expression and regulation of melanocortin receptor-5 (MC5-R) in the bovine adrenal cortex.","date":"2000","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/10687856","citation_count":12,"is_preprint":false},{"pmid":"36920787","id":"PMC_36920787","title":"Melanocortin/MC5R axis regulates the proliferation of hematopoietic stem cells in mice after ionizing radiation injury.","date":"2023","source":"Blood advances","url":"https://pubmed.ncbi.nlm.nih.gov/36920787","citation_count":9,"is_preprint":false},{"pmid":"37239994","id":"PMC_37239994","title":"Study on the Mechanism of MC5R Participating in Energy Metabolism of Goose Liver.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37239994","citation_count":8,"is_preprint":false},{"pmid":"28396017","id":"PMC_28396017","title":"Cell surface targeting of the Melanocortin 5 Receptor (MC5R) requires serine-rich terminal motifs.","date":"2017","source":"Biochimica et biophysica acta. Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/28396017","citation_count":6,"is_preprint":false},{"pmid":"35648215","id":"PMC_35648215","title":"Differential MC5R loss in whales and manatees reveals convergent evolution to the marine environment.","date":"2022","source":"Development genes and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/35648215","citation_count":6,"is_preprint":false},{"pmid":"35447133","id":"PMC_35447133","title":"Analyzing the Hypothalamus/Pituitary/Interrenal axis of the neopterygian fish, Lepisosteus oculatus: Co-localization of MC2R, MC5R, MRAP1, and MRAP2 in interrenal cells.","date":"2022","source":"General and comparative endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/35447133","citation_count":5,"is_preprint":false},{"pmid":"40739753","id":"PMC_40739753","title":"Intercepting the complement amplification loop through podocyte MC5R signaling ameliorates membranous nephropathy.","date":"2025","source":"Molecular therapy : the journal of the American Society of Gene Therapy","url":"https://pubmed.ncbi.nlm.nih.gov/40739753","citation_count":4,"is_preprint":false},{"pmid":"12530674","id":"PMC_12530674","title":"Expression of the melanocortin receptors MC2-R (ACTH-receptor) and MC5-R during embryonic development of ovine adrenals.","date":"2002","source":"Endocrine research","url":"https://pubmed.ncbi.nlm.nih.gov/12530674","citation_count":4,"is_preprint":false},{"pmid":"34909724","id":"PMC_34909724","title":"MC5R Contributes to Sensitivity to UVB Waves and Barrier Function in Mouse Epidermis.","date":"2021","source":"JID innovations : skin science from molecules to population health","url":"https://pubmed.ncbi.nlm.nih.gov/34909724","citation_count":3,"is_preprint":false},{"pmid":"37307241","id":"PMC_37307241","title":"Discovery of a Pan-Melanocortin Receptor Antagonist [Ac-DPhe(pI)-Arg-Nal(2')-Orn-NH2] at the MC1R, MC3R, MC4R, and MC5R that Mediates an Increased Feeding Response in Mice and a 40-Fold Selective MC1R Antagonist [Ac-DPhe(pI)-DArg-Nal(2')-Arg-NH2].","date":"2023","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37307241","citation_count":3,"is_preprint":false},{"pmid":"33128687","id":"PMC_33128687","title":"Molecular cloning and expression analysis of mc5r like genes (mc5rl) in Ruditapes philippinarum (Manila clam) after aerial exposure and low-temperature stress.","date":"2020","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/33128687","citation_count":0,"is_preprint":false},{"pmid":"40254355","id":"PMC_40254355","title":"From MC1R to MC5R, a new horizon for the podoprotective effect of melanocortin.","date":"2025","source":"Kidney international","url":"https://pubmed.ncbi.nlm.nih.gov/40254355","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.26.645414","title":"α-Melanocyte Stimulating Hormone Reduces Blood Glucose Across Species","date":"2025-03-29","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.26.645414","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13430,"output_tokens":2782,"usd":0.04101,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10191,"output_tokens":3058,"usd":0.063702,"stage2_stop_reason":"end_turn"},"total_usd":0.104712,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"MC5R and MC1R from barfin flounder form heterodimers at the plasma membrane. Co-immunoprecipitation showed bfMC1R and bfMC5R physically interact, and heterodimerization produces ligand-dependent inhibition of cAMP accumulation: α-MSH-induced cAMP was suppressed by coexpression of both receptors, whereas desacetyl-α-MSH was not inhibitory. This provides a mechanism for selective pigment dispersion in different chromatophore types.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, cAMP accumulation assay in CHO cells\",\n      \"journal\": \"General and comparative endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus functional cAMP assay in a single study; single lab, two orthogonal methods\",\n      \"pmids\": [\"27080548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Cell surface targeting of MC5R requires two serine-rich motifs in the N-terminal domain (residues Ser4/Ser5 and Ser17/Glu18). Site-directed mutagenesis of these residues caused retention of MC5R at the ER/Golgi complex rather than delivery to the plasma membrane. The first 21 amino acids contain the information required for correct trafficking, and homodimerization was unaffected by these mutations, indicating that surface targeting and dimerization are independent processes.\",\n      \"method\": \"N-terminal deletion analysis, site-directed mutagenesis, fluorescence microscopy of ER/Golgi vs. plasma membrane localization\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis plus subcellular localization imaging with functional trafficking readout; single lab, two orthogonal methods\",\n      \"pmids\": [\"28396017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MC5R expression is required on APCs (not T cells) to promote regulatory immunity in the spleen of EAU-recovering mice. APCs from wild-type EAU-recovering mice induced TGF-β expression and FoxP3+CD25+CD4+ Treg cell activation in IRBP-specific effector T cells from MC5r-/- mice, whereas APCs from MC5r-/- mice failed to do so. Adoptive transfer confirmed the APC-intrinsic dependence on MC5r.\",\n      \"method\": \"MC5r-/- mouse model, APC isolation, co-culture cytokine assays (ELISA, flow cytometry), adoptive transfer\",\n      \"journal\": \"Investigative ophthalmology & visual science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout epistasis plus adoptive transfer with functional readout; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"21989727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MC5r-dependent regulatory immunity in post-EAU spleen requires adenosine 2A receptor (A2Ar) expression on T cells. MC5r-dependent APCs were identified as CD11b+F4/80+Ly-6C(low)Ly-6G+CD39+CD73+ cells, and these APCs use the adenosinergic pathway to activate autoantigen-specific FoxP3+CD25+CD4+ regulatory T cells. Both MC5r and A2Ar are required for EAU-suppressing regulatory immunity.\",\n      \"method\": \"MC5r-/- and A2Ar-/- mouse models, flow cytometry, functional assays of Treg induction\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dual genetic knockout epistasis with defined cellular phenotype; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"24043903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The melanocortin/MC5R axis regulates proliferation of hematopoietic stem cells (HSCs) after irradiation via activation of the PI3K/AKT and MAPK signaling pathways. MC5R knockout aggravated irradiation-induced myelosuppression due to impaired HSC proliferation and reconstitution, and α-MSH treatment accelerated hematopoietic recovery in irradiated mice.\",\n      \"method\": \"MC5R knockout mouse model, irradiation injury model, pathway inhibitor assays (PI3K/AKT, MAPK), α-MSH treatment, colony/reconstitution assays\",\n      \"journal\": \"Blood advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout plus pharmacological rescue with pathway-level readout; single lab, multiple methods\",\n      \"pmids\": [\"36920787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Peripheral α-MSH promotes glucose uptake in skeletal muscle via an MC5R-dependent mechanism. A selective MC5R agonist (PG-901) reduced blood glucose during a glucose tolerance test in wild-type mice but had no effect in MC5R-deficient mice. Both α-MSH and PG-901 directly induced glucose uptake in primary human and non-human primate myotubes in vitro, and the pathway was functional in healthy human volunteers.\",\n      \"method\": \"MC5R knockout mouse model, glucose tolerance test, in vitro glucose uptake assay in primary human myotubes, human oral glucose tolerance test with α-MSH administration\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout abolishes effect, selective agonist in multiple species including human; single study, multiple orthogonal methods; preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.03.26.645414\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Podocyte MC5R intercepts the complement amplification loop in membranous nephropathy by inhibiting podocyte expression of complement factors B and D via a PPARγ-dependent mechanism. MC5R knockout exacerbated glomerular C5b-9 and C3 fixation, whereas MC5R agonism diminished it. Podocyte-specific reconstitution of MC5R in MC5R knockout mice restored melanocortin therapeutic efficacy, establishing podocyte MC5R as the critical cell-autonomous effector.\",\n      \"method\": \"MC5R knockout mouse model, podocyte-specific MC5R reconstitution, selective MC5R agonist (PG-901), complement cascade analysis, PPARγ pathway analysis, cultured podocyte assays\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific reconstitution plus pharmacological agonism/antagonism, multiple orthogonal mechanistic readouts (complement factors, PPARγ), single rigorous study\",\n      \"pmids\": [\"40739753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MC5R stimulation in high-glucose-exposed cardiac H9c2 cells reduces hypertrophy by activating PI3K signaling and decreasing the GLUT1/GLUT4 ratio on the cell membrane, mediated by a reduction in miR-133a levels.\",\n      \"method\": \"MC5R agonist (α-MSH, PG-901) treatment of H9c2 cells, PI3K activity assay, GLUT1/GLUT4 quantification, miR-133a measurement, streptozotocin-diabetic rat echocardiography\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pharmacological agonism with pathway readouts but no receptor-specific genetic ablation; single lab, mechanistic pathway partially characterized\",\n      \"pmids\": [\"30416452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"MC5-R in bovine adrenal glomerulosa cells is upregulated by ACTH, α-MSH, and angiotensin II (7-, 5-, and 4.5-fold respectively) at the mRNA level, and MC5-R is expressed exclusively in the glomerulosa zone (not fasciculata) of adult adrenal cortex, at levels at least 100-fold lower than MC2-R.\",\n      \"method\": \"Semi-quantitative RT-PCR, RNase protection assay, primary adrenocortical cell culture with hormone treatment\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — expression/regulation in primary cells by semi-quantitative methods; single lab, no functional downstream mechanism defined\",\n      \"pmids\": [\"10687856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MC5R deficiency in mice leads to impaired epidermal barrier function, characterized by increased transepidermal water loss, fewer lamellar granules, reduced lipid secretion, and expansion of the trans-Golgi network in epidermal cells. MC5R-deficient mice also showed increased UVB sensitivity with enhanced inflammatory cell infiltration and elevated IL-6 but reduced IL-10.\",\n      \"method\": \"MC5R knockout mouse model, transepidermal water loss measurement, dye exclusion assay, transmission electron microscopy, cytokine measurement\",\n      \"journal\": \"JID innovations\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with ultrastructural (TEM) and functional barrier readouts; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"34909724\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MC5R is a G protein-coupled receptor that signals through cAMP and PI3K/AKT/MAPK pathways; its cell surface trafficking requires N-terminal Ser4/Ser5 and Ser17/Glu18 motifs; it acts on APCs to promote adenosinergic Treg induction during ocular autoimmunity; it mediates α-MSH-driven glucose uptake in skeletal muscle; it protects podocytes in membranous nephropathy by suppressing complement factors B and D via a PPARγ-dependent mechanism; and it supports hematopoietic stem cell proliferation and epidermal barrier function under stress conditions.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MC5R is a melanocortin G protein-coupled receptor that couples α-MSH and related melanocortin ligands to cAMP and PI3K/AKT/MAPK signaling to control diverse peripheral cellular responses [#4, #8]. Its activity is set at the cell surface: delivery of MC5R to the plasma membrane requires two N-terminal serine-rich motifs (Ser4/Ser5 and Ser17/Glu18), and mutation of these residues traps the receptor at the ER/Golgi, a process independent of its capacity to dimerize [#1]. MC5R can engage other melanocortin receptors physically, forming heterodimers with MC1R that confer ligand-dependent suppression of cAMP signaling [#0]. Functionally, MC5R operates as a cell-autonomous effector across tissues: on antigen-presenting cells it drives adenosinergic induction of FoxP3+ regulatory T cells via A2A receptor signaling to enforce ocular regulatory immunity [#2, #3]; in skeletal muscle it mediates melanocortin-driven glucose uptake [#5]; in podocytes it suppresses complement factors B and D through a PPARγ-dependent mechanism to intercept the complement amplification loop in membranous nephropathy [#6]; and it supports hematopoietic stem cell proliferation after irradiation through PI3K/AKT and MAPK activation [#4]. MC5R is also required for epidermal barrier integrity and lamellar granule-mediated lipid secretion [#9]. No structural model of human MC5R or its signaling complex is characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that MC5R is expressed and hormonally regulated in a defined adrenal compartment, indicating a peripheral, ligand-responsive receptor rather than a purely central one.\",\n      \"evidence\": \"Semi-quantitative RT-PCR and RNase protection in bovine adrenal glomerulosa primary cells with ACTH/α-MSH/angiotensin II treatment\",\n      \"pmids\": [\"10687856\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Expression measured by semi-quantitative methods only\", \"No downstream signaling or functional consequence defined\", \"Restricted to bovine adrenal tissue\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Resolved which cell type requires MC5R for melanocortin-driven regulatory immunity, showing the receptor acts in APCs rather than T cells.\",\n      \"evidence\": \"MC5r-/- mice, APC isolation, co-culture cytokine assays and adoptive transfer in post-EAU spleen\",\n      \"pmids\": [\"21989727\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling pathway downstream of MC5R in APCs not defined\", \"Ligand driving APC MC5R activation in vivo not identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified the effector pathway linking APC MC5R to Treg induction, defining a CD39/CD73 adenosinergic axis requiring T-cell A2A receptor.\",\n      \"evidence\": \"MC5r-/- and A2Ar-/- mouse epistasis, flow cytometry phenotyping, Treg induction assays\",\n      \"pmids\": [\"24043903\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between MC5R signaling and CD39/CD73 expression not established\", \"Generality beyond ocular autoimmunity untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated MC5R forms heterodimers with another melanocortin receptor, providing a mechanism for ligand-selective modulation of cAMP output.\",\n      \"evidence\": \"Reciprocal Co-IP, co-localization, and cAMP accumulation assays in CHO cells using barfin flounder MC1R/MC5R\",\n      \"pmids\": [\"27080548\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Shown in fish orthologs; conservation in mammalian MC5R not tested\", \"Stoichiometry and structural basis of the heterodimer unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Mapped the determinants of MC5R cell surface delivery, separating trafficking control from dimerization.\",\n      \"evidence\": \"N-terminal deletion, site-directed mutagenesis (Ser4/Ser5, Ser17/Glu18), and ER/Golgi vs plasma membrane imaging\",\n      \"pmids\": [\"28396017\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking chaperones or machinery recognizing the N-terminal motifs not identified\", \"Effect of mutations on downstream signaling not quantified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed an MC5R requirement in epidermal homeostasis, linking the receptor to lipid secretion, barrier formation, and UVB-stress responses.\",\n      \"evidence\": \"MC5R knockout mice with transepidermal water loss, TEM ultrastructure, and cytokine measurement\",\n      \"pmids\": [\"34909724\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signaling pathway in keratinocytes not defined\", \"Mechanism connecting MC5R to lamellar granule biogenesis unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a melanocortin/MC5R role in hematopoietic regeneration through PI3K/AKT and MAPK signaling.\",\n      \"evidence\": \"MC5R knockout plus irradiation injury model with pathway inhibitors, α-MSH rescue, and reconstitution assays\",\n      \"pmids\": [\"36920787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct receptor-effector coupling in HSCs not biochemically resolved\", \"Whether effect is HSC-intrinsic or niche-mediated not fully separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established podocyte MC5R as the cell-autonomous effector suppressing complement factors B and D via PPARγ, defining a therapeutic mechanism in membranous nephropathy.\",\n      \"evidence\": \"MC5R knockout with podocyte-specific reconstitution, selective agonist PG-901, complement and PPARγ pathway analysis\",\n      \"pmids\": [\"40739753\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between MC5R signaling and PPARγ activation not detailed\", \"Whether the same axis operates in human disease not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated MC5R mediates peripheral α-MSH-driven glucose uptake in skeletal muscle across species including humans.\",\n      \"evidence\": \"MC5R knockout mice, selective agonist PG-901 in glucose tolerance tests, glucose uptake in primary human/NHP myotubes, human OGTT (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.03.26.645414\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"Intracellular signaling driving glucose uptake in myotubes not defined\", \"GLUT transporter mechanism not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single melanocortin receptor coordinates such diverse tissue-specific outputs (immune, metabolic, renal, epidermal, hematopoietic) through distinct downstream effectors remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying signaling logic linking MC5R to cell-type-specific effectors (PPARγ, adenosinergic, GLUT, PI3K)\", \"No structural model of human MC5R or its complexes\", \"Endogenous ligand and bias determinants per tissue not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"GO:0004930\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MC1R\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}