{"gene":"SGMS2","run_date":"2026-06-10T07:46:31","timeline":{"discoveries":[{"year":2007,"finding":"SMS1 localizes to the Golgi and SMS2 localizes to the plasma membrane, and both function as the key SM synthases in HeLa cells; RNA interference-mediated depletion of either SMS1 or SMS2 caused decreased SM production, ceramide accumulation, and a block in cell growth.","method":"RNA interference (siRNA knockdown), lipid analysis, cell growth assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional depletion with multiple orthogonal readouts (lipid levels, growth, localization), replicated across two isoforms","pmids":["17449912"],"is_preprint":false},{"year":2009,"finding":"SMS2 is a bifunctional enzyme with both sphingomyelin (SM) synthase and ceramide phosphoethanolamine (CPE) synthase activity, distinguishing it from SMS1 (SM synthase only) and SMSr (CPE synthase only); both SM and CPE synthase activities are enhanced at the surface of SMS2-overexpressing HeLa cells.","method":"In vitro enzymatic assay, substrate specificity profiling, overexpression in HeLa cells, surface activity measurement","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical in vitro activity assay with mutagenesis-equivalent substrate specificity characterization and cellular validation","pmids":["19454763"],"is_preprint":false},{"year":2019,"finding":"The SGMS2 nonsense variant p.Arg50* yields a catalytically inactive SMS2 enzyme, while missense variants p.Ile62Ser and p.Met64Arg enhance de novo sphingomyelin production by blocking ER export of a functional enzyme, thereby causing aberrant ER retention of enzymatically active SMS2.","method":"Functional enzymatic assays of mutant proteins, cellular localization studies, patient-derived variant characterization","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct enzymatic activity assay of mutant variants combined with ER export/localization studies in a single study","pmids":["30779713"],"is_preprint":false},{"year":2022,"finding":"Pathogenic SMS2 variants linked to severe bone phenotypes retain full enzymatic activity but fail to exit the ER due to a defective autonomous ER export signal; cells harboring these variants accumulate sphingomyelin in the ER, display disrupted transbilayer sphingomyelin asymmetry, and show imbalances in cholesterol organization and glycerophospholipid profiles in the secretory pathway.","method":"Biochemical enzymatic activity assays, fluorescence-based lipid imaging, lipidomics, patient-derived fibroblast analysis, ER export signal characterization","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (enzymatic assay, lipid imaging, lipidomics) in patient-derived cells and engineered cell lines","pmids":["36102623"],"is_preprint":false},{"year":2010,"finding":"SMS2 deficiency in knockout mice attenuates LPS-induced lung injury; loss of SMS2 decreased MAP kinase-JNK activation and reduced pulmonary neutrophil influx and inflammation.","method":"SMS2 knockout mouse model, LPS-induced lung injury model, cytokine measurement, MAP kinase signaling analysis","journal":"American journal of physiology. Lung cellular and molecular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cellular phenotype and signaling pathway readout, single lab","pmids":["21191108"],"is_preprint":false},{"year":2011,"finding":"SMS2 deficiency in mouse brain significantly decreases mRNA and protein expression of P-glycoprotein (Pgp/Mdr1) drug transporter, and reduces ezrin and β-actin expression; co-immunoprecipitation showed association between Pgp, ezrin, and β-actin in brain lysate.","method":"RT-PCR, western blot, immunohistochemistry, co-immunoprecipitation, SMS2 knockout mouse brain","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — SMS2 KO with multiple readouts and Co-IP showing Pgp/ezrin/β-actin interaction, single lab","pmids":["21554861"],"is_preprint":false},{"year":2021,"finding":"Upregulated SMS2 in anti-dsDNA germinal center B cells induces apoptosis by directly activating protein kinase C delta (PKCδ) pro-apoptotic activity, serving as a B cell tolerance checkpoint; pharmacological stimulation of this pathway inhibited lupus pathogenesis in lupus-prone mice.","method":"SMS2 overexpression/knockdown in B cells, PKCδ activity assay, SMS2 knockout mice, lupus mouse models (C57BL/6 and NZBWF1)","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function and gain-of-function with defined apoptotic pathway readout (PKCδ activation), in vivo pharmacological validation, single lab","pmids":["34469734"],"is_preprint":false},{"year":2021,"finding":"SMS2 deficiency in platelets reduces platelet aggregation, spreading, clot retraction, and in vivo thrombosis; the PLCγ/PI3K/Akt signaling pathway is inhibited in SMS2-/- platelets and in platelets treated with SMS2 inhibitor D609.","method":"SMS2 knockout mouse platelets, pharmacological inhibition with D609, platelet aggregation assays, in vivo thrombosis model, signaling pathway analysis","journal":"Thrombosis journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with defined functional and signaling pathway phenotype, confirmed with pharmacological inhibitor, single lab","pmids":["33910580"],"is_preprint":false},{"year":2024,"finding":"SMS2 siRNA inhibition suppresses pancreatic tumor growth by modulating tumor-associated macrophage polarization and reducing tumor-associated neutrophil infiltration via regulation of the NF-κB/CXCL5 pathway.","method":"Self-assembling SMS2 siRNA in vivo delivery, murine Panc02 pancreatic carcinoma model, immune cell profiling, NF-κB/CXCL5 pathway analysis","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo siRNA knockdown with defined immune and signaling pathway readouts, single lab","pmids":["39255679"],"is_preprint":false},{"year":2025,"finding":"SMS2 inhibition (via inhibitor Ly93) suppresses endothelial-to-mesenchymal transition (EndMT) by blocking the Wnt/β-catenin pathway, which attenuates PPARγ ubiquitination-mediated degradation through PPARγ-β-catenin interaction, ultimately reducing CPT1A expression and fatty acid oxidation; endothelial-specific SMS2 overexpression in ApoE-/- mice enhances atherosclerosis.","method":"Pharmacological SMS2 inhibition, RNA sequencing, endothelial cell-specific SMS2 overexpression in ApoE-/- mice, EndMT marker analysis, Wnt/β-catenin and PPARγ pathway assays, human atherosclerotic plaque analysis","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (pharmacological inhibition, in vivo overexpression, RNA-seq, pathway assays) in single lab study","pmids":["41988717"],"is_preprint":false},{"year":2025,"finding":"SPNS2 knockdown in endothelial cells upregulates SMS2 expression, leading to increased sphingomyelin synthesis and endothelial-to-mesenchymal transition (EndMT); exogenous sphingomyelinase, which degrades SM, reverses the SPNS2 knockdown-induced EndMT.","method":"siRNA knockdown of SPNS2, exogenous SM addition and sphingomyelinase treatment, EndMT marker analysis, sphingolipid metabolic profiling","journal":"Cellular and molecular biology (Noisy-le-Grand, France)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, indirect evidence for SMS2 role (via upstream SPNS2 manipulation), no direct SMS2 loss-of-function experiment","pmids":["39910932"],"is_preprint":false},{"year":2025,"finding":"Uric acid upregulates SMS2 expression in endothelial cells; SMS2 siRNA knockdown reverses uric acid-induced apoptosis, impaired migration, diminished angiogenic potential, ER stress marker elevation, and intracellular calcium disruption.","method":"siRNA knockdown of SMS2 in HUVEC cells, uric acid cytotoxicity assay, ER stress marker analysis, calcium homeostasis measurement, functional assays (migration, angiogenesis)","journal":"Toxicology in vitro","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, siRNA knockdown with functional phenotypes but pathway placement remains correlative","pmids":["40865887"],"is_preprint":false}],"current_model":"SGMS2 encodes sphingomyelin synthase 2 (SMS2), a plasma membrane-resident bifunctional enzyme that catalyzes transfer of phosphocholine from phosphatidylcholine to ceramide to produce sphingomyelin (SM), and also possesses ceramide phosphoethanolamine (CPE) synthase activity; it maintains the SM/cholesterol gradient along the secretory pathway via an autonomous ER export signal, and its activity regulates ceramide levels, lipid raft integrity, PKCδ-mediated B cell apoptosis, PLCγ/PI3K/Akt platelet signaling, Wnt/β-catenin-dependent endothelial-to-mesenchymal transition, NF-κB/CXCL5-dependent tumor immune microenvironment, and P-glycoprotein expression in the brain, with loss-of-function or ER-retaining gain-of-function variants causing defective bone mineralization and osteoporosis/skeletal dysplasia."},"narrative":{"mechanistic_narrative":"SGMS2 encodes sphingomyelin synthase 2 (SMS2), a plasma membrane-resident enzyme that, together with the Golgi-localized SMS1, constitutes the principal sphingomyelin (SM) synthase activity of the cell, transferring phosphocholine to ceramide so that its depletion lowers SM, drives ceramide accumulation, and arrests cell growth [PMID:17449912]. Distinct from its paralogs, SMS2 is bifunctional, possessing both SM synthase and ceramide phosphoethanolamine (CPE) synthase activities at the cell surface [PMID:19454763]. SMS2 carries an autonomous ER export signal that governs its trafficking to the plasma membrane; pathogenic SGMS2 variants either abolish catalytic activity (p.Arg50*) or, while remaining fully active, disrupt this export signal (p.Ile62Ser, p.Met64Arg), causing ER retention, ectopic SM accumulation in the ER, disrupted transbilayer SM asymmetry, and imbalanced cholesterol and glycerophospholipid organization along the secretory pathway, which underlies severe bone mineralization defects and skeletal dysplasia/osteoporosis [PMID:30779713, PMID:36102623]. Through its control of membrane sphingolipid composition, SMS2 modulates multiple signaling outputs: it activates pro-apoptotic PKCδ as a germinal-center B-cell tolerance checkpoint [PMID:34469734], supports PLCγ/PI3K/Akt-dependent platelet activation and thrombosis [PMID:33910580], drives Wnt/β-catenin-dependent endothelial-to-mesenchymal transition and atherosclerosis [PMID:41988717], and shapes the tumor immune microenvironment via NF-κB/CXCL5 signaling [PMID:39255679]. In mice, SMS2 loss attenuates LPS-induced lung injury by dampening JNK MAP-kinase activation [PMID:21191108] and reduces brain expression of the P-glycoprotein drug transporter [PMID:21554861].","teleology":[{"year":2007,"claim":"Established that SMS2 is a bona fide sphingomyelin synthase whose activity is required for SM homeostasis and cell proliferation, defining its core metabolic role and plasma-membrane localization.","evidence":"siRNA depletion of SMS1/SMS2 in HeLa cells with lipid analysis, growth assays, and localization","pmids":["17449912"],"confidence":"High","gaps":["Did not resolve catalytic mechanism or substrate determinants","Growth arrest mechanism (ceramide vs. SM loss) not dissected"]},{"year":2009,"claim":"Distinguished SMS2 biochemically from its paralogs by showing it is dual-function, producing both SM and CPE, refining the enzymatic identity of the SMS family.","evidence":"In vitro enzymatic assays with substrate specificity profiling and surface activity measurement in SMS2-overexpressing HeLa cells","pmids":["19454763"],"confidence":"High","gaps":["Physiological significance of CPE synthase activity not established","No structural basis for dual substrate use"]},{"year":2019,"claim":"Linked SGMS2 variants to a skeletal disease and showed two distinct molecular mechanisms — catalytic loss versus ER retention of active enzyme — explaining how both loss- and gain-of-function alleles cause pathology.","evidence":"Functional enzymatic assays and localization studies of patient-derived variants","pmids":["30779713"],"confidence":"High","gaps":["Tissue-level mechanism connecting SM dysregulation to bone mineralization unresolved","ER export signal not yet mapped"]},{"year":2022,"claim":"Identified an autonomous ER export signal in SMS2 and showed that its disruption causes ER SM accumulation and broad secretory-pathway lipid imbalance, providing the membrane-biology mechanism behind the gain-of-function skeletal phenotype.","evidence":"Enzymatic assays, fluorescence lipid imaging, lipidomics in patient-derived fibroblasts and engineered cells","pmids":["36102623"],"confidence":"High","gaps":["How ER lipid imbalance impairs osteoblast/bone function not shown","Trafficking machinery recognizing the export signal unidentified"]},{"year":2011,"claim":"Connected SMS2 activity to expression of the P-glycoprotein drug transporter in brain, implicating sphingomyelin metabolism in transporter regulation.","evidence":"RT-PCR, western blot, IHC, and Co-IP in SMS2 knockout mouse brain","pmids":["21554861"],"confidence":"Medium","gaps":["Mechanism linking SM to Pgp/ezrin/actin expression not defined","Single Co-IP without reciprocal validation"]},{"year":2010,"claim":"Demonstrated an inflammatory role for SMS2, where its loss attenuates LPS-induced lung injury via reduced JNK signaling, extending SMS2 function to innate immune signaling.","evidence":"SMS2 knockout mouse LPS lung injury model with MAP kinase and neutrophil readouts","pmids":["21191108"],"confidence":"Medium","gaps":["Direct link between SM/ceramide changes and JNK activation not established","Cell type responsible not isolated"]},{"year":2021,"claim":"Defined SMS2 as a B-cell tolerance checkpoint by showing it drives PKCδ-mediated apoptosis of autoreactive germinal-center B cells, with therapeutic relevance in lupus.","evidence":"SMS2 gain/loss of function in B cells, PKCδ activity assays, knockout and lupus mouse models","pmids":["34469734"],"confidence":"Medium","gaps":["Molecular link between SM synthesis and PKCδ activation unresolved","Single lab"]},{"year":2021,"claim":"Showed SMS2 supports platelet activation and thrombosis through the PLCγ/PI3K/Akt pathway, broadening its signaling role to hemostasis.","evidence":"SMS2 knockout platelets and D609 inhibition in aggregation and in vivo thrombosis assays","pmids":["33910580"],"confidence":"Medium","gaps":["How membrane SM modulates PLCγ/PI3K/Akt not mechanistically defined","D609 specificity is a confound"]},{"year":2024,"claim":"Implicated SMS2 in shaping the tumor immune microenvironment via NF-κB/CXCL5, identifying it as a candidate target in pancreatic cancer.","evidence":"In vivo SMS2 siRNA delivery in murine Panc02 model with immune profiling","pmids":["39255679"],"confidence":"Medium","gaps":["Direct effect of SMS2 on tumor vs. immune cells not separated","NF-κB/CXCL5 link correlative"]},{"year":2025,"claim":"Placed SMS2 upstream of Wnt/β-catenin-driven endothelial-to-mesenchymal transition and atherosclerosis, mechanistically tying it to PPARγ stability and fatty acid oxidation.","evidence":"Pharmacological SMS2 inhibition, RNA-seq, endothelial-specific overexpression in ApoE-/- mice, pathway assays, human plaque analysis","pmids":["41988717"],"confidence":"Medium","gaps":["How SM synthesis activates Wnt/β-catenin not resolved","Single lab"]},{"year":2025,"claim":"Provided context that SMS2 acts downstream of SPNS2 and that uric acid stress upregulates SMS2 in endothelial cells, supporting a role in endothelial dysfunction, though through indirect or correlative manipulations.","evidence":"siRNA knockdown of SPNS2 or SMS2 in endothelial cells with SM/sphingomyelinase manipulation and functional/ER-stress readouts","pmids":["39910932","40865887"],"confidence":"Low","gaps":["SPNS2 study lacks direct SMS2 loss-of-function","Pathway placement remains correlative"]},{"year":null,"claim":"How SMS2-controlled changes in plasma-membrane and ER sphingomyelin are mechanistically transduced into the diverse downstream pathways (PKCδ, PLCγ/PI3K/Akt, Wnt/β-catenin, NF-κB) and into bone mineralization remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying mechanism linking membrane lipid changes to specific signaling outputs","Tissue-specific basis of skeletal disease unexplained","No structural model of SMS2"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,2,3]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,1,3]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,7,9]}],"complexes":[],"partners":[],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NHU3","full_name":"Phosphatidylcholine:ceramide cholinephosphotransferase 2","aliases":["Sphingomyelin synthase 2","SMS2"],"length_aa":365,"mass_kda":42.3,"function":"Sphingomyelin synthase that primarily contributes to sphingomyelin synthesis and homeostasis at the plasma membrane. Catalyzes the reversible transfer of phosphocholine moiety in sphingomyelin biosynthesis: in the forward reaction transfers phosphocholine head group of phosphatidylcholine (PC) on to ceramide (CER) to form ceramide phosphocholine (sphingomyelin, SM) and diacylglycerol (DAG) as by-product, and in the reverse reaction transfers phosphocholine from SM to DAG to form PC and CER (PubMed:14685263, PubMed:17449912, PubMed:17982138, PubMed:18370930, PubMed:38388831). The direction of the reaction appears to depend on the levels of CER and DAG in the plasma membrane (PubMed:14685263, PubMed:17449912, PubMed:17982138, PubMed:18370930). Does not use free phosphorylcholine or CDP-choline as donors (PubMed:14685263). Can also transfer phosphoethanolamine head group of phosphatidylethanolamine (PE) on to ceramide (CER) to form ceramide phosphoethanolamine (CPE) (PubMed:19454763). Regulates receptor-mediated signal transduction via mitogenic DAG and proapoptotic CER, as well as via SM, a structural component of membrane rafts that serve as platforms for signal transduction and protein sorting (PubMed:17449912, PubMed:17982138). To a lesser extent, plays a role in secretory transport via regulation of DAG pool at the Golgi apparatus and its downstream effects on PRKD1 (PubMed:18370930, PubMed:21980337). Required for normal bone matrix mineralization (PubMed:30779713)","subcellular_location":"Cell membrane; Golgi apparatus membrane","url":"https://www.uniprot.org/uniprotkb/Q8NHU3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SGMS2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SGMS2","total_profiled":1310},"omim":[{"mim_id":"611574","title":"SPHINGOMYELIN SYNTHASE 2; SGMS2","url":"https://www.omim.org/entry/611574"},{"mim_id":"166260","title":"GNATHODIAPHYSEAL DYSPLASIA; GDD","url":"https://www.omim.org/entry/166260"},{"mim_id":"126550","title":"CALVARIAL DOUGHNUT LESIONS WITH BONE FRAGILITY; CDL","url":"https://www.omim.org/entry/126550"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Golgi apparatus","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SGMS2"},"hgnc":{"alias_symbol":["MGC26963","SMS2"],"prev_symbol":[]},"alphafold":{"accession":"Q8NHU3","domains":[{"cath_id":"-","chopping":"75-322","consensus_level":"medium","plddt":89.9721,"start":75,"end":322}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NHU3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NHU3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NHU3-F1-predicted_aligned_error_v6.png","plddt_mean":76.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SGMS2","jax_strain_url":"https://www.jax.org/strain/search?query=SGMS2"},"sequence":{"accession":"Q8NHU3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NHU3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NHU3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NHU3"}},"corpus_meta":[{"pmid":"17449912","id":"PMC_17449912","title":"Both sphingomyelin synthases SMS1 and SMS2 are required for sphingomyelin homeostasis and growth in human HeLa cells.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17449912","citation_count":189,"is_preprint":false},{"pmid":"30779713","id":"PMC_30779713","title":"Osteoporosis and skeletal dysplasia caused by pathogenic variants in SGMS2.","date":"2019","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/30779713","citation_count":63,"is_preprint":false},{"pmid":"19454763","id":"PMC_19454763","title":"Sphingomyelin synthase SMS2 displays dual activity as ceramide phosphoethanolamine synthase.","date":"2009","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/19454763","citation_count":61,"is_preprint":false},{"pmid":"21191108","id":"PMC_21191108","title":"Sphingomyelin synthase 2 (SMS2) deficiency attenuates LPS-induced lung injury.","date":"2010","source":"American journal of physiology. Lung cellular and molecular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/21191108","citation_count":45,"is_preprint":false},{"pmid":"30646599","id":"PMC_30646599","title":"The Opposing Contribution of SMS1 and SMS2 to Glioma Progression and Their Value in the Therapeutic Response to 2OHOA.","date":"2019","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/30646599","citation_count":31,"is_preprint":false},{"pmid":"21554861","id":"PMC_21554861","title":"The effect of sphingomyelin synthase 2 (SMS2) deficiency on the expression of drug transporters in mouse brain.","date":"2011","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21554861","citation_count":30,"is_preprint":false},{"pmid":"36102623","id":"PMC_36102623","title":"Pathogenic variants of sphingomyelin synthase SMS2 disrupt lipid landscapes in the secretory pathway.","date":"2022","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/36102623","citation_count":25,"is_preprint":false},{"pmid":"36691044","id":"PMC_36691044","title":"LARP6 suppresses colorectal cancer progression through ZNF267/SGMS2-mediated imbalance of sphingomyelin synthesis.","date":"2023","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/36691044","citation_count":21,"is_preprint":false},{"pmid":"29222099","id":"PMC_29222099","title":"Isolation of the (+)-Pinoresinol-Mineralizing Pseudomonas sp. 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Strain SG-MS2.","date":"2020","source":"Applied and environmental microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/32198167","citation_count":11,"is_preprint":false},{"pmid":"37886644","id":"PMC_37886644","title":"SGMS2 in primary osteoporosis with facial nerve palsy.","date":"2023","source":"Frontiers in endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/37886644","citation_count":10,"is_preprint":false},{"pmid":"33910580","id":"PMC_33910580","title":"The role of Sphingomyelin synthase 2 (SMS2) in platelet activation and its clinical significance.","date":"2021","source":"Thrombosis journal","url":"https://pubmed.ncbi.nlm.nih.gov/33910580","citation_count":8,"is_preprint":false},{"pmid":"39255679","id":"PMC_39255679","title":"SMS2 siRNA inhibits pancreatic tumor growth by tumor microenvironment modulation.","date":"2024","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/39255679","citation_count":5,"is_preprint":false},{"pmid":"37175737","id":"PMC_37175737","title":"Clinical and Genetic Characteristics of Calvarial Doughnut Lesions with Bone Fragility in Three Families with a Reccurent SGMS2 Gene Variant.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37175737","citation_count":5,"is_preprint":false},{"pmid":"38732433","id":"PMC_38732433","title":"SMS2, a Novel Allele of OsINV3, Regulates Grain Size in Rice.","date":"2024","source":"Plants (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/38732433","citation_count":4,"is_preprint":false},{"pmid":"40123745","id":"PMC_40123745","title":"A novel SGMS2 mutation associated with high bone mass; description of an affected family with recurrent fragility fractures.","date":"2025","source":"Bone reports","url":"https://pubmed.ncbi.nlm.nih.gov/40123745","citation_count":4,"is_preprint":false},{"pmid":"37407394","id":"PMC_37407394","title":"Hsa_circ_0000129 knockdown attenuates proliferation and migration in keloid fibroblasts by targeting miR-485-3p/SGMS2 pathway.","date":"2023","source":"Burns : journal of the International Society for Burn Injuries","url":"https://pubmed.ncbi.nlm.nih.gov/37407394","citation_count":3,"is_preprint":false},{"pmid":"39910932","id":"PMC_39910932","title":"The loss of Spinster homolog 2 drives endothelial mesenchymal transition via SMS2-mediated disruption of sphingomyelin metabolism.","date":"2025","source":"Cellular and molecular biology (Noisy-le-Grand, France)","url":"https://pubmed.ncbi.nlm.nih.gov/39910932","citation_count":2,"is_preprint":false},{"pmid":"40978119","id":"PMC_40978119","title":"Transcriptomic and lipidomic profiling provide novel insight into the pathogenesis of monogenic SGMS2-related osteoporosis.","date":"2025","source":"JBMR plus","url":"https://pubmed.ncbi.nlm.nih.gov/40978119","citation_count":1,"is_preprint":false},{"pmid":"40865887","id":"PMC_40865887","title":"Hyperuricemia impairs endothelial function through SMS2-dependent activation of the endoplasmic reticulum stress response.","date":"2025","source":"Toxicology in vitro : an international journal published in association with BIBRA","url":"https://pubmed.ncbi.nlm.nih.gov/40865887","citation_count":1,"is_preprint":false},{"pmid":"41988717","id":"PMC_41988717","title":"Inhibiting Endothelial SMS2 Alleviates Atherosclerosis by Blocking Endothelial‑Mesenchymal Transition Through Boosted Fatty Acid Oxidation.","date":"2026","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/41988717","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.12.642613","title":"Human growth plates house resting zone sub-populations with features of quiescent stem cells","date":"2025-03-14","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.12.642613","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16014,"output_tokens":2986,"usd":0.046416,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10571,"output_tokens":3613,"usd":0.07159,"stage2_stop_reason":"end_turn"},"total_usd":0.118006,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"SMS1 localizes to the Golgi and SMS2 localizes to the plasma membrane, and both function as the key SM synthases in HeLa cells; RNA interference-mediated depletion of either SMS1 or SMS2 caused decreased SM production, ceramide accumulation, and a block in cell growth.\",\n      \"method\": \"RNA interference (siRNA knockdown), lipid analysis, cell growth assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional depletion with multiple orthogonal readouts (lipid levels, growth, localization), replicated across two isoforms\",\n      \"pmids\": [\"17449912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SMS2 is a bifunctional enzyme with both sphingomyelin (SM) synthase and ceramide phosphoethanolamine (CPE) synthase activity, distinguishing it from SMS1 (SM synthase only) and SMSr (CPE synthase only); both SM and CPE synthase activities are enhanced at the surface of SMS2-overexpressing HeLa cells.\",\n      \"method\": \"In vitro enzymatic assay, substrate specificity profiling, overexpression in HeLa cells, surface activity measurement\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical in vitro activity assay with mutagenesis-equivalent substrate specificity characterization and cellular validation\",\n      \"pmids\": [\"19454763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The SGMS2 nonsense variant p.Arg50* yields a catalytically inactive SMS2 enzyme, while missense variants p.Ile62Ser and p.Met64Arg enhance de novo sphingomyelin production by blocking ER export of a functional enzyme, thereby causing aberrant ER retention of enzymatically active SMS2.\",\n      \"method\": \"Functional enzymatic assays of mutant proteins, cellular localization studies, patient-derived variant characterization\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct enzymatic activity assay of mutant variants combined with ER export/localization studies in a single study\",\n      \"pmids\": [\"30779713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Pathogenic SMS2 variants linked to severe bone phenotypes retain full enzymatic activity but fail to exit the ER due to a defective autonomous ER export signal; cells harboring these variants accumulate sphingomyelin in the ER, display disrupted transbilayer sphingomyelin asymmetry, and show imbalances in cholesterol organization and glycerophospholipid profiles in the secretory pathway.\",\n      \"method\": \"Biochemical enzymatic activity assays, fluorescence-based lipid imaging, lipidomics, patient-derived fibroblast analysis, ER export signal characterization\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (enzymatic assay, lipid imaging, lipidomics) in patient-derived cells and engineered cell lines\",\n      \"pmids\": [\"36102623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SMS2 deficiency in knockout mice attenuates LPS-induced lung injury; loss of SMS2 decreased MAP kinase-JNK activation and reduced pulmonary neutrophil influx and inflammation.\",\n      \"method\": \"SMS2 knockout mouse model, LPS-induced lung injury model, cytokine measurement, MAP kinase signaling analysis\",\n      \"journal\": \"American journal of physiology. Lung cellular and molecular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cellular phenotype and signaling pathway readout, single lab\",\n      \"pmids\": [\"21191108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SMS2 deficiency in mouse brain significantly decreases mRNA and protein expression of P-glycoprotein (Pgp/Mdr1) drug transporter, and reduces ezrin and β-actin expression; co-immunoprecipitation showed association between Pgp, ezrin, and β-actin in brain lysate.\",\n      \"method\": \"RT-PCR, western blot, immunohistochemistry, co-immunoprecipitation, SMS2 knockout mouse brain\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — SMS2 KO with multiple readouts and Co-IP showing Pgp/ezrin/β-actin interaction, single lab\",\n      \"pmids\": [\"21554861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Upregulated SMS2 in anti-dsDNA germinal center B cells induces apoptosis by directly activating protein kinase C delta (PKCδ) pro-apoptotic activity, serving as a B cell tolerance checkpoint; pharmacological stimulation of this pathway inhibited lupus pathogenesis in lupus-prone mice.\",\n      \"method\": \"SMS2 overexpression/knockdown in B cells, PKCδ activity assay, SMS2 knockout mice, lupus mouse models (C57BL/6 and NZBWF1)\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function and gain-of-function with defined apoptotic pathway readout (PKCδ activation), in vivo pharmacological validation, single lab\",\n      \"pmids\": [\"34469734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SMS2 deficiency in platelets reduces platelet aggregation, spreading, clot retraction, and in vivo thrombosis; the PLCγ/PI3K/Akt signaling pathway is inhibited in SMS2-/- platelets and in platelets treated with SMS2 inhibitor D609.\",\n      \"method\": \"SMS2 knockout mouse platelets, pharmacological inhibition with D609, platelet aggregation assays, in vivo thrombosis model, signaling pathway analysis\",\n      \"journal\": \"Thrombosis journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with defined functional and signaling pathway phenotype, confirmed with pharmacological inhibitor, single lab\",\n      \"pmids\": [\"33910580\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SMS2 siRNA inhibition suppresses pancreatic tumor growth by modulating tumor-associated macrophage polarization and reducing tumor-associated neutrophil infiltration via regulation of the NF-κB/CXCL5 pathway.\",\n      \"method\": \"Self-assembling SMS2 siRNA in vivo delivery, murine Panc02 pancreatic carcinoma model, immune cell profiling, NF-κB/CXCL5 pathway analysis\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo siRNA knockdown with defined immune and signaling pathway readouts, single lab\",\n      \"pmids\": [\"39255679\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SMS2 inhibition (via inhibitor Ly93) suppresses endothelial-to-mesenchymal transition (EndMT) by blocking the Wnt/β-catenin pathway, which attenuates PPARγ ubiquitination-mediated degradation through PPARγ-β-catenin interaction, ultimately reducing CPT1A expression and fatty acid oxidation; endothelial-specific SMS2 overexpression in ApoE-/- mice enhances atherosclerosis.\",\n      \"method\": \"Pharmacological SMS2 inhibition, RNA sequencing, endothelial cell-specific SMS2 overexpression in ApoE-/- mice, EndMT marker analysis, Wnt/β-catenin and PPARγ pathway assays, human atherosclerotic plaque analysis\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (pharmacological inhibition, in vivo overexpression, RNA-seq, pathway assays) in single lab study\",\n      \"pmids\": [\"41988717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SPNS2 knockdown in endothelial cells upregulates SMS2 expression, leading to increased sphingomyelin synthesis and endothelial-to-mesenchymal transition (EndMT); exogenous sphingomyelinase, which degrades SM, reverses the SPNS2 knockdown-induced EndMT.\",\n      \"method\": \"siRNA knockdown of SPNS2, exogenous SM addition and sphingomyelinase treatment, EndMT marker analysis, sphingolipid metabolic profiling\",\n      \"journal\": \"Cellular and molecular biology (Noisy-le-Grand, France)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, indirect evidence for SMS2 role (via upstream SPNS2 manipulation), no direct SMS2 loss-of-function experiment\",\n      \"pmids\": [\"39910932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Uric acid upregulates SMS2 expression in endothelial cells; SMS2 siRNA knockdown reverses uric acid-induced apoptosis, impaired migration, diminished angiogenic potential, ER stress marker elevation, and intracellular calcium disruption.\",\n      \"method\": \"siRNA knockdown of SMS2 in HUVEC cells, uric acid cytotoxicity assay, ER stress marker analysis, calcium homeostasis measurement, functional assays (migration, angiogenesis)\",\n      \"journal\": \"Toxicology in vitro\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, siRNA knockdown with functional phenotypes but pathway placement remains correlative\",\n      \"pmids\": [\"40865887\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SGMS2 encodes sphingomyelin synthase 2 (SMS2), a plasma membrane-resident bifunctional enzyme that catalyzes transfer of phosphocholine from phosphatidylcholine to ceramide to produce sphingomyelin (SM), and also possesses ceramide phosphoethanolamine (CPE) synthase activity; it maintains the SM/cholesterol gradient along the secretory pathway via an autonomous ER export signal, and its activity regulates ceramide levels, lipid raft integrity, PKCδ-mediated B cell apoptosis, PLCγ/PI3K/Akt platelet signaling, Wnt/β-catenin-dependent endothelial-to-mesenchymal transition, NF-κB/CXCL5-dependent tumor immune microenvironment, and P-glycoprotein expression in the brain, with loss-of-function or ER-retaining gain-of-function variants causing defective bone mineralization and osteoporosis/skeletal dysplasia.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SGMS2 encodes sphingomyelin synthase 2 (SMS2), a plasma membrane-resident enzyme that, together with the Golgi-localized SMS1, constitutes the principal sphingomyelin (SM) synthase activity of the cell, transferring phosphocholine to ceramide so that its depletion lowers SM, drives ceramide accumulation, and arrests cell growth [#0]. Distinct from its paralogs, SMS2 is bifunctional, possessing both SM synthase and ceramide phosphoethanolamine (CPE) synthase activities at the cell surface [#1]. SMS2 carries an autonomous ER export signal that governs its trafficking to the plasma membrane; pathogenic SGMS2 variants either abolish catalytic activity (p.Arg50*) or, while remaining fully active, disrupt this export signal (p.Ile62Ser, p.Met64Arg), causing ER retention, ectopic SM accumulation in the ER, disrupted transbilayer SM asymmetry, and imbalanced cholesterol and glycerophospholipid organization along the secretory pathway, which underlies severe bone mineralization defects and skeletal dysplasia/osteoporosis [#2, #3]. Through its control of membrane sphingolipid composition, SMS2 modulates multiple signaling outputs: it activates pro-apoptotic PKCδ as a germinal-center B-cell tolerance checkpoint [#6], supports PLCγ/PI3K/Akt-dependent platelet activation and thrombosis [#7], drives Wnt/β-catenin-dependent endothelial-to-mesenchymal transition and atherosclerosis [#9], and shapes the tumor immune microenvironment via NF-κB/CXCL5 signaling [#8]. In mice, SMS2 loss attenuates LPS-induced lung injury by dampening JNK MAP-kinase activation [#4] and reduces brain expression of the P-glycoprotein drug transporter [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that SMS2 is a bona fide sphingomyelin synthase whose activity is required for SM homeostasis and cell proliferation, defining its core metabolic role and plasma-membrane localization.\",\n      \"evidence\": \"siRNA depletion of SMS1/SMS2 in HeLa cells with lipid analysis, growth assays, and localization\",\n      \"pmids\": [\"17449912\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve catalytic mechanism or substrate determinants\", \"Growth arrest mechanism (ceramide vs. SM loss) not dissected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Distinguished SMS2 biochemically from its paralogs by showing it is dual-function, producing both SM and CPE, refining the enzymatic identity of the SMS family.\",\n      \"evidence\": \"In vitro enzymatic assays with substrate specificity profiling and surface activity measurement in SMS2-overexpressing HeLa cells\",\n      \"pmids\": [\"19454763\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological significance of CPE synthase activity not established\", \"No structural basis for dual substrate use\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked SGMS2 variants to a skeletal disease and showed two distinct molecular mechanisms — catalytic loss versus ER retention of active enzyme — explaining how both loss- and gain-of-function alleles cause pathology.\",\n      \"evidence\": \"Functional enzymatic assays and localization studies of patient-derived variants\",\n      \"pmids\": [\"30779713\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-level mechanism connecting SM dysregulation to bone mineralization unresolved\", \"ER export signal not yet mapped\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified an autonomous ER export signal in SMS2 and showed that its disruption causes ER SM accumulation and broad secretory-pathway lipid imbalance, providing the membrane-biology mechanism behind the gain-of-function skeletal phenotype.\",\n      \"evidence\": \"Enzymatic assays, fluorescence lipid imaging, lipidomics in patient-derived fibroblasts and engineered cells\",\n      \"pmids\": [\"36102623\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ER lipid imbalance impairs osteoblast/bone function not shown\", \"Trafficking machinery recognizing the export signal unidentified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connected SMS2 activity to expression of the P-glycoprotein drug transporter in brain, implicating sphingomyelin metabolism in transporter regulation.\",\n      \"evidence\": \"RT-PCR, western blot, IHC, and Co-IP in SMS2 knockout mouse brain\",\n      \"pmids\": [\"21554861\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking SM to Pgp/ezrin/actin expression not defined\", \"Single Co-IP without reciprocal validation\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated an inflammatory role for SMS2, where its loss attenuates LPS-induced lung injury via reduced JNK signaling, extending SMS2 function to innate immune signaling.\",\n      \"evidence\": \"SMS2 knockout mouse LPS lung injury model with MAP kinase and neutrophil readouts\",\n      \"pmids\": [\"21191108\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct link between SM/ceramide changes and JNK activation not established\", \"Cell type responsible not isolated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined SMS2 as a B-cell tolerance checkpoint by showing it drives PKCδ-mediated apoptosis of autoreactive germinal-center B cells, with therapeutic relevance in lupus.\",\n      \"evidence\": \"SMS2 gain/loss of function in B cells, PKCδ activity assays, knockout and lupus mouse models\",\n      \"pmids\": [\"34469734\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between SM synthesis and PKCδ activation unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed SMS2 supports platelet activation and thrombosis through the PLCγ/PI3K/Akt pathway, broadening its signaling role to hemostasis.\",\n      \"evidence\": \"SMS2 knockout platelets and D609 inhibition in aggregation and in vivo thrombosis assays\",\n      \"pmids\": [\"33910580\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How membrane SM modulates PLCγ/PI3K/Akt not mechanistically defined\", \"D609 specificity is a confound\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Implicated SMS2 in shaping the tumor immune microenvironment via NF-κB/CXCL5, identifying it as a candidate target in pancreatic cancer.\",\n      \"evidence\": \"In vivo SMS2 siRNA delivery in murine Panc02 model with immune profiling\",\n      \"pmids\": [\"39255679\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct effect of SMS2 on tumor vs. immune cells not separated\", \"NF-κB/CXCL5 link correlative\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed SMS2 upstream of Wnt/β-catenin-driven endothelial-to-mesenchymal transition and atherosclerosis, mechanistically tying it to PPARγ stability and fatty acid oxidation.\",\n      \"evidence\": \"Pharmacological SMS2 inhibition, RNA-seq, endothelial-specific overexpression in ApoE-/- mice, pathway assays, human plaque analysis\",\n      \"pmids\": [\"41988717\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How SM synthesis activates Wnt/β-catenin not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided context that SMS2 acts downstream of SPNS2 and that uric acid stress upregulates SMS2 in endothelial cells, supporting a role in endothelial dysfunction, though through indirect or correlative manipulations.\",\n      \"evidence\": \"siRNA knockdown of SPNS2 or SMS2 in endothelial cells with SM/sphingomyelinase manipulation and functional/ER-stress readouts\",\n      \"pmids\": [\"39910932\", \"40865887\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"SPNS2 study lacks direct SMS2 loss-of-function\", \"Pathway placement remains correlative\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SMS2-controlled changes in plasma-membrane and ER sphingomyelin are mechanistically transduced into the diverse downstream pathways (PKCδ, PLCγ/PI3K/Akt, Wnt/β-catenin, NF-κB) and into bone mineralization remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying mechanism linking membrane lipid changes to specific signaling outputs\", \"Tissue-specific basis of skeletal disease unexplained\", \"No structural model of SMS2\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 7, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}