Affinage

SGMS2

Phosphatidylcholine:ceramide cholinephosphotransferase 2 · UniProt Q8NHU3

Length
365 aa
Mass
42.3 kDa
Annotated
2026-06-10
27 papers in source corpus 12 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

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).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2007 High

    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

    PMID:17449912

    Open questions at the time
    • Did not resolve catalytic mechanism or substrate determinants
    • Growth arrest mechanism (ceramide vs. SM loss) not dissected
  2. 2009 High

    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

    PMID:19454763

    Open questions at the time
    • Physiological significance of CPE synthase activity not established
    • No structural basis for dual substrate use
  3. 2019 High

    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

    PMID:30779713

    Open questions at the time
    • Tissue-level mechanism connecting SM dysregulation to bone mineralization unresolved
    • ER export signal not yet mapped
  4. 2022 High

    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

    PMID:36102623

    Open questions at the time
    • How ER lipid imbalance impairs osteoblast/bone function not shown
    • Trafficking machinery recognizing the export signal unidentified
  5. 2011 Medium

    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

    PMID:21554861

    Open questions at the time
    • Mechanism linking SM to Pgp/ezrin/actin expression not defined
    • Single Co-IP without reciprocal validation
  6. 2010 Medium

    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

    PMID:21191108

    Open questions at the time
    • Direct link between SM/ceramide changes and JNK activation not established
    • Cell type responsible not isolated
  7. 2021 Medium

    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

    PMID:34469734

    Open questions at the time
    • Molecular link between SM synthesis and PKCδ activation unresolved
    • Single lab
  8. 2021 Medium

    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

    PMID:33910580

    Open questions at the time
    • How membrane SM modulates PLCγ/PI3K/Akt not mechanistically defined
    • D609 specificity is a confound
  9. 2024 Medium

    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

    PMID:39255679

    Open questions at the time
    • Direct effect of SMS2 on tumor vs. immune cells not separated
    • NF-κB/CXCL5 link correlative
  10. 2025 Medium

    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

    PMID:41988717

    Open questions at the time
    • How SM synthesis activates Wnt/β-catenin not resolved
    • Single lab
  11. 2025 Low

    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

    PMID:39910932 PMID:40865887

    Open questions at the time
    • SPNS2 study lacks direct SMS2 loss-of-function
    • Pathway placement remains correlative

Open questions

Synthesis pass · forward-looking unresolved questions
  • 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.
  • 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

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016740 transferase activity 4 GO:0016787 hydrolase activity 1
Localization
GO:0005783 endoplasmic reticulum 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-1430728 Metabolism 3 R-HSA-162582 Signal Transduction 3

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 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. RNA interference (siRNA knockdown), lipid analysis, cell growth assays The Journal of biological chemistry High 17449912
2009 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. In vitro enzymatic assay, substrate specificity profiling, overexpression in HeLa cells, surface activity measurement Journal of lipid research High 19454763
2019 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. Functional enzymatic assays of mutant proteins, cellular localization studies, patient-derived variant characterization JCI insight High 30779713
2022 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. Biochemical enzymatic activity assays, fluorescence-based lipid imaging, lipidomics, patient-derived fibroblast analysis, ER export signal characterization eLife High 36102623
2010 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. SMS2 knockout mouse model, LPS-induced lung injury model, cytokine measurement, MAP kinase signaling analysis American journal of physiology. Lung cellular and molecular physiology Medium 21191108
2011 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. RT-PCR, western blot, immunohistochemistry, co-immunoprecipitation, SMS2 knockout mouse brain Biochemical pharmacology Medium 21554861
2021 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. SMS2 overexpression/knockdown in B cells, PKCδ activity assay, SMS2 knockout mice, lupus mouse models (C57BL/6 and NZBWF1) Cell reports Medium 34469734
2021 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. SMS2 knockout mouse platelets, pharmacological inhibition with D609, platelet aggregation assays, in vivo thrombosis model, signaling pathway analysis Thrombosis journal Medium 33910580
2024 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. Self-assembling SMS2 siRNA in vivo delivery, murine Panc02 pancreatic carcinoma model, immune cell profiling, NF-κB/CXCL5 pathway analysis International immunopharmacology Medium 39255679
2025 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. 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 Arteriosclerosis, thrombosis, and vascular biology Medium 41988717
2025 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. siRNA knockdown of SPNS2, exogenous SM addition and sphingomyelinase treatment, EndMT marker analysis, sphingolipid metabolic profiling Cellular and molecular biology (Noisy-le-Grand, France) Low 39910932
2025 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. siRNA knockdown of SMS2 in HUVEC cells, uric acid cytotoxicity assay, ER stress marker analysis, calcium homeostasis measurement, functional assays (migration, angiogenesis) Toxicology in vitro Low 40865887

Source papers

Stage 0 corpus · 27 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 Both sphingomyelin synthases SMS1 and SMS2 are required for sphingomyelin homeostasis and growth in human HeLa cells. The Journal of biological chemistry 189 17449912
2019 Osteoporosis and skeletal dysplasia caused by pathogenic variants in SGMS2. JCI insight 63 30779713
2009 Sphingomyelin synthase SMS2 displays dual activity as ceramide phosphoethanolamine synthase. Journal of lipid research 61 19454763
2010 Sphingomyelin synthase 2 (SMS2) deficiency attenuates LPS-induced lung injury. American journal of physiology. Lung cellular and molecular physiology 45 21191108
2019 The Opposing Contribution of SMS1 and SMS2 to Glioma Progression and Their Value in the Therapeutic Response to 2OHOA. Cancers 31 30646599
2011 The effect of sphingomyelin synthase 2 (SMS2) deficiency on the expression of drug transporters in mouse brain. Biochemical pharmacology 30 21554861
2022 Pathogenic variants of sphingomyelin synthase SMS2 disrupt lipid landscapes in the secretory pathway. eLife 25 36102623
2023 LARP6 suppresses colorectal cancer progression through ZNF267/SGMS2-mediated imbalance of sphingomyelin synthesis. Journal of experimental & clinical cancer research : CR 21 36691044
2018 Isolation of the (+)-Pinoresinol-Mineralizing Pseudomonas sp. Strain SG-MS2 and Elucidation of Its Catabolic Pathway. Applied and environmental microbiology 20 29222099
2020 Musculoskeletal phenotype in two unrelated individuals with a recurrent nonsense variant in SGMS2. Bone 17 32028018
2012 A sensitive cell-based method to screen for selective inhibitors of SMS1 or SMS2 using HPLC and a fluorescent substrate. Chemistry and physics of lipids 15 23063490
2021 Abnormal Bone Tissue Organization and Osteocyte Lacunocanalicular Network in Early-Onset Osteoporosis Due to SGMS2 Mutations. JBMR plus 14 34761145
2021 LncRNA THAP9-AS1 accelerates cell growth of esophageal squamous cell carcinoma through sponging miR-335-5p to regulate SGMS2. Pathology, research and practice 13 34273804
2021 SMS2 deficiency impairs PKCδ-regulated B cell tolerance in the germinal center. Cell reports 13 34469734
2020 Oxidative Catabolism of (+)-Pinoresinol Is Initiated by an Unusual Flavocytochrome Encoded by Translationally Coupled Genes within a Cluster of (+)-Pinoresinol-Coinduced Genes in Pseudomonas sp. Strain SG-MS2. Applied and environmental microbiology 11 32198167
2015 Prenatal alcohol exposure inducing the apoptosis of mossy cells in hippocampus of SMS2-/- mice. Environmental toxicology and pharmacology 11 26562048
2023 SGMS2 in primary osteoporosis with facial nerve palsy. Frontiers in endocrinology 10 37886644
2021 The role of Sphingomyelin synthase 2 (SMS2) in platelet activation and its clinical significance. Thrombosis journal 8 33910580
2024 SMS2 siRNA inhibits pancreatic tumor growth by tumor microenvironment modulation. International immunopharmacology 5 39255679
2023 Clinical and Genetic Characteristics of Calvarial Doughnut Lesions with Bone Fragility in Three Families with a Reccurent SGMS2 Gene Variant. International journal of molecular sciences 5 37175737
2025 A novel SGMS2 mutation associated with high bone mass; description of an affected family with recurrent fragility fractures. Bone reports 4 40123745
2024 SMS2, a Novel Allele of OsINV3, Regulates Grain Size in Rice. Plants (Basel, Switzerland) 4 38732433
2023 Hsa_circ_0000129 knockdown attenuates proliferation and migration in keloid fibroblasts by targeting miR-485-3p/SGMS2 pathway. Burns : journal of the International Society for Burn Injuries 3 37407394
2025 The loss of Spinster homolog 2 drives endothelial mesenchymal transition via SMS2-mediated disruption of sphingomyelin metabolism. Cellular and molecular biology (Noisy-le-Grand, France) 2 39910932
2025 Hyperuricemia impairs endothelial function through SMS2-dependent activation of the endoplasmic reticulum stress response. Toxicology in vitro : an international journal published in association with BIBRA 1 40865887
2025 Transcriptomic and lipidomic profiling provide novel insight into the pathogenesis of monogenic SGMS2-related osteoporosis. JBMR plus 1 40978119
2026 Inhibiting Endothelial SMS2 Alleviates Atherosclerosis by Blocking Endothelial‑Mesenchymal Transition Through Boosted Fatty Acid Oxidation. Arteriosclerosis, thrombosis, and vascular biology 0 41988717

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