Affinage

Showing DDOST — OST is a alias.

DDOST

Dolichyl-diphosphooligosaccharide--protein glycosyltransferase 48 kDa subunit · UniProt P39656

Length
456 aa
Mass
50.8 kDa
Annotated
2026-06-09
23 papers in source corpus 10 papers cited in narrative 10 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

DDOST encodes OST48, a structurally essential subunit of the endoplasmic reticulum oligosaccharyltransferase (OST) complex that is required for the stable assembly of both STT3A- and STT3B-containing OST complexes; its loss destabilizes these complexes and causes pronounced global hypoglycosylation of N-glycosylation substrates (PMID:22467853). Biallelic loss-of-function mutations in DDOST reduce N-glycosylation in patient fibroblasts and are rescued by wild-type cDNA, establishing DDOST as a causative gene in congenital disorders of glycosylation (PMID:22305527). ER localization of OST48 is achieved primarily through luminal complex formation with ribophorin I, supported by a cytosolic C-terminal di-lysine retrieval signal (PMID:11530934). Beyond its global role, OST48 mediates N-glycosylation of specific substrates with defined functional consequences: it glycosylates MITA/STING to enable MITA oligomerization and antiviral innate immune signaling (PMID:36449507), the secreted matrix cross-linker lysyl oxidase (PMID:37848450), and in cancer cells EGFR and PD-L1, where DDOST loss suppresses downstream AKT/ERK signaling and sensitizes hepatocellular carcinoma to lenvatinib (PMID:41413687). DDOST was originally identified as the AGE-binding protein p60 with cell-surface AGE-binding activity (PMID:8855306), and additional context-specific roles include a physical interaction with the testis-specific phosphatase PPP1CC2 at the nuclear envelope in spermatogenic cells (PMID:23140390) and regulation of its phosphorylation by PNKP linking it to neutrophil extracellular trap formation (PMID:41109654).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 1996 Medium

    Established a surprising dual identity for DDOST, showing the AGE-binding membrane protein p60 is the same protein as the 48-kDa OST subunit and is also displayed at the cell surface.

    Evidence N-terminal sequencing, immunoprecipitation, AGE-binding and blocking-antibody assays in rat liver membranes

    PMID:8855306

    Open questions at the time
    • Functional significance of surface AGE binding not established
    • Single-lab characterization without independent confirmation
    • Relationship between AGE-binding and OST function unaddressed
  2. 2001 Medium

    Resolved how OST48 is retained in the ER, showing localization depends primarily on luminal complex formation with ribophorin I rather than its cytosolic di-lysine motif alone.

    Evidence Site-directed mutagenesis and immunofluorescence co-expression epistasis in COS-1 cells

    PMID:11530934

    Open questions at the time
    • Structural basis of luminal ribophorin I interaction not defined
    • Mechanism of di-lysine retrieval not detailed
  3. 2012 High

    Defined OST48 as structurally essential for OST complex assembly, demonstrating its knockdown destabilizes both STT3A and STT3B complexes and globally impairs N-glycosylation.

    Evidence Subunit-specific siRNA knockdown with OST complex stability and glycosylation readouts in mammalian cells

    PMID:22467853

    Open questions at the time
    • Catalytic versus purely structural contribution not separated
    • No structural model of OST48 within the assembled complex
  4. 2012 High

    Established DDOST as a human disease gene by linking biallelic loss-of-function mutations to a congenital disorder of glycosylation with functional rescue.

    Evidence Whole-exome sequencing with biochemical glycosylation assays and cDNA complementation in patient fibroblasts

    PMID:22305527

    Open questions at the time
    • Genotype-phenotype spectrum limited to few patients
    • Tissue-specific disease mechanism not dissected
  5. 2012 Medium

    Identified a context-specific interaction of DDOST with the testis-specific phosphatase PPP1CC2 and nuclear-envelope localization in spermatogenic cells, hinting at roles beyond ER glycosylation.

    Evidence Tandem affinity purification with reciprocal in vitro sedimentation and immunolocalization in spermatogenic cells

    PMID:23140390

    Open questions at the time
    • Functional consequence of the PPP1CC2 interaction unknown
    • Mechanism of nuclear-envelope localization unexplained
    • Single-lab finding
  6. 2022 High

    Showed DDOST acts on a specific signaling substrate, glycosylating MITA/STING to enable oligomerization and antiviral immune signaling, with in vivo protective effect against HSV encephalitis.

    Evidence Substrate glycosylation-site mutagenesis, DDOST knockdown/overexpression, oligomerization assay and in vivo mouse brain viral infection model

    PMID:36449507

    Open questions at the time
    • Substrate selectivity determinants not defined
    • Whether effect requires full OST complex or DDOST specifically not separated
  7. 2023 Medium

    Extended DDOST substrate range to the secreted matrix enzyme lysyl oxidase and leveraged this to functionally classify pathogenic DDOST variants.

    Evidence Proximity labelling, LOX N-glycosylation functional assay and variant complementation in cells

    PMID:37848450

    Open questions at the time
    • Transient nature of the LOX interaction not structurally characterized
    • Single-lab assay
  8. 2024 Medium

    Linked DDOST to cancer cell survival, showing its knockdown in PDAC cells triggers ER stress, ROS, and apoptosis.

    Evidence siRNA knockdown in two PDAC cell lines with quantitative proteomics, viability, apoptosis and ROS assays

    PMID:39223141

    Open questions at the time
    • Specific glycoprotein substrates driving the phenotype not identified
    • In vivo relevance untested
  9. 2025 Medium

    Connected DDOST-dependent glycosylation to oncogenic receptor signaling and therapy response, showing depletion impairs EGFR and PD-L1 glycosylation and sensitizes HCC to lenvatinib.

    Evidence DDOST knockdown and NGI-1 inhibition in HCC cell lines and xenografts with glycosylation and signaling readouts

    PMID:41413687

    Open questions at the time
    • Direct versus complex-mediated glycosylation of EGFR/PD-L1 not distinguished
    • Clinical translatability untested
  10. 2025 Medium

    Implicated DDOST phosphorylation, controlled by PNKP, in neutrophil extracellular trap formation during atherosclerosis.

    Evidence Co-IP, RIP, dual-luciferase reporter assays and ApoE-/- mouse atherosclerosis model

    PMID:41109654

    Open questions at the time
    • Phosphorylation site(s) on DDOST not mapped
    • Mechanistic link between DDOST phosphorylation and NET machinery indirect
    • Single-lab finding

Open questions

Synthesis pass · forward-looking unresolved questions
  • How DDOST achieves substrate selectivity and whether its non-glycosylation roles (AGE binding, PPP1CC2 interaction, phosphorylation-dependent NET regulation) are mechanistically separable from OST complex function remains open.
  • No structural model of DDOST substrate engagement
  • Moonlighting functions not reconciled with ER glycosylation role

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 4 GO:0016740 transferase activity 2
Localization
GO:0005783 endoplasmic reticulum 3 GO:0005635 nuclear envelope 1 GO:0005886 plasma membrane 1
Pathway
R-HSA-392499 Metabolism of proteins 2 R-HSA-168256 Immune System 1
Partners
LOXPNKPPPP1CC2RPN1STING1
Complex memberships
oligosaccharyltransferase (OST) complex

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1996 The AGE-binding protein p60 isolated from rat liver membranes is identical to OST-48 (DDOST), a 48-kDa subunit of the oligosaccharyltransferase complex. Immunoprecipitated OST-48 from rat rough endoplasmic reticulum fractions exhibited AGE-specific binding, and anti-OST-48 IgG inhibited AGE-BSA binding to cell membranes in a dose-dependent manner. OST-48 is also surface-expressed on mononuclear, endothelial, renal, and neuronal cells. N-terminal protein sequencing, immunoprecipitation, AGE-ligand binding assay, Western blot, immunostaining, flow cytometry Proceedings of the National Academy of Sciences of the United States of America Medium 8855306
2001 ER localisation of OST48 (DDOST) is conferred by two cytosolic C-terminal lysine residues (Lys-3 and Lys-5 from the C-terminus). These lysines act as a retrieval/relocation signal rather than a primary retention signal. Co-expression with ribophorin I quantitatively retained an OST48 surface-escape mutant in the ER, indicating that ER localisation is primarily achieved through complex formation with ribophorin I involving their luminal domains. Site-directed mutagenesis of OST48 cytosolic lysines, immunofluorescence microscopy of COS-1 cells expressing OST48 mutants and hybrid proteins, co-expression epistasis Biological chemistry Medium 11530934
2012 OST48 (DDOST) and DAD1 are required for the stable assembly of both STT3A- and STT3B-containing oligosaccharyltransferase complexes. Knockdown of OST48 destabilises these complexes and causes pronounced global hypoglycosylation of N-glycosylation substrates. siRNA knockdown of OST48/DAD1/KCP2 in mammalian cells, biochemical analysis of OST complex stability, glycosylation efficiency assays Journal of cell science High 22467853
2012 Biallelic loss-of-function mutations in DDOST (a 22 bp deletion and a missense mutation) cause decreased N-glycosylation in patient fibroblasts, and complementation with wild-type DDOST cDNA restores glycosylation, establishing DDOST as a causative gene in congenital disorders of glycosylation (CDG). Whole-exome sequencing, biochemical glycosylation assays (three biomarkers), cDNA complementation in patient fibroblasts American journal of human genetics High 22305527
2012 DDOST (OST48) physically interacts with the testis-specific protein phosphatase isoform PPP1CC2. The interaction was identified by tandem affinity purification and confirmed by reciprocal in vitro sedimentation assay. DDOST localises to the nuclear envelope in dissociated spermatogenic cells. Tandem affinity purification from knock-in mouse embryonic stem cells, reciprocal in vitro sedimentation assay, immunolocalization Biochemistry Medium 23140390
2022 Upon DNA viral infection, MITA/STING undergoes DDOST-mediated N-glycosylation in the ER. Selective mutation of the DDOST-dependent N-glycosylation sites on MITA abolished MITA oligomerization and downstream immune signalling. Increasing Ddost expression in mouse brain enhanced local immune response to HSV-1 and prolonged survival in HSV encephalitis. N-glycosylation site mutagenesis of MITA, DDOST knockdown/overexpression in cells and in vivo mouse brain, MITA oligomerization assay, viral infection model PLoS pathogens High 36449507
2023 OST48 (DDOST) transiently interacts with lysyl oxidase (LOX), a secreted extracellular matrix cross-linking enzyme, and is required for efficient N-glycosylation of LOX. An assay based on LOX N-glycosylation was used to functionally classify DDOST variants, identifying p.S243F and p.E286del as pathogenic loss-of-function variants. Proximity labelling to identify OST48 interaction with LOX, LOX N-glycosylation functional assay, variant complementation testing in cells Scientific reports Medium 37848450
2024 DDOST knockdown in pancreatic ductal adenocarcinoma (PDAC) cells decreased proliferation and cell viability and increased ER stress, ROS formation, and apoptosis. Quantitative mass spectrometry identified 30 differentially expressed proteins/phosphopeptides after DDOST knockdown. siRNA knockdown of DDOST in two PDAC cell lines, quantitative mass spectrometry proteomics, cell viability and apoptosis assays, ROS measurement Scientific reports Medium 39223141
2025 DDOST depletion in HCC cells impaired EGFR N-glycosylation, suppressing downstream AKT, ERK5 and ERK1/2 signalling and sensitising cells to lenvatinib. DDOST depletion also reduced PD-L1 glycosylation. The OST inhibitor NGI-1 phenocopied these effects in vitro and in vivo. DDOST knockdown in HCC cell lines and xenograft models, EGFR and PD-L1 N-glycosylation assays, Western blot for downstream signalling, pharmacological inhibition with NGI-1 Experimental & molecular medicine Medium 41413687
2025 Macrophage-derived exosome miR-146a-5p suppresses PNKP expression, reducing PNKP–DDOST interaction and thereby enhancing DDOST phosphorylation, which activates JAGN1-dependent neutrophil extracellular trap (NET) formation in atherosclerosis. Co-immunoprecipitation, RIP assay, dual-luciferase reporter assay, Western blot, qRT-PCR, ApoE-/- mouse AS model Cellular signalling Medium 41109654

Source papers

Stage 0 corpus · 23 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1996 Molecular identity and cellular distribution of advanced glycation endproduct receptors: relationship of p60 to OST-48 and p90 to 80K-H membrane proteins. Proceedings of the National Academy of Sciences of the United States of America 299 8855306
2012 The oligosaccharyltransferase subunits OST48, DAD1 and KCP2 function as ubiquitous and selective modulators of mammalian N-glycosylation. Journal of cell science 78 22467853
2012 DDOST mutations identified by whole-exome sequencing are implicated in congenital disorders of glycosylation. American journal of human genetics 58 22305527
1997 Genome organization of human 48-kDa oligosaccharyltransferase (DDOST). Genomics 27 9367678
2017 Increased liver AGEs induce hepatic injury mediated through an OST48 pathway. Scientific reports 25 28947796
2022 DDOST Correlated with Malignancies and Immune Microenvironment in Gliomas. Frontiers in immunology 18 35812432
2017 Dietary advanced glycated end-products and medicines influence the expression of SIRT1 and DDOST in peripheral mononuclear cells from long-term type 1 diabetes patients. Diabetes & vascular disease research 15 29027826
2012 Tandem affinity purification in transgenic mouse embryonic stem cells identifies DDOST as a novel PPP1CC2 interacting protein. Biochemistry 13 23140390
2022 MITA oligomerization upon viral infection is dependent on its N-glycosylation mediated by DDOST. PLoS pathogens 11 36449507
2023 LncRNA TSIX aggravates spinal cord injury by regulating the PI3K/AKT pathway via the miR-532-3p/DDOST axis. Journal of biochemical and molecular toxicology 7 37155292
2022 DDOST-CDG: Clinical and molecular characterization of a third patient with a milder and a predominantly movement disorder phenotype. Journal of inherited metabolic disease 7 36214423
2021 The AGE receptor, OST48 drives podocyte foot process effacement and basement membrane expansion (alters structural composition). Endocrinology, diabetes & metabolism 7 34277994
2001 Analysis of structural signals conferring localisation of pig OST48 to the endoplasmic reticulum. Biological chemistry 6 11530934
1995 PCR-mediated cloning and sequencing of the DmOST50 gene, a WBP1/AvOST50/OST48 homologue, from Drosophila melanogaster. Gene 6 7607543
2023 Functional classification of DDOST variants of uncertain clinical significance in congenital disorders of glycosylation. Scientific reports 5 37848450
2021 The second DDOST-CDG patient with lactose intolerance, developmental delay, and situs inversus totalis. Journal of human genetics 5 34462534
2024 Induction of oxidative- and endoplasmic-reticulum-stress dependent apoptosis in pancreatic cancer cell lines by DDOST knockdown. Scientific reports 4 39223141
2019 Globally elevating the AGE clearance receptor, OST48, does not protect against the development of diabetic kidney disease, despite improving insulin secretion. Scientific reports 4 31541173
2025 Macrophage-derived exosome miR-146a-5p modulates PNKP/DDOST/JAGN1 complex to regulate NETs formation in atherosclerosis. Cellular signalling 2 41109654
2024 DDOST is associated with tumor immunosuppressive microenvironment in cervical cancer. Discover oncology 1 38460058
2025 Progress in research on DDOST dysregulation in related diseases. Glycoconjugate journal 0 40601285
2025 DDOST-Congenital Disorder of Glycosylation: Defining the Clinical Spectrum and First Report of a Structural Variant. American journal of medical genetics. Part A 0 41392699
2025 Targeting DDOST improves the efficacy of lenvatinib and immunotherapy in hepatocellular carcinoma. Experimental & molecular medicine 0 41413687

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