Affinage

SLC35A3

UDP-N-acetylglucosamine transporter · UniProt Q9Y2D2

Length
325 aa
Mass
36.0 kDa
Annotated
2026-06-10
14 papers in source corpus 10 papers cited in narrative 10 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SLC35A3 is a Golgi-resident UDP-N-acetylglucosamine (UDP-GlcNAc) transporter that supplies the activated sugar donor required for GlcNAc-branched glycan biosynthesis (PMID:16344554). It operates as a UDP-GlcNAc/UMP antiporter, with conserved Glu-47 and Lys-50 residues in a TMH2 EXXK motif lining the central translocation cavity being critical for transport kinetics (PMID:31118275). Functionally, SLC35A3 channels imported UDP-GlcNAc to specific Golgi glycosyltransferases: it physically associates with the Mgat (GnT) family of mannoside acetylglucosaminyltransferases and with the UDP-galactose transporter SLC35A2, forming multienzyme complexes in the Golgi membrane (PMID:25944901). Loss of SLC35A3 selectively depletes highly branched tri- and tetraantennary N-glycans while sparing mono- and biantennary species, defining a dedicated role in N-glycan branching downstream of GnT-IV (PMID:24031089, PMID:23766508, PMID:34981577). This activity is regulated post-translationally by OGT, which O-GlcNAcylates SLC35A3 to stabilize the protein and sustain an OGT–SLC35A3–GnT-IV axis for branched-glycan output (PMID:34981577). SLC35A3 is not the sole UDP-GlcNAc transporter and acts cooperatively with SLC35A2, such that balanced function of both transporters is required for normal glycosylation (PMID:32938718, PMID:37552213). Loss-of-function impairs both N-glycan branching and glycosaminoglycan biosynthesis in vivo; a missense mutation causes complex vertebral malformation (CVM) in cattle, and Slc35a3-knockout mice are perinatally lethal with chondrodysplasia and CVM-like vertebral anomalies (PMID:16344554, PMID:37053259).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2005 High

    Established the molecular identity and disease relevance of SLC35A3 by showing it is a functional Golgi UDP-GlcNAc transporter whose mutation causes a defined glycosylation disorder.

    Evidence Yeast complementation rescue of a UDP-GlcNAc transport-deficient strain, tissue glycoproteome analysis, and genetic cosegregation of a CVM-causing missense mutation in cattle

    PMID:16344554

    Open questions at the time
    • Did not resolve the transport mechanism (antiport vs uniport) or the residues mediating substrate translocation
    • Did not define which glycosyltransferases use the transported substrate
  2. 2013 High

    Tied SLC35A3 transport activity directly to a specific glycan output, showing its loss selectively collapses highly branched N-glycans in disease-relevant human cells.

    Evidence Golgi vesicle UDP-GlcNAc transport assay in patient fibroblasts plus cell-surface N-glycan profiling; siRNA knockdown across CHO, HeLa, and MDCK-II cells with glycan analysis and PLA showing SLC35A3–Mgat5 Golgi proximity

    PMID:23766508 PMID:24031089

    Open questions at the time
    • Did not establish whether SLC35A3 is the exclusive UDP-GlcNAc transporter
    • Proximity to Mgat5 did not define a stable biochemical complex or stoichiometry
  3. 2015 High

    Defined SLC35A3 as a hub organizing nucleotide-sugar supply with biosynthetic enzymes by demonstrating endogenous complexes with multiple Mgat enzymes and with the UDP-galactose transporter SLC35A2.

    Evidence In situ PLA at endogenous protein levels and FLIM-FRET detecting Mgat1/2/4B/5 and SLC35A2 interactions

    PMID:25944901

    Open questions at the time
    • Did not determine complex architecture or which interactions are functionally required for transport-to-glycosylation coupling
    • Single laboratory
  4. 2019 High

    Resolved the transport mechanism and its molecular determinants, identifying SLC35A3 as a UDP-GlcNAc/UMP antiporter dependent on conserved TMH2 residues.

    Evidence Cysteine-scanning mutagenesis, reconstitution of variants into proteoliposomes with direct transport kinetics, yeast complementation, and 3D homology modeling placing Glu-47/Lys-50 in the central cavity

    PMID:31118275

    Open questions at the time
    • Homology model not validated by experimental structure
    • Conformational cycle of antiport not directly visualized
  5. 2020 High

    Revised the simple single-transporter model by showing SLC35A3 loss does not abolish Golgi UDP-GlcNAc transport and that branching defects depend on cooperation with SLC35A2.

    Evidence CRISPR/siRNA knockout panels in CHO, HEK293T, and HepG2 cells with Golgi transport assays and N-/O-glycan mass spectrometry, including SLC35A2/SLC35A3 double knockouts

    PMID:32938718

    Open questions at the time
    • Identity of the redundant UDP-GlcNAc transporter(s) not determined
    • Cell-type-specific differences between CHO and HEK293T phenotypes unexplained
  6. 2021 Medium

    Extended the SLC35A3 interactome toward ion-homeostasis machinery, hinting at coupling between nucleotide-sugar transport and Golgi/ER ion regulation.

    Evidence Co-immunoprecipitation with mass spectrometry across four experiments and NanoBiT split-luciferase validation of selected partners (ATP2A2, ATP2C1, GPR89B, TMCO1, BSG)

    PMID:34242836

    Open questions at the time
    • Functional consequence of ion-channel interactions on transport activity not demonstrated
    • Validation limited to a subset of MS candidates
    • Single lab
  7. 2022 High

    Identified post-translational control of SLC35A3 and refined its enzyme partnership, establishing an OGT–SLC35A3–GnT-IV axis driving branched N-glycan synthesis.

    Evidence Chemoenzymatic O-GlcNAcylation labeling and Western blot, co-IP of SLC35A3 with GnT-IV (but not GnT-V), lectin blotting, HPLC and MS glycan profiling, and OGT knockdown phenocopy in SLC35A3-KO cells

    PMID:34981577

    Open questions at the time
    • O-GlcNAcylation site(s) on SLC35A3 not mapped
    • Apparent discrepancy with earlier PLA-detected Mgat5 proximity not reconciled
  8. 2023 High

    Demonstrated the in vivo physiological requirement for SLC35A3, linking its loss to skeletal glycosaminoglycan deficits and recapitulating the bovine CVM phenotype in mouse.

    Evidence CRISPR/Cas9 Slc35a3-knockout mice with histology of growth-plate cartilage, GAG disaccharide composition analysis, and in situ hybridization; chimeric SLC35A2–SLC35A3 hybrid rescue in double-knockout HEK293T cells

    PMID:37053259 PMID:37552213

    Open questions at the time
    • Mechanism linking GAG reduction to cartilage extracellular-space collapse not resolved
    • How balanced SLC35A2/SLC35A3 stoichiometry is normally maintained in vivo unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • The identity of the redundant UDP-GlcNAc transporter(s) compensating for SLC35A3 loss, and the experimental structure underlying its antiport cycle, remain unresolved.
  • No experimentally determined structure of SLC35A3
  • Redundant transporter not molecularly identified
  • How transporter-glycosyltransferase complexes are spatially assembled in the Golgi is undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005215 transporter activity 4 GO:0140104 molecular carrier activity 1
Localization
GO:0005794 Golgi apparatus 3
Pathway
R-HSA-392499 Metabolism of proteins 4 R-HSA-382551 Transport of small molecules 3
Partners
ATP2A2BSGMGAT1MGAT2MGAT4BMGAT5OGTSLC35A2

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2005 SLC35A3 encodes a Golgi-resident UDP-N-acetylglucosamine (UDP-GlcNAc) transporter; a missense mutation causing CVM in cattle impairs this transport activity, as demonstrated by failure of the mutant gene (but not wild-type) to rescue a yeast mutant deficient in Golgi UDP-GlcNAc transport, and by abnormal protein glycosylation in affected tissues. Yeast complementation assay (phenotypic rescue of UDP-GlcNAc transport-deficient yeast strain), proteome analysis of glycosylation patterns in affected tissues, genetic cosegregation Genome research High 16344554
2013 Loss of SLC35A3 function in patient fibroblasts significantly reduces UDP-GlcNAc transport in Golgi vesicles, causing a massive decrease in highly branched N-glycans (tri- and tetraantennary) at the cell surface and a concomitant increase in lower-branched glycoforms. Golgi vesicle UDP-GlcNAc transport assay from patient fibroblasts, glycan analysis of cell surface N-glycans Journal of medical genetics High 24031089
2013 siRNA-mediated knockdown of SLC35A3 in CHO, CHO-Lec8, and HeLa cells decreases highly branched tri- and tetraantennary N-glycans while monoantennary and biantennary glycans remain unchanged or accumulate; knockdown in MDCK-II cells dramatically reduces keratan sulfate but not heparan sulfate biosynthesis. SLC35A3 was also shown by proximity assay to be in close proximity to Mgat5 in the Golgi membrane. siRNA knockdown, glycan analysis, in situ proximity ligation assay (PLA) for SLC35A3–Mgat5 proximity The Journal of biological chemistry High 23766508
2015 SLC35A3 (NGT) forms complexes with mannoside acetylglucosaminyltransferases Mgat1, Mgat2, Mgat4B, and Mgat5 in the Golgi membrane, and interacts with SLC35A2 (UGT) to form heterologous complexes; these interactions were detected at endogenous protein levels. In situ proximity ligation assay (PLA) at endogenous levels, FLIM-FRET The Journal of biological chemistry High 25944901
2019 Conserved Glu-47 and Lys-50 residues in transmembrane helix 2 (TMH2) are critical for the UDP-GlcNAc/UMP antiport activity of mouse Slc35a3; conservative and non-conservative substitutions at these positions impair UDP-GlcNAc uptake and dramatically alter kinetic parameters when reconstituted into proteoliposomes. The EXXK motif in TMH2 is highly conserved across SLC35A subfamily members, and a 3D-homology model places these residues facing the central cavity. Cysteine-scanning mutagenesis, reconstitution of variants into proteoliposomes with direct transport assay, yeast complementation, GFP-tagged protein expression, 3D homology modeling The Journal of biological chemistry High 31118275
2020 Knockout of SLC35A3 in CHO cells impairs N-glycan branching without abolishing UDP-GlcNAc transport into Golgi vesicles; in HEK293T SLC35A3-KO cells, UDP-GlcNAc transport is significantly reduced but N-glycan branching is not impaired; effects on N-glycan branching are potentiated in SLC35A2/SLC35A3 double knockouts. GlcNAc incorporation into O-glycans is not abolished by SLC35A3 loss alone. These data indicate SLC35A3 may not be the sole or primary UDP-GlcNAc transporter. CRISPR/siRNA knockout cell panels (CHO, HEK293T, HepG2), Golgi vesicle UDP-GlcNAc transport assay, N- and O-glycan mass spectrometry analysis The Journal of biological chemistry High 32938718
2021 SLC35A3 interacts with ATP2A2 (SERCA2), ATP2C1, Golgi pH regulator B (GPR89B), calcium channel TMCO1, and basigin (BSG), suggesting links between nucleotide sugar transport and ion homeostasis; interactions confirmed by pull-down/MS and NanoBiT split-luciferase complementation assay. Co-immunoprecipitation pull-down with mass spectrometry (4 independent experiments), NanoBiT split-luciferase complementation assay for selected interactions Journal of proteomics Medium 34242836
2022 OGT modifies SLC35A3 via O-GlcNAcylation, which contributes to SLC35A3 protein stability; SLC35A3 interacts physically with GnT-IV (N-acetylglucosaminyltransferase IV) but not with GnT-V (Mgat5), and SLC35A3 deficiency specifically decreases tri- and tetraantennary N-glycans catalyzed by GnT-IV. OGT knockdown phenocopies SLC35A3 loss, establishing an OGT–SLC35A3–GnT-IV regulatory axis for GlcNAc-branched N-glycan biosynthesis. Co-immunoprecipitation (SLC35A3–GnT-IV interaction), Western blot and chemoenzymatic labeling assay (O-GlcNAcylation of SLC35A3 by OGT), lectin blotting, HPLC, mass spectrometry (N-glycan analysis), SLC35A3 knockout cells FASEB journal High 34981577
2023 Slc35a3-knockout mice generated by CRISPR/Cas9 are perinatal lethal and exhibit chondrodysplasia with CVM-like vertebral anomalies; Slc35a3-/- embryos show drastically reduced extracellular space in growth plate cartilage with reshaped chondrocytes but no change in chondrocyte proliferation, apoptosis, or differentiation. Amounts of heparan sulfate, keratan sulfate, and chondroitin sulfate/dermatan sulfate are significantly decreased in spine and limbs, indicating SLC35A3 regulates glycosaminoglycan biosynthesis in vivo. CRISPR/Cas9 knockout mouse, histological analysis of growth plate cartilage, disaccharide composition analysis of glycosaminoglycans, in situ hybridization for expression pattern PloS one High 37053259
2023 SLC35A2–SLC35A3 and SLC35A3–SLC35A2 hybrid proteins expressed in SLC35A2/SLC35A3 double-knockout HEK293T cells fully restore glycosylation, whereas SLC35A3 alone only partially restores galactosylation, demonstrating that proper glycosylation requires balanced cooperation between SLC35A2 and SLC35A3 in the Golgi membrane. Expression of chimeric hybrid proteins in double-knockout HEK293T cells, glycosylation analysis FEBS letters Medium 37552213

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 A missense mutation in the bovine SLC35A3 gene, encoding a UDP-N-acetylglucosamine transporter, causes complex vertebral malformation. Genome research 125 16344554
2013 Mutations in SLC35A3 cause autism spectrum disorder, epilepsy and arthrogryposis. Journal of medical genetics 49 24031089
2013 UDP-N-acetylglucosamine transporter (SLC35A3) regulates biosynthesis of highly branched N-glycans and keratan sulfate. The Journal of biological chemistry 47 23766508
2015 UDP-galactose (SLC35A2) and UDP-N-acetylglucosamine (SLC35A3) Transporters Form Glycosylation-related Complexes with Mannoside Acetylglucosaminyltransferases (Mgats). The Journal of biological chemistry 46 25944901
2020 Biosynthesis of GlcNAc-rich N- and O-glycans in the Golgi apparatus does not require the nucleotide sugar transporter SLC35A3. The Journal of biological chemistry 23 32938718
2017 A human case of SLC35A3-related skeletal dysplasia. American journal of medical genetics. Part A 19 28777481
2017 Recessive mutations in SLC35A3 cause early onset epileptic encephalopathy with skeletal defects. American journal of medical genetics. Part A 18 28328131
2021 Identification of novel potential interaction partners of UDP-galactose (SLC35A2), UDP-N-acetylglucosamine (SLC35A3) and an orphan (SLC35A4) nucleotide sugar transporters. Journal of proteomics 13 34242836
2022 O-GlcNAcylation regulates β1,4-GlcNAc-branched N-glycan biosynthesis via the OGT/SLC35A3/GnT-IV axis. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 11 34981577
2019 Conserved Glu-47 and Lys-50 residues are critical for UDP-N-acetylglucosamine/UMP antiport activity of the mouse Golgi-associated transporter Slc35a3. The Journal of biological chemistry 8 31118275
2023 Mice lacking nucleotide sugar transporter SLC35A3 exhibit lethal chondrodysplasia with vertebral anomalies and impaired glycosaminoglycan biosynthesis. PloS one 5 37053259
2021 Identification of HIF-dependent alternative splicing in gastrointestinal cancers and characterization of a long, coding isoform of SLC35A3. Genomics 5 33418078
2023 The glycosylation defect in solute carrier SLC35A2/SLC35A3 double knockout cells is rescued by SLC35A2-SLC35A3 and SLC35A3-SLC35A2 hybrids. FEBS letters 4 37552213
2023 Association of genotypes at rs438228855 in bovine SLC35A3 receptor gene of Pakistani cattle with the susceptibility to develop complex vertebral malformation. Reproduction in domestic animals = Zuchthygiene 0 36932867

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