Affinage

SLC35A1

CMP-sialic acid transporter · UniProt P78382

Length
337 aa
Mass
36.8 kDa
Annotated
2026-06-10
14 papers in source corpus 11 papers cited in narrative 11 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

SLC35A1 is a Golgi nucleotide-sugar transporter that imports CMP-sialic acid from the cytoplasm to supply the Golgi sialylation machinery for glycoprotein and glycolipid sialylation (PMID:34015330, PMID:40613041). Its substrate range is set by the size of its binding pocket, which is large enough to also accommodate CDP-ribitol; engineering bulky SLC35A4-derived residues into the pocket abolishes sialylation while preserving CDP-ribitol transport and α-dystroglycan ribitol phosphorylation, establishing that SLC35A1 and SLC35A4 redundantly transport CDP-ribitol (PMID:34015330). SLC35A1 physically associates with the α2,3-sialyltransferase ST3Gal4 in the Golgi, and disruption of this transporter–sialyltransferase complex impairs N-glycan sialylation (PMID:36257191). Through its control of sialylation, SLC35A1 governs megakaryocyte maturation and platelet homeostasis—its loss causing thrombocytopenia via defective megakaryocytopoiesis and accelerated clearance of desialylated platelets (PMID:32303557)—and maintains liver sinusoidal endothelial cell identity by restraining VEGFR2 signaling through VEGFR2 sialylation (PMID:38467191). Because SLC35A1-dependent sialylation builds the terminal sialic acid coat of cell-surface glycans, it determines susceptibility to sialic-acid-dependent viruses and masks underlying galactose receptors (PMID:34069698, PMID:36453883). Distinct from its transport activity, the C-terminal cytoplasmic tail of SLC35A1 has a sialylation-independent role in intracellular trafficking and nuclear import of recombinant AAV vectors (PMID:39601564). Disease-causing variants act through several mechanisms: differential impairment of transport and dimer formation (PMID:33396746), reduced protein stability (PMID:40613041), and a sialylation-independent defect in α-dystroglycan O-mannosylation (PMID:25552652).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2014 High

    Asked whether SLC35A1 contributes to glycosylation beyond CMP-sialic acid transport, revealing a sialylation-independent role in α-dystroglycan O-mannosylation.

    Evidence SLC35A1-knockout HAP1 cells with lentiviral WT and p.Q101H complementation, α-DG ligand-binding and sialic acid incorporation assays

    PMID:25552652

    Open questions at the time
    • Molecular basis linking SLC35A1 to O-mannosylation not defined
    • Does not identify the relevant transported substrate for this function
  2. 2021 High

    Defined the structural determinant of substrate choice, showing the binding-pocket size lets SLC35A1 transport CDP-ribitol redundantly with SLC35A4 in addition to CMP-sialic acid.

    Evidence Site-directed mutagenesis of the SLC35A1 binding pocket expressed in KO cells, with sialylation and α-DG ribitol phosphorylation readouts

    PMID:34015330

    Open questions at the time
    • No high-resolution structure of the transporter with either substrate
    • Stoichiometry/antiport coupling not established
  3. 2021 High

    Established the in vivo physiological consequence of SLC35A1-dependent sialylation in hematopoiesis, defining two mechanisms of thrombocytopenia.

    Evidence Megakaryocyte/platelet-specific conditional Slc35a1 knockout mice with bone marrow, platelet count, and liver clearance analysis

    PMID:32303557

    Open questions at the time
    • Specific desialylated platelet glycoproteins driving clearance not enumerated
    • Megakaryocyte maturation block mechanism not resolved at molecular level
  4. 2021 Medium

    Connected SLC35A1 surface-sialylation to viral tropism, showing its loss unmasks the galactose AAV9 receptor.

    Evidence CRISPR/Cas9 KO of SLC35A1 in HEK293T/HeLa with AAV9 transduction and lectin staining

    PMID:34069698

    Open questions at the time
    • Did not separate surface-receptor masking from intracellular trafficking roles
    • Single cell-line context
  5. 2021 Medium

    Characterized how CDG-causing mutations differentially perturb transport and oligomerization while preserving Golgi targeting.

    Evidence Expression of Q101H, T156R, E196K variants in CST-deficient HEK293T cells with glycan MS, lectins, localization and dimer assays

    PMID:33396746

    Open questions at the time
    • Functional significance of dimerization for transport not directly tested
    • Genotype-phenotype correlation in patients not established
  6. 2022 Medium

    Identified a physical transporter–sialyltransferase complex, showing SLC35A1 associates with ST3Gal4 to promote N-glycan sialylation.

    Evidence Co-immunoprecipitation of SLC35A1 with ST3Gal4 and CDG-mutant complementation in SLC35A1-KO cells

    PMID:36257191

    Open questions at the time
    • Single Co-IP without reciprocal or structural validation
    • Whether the interaction is direct or bridged is unknown
  7. 2022 Medium

    Extended the viral-attachment role to coronaviruses, placing SLC35A1-mediated sialylation at the PDCoV adsorption step.

    Evidence Genome-wide CRISPR KO screen in LLC-PK1 cells, viral adsorption assays, and recombinant PDCoV S1 mutagenesis

    PMID:36453883

    Open questions at the time
    • Specific sialylated receptor used by PDCoV not defined
    • Single cell-line system
  8. 2024 High

    Demonstrated an organ-level requirement for SLC35A1 sialylation in maintaining endothelial identity by restraining VEGFR2 signaling.

    Evidence Endothelial-specific Slc35a1 knockout mice with transcriptomics, lipidomics, signaling analysis, and SU5416 pharmacological epistasis rescue

    PMID:38467191

    Open questions at the time
    • Direct demonstration of VEGFR2 sialylation site not provided
    • Whether other endothelial receptors contribute is unresolved
  9. 2024 Medium

    Separated the transport function from a sialylation-independent role of the C-terminal tail in rAAV nuclear import.

    Evidence Genome-wide CRISPR screen with ΔC-tail and T128A mutant cell lines, multi-serotype rAAV transduction and nuclear import assays

    PMID:39601564

    Open questions at the time
    • Mechanism by which the cytoplasmic tail directs vector trafficking unknown
    • Cellular trafficking partners of the C-tail not identified
  10. 2025 Medium

    Showed a disease variant can act through protein destabilization rather than direct transport loss, broadening the mutational mechanisms underlying SLC35A1-related disease.

    Evidence CRISPR KO HEK293 complemented with WT or p.Thr45Ala, CMP-Neu5Ac measurement, N-glycan LC-MS, immunoblot, and patient fibroblast analysis

    PMID:40613041

    Open questions at the time
    • Structural basis of destabilization not defined
    • Downstream metabolic effects only correlative

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the C-terminal tail mediates intracellular trafficking and what molecular partners distinguish SLC35A1's transport-independent roles from its CMP-sialic acid/CDP-ribitol transport function remain unresolved.
  • No structural model of the transporter or its tail
  • Trafficking partners of the cytoplasmic tail unidentified
  • Mechanism of the O-mannosylation contribution undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005215 transporter activity 2 GO:0140104 molecular carrier activity 1
Localization
GO:0005794 Golgi apparatus 2
Pathway
R-HSA-392499 Metabolism of proteins 3
Partners

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2014 SLC35A1 deficiency impairs α-dystroglycan O-mannosylation independently of sialic acid; lentiviral complementation with disease mutation p.Q101H failed to restore O-mannosylation in SLC35A1 knockout cells but partly restored sialylation, demonstrating a role for SLC35A1 in α-DG O-mannosylation distinct from its CMP-sialic acid transport function. SLC35A1-knockout cell model (HAP1), lentiviral complementation with wild-type and p.Q101H mutant, α-DG ligand-binding assay, sialic acid incorporation assay Human molecular genetics High 25552652
2020 CDG-causing mutations Q101H, T156R, and E196K differentially impair SLC35A1 transporter function and dimer formation; all mutants retain correct Golgi localization. Single T156R and E196K mutants partially restore sialylation in CST-deficient HEK293T cells, whereas the compound T156R/E196K combination strongly reduces functionality, and differences in dimer formation capacity were observed among variants. Expression of mutant SLC35A1 variants in CST-deficient HEK293T cells, lectin staining, N- and O-glycan MS analysis, glycolipid analysis, microscopy for Golgi localization, dimer formation assay International journal of molecular sciences Medium 33396746
2021 SLC35A1 transports CDP-ribitol into the Golgi in addition to CMP-sialic acid; the large binding pocket of SLC35A1 accommodates both substrates. Introducing bulky residues from SLC35A4 into the SLC35A1 binding pocket abolished sialylation but retained CDP-ribitol transport and ribitol phosphorylation of α-dystroglycan, demonstrating that binding-pocket size determines substrate specificity and that SLC35A1 and SLC35A4 redundantly transport CDP-ribitol. Site-directed mutagenesis of SLC35A1 binding pocket, expression in SLC35A1 KO cell lines, sialylation assay, ribitol phosphorylation assay of α-dystroglycan The Journal of biological chemistry High 34015330
2021 Megakaryocyte/platelet-specific deletion of Slc35a1 in mice causes thrombocytopenia through two mechanisms: impaired megakaryocyte maturation in bone marrow and accelerated clearance of desialylated platelets by Kupffer cells in the liver. Conditional Slc35a1 knockout mice (Plt Slc35a1−/−), bone marrow megakaryocyte analysis, platelet count, liver histology, lectin staining for desialylation Haematologica High 32303557
2022 SLC35A1 physically associates with the α2,3-sialyltransferase ST3Gal4 in the Golgi; this interaction is disrupted by the CDG-causing E196K mutation (but not T156R), and the E196K mutant is less efficient at restoring N-glycan sialylation in SLC35A1-KO cells, suggesting the transporter–sialyltransferase complex is functionally important for N-glycan sialylation. Co-immunoprecipitation of SLC35A1 with ST3Gal4, expression of CDG mutants (E196K, T156R) in SLC35A1-KO cells, lectin/glycan analysis of N-glycan sialylation Biochemical and biophysical research communications Medium 36257191
2024 Endothelial-specific Slc35a1 deletion in mice causes desialylation of VEGFR2 in liver sinusoidal endothelial cells (LSECs), leading to enhanced VEGFR2 signaling, sinusoidal capillarization, disrupted hepatic zonation, and excessive neonatal lipid deposition; pharmacological inhibition of VEGFR2 with SU5416 rescued lipid deposition and hepatic vasculature, placing SLC35A1-mediated sialylation upstream of VEGFR2 signaling in LSEC identity. Endothelial-specific Slc35a1 knockout mice, immunofluorescence, immunoblot, RNA sequencing, lipidomic profiling, VEGFR2 signaling analysis, SU5416 pharmacological rescue Cellular and molecular gastroenterology and hepatology High 38467191
2021 Knockout of SLC35A1 in HEK293T and HeLa cells eliminates cell-surface sialic acid, thereby unmasking terminal galactose residues and rendering cells permissive to AAV9 transduction, demonstrating that SLC35A1-dependent sialylation masks the galactose-based AAV9 receptor on these cells. CRISPR/Cas9 KO of SLC35A1 in HEK293T and HeLa cells, AAV9 transduction assay, lectin staining for cell-surface sialic acid and galactose Cells Medium 34069698
2024 SLC35A1 KO reduces α2,6-linked sialic acid expression and impairs nuclear import of multiple rAAV serotypes post-internalization; deletion of the C-terminal cytoplasmic tail of SLC35A1 significantly decreases rAAV transduction and vector nuclear import without drastically reducing sialic acid expression, while the T128A mutant reduces sialic acid but still supports rAAV transduction, indicating the C-tail has a sialylation-independent role in rAAV intracellular trafficking. Genome-wide CRISPR/Cas9 KO screen, SLC35A1 KO and domain-deletion/point-mutant (ΔC-tail, T128A) cell lines, rAAV transduction assays across multiple serotypes, flow cytometry for surface sialic acid, nuclear import assay mBio Medium 39601564
2022 SLC35A1 KO in LLC-PK1 cells reduces cell-surface sialic acid and decreases porcine deltacoronavirus (PDCoV) adsorption; trypsin treatment promotes SA-dependent PDCoV entry. The T182 residue in the PDCoV S1 N-terminal domain was identified as a putative SA-binding site, placing SLC35A1-mediated sialylation at the viral attachment step. Genome-wide CRISPR/Cas9 KO screen in LLC-PK1 cells, SLC35A1 KO validation, viral adsorption assay, recombinant PDCoV with S1 domain mutations, trypsin treatment, lectin staining Journal of virology Medium 36453883
2019 Loss of SLC35A1 (the sialic acid transporter) affects cell survival upon VSV infection and modulates the apoptotic response induced by VSV, implicating SLC35A1 in the host apoptotic response to oncolytic virus infection. Focused CRISPR/Cas9 KO library genetic screen for cell survival upon VSV infection, follow-up characterization of SLC35A1 KO cells Scientific reports Low 31320712
2025 The SLC35A1 p.Thr45Ala disease variant does not directly impair CMP-Neu5Ac transport (as restoration of CMP-Neu5Ac levels was achieved in KO cells transfected with the variant), but causes reduced protein stability (~65% residual activity), leading to impaired sialylation of ICAM1, GP130, and TGN46, altered N-glycans, and secondary effects on O-GlcNAcylation, energy, and lipid metabolism. CRISPR/Cas9 SLC35A1 KO HEK293 cells complemented with WT or p.Thr45Ala variant, CMP-Neu5Ac measurement, lectin staining, LC-MS N-glycan analysis, immunoblot, patient fibroblast analysis, GlcNAc supplementation rescue Human mutation Medium 40613041

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2021 Slc35a1 deficiency causes thrombocytopenia due to impaired megakaryocytopoiesis and excessive platelet clearance in the liver. Haematologica 33 32303557
2014 Disease mutations in CMP-sialic acid transporter SLC35A1 result in abnormal α-dystroglycan O-mannosylation, independent from sialic acid. Human molecular genetics 31 25552652
2022 Genome-Wide CRISPR/Cas9 Screen Reveals a Role for SLC35A1 in the Adsorption of Porcine Deltacoronavirus. Journal of virology 30 36453883
2023 Genome-scale CRISPR screen identifies TRIM2 and SLC35A1 associated with porcine epidemic diarrhoea virus infection. International journal of biological macromolecules 22 37499712
2019 The transporters SLC35A1 and SLC30A1 play opposite roles in cell survival upon VSV virus infection. Scientific reports 20 31320712
2021 The promiscuous binding pocket of SLC35A1 ensures redundant transport of CDP-ribitol to the Golgi. The Journal of biological chemistry 19 34015330
2020 Novel Insights into Selected Disease-Causing Mutations within the SLC35A1 Gene Encoding the CMP-Sialic Acid Transporter. International journal of molecular sciences 19 33396746
2021 Knockout of the CMP-Sialic Acid Transporter SLC35A1 in Human Cell Lines Increases Transduction Efficiency of Adeno-Associated Virus 9: Implications for Gene Therapy Potency Assays. Cells 16 34069698
2024 Endothelial Slc35a1 Deficiency Causes Loss of LSEC Identity and Exacerbates Neonatal Lipid Deposition in the Liver in Mice. Cellular and molecular gastroenterology and hepatology 10 38467191
2022 An interaction between SLC35A1 and ST3Gal4 is differentially affected by CDG-causing mutations in the SLC35A1 gene. Biochemical and biophysical research communications 8 36257191
2024 Identification of SLC35A1 as an essential host factor for the transduction of multi-serotype recombinant adeno-associated virus (AAV) vectors. mBio 5 39601564
2025 A Novel Missense Variant in Ultrarare SLC35A1-CDG Alters Cellular Glycosylation, Lipid, and Energy Metabolism Without Affecting CDG Serum Markers. Human mutation 1 40613041
2026 Strain-specific responses of avian influenza virus to disruption of solute carrier family 35 member A1 (SLC35A1) in chicken cells. Poultry science 0 42241751
2024 Identification of SLC35A1 as an essential host factor for the transduction of multi-serotype recombinant adeno-associated virus (AAV) vectors. bioRxiv : the preprint server for biology 0 39463973

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