C1GALT1 Human
Description
Molecular Structure and Function
C1GALT1 encodes T-synthase, a Golgi-resident enzyme requiring the chaperone Cosmc (C1GALT1C1) for proper folding and activity . Key features include:
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Catalytic Activity: Transfers galactose from UDP-Gal to Tn antigen (GalNAcα1-Ser/Thr) to form the core 1 structure .
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Protein Partners: Forms a stable complex with Cosmc, which ensures enzymatic activity .
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Gene Interactions: Collaborates with glycosyltransferases like GCNT1 and ST6GALNAC1 to extend O-glycans .
Angiogenesis
C1GALT1 regulates endothelial cell interactions via O-glycosylation of adhesion molecules (e.g., integrins), influencing vascular development .
Platelet Production
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Mice with bone marrow-specific C1GALT1 deletion exhibit severe thrombocytopenia, giant platelets, and prolonged bleeding .
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Reduced T-synthase activity (<5% of wild-type) disrupts megakaryocyte maturation .
Kidney Homeostasis
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C1GALT1 mutations in mice cause glomerular atrophy, tubular stenosis, and fatal renal failure .
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Dysregulation correlates with elevated Gd-IgA1 levels in IgA nephropathy (IgAN) patients .
Cancer
C1GALT1 exhibits dual roles (pro-tumorigenic and suppressive) depending on cancer type:
Inflammatory Diseases
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IgA Nephropathy: Downregulation in B lymphocytes increases pathogenic Gd-IgA1 levels (8.55–14.48 U/ml in patients vs. 3.97–12.15 U/ml in controls) .
O-Glycan Regulation
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Core 1 vs. Core 3 Synthesis: C1GALT1 competes with β3GnT6 (core 3 synthase); reduced activity shifts glycans toward tumor-associated Tn/STn antigens .
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Integrin Signaling: In PDAC, C1GALT1 modifies integrin αv O-glycans, activating FAK/Akt pathways to drive metastasis .
Therapeutic Targets
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COSMC Chaperone: Mutations in COSMC disrupt C1GALT1 folding, leading to Tn antigen accumulation .
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Antibody Therapies: Anti-Tn/STn antibodies show promise in targeting C1GALT1-deficient cancers .
Research Gaps and Future Directions
Product Specs
Q&A
Basic Research Questions
What is the core biochemical function of C1GALT1, and how does it influence cellular processes?
C1GALT1 (core 1 synthase, glycoprotein-N-acetylgalactosamine 3-β-galactosyltransferase 1) catalyzes the synthesis of the core 1 O-glycan structure (T antigen) by transferring galactose from UDP-galactose to Tn antigen (GalNAc-α-1-O-Ser/Thr) . This step is critical for generating extended mucin-type O-glycans on cell surface and secreted glycoproteins. Methodologically, its activity is studied via:
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Enzyme assays: Measuring galactose transfer using radiolabeled UDP-galactose or fluorescent substrates.
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Structural studies: X-ray crystallography of C1GALT1 in complex with substrates (e.g., glycopeptides) reveals its GT-A fold dimer architecture and substrate-binding mechanisms .
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Genetic models: Knockout mice (T-syn−/−) exhibit embryonic lethality due to defective angiogenesis and kidney development .
Which human diseases are directly linked to dysregulated C1GALT1 activity?
C1GALT1 dysfunction is implicated in:
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Cancer: Overexpression in gastric (GC) and pancreatic cancers promotes metastasis via aberrant O-glycosylation of integrins and other oncoproteins .
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IgA nephropathy (IgAN): Reduced C1GALT1 in B lymphocytes elevates galactose-deficient IgA1 (Gd-IgA1), triggering immune complex deposition in kidneys .
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Thrombocytopenia and renal defects: Mouse models (plt1/plt1) with C1GALT1 mutations show 40% platelet reduction and glomerular atrophy .
Experimental validation:
Advanced Research Questions
How can researchers resolve contradictions in C1GALT1’s role as tumor-promoting vs. tumor-suppressing?
Data conflicts arise in cancer contexts:
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Pro-tumor role: In GC, C1GALT1 overexpression enhances integrin α5 O-glycosylation, driving proliferation and invasion .
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Anti-tumor role: In endometrial cancer (EC), C1GALT1 depletion mimics aggressive phenotypes (↑ migration, angiogenesis) .
Methodological strategies:
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Tissue-specific models: Use conditional knockout mice or organoid systems to isolate microenvironmental effects.
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Multi-omics integration: Combine glycomics (lectin arrays) with proteomics (SILAC) to map O-glycoproteome changes .
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Kinetic studies: Compare enzyme activity in primary vs. metastatic tumors using FRET-based substrates.
What experimental designs are optimal for studying C1GALT1’s regulation by transcription factors?
The SP1 transcription factor upregulates C1GALT1 in GC via promoter binding . Key approaches include:
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ChIP-seq: Validate SP1 binding to the C1GALT1 promoter in GC cell lines (e.g., MGC-803).
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Luciferase reporters: Test promoter activity under SP1 overexpression/knockdown.
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Clinical correlation: Match TCGA data (C1GALT1 mRNA vs. SP1 expression) with IHC in patient cohorts.
How do researchers address technical challenges in quantifying C1GALT1 activity in vivo?
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Fluorogenic probes: Develop synthetic glycopeptide substrates with quenched fluorescent tags (e.g., Mca-peptide-Dnp).
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Metabolic labeling: Use azido-GalNAc analogs to track O-glycan elongation via click chemistry.
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Non-invasive imaging: Engineer PET tracers targeting T antigen (e.g., ¹⁸F-labeled anti-T antibodies).
Data Interpretation and Contradictions
Why do C1GALT1 knockout phenotypes vary across tissue types?
Discrepancies arise from:
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Compensatory pathways: Core 3 synthase (β3GnT6) may bypass C1GALT1 in some epithelia .
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Substrate specificity: C1GALT1 glycosylates ~30% of mucins; remaining glycans rely on other GTs .
Critical data:
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In plt1 mice, residual T-synthase activity (5% of WT) partially rescues platelet production but not renal defects .
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Pancreatic C1GALT1−/− cells show ↑ Tn antigen but no core 3 compensation, driving metastasis .
How should researchers validate C1GALT1’s role in IgA nephropathy given low plasma cell yields?
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Single-cell RNA-seq: Profile C1GALT1 expression in circulating IgA1+ plasmablasts from IgAN patients.
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Ex vivo models: Differentiate patient-derived B cells into IgA1-secreting cells under TGF-β/IL-6 stimulation.
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Biomarker correlation: Link serum Gd-IgA1 levels (ELISA) to C1GALT1 polymorphisms (GWAS).
Methodological Innovations
What emerging technologies enhance C1GALT1 structural and functional analysis?
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Cryo-EM: Resolve full-length C1GALT1-Cosmc chaperone complexes in lipid bilayers.
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Glyco-CRISPR: Edit O-glycosylation sites (e.g., Thr/Ser→Ala) in endogenous glycoproteins like integrin α5.
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Machine learning: Predict C1GALT1 substrates using AlphaFold2-predicted glycoprotein structures.
How can multi-omics datasets resolve C1GALT1’s pleiotropic effects?
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Proteomics: SILAC-based quantification in C1GALT1-depleted EC cells identified ANXA1 and LGALS3 as mediators of metastasis .
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Glycomics: PGC-LC-MS/MS quantifies core 1 vs. core 3 O-glycans in CRISPR-edited cell lines.
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Transcriptomics: SCENIC analysis reveals SP1 as the master regulator of C1GALT1 in GC .
Experimental Design Considerations
What controls are essential for C1GALT1 loss-of-function studies?
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Cosmc knockout: Confirm phenotypes are C1GALT1-specific, not chaperone-related.
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Glycan validation: Use Vicia villosa lectin (VVL) to detect Tn antigen in C1GALT1−/− cells .
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Rescue experiments: Re-express WT vs. catalytically dead C1GALT1 (D316N mutant) .
How to model C1GALT1’s role in angiogenesis and thrombosis?
Product Science Overview
Core 1 Beta3-Gal-T1, also known as C1GALT1, is an enzyme that plays a crucial role in the biosynthesis of O-glycans. It is responsible for creating the common core 1 O-glycan structure, Gal-beta-1-3GalNAc-R, by transferring galactose (Gal) from UDP-Gal to N-acetylgalactosamine (GalNAc)-alpha-1-R . This structure is a precursor for many extended mucin-type O-glycans found on cell surfaces and secreted glycoproteins .
The human recombinant form of C1GALT1 is produced in Escherichia coli (E. coli). It is a single, non-glycosylated polypeptide chain containing 357 amino acids (30-363 a.a) and has a molecular mass of approximately 41.4 kDa . The recombinant protein is fused to a 23 amino acid His-tag at the N-terminus, which aids in its purification through chromatographic techniques .
The recombinant form of C1GALT1 is used extensively in research to study its role in glycosylation and its impact on various biological processes. It is also utilized in the development of therapeutic interventions targeting glycosylation pathways.
The C1GALT1 protein solution is typically formulated in a buffer containing 20mM Tris-HCl (pH 8.0), 0.15M NaCl, 20% glycerol, and 1mM DTT . For short-term storage, it can be kept at 4°C if used within 2-4 weeks. For long-term storage, it is recommended to store the protein at -20°C with the addition of a carrier protein (0.1% HSA or BSA) to prevent multiple freeze-thaw cycles .
