Dataset Information

An unusual dual sugar-binding lectin domain controls the substrate specificity of a mucin-type O-glycosyltransferase

ABSTRACT: N-acetylgalactosaminyl transferases (GalNAc-Ts) initiate mucin-type O-glycosylation, an abundant and complex post-translational modification that regulates host-microbe interactions, tissue development, and metabolism. GalNAc-Ts contain a C-terminal lectin domain consisting of three homologous repeats (, , where and can potentially interact with O-GalNAc on substrates to enhance activity towards a nearby acceptor Thr/Ser. The ubiquitous isoenzyme GalNAc-T1 modulates diverse biological functions, including heart development, immunity, and SARS-CoV-2 infectivity, but its substrates are largely unknown. Here, we show that both and in GalNAc-T1 uniquely orchestrate the O-glycosylation of various glycopeptide substrates. The repeat directs O-glycosylation to acceptor sites C-terminal to an existing GalNAc, while the repeat directs O-glycosylation to N-terminal sites. Additionally, GalNAc-T1 incorporates and binding into various substrate binding modes to cooperatively increase the specificity towards an intermediate acceptor site. Our studies highlight a unique mechanism by which dual lectin repeats expand substrate specificity and inform on identifying the biological substrates affected by disruptions in GalNAc-T1 function.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Weiming Yang

LAB HEAD: Nadine L. Samara

PROVIDER: PXD047845 | Pride | 2024-05-23

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	2023_27_1_abbie_1_A.raw	Raw
	2023_27_1_abbie_1_AB.raw	Raw
	2023_27_1_abbie_1_B.raw	Raw
	2023_27_1_abbie_1_WT1.raw	Raw
	Dataset_1_identification_of_glycosylation_site_in_muc1_peptide_after_treatment.xlsx	Xlsx

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Publications

An unusual dual sugar-binding lectin domain controls the substrate specificity of a mucin-type O-glycosyltransferase.

Collette Abbie M AM Hassan Sergio A SA Schmidt Susan I SI Lara Alexander J AJ Yang Weiming W Samara Nadine L NL

Science advances 20240228 9

N-acetylgalactosaminyl-transferases (GalNAc-Ts) initiate mucin-type O-glycosylation, an abundant and complex posttranslational modification that regulates host-microbe interactions, tissue development, and metabolism. GalNAc-Ts contain a lectin domain consisting of three homologous repeats (α, β, and γ), where α and β can potentially interact with O-GalNAc on substrates to enhance activity toward a nearby acceptor Thr/Ser. The ubiquitous isoenzyme GalNAc-T1 modulates heart development, immunity, ...[more]

PMID: 38416819

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Project description:A large family of GalNAc transferases (GalNAc-Ts) catalyzes the covalent attachment of N-Acetylgalactosamine (GalNAc) to serine and threonine residues on proteins that pass through the secretory pathway in the first committed step of mucin-type O-glycosylation. Abnormalities in the activity of individual GalNAc-Ts can result in congenital disorders of O-glycosylation (CDG) and influence other biological functions. Although ~85% of proteins that pass through the secretory pathway are modified with O-glycans, only 47 O-glycosylation sites (O-glycosites) from 22 mouse glycoproteins and 17 publications are present on UniProt and an O-glycoprotein database (http://www.oglyp.org/). A compilation of all in vivo O-glycosites (the O-glycoproteome) would be an invaluable step in determining the function of proteins decorated with N-Acetylgalactosamine and what role(s), if any, the O-glycans play. While approaches to delineate O-glycosites have been developed for simple, genetically engineered cell lines, there is no universal approach to mapping the O-glycosites of glycoproteins in complex tissue extracts or biological fluids. We have developed chemical and enzymatic conditions that cleave solitary O-glycans while leaving the modified core protein/peptides assayable by mass spectrometry (MS). The methodology permits the mapping of thousands of O-glycosites decorated with Tn or T antigen from tissues or biological fluids. We then integrated an HCD-pd-EThcD MS workflow and software, including MSFragger-Glyco, pGlyco3, and O-Pair, to study the mouse brain, heart, lung, liver, spleen, kidney, colon, muscle, submandibular gland, and whole blood. The integrated approach identified 2154 solitary O-glycosites from 595 glycoproteins. The O-glycosites and glycoproteins displayed consensus motifs and Gene Ontology (GO) terms for O-glycoproteins. Limited overlap of O-glycosites was observed with protein O-GlcNAcylation and phosphorylation sites. Integrating quantitative glycoproteomics and proteomics revealed a tissue-specific regulation of O-glycosites that the differential expression of Galnt isoenzymes in tissues partly contributes to. We next used established quantitative glycoproteomics and proteomics methods to identify site-specific substrates that may contribute to biologically relevant phenotypes when Galnt2 was genetically ablated in a Galnt2-null mouse model, which presents with lipid and metabolic dysregulation. Our findings suggest networks of Galnt2 direct and indirect interactions that may explain the complex metabolic phenotypes. The mouse O-glycoproteome-map and quantitative glycoproteomics/proteomics approach will provide a valuable foundation for revealing the significance of O-glycosylation biology in CDGs and other diseases and conditions.

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