Dataset Information

Deconstruction of protein O-glycosylation

ABSTRACT: GalNAc-transferase (GalNAc-T) isoforms modify distinct subsets of the O-glycoproteome and GalNAc-type O-glycosylation is found on most proteins trafficking through the secretory pathway in metazoan cells. The O-glycoproteome is regulated by up to 20 polypeptide GalNAc-Ts and the contributions and biological functions of individual GalNAc-Ts are poorly understood. Here, we used a zinc-finger nuclease (ZFN)-directed knockout strategy to probe the contributions of the major GalNAc-Ts (GalNAc-T1 and T2) in liver cells, and explore how the GalNAc-T repertoire quantitatively affects the O-glycoproteome. We demonstrate that the majority of the O-glycoproteome is covered by redundancy, whereas distinct subsets of substrates are modified by non-redundant functions of GalNAc-T1 and T2. Differential transcriptomic analysis indicates that loss of function of a GalNAc-T induces specific transcriptional response. The non-redundant O-glycoproteome subsets for and the transcriptional responses for each isoform appeared to be related to different cellular processes, and for the GalNAc-T2 isoform supporting a role in lipid metabolism. The results demonstrate that GalNAc-Ts have non-redundant glycosylation functions, and that these may affect distinct cellular processes. The data provides a comprehensive resource for unique substrates for individual GalNAc-Ts. Our study provides a new view on the regulation of the O-glycoproteome, suggesting that the plurality of GalNAc-Ts arose to regulate distinct protein functions and cellular processes.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Sergey Vakhrushev

LAB HEAD: Henrik Clausen

PROVIDER: PXD002770 | Pride | 2015-08-21

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	121120_HepG2_041012_SCL_T1KOM_95_IEF_10_100_4h_5HCD_5ETD.raw	Raw
	121120_HepG2_041012_SCL_T1KOM_95_IEF_11_100_4h_5HCD_5ETD.raw	Raw
	121120_HepG2_041012_SCL_T1KOM_95_IEF_12_100_4h_5HCD_5ETD.raw	Raw
	121120_HepG2_041012_SCL_T1KOM_95_IEF_1_100_2h_5HCD_5ETD.raw	Raw
	121120_HepG2_041012_SCL_T1KOM_95_IEF_2_100_2h_5HCD_5ETD.raw	Raw

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Publications

Deconstruction of O-glycosylation--GalNAc-T isoforms direct distinct subsets of the O-glycoproteome.

Schjoldager Katrine T KT Joshi Hiren J HJ Kong Yun Y Goth Christoffer K CK King Sarah Louise SL Wandall Hans H HH Bennett Eric P EP Vakhrushev Sergey Y SY Clausen Henrik H

EMBO reports 20151113 12

GalNAc-type O-glycosylation is found on most proteins trafficking through the secretory pathway in metazoan cells. The O-glycoproteome is regulated by up to 20 polypeptide GalNAc-Ts and the contributions and biological functions of individual GalNAc-Ts are poorly understood. Here, we used a zinc-finger nuclease (ZFN)-directed knockout strategy to probe the contributions of the major GalNAc-Ts (GalNAc-T1 and GalNAc-T2) in liver cells and explore how the GalNAc-T repertoire quantitatively affects ...[more]

PMID: 26566661

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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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