Deconstruction of O-glycosylation – Polypeptide GalNAc-T Isoforms Direct Distinct Subsets of the O-Glycoproteome
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Illumina Truseq RNA Sample Preparation Kit, Illumina HiSeq 2000
ORGANISM(S): Homo sapiens
SUBMITTER: Hiren Joshi
PROVIDER: E-MTAB-3844 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description: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.
2015-08-21 | PXD002770 | Pride
Project description:The GalNAc-type O-glycoproteome is orchestrated by a large family of polypeptide GalNAc-transferase isoenzymes (GalNAc-Ts) with partially overlapping contributions to the O-glycoproteome as well as distinct non-redundant functions. Increasing evidence indicate that individual GalNAc-Ts co-regulate and fine-tune specific protein functions in health and disease, and deficiencies in individual GALNT genes underlie congenital diseases with distinct phenotypes. Studies of GalNAc-T specificities have mainly been performed with in vitro enzyme assays using short peptide substrate, but recently quantitative differential O-glycoproteomics of isogenic cells with and without GALNT genes has enabled a more unbiased exploration of the non-redundant contributions of individual GalNAc-Ts. Both approaches suggest that fairly small subsets of O-glycosites are non-redundantly regulated by specific GalNAc-Ts, but how these isoenzymes orchestrate regulation amongst competing redundant substrates is unclear. To explore this, we developed isogenic cell model systems with Tet-On inducible expression of two GalNAc-T genes, GALNT2 and GALNT11, in a knockout background. Using quantitative O-glycoproteomics with TMT labelling we found that isoform-specific glycosites were glycosylated in a dose dependent manner, and induction of GalNAc-T2 or T11 produced discrete glycosylation effects without affecting the major part of the glycoproteome. The results support the findings that individual GalNAc-T isoenzymes can serve in fine-tuned regulation of distinct protein functions
2018-10-16 | PXD010155 | Pride
Project description:Most proteins trafficking the secretory pathway of metazoan cells will acquire GalNAc-type O-glycosylation. GalNAc-type O-glycosylation is differentially regulated in cells by the expression of a repertoire of up to twenty genes encoding polypeptide GalNAc-transferase isoforms (GalNAc-Ts) that initiate O-glycosylation by catalyzing the attachment of GalNAc residues to select Ser and Thr residues. These GalNAc-Ts orchestrate the positions and patterns of O-glycans on proteins in poorly understood coordinated ways guided partly by the kinetic properties and substrate specificities of their catalytic domains and modulatory effects of their unique GalNAc-binding lectin domains. Here, we provide the hereto most comprehensive characterization of the non-redundant contributions of individual GalNAc-T isoforms to the O-glycoproteome of the human HEK293 cell line using quantitative differential O-glycoproteomics on a panel of isogenic HEK293 cell lines with knockout of GalNAc-T genes (GALNT1, T2, T3, T7, T10, or T11). We confirm that a major part of the O-glycoproteome is covered by redundancy, while distinct subsets of O-glycosites are covered by non-redundant GalNAc-T isoform-specific functions. We demonstrate that GalNAc-T7 and T10 as predicted from in vitro studies function in completion of high density O-glycosylated regions, while GalNAc-T11 selectively controls the site-specific O-glycosylation of low-density lipoprotein-related receptors in the linker regions between the ligand-binding LDLR class A repeats.
2019-06-24 | PXD009955 | Pride
Project description: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.
2024-05-23 | PXD047845 | Pride
Project description:Glycosylation is an abundant post-translational modification of both intracellular and extracellular proteins [1]. The majority of glycans are classified as N-linked chains, where the carbohydrate moiety is attached to asparagine residues, or O-linked chains, most commonly linked to a serine or threonine. N-linked glycosylation is initiated by the oligosaccharyltransferase complex with only two paralogs of the catalytic subunit, whereas O-glycan initiation is more complex. There are several types of O-linked glycosylation, but among the most diverse is the mucin or GalNAc type (hereafter referred to as O-glycosylation). O-glycosylation is initiated by 20 evolutionarily conserved polypeptide GalNAc-transferases (GalNAc-Ts), which catalyze the first step in the O-glycosylation of proteins by adding GalNAc residues to threonine, serine, and tyrosine amino acids (Fig 1A). Each of the GalNAc-Ts are differentially expressed in various tissues and have both distinct and overlapping peptide substrate specificities [2-12]. Thus, the repertoire of GalNAc-Ts expressed in a given cell determines the subset and O-glycosite pattern of glycosylated proteins [13]. Substantial efforts have been made to characterize and predict the substrate specificities of GalNAc-Ts in vitro, but understanding of the in vivo specificities of the individual GalNAc-Ts or their biological functions is limited [13-15]. This lack of insight prevents an understanding of how site-specific O-linked glycosylation affects diseases, such as metabolic disorders, cardiovascular disease, and various malignancies, that have been associated with GalNAc-Ts through genome-wide association studies and other linkage studies [16-26]. Therefore, it is imperative that we establish how O-glycosylation at specific sites in proteins affects protein function. A major task in achieving this goal is to identify the non-redundant biological functions of site-specific O-glycosylation. We and others recently developed new strategies for identifying specific sites on proteins that undergo O-glycosylation in different cell types and tissues [27-31]. Characterization of the O-glycoproteomic landscape in isolated human cells and multiple human cell lines suggests that more than 80 % of all proteins that traffic through the secretory pathway are O-glycoproteins [28, 30]. Probing the non-redundant contributions of individual GalNAc-Ts in cells with and without specific GalNAc-Ts [32-34] has revealed broad substrate specificities for some of the individual isoforms, whereas others seem to have very restricted substrate specificities [33-35]. Assessing all of the mapped O-glycosylation sites to identify associations between O-glycosites and protein annotations, we recently found that O-glycans are over-represented close to tandem repeat regions, protease cleavage sites, within propeptides, and on a select group of protein domains [28, 30, 36]. Although such general associations between the location of O-glycans and protein functions may direct future investigations, the strategy does not define the function of site-specific glycosylation. Further progress in discovering and defining novel functions of site-specific glycosylation events requires direct quantitative analysis of potential biological responses induced by the loss of distinct GalNAc-T isoforms, and such biological responses are not easily observed in single cell culture systems. Instead, more complex model systems can be used to examine and dissect the molecular mechanisms underlying the important biological functions of site-specific glycosylation. We previously used an organotypic tissue model equipped with genetically engineered cells to decipher the function of elongated O-glycans [29]. In the present study, we use the model combined with quantitative O-glycoproteomics and phosphoproteomics to perform open-ended discovery of the biological functions of site-specific glycosylation governed by GalNAc-Ts (Fig 1B). With this combinatorial strategy, we demonstrate that loss of individual GalNAc-T isoforms has distinct phenotypic consequences through their effect on distinct biological pathways, suggesting specific roles during epithelial formation.
2020-05-22 | PXD016618 | Pride
Project description:Ebola virus glycoprotein is one of the most heavily O-glycosylated viral envelope glycoproteins. The glycoprotein possesses a large mucin-like domain responsible for the cytopathic effect on infected cells, yet its structure or potential role in early entry events is poorly defined. To understand the importance of O-glycans and the individual O-glycosylation sites for viral infectivity, we performed a comprehensive characterization of site-specific glycosylation governed by the three key GalNAc-transferases, GalNAc-T1, -T2, and -T3, initiating O-glycan biosynthesis. Using TMT isobaric labelling we performed quantitative differential O-glycoproteomics on proteins produced in wild type HEK293 cells and cell lines ablated for each of the three GalNAc-Ts, as well as compared it to patterns on wild type virus-like particles. In total we found 38 and 41 O-glycosites on virus like particle-derived and recombinant GP, respectively, with well correlated sites and site-specific structures. Examination of the isoform-specific glycosylation demonstrate selective initiation of a subset of O-glycosites by each enzyme, with GalNAc-T1 having the largest contribution. We next demonstrate that O-linked glycan truncation and perturbed initiation retarded the production of viral particles and decreased infectivity of progeny virus. This work represents a comprehensive site-specific analysis of EBOV GP and sheds light on differential regulation of EBOV GP glycosylation initiated by host GalNAc-Ts. Together with the effect on viral propagation it opens prospective avenues for tailored intervention approaches and means for modulating immunogen O-glycan density.
2024-04-29 | PXD036213 | Pride
Project description:Dr. Clausen's laboratory is interested in the structure, biosynthesis and genetic regulation of glycoconjugates, with a major focus on mucins. This laboratory is studying the glycosylation and secretion process of mucins and biological functions involving mucins. This lab is also interested in receptor modulation mediated by glycosylation or through glycosphingolipids. RNA samples from two human pancreatic cell lines. The relevance of the variable expression levels of isoforms belonging to the polypeptide GalNAc-transferase gene-family is still a puzzle to us. The polypeptide GalNAc-transferase gene family is estimated to contain 24 gene-members all participating in the initiation of mucin-type O-glycosylation. It has become apparent that each of these individual isoforms have different tissue distribution profiles and kinetic capabilities. Mucin-type O-glycosylation is thus controlled, and dependent upon the repetoir of expressed GalNAc-transferases in any given organ and cell type at any given time. We have been trying to contribute to the understanding of the ordered process controlling mucin-type O-glycosylation in both normal and malignant models, and are currently investigating a pancreatic cell line model in the lab. The pancreatic tumor cell line ASPC-1 has been found to possess low metastatic potential in mouse models, in contrast to the pancreatic tumor cell line Suit-T2 possessing high metastatic potential. Immunohistochemical analysis of both cell lines, ASPC-1 and Suit-T2, using our monoclonal antibodies to 7 isoforms has revealed great differences in the expression profile of these 7 isoforms in theses two cell lines, and for instance GalNAc-T3 has been found to be highly expressed in Suit-T2 but completely lacking in ASPC-1. Two cell lines: ASPC-1 and Suit-T2 are analyzed with 3 independent replicate prepared for each cell line.
2010-12-11 | E-GEOD-26011 | biostudies-arrayexpress
Project description:Dr. Clausen's laboratory is interested in the structure, biosynthesis and genetic regulation of glycoconjugates, with a major focus on mucins. This laboratory is studying the glycosylation and secretion process of mucins and biological functions involving mucins. This lab is also interested in receptor modulation mediated by glycosylation or through glycosphingolipids. RNA samples from two human pancreatic cell lines. The relevance of the variable expression levels of isoforms belonging to the polypeptide GalNAc-transferase gene-family is still a puzzle to us. The polypeptide GalNAc-transferase gene family is estimated to contain 24 gene-members all participating in the initiation of mucin-type O-glycosylation. It has become apparent that each of these individual isoforms have different tissue distribution profiles and kinetic capabilities. Mucin-type O-glycosylation is thus controlled, and dependent upon the repetoir of expressed GalNAc-transferases in any given organ and cell type at any given time. We have been trying to contribute to the understanding of the ordered process controlling mucin-type O-glycosylation in both normal and malignant models, and are currently investigating a pancreatic cell line model in the lab. The pancreatic tumor cell line ASPC-1 has been found to possess low metastatic potential in mouse models, in contrast to the pancreatic tumor cell line Suit-T2 possessing high metastatic potential. Immunohistochemical analysis of both cell lines, ASPC-1 and Suit-T2, using our monoclonal antibodies to 7 isoforms has revealed great differences in the expression profile of these 7 isoforms in theses two cell lines, and for instance GalNAc-T3 has been found to be highly expressed in Suit-T2 but completely lacking in ASPC-1.
2010-12-11 | GSE26011 | GEO
Project description:Mucin-type-O-glycosylation on proteins is integrally involved in human health and disease and is coordinated by an enzyme family of 20 N-acetylgalactosaminyltransferases (GalNAc-Ts). Detailed knowledge on the biological effects of site-specific O-glycosylation is limited due to lack of information on specific glycosylation enzyme activities and O-glycosylation site-occupancies. Here we present a systematic analysis of the isoform-specific targets of all GalNAc-Ts expressed within a tissue-forming human skin cell line, and demonstrate biologically significant effects of O-glycan initiation on epithelial formation. We find over 300 unique glycosylation sites across a diverse set of proteins specifically regulated by one of the GalNAc-T isoforms, consistent with their impact on the tissue phenotypes. Notably, we discover a high variability in the O-glycosylation site-occupancy of 70 glycosylated regions of secreted proteins. These findings revisit the relevance of individual O-glycosylation sites in the proteome, and provide an approach to establish which sites drive biological functions.
2022-10-22 | PXD036791 | Pride
Project description:Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy, thus understanding molecular changes associated with EOC progression could lead to the identification of essential therapeutic targets. Glycosylation is a post-translational modification (PTM) that participates in major pathophysiology events, including tumorigenesis. Aberrant mucin-type or O-glycosylation in cancer is frequently attributed to altered expression of different N-acetylgalactosaminyltransferases (GalNAc-Ts). We have previously identified the N-acetylgalactosaminyltransferase 3 (GALNT3) gene as a potential EOC oncogene, possibly implicated in aberrant O-glycosylation in EOC cells. Literature reports are suggestive for genetic and functional redundancy between different GalNAc-Ts, and our previous data were indicative for an induction of the GALNT6 expression upon GALNT3 suppression in EOC cells. Here we show that GALNT3 gene knockout (KO) in the A2780s EOC cells leads to strong GALNT6 upregulation. Moreover, A2780s cell migration, invasion, proliferation and cell cycle analysis were significantly reduced in double GALNT3/T6 gene KO cells compared to single GALNT3 gene KO. Furthermore, MUC1 expression was downregulated in both GALNT3 KO and GALNT3/6 KO, with a more prominent decrease observed in the double KO clone. In vivo studies supported the observed functional redundancy imposed by GALNT6, as animals injected with double GALNT3/T6 KO EOC cell clones displayed a significant increase in survival rates compared to those injected with the control and the GALNT3 KO clones. Collectively our data strongly suggest for possible functional redundancy of the two GalNAc-Ts (GALNT3 and T6) in EOC, with the perspective to use both of these genes as EOC markers and/or therapeutic targets.
2019-05-07 | GSE104861 | GEO