Changes in the profile of simple mucin-type O-glycans and polypeptide GalNAc-transferases in human testis and testicular neoplasms are associated with germ cell maturation and tumour differentiation

Meyts, Ewa Rajpert‐De; Poll, S. N.; Goukasian, I.; Jeanneau, Charlotte; Herlihy, Amy; Bennett, Eric; Skakkebæk, Niels E.; Clausen, Henrik; Giwercman, Aleksander; Mandel, Ulla

doi:10.1007/s00428-007-0478-4

Cited by 31 publications

(20 citation statements)

References 43 publications

(46 reference statements)

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“…The repertoire of enzyme isoforms expressed in cancer cells is markedly altered from the normal counterparts (29)(30)(31)(32)(33)(34); however, the consequences of these changes for the O-glycoproteome and carcinogenesis remain unknown. The locus 9q22 including the GALNT12 gene is a susceptibility locus for colorectal cancer (35) and heterozygous germ line as well as somatic inactivating mutations have been identified in cancer patients (36).…”

Section: Discussionmentioning

confidence: 99%

Probing isoform-specific functions of polypeptide GalNAc-transferases using zinc finger nuclease glycoengineered SimpleCells

Schjoldager

Vakhrushev²,

Kong³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

120

124

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Our knowledge of the O-glycoproteome [N-acetylgalactosamine (GalNAc) type] is highly limited. The O-glycoproteome is differentially regulated in cells by dynamic expression of a subset of 20 polypeptide GalNAc-transferases (GalNAc-Ts), and methods to identify important functions of individual GalNAc-Ts are largely unavailable. We recently introduced SimpleCells, i.e., human cell lines made deficient in O-glycan extension by zinc finger nuclease targeting of a key gene in Oglycan elongation (Cosmc), which allows for proteome-wide discovery of O-glycoproteins. Here we have extended the SimpleCell concept to include proteome-wide discovery of unique functions of individual GalNAc-Ts. We used the GalNAc-T2 isoform implicated in dyslipidemia and the human HepG2 liver cell line to demonstrate unique functions of this isoform. We confirm that GalNAc-T2-directed site-specific Oglycosylation inhibits proprotein activation of the lipase inhibitor ANGPTL3 in HepG2 cells and further identify eight O-glycoproteins exclusively glycosylated by T2 of which one, ApoC-III, is implicated in dyslipidemia. Our study supports an essential role for GalNAc-T2 in lipid metabolism, provides serum biomarkers for GalNAc-T2 enzyme function, and validates the use of GALNT gene targeting with SimpleCells for broad discovery of disease-causing deficiencies in O-glycosylation. The presented glycoengineering strategy opens the way for proteome-wide discovery of functions of GalNAc-T isoforms and their role in congenital diseases and disorders.apolipoproteins | angiopoietin-like proteins | genetic engineering | glycoproteins T he GALNT2 gene involved in O-glycosylation has been associated with aberrant serum levels of triglyceride (TG) and highdensity lipoprotein cholesterol (HDL-C) by several genome-wide association studies (GWAS) (1, 2). A direct functional role of this gene was obtained by transient knockdown and overexpression of galnt2 in mouse liver, which resulted in increased and lowered plasma HDL-C, respectively (3). GALNT2 is a member of the largest family of homologous glycosyltransferase isoforms (up to 20) catalyzing the same glycosidic linkage (GalNAcα1-O-Ser/Thr) and initiating protein O-glycosylation (4, 5). These isoforms have overlapping but distinct peptide substrate specificities and identifying essential unique functions for individual GalNAc-T isoforms has been notoriously difficult. In search of putative functions of GALNT2 in lipid metabolism, we previously screened a number of known and predicted O-glycoproteins with roles in lipid metabolism for O-glycosylation by the encoded GalNAc-T2 enzyme and identified ANGPTL3 (6). We found that site-specific O-glycosylation of a Thr residue adjacent to the proprotein convertase (PC) processing site in ANGPTL3 that activates this lipase inhibitor was performed only by the GalNAc-T2 isoform. More recently, a heterozygous mutation in GALNT2 resulting in slightly reduced kinetic properties of the encoded GalNAc-T2 enzyme was found in two probands with elevated HDL and reduced TG (7). ...

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Section: Discussionmentioning

confidence: 99%

Probing isoform-specific functions of polypeptide GalNAc-transferases using zinc finger nuclease glycoengineered SimpleCells

Schjoldager

Vakhrushev²,

Kong³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

120

124

View full text Add to dashboard Cite

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“…6B). Furthermore, glycosylation was specifically performed by the GalNAc-T3 isoform, which, as inhibin ␣, is highly expressed in the testis (30,31).…”

Section: Discussionmentioning

confidence: 99%

A Systematic Study of Site-specific GalNAc-type O-Glycosylation Modulating Proprotein Convertase Processing

Schjoldager

Vester-Christensen

Goth

et al. 2011

Journal of Biological Chemistry

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Background: GalNAc-type O-glycosylation is emerging as a co-regulator of proprotein convertase processing of proteins. Results: O-Glycosylation within at least Ϯ3 residues of the RXXR substrate motif for furin affected processing. Conclusion: Site-specific O-glycosylation by 20 polypeptide GalNAc transferases have wide co-regulatory functions in proprotein processing. Significance: This is the first systematic study that paves the way for wider co-regulatory functions of O-glycosylation in protein processing.

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“…As the GalNAc is necessary for the transfer of sialic acid to create STn structure, one can say that the efficient GalNAc-transferase activity is crucial for STn expression. Logically, cells lacking these activities are therefore unable to express STn or any other GalNAc-based O -glycans, as observed in the testis for spermatogonia and Sertoli cells [1]. However, to date, there is no demonstration that the quantity or the quality (e.g., clustering or specific sites) of O -GalNAcylation of proteins affects the subsequent sialylation of GalNAc residues.…”

Section: Sialyl-tn Structure and Biosynthesismentioning

confidence: 99%

Sialyl-Tn in Cancer: (How) Did We Miss the Target?

2012

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Sialyl-Tn antigen (STn) is a short O-glycan containing a sialic acid residue α2,6-linked to GalNAcα-O-Ser/Thr. The biosynthesis of STn is mediated by a specific sialyltransferase termed ST6GalNAc I, which competes with O-glycans elongating glycosyltransferases and prevents cancer cells from exhibiting longer O-glycans. While weakly expressed by fetal and normal adult tissues, STn is expressed by more than 80% of human carcinomas and in all cases, STn detection is associated with adverse outcome and decreased overall survival for the patients. Because of its pan-carcinoma expression associated with an adverse outcome, an anti-cancer vaccine, named Theratope, has been designed towards the STn epitope. In spite of the great enthusiasm around this immunotherapy, Theratope failed on Phase III clinical trial. However, in lieu of missing this target, one should consider to revise the Theratope design and the actual facts. In this review, we highlight the many lessons that can be learned from this failure from the immunological standpoint, as well as from the drug design and formulation and patient selection. Moreover, an irrefutable knowledge is arising from novel immunotherapies targeting other carbohydrate antigens and STn carrier proteins, such as MUC1, that will warrantee the future development of more successful anti-STn immunotherapy strategies.

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Changes in the profile of simple mucin-type O-glycans and polypeptide GalNAc-transferases in human testis and testicular neoplasms are associated with germ cell maturation and tumour differentiation

Cited by 31 publications

References 43 publications

Probing isoform-specific functions of polypeptide GalNAc-transferases using zinc finger nuclease glycoengineered SimpleCells

Probing isoform-specific functions of polypeptide GalNAc-transferases using zinc finger nuclease glycoengineered SimpleCells

A Systematic Study of Site-specific GalNAc-type O-Glycosylation Modulating Proprotein Convertase Processing

Sialyl-Tn in Cancer: (How) Did We Miss the Target?

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