1
|
Aryal RP, Noel M, Zeng J, Matsumoto Y, Sinard R, Waki H, Erger F, Reusch B, Beck BB, Cummings RD. Cosmc regulates O-glycan extension in murine hepatocytes. Glycobiology 2024; 34:cwae069. [PMID: 39216105 PMCID: PMC11398974 DOI: 10.1093/glycob/cwae069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2024] [Revised: 08/20/2024] [Accepted: 08/29/2024] [Indexed: 09/04/2024] Open
Abstract
Hepatocytes synthesize a vast number of glycoproteins found in their membranes and secretions, many of which contain O-glycans linked to Ser/Thr residues. As the functions and distribution of O-glycans on hepatocyte-derived membrane glycoproteins and blood glycoproteins are not well understood, we generated mice with a targeted deletion of Cosmc (C1Galt1c1) in hepatocytes. Liver glycoproteins in WT mice express typical sialylated core 1 O-glycans (T antigen/CD176) (Galβ1-3GalNAcα1-O-Ser/Thr), whereas the Cosmc knockout hepatocytes (HEP-Cosmc-KO) lack extended O-glycans and express the Tn antigen (CD175) (GalNAcα1-O-Ser/Thr). Tn-containing glycoproteins occur in the sera of HEP-Cosmc-KO mice but not in WT mice. The LDL-receptor (LDLR), a well-studied O-glycosylated glycoprotein in hepatocytes, behaves as a ∼145kD glycoprotein in WT liver lysates, whereas it is reduced to ∼120 kDa in lysates from HEP-Cosmc-KO mice. Interestingly, the expression of the LDLR, as well as HMG-CoA reductase, which is typically altered in response to dysregulated cholesterol metabolism, are similar between WT and HEP-Cosmc-KO mice, indicating no significant effect by Cosmc deletion on either LDLR stability or cholesterol metabolism. Consistent with this, we observed no detectable phenotype in the HEP-Cosmc-KO mice regarding development, appearance or aging compared to WT. These results provide surprising, novel information about the pathway of O-glycosylation in the liver.
Collapse
Affiliation(s)
- Rajindra P Aryal
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA 02115, United States
| | - Maxence Noel
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA 02115, United States
| | - Junwei Zeng
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA 02115, United States
| | - Yasuyuki Matsumoto
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA 02115, United States
| | - Rachael Sinard
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA 02115, United States
| | - Hannah Waki
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA 02115, United States
| | - Florian Erger
- Institute of Human Genetics, University Hospital Cologne, Faculty of Medicine, University of Cologne, Kerpenerstr. 34, Cologne 50931, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Robert-Koch-Str. 21, Cologne 50931, Germany
| | - Björn Reusch
- Institute of Human Genetics, University Hospital Cologne, Faculty of Medicine, University of Cologne, Kerpenerstr. 34, Cologne 50931, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Robert-Koch-Str. 21, Cologne 50931, Germany
| | - Bodo B Beck
- Institute of Human Genetics, University Hospital Cologne, Faculty of Medicine, University of Cologne, Kerpenerstr. 34, Cologne 50931, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Robert-Koch-Str. 21, Cologne 50931, Germany
| | - Richard D Cummings
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA 02115, United States
| |
Collapse
|
2
|
Radziejewska I. Tumor-associated carbohydrate antigens of MUC1 - Implication in cancer development. Biomed Pharmacother 2024; 174:116619. [PMID: 38643541 DOI: 10.1016/j.biopha.2024.116619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 04/12/2024] [Accepted: 04/17/2024] [Indexed: 04/23/2024] Open
Abstract
Glycosylation of cancerous epithelial MUC1 protein is specifically altered in comparison to that which is presented by healthy cells. One of such changes is appearing tumor-associated carbohydrate antigens (TACAs) which are rare in normal tissues and are highly correlated with poor clinical outcomes and cancer progression. This review summarizes and describes the role of Tn, T antigens, their sialylated forms as well as fucosylated Lewis epitopes in different aspects of tumor development, progression, and metastasis. Finally, applications of MUC1 glycan epitopes as potential targets for therapeutic strategy of cancers are notified. One of the novelties of this review is presentation of TACAs as inherently connected with MUC1 mucin.
Collapse
Affiliation(s)
- Iwona Radziejewska
- Department of Medical Chemistry, Medical University of Białystok, ul. Mickiewicza 2, Białystok 15-222, Poland.
| |
Collapse
|
3
|
Sanji AS, J M, Gurav MJ, Batra SK, Chachadi VB. Cancer snap-shots: Biochemistry and glycopathology of O-glycans: A review. Int J Biol Macromol 2024; 260:129318. [PMID: 38232866 DOI: 10.1016/j.ijbiomac.2024.129318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 01/05/2024] [Accepted: 01/05/2024] [Indexed: 01/19/2024]
Abstract
Cancer pathogenesis is strongly linked to the qualitative and quantitative alteration of the cell surface glycans, that are glycosidically linked to proteins and lipids. Glycans that are covalently linked to the polypeptide backbone of a protein through nitrogen or oxygen, are known as N-glycans or O-glycans, respectively. Although the role of glycans in the expression, physiology, and communication of cells is well documented, the function of these glycans in tumor biology is not fully elucidated. In this context, current review summarizes biosynthesis, modifications and pathological implications of O-glycans The review also highlights illustrative examples of cancer types modulated by aberrant O-glycosylation. Related O-glycans like Thomsen-nouveau (Tn), Thomsen-Friedenreich (TF), Lewisa/x, Lewisb/y, sialyl Lewisa/x and some other O-glycans are discussed in detail. Since, the overexpression of O-glycans are attributed to the aggressiveness and metastatic behavior of cancer cells, the current review attempts to understand the relation between metastasis and O-glycans.
Collapse
Affiliation(s)
- Ashwini S Sanji
- P. G. Department of Studies in Biochemistry, Karnatak University, Dharwad, Karnataka 580 003, India
| | - Manasa J
- P. G. Department of Studies in Biochemistry, Karnatak University, Dharwad, Karnataka 580 003, India
| | - Maruti J Gurav
- P. G. Department of Studies in Biochemistry, Karnatak University, Dharwad, Karnataka 580 003, India
| | - Surinder K Batra
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA; Fred and Pamela Buffett Cancer Center, Eppley Institute for Research in Cancer and Allied Disease, University of Nebraska Medical Center, Omaha, NE, USA
| | - Vishwanath B Chachadi
- P. G. Department of Studies in Biochemistry, Karnatak University, Dharwad, Karnataka 580 003, India.
| |
Collapse
|
4
|
Mercanoglu B, Karstens KF, Giannou AD, Meiners J, Lücke J, Seeger P, Brackrock V, Güngör C, Izbicki JR, Bockhorn M, Hackert T, Melling N, Wolters-Eisfeld G. A Comprehensive Analysis of Tn and STn Antigen Expression in Esophageal Adenocarcinoma. Cancers (Basel) 2024; 16:240. [PMID: 38254730 PMCID: PMC10814236 DOI: 10.3390/cancers16020240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 12/29/2023] [Accepted: 01/02/2024] [Indexed: 01/24/2024] Open
Abstract
Differential glycosylation, marked by the presence of truncated O-glycans, is a distinctive feature of epithelial-derived cancers. However, there is a notable gap in research regarding the expression of Tn and STn antigens in esophageal adenocarcinoma (EAC). To address this, we employed commercially available antibodies, previously validated for Tn and STn antigens, to analyze two cohorts of EAC tissues. Initially, large-area tissue sections from formalin-fixed paraffin-embedded (FFPE) EAC and corresponding healthy tissues were subjected to immunohistochemistry (IHC) staining and scoring. Subsequently, we evaluated the RNA expression levels of crucial O-glycosylation related genes-C1GALT1 and C1GALT1C1-using a quantitative real-time polymerase chain reaction (qRT-PCR). In a comprehensive analysis, a substantial cohort of EAC tissues (n = 311 for Tn antigen, n = 351 for STn antigen) was investigated and correlated with clinicopathological data. Our findings revealed that Tn and STn antigens are highly expressed (approximately 71% for both) in EAC, with this expression being tumor-specific. Notably, Tn antigen expression correlates significantly with the depth of tumor cell infiltration (p = 0.026). These antigens emerge as valuable markers and potential therapeutic targets for esophageal adenocarcinoma.
Collapse
Affiliation(s)
- Baris Mercanoglu
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Karl-Frederick Karstens
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Anastasios D. Giannou
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
- Section of Molecular Immunology und Gastroenterology, I. Department of Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Jan Meiners
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
- Department of Pathology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Jöran Lücke
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
- Section of Molecular Immunology und Gastroenterology, I. Department of Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Philipp Seeger
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Vera Brackrock
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Cenap Güngör
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Jakob R. Izbicki
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Maximilian Bockhorn
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
- Department of General and Visceral Surgery, University Medical Center Oldenburg, 26133 Oldenburg, Germany
| | - Thilo Hackert
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Nathaniel Melling
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| | - Gerrit Wolters-Eisfeld
- Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany (A.D.G.); (J.L.); (C.G.); (J.R.I.); (M.B.); (T.H.); (N.M.)
| |
Collapse
|
5
|
Radziejewska I. Galectin-3 and Epithelial MUC1 Mucin-Interactions Supporting Cancer Development. Cancers (Basel) 2023; 15:2680. [PMID: 37345016 DOI: 10.3390/cancers15102680] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 05/04/2023] [Accepted: 05/05/2023] [Indexed: 06/23/2023] Open
Abstract
Aberrant glycosylation of cell surface proteins is a very common feature of many cancers. One of the glycoproteins, which undergoes specific alterations in the glycosylation of tumor cells is epithelial MUC1 mucin, which is highly overexpressed in the malignant state. Such changes lead to the appearance of tumor associated carbohydrate antigens (TACAs) on MUC1, which are rarely seen in healthy cells. One of these structures is the Thomsen-Friedenreich disaccharide Galβ1-3GalNAc (T or TF antigen), which is typical for about 90% of cancers. It was revealed that increased expression of the T antigen has a big impact on promoting cancer progression and metastasis, among others, due to the interaction of this antigen with the β-galactose binding protein galectin-3 (Gal-3). In this review, we summarize current information about the interactions between the T antigen on MUC1 mucin and Gal-3, and their impact on cancer progression and metastasis.
Collapse
Affiliation(s)
- Iwona Radziejewska
- Department of Medical Chemistry, Medical University of Białystok, ul. Mickiewicza 2a, 15-222 Białystok, Poland
| |
Collapse
|
6
|
Zemkollari M, Blaukopf M, Grabherr R, Staudacher E. Expression and Characterisation of the First Snail-Derived UDP-Gal: Glycoprotein-N-acetylgalactosamine β-1,3-Galactosyltransferase (T-Synthase) from Biomphalaria glabrata. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28020552. [PMID: 36677618 PMCID: PMC9865085 DOI: 10.3390/molecules28020552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 12/21/2022] [Accepted: 12/30/2022] [Indexed: 01/09/2023]
Abstract
UDP-Gal: glycoprotein-N-acetylgalactosamine β-1,3-galactosyltransferase (T-synthase, EC 2.4.1.122) catalyses the transfer of the monosaccharide galactose from UDP-Gal to GalNAc-Ser/Thr, synthesizing the core 1 mucin type O-glycan. Such glycans play important biological roles in a number of recognition processes. The crucial role of these glycans is acknowledged for mammals, but a lot remains unknown regarding invertebrate and especially mollusc O-glycosylation. Although core O-glycans have been found in snails, no core 1 β-1,3-galactosyltransferase has been described so far. Here, the sequence of the enzyme was identified by a BlastP search of the NCBI Biomphalaria glabrata database using the human T-synthase sequence (NP_064541.1) as a template. The obtained gene codes for a 388 amino acids long transmembrane protein with two putative N-glycosylation sites. The coding sequence was synthesised and expressed in Sf9 cells. The expression product of the putative enzyme displayed core 1 β-1,3-galactosyltransferase activity using pNP-α-GalNAc as the substrate. The enzyme showed some sequence homology (49.40% with Homo sapiens, 53.69% with Drosophila melanogaster and 49.14% with Caenorhabditis elegans) and similar biochemical parameters with previously characterized T-synthases from other phyla. In this study we present the identification, expression and characterisation of the UDP-Gal: glycoprotein-N-acetylgalactosamine β-1,3-galactosyltransferase from the fresh-water snail Biomphalaria glabrata, which is the first cloned T-synthase from mollusc origin.
Collapse
Affiliation(s)
- Marilica Zemkollari
- Department of Chemistry, University of Natural Resources and Life Sciences, 1190 Vienna, Austria
| | - Markus Blaukopf
- Department of Chemistry, University of Natural Resources and Life Sciences, 1190 Vienna, Austria
| | - Reingard Grabherr
- Department of Biotechnology, University of Natural Resources and Life Sciences, 1190 Vienna, Austria
| | - Erika Staudacher
- Department of Chemistry, University of Natural Resources and Life Sciences, 1190 Vienna, Austria
- Correspondence: ; Tel.: +43-1-47654-77263
| |
Collapse
|
7
|
Zhang Y, Sun L, Lei C, Li W, Han J, Zhang J, Zhang Y. A Sweet Warning: Mucin-Type O-Glycans in Cancer. Cells 2022; 11:cells11223666. [PMID: 36429094 PMCID: PMC9688771 DOI: 10.3390/cells11223666] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/12/2022] [Accepted: 11/15/2022] [Indexed: 11/22/2022] Open
Abstract
Glycosylation is a common post-translational modification process of proteins. Mucin-type O-glycosylation is an O-glycosylation that starts from protein serine/threonine residues. Normally, it is involved in the normal development and differentiation of cells and tissues, abnormal glycosylation can lead to a variety of diseases, especially cancer. This paper reviews the normal biosynthesis of mucin-type O-glycans and their role in the maintenance of body health, followed by the mechanisms of abnormal mucin-type O-glycosylation in the development of diseases, especially tumors, including the effects of Tn, STn, T antigen, and different glycosyltransferases, with special emphasis on their role in the development of gastric cancer. Finally, tumor immunotherapy targeting mucin-type O-glycans was discussed.
Collapse
Affiliation(s)
- Yuhan Zhang
- Medical College of Yan’an University, Yan’an University, Yan’an 716000, China
| | - Lingbo Sun
- Medical College of Yan’an University, Yan’an University, Yan’an 716000, China
- Correspondence: (L.S.); (Y.Z.)
| | - Changda Lei
- Department of Gastroenterology, Ninth Hospital of Xi‘an, Xi’an 710054, China
| | - Wenyan Li
- Medical College of Yan’an University, Yan’an University, Yan’an 716000, China
| | - Jiaqi Han
- Medical College of Yan’an University, Yan’an University, Yan’an 716000, China
| | - Jing Zhang
- Medical College of Yan’an University, Yan’an University, Yan’an 716000, China
| | - Yuecheng Zhang
- Key Laboratory of Analytical Technology and Detection of Yan’an, College of Chemistry and Chemical Engineering, Yan’an University, Yan’an 716000, China
- Correspondence: (L.S.); (Y.Z.)
| |
Collapse
|
8
|
Xia T, Xiang T, Xie H. Update on the role of C1GALT1 in cancer (Review). Oncol Lett 2022; 23:97. [PMID: 35154428 PMCID: PMC8822393 DOI: 10.3892/ol.2022.13217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 01/17/2022] [Indexed: 12/03/2022] Open
Abstract
Cancer remains one of the most difficult diseases to treat. In the quest for early diagnoses to improve patient survival and prognosis, targeted therapies have become a hot research topic in recent years. Glycosylation is the most common posttranslational modification in mammalian cells. Core 1β1,3-galactosyltransferase (C1GALT1) is a key glycosyltransferase in the glycosylation process and is the key enzyme in the formation of the core 1 structure on which most complex and branched O-glycans are formed. A recent study reported that C1GALT1 was aberrantly expressed in tumors. In cancer cells, C1GALT1 is regulated by different factors. In the present review, the expression of C1GALT1 in different tumors and its possible molecular mechanisms of action are described and the role of C1GALT1 in cancer development is discussed.
Collapse
Affiliation(s)
- Tong Xia
- Hunan Province Key Laboratory of Tumor Cellular and Molecular Pathology, Institute of Cancer Research, School of Medicine, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Ting Xiang
- Hunan Province Key Laboratory of Tumor Cellular and Molecular Pathology, Institute of Cancer Research, School of Medicine, University of South China, Hengyang, Hunan 421001, P.R. China
| | - Hailong Xie
- Hunan Province Key Laboratory of Tumor Cellular and Molecular Pathology, Institute of Cancer Research, School of Medicine, University of South China, Hengyang, Hunan 421001, P.R. China
| |
Collapse
|
9
|
Expression and Impact of C1GalT1 in Cancer Development and Progression. Cancers (Basel) 2021; 13:cancers13246305. [PMID: 34944925 PMCID: PMC8699795 DOI: 10.3390/cancers13246305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/10/2021] [Accepted: 12/13/2021] [Indexed: 12/25/2022] Open
Abstract
Simple Summary C1GalT1 is one of the enzymes that catalyze the addition of sugar residues to proteins (protein glycosylation). It specifically controls the synthesis and formation of a special disaccharide structure Galβ1,3GalNAcα-, which occurs predominately in cancer but rarely in normal cells. Recent studies have shown that C1GalT1 is overexpressed in many common cancers including colon, breast, gastric, lung, head and neck, pancreatic, esophageal, prostate, and hepatocellular cancer. C1GalT1 overexpression is also often associated with poorer prognosis and poorer patient survival. This review summarizes our current understanding of the expression of C1GalT1 in various cancers and discusses the impact of C1GalT change on cancer cell activities in cancer development and progression. Abstract C1GalT1 (T-synthase) is one of the key glycosyltransferases in the biosynthesis of O-linked mucin-type glycans of glycoproteins. It controls the formation of Core-1 disaccharide Galβ1,3GalNAcα- (Thomsen–Friedenreich oncofetal antigen, T or TF antigen) and Core-1-associated carbohydrate structures. Recent studies have shown that C1GalT1 is overexpressed in many cancers of epithelial origin including colon, breast, gastric, head and neck, pancreatic, esophageal, prostate, and hepatocellular cancer. Overexpression of C1GalT1 is often seen to also be associated with poorer prognosis and poorer patient survival. Change of C1GalT1 expression causes glycosylation changes of many cell membrane glycoproteins including mucin proteins, growth factor receptors, adhesion molecules, and death receptors. This leads to alteration of the interactions of these cell surface molecules with their binding ligands, resulting in changes of cancer cell activity and behaviors. This review summarizes our current understanding of the expression of C1GalT1 in various cancers and discusses the impact of C1GalT change on cancer cell activities in cancer development and progression.
Collapse
|
10
|
Zeng J, Aryal RP, Stavenhagen K, Luo C, Liu R, Wang X, Chen J, Li H, Matsumoto Y, Wang Y, Wang J, Ju T, Cummings RD. Cosmc deficiency causes spontaneous autoimmunity by breaking B cell tolerance. SCIENCE ADVANCES 2021; 7:eabg9118. [PMID: 34613773 PMCID: PMC8494437 DOI: 10.1126/sciadv.abg9118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 08/17/2021] [Indexed: 05/12/2023]
Abstract
Factors regulating the induction and development of B cell–mediated autoimmunity are not well understood. Here, we report that targeted deletion in murine B cells of X-linked Cosmc, encoding the chaperone required for expression of core 1 O-glycans, causes the spontaneous development of autoimmune pathologies due to a breakdown of B cell tolerance. BC-CosmcKO mice display multiple phenotypic abnormalities, including severe weight loss, ocular manifestations, lymphadenopathy, and increased female-associated mortality. Disruption of B cell tolerance in BC-CosmcKO mice is manifested as elevated self-reactive IgM and IgG autoantibodies. Cosmc-deficient B cells exhibit enhanced basal activation and responsiveness to stimuli. There is also an elevated frequency of spontaneous germinal center B cells in BC-CosmcKO mice. Mechanistically, loss of Cosmc confers enhanced B cell receptor (BCR) signaling through diminished BCR internalization. The results demonstrate that Cosmc, through control of core 1 O-glycans, is a previously unidentified immune checkpoint gene in maintaining B cell tolerance.
Collapse
Affiliation(s)
- Junwei Zeng
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Rajindra P. Aryal
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Kathrin Stavenhagen
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Chi Luo
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Renyan Liu
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Xiaohui Wang
- Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - Jiaxuan Chen
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Hao Li
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Yasuyuki Matsumoto
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Yingchun Wang
- Department of Biochemistry, Emory University, Atlanta, GA, USA
| | - Jianmei Wang
- Department of Biochemistry, Emory University, Atlanta, GA, USA
| | - Tongzhong Ju
- Department of Biochemistry, Emory University, Atlanta, GA, USA
| | - Richard D. Cummings
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| |
Collapse
|
11
|
Hansen AL, Reily C, Novak J, Renfrow MB. Immunoglobulin A Glycosylation and Its Role in Disease. EXPERIENTIA SUPPLEMENTUM (2012) 2021; 112:433-477. [PMID: 34687019 DOI: 10.1007/978-3-030-76912-3_14] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Human IgA is comprised of two subclasses, IgA1 and IgA2. Monomeric IgA (mIgA), polymeric IgA (pIgA), and secretory IgA (SIgA) are the main molecular forms of IgA. The production of IgA rivals all other immunoglobulin isotypes. The large quantities of IgA reflect the fundamental roles it plays in immune defense, protecting vulnerable mucosal surfaces against invading pathogens. SIgA dominates mucosal surfaces, whereas IgA in circulation is predominately monomeric. All forms of IgA are glycosylated, and the glycans significantly influence its various roles, including antigen binding and the antibody effector functions, mediated by the Fab and Fc portions, respectively. In contrast to its protective role, the aberrant glycosylation of IgA1 has been implicated in the pathogenesis of autoimmune diseases, such as IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN). Furthermore, detailed characterization of IgA glycosylation, including its diverse range of heterogeneity, is of emerging interest. We provide an overview of the glycosylation observed for each subclass and molecular form of IgA as well as the range of heterogeneity for each site of glycosylation. In many ways, the role of IgA glycosylation is in its early stages of being elucidated. This chapter provides an overview of the current knowledge and research directions.
Collapse
Affiliation(s)
- Alyssa L Hansen
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Colin Reily
- Departments of Medicine and Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jan Novak
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - Matthew B Renfrow
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA.
| |
Collapse
|
12
|
Mucin-Type O-GalNAc Glycosylation in Health and Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1325:25-60. [PMID: 34495529 DOI: 10.1007/978-3-030-70115-4_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mucin-type GalNAc O-glycosylation is one of the most abundant and unique post-translational modifications. The combination of proteome-wide mapping of GalNAc O-glycosylation sites and genetic studies with knockout animals and genome-wide analyses in humans have been instrumental in our understanding of GalNAc O-glycosylation. Combined, such studies have revealed well-defined functions of O-glycans at single sites in proteins, including the regulation of pro-protein processing and proteolytic cleavage, as well as modulation of receptor functions and ligand binding. In addition to isolated O-glycans, multiple clustered O-glycans have an important function in mammalian biology by providing structural support and stability of mucins essential for protecting our inner epithelial surfaces, especially in the airways and gastrointestinal tract. Here the many O-glycans also provide binding sites for both endogenous and pathogen-derived carbohydrate-binding proteins regulating critical developmental programs and helping maintain epithelial homeostasis with commensal organisms. Finally, O-glycan changes have been identified in several diseases, most notably in cancer and inflammation, where the disease-specific changes can be used for glycan-targeted therapies. This chapter will review the biosynthesis, the biology, and the translational perspectives of GalNAc O-glycans.
Collapse
|
13
|
Gollamudi S, Lekhraj R, Lalezari S, Lalezari P. COSMC mutations reduce T-synthase activity in advanced Alzheimer's disease. ALZHEIMER'S & DEMENTIA (NEW YORK, N. Y.) 2020; 6:e12040. [PMID: 32607408 PMCID: PMC7317644 DOI: 10.1002/trc2.12040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/14/2020] [Accepted: 05/11/2020] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Mutations in brain tissues that cumulate with age may contribute to Alzheimer's disease (AD). Abnormal glycoprotein and Tn antigen expression have been demonstrated in AD. We identified C1GALT1C1/COSMC mutations in AD and age-matched normals without AD. The COSMC coding mutations resulted in a significant reduction in T-synthase activity in advanced AD cases. METHODS Identification of COSMC mutations, Real-Time Quantitative Reverse Transcription PCR (Q-RT-PCR), western blotting, and T-synthase activity assays. RESULTS COSMC mutations were detected in the promotor, coding region and 3'UTR in AD and normals. COSMC coding mutations demonstrated a correlation with AD progression. T-synthase levels were significantly elevated in advanced AD compared to AD III (P = 0.03) and normals (P = 0.002). T-synthase activity in advanced AD {Braak and Braak (B&B) stages V and VI} with COSMC coding mutations was 3-fold lower than advanced AD without mutations, and 1.3-fold lower than normal (P = 0.001) and AD B&B stage III (P = 0.01) with coding mutations. DISCUSSION COSMC coding mutations significantly diminished T-synthase activity in advanced AD, potentially causing defective galactosylation.
Collapse
Affiliation(s)
- Seema Gollamudi
- Neurosurgery Research LaboratoryDepartment of NeurosurgeryMontefiore Medical Center and Albert Einstein College of MedicineBronxNew YorkUSA
| | - Rukmani Lekhraj
- Neurosurgery Research LaboratoryDepartment of NeurosurgeryMontefiore Medical Center and Albert Einstein College of MedicineBronxNew YorkUSA
| | - Shirin Lalezari
- Neurosurgery Research LaboratoryDepartment of NeurosurgeryMontefiore Medical Center and Albert Einstein College of MedicineBronxNew YorkUSA
| | - Parviz Lalezari
- Neurosurgery Research LaboratoryDepartment of NeurosurgeryMontefiore Medical Center and Albert Einstein College of MedicineBronxNew YorkUSA
| |
Collapse
|
14
|
Taujale R, Venkat A, Huang LC, Zhou Z, Yeung W, Rasheed KM, Li S, Edison AS, Moremen KW, Kannan N. Deep evolutionary analysis reveals the design principles of fold A glycosyltransferases. eLife 2020; 9:54532. [PMID: 32234211 PMCID: PMC7185993 DOI: 10.7554/elife.54532] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 03/31/2020] [Indexed: 12/26/2022] Open
Abstract
Glycosyltransferases (GTs) are prevalent across the tree of life and regulate nearly all aspects of cellular functions. The evolutionary basis for their complex and diverse modes of catalytic functions remain enigmatic. Here, based on deep mining of over half million GT-A fold sequences, we define a minimal core component shared among functionally diverse enzymes. We find that variations in the common core and emergence of hypervariable loops extending from the core contributed to GT-A diversity. We provide a phylogenetic framework relating diverse GT-A fold families for the first time and show that inverting and retaining mechanisms emerged multiple times independently during evolution. Using evolutionary information encoded in primary sequences, we trained a machine learning classifier to predict donor specificity with nearly 90% accuracy and deployed it for the annotation of understudied GTs. Our studies provide an evolutionary framework for investigating complex relationships connecting GT-A fold sequence, structure, function and regulation. Carbohydrates are one of the major groups of large biological molecules that regulate nearly all aspects of life. Yet, unlike DNA or proteins, carbohydrates are made without a template to follow. Instead, these molecules are built from a set of sugar-based building blocks by the intricate activities of a large and diverse family of enzymes known as glycosyltransferases. An incomplete understanding of how glycosyltransferases recognize and build diverse carbohydrates presents a major bottleneck in developing therapeutic strategies for diseases associated with abnormalities in these enzymes. It also limits efforts to engineer these enzymes for biotechnology applications and biofuel production. Taujale et al. have now used evolutionary approaches to map the evolution of a major subset of glycosyltransferases from species across the tree of life to understand how these enzymes evolved such precise mechanisms to build diverse carbohydrates. First, a minimal structural unit was defined based on being shared among a group of over half a million unique glycosyltransferase enzymes with different activities. Further analysis then showed that the diverse activities of these enzymes evolved through the accumulation of mutations within this structural unit, as well as in much more variable regions in the enzyme that extend from the minimal unit. Taujale et al. then built an extended family tree for this collection of glycosyltransferases and details of the evolutionary relationships between the enzymes helped them to create a machine learning framework that could predict which sugar-containing molecules were the raw materials for a given glycosyltransferase. This framework could make predictions with nearly 90% accuracy based only on information that can be deciphered from the gene for that enzyme. These findings will provide scientists with new hypotheses for investigating the complex relationships connecting the genetic information about glycosyltransferases with their structures and activities. Further refinement of the machine learning framework may eventually enable the design of enzymes with properties that are desirable for applications in biotechnology.
Collapse
Affiliation(s)
- Rahil Taujale
- Institute of Bioinformatics, University of Georgia, Athens, Georgia.,Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia
| | - Aarya Venkat
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - Liang-Chin Huang
- Institute of Bioinformatics, University of Georgia, Athens, Georgia
| | - Zhongliang Zhou
- Department of Computer Science, University of Georgia, Athens, Georgia
| | - Wayland Yeung
- Institute of Bioinformatics, University of Georgia, Athens, Georgia
| | - Khaled M Rasheed
- Department of Computer Science, University of Georgia, Athens, Georgia
| | - Sheng Li
- Department of Computer Science, University of Georgia, Athens, Georgia
| | - Arthur S Edison
- Institute of Bioinformatics, University of Georgia, Athens, Georgia.,Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - Kelley W Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - Natarajan Kannan
- Institute of Bioinformatics, University of Georgia, Athens, Georgia.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| |
Collapse
|
15
|
Xu F, Wang D, Cui J, Li J, Jiang H. Demethylation of the Cosmc Promoter Alleviates the Progression of Breast Cancer Through Downregulation of the Tn and Sialyl-Tn Antigens. Cancer Manag Res 2020; 12:1017-1027. [PMID: 32104083 PMCID: PMC7023867 DOI: 10.2147/cmar.s214553] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 12/24/2019] [Indexed: 01/28/2023] Open
Abstract
Background Aberrant gene methylation in breast cancer is associated with an unfavorable prognosis. Besides, abnormal Cosmc can induce the expression of Tn and STn antigens. The present study aimed to investigate the roles of Cosmc promoter methylation in breast cancer through the regulation of Tn and STn antigens. Methods The expression patterns of Cosmc and the Tn and STn antigens in breast cancer cell lines were determined. Cosmc was overexpressed to explore the effects of Cosmc on cell behavior, including the growth, migration, invasion, and apoptosis of breast cancer cells and tumor growth with in vitro and in vivo experiments. Afterwards, a methyltransferase and a methyltransferase inhibitor were used to alter the methylation status of Cosmc to explore the mechanisms related to Cosmc promoter methylation. Results Cosmc was poorly expressed in breast cancer cells. Cosmc overexpression inhibited cell growth, migration, and invasion while promoting apoptosis in breast cancer cells in vitro and restraining tumor growth in vivo. Cosmc promoter methylation was found to decrease the levels of Cosmc and increased the expression of the Tn and STn antigens in breast cancer. Conclusion In conclusion, the demethylation of Cosmc mitigates breast cancer progression through the repression of the Tn and STn antigens, which provides evidence for therapeutic considerations for a novel target against breast cancer.
Collapse
Affiliation(s)
- Feng Xu
- Department of Breast Surgery, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, People's Republic of China
| | - Dong Wang
- Department of Oncology, Affiliated Hospital of Inner Mongolia University for Nationalities, Tongliao 028000, People's Republic of China
| | - JianXiu Cui
- Department of Breast Surgery, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, People's Republic of China
| | - Jie Li
- Department of Breast Surgery, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, People's Republic of China
| | - Hongchuan Jiang
- Department of Breast Surgery, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, People's Republic of China
| |
Collapse
|
16
|
Cummings RD. "Stuck on sugars - how carbohydrates regulate cell adhesion, recognition, and signaling". Glycoconj J 2019; 36:241-257. [PMID: 31267247 DOI: 10.1007/s10719-019-09876-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 06/11/2019] [Indexed: 12/12/2022]
Abstract
We have explored the fundamental biological processes by which complex carbohydrates expressed on cellular glycoproteins and glycolipids and in secretions of cells promote cell adhesion and signaling. We have also explored processes by which animal pathogens, such as viruses, bacteria, and parasites adhere to glycans of animal cells and initiate disease. Glycans important in cell signaling and adhesion, such as key O-glycans, are essential for proper animal development and cellular differentiation, but they are also involved in many pathogenic processes, including inflammation, tumorigenesis and metastasis, and microbial and parasitic pathogenesis. The overall hypothesis guiding these studies is that glycoconjugates are recognized and bound by a growing class of proteins called glycan-binding proteins (GBPs or lectins) expressed by all types of cells. There is an incredible variety and diversity of GBPs in animal cells involved in binding N- and O-glycans, glycosphingolipids, and proteoglycan/glycosaminoglycans. We have specifically studied such molecular determinants recognized by selectins, galectins, and many other C-type lectins, involved in leukocyte recruitment to sites of inflammation in human tissues, lymphocyte trafficking, adhesion of human viruses to human cells, structure and immunogenicity of glycoproteins on the surfaces of human parasites. We have also explored the molecular basis of glycoconjugate biosynthesis by exploring the enzymes and molecular chaperones required for correct protein glycosylation. From these studies opportunities for translational biology have arisen, involving production of function-blocking antibodies, anti-glycan specific antibodies, and synthetic glycoconjugates, e.g. glycosulfopeptides, that specifically are recognized by GBPs. This invited short review is based in part on my presentation for the IGO Award 2019 given by the International Glycoconjugate Organization in Milan.
Collapse
Affiliation(s)
- Richard D Cummings
- Beth Israel Deaconess Medical Center, Harvard Medical School, CLS 11087 - 3 Blackfan Circle, Boston, MA, 02115, USA.
| |
Collapse
|
17
|
Sun X, Ju T, Cummings RD. Differential expression of Cosmc, T-synthase and mucins in Tn-positive colorectal cancers. BMC Cancer 2018; 18:827. [PMID: 30115016 PMCID: PMC6097208 DOI: 10.1186/s12885-018-4708-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 07/31/2018] [Indexed: 12/23/2022] Open
Abstract
Background The Tn neoantigen (GalNAcα1-O-Ser/Thr) is an O-glycan expressed in various types of human cancers. Studies in several Tn-expressing cancer cell lines and pancreatic tumors have identified loss of Cosmc expression caused by either mutations or promoter hypermethylation. In this study, we explored the mechanism(s) for Tn expression in human colorectal cancers (CRC). Methods Tn-expressing cell populations were isolated from CRC cell lines by Fluorescence-associated cell sorting (FACS). The expression of the Tn and sialylated Tn (STn) antigens, Cosmc, T-synthase, and mucins was characterized in paired specimens with CRC and in CRC cell lines by immunostaining, western blot, and qPCR. Results Using well-defined monoclonal antibodies, we confirmed prevalent Tn/STn expression in CRC samples. However, a majority of these tumors had elevated T-synthase activity and expression of both Cosmc and T-synthase proteins. Meanwhile, Tn antigen expression was not caused by mucin overproduction. In addition, we found that Tn-expressing CRC cell lines had either loss-of-function mutations in Cosmc or reversible Tn antigen expression, which was not caused by the deficiency of T-synthase activity. Conclusions Our results demonstrate multiple mechanisms for Tn expression in CRCs. Electronic supplementary material The online version of this article (10.1186/s12885-018-4708-8) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Xiaodong Sun
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, 3 Blackfan Circle, Room 11087, Boston, MA, 02115, USA.
| | - Tongzhong Ju
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA. .,Office of Biotechnology Products (OBP), Center for Drug Evaluation and Research (CDER), U. S. Food and Drug Administration, Bldg 52/72, Room 2120, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA.
| | - Richard D Cummings
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, 3 Blackfan Circle, Room 11087, Boston, MA, 02115, USA.
| |
Collapse
|
18
|
Hanes MS, Moremen KW, Cummings RD. Biochemical characterization of functional domains of the chaperone Cosmc. PLoS One 2017; 12:e0180242. [PMID: 28665962 PMCID: PMC5493369 DOI: 10.1371/journal.pone.0180242] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 06/12/2017] [Indexed: 02/07/2023] Open
Abstract
Cosmc is an endoplasmic reticulum chaperone necessary for normal protein O-GalNAc glycosylation through regulation of T-synthase, its single client. Loss-of-function of Cosmc results in expression of the Tn antigen, which is associated with multiple human diseases including cancer. Despite intense interest in dysregulated expression of the Tn antigen, little is known about the structure and function of Cosmc, including domain organization, secondary structure, oligomerization, and co-factors. Limited proteolysis experiments show that Cosmc contains a structured N-terminal domain (CosmcΔ256), and biochemical characterization of CosmcΔ256 reveals wild type chaperone activity. Interestingly, CosmcE152K, which shows loss of function in vivo, exhibits wild type-like activity in vitro. Cosmc and CosmcE152K heterogeneously oligomerize and form monomeric, dimeric, trimeric, and tetrameric species, while CosmcΔ256 is predominantly monomeric as characterized by chemical crosslinking and blue native page electrophoresis. Additionally, Cosmc selectively binds divalent cations in thermal shift assays and metal binding is abrogated by the CosmcΔ256 truncation, and perturbed by the E152K mutation. Therefore, the N-terminal domain of Cosmc mediates T-synthase binding and chaperone function, whereas the C-terminal domain is necessary for oligomerization and metal binding. Our results provide new structure-function insight to Cosmc, indicate that Cosmc behaves as a modular protein and suggests points of modulation or regulation of in vivo chaperone function.
Collapse
Affiliation(s)
- Melinda S. Hanes
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Kelley W. Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, United States of America
| | - Richard D. Cummings
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States of America
| |
Collapse
|
19
|
Kellokumpu S, Hassinen A, Glumoff T. Glycosyltransferase complexes in eukaryotes: long-known, prevalent but still unrecognized. Cell Mol Life Sci 2016; 73:305-25. [PMID: 26474840 PMCID: PMC7079781 DOI: 10.1007/s00018-015-2066-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 09/28/2015] [Accepted: 10/08/2015] [Indexed: 01/08/2023]
Abstract
Glycosylation is the most common and complex cellular modification of proteins and lipids. It is critical for multicellular life and its abrogation often leads to a devastating disease. Yet, the underlying mechanistic details of glycosylation in both health and disease remain unclear. Partly, this is due to the complexity and dynamicity of glycan modifications, and the fact that not all the players are taken into account. Since late 1960s, a vast number of studies have demonstrated that glycosyltransferases typically form homomeric and heteromeric complexes with each other in yeast, plant and animal cells. To propagate their acceptance, we will summarize here accumulated data for their prevalence and potential functional importance for glycosylation focusing mainly on their mutual interactions, the protein domains mediating these interactions, and enzymatic activity changes that occur upon complex formation. Finally, we will highlight the few existing 3D structures of these enzyme complexes to pinpoint their individual nature and to emphasize that their lack is the main obstacle for more detailed understanding of how these enzyme complexes interact and function in a eukaryotic cell.
Collapse
Affiliation(s)
- Sakari Kellokumpu
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7, 90220, Oulu, Finland.
| | - Antti Hassinen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7, 90220, Oulu, Finland
| | - Tuomo Glumoff
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 7, 90220, Oulu, Finland
| |
Collapse
|
20
|
Vasconcelos-Dos-Santos A, Oliveira IA, Lucena MC, Mantuano NR, Whelan SA, Dias WB, Todeschini AR. Biosynthetic Machinery Involved in Aberrant Glycosylation: Promising Targets for Developing of Drugs Against Cancer. Front Oncol 2015; 5:138. [PMID: 26161361 PMCID: PMC4479729 DOI: 10.3389/fonc.2015.00138] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 06/02/2015] [Indexed: 12/22/2022] Open
Abstract
Cancer cells depend on altered metabolism and nutrient uptake to generate and keep the malignant phenotype. The hexosamine biosynthetic pathway is a branch of glucose metabolism that produces UDP-GlcNAc and its derivatives, UDP-GalNAc and CMP-Neu5Ac and donor substrates used in the production of glycoproteins and glycolipids. Growing evidence demonstrates that alteration of the pool of activated substrates might lead to different glycosylation and cell signaling. It is already well established that aberrant glycosylation can modulate tumor growth and malignant transformation in different cancer types. Therefore, biosynthetic machinery involved in the assembly of aberrant glycans are becoming prominent targets for anti-tumor drugs. This review describes three classes of glycosylation, O-GlcNAcylation, N-linked, and mucin type O-linked glycosylation, involved in tumor progression, their biosynthesis and highlights the available inhibitors as potential anti-tumor drugs.
Collapse
Affiliation(s)
| | - Isadora A Oliveira
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brasil
| | - Miguel Clodomiro Lucena
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brasil
| | - Natalia Rodrigues Mantuano
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brasil
| | - Stephen A Whelan
- Department of Biochemistry, Cardiovascular Proteomics Center, Boston University School of Medicine , Boston, MA , USA
| | - Wagner Barbosa Dias
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brasil
| | - Adriane Regina Todeschini
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro , Rio de Janeiro , Brasil
| |
Collapse
|
21
|
Kudelka MR, Ju T, Heimburg-Molinaro J, Cummings RD. Simple sugars to complex disease--mucin-type O-glycans in cancer. Adv Cancer Res 2015; 126:53-135. [PMID: 25727146 DOI: 10.1016/bs.acr.2014.11.002] [Citation(s) in RCA: 357] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mucin-type O-glycans are a class of glycans initiated with N-acetylgalactosamine (GalNAc) α-linked primarily to Ser/Thr residues within glycoproteins and often extended or branched by sugars or saccharides. Most secretory and membrane-bound proteins receive this modification, which is important in regulating many biological processes. Alterations in mucin-type O-glycans have been described across tumor types and include expression of relatively small-sized, truncated O-glycans and altered terminal structures, both of which are associated with patient prognosis. New discoveries in the identity and expression of tumor-associated O-glycans are providing new avenues for tumor detection and treatment. This chapter describes mucin-type O-glycan biosynthesis, altered mucin-type O-glycans in primary tumors, including mechanisms for structural changes and contributions to the tumor phenotype, and clinical approaches to detect and target altered O-glycans for cancer treatment and management.
Collapse
Affiliation(s)
- Matthew R Kudelka
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Tongzhong Ju
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA
| | | | - Richard D Cummings
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia, USA.
| |
Collapse
|
22
|
Sun Q, Zhang J, Zhou N, Liu X, Shen Y. DNA methylation in Cosmc promoter region and aberrantly glycosylated IgA1 associated with pediatric IgA nephropathy. PLoS One 2015; 10:e0112305. [PMID: 25647400 PMCID: PMC4315396 DOI: 10.1371/journal.pone.0112305] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 09/16/2014] [Indexed: 12/31/2022] Open
Abstract
IgA nephropathy (IgAN) is one of the most common glomerular diseases leading to end-stage renal failure. Elevation of aberrantly glycosylated IgA1 is a key feature of it. The expression of the specific molecular chaperone of core1ß1, 3galactosyl transferase (Cosmc) is known to be reduced in IgAN. We aimed to investigate whether the methylation of CpG islands of Cosmc gene promoter region could act as a possible mechanism responsible for down-regulation of Cosmc and related higher secretion of aberrantly glycosylated IgA1in lymphocytes from children with IgA nephropathy. Three groups were included: IgAN children (n = 26), other renal diseases (n = 11) and healthy children (n = 13). B-lymphocytes were isolated and cultured, treated or not with IL-4 or 5-Aza-2’-deoxycytidine (AZA). The levels of DNA methylation of Cosmc promotor region were not significantly different between the lymphocytes of the three children populations (P = 0.113), but there were significant differences between IgAN lymphocytes and lymphocytes of the other two children populations after IL-4 (P<0.0001) or AZA (P<0.0001). Cosmc mRNA expression was low in IgAN lymphocytes compared to the other two groups (P<0.0001). The level of aberrantly glycosylated IgA1 was markedly higher in IgAN group compared to the other groups (P<0.0001). After treatment with IL-4, the levels of Cosmc DNA methylation and aberrantly glycosylated IgA1 in IgAN lymphocytes were remarkably higher than the other two groups (P<0.0001) with more markedly decreased Cosmc mRNA content (P<0.0001). After treatment with AZA, the levels in IgAN lymphocytes were decreased, but was still remarkably higher than the other two groups (P<0.0001), while Cosmc mRNA content in IgAN lymphocytes were more markedly increased than the other two groups (P<0.0001). The alteration of DNA methylation by IL-4 or AZA specifically correlates in IgAN lymphocytes with alterations in Cosmc mRNA expression and with the level of aberrantly glycosylated IgA1 (r = −0.948, r = 0. 707). Our results suggested that hypermethylation of Cosmc promoter region could be a key mechanism for the reduction of Cosmc mRNA expression in IgAN lymphocytes with associated increase in aberrantly glycosylated IgA1.
Collapse
Affiliation(s)
- Qiang Sun
- Department of nephrology, Beijing Children’s Hospital, Capital Medical University, Beijing, China
| | - Jianqian Zhang
- Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing, China
| | - Nan Zhou
- Department of nephrology, Beijing Children’s Hospital, Capital Medical University, Beijing, China
| | - Xiaorong Liu
- Department of nephrology, Beijing Children’s Hospital, Capital Medical University, Beijing, China
| | - Ying Shen
- Department of nephrology, Beijing Children’s Hospital, Capital Medical University, Beijing, China
- * E-mail:
| |
Collapse
|
23
|
Ju T, Aryal RP, Kudelka MR, Wang Y, Cummings RD. The Cosmc connection to the Tn antigen in cancer. Cancer Biomark 2015; 14:63-81. [PMID: 24643043 DOI: 10.3233/cbm-130375] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The Tn antigen is a tumor-associated carbohydrate antigen that is not normally expressed in peripheral tissues or blood cells. Expression of this antigen, which is found in a majority of human carcinomas of all types, arises from a blockage in the normal O-glycosylation pathway in which glycans are extended from the common precursor GalNAcα1-O-Ser/Thr (Tn antigen). This precursor is generated in the Golgi apparatus on newly synthesized glycoproteins by a family of polypeptide α-N-acetylgalactosaminyltransferases (ppGalNAcTs) and then extended to the common core 1 O-glycan Galβ1-3GalNAcα1-O-Ser/Thr (T antigen) by a single enzyme termed the T-synthase (core 1 β3-galactosyltransferase or C1GalT). Formation of the active form of the T-synthase requires a unique molecular chaperone termed Cosmc, encoded by Cosmc on the X-chromosome (Xq24 in humans, Xc3 in mice). Cosmc resides in the endoplasmic reticulum (ER) and prevents misfolding, aggregation, and proteasome-dependent degradation of newly synthesized T-synthase. Loss of expression of active T-synthase or Cosmc can lead to expression of the Tn antigen, along with its sialylated version Sialyl Tn antigen as observed in several cancers. Both genetic and epigenetic pathways, in addition to potential metabolic regulation, can result in abnormal expression of the Tn antigen. Engineered expression of the Tn antigen by disruption of either C1GalT (T-syn) or Cosmc in mice is associated with a tremendous range of pathologies and engineered expression of the Tn antigen in mouse embryos leads to embryonic death. Studies indicate that many membrane glycoproteins expressing the Tn antigen and/or truncated O-glycans may be dysfunctional, due to degradation and/or misfolding. Thus, expression of normal O-glycans is associated with health and homeostasis whereas truncation of O-glycans, e.g. the Tn and/or Sialyl Tn antigens is associated with cancer and other pathologies.
Collapse
Affiliation(s)
- Tongzhong Ju
- Department of Biochemistry and the Emory Glycomics Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Rajindra P Aryal
- Department of Biochemistry and the Emory Glycomics Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Matthew R Kudelka
- Department of Biochemistry and the Emory Glycomics Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Yingchun Wang
- Department of Biochemistry and the Emory Glycomics Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Richard D Cummings
- Department of Biochemistry and the Emory Glycomics Center, Emory University School of Medicine, Atlanta, GA, USA
| |
Collapse
|
24
|
Liang DM, Liu JH, Wu H, Wang BB, Zhu HJ, Qiao JJ. Glycosyltransferases: mechanisms and applications in natural product development. Chem Soc Rev 2015; 44:8350-74. [DOI: 10.1039/c5cs00600g] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Glycosylation reactions mainly catalyzed by glycosyltransferases (Gts) occur almost everywhere in the biosphere, and always play crucial roles in vital processes.
Collapse
Affiliation(s)
- Dong-Mei Liang
- Department of Pharmaceutical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- China
| | - Jia-Heng Liu
- Department of Pharmaceutical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- China
| | - Hao Wu
- Department of Pharmaceutical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- China
| | - Bin-Bin Wang
- Department of Pharmaceutical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- China
| | - Hong-Ji Zhu
- Department of Pharmaceutical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- China
| | - Jian-Jun Qiao
- Department of Pharmaceutical Engineering
- School of Chemical Engineering and Technology
- Tianjin University
- Tianjin 300072
- China
| |
Collapse
|
25
|
Cellular signaling and production of galactose-deficient IgA1 in IgA nephropathy, an autoimmune disease. J Immunol Res 2014; 2014:197548. [PMID: 25152896 PMCID: PMC4134797 DOI: 10.1155/2014/197548] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 06/25/2014] [Indexed: 12/21/2022] Open
Abstract
Immunoglobulin A (IgA) nephropathy (IgAN), the leading cause of primary glomerulonephritis, is characterized by IgA1-containing immunodeposits in the glomeruli. IgAN is a chronic disease, with up to 40% of patients progressing to end-stage renal disease, with no disease-specific treatment. Multiple studies of the origin of the glomerular immunodeposits have linked elevated circulating levels of aberrantly glycosylated IgA1 (galactose-deficient in some O-glycans; Gd-IgA1) with formation of nephritogenic Gd-IgA1-containing immune complexes. Gd-IgA1 is recognized as an autoantigen in susceptible individuals by anti-glycan autoantibodies, resulting in immune complexes that may ultimately deposit in the kidney and induce glomerular injury. Genetic studies have revealed that an elevated level of Gd-IgA1 in the circulation of IgAN patients is a hereditable trait. Moreover, recent genome-wide association studies have identified several immunity-related loci that associated with IgAN. Production of Gd-IgA1 by IgA1-secreting cells of IgAN patients has been attributed to abnormal expression and activity of several key glycosyltransferases. Substantial evidence is emerging that abnormal signaling in IgA1-producing cells is related to the production of Gd-IgA1. As Gd-IgA1 is the key autoantigen in IgAN, understanding the genetic, biochemical, and environmental aspects of the abnormal signaling in IgA1-producing cells will provide insight into possible targets for future disease-specific therapy.
Collapse
|
26
|
Aryal RP, Ju T, Cummings RD. Identification of a novel protein binding motif within the T-synthase for the molecular chaperone Cosmc. J Biol Chem 2014; 289:11630-11641. [PMID: 24616093 DOI: 10.1074/jbc.m114.555870] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Prior studies suggested that the core 1 β3-galactosyltransferase (T-synthase) is a specific client of the endoplasmic reticulum chaperone Cosmc, whose function is required for T-synthase folding, activity, and consequent synthesis of normal O-glycans in all vertebrate cells. To explore whether the T-synthase encodes a specific recognition motif for Cosmc, we used deletion mutagenesis to identify a cryptic linear and relatively hydrophobic peptide in the N-terminal stem region of the T-synthase that is essential for binding to Cosmc (Cosmc binding region within T-synthase, or CBRT). Using this sequence information, we synthesized a peptide containing CBRT and found that it directly interacts with Cosmc and also inhibits Cosmc-assisted in vitro refolding of denatured T-synthase. Moreover, engineered T-synthase carrying mutations within CBRT exhibited diminished binding to Cosmc that resulted in the formation of inactive T-synthase. To confirm the general recognition of CBRT by Cosmc, we performed a domain swap experiment in which we inserted the stem region of the T-synthase into the human β4GalT1 and found that the CBRT element can confer Cosmc binding onto the β4GalT1 chimera. Thus, CBRT is a unique recognition motif for Cosmc to promote its regulation and formation of active T-synthase and represents the first sequence-specific chaperone recognition system in the ER/Golgi required for normal protein O-glycosylation.
Collapse
Affiliation(s)
- Rajindra P Aryal
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Tongzhong Ju
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
| | - Richard D Cummings
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
| |
Collapse
|
27
|
Ju T, Wang Y, Aryal RP, Lehoux SD, Ding X, Kudelka MR, Cutler C, Zeng J, Wang J, Sun X, Heimburg-Molinaro J, Smith DF, Cummings RD. Tn and sialyl-Tn antigens, aberrant O-glycomics as human disease markers. Proteomics Clin Appl 2013; 7:618-31. [PMID: 23857728 DOI: 10.1002/prca.201300024] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 04/24/2013] [Indexed: 12/12/2022]
Abstract
In many different human disorders, the cellular glycome is altered. An interesting but poorly understood alteration occurs in the mucin-type O-glycome, in which there is aberrant expression of the truncated O-glycans Tn (GalNAcα1-Ser/Thr) and its sialylated version sialyl-Tn (STn) (Neu5Acα2,6GalNAcα1-Ser/Thr). Both Tn and STn are tumor-associated carbohydrate antigens and tumor biomarkers, since they are not expressed normally and appear early in tumorigenesis. Moreover, their expression is strongly associated with poor prognosis and tumor metastasis. The Tn and STn antigens are also expressed in other human diseases and disorders, such as Tn syndrome and IgA nephropathy. The major pathological mechanism for expression of the Tn and STn antigens is compromised T-synthase activity, resulting from alteration of the X-linked gene that encodes for Cosmc, a molecular chaperone specifically required for the correct folding of T-synthase to form active enzyme. This review will summarize our current understanding of the Tn and STn antigens in terms of their biochemistry and role in pathology.
Collapse
Affiliation(s)
- Tongzhong Ju
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Yingchun Wang
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Rajindra P Aryal
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Sylvain D Lehoux
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Xiaokun Ding
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Matthew R Kudelka
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Christopher Cutler
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Junwei Zeng
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Jianmei Wang
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Xiaodong Sun
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | | | - David F Smith
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| | - Richard D Cummings
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, USA
| |
Collapse
|
28
|
Mi R, Song L, Wang Y, Ding X, Zeng J, Lehoux S, Aryal RP, Wang J, Crew VK, van Die I, Chapman AB, Cummings RD, Ju T. Epigenetic silencing of the chaperone Cosmc in human leukocytes expressing tn antigen. J Biol Chem 2012; 287:41523-33. [PMID: 23035125 DOI: 10.1074/jbc.m112.371989] [Citation(s) in RCA: 243] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cosmc is the specific molecular chaperone in the endoplasmic reticulum for T-synthase, a Golgi β3-galactosyltransferase that generates the core 1 O-glycan, Galβ1-3GalNAcα-Ser/Thr, in glycoproteins. Dysfunctional Cosmc results in the formation of inactive T-synthase and consequent expression of the Tn antigen (GalNAcα1-Ser/Thr), which is associated with several human diseases. However, the molecular regulation of expression of Cosmc, which is encoded by a single gene on Xq24, is poorly understood. Here we show that epigenetic silencing of Cosmc through hypermethylation of its promoter leads to loss of Cosmc transcripts in Tn4 cells, an immortalized B cell line from a male patient with a Tn-syndrome-like phenotype. These cells lack T-synthase activity and express the Tn antigen. Treatment of cells with 5-aza-2'-deoxycytidine causes restoration of Cosmc transcripts, restores T-synthase activity, and reduces Tn antigen expression. Bisulfite sequencing shows that CG dinucleotides in the Cosmc core promoter are hypermethylated. Interestingly, several other X-linked genes associated with glycosylation are not silenced in Tn4 cells, and we observed no correlation of a particular DNA methyltransferase to aberrant methylation of Cosmc in these cells. Thus, hypermethylation of the Cosmc promoter in Tn4 cells is relatively specific. Epigenetic silencing of Cosmc provides another mechanism underlying the abnormal expression of the Tn antigen, which may be important in understanding aberrant Tn antigen expression in human diseases, including IgA nephropathy and cancer.
Collapse
Affiliation(s)
- Rongjuan Mi
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|