1
|
Stewart TJ, Takahashi K, Xu N, Prakash A, Brown R, Raska M, Renfrow MB, Novak J. Quantitative assessment of successive carbohydrate additions to the clustered O-glycosylation sites of IgA1 by glycosyltransferases. Glycobiology 2020; 31:540-556. [PMID: 33295603 DOI: 10.1093/glycob/cwaa111] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 12/01/2020] [Accepted: 12/02/2020] [Indexed: 11/12/2022] Open
Abstract
Mucin-type O-glycosylation occurs on many proteins that transit the Golgi apparatus. These glycans impact structure and function of many proteins and have important roles in cellular biosynthetic processes, signaling and differentiation. Although recent technological advances have enhanced our ability to profile glycosylation of glycoproteins, limitations in the understanding of the biosynthesis of these glycan structures remain. Some of these limitations stem from the difficulty to track the biosynthetic process of mucin-type O-glycosylation, especially when glycans occur in dense clusters in repeat regions of proteins, such as the mucins or immunoglobulin A1 (IgA1). Here, we describe a series of nano-liquid chromatography (LC)-mass spectrometry (MS) analyses that demonstrate the range of glycosyltransferase enzymatic activities involved in the biosynthesis of clustered O-glycans on IgA1. By utilizing nano-LC-MS relative quantitation of in vitro reaction products, our results provide unique insights into the biosynthesis of clustered IgA1 O-glycans. We have developed a workflow to determine glycoform-specific apparent rates of a human UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltrasnfersase (GalNAc-T EC 2.4.1.41) and demonstrated how pre-existing glycans affect subsequent activity of glycosyltransferases, such as core 1 galactosyltransferase and α2,3- and α2,6-specific sialyltransferases, in successive additions in the biosynthesis of clustered O-glycans. In the context of IgA1, these results have potential to provide insight into the molecular mechanisms implicated in the pathogenesis of IgA nephropathy, an autoimmune renal disease involving aberrant IgA1 O-glycosylation. In a broader sense, these methods and workflows are applicable to the studies of the concerted and competing functions of other glycosyltransferases that initiate and extend mucin-type core 1 clustered O-glycosylation.
Collapse
Affiliation(s)
- Tyler J Stewart
- Department of Microbiology, University of Alabama at Birmingham, 845 19th Street South, BBRB 761A, Birmingham, AL 35294, USA.,Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 720 20th Street South, KAUL 524, Birmingham, AL 35294, USA
| | - Kazuo Takahashi
- Department of Biomedical Molecular Sciences, Fujita Health University School of Medicine, 1-98 Dengakugakubo, Kutsukake, Aichi, Toyoake 470-1192, Japan.,Department of Microbiology, University of Alabama at Birmingham, 845 19th Street South, BBRB 761A, Birmingham, AL 35294, USA
| | - Nuo Xu
- Department of Management, Information Systems & Quantitative Methods, 710 13th Street South, University of Alabama at Birmingham, Birmingham, AL 35233, USA
| | - Amol Prakash
- Optys Tech Corporation, Shrewsbury, MA 01545, USA
| | - Rhubell Brown
- Department of Microbiology, University of Alabama at Birmingham, 845 19th Street South, BBRB 761A, Birmingham, AL 35294, USA
| | - Milan Raska
- Department of Immunology, Palacky University and University Hospital, Hnevotinska 3, Olomouc 775 15, Czech Republic
| | - Matthew B Renfrow
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 720 20th Street South, KAUL 524, Birmingham, AL 35294, USA
| | - Jan Novak
- Department of Microbiology, University of Alabama at Birmingham, 845 19th Street South, BBRB 761A, Birmingham, AL 35294, USA
| |
Collapse
|
2
|
Stewart TJ, Takahashi K, Whitaker RH, Raska M, Placzek WJ, Novak J, Renfrow MB. IgA1 hinge-region clustered glycan fidelity is established early during semi-ordered glycosylation by GalNAc-T2. Glycobiology 2019; 29:543-556. [PMID: 30759204 PMCID: PMC6583770 DOI: 10.1093/glycob/cwz007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 01/13/2019] [Accepted: 02/04/2019] [Indexed: 01/03/2023] Open
Abstract
GalNAc-type O-glycans are often added to proteins post-translationally in a clustered manner in repeat regions of proteins, such as mucins and IgA1. Observed IgA1 glycosylation patterns show that glycans occur at similar sites with similar structures. It is not clear how the sites and number of glycans added to IgA1, or other proteins, can follow a conservative process. GalNAc-transferases initiate GalNAc-type glycosylation. In IgA nephropathy, an autoimmune disease, the sites and O-glycan structures of IgA1 hinge-region are altered, giving rise to a glycan autoantigen. To better understand how GalNAc-transferases determine sites and densities of clustered O-glycans, we used IgA1 hinge-region (HR) segment as a probe. Using LC-MS, we demonstrated a semi-ordered process of glycosylation by GalNAc-T2 towards the IgA1 HR. The catalytic domain was responsible for selection of four initial sites based on amino-acid sequence recognition. Both catalytic and lectin domains were involved in multiple second site-selections, each dependent on initial site-selection. Our data demonstrated that multiple start-sites and follow-up pathways were key to increasing the number of glycans added. The lectin domain predominately enhanced IgA1 HR glycan density by increasing synthesis pathway exploration by GalNAc-T2. Our data indicated a link between site-specific glycan addition and clustered glycan density that defines a mechanism of how conserved clustered O-glycosylation patterns and glycoform populations of IgA1 can be controlled by GalNAc-T2. Together, these findings characterized a correlation between glycosylation pathway diversity and glycosylation density, revealing mechanisms by which a single GalNAc-T isozyme can limit and define glycan heterogeneity in a disease-relevant context.
Collapse
Affiliation(s)
- Tyler J Stewart
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Kazuo Takahashi
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Nephrology, Fujita Health University, Toyoake, Japan
| | - Robert H Whitaker
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Milan Raska
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Immunology, Palacky University and University Hospital, Olomouc, Czech Republic
| | - William J Placzek
- Department of Biochemistry and Molecular Genetics, 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
|
3
|
Revoredo L, Wang S, Bennett EP, Clausen H, Moremen KW, Jarvis DL, Ten Hagen KG, Tabak LA, Gerken TA. Mucin-type O-glycosylation is controlled by short- and long-range glycopeptide substrate recognition that varies among members of the polypeptide GalNAc transferase family. Glycobiology 2015; 26:360-76. [PMID: 26610890 DOI: 10.1093/glycob/cwv108] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 11/16/2015] [Indexed: 01/02/2023] Open
Abstract
A large family of UDP-GalNAc:polypeptide GalNAc transferases (ppGalNAc-Ts) initiates and defines sites of mucin-type Ser/Thr-O-GalNAc glycosylation. Family members have been classified into peptide- and glycopeptide-preferring subfamilies, although both families possess variable activities against glycopeptide substrates. All but one isoform contains a C-terminal carbohydrate-binding lectin domain whose roles in modulating glycopeptide specificity is just being understood. We have previously shown for several peptide-preferring isoforms that the presence of a remote Thr-O-GalNAc, 6-17 residues from a Ser/Thr acceptor site, may enhance overall catalytic activity in an N- or C-terminal direction. This enhancement varies with isoform and is attributed to Thr-O-GalNAc interactions at the lectin domain. We now report on the glycopeptide substrate utilization of a series of glycopeptide (human-ppGalNAc-T4, T7, T10, T12 and fly PGANT7) and peptide-preferring transferases (T2, T3 and T5) by exploiting a series of random glycopeptide substrates designed to probe the functions of their catalytic and lectin domains. Glycosylation was observed at the -3, -1 and +1 residues relative to a neighboring Thr-O-GalNAc, depending on isoform, which we attribute to specific Thr-O-GalNAc binding at the catalytic domain. Additionally, these glycopeptide-preferring isoforms show remote lectin domain-assisted Thr-O-GalNAc enhancements that vary from modest to none. We conclude that the glycopeptide specificity of the glycopeptide-preferring isoforms predominantly resides in their catalytic domain but may be further modulated by remote lectin domain interactions. These studies further demonstrate that both domains of the ppGalNAc-Ts have specialized and unique functions that work in concert to control and order mucin-type O-glycosylation.
Collapse
Affiliation(s)
| | - Shengjun Wang
- Copenhagen Center for Glycomics (CCG), Departments of Cellular and Molecular Medicine and Dentistry, Faculty of Health Sciences, University of Copenhagen, Copenhagen N DK-2200, Denmark
| | - Eric Paul Bennett
- Copenhagen Center for Glycomics (CCG), Departments of Cellular and Molecular Medicine and Dentistry, Faculty of Health Sciences, University of Copenhagen, Copenhagen N DK-2200, Denmark
| | - Henrik Clausen
- Copenhagen Center for Glycomics (CCG), Departments of Cellular and Molecular Medicine and Dentistry, Faculty of Health Sciences, University of Copenhagen, Copenhagen N DK-2200, Denmark
| | - Kelley W Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA
| | - Donald L Jarvis
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
| | | | - Lawrence A Tabak
- Section on Biological Chemistry, Department of Health and Human Services, NIDCR, National Institutes of Health, Bethesda, MD 20892, USA
| | - Thomas A Gerken
- Department of Chemistry Department of Pediatrics and Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA
| |
Collapse
|
4
|
Neves AA, Stöckmann H, Wainman YA, Kuo JCH, Fawcett S, Leeper FJ, Brindle KM. Imaging cell surface glycosylation in vivo using "double click" chemistry. Bioconjug Chem 2013; 24:934-41. [PMID: 23642228 PMCID: PMC3687584 DOI: 10.1021/bc300621n] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
Dynamic alterations in cell surface
glycosylation occur in numerous
biological processes that involve cell–cell communication and
cell migration. We report here imaging of cell surface glycosylation
in live mice using double click chemistry. Cell surface glycans were
metabolically labeled using peracetylated azido-labeled N-acetylgalactosamine and then reacted, in the first click reaction,
with either a cyclooctyne, in a Huisgen [3 + 2] cycloaddition, or
with a Staudinger phosphine, via Staudinger ligation. The second click
reaction was a [4 + 2] inverse electron demand Diels–Alder
reaction between a trans-cyclooctene and a tetrazine,
where the latter reagent had been fluorescently labeled with a far-red
fluorophore. After administration of the fluorescent tetrazine, the
bifunctional cyclooctyne-cyclooctene produced significant azido sugar-dependent
fluorescence labeling of tumor, kidney, liver, spleen, and small intestine
in vivo, where the kidney and tumor could be imaged noninvasively
in the live mouse.
Collapse
Affiliation(s)
- André A Neves
- Cancer Research U.K., Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK
| | | | | | | | | | | | | |
Collapse
|
5
|
Brockhausen I, Dowler T, Paulsen H. Site directed processing: role of amino acid sequences and glycosylation of acceptor glycopeptides in the assembly of extended mucin type O-glycan core 2. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1790:1244-57. [PMID: 19524017 DOI: 10.1016/j.bbagen.2009.05.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 05/21/2009] [Accepted: 05/29/2009] [Indexed: 12/15/2022]
Abstract
BACKGROUND The assembly of Ser/Thr-linked O-glycans of mucins with core 2 structures is initiated by polypeptide GalNAc-transferase (ppGalNAc-T), followed by the action of core 1 beta3-Gal-transferase (C1GalT) and core 2 beta6-GlcNAc-transferase (C2GnT). Beta4-Gal-transferase (beta4GalT) extends core 2 and forms the backbone structure for biologically important epitopes. O-glycan structures are often abnormal in chronic diseases. The goal of this work is to determine if the activity and specificity of these enzymes are directed by the sequences and glycosylation of substrates. METHODS We studied the specificities of four enzymes that synthesize extended O-glycan core 2 using as acceptor substrates synthetic mucin derived peptides and glycopeptides, substituted with GalNAc or O-glycan core structures 1, 2, 3, 4 and 6. RESULTS Specific Thr residues were found to be preferred sites for the addition of GalNAc, and Pro in the +3 position was found to especially enhance primary glycosylation. An inverse relationship was found between the size of adjacent glycans and the rate of GalNAc addition. All four enzymes could distinguish between substrates having different amino acid sequences and O-glycosylated sites. A short glycopeptide Galbeta1-3GalNAcalpha-TAGV was identified as an efficient C2GnT substrate. CONCLUSIONS The activities of four enzymes assembling the extended core 2 structure are affected by the amino acid sequence and presence of carbohydrates on nearby residues in acceptor glycopeptides. In particular, the sequences and O-glycosylation patterns direct the addition of the first and second sugar residues by ppGalNAc-T and C1GalT which act in a site directed fashion. GENERAL SIGNIFICANCE Knowledge of site directed processing enhances our understanding of the control of O-glycosylation in normal cells and in disease.
Collapse
Affiliation(s)
- Inka Brockhausen
- Department of Medicine, Division of Rheumatology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
| | | | | |
Collapse
|
6
|
Kanoh A, Takeuchi H, Kato K, Waki M, Usami K, Irimura T. Interleukin-4 induces specific pp-GalNAc-T expression and alterations in mucin O-glycosylation in colonic epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1780:577-84. [PMID: 17916404 DOI: 10.1016/j.bbagen.2007.08.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 08/10/2007] [Indexed: 10/22/2022]
Abstract
Mucus hypersecretion occurs as a consequence of the Th2 immune response in epithelia, yet it was not previously known whether the degree of O-glycosylation was modulated under such conditions. A colonic carcinoma cell line LS174T was used to assess the effect of interleukin (IL)-4 on the mRNA levels of eight pp-GalNAc-Ts. A three- to four-fold increase in pp-GalNAc-T1, T4, and T7 levels was observed. Lysates of untreated or IL-4-treated cells were examined for their ability to transfer GalNAc residues onto a peptide corresponding to the tandem repeat portion of human MUC2. The number of incorporated GalNAc residues was greater after incubation with lysates of IL-4-treated cells than with lysates of untreated cells. Mucin-like large glycoproteins secreted by IL-4-treated cells had higher binding capacity to PNA and VVA-B(4) than those secreted by untreated cells. The results indicated that IL-4-treated LS174T cells are able to produce mucins with a higher degree of O-glycosylation than untreated counterparts.
Collapse
Affiliation(s)
- Akira Kanoh
- Laboratory of Cancer Biology and Molecular Immunology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | | | | | | | | | | |
Collapse
|
7
|
Hang HC, Bertozzi CR. The chemistry and biology of mucin-type O-linked glycosylation. Bioorg Med Chem 2005; 13:5021-34. [PMID: 16005634 DOI: 10.1016/j.bmc.2005.04.085] [Citation(s) in RCA: 203] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2005] [Accepted: 04/26/2005] [Indexed: 02/04/2023]
Abstract
Mucin-type O-linked glycosylation is a fundamental post-translational modification that is involved in a variety of important biological processes. However, the lack of chemical tools to study mucin-type O-linked glycosylation has hindered our molecular understanding of O-linked glycans in many biological contexts. The review discusses the significance of mucin-type O-linked glycosylation initiated by the polypeptide N-acetylgalactosaminyltransferases in biology and development of chemical tools to study these enzymes and their substrates.
Collapse
Affiliation(s)
- Howard C Hang
- Department of Chemistry, University of California, Berkeley 94720-1460, USA.
| | | |
Collapse
|
8
|
Bandaletova T, Bailey N, Bingham SA, Loktionov A. Isolation of exfoliated colonocytes from human stool as a new technique for colonic cytology. APMIS 2002; 110:239-46. [PMID: 12076277 DOI: 10.1034/j.1600-0463.2002.100306.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Cell exfoliation in the gut is an important cell renewal mechanism. To approach its investigation we applied a novel immunomagnetic technique for isolation of exfoliated cells from human stool. Exfoliated colonocytes were isolated from 168 stool samples. The cells were assessed microscopically using conventional stains and immunohistochemistry. The technique allowed us to obtain well-preserved colonocytes displaying characteristic features of well-differentiated colonic epithelium and positive immunostaining for cytokeratin 5/8. No mucin-producing cells were found. Exfoliated cells did not produce inducible nitric oxide synthase, albeit cultured colon carcinoma cells HT-29 analysed in parallel showed strong immunostaining. Analysis of exfoliated cell numbers in consecutive stool samples from the same subjects revealed considerable interindividual variation. Overall exfoliated colonocyte numbers were relatively low, isolation being unaffected by addition during the procedure of excessive amounts of HT-29 cells. Apoptosis was extremely rare among exfoliated colonocytes. Well-preserved exfoliated colonocytes can be consistently isolated from human faeces using a simple procedure. Our findings suggest that the actual process of cell exfoliation in the human colon may be much less intense than is generally accepted. Exfoliated cell isolation from human stool constitutes a convenient non-invasive approach that can be used for diagnostic and research purposes.
Collapse
|
9
|
Kakehi K, Oda Y, Kinoshita M. Fluorescence polarization: analysis of carbohydrate-protein interaction. Anal Biochem 2001; 297:111-6. [PMID: 11673876 DOI: 10.1006/abio.2001.5309] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fluorescence polarization has been widely used for the studies on the molecular motion in solution and has been applied to immunoassays for proteins, therapeutic drug monitoring in clinical pharmacy, and assays for environmentally toxic compounds. Because fluorescence polarization is most readily applicable to the kinetic analysis of the binding reaction between a substance having small molecular mass and a receptor molecule, this method is easily applied to the analysis of carbohydrate-lectin binding. In this tutorial Thematic Review, we briefly introduce the principles of fluorescence polarization and some applications of fluorescence polarization technique to glycobiology.
Collapse
Affiliation(s)
- K Kakehi
- Faculty of Pharmaceutical Sciences, Kinki University, Kowakae 3-4-1, Higashi-Osaka, 577, Japan.
| | | | | |
Collapse
|
10
|
Kato K, Takeuchi H, Kanoh A, Mandel U, Hassan H, Clausen H, Irimura T. N-acetylgalactosamine incorporation into a peptide containing consecutive threonine residues by UDP-N-acetyl-D-galactosaminide:polypeptide N-acetylgalactosaminyltransferases. Glycobiology 2001; 11:821-9. [PMID: 11588158 DOI: 10.1093/glycob/11.10.821] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A limited number of glycosylation products were generated in a cell-free system from a portion of the MUC2 tandem repeat, PTTTPITTTTK, when microsome fractions of human colon carcinoma LS174T cells were used as the source of UDP-N-acetyl-D-galactosaminide:polypeptide N-acetylgalactosaminyltransferases (pp-GalNAc-T) in our previous work. The structures of all products suggested that there were only two biosynthetic pathways in the GalNAc incorporation into this peptide. In the present report, the putative biosynthetic intermediates, PTTT*PITTTTK (asterisk designates a GalNAc residue), PT*TTPITTTTK, PTT*T*PITT*T*TK, and PT*TTPIT*T*T*TK, of these two hypothetical pathways were used as acceptors to prove that these two pathways do exist. The incubation products of these glycopeptides, microsome fractions of LS174T cells, and UDP-GalNAc were fractionated by reverse-phase HPLC and their structures were determined using MALDI-TOF MS and peptide sequencing. The products from PTTT*PITTTTK were PTTT*PITTT*TK, PTTT*PITT*T*TK, PTT*T*PI-TT*T*TK, PTT*T*PIT*T*T*TK, PT*T*T*PIT*T*T*TK, and PT*T*T*PIT*T*T*T*K. The products from PTT*-T*PITT*T*TK exactly corresponded to the products with five to seven GalNAc residues from PTTT*PITTTTK. The products from PT*TTPITTTTK were PT*TTPITT*TTK, PT*TTPIT*T*TTK, and PT*TTPIT*T*T*TK. PT*TTP-IT*T*T*TK was not converted further under the applied condition. All the products detected and analyzed were the same as those obtained when the unsubstituted peptide and microsome fractions of LS174T cells were incubated. Immunocytochemical analysis indicated that LS174T cells contain at least four pp-GalNAc-Ts (-T1, -T2, -T3, and -T4), suggesting that control of the order and the maximum number of GalNAc incorporation into this peptide is regulated through the coordinated actions of these and possibly other pp-GalNAc-Ts.
Collapse
Affiliation(s)
- K Kato
- Laboratory of Cancer Biology and Molecular Immunology, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | | | | | | | | | | | | |
Collapse
|
11
|
Kato K, Takeuchi H, Miyahara N, Kanoh A, Hassan H, Clausen H, Irimura T. Distinct orders of GalNAc incorporation into a peptide with consecutive threonines. Biochem Biophys Res Commun 2001; 287:110-5. [PMID: 11549261 DOI: 10.1006/bbrc.2001.5562] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mucin O-glycosylation is initiated by a transfer of N-acetyl-d-galactosamine (GalNAc) to Ser and Thr residues in polypeptides with a family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (pp-GalNAc-Ts). In this paper, four human pp-GalNAc-Ts (pp-GalNAc-T1, T2, T3, and T4) were tested for their preferential orders of GalNAc incorporation into FITC-PTTTPITTTTK, a portion of the tandem repeat of human MUC2. The products were separated by reverse-phase HPLC and characterized by MALDI-TOF MS and peptide sequencing. pp-GalNAc-T1 showed preference for acceptor sites, but the order of the incorporation into these sites seemed to be random. In contrast, the GalNAc incorporation by pp-GalNAc-T2, T3, or T4 was not only site-specific but also according to the specific orders. Furthermore, pp-GalNAc-T2, T3, or T4 had distinct maximum numbers of GalNAc incorporations into this peptide.
Collapse
Affiliation(s)
- K Kato
- Laboratory of Cancer Biology and Molecular Immunology, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | | | | | | | | | | | | |
Collapse
|
12
|
Abstract
Many carcinoma-associated markers are glycoconjugates whose expression undergoes temporal or spatial regulation. Mucin-1 (MUC1), discovered through monoclonal antibody technology, is a well-documented example of such a molecule and influences numerous pathophysiological behaviors, such as the invasion and metastasis of carcinoma cells. Levels of MUC1 expression in carcinomas correlate with the clinical stage of the cancer and inversely correlate with the survival prospects of patients. The MUC1 immune response is known to provide a protective host defense mechanism against cancer. The multiple functions of MUC1 in carcinoma-host interactions are believed to be dependent on the polymorphic nature of MUC1, particularly its glycosylation status.
Collapse
Affiliation(s)
- K Denda-Nagai
- Laboratory of Cancer Biology and Molecular Immunology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Japan
| | | |
Collapse
|