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Guo X, Elkashef SM, Patel A, Ribeiro Morais G, Shnyder SD, Loadman PM, Patterson LH, Falconer RA. An assay for quantitative analysis of polysialic acid expression in cancer cells. Carbohydr Polym 2021; 259:117741. [PMID: 33674001 DOI: 10.1016/j.carbpol.2021.117741] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/13/2021] [Accepted: 01/27/2021] [Indexed: 10/22/2022]
Abstract
Polysialic acid (polySia) is a linear polysaccharide comprised of N-acetylneuraminic acid residues and its over-expression in cancer cells has been correlated with poor clinical prognosis. An assay has been developed for quantitative analysis of cellular polySia expression. This was achieved by extracting and purifying released polySia from glycoproteins by mild acid hydrolysis and optimised organic extraction. The polySia was further hydrolysed into Sia monomers, followed by fluorescent labelling and quantitative analysis. The assay was qualified utilising endoneuraminidase-NF to remove polySia from the surface of C6-ST8SiaII cancer cells (EC50 = 2.13 ng/mL). The result was comparable to that obtained in a polySia-specific cellular ELISA assay. Furthermore, the assay proved suitable for evaluation of changes in polySia expression following treatment with a small molecule inhibitor of polysialylation. Given the importance of polySia in multiple disease states, notably cancer, this is a potentially vital tool with applications in the fields of drug discovery and glycobiology.
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Affiliation(s)
- Xiaoxiao Guo
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom
| | - Sara M Elkashef
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom
| | - Anjana Patel
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom
| | - Goreti Ribeiro Morais
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom
| | - Steven D Shnyder
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom
| | - Paul M Loadman
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom
| | - Laurence H Patterson
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom
| | - Robert A Falconer
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, BD7 1DP, United Kingdom.
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Guo X, Malcolm JR, Ali MM, Ribeiro Morais G, Shnyder SD, Loadman PM, Patterson LH, Falconer RA. An efficient assay for identification and quantitative evaluation of potential polysialyltransferase inhibitors. Analyst 2020; 145:4512-4521. [PMID: 32412559 DOI: 10.1039/d0an00721h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The polysialyltransferases (polySTs) catalyse the polymerisation of polysialic acid, which plays an important role in tumour metastasis. While assays are available to assess polyST enzyme activity, there is no methodology available specifically optimised for identification and quantitative evaluation of potential polyST inhibitors. The development of an HPLC-fluorescence-based enzyme assay described within includes a comprehensive investigation of assay conditions, including evaluation of metal ion composition, enzyme, substrate and acceptor concentrations, temperature, pH, and tolerance to DMSO, followed by validation using known polyST inhibitors. Thorough analysis of each of the assay components provided a set of optimised conditions. Under these optimised conditions, the experimentally observed Ki value for CMP, a competitive polyST inhibitor, was strongly correlated with the predicted Ki value, based on the classical Cheng-Prusoff equation [average fold error (AFE) = 1.043]. These results indicate that this assay can provide medium-throughput analysis for enzyme inhibitors with high accuracy, through determining the corresponding IC50 values with substrate concentration at the KM, without the need to perform extensive kinetic studies for each compound. In conclusion, an in vitro cell-free assay for accurate assessment of polyST inhibition is described. The utility of the assay for routine identification of potential polyST inhibitors is demonstrated, allowing quantitative measurement of inhibition to be achieved, and exemplified through assessment of full competitive inhibition. Given the considerable and growing interest in the polySTs as important anti-metastatic targets in cancer drug discovery, this is a vital tool to enable preclinical identification and evaluation of novel polyST inhibitors.
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Affiliation(s)
- Xiaoxiao Guo
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford BD7 1DP, UK.
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Janesch B, Baumann L, Mark A, Thompson N, Rahmani S, Sim L, Withers SG, Wakarchuk WW. Directed evolution of bacterial polysialyltransferases. Glycobiology 2020; 29:588-598. [PMID: 30976781 DOI: 10.1093/glycob/cwz021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 02/15/2019] [Accepted: 03/18/2019] [Indexed: 01/30/2023] Open
Abstract
Polysialyltransferases (polySTs) are glycosyltransferases that synthesize polymers of sialic acid found in vertebrates and some bacterial pathogens. Bacterial polySTs have utility in the modification of therapeutic proteins to improve serum half-life, and the potential for tissue engineering. PolySTs are membrane-associated proteins and as recombinant proteins suffer from inherently low solubility, low expression levels and poor thermal stability. To improve their physicochemical and biochemical properties, we applied a directed evolution approach using a FACS-based ultrahigh-throughput assay as a simple, robust and reliable screening method. We were able to enrich a large mutant library and, in combination with plate-based high-throughput secondary screening, we discovered mutants with increased enzymatic activity and improved stability compared to the wildtype enzyme. This work presents a powerful strategy for the screening of directed evolution libraries of bacterial polySTs to identify better catalysts for in vitro polysialylation of therapeutics.
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Affiliation(s)
- Bettina Janesch
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
| | - Lars Baumann
- Departments of Chemistry and Biochemistry, and Michael Smith Laboratory, University of British Columbia, Vancouver, BC, Canada
| | - Alison Mark
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
| | - Nicole Thompson
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
| | - Sadia Rahmani
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
| | - Lyann Sim
- Departments of Chemistry and Biochemistry, and Michael Smith Laboratory, University of British Columbia, Vancouver, BC, Canada
| | - Stephen G Withers
- Departments of Chemistry and Biochemistry, and Michael Smith Laboratory, University of British Columbia, Vancouver, BC, Canada
| | - Warren W Wakarchuk
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
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Ehrit J, Keys TG, Sutherland M, Wolf S, Meier C, Falconer RA, Gerardy-Schahn R. Exploring and Exploiting Acceptor Preferences of the Human Polysialyltransferases as a Basis for an Inhibitor Screen. Chembiochem 2017; 18:1332-1337. [PMID: 28472541 DOI: 10.1002/cbic.201700157] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Indexed: 12/18/2022]
Abstract
α2,8-Linked polysialic acid (polySia) is an oncofoetal antigen with high abundance during embryonic development. It reappears in malignant tumours of neuroendocrine origin. Two polysialyltransferases (polySTs) ST8SiaII and IV are responsible for polySia biosynthesis. During development, both enzymes are essential to control polySia expression. However, in tumours ST8SiaII is the prevalent enzyme. Consequently, ST8SiaII is an attractive target for novel cancer therapeutics. A major challenge is the high structural and functional conservation of ST8SiaII and -IV. An assay system that enables differential testing of ST8SiaII and -IV would be of high value to search for specific inhibitors. Here we exploited the different modes of acceptor recognition and elongation for this purpose. With DMB-DP3 and DMB-DP12 (fluorescently labelled sialic acid oligomers with a degree of polymerisation of 3 and 12, respectively) we identified stark differences between the two enzymes. The new acceptors enabled the simple comparative testing of the polyST initial transfer rate for a series of CMP-activated and N-substituted sialic acid derivatives. Of these derivatives, the non-transferable CMP-Neu5Cyclo was found to be a new, competitive ST8SiaII inhibitor.
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Affiliation(s)
- Jörg Ehrit
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Timothy G Keys
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Mark Sutherland
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, West Yorkshire, BD7 1DP, UK
| | - Saskia Wolf
- Department of Chemistry, Organic Chemistry, University Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany
| | - Chris Meier
- Department of Chemistry, Organic Chemistry, University Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany
| | - Robert A Falconer
- Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, West Yorkshire, BD7 1DP, UK
| | - Rita Gerardy-Schahn
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
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