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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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Guo X, Elkashef SM, Loadman PM, Patterson LH, Falconer RA. Recent advances in the analysis of polysialic acid from complex biological systems. Carbohydr Polym 2019; 224:115145. [PMID: 31472857 DOI: 10.1016/j.carbpol.2019.115145] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 07/26/2019] [Accepted: 07/29/2019] [Indexed: 12/25/2022]
Abstract
Polysialic acid (polySia) is a unique, well-characterised carbohydrate polymer highly-expressed on the cell surface of neurons in the early stages of mammalian brain development. Post-embryogenesis, it is also re-expressed in a number of tumours of neuroendocrine origin. It plays important roles in modulating cell-cell, and cell-matrix adhesion and migration, tumour invasion and metastasis. Techniques for structural and quantitative characterisation of polySia from tumours and cancer cells are thus essential in exploring the relationship between polySia expression levels and structural and functional changes associated with cancer progression and metastasis. A variety of techniques have been developed to structurally and quantitatively analyse polySia in clinical tissues and other biological samples. In this review, analytical approaches used for the determination of polySia in biological matrices in the past 20 years are discussed, with a particular focus on chemical approaches, and quantitative analysis.
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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
| | - 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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Noel M, Gilormini PA, Cogez V, Lion C, Biot C, Harduin-Lepers A, Guérardel Y. MicroPlate Sialyltransferase Assay: A Rapid and Sensitive Assay Based on an Unnatural Sialic Acid Donor and Bioorthogonal Chemistry. Bioconjug Chem 2018; 29:3377-3384. [PMID: 30192128 DOI: 10.1021/acs.bioconjchem.8b00529] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mammalian sialyltransferases transfer sialic acids onto glycoproteins and glycolipids within the Golgi apparatus. Despite their key role in glycosylation, the study of their enzymatic activities is limited by the lack of appropriate tools. Herein, we developed a quick and sensitive sialyltransferase microplate assay based on the use of the unnatural CMP-SiaNAl donor substrate. In this assay, an appropriate acceptor glycoprotein is coated on the bottom of 96-well plate and the sialyltransferase activity is assessed using CMP-SiaNAl. The alkyne tag of SiaNAl enables subsequent covalent ligation of an azido-biotin probe via CuAAC and an antibiotin-HRP conjugated antibody is then used to quantify the amount of transferred SiaNAl by a colorimetric titration. With this test, we evaluated the kinetic characteristics and substrate preferences of two human sialyltransferases, ST6Gal I and ST3Gal I toward a panel of asialoglycoprotein acceptors, and identified cations that display a sialyltransferase inhibitory effect.
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Affiliation(s)
- Maxence Noel
- Universite Lille , CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille , France
| | - Pierre-André Gilormini
- Universite Lille , CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille , France
| | - Virginie Cogez
- Universite Lille , CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille , France
| | - Cédric Lion
- Universite Lille , CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille , France
| | - Christophe Biot
- Universite Lille , CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille , France
| | - Anne Harduin-Lepers
- Universite Lille , CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille , France
| | - Yann Guérardel
- Universite Lille , CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, F 59000 Lille , France
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Chemical and biological methods for probing the structure and functions of polysialic acids. Emerg Top Life Sci 2018; 2:363-376. [DOI: 10.1042/etls20180008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 07/18/2018] [Accepted: 08/01/2018] [Indexed: 01/27/2023]
Abstract
Owing to its poly-anionic charge and large hydrodynamic volume, polysialic acid (polySia) attached to neural cell adhesion molecule regulates axon–axon and axon–substratum interactions and signalling, particularly, in the development of the central nervous system (CNS). Expression of polySia is spatiotemporally regulated by the action of two polysialyl transferases, namely ST8SiaII and ST8SiaIV. PolySia expression peaks during late embryonic and early post-natal period and maintained at a steady state in adulthood in neurogenic niche of the brain. Aberrant polySia expression is associated with neurological disorders and brain tumours. Investigations on the structure and functions, over the past four decades, have shed light on the physiology of polySia. This review focuses on the biological, biochemical, and chemical tools available for polySia engineering. Genetic knockouts, endo-neuraminidases that cleave polySia, antibodies, exogenous expression, and neuroblastoma cells have provided deep insights into the ability of polySia to guide migration of neuronal precursors in neonatal brain development, neuronal clustering, axonal pathway guidance, and axonal targeting. Advent of metabolic sialic acid engineering using ManNAc analogues has enabled reversible and dose-dependent modulation polySia in vitro and ex vivo. In vivo, ManNAc analogues readily engineer the sialoglycans in peripheral tissues, but show no effect in the brain. A recently developed carbohydrate-neuroactive hybrid strategy enables a non-invasive access to the brain in living animals across the blood–brain barrier. A combination of recent advances in CNS drugs and imaging with ManNAc analogues for polySia modulation would pave novel avenues for understanding intricacies of brain development and tackling the challenges of neurological disorders.
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