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Nejatie A, Steves E, Gauthier N, Baker J, Nesbitt J, McMahon SA, Oehler V, Thornton NJ, Noyovitz B, Khazaei K, Byers BW, Zandberg WF, Gloster TM, Moore MM, Bennet AJ. Kinetic and Structural Characterization of Sialidases (Kdnases) from Ascomycete Fungal Pathogens. ACS Chem Biol 2021; 16:2632-2640. [PMID: 34724608 DOI: 10.1021/acschembio.1c00666] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sialidases catalyze the release of sialic acid from the terminus of glycan chains. We previously characterized the sialidase from the opportunistic fungal pathogen, Aspergillus fumigatus, and showed that it is a Kdnase. That is, this enzyme prefers 3-deoxy-d-glycero-d-galacto-non-2-ulosonates (Kdn glycosides) as the substrate compared to N-acetylneuraminides (Neu5Ac). Here, we report characterization and crystal structures of putative sialidases from two other ascomycete fungal pathogens, Aspergillus terreus (AtS) and Trichophyton rubrum (TrS). Unlike A. fumigatus Kdnase (AfS), hydrolysis with the Neu5Ac substrates was negligible for TrS and AtS; thus, TrS and AtS are selective Kdnases. The second-order rate constant for hydrolysis of aryl Kdn glycosides by AtS is similar to that by AfS but 30-fold higher by TrS. The structures of these glycoside hydrolase family 33 (GH33) enzymes in complex with a range of ligands for both AtS and TrS show subtle changes in ring conformation that mimic the Michaelis complex, transition state, and covalent intermediate formed during catalysis. In addition, they can aid identification of important residues for distinguishing between Kdn and Neu5Ac substrates. When A. fumigatus, A. terreus, and T. rubrum were grown in chemically defined media, Kdn was detected in mycelial extracts, but Neu5Ac was only observed in A. terreus or T. rubrum extracts. The C8 monosaccharide 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) was also identified in A. fumigatus and T. rubrum samples. A fluorescent Kdn probe was synthesized and revealed the localization of AfS in vesicles at the cell surface.
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Affiliation(s)
- Ali Nejatie
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Elizabeth Steves
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Nick Gauthier
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Jamie Baker
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Jason Nesbitt
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Stephen A. McMahon
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Fife, U.K
| | - Verena Oehler
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Fife, U.K
| | - Nicholas J. Thornton
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Fife, U.K
| | - Benjamin Noyovitz
- Department of Chemistry, I. K. Barber Faculty of Science, University of British Columbia, 3247 University Way, Kelowna V1V 1V7, British Columbia, Canada
| | - Kobra Khazaei
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Brock W. Byers
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Wesley F. Zandberg
- Department of Chemistry, I. K. Barber Faculty of Science, University of British Columbia, 3247 University Way, Kelowna V1V 1V7, British Columbia, Canada
| | - Tracey M. Gloster
- Biomedical Sciences Research Complex, University of St Andrews, St Andrews KY16 9ST, Fife, U.K
| | - Margo M. Moore
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
| | - Andrew J. Bennet
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, British
Columbia, Canada
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Glycocalyx disruption enhances motility, proliferation and collagen synthesis in diabetic fibroblasts. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1868:118955. [PMID: 33421533 DOI: 10.1016/j.bbamcr.2021.118955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 12/24/2020] [Accepted: 01/04/2021] [Indexed: 11/22/2022]
Abstract
Impaired wound healing represents one of the most debilitating side effects of Diabetes mellitus. Though the role of fibroblasts in wound healing is well-known, the extent to which their function is altered in the context of diabetes remains incompletely understood. Here, we address this question by comparing the phenotypes of healthy dermal fibroblasts (HDFs) and diabetic dermal fibroblasts (DDFs). We show that DDFs are more elongated but less motile and less contractile than HDFs. Reduced motility of DDFs is attributed to formation of larger focal adhesions stabilized by a bulky glycocalyx, associated with increased expression of the cell surface glycoprotein mucin 16 (MUC 16). Disruption of the glycocalyx not only restored DDF motility to levels comparable to that of HDFs, but also led to increased proliferation and collagen synthesis. Collectively, our results illustrate the influence of glycocalyx disruption on mechanics of diabetic fibroblasts relevant to cell motility.
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Nejatie A, Akintola O, Steves E, Shamsi Kazem Abadi S, Moore MM, Bennet AJ. Structurally homologous sialidases exhibit a commonality in reactivity: Glycoside hydrolase-catalyzed hydrolysis of Kdn-thioglycosides. Bioorg Chem 2020; 106:104484. [PMID: 33268005 DOI: 10.1016/j.bioorg.2020.104484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 10/19/2020] [Accepted: 11/16/2020] [Indexed: 10/23/2022]
Abstract
Aspergillus fumigatus is one of the main causative agents of invasive aspergillosis, an often-lethal fungal disease that affects immunocompromised individuals. A. fumigatus produces a sialidase that cleaves the nine-carbon carbohydrate Kdn from glycoconjugates. This enzyme plays a critical role in A. fumigatus pathogenicity, and is thus a target for the development of new therapeutics. In order to understand the reactivity of this Kdnase, and to develop a sensitive and selective assay for its catalytic activity we determined whether, like its close structural homolog the excreted sialidase produced by Micromonospora viridifaciens, this enzyme can efficiently hydrolyze thioglycoside substrates. We synthesized a panel of seven aryl 2-thio-d-glycero-α-d-galacto-non-2-ulopyranosonides and measured the activity of the A. fumigatus Kdnase towards these substrates. Four of these substrates were hydrolyzed by the A. fumigatus enzyme, although M. viridifaciens sialidase-catalyzed the hydrolysis of these Kdn thioglycosides with higher catalytic efficiencies (kcat/Km). We also tested an enzyme that was evolved from MvNA to improve its activity against Kdn glycosides (Glycobiology 2020, 30, 325). All three enzymes catalyzed the hydrolysis of the four most reactive Kdn thioglycosides and their second-order rate constants (kcat/Km) display a concave downwards Brønsted plot. The kinetic data, for each enzyme, is consistent with a change in rate-limiting step from CS bond cleavage for thioglycosides in which the pKa of the corresponding aryl thiol is >3.6, to a non-chemical step, which is likely a conformational change, that occurs prior to CS bond cleavage for the 2,3,4,5,6-pentafluorothiophenyl glycoside.
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Affiliation(s)
- Ali Nejatie
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Oluwafemi Akintola
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Elizabeth Steves
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Saeideh Shamsi Kazem Abadi
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Margo M Moore
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Andrew J Bennet
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada.
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