Inhibition of Aspergillus fumigatus conidia binding to extracellular matrix proteins by sialic acids: a pH effect?

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Title Inhibition of Aspergillus fumigatus conidia binding to extracellular matrix proteins by sialic acids: a pH effect?
Author Tiralongo, Giuseppe; Wohlschlager, Therese; Tiralongo, Evelin; Kiefel, Milton
Journal Name Microbiology
Year Published 2009
Place of publication UK
Publisher The Society for General Microbiology
Abstract Infection by Aspergillus fumigatus, which causes the life-threatening disease invasive aspergillosis, begins with the inhalation of conidia that adhere to and germinate in the lung. Previous studies have shown that A. fumigatus conidia express high levels of the negatively charged 9-carbon sugar sialic acid, and that sialic acid appears to mediate the binding of A. fumigatus conidia to basal lamina proteins. However, despite the ability of sialic acid to inhibit adherence of A. fumigatus conidia, the exact mechanism by which this binding occurs remains unresolved. Utilizing various free sialic acids and other carbohydrates, sialic acid derivatives, sialoglycoconjugates, glycoproteins, -keto acid related compounds and amino acids we have found that the binding of A. fumigatus conidia to type IV collagen and fibrinogen was inhibited by (i) glycoproteins (in a sialic acid-independent manner), and (ii) free sialic acids, glucuronic acid and -keto acid related compounds. However, inhibition by the latter was found to be the result of a shift in pH from neutral (pH 7.4) to acidic (less than pH 4.6) induced by the relatively high concentrations of free sialic acids, glucuronic acid and -keto acid related compounds used in the binding assays. This suggests that previous reports describing inhibition of A. fumigatus conidia binding by free sialic acid may actually be due to a pH shift similar to that shown here. As previously reported, we found that A. fumigatus conidia express only N-acetylneuraminic acid, the most common sialic acid found in nature. However, A. fumigatus appears to do so by an alternative mechanism to that seen in other organisms. We report here that A. fumigatus (i) does not incorporate sialic acid obtained from the environment, (ii) does not synthesize and incorporate sialic acid from exogenous N-acetylmannosamine, and (iii) lacks homologues of known sialic acid biosynthesizing enzymes.
Peer Reviewed Yes
Published Yes
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Copyright Statement Copyright 2009 Society for General Microbiology (SGM). This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal website for access to the definitive, published version.
Volume 155
Issue Number 9
Page from 3100
Page to 3109
ISSN 1350-0872
Date Accessioned 2010-02-22
Date Available 2010-09-01T08:06:59Z
Language en_AU
Research Centre Griffith Health Institute; Institute for Glycomics; Molecular Basis of Disease
Faculty Faculty of Science, Environment, Engineering and Technology
Subject Medical Biochemistry: Carbohydrates; Mycology
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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