<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase

ABSTRACT Blastomyces adhesin-1 (BAD-1) protein mediates the virulence of the yeast Blastomyces dermatitidis, in part by binding host lung tissue, the extracellular matrix, and cellular receptors via glycosaminoglycans (GAGs), such as heparan sulfate. The tandem repeats that make up over 90% of BAD-1...

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Autores principales:	Audrey Beaussart, Tristan Brandhorst, Yves F. Dufrêne, Bruce S. Klein
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2015
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/6f7825444b0048adb6fe6a255b1c0ce0
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spelling	oai:doaj.org-article:6f7825444b0048adb6fe6a255b1c0ce02021-11-15T15:41:30Z<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase10.1128/mBio.01403-152150-7511https://doaj.org/article/6f7825444b0048adb6fe6a255b1c0ce02015-10-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01403-15https://doaj.org/toc/2150-7511ABSTRACT Blastomyces adhesin-1 (BAD-1) protein mediates the virulence of the yeast Blastomyces dermatitidis, in part by binding host lung tissue, the extracellular matrix, and cellular receptors via glycosaminoglycans (GAGs), such as heparan sulfate. The tandem repeats that make up over 90% of BAD-1 appear in their native state to be tightly folded into an inactive conformation, but recent work has shown that they become activated and adhesive upon reduction of a disulfide linkage. Here, atomic force microscopy (AFM) of a single BAD-1 molecule interacting with immobilized heparin revealed that binding is enhanced upon treatment with protein disulfide isomerase and dithiothreitol (PDI/DTT). PDI/DTT treatment of BAD-1 induced a plateau effect in atomic force signatures that was consistent with sequential rupture of tandem binding domains. Inhibition of PDI in murine macrophages blunted BAD-1 binding to heparin in vitro. Based on AFM, we found that a short Cardin-Weintraub sequence paired with a WxxWxxW sequence in the first, degenerate repeat at the N terminus of BAD-1 was sufficient to initiate heparin binding. Removal of half of the 41 BAD-1 tandem repeats led to weaker adhesion, illustrating their role in enhanced binding. Mass spectroscopy of the tandem repeat revealed that the PDI-induced interaction with heparin is characterized by ruptured disulfide bonds and that cysteine thiols remain reduced. Further binding studies showed direct involvement of thiols in heparin ligation. Thus, we propose that the N-terminal domain of BAD-1 governs the initial association with host GAGs and that proximity to GAG-associated host PDI catalyzes activation of additional binding motifs conserved within the tandem repeats, leading to enhanced avidity and availability of reduced thiols. IMPORTANCE Pathogenic fungi and other microbes must adhere to host tissue to initiate infection. Surface adhesins promote this event and may be required for disease pathogenesis. We studied a fungal adhesin essential for virulence (BAD-1; Blastomyces adhesin-1) and found that host products induce its structural reconfiguration and foster its optimal binding to tissue structures.Audrey BeaussartTristan BrandhorstYves F. DufrêneBruce S. KleinAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 6, Iss 5 (2015)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Audrey Beaussart Tristan Brandhorst Yves F. Dufrêne Bruce S. Klein <italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase
description	ABSTRACT Blastomyces adhesin-1 (BAD-1) protein mediates the virulence of the yeast Blastomyces dermatitidis, in part by binding host lung tissue, the extracellular matrix, and cellular receptors via glycosaminoglycans (GAGs), such as heparan sulfate. The tandem repeats that make up over 90% of BAD-1 appear in their native state to be tightly folded into an inactive conformation, but recent work has shown that they become activated and adhesive upon reduction of a disulfide linkage. Here, atomic force microscopy (AFM) of a single BAD-1 molecule interacting with immobilized heparin revealed that binding is enhanced upon treatment with protein disulfide isomerase and dithiothreitol (PDI/DTT). PDI/DTT treatment of BAD-1 induced a plateau effect in atomic force signatures that was consistent with sequential rupture of tandem binding domains. Inhibition of PDI in murine macrophages blunted BAD-1 binding to heparin in vitro. Based on AFM, we found that a short Cardin-Weintraub sequence paired with a WxxWxxW sequence in the first, degenerate repeat at the N terminus of BAD-1 was sufficient to initiate heparin binding. Removal of half of the 41 BAD-1 tandem repeats led to weaker adhesion, illustrating their role in enhanced binding. Mass spectroscopy of the tandem repeat revealed that the PDI-induced interaction with heparin is characterized by ruptured disulfide bonds and that cysteine thiols remain reduced. Further binding studies showed direct involvement of thiols in heparin ligation. Thus, we propose that the N-terminal domain of BAD-1 governs the initial association with host GAGs and that proximity to GAG-associated host PDI catalyzes activation of additional binding motifs conserved within the tandem repeats, leading to enhanced avidity and availability of reduced thiols. IMPORTANCE Pathogenic fungi and other microbes must adhere to host tissue to initiate infection. Surface adhesins promote this event and may be required for disease pathogenesis. We studied a fungal adhesin essential for virulence (BAD-1; Blastomyces adhesin-1) and found that host products induce its structural reconfiguration and foster its optimal binding to tissue structures.
format	article
author	Audrey Beaussart Tristan Brandhorst Yves F. Dufrêne Bruce S. Klein
author_facet	Audrey Beaussart Tristan Brandhorst Yves F. Dufrêne Bruce S. Klein
author_sort	Audrey Beaussart
title	<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase
title_short	<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase
title_full	<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase
title_fullStr	<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase
title_full_unstemmed	<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase
title_sort	<italic toggle="yes">blastomyces</italic> virulence adhesin-1 protein binding to glycosaminoglycans is enhanced by protein disulfide isomerase
publisher	American Society for Microbiology
publishDate	2015
url	https://doaj.org/article/6f7825444b0048adb6fe6a255b1c0ce0
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<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide Isomerase

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