<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...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2015-10-01
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| Series: | mBio |
| Online Access: | https://journals.asm.org/doi/10.1128/mBio.01403-15 |
| _version_ | 1818995596450594816 |
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| 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 |
| collection | DOAJ |
| 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. |
| first_indexed | 2024-12-20T21:16:21Z |
| format | Article |
| id | doaj.art-6f7825444b0048adb6fe6a255b1c0ce0 |
| institution | Directory Open Access Journal |
| issn | 2150-7511 |
| language | English |
| last_indexed | 2024-12-20T21:16:21Z |
| publishDate | 2015-10-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | mBio |
| spelling | doaj.art-6f7825444b0048adb6fe6a255b1c0ce02022-12-21T19:26:25ZengAmerican Society for MicrobiologymBio2150-75112015-10-016510.1128/mBio.01403-15<italic toggle="yes">Blastomyces</italic> Virulence Adhesin-1 Protein Binding to Glycosaminoglycans Is Enhanced by Protein Disulfide IsomeraseAudrey Beaussart0Tristan Brandhorst1Yves F. Dufrêne2Bruce S. Klein3Université catholique de Louvain, Institute of Life Sciences, Louvain-la-Neuve, BelgiumDepartment of Pediatrics, School of Medicine and Public Health, University of Wisconsin—Madison, Madison, Wisconsin, USAUniversité catholique de Louvain, Institute of Life Sciences, Louvain-la-Neuve, BelgiumDepartment of Pediatrics, School of Medicine and Public Health, University of Wisconsin—Madison, Madison, Wisconsin, USAABSTRACT 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.https://journals.asm.org/doi/10.1128/mBio.01403-15 |
| spellingShingle | 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 mBio |
| title | <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_short | <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 |
| url | https://journals.asm.org/doi/10.1128/mBio.01403-15 |
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