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Stretching fibronectin fibres disrupts binding of bacterial adhesins by physically destroying an epitope.

Chabria M, Hertig S, Smith ML, Vogel V - Nat Commun (2010)

Bottom Line: Heparin reduces binding but does not eliminate mechanosensitivity.The mechanical switch described here operates differently from the catch bond mechanism that Escherichia coli uses to adhere to surfaces under fluid flow.Demonstrating the existence of a mechanosensitive cell-binding site provides a new perspective on how the mechanobiology of ECM might regulate bacterial and cell-binding events, virulence and the course of infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials, ETH Zurich, Zürich CH-8093, Switzerland.

ABSTRACT
Although soluble inhibitors are frequently used to block cell binding to the extracellular matrix (ECM), mechanical stretching of a protein fibre alone can physically destroy a cell-binding site. Here, we show using binding assays and steered molecular dynamics that mechanical tension along fibronectin (Fn) fibres causes a structural mismatch between Fn-binding proteins from Streptococcus dysgalactiae and Staphylococcus aureus. Both adhesins target a multimodular site on Fn that is switched to low affinity by stretching the intermodular distances on Fn. Heparin reduces binding but does not eliminate mechanosensitivity. These adhesins might thus preferentially bind to sites at which ECM fibres are cleaved, such as wounds or inflamed tissues. The mechanical switch described here operates differently from the catch bond mechanism that Escherichia coli uses to adhere to surfaces under fluid flow. Demonstrating the existence of a mechanosensitive cell-binding site provides a new perspective on how the mechanobiology of ECM might regulate bacterial and cell-binding events, virulence and the course of infection.

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Structural organization of Fn and the bacterial FnBP.(a) Schematic representation of the multimodular structure of Fn emphasizing specific binding sites for cells and matrix proteins. The Fn modules type I, II and III are represented as circles, hexagons and rectangles, respectively. (b) Domain organization of five FnBP from various bacteria, including the peptides used in this study: B3 from FnBB-4 of S. dysgalactiae and STAFF5 from FnBPA5 of S. aureus. (c) Sequence alignment of various FnBR binding to FnI1–5 from S. pyogenes and S. dysgalactiae (alignment as shown in ref. 56). Grey regions indicate conserved residues; letters in green are the residues mainly involved in β-sheet interactions with the corresponding Fn modules; and the numbers correspond to the first and last residues. For site-specific photolabelling, the B3 moiety was synthesized with an additional N-terminal cysteine (B3C). B3T, the truncated form of the B3 peptide, is part of the nuclear magnetic resonance structure that has been used for SMD simulations (PDB-code 1O9A). The sequence of peptide STAFF5C is given in the last line.
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f1: Structural organization of Fn and the bacterial FnBP.(a) Schematic representation of the multimodular structure of Fn emphasizing specific binding sites for cells and matrix proteins. The Fn modules type I, II and III are represented as circles, hexagons and rectangles, respectively. (b) Domain organization of five FnBP from various bacteria, including the peptides used in this study: B3 from FnBB-4 of S. dysgalactiae and STAFF5 from FnBPA5 of S. aureus. (c) Sequence alignment of various FnBR binding to FnI1–5 from S. pyogenes and S. dysgalactiae (alignment as shown in ref. 56). Grey regions indicate conserved residues; letters in green are the residues mainly involved in β-sheet interactions with the corresponding Fn modules; and the numbers correspond to the first and last residues. For site-specific photolabelling, the B3 moiety was synthesized with an additional N-terminal cysteine (B3C). B3T, the truncated form of the B3 peptide, is part of the nuclear magnetic resonance structure that has been used for SMD simulations (PDB-code 1O9A). The sequence of peptide STAFF5C is given in the last line.

Mentions: The multimodularity of Fn (Fig. 1a) allows spatial distribution of distinct recognition sites along the molecule, enabling diverse interactions such as with other ECM proteins, growth factors, and prokaryotic and eukaryotic cells11. Dimeric Fn contains more than 50 modules that belong to one of the three structural β-sheet motifs, FnI, FnII and FnIII12. To enhance specificity, the bacterial FnBP exploits the modular structure of Fn by simultaneously binding to several FnI modules that define the amino (N)-terminal 29 KDa region1314 (Fig. 1b). The bacterial FnBP aligns antiparallel with up to five FnI modules and undergoes a disordered–ordered transition upon binding to form a tandem β-zipper15. A comparison of FnBP across different classes of bacteria shows that the bacterial Fn-binding repeats (FnBR) are each made up of 35–40 residues that form the primary binding site to Fn, but the number of FnBR varies considerably across species, containing just one for Borrelia burgdorferi16 and 11 for Staphylococcus aureus17 (Fig. 1b). The significance of this variation in relation to the specific modes of host adhesion and invasion is not known.


Stretching fibronectin fibres disrupts binding of bacterial adhesins by physically destroying an epitope.

Chabria M, Hertig S, Smith ML, Vogel V - Nat Commun (2010)

Structural organization of Fn and the bacterial FnBP.(a) Schematic representation of the multimodular structure of Fn emphasizing specific binding sites for cells and matrix proteins. The Fn modules type I, II and III are represented as circles, hexagons and rectangles, respectively. (b) Domain organization of five FnBP from various bacteria, including the peptides used in this study: B3 from FnBB-4 of S. dysgalactiae and STAFF5 from FnBPA5 of S. aureus. (c) Sequence alignment of various FnBR binding to FnI1–5 from S. pyogenes and S. dysgalactiae (alignment as shown in ref. 56). Grey regions indicate conserved residues; letters in green are the residues mainly involved in β-sheet interactions with the corresponding Fn modules; and the numbers correspond to the first and last residues. For site-specific photolabelling, the B3 moiety was synthesized with an additional N-terminal cysteine (B3C). B3T, the truncated form of the B3 peptide, is part of the nuclear magnetic resonance structure that has been used for SMD simulations (PDB-code 1O9A). The sequence of peptide STAFF5C is given in the last line.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3105298&req=5

f1: Structural organization of Fn and the bacterial FnBP.(a) Schematic representation of the multimodular structure of Fn emphasizing specific binding sites for cells and matrix proteins. The Fn modules type I, II and III are represented as circles, hexagons and rectangles, respectively. (b) Domain organization of five FnBP from various bacteria, including the peptides used in this study: B3 from FnBB-4 of S. dysgalactiae and STAFF5 from FnBPA5 of S. aureus. (c) Sequence alignment of various FnBR binding to FnI1–5 from S. pyogenes and S. dysgalactiae (alignment as shown in ref. 56). Grey regions indicate conserved residues; letters in green are the residues mainly involved in β-sheet interactions with the corresponding Fn modules; and the numbers correspond to the first and last residues. For site-specific photolabelling, the B3 moiety was synthesized with an additional N-terminal cysteine (B3C). B3T, the truncated form of the B3 peptide, is part of the nuclear magnetic resonance structure that has been used for SMD simulations (PDB-code 1O9A). The sequence of peptide STAFF5C is given in the last line.
Mentions: The multimodularity of Fn (Fig. 1a) allows spatial distribution of distinct recognition sites along the molecule, enabling diverse interactions such as with other ECM proteins, growth factors, and prokaryotic and eukaryotic cells11. Dimeric Fn contains more than 50 modules that belong to one of the three structural β-sheet motifs, FnI, FnII and FnIII12. To enhance specificity, the bacterial FnBP exploits the modular structure of Fn by simultaneously binding to several FnI modules that define the amino (N)-terminal 29 KDa region1314 (Fig. 1b). The bacterial FnBP aligns antiparallel with up to five FnI modules and undergoes a disordered–ordered transition upon binding to form a tandem β-zipper15. A comparison of FnBP across different classes of bacteria shows that the bacterial Fn-binding repeats (FnBR) are each made up of 35–40 residues that form the primary binding site to Fn, but the number of FnBR varies considerably across species, containing just one for Borrelia burgdorferi16 and 11 for Staphylococcus aureus17 (Fig. 1b). The significance of this variation in relation to the specific modes of host adhesion and invasion is not known.

Bottom Line: Heparin reduces binding but does not eliminate mechanosensitivity.The mechanical switch described here operates differently from the catch bond mechanism that Escherichia coli uses to adhere to surfaces under fluid flow.Demonstrating the existence of a mechanosensitive cell-binding site provides a new perspective on how the mechanobiology of ECM might regulate bacterial and cell-binding events, virulence and the course of infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials, ETH Zurich, Zürich CH-8093, Switzerland.

ABSTRACT
Although soluble inhibitors are frequently used to block cell binding to the extracellular matrix (ECM), mechanical stretching of a protein fibre alone can physically destroy a cell-binding site. Here, we show using binding assays and steered molecular dynamics that mechanical tension along fibronectin (Fn) fibres causes a structural mismatch between Fn-binding proteins from Streptococcus dysgalactiae and Staphylococcus aureus. Both adhesins target a multimodular site on Fn that is switched to low affinity by stretching the intermodular distances on Fn. Heparin reduces binding but does not eliminate mechanosensitivity. These adhesins might thus preferentially bind to sites at which ECM fibres are cleaved, such as wounds or inflamed tissues. The mechanical switch described here operates differently from the catch bond mechanism that Escherichia coli uses to adhere to surfaces under fluid flow. Demonstrating the existence of a mechanosensitive cell-binding site provides a new perspective on how the mechanobiology of ECM might regulate bacterial and cell-binding events, virulence and the course of infection.

Show MeSH
Related in: MedlinePlus