Staphylococcus aureus vWF-binding protein triggers a strong interaction between clumping factor A and host vWF

Abstract

The Staphylococcus aureus cell wall-anchored adhesin ClfA binds to the very large blood circulating protein, von Willebrand factor (vWF) via vWF-binding protein (vWbp), a secreted protein that does not bind the cell wall covalently. Here we perform force spectroscopy studies on living bacteria to unravel the molecular mechanism of this interaction. We discover that the presence of all three binding partners leads to very high binding forces (2000 pN), largely outperforming other known ternary complexes involving adhesins. Strikingly, our experiments indicate that a direct interaction involving features of the dock, lock and latch mechanism must occur between ClfA and vWF to sustain the extreme tensile strength of the ternary complex. Our results support a previously undescribed mechanism whereby vWbp activates a direct, ultra-strong interaction between ClfA and vWF. This intriguing interaction represents a potential target for therapeutic interventions, including synthetic peptides inhibiting the ultra-strong interactions between ClfA and its ligands.

Non-Canonical Host Intracellular Niche Links to New Antimicrobial Resistance Mechanism

“…While the FnBP-Fn-α5β1 integrin pathway is historically recognized as the main internalization process, there are numerous "secondary" mechanisms between S. aureus virulence factors and host cell components that are involved in or mediate FnBP-independent cellular invasion by S. aureus. These mechanisms involve major staphylococcal proteins such as autolysin (Atl), α-hemolysin (HLA), clumping factor A (ClfA), clumping factor B (ClfB), iron-regulated surface determinant B (IsdB), lipoprotein-like lipoproteins (Lpls), serine-rich adhesin for platelets (SraP), and bacterial serine aspartate repeat-containing protein D (SdrD), whose variable interactions with host cell receptors are summarized in Table 3 [87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105]. Further entry pathways are summarized in Figure 3 [106][107][108][109][110][111][112][113][114][115].…”

Staphylococcus aureus adhesion to the host

“…For example, ClfA adheres to fibrinogen, 44 which is known to promote the formation of a fibrin(ogen) shield that protects the bacterium from host immune recognition and clearance 45 . During adhesion to blood vessel walls, the secreted von Willeebrand factor (vWF)‐binding protein (vWbp) activates the dock, lock, and latch mechanism between ClfA and the vWF circulating in the blood 27 . This ternary complex is resistant to tensile stress 27 .…”

“… 59 For example, secreted proteins comprise an extensive repertoire of adhesins that interact with host cell ligands 5 . These adhesins include coagulase (Coa), the extracellular adherence protein (Eap), extracellular fibrinogen–binding protein (Efb), extracellular matrix protein–binding protein (Emp), and the vWbp 5,27,59 . Some of these factors are important for disease progression; for example, Efb inhibits phagocytosis of S. aureus in a mouse peritonitis model, 60 and Eap inhibits neutrophil recruitment in an acute mouse model 61 .…”

“…Pathogens harness a multitude of virulence factors and mechanisms to colonize, infect, and ultimately cause damage to their hosts 24–26 . Key to pathogenesis is adhesion to the host; bacteria must adhere tightly to avoid clearance, including during fluid flow in the vasculature, mucociliary clearance, the shedding of skin cells, the excretion of feces and urine, and through the shedding of tears 8,27 . The proximity achieved through adhesion also allows for the delivery of toxins, access to nutrients, colonization, biofilm formation, and host cell invasion 1,8,28 .…”

AFM Identifies a Protein Complex Involved in Pathogen Adhesion Which Ruptures at Three Nanonewtons

“…The von Willebrand factor (vWF) is a mechanosensitive multimeric glycoprotein that is an essential component of the blood and of the endothelial basement membrane. Each mature vWF monomer exhibits a modular architecture with distinct domains dedicated to specific functions (Figure a). , From the N- to the C-terminus, A1 and A3 domains bind to constituents of the extracellular matrix of the subendothelium such as fibrillar collagens , and platelet glycoprotein Ibα (GpIb), − and the C4 domain contains an RGD motif that binds to the platelet integrin α IIb β 3 . Large multimers of vWF are stocked in endothelial cells, from which they are secreted into the blood .…”