Abstract
The choline-binding protein PspC of Streptococcus pneumoniae interacts with the C-terminal heparin-binding domain of vitronectin
Highlights
Adhesins are essential for pneumococcal colonization and pathogenesis
Vitronectin Binds to Intact Pneumococci—S. pneumoniae were previously shown to recruit multimeric vitronectin [4]. These results were confirmed by flow cytometric analysis, which revealed a dose-dependent binding of vitronectin to the pneumococcal surface (Fig. 1A and supplemental Fig. S1A)
Pneumococci exploit vitronectin as a molecular bridge to access ␣v3integrin receptors, which results in an activation of the PI3KAkt signaling pathway via the integrin-linked kinase, induces rearrangements of the host cell actin cytoskeleton, and enhances pneumococcal internalization
Summary
Results: PspC, identified as a vitronectin-binding protein, interacts with the C-terminal heparin-binding domain of vitronectin, and when bound to PspC, it retains complement inhibitory function. Pneumococci express an armamentarium of surface-exposed adhesins These adhesins interact with host cellular receptors directly or indirectly by targeting extracellular matrix or acquiring human serum proteins, thereby linking pneumococci to eukaryotic cell receptors or professional phagocytes [2,3,4,5,6,7,8]. The interaction sites were mapped to a 121-amino acid sequence in the N-terminal part of the PspC protein and to the short consensus repeats 8 –11 and short consensus repeats 19 –20 of Factor H [2, 30] This interplay enables pneumococci to effectively evade the host immune attack and to control complement effector functions by inhibiting the C3 convertase activity of the alternative pathway [31]. In addition to four hemopexin-type repeats, vitronectin consists of three heparin-binding domains (HBDs), of which the most C-terminal one mediates binding to proteoglycans and is
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