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- Asmat, Tauseef M, et al.
(författare)
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Endocytosis of Streptococcus pneumoniae via the polymeric immunoglobulin receptor of epithelial cells relies on clathrin and caveolin dependent mechanisms.
- 2014
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Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1618-0607 .- 1438-4221. ; 304:8, s. 1233-1246
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Tidskriftsartikel (refereegranskat)abstract
- Colonization of Streptococcus pneumoniae (pneumococci) is a prerequisite for bacterial dissemination and their capability to enter the bloodstream. Pneumococci have evolved various successful strategies to colonize the mucosal epithelial barrier of humans. A pivotal mechanism of host cell invasion implicated with invasive diseases is promoted by the interaction of pneumococcal PspC with the polymeric Ig-receptor (pIgR). However, the mechanism(s) of pneumococcal endocytosis and the intracellular route of pneumococci upon uptake by the PspC-pIgR-interaction are not known. Here, we demonstrate by using a combination of pharmacological inhibitors and genetics interference approaches the involvement of active dynamin-dependent caveolae and clathrin-coated vesicles for pneumococcal uptake via the PspC-pIgR mechanism. Depleting cholesterol from host cell membranes and disruption of lipid microdomains impaired pneumococcal internalization. Moreover, chemical inhibition of clathrin or functional inactivation of dynamin, caveolae or clathrin by RNA interference significantly affected pneumococcal internalization suggesting that clathrin-mediated endocytosis (CME) and caveolae are involved in the bacterial uptake process. Confocal fluorescence microscopy of pIgR-expressing epithelial cells infected with pneumococci or heterologous Lactococcus lactis expressing PspC demonstrated bacterial co-localization with fluorescent-tagged clathrin and early as well as recycling or late endosomal markers such as Lamp1, Rab5, Rab4, and Rab7, respectively. In conclusion these data suggest that PspC-promoted uptake is mediated by both CME and caveolae. After endocytosis pneumococci are routed via the endocytic pathway into early endosomes and are then sorted into recycling or late endosomes, which can result in pneumococcal killing in phagolysosomes or transcytosis via recycling endosomes.
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- Voss, Sylvia, et al.
(författare)
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The Choline-binding Protein PspC of Streptococcus pneumoniae Interacts with the C-terminal Heparin-binding Domain of Vitronectin
- 2013
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 288:22, s. 15614-15627
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Tidskriftsartikel (refereegranskat)abstract
- Adherence of Streptococcus pneumoniae is directly mediated by interactions of adhesins with eukaryotic cellular receptors or indirectly by exploiting matrix and serum proteins as molecular bridges. Pneumococci engage vitronectin, the human adhesive glycoprotein and complement inhibitor, to facilitate attachment to epithelial cells of the mucosal cavity, thereby modulating host cell signaling. In this study, we identified PspC as a vitronectin-binding protein interacting with the C-terminal heparin-binding domain of vitronectin. PspC is a multifunctional surface-exposed choline-binding protein displaying various adhesive properties. Vitronectin binding required the R domains in the mature PspC protein, which are also essential for the interaction with the ectodomain of the polymeric immunoglobulin receptor and secretory IgA. Consequently, secretory IgA competitively inhibited binding of vitronectin to purified PspC and to PspC-expressing pneumococci. In contrast, Factor H, which binds to the N-terminal part of mature PspC molecules, did not interfere with the PspC-vitronectin interaction. Using a series of vitronectin peptides, the C-terminal heparin-binding domain was shown to be essential for the interaction of soluble vitronectin with PspC. Binding experiments with immobilized vitronectin suggested a region N-terminal to the identified heparin-binding domain as an additional binding region for PspC, suggesting that soluble, immobilized, as well as cellularly bound vitronectin possesses different conformations. Finally, vitronectin bound to PspC was functionally active and inhibited the deposition of the terminal complement complex. In conclusion, this study identifies and characterizes (on the molecular level) the interaction between the pneumococcal adhesin PspC and the human glycoprotein vitronectin.
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