Integrin-linked kinase is required for vitronectin-mediated internalization ofStreptococcus pneumoniaeby host cells

Abstract

By interacting with components of the human host, including extracellular matrix (ECM) proteins, Streptococcus pneumoniae has evolved various strategies for colonization. Here, we characterized the interaction of pneumococci with the adhesive glycoprotein vitronectin and the contribution of this protein to pneumococcal uptake by host cells in an integrin-dependent manner. Specific interaction of S. pneumoniae with the heparin-binding sites of purified multimeric vitronectin was demonstrated by flow cytometry analysis. Host-cell-bound vitronectin promoted pneumococcal adherence to and invasion into human epithelial and endothelial cells. Pneumococci were trapped by microspike-like structures, which were induced upon contact of pneumococci with host-cell-bound vitronectin. αvβ3 integrin was identified as the major cellular receptor for vitronectin-mediated adherence and uptake of pneumococci. Ingestion of pneumococci by host cells via vitronectin required a dynamic actin cytoskeleton and was dependent on integrin-linked kinase (ILK), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt), as demonstrated by gene silencing or in inhibition experiments. In conclusion, pneumococci exploit the vitronectin–αvβ3-integrin complex as a cellular receptor for invasion and this integrin-mediated internalization requires the cooperation between the host signalling molecules ILK, PI3K and Akt.

Heterologous expression of pneumococcal virulence factor PspC on the surface of Lactococcus lactis confers adhesive properties

“…Pneumococcal adherence to host cells is, similar to other Gram-positive pathogens including Staphylococcus aureus and Streptococcus pyogenes, a multifactorial process. Attachment of S. pneumoniae to respiratory epithelial cells is mediated by serum or extracellular matrix proteins including complement Factor H, thrombospondin-1 and vitronectin (Agarwal et al, 2010b;Bergmann et al, 2009;Hammerschmidt et al, 2007;Rennemeier et al, 2007). In addition, pneumococci produce surface proteins interacting directly with host cellular receptors such as the choline-binding protein PspC (pneumococcal surface protein C, also referred to as CbpA or SpsA), RrgA of Pilus-1, PavB and PsrP (Barocchi et al, 2006;Elm et al, 2004;Jensch et al, 2010;Orihuela et al, 2004;Zhang et al, 2000).…”

The Choline-binding Protein PspC of Streptococcus pneumoniae Interacts with the C-terminal Heparin-binding Domain of Vitronectin

“…Therefore, 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). Adhesive properties are known for a number of pneumococcal surface proteins recognizing plasmin(ogen), fibronectin, thrombospondin-1, and vitronectin (8 -17).…”

Streptococcus pyogenes M49 Plasminogen/Plasmin Binding Facilitates Keratinocyte Invasion via Integrin-Integrin-linked Kinase (ILK) Pathways and Protects from Macrophage Killing

“…These are e.g. Streptococcus pneumoniae (37), Staphylococcus aureus (61), or Porphyromonas gingivalis (62).…”

“…The assay was performed in the presence of the inhibitors. As a control, the cells were preincubated with DMSO at the same concentrations and infected with the bacteria (37). All inhibition experiments were performed in DMEM without FBS supplementation.…”