The novel chlamydial adhesin CPn0473 mediates the lipid raft‐dependent uptake ofChlamydia pneumoniae

Abstract

Summary Chlamydiae are Gram‐negative, obligate intracellular pathogens that pose a serious threat to public health worldwide. Chlamydial surface molecules are essential for host cell invasion. The first interaction with the host cell is thereby accomplished by the Outer membrane complex protein B (OmcB) binding to heparan sulfate moieties on the host cell surface, followed by the interaction of the chlamydial polymorphic membrane proteins (Pmps) with host cell receptors. Specifically, the interaction of the Pmp21 adhesin and invasin with its human interaction partner, the epidermal growth factor receptor, results in receptor activation, down‐stream signalling and finally internalization of the bacteria. Blocking both, the OmcB and Pmp21 adhesion pathways, did not completely abolish infection, suggesting the presence of additional factors relevant for host cell invasion. Here, we show that the novel surface protein CPn0473 of Chlamydia pneumoniae contributes to the binding and invasion of infectious chlamydial particles. CPn0473 is expressed late in the infection cycle and located on the infectious chlamydial cell surface. Soluble recombinant CPn0473 as well as rCPn0473‐coupled fluorescent latex beads adhere to human epithelial HEp‐2 cells. Interestingly, in classical infection blocking experiments pretreatment of HEp‐2 cells with rCPn0473 does not attenuate adhesion but promotes dose‐dependently internalization by C. pneumoniae suggesting an unusual mode of action for this adhesin. This CPn0473‐dependent promotion of infection by C. pneumoniae depends on two different domains within the protein and requires intact lipid rafts. Thus, inhibition of the interaction of CPn0473 with the host cell could provide a way to reduce the virulence of C. pneumoniae.

The cellular ceramide transport protein CERT promotesChlamydia psittaciinfection and controls bacterial sphingolipid uptake

“…In addition, entry via cholesterol‐rich lipid rafts has also been described for Chlamydia spp. (Fechtner, Galle, & Hegemann, ; Norkin, Wolfrom, & Stuart, ). Uptake requires the delivery of bacterial proteins into the host cell cytosol using a type III secretion system (Hsia, Pannekoek, Ingerowski, & Bavoil, ; Hybiske & Stephens, ; Nans, Ford, & Hayward, ).…”

Mycobacterium tuberculosis Primary Infection and Dissemination: A Critical Role for Alveolar Epithelial Cells

“…Furthermore, disruption of lipid rafts by pretreating the AEC with Filipin significantly reduced the numbers of intracellular bacteria suggesting a role for lipid raft targeting and aggregation in M. tb internalization by type 2 AEC. Whether it is M. tb adhesin:lipid raft interactions that promote uptake by AEC (or other non-phagocytic cells), either directly or through co-localized receptors, remains to be investigated; however, adhesins of other bacterial pathogens have been shown to mediate their uptake by non-phagocytic cells through lipid raft-dependent mechanisms including Chlamydia pneumoniae (Fechtner et al, 2016), Streptococcus pneumonia (Yamaguchi et al, 2013), and Shiga-toxigenic E. coli (Rogers et al, 2012).…”

Insights Into a Chlamydia pneumoniae-Specific Gene Cluster of Membrane Binding Proteins

“…In order to test whether the proteins have adhesive capacities, we performed adhesion studies in which human HEp-2 cells are tested for binding of selected recombinant (r) cluster proteins ( Figure 7A). Interestingly, compared to the controls, the chlamydial adhesin rCPn0473 (Fechtner et al, 2016) and rGST, we observed that only rMbp1 and rMbp4 proteins carrying a DUF575 domain were able to adhere to the human cells, while those carrying only the DUF562 (rMbp3) or no DUF at all (rMbp2) did not bind to the cells (Figure 7A). Furthermore, we could show that the DUF575 domain is essential for adhesion, as rMbp4 121−672 , a DUF575 deletion variant, clearly showed strongly reduced adhesion to HEp-2 ( Figure 7A).…”

“…Initial contact between the Cpn EB and the host cell is mediated by binding of conserved adhesins to various host cell structures. Of these, OmcB binds to heparansulfate-like proteoglycans (GAG), while LipP (CPn0473) binds to phospholipids in the host membrane, and Pmp21 interacts with the epidermal growth factor receptor (EGFR), serving as both an adhesin and an invasin (Moelleken and Hegemann, 2008;Mölleken et al, 2013;Fechtner et al, 2016). This last interaction promotes internalization of the EB by activating the EGFR, and the developing inclusion at first remains associated with the activated receptor (Mölleken et al, 2013).…”