The role of the Chlamydia pneumoniae protein Pmp21 during infection
Zusammenfassung der Projektergebnisse
During the second funding period of the Research Unit 729 we focused on three major issues in our research. We identified the receptor for the Chlamydia pneumoniae adhesin Pmp21 and subsequently characterized in depth the adhesin – receptor interaction. Secondly, we tried to elucidate whether the C. pneumoniae Pmp proteins are involved in antigenic variation. Thirdly, we analyzed the formation of hetero- or homo-oligomeric structures among Pmp proteins. We successfully established a biochemical approach combining biotinylation of recombinant proteins, crosslinking and affinity purification which led to the identification of the human EGF receptor as interaction partner for Pmp21. In the course of a detailed analysis we could show that EGFR is not only essential for binding of C. pneumoniae to human cells, but also for the subsequent internalization of the infectious elementary bodies. We were able to show that the interaction with Pmp21 results in activation of the receptor, which colocalizes from onset of bacterial attachment to completed internalization with the Chlamydia and that this activation is necessary for a successful internalization into the host cell. Moreover, we could show that the Pmp21-EGFR mediated internalization of C. pneumoniae requires the presence of two essential EGFR adaptor proteins, c-Cbl and Grb2, both of which co-localize with internalized bacteria. If we inhibit binding of those adaptors to the receptor we can diminish infectivity and chlamydial internalization. Finally, we were able to identify the interaction domain within the receptor required for binding of Pmp21. Taken together we could show for the first time the interaction of the C. pneumoniae invasin protein Pmp21 with its human partner EGFR and that this interaction is the trigger for internalization of the bacterium. When we characterized the expression profile of Pmp proteins, we found that the C. pneumoniae Pmp proteins, Pmp6, Pmp20 and Pmp21 show a differential expression pattern during infection with Pmp21 being expressed constitutively while the other 2 Pmp proteins were only expressed in a subset of inclusions suggesting an immune evasion mechanism. Finally, we investigated oligomerization and self-interaction of full length or processed Pmp proteins and could show that Pmp21 fragments can form oligomers and are able to interact with themselves. Moreover, we found interaction among different C. pneumoniae Pmp proteins indicating that they may form higher order structures to fulfill their function.
Projektbezogene Publikationen (Auswahl)
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(2010) Members of the Pmp protein family of Chlamydia pneumoniae mediate adhesion to human cells via short repetitive peptide motifs. Mol Microbiol. 78(4): 1004-17
Mölleken K, Schmidt E, Hegemann JH
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(2012) Chlamydial adhesion and adhesins. In: Tan M, and Bavoil PM (eds). Intracellular Pathogens I Chlamydiales, ASM Press Washington, D.C.
Hegemann JH, Moelleken K
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(2013) The Chlamydia pneumoniae invasin protein Pmp21 recruits the EGF receptor for host cell entry. PLoS Pathog. 9(4): e1003325
Mölleken K, Becker E, Hegemann JH
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(2014) All subtypes of the Pmp adhesin family are implicated in chlamydial virulence and show species-specific function. Microbiologyopen 3(4): 544-556
Becker E, Hegemann JH
