Bacterial killing by complement requires direct anchoring of membrane attack complex precursor C5b-7

Autoři: Dennis J. Doorduijn aff001;  Bart W. Bardoel aff001;  Dani A. C. Heesterbeek aff001;  Maartje Ruyken aff001;  Georgina Benn aff002;  Edward S. Parsons aff002;  Bart W. Hoogenboom aff002;  Suzan H. M. Rooijakkers aff001
Působiště autorů: Department of Medical Microbiology, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands aff001;  London Centre for Nanotechnology, University College London, London, United Kingdom aff002;  Institute of Structural and Molecular Biology, University College London, London, United Kingdom aff003;  National Physical Laboratory, Teddington, United Kingdom aff004;  Department of Physics and Astronomy, University College London, London, United Kingdom aff005
Vyšlo v časopise: Bacterial killing by complement requires direct anchoring of membrane attack complex precursor C5b-7. PLoS Pathog 16(6): e32767. doi:10.1371/journal.ppat.1008606
Kategorie: Research Article
doi: 10.1371/journal.ppat.1008606


An important effector function of the human complement system is to directly kill Gram-negative bacteria via Membrane Attack Complex (MAC) pores. MAC pores are assembled when surface-bound convertase enzymes convert C5 into C5b, which together with C6, C7, C8 and multiple copies of C9 forms a transmembrane pore that damages the bacterial cell envelope. Recently, we found that bacterial killing by MAC pores requires local conversion of C5 by surface-bound convertases. In this study we aimed to understand why local assembly of MAC pores is essential for bacterial killing. Here, we show that rapid interaction of C7 with C5b6 is required to form bactericidal MAC pores on Escherichia coli. Binding experiments with fluorescently labelled C6 show that C7 prevents release of C5b6 from the bacterial surface. Moreover, trypsin shaving experiments and atomic force microscopy revealed that this rapid interaction between C7 and C5b6 is crucial to efficiently anchor C5b-7 to the bacterial cell envelope and form complete MAC pores. Using complement-resistant clinical E. coli strains, we show that bacterial pathogens can prevent complement-dependent killing by interfering with the anchoring of C5b-7. While C5 convertase assembly was unaffected, these resistant strains blocked efficient anchoring of C5b-7 and thus prevented stable insertion of MAC pores into the bacterial cell envelope. Altogether, these findings provide basic molecular insights into how bactericidal MAC pores are assembled and how bacteria evade MAC-dependent killing.

Klíčová slova:

Atomic force microscopy – Bacteria – Complement system – Flow cytometry – Gram negative bacteria – Lysis (medicine) – Red blood cells – Serine proteases


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