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Functional Recruitment of Human Complement Inhibitor C4b-Binding Protein to Outer Membrane Protein Rck of Salmonella

Ho, Derek K.; Tissari, Jorma; Jarvinen, Hanna M.; Blom, Anna LU ; Meri, Seppo and Jarva, Hanna (2011) In PLoS ONE 6(11).
Abstract
Resistance to complement mediated killing, or serum resistance, is a common trait of pathogenic bacteria. Rck is a 17 kDa outer membrane protein encoded on the virulence plasmid of Salmonella enterica serovars Typhimurium and Enteritidis. When expressed in either E. coli or S. enterica Typhimurium, Rck confers LPS-independent serum resistance as well as the ability to bind to and invade mammalian cells. Having recently shown that Rck binds the inhibitor of the alternative pathway of complement, factor H (fH), we hypothesized that Rck can also bind the inhibitor of the classical and lectin pathways, C4b-binding protein (C4BP). Using flow cytometry and direct binding assays, we demonstrate that E. coli expressing Rck binds C4BP from... (More)
Resistance to complement mediated killing, or serum resistance, is a common trait of pathogenic bacteria. Rck is a 17 kDa outer membrane protein encoded on the virulence plasmid of Salmonella enterica serovars Typhimurium and Enteritidis. When expressed in either E. coli or S. enterica Typhimurium, Rck confers LPS-independent serum resistance as well as the ability to bind to and invade mammalian cells. Having recently shown that Rck binds the inhibitor of the alternative pathway of complement, factor H (fH), we hypothesized that Rck can also bind the inhibitor of the classical and lectin pathways, C4b-binding protein (C4BP). Using flow cytometry and direct binding assays, we demonstrate that E. coli expressing Rck binds C4BP from heat-inactivated serum and by using the purified protein. No binding was detected in the absence of Rck expression. C4BP bound to Rck is functional, as we observed factor I-mediated cleavage of C4b in cofactor assays. In competition assays, binding of radiolabeled C4BP to Rck was reduced by increasing concentrations of unlabeled protein. No effect was observed by increasing heparin or salt concentrations, suggesting mainly non-ionic interactions. Reduced binding of C4BP mutants lacking complement control protein domains (CCPs) 7 or 8 was observed compared to wt C4BP, suggesting that these CCPs are involved in Rck binding. While these findings are restricted to Rck expression in E. coli, these data suggest that C4BP binding may be an additional mechanism of Rck-mediated complement resistance. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
PLoS ONE
volume
6
issue
11
publisher
Public Library of Science
external identifiers
  • wos:000297348800032
  • scopus:80755126035
ISSN
1932-6203
DOI
10.1371/journal.pone.0027546
language
English
LU publication?
yes
id
395a4273-da04-4daf-ab79-9657ebd7f9f7 (old id 2270418)
date added to LUP
2012-01-02 09:47:19
date last changed
2017-04-16 03:51:14
@article{395a4273-da04-4daf-ab79-9657ebd7f9f7,
  abstract     = {Resistance to complement mediated killing, or serum resistance, is a common trait of pathogenic bacteria. Rck is a 17 kDa outer membrane protein encoded on the virulence plasmid of Salmonella enterica serovars Typhimurium and Enteritidis. When expressed in either E. coli or S. enterica Typhimurium, Rck confers LPS-independent serum resistance as well as the ability to bind to and invade mammalian cells. Having recently shown that Rck binds the inhibitor of the alternative pathway of complement, factor H (fH), we hypothesized that Rck can also bind the inhibitor of the classical and lectin pathways, C4b-binding protein (C4BP). Using flow cytometry and direct binding assays, we demonstrate that E. coli expressing Rck binds C4BP from heat-inactivated serum and by using the purified protein. No binding was detected in the absence of Rck expression. C4BP bound to Rck is functional, as we observed factor I-mediated cleavage of C4b in cofactor assays. In competition assays, binding of radiolabeled C4BP to Rck was reduced by increasing concentrations of unlabeled protein. No effect was observed by increasing heparin or salt concentrations, suggesting mainly non-ionic interactions. Reduced binding of C4BP mutants lacking complement control protein domains (CCPs) 7 or 8 was observed compared to wt C4BP, suggesting that these CCPs are involved in Rck binding. While these findings are restricted to Rck expression in E. coli, these data suggest that C4BP binding may be an additional mechanism of Rck-mediated complement resistance.},
  author       = {Ho, Derek K. and Tissari, Jorma and Jarvinen, Hanna M. and Blom, Anna and Meri, Seppo and Jarva, Hanna},
  issn         = {1932-6203},
  language     = {eng},
  number       = {11},
  publisher    = {Public Library of Science},
  series       = {PLoS ONE},
  title        = {Functional Recruitment of Human Complement Inhibitor C4b-Binding Protein to Outer Membrane Protein Rck of Salmonella},
  url          = {http://dx.doi.org/10.1371/journal.pone.0027546},
  volume       = {6},
  year         = {2011},
}