Rickettsial outer-membrane protein B (rOmpB) mediates bacterial invasion through Ku70 in an actin, c-Cbl, clathrin and caveolin 2-dependent manner

Cell Microbiol. 2009 Apr;11(4):629-44. doi: 10.1111/j.1462-5822.2008.01279.x. Epub 2009 Jan 7.

Abstract

Rickettsia conorii, an obligate intracellular tick-borne pathogen and the causative agent of Mediterranean spotted fever, binds to and invades non-phagocytic mammalian cells. Previous work identified Ku70 as a mammalian receptor involved in the invasion process and identified the rickettsial autotransporter protein, rOmpB, as a ligand; however, little is known about the role of Ku70-rOmpB interactions in the bacterial invasion process. Using an Escherichia coli heterologous expression system, we show here that rOmpB mediates attachment to mammalian cells and entry in a Ku70-dependent process. A purified recombinant peptide corresponding to the rOmpB passenger domain interacts with Ku70 and serves as a competitive inhibitor of adherence. We observe that rOmpB-mediated infection culminates in actin recruitment at the bacterial foci, and that this entry process relies in part on actin polymerization likely imparted through protein tyrosine kinase and phosphoinositide 3-kinase-dependent activities and microtubule stability. Small-interfering RNA studies targeting components of the endocytic pathway reveal that entry by rOmpB is dependent on c-Cbl, clathrin and caveolin-2. Together, these results illustrate that rOmpB is sufficient to mediate Ku70-dependent invasion of mammalian cells and that clathrin- and caveolin-dependent endocytic events likely contribute to the internalization process.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / metabolism
  • Animals
  • Antigens, Nuclear / metabolism*
  • Bacterial Outer Membrane Proteins / metabolism*
  • Caveolin 2 / metabolism
  • Chlorocebus aethiops
  • Clathrin / metabolism
  • DNA-Binding Proteins / metabolism*
  • Epithelial Cells / microbiology*
  • HeLa Cells / microbiology
  • Host-Pathogen Interactions*
  • Humans
  • Ku Autoantigen
  • Proto-Oncogene Proteins c-cbl / metabolism
  • Rickettsia conorii / metabolism
  • Rickettsia conorii / pathogenicity*
  • Rickettsia conorii / physiology
  • Vero Cells / microbiology

Substances

  • Actins
  • Antigens, Nuclear
  • Bacterial Outer Membrane Proteins
  • Caveolin 2
  • Clathrin
  • DNA-Binding Proteins
  • Proto-Oncogene Proteins c-cbl
  • Xrcc6 protein, human
  • Ku Autoantigen
  • CBL protein, human