title: OmpA-mediated rickettsial adherence to and invasion of human endothelial cells is dependent upon interaction with α2β1 integrin.
abstract: Rickettsia conorii, a member of the spotted fever group (SFG) of the genus Rickettsia and causative agent of Mediterranean spotted fever, is an obligate intracellular pathogen capable of infecting various mammalian cell types. SFG rickettsiae express two major immunodominant surface cell antigen (Sca) proteins, OmpB (Sca5) and OmpA (Sca0). While OmpB-mediated entry has been characterized, the contribution of OmpA has not been well defined. Here we show OmpA expression in Escherichia coli is sufficient to mediate adherence to and invasion of non-phagocytic human endothelial cells. A recombinant soluble C-terminal OmpA protein domain (954-1735) with predicted structural homology to the Bordetella pertussis pertactin protein binds mammalian cells and perturbs R. conorii invasion by interacting with several mammalian proteins including β1 integrin. Using functional blocking antibodies, small interfering RNA transfection, and mouse embryonic fibroblast cell lines, we illustrate the contribution of α2β1 integrin as a mammalian ligand involved in R. conorii invasion of primary endothelial cells. We further demonstrate that OmpA-mediated attachment to mammalian cells is in part dependent on a conserved non-continuous RGD motif present in a predicted C-terminal 'pertactin' domain in OmpA.Our results demonstrate that multiple adhesin-receptor pairs are sufficient in mediating efficient bacterial invasion of R. conorii.
authors.affiliation: Department of Microbiology, The University of Chicago, 920 East 58th Street, Cummings Life Sciences Center 707A, Chicago, IL 60637, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Hillman
authors.forename: Yasmine M
authors.initials: YM
authors.lastname: Baktash
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Martinez
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000235:genetics* / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000276:immunology; D001907:Boutonneuse Fever / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D006801:Humans; D038982:Integrin alpha2beta1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D012281:Rickettsia / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D020114:Rickettsia conorii / Q000235:genetics / Q000472:pathogenicity
chemical_list: D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D038982:Integrin alpha2beta1; C078167:OMPA outer membrane proteins