title: Borrelia burgdorferi CheD Promotes Various Functions in Chemotaxis and the Pathogenic Life Cycle of the Spirochete.
abstract: Borrelia burgdorferi possesses a sophisticated chemotaxis signaling system; however, the roles of the majority of the chemotaxis proteins in the infectious life cycle have not yet been demonstrated. Specifically, the role of CheD during host colonization has not been demonstrated in any bacterium. Here, we systematically characterized the B. burgdorferi CheD homolog using genetics and biochemical and mouse-tick-mouse infection cycle studies. Bacillus subtilis CheD plays an important role in chemotaxis by deamidation of methyl-accepting chemotaxis protein receptors (MCPs) and by increasing the receptor kinase activity or enhancing CheC phosphatase activity, thereby regulating the levels of the CheY response regulator. Our biochemical analysis indicates that B. burgdorferi CheD significantly enhances CheX phosphatase activity by specifically interacting with the phosphatase. Moreover, CheD specifically binds two of the six MCPs, indicating that CheD may also modulate the receptor proteins. Although the motility of the cheD mutant cells was indistinguishable from that of the wild-type cells, the mutant did exhibit reduced chemotaxis. Importantly, the mutant showed significantly reduced infectivity in C3H/HeN mice via needle inoculation. Mouse-tick-mouse infection assays indicated that CheD is dispensable for acquisition or transmission of spirochetes; however, the viability of cheD mutants in ticks is marginally reduced compared to that of the wild-type or complemented cheD spirochetes. These data suggest that CheD plays an important role in the chemotaxis and pathogenesis of B. burgdorferi We propose potential connections between CheD, CheX, and MCPs and discuss how these interactions play critical roles during the infectious life cycle of the spirochete.
authors.affiliation: Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA.
authors.forename: Ki Hwan
authors.initials: KH
authors.lastname: Moon
authors.affiliation: Department of Statistics, West Virginia University, Morgantown, West Virginia, USA.
authors.forename: Gerry
authors.initials: G
authors.lastname: Hobbs
authors.affiliation: Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA motalebm@ecu.edu.
authors.forename: M A
authors.initials: MA
authors.lastname: Motaleb
mesh_terms: D000818:Animals; D001096:Arachnid Vectors / Q000382:microbiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology; D025065:Borrelia burgdorferi / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D002633:Chemotaxis / Q000235:genetics / Q000276:immunology*; D004195:Disease Models, Animal; D015964:Gene Expression Regulation, Bacterial; D054884:Host-Pathogen Interactions; D008193:Lyme Disease / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D000072236:Methyl-Accepting Chemotaxis Proteins / Q000235:genetics* / Q000276:immunology; D051379:Mice; D008809:Mice, Inbred C3H; D009154:Mutation; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000276:immunology; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D013987:Ticks / Q000382:microbiology*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C446292:CheD protein, Bacillus subtilis; D000072236:Methyl-Accepting Chemotaxis Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D010744:Phosphoric Monoester Hydrolases