title: Minor modifications to the phosphate groups and the C3' acyl chain length of lipid A in two Bordetella pertussis strains, BP338 and 18-323, independently affect Toll-like receptor 4 protein activation.
abstract: Lipopolysaccharides (LPS) of Bordetella pertussis are important modulators of the immune system. Interaction of the lipid A region of LPS with the Toll-like receptor 4 (TLR4) complex causes dimerization of TLR4 and activation of downstream nuclear factor κB (NFκB), which can lead to inflammation. We have previously shown that two strains of B. pertussis, BP338 (a Tohama I-derivative) and 18-323, display two differences in lipid A structure. 1) BP338 can modify the 1- and 4'-phosphates by the addition of glucosamine (GlcN), whereas 18-323 cannot, and 2) the C3' acyl chain in BP338 is 14 carbons long, but only 10 or 12 carbons long in 18-323. In addition, BP338 lipid A can activate TLR4 to a greater extent than 18-323 lipid A. Here we set out to determine the genetic reasons for the differences in these lipid A structures and the contribution of each structural difference to the ability of lipid A to activate TLR4. We show that three genes of the lipid A GlcN modification (Lgm) locus, lgmA, lgmB, and lgmC (previously locus tags BP0399-BP0397), are required for GlcN modification and a single amino acid difference in LpxA is responsible for the difference in C3' acyl chain length. Furthermore, by introducing lipid A-modifying genes into 18-323 to generate isogenic strains with varying penta-acyl lipid A structures, we determined that both modifications increase TLR4 activation, although the GlcN modification plays a dominant role. These results shed light on how TLR4 may interact with penta-acyl lipid A species.
authors: Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors: Nita R
authors: NR
authors: Shah
authors: Sami
authors: S
authors: Albitar-Nehme
authors: Emma
authors: E
authors: Kim
authors: Nico
authors: N
authors: Marr
authors: Alexey
authors: A
authors: Novikov
authors: Martine
authors: M
authors: Caroff
authors: Rachel C
authors: RC
authors: Fernandez
mesh_terms: D001886:Bordetella pertussis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002240:Carbohydrate Sequence; D002460:Cell Line; D056426:Genetic Loci; D006801:Humans; D008050:Lipid A / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization; D013045:Species Specificity; D051197:Toll-Like Receptor 4 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D008050:Lipid A; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4