The polysaccharide portion plays an indispensable role in Salmonella lipopolysaccharide-induced activation of NF-kappaB through human toll-like receptor 4.
The lipid A portion has been identified as the active center responsible for lipopolysaccharide (LPS)-induced macrophage activation. However, we found that Salmonella (Salmonella enterica serovars Abortusequi, Minnesota, and Typhimurium) lipid A is inactive in human macrophages, despite its LPS being highly active. Thus we investigated the critical role of polysaccharide in Salmonella LPS-induced activation of NF-kappaB. In human monocytic cell line THP-1, Salmonella lipid A and synthetic Salmonella-type lipid A (516) did not induce NF-kappaB-dependent reporter activity up to 1 micro g/ml, whereas strong activation was observed in response to Salmonella LPS. The difference in activity between this lipid A and LPS was further examined by using 293 cells expressing human CD14/Toll-like receptor 4 (TLR4)/MD-2, and similar results were obtained in these cells as well. A polysaccharide preparation obtained from Salmonella LPS was inactive in 293 cells expressing human CD14/TLR4/MD-2 even in combination with 516. Salmonella enterica serovar Minnesota Re LPS, whose structure consists of lipid A and two molecules of 2-keto-3-deoxyoctonic acid, but not its lipid A exhibited strong activity in THP-1 cells and 293 cells expressing human CD14/TLR4/MD-2. These results indicate that the polysaccharide portion covalently bound to lipid A plays the principal role in Salmonella LPS-induced activation of NF-kappaB through human CD14/TLR4/MD-2.
Muroi
Masashi
M
Division of Microbiology, National Institute of Health Sciences, Setagaya, Tokyo 158-8501, Japan.
Tanamoto
Ken-Ichi
K
D000818:Animals; D000954:Antigens, Surface / Q000502:physiology; D002460:Cell Line; D029721:Drosophila Proteins; D006801:Humans; D008050:Lipid A / Q000737:chemistry / Q000494:pharmacology*; D018950:Lipopolysaccharide Receptors / Q000502:physiology; D008070:Lipopolysaccharides / Q000737:chemistry / Q000494:pharmacology*; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000502:physiology*; D012475:Salmonella / Q000472:pathogenicity*; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D000954:Antigens, Surface; D029721:Drosophila Proteins; C495377:LY96 protein, human; D008050:Lipid A; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011135:Polysaccharides, Bacterial; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors