g(m1)-ganglioside and lipoteichoic-acid

Lipoteichoic acid (LTA), a key cell wall component of Gram-positive bacteria, seems to function as an immune activator with characteristics very similar to lipopolysaccharide from Gram-negative bacteria. It has been shown that LTA binds CD14 and triggers activation via Toll-like receptor 2, but whether the activation occurs at the cell surface or internalization is required to trigger signaling has yet to be demonstrated. In this work we have investigated LTA binding and internalization and found that LTA and its receptor molecules accumulate in lipid rafts and are subsequently targeted rapidly to the Golgi apparatus. This internalization seems to be lipid raft-dependent because raft-disrupting drugs inhibited LTA/Toll-like receptor 2 colocalization in the Golgi. Similarly to lipopolysaccharide, LTA activation occurs at the cell surface, and the observed trafficking is independent of signaling.

Topics: Animals; Cell Line; Cell Membrane; CHO Cells; Cricetinae; Energy Transfer; Enzyme-Linked Immunosorbent Assay; Fluorescence Resonance Energy Transfer; G(M1) Ganglioside; Genes, Reporter; Golgi Apparatus; Humans; Lipopolysaccharide Receptors; Lipopolysaccharides; Luciferases; Membrane Glycoproteins; Membrane Microdomains; Microscopy, Fluorescence; Plasmids; Protein Binding; Receptors, Cell Surface; Signal Transduction; Staphylococcus aureus; Teichoic Acids; Toll-Like Receptor 2; Toll-Like Receptors; Tumor Necrosis Factor-alpha

Airway epithelial cells provide an immediate response to bacterial pathogens by producing chemokines and cytokines that recruit polymorphonuclear leukocytes (PMNs) to the site of infection. This response is excessive in patients with cystic fibrosis (CF) who have bacterial contamination of their airways. We postulated that CF airway pathogens, in activating nuclear factor-kappaB-dependent gene transcription in epithelial cells, would promote expression of cytokines that inhibit constitutive apoptosis of recruited PMNs. Epithelial cell culture supernatants from CF (IB-3) and corrected (C-38) epithelial cells stimulated by Staphylococcus aureus or Pseudomonas aeruginosa, increased survival of PMNs by 2- to 5-fold. Enhanced PMN survival was attributed to effects of epithelial granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor expression, which inhibit PMN apoptosis, and was negated by neutralizing antibody to either cytokine. Both CF and normal cells responded to bacteria with increased cytokine production. Granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor expression were activated by ligation of asialoGM1, a receptor for P. aeruginosa and S. aureus, and by S. aureus lipoteichoic acid. Lipopolysaccharide was not a potent stimulus of cytokine expression, and P. aeruginosa algC (lipopolysaccharide) and lasR (quorum sensing) mutants were fully capable of activating epithelial cells. Induced expression of cytokines by airway cells repeatedly exposed to bacteria, as occurs in CF, serves not only to recruit and activate PMNs, but also to enhance their survival.

Topics: Antibodies; Apoptosis; Bacterial Proteins; Bronchi; Cell Survival; Cells, Cultured; Culture Media, Conditioned; Cystic Fibrosis; DNA-Binding Proteins; Epithelial Cells; G(M1) Ganglioside; Granulocyte Colony-Stimulating Factor; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Lipopolysaccharides; Mutation; Neutrophils; Phosphotransferases (Phosphomutases); Pseudomonas aeruginosa; Reference Values; Staphylococcus aureus; Teichoic Acids; Trans-Activators