Mediators of innate immune recognition of bacteria concentrate in lipid rafts and facilitate lipopolysaccharide-induced cell activation.
The plasma membrane of cells is composed of lateral heterogeneities, patches and microdomains. These membrane microdomains or lipid rafts are enriched in glycosphingolipids and cholesterol and have been implicated in cellular processes such as membrane sorting and signal transduction. In this study we investigated the importance of lipid raft formation in the innate immune recognition of bacteria using biochemical and fluorescence imaging techniques. We found that receptor molecules that are implicated in lipopolysaccharide (LPS)-cellular activation, such as CD14, heat shock protein (hsp) 70, 90, Chemokine receptor 4 (CXCR4), growth differentiation factor 5 (GDF5) and Toll-like receptor 4 (TLR4), are present in microdomains following LPS stimulation. Lipid raft integrity is essential for LPS-cellular activation, since raft-disrupting drugs, such as nystatin or MCD, inhibit LPS-induced TNF-alpha secretion. Our results suggest that the entire bacterial recognition system is based around the ligation of CD14 by bacterial components and the recruitment of multiple signalling molecules, such as hsp70, hsp90, CXCR4, GDF5 and TLR4, at the site of CD14-LPS ligation, within the lipid rafts.
Triantafilou
Martha
M
University of Portsmouth, School of Biological Sciences, King Henry Building, King Henry I Street, Portsmouth, PO1 2DY, UK.
Miyake
Kensuke
K
Golenbock
Douglas T
DT
Triantafilou
Kathy
K
D000818:Animals; D001419:Bacteria / Q000276:immunology*; D001424:Bacterial Infections / Q000276:immunology*; D019485:Bone Morphogenetic Proteins / Q000187:drug effects / Q000276:immunology; D016466:CHO Cells; D006224:Cricetinae; D029721:Drosophila Proteins; D005677:G(M1) Ganglioside / Q000276:immunology; D055428:Growth Differentiation Factor 5; D018840:HSP70 Heat-Shock Proteins / Q000187:drug effects / Q000276:immunology; D018841:HSP90 Heat-Shock Proteins / Q000187:drug effects / Q000276:immunology; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology* / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000276:immunology; D021962:Membrane Microdomains / Q000187:drug effects / Q000276:immunology*; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000276:immunology; D009761:Nystatin / Q000494:pharmacology; D019718:Receptors, CXCR4 / Q000187:drug effects / Q000276:immunology; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000276:immunology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D019485:Bone Morphogenetic Proteins; D029721:Drosophila Proteins; C525893:GDF5 protein, human; D055428:Growth Differentiation Factor 5; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D019718:Receptors, CXCR4; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D009761:Nystatin; D005677:G(M1) Ganglioside; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases