CD14-dependent endotoxin internalization via a macropinocytic pathway
| Autor: | Jérôme Pugin, Jean-Louis Carpentier, Michelangelo Foti, Carine Poussin |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Lipopolysaccharides
Monocytes/physiology/ultrastructure Glycosylphosphatidylinositols Endocytic cycle Lipopolysaccharide Receptors Fluorescent Antibody Technique Vacuole Biochemistry Monocytes chemistry.chemical_compound Caveolae Phosphorylation Internalization Microscopy Immunoelectron Cytochalasin D media_common Membrane Glycoproteins ddc:617 Pinocytosis Transfection/genetics Membrane Glycoproteins/metabolism Coated Pits Cell-Membrane Cell biology Lysosomes/physiology Endosomes/physiology lipids (amino acids peptides and proteins) Cell activation Endosome media_common.quotation_subject Recombinant Fusion Proteins Endosomes Biology Transfection Cell Line Pinocytosis/physiology Antigens CD14/metabolism Centrifugation Density Gradient ddc:612 Molecular Biology Recombinant Fusion Proteins/genetics Endotoxins/metabolism Cell Biology Endotoxins Kinetics chemistry Cytochalasin D/pharmacology Glycosylphosphatidylinositols/physiology Lysosomes Coated Pits Cell-Membrane/physiology Lipopolysaccharides/metabolism |
| Zdroj: | Journal of Biological Chemistry, Vol. 273, No 32 (1998) pp. 20285-20291 |
| ISSN: | 0021-9258 |
| Popis: | Gram-negative bacterial endotoxin (a lipopolysaccharide (LPS)) specifically binds to CD14, a glycosylphosphatidyl inositol (GPI)-anchored surface myeloid glycoprotein. This interaction leads to cell activation, but it also promotes LPS internalization and detoxification. In this work, we investigated the route of LPS and CD14 internalization and the relevance of CD14 GPI anchor in the endocytic pathway. In promonocytic THP-1 cells transfected with a GPI or a chimeric integral form of CD14, we showed by differential buoyancy in sucrose density gradients that these two forms of CD14 were sorted to different plasma membrane subdomains. However, both forms of CD14 associated preferentially with the same surface microfilament-enriched microvilli or ruffles. Electron microscopic studies indicated that CD14 internalized via macropinocytosis, a process resembling that of phagocytosis, different from "classical" receptor-mediated endocytic pathways, such as clathrin-coated pits or caveolae. With cell warming, the CD14-enriched ruffles fused and formed large vesicles. Later, these vacuoles made stacks and condensed into phago-lysosomes. CD14 was specifically associated with all of these structures. Radiolabeled LPS internalization paralleled CD14 internalization. Confocal microscopic studies confirmed the co-localization of LPS and CD14 both at the cell surface and in endosomal compartments. The microfilament-disrupting, macropinocytosis blocking agent cytochalasin D inhibited LPS and CD14 internalization but did not prevent LPS-dependent activation, indicating that these two processes are dissociated. |
| Databáze: | OpenAIRE |
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