myelin-basic-protein and 5-hydroxy-6-8-11-14-eicosatetraenoic-acid

AA stimulates integrin-dependent neutrophil adhesion, a critical early step in acute inflammation. However, neither the signaling pathway(s) of AA-stimulated adhesion, nor whether AA acts directly or through the generation of active metabolites, has been elucidated. Previously, we have observed a tight association between neutrophil Erk activation and homotypic adhesion in response to chemoattractants acting through G protein-linked receptors. We now report a similar association between homotypic adhesion and Erk activation in response to AA. Erk activation was cyclooxygenase independent and required AA metabolism to 5(S)- hydroperoxyeicosatetraenoic acid (5-HpETE) via 5-lipoxygenase, but not the further lipoxygenase-dependent metabolism of 5-HpETE to leukotrienes. AA stimulation of Erk was accompanied by Raf-1 activation and was sensitive to inhibitors of Raf-1 and Mek. Whereas activation of Erk by AA was pertussis toxin sensitive, [3H]-AA binding to neutrophils was not saturable, suggesting that an AA metabolite activates a G protein. Consistent with this hypothesis, Erk activation by 5(S)-hydroxyeicosatetraenoic acid (5-HETE; lipoxygenase-independent metabolite of 5-HpETE) was also pertussis toxin sensitive. These data suggest that a 5-lipoxygenase metabolite of AA, e.g., 5-HETE, is released from AA-treated cells to engage a plasma membrane-associated, pertussis toxin-sensitive, G protein-linked receptor, leading to activation of Erk and adhesion via the Raf-1/Mek signal transduction pathway.

Topics: Arachidonate 5-Lipoxygenase; Arachidonic Acid; Cell Adhesion; Cell Aggregation; Cyclic AMP; Enzyme Activation; Humans; Hydroxyeicosatetraenoic Acids; Integrins; MAP Kinase Kinase Kinase 1; Mitogen-Activated Protein Kinases; Myelin Basic Protein; Nerve Tissue Proteins; Neutrophils; Pertussis Toxin; Phosphorylation; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins c-raf; Virulence Factors, Bordetella