Bacterial lipopolysaccharide stimulates protein tyrosine phosphorylation in macrophages.

Abstract

Lipopolysaccharide (LPS), a membrane component of Gram-negative bacteria, stimulates immune responses by activating macrophages, B lymphocytes, and other cells of the immune system. The mechanisms by which LPS activates these cells are poorly characterized. Since protein tyrosine phosphorylation appears to be a major intracellular signaling event that mediates cellular responses, we examined whether LPS alters tyrosine phosphorylation in macrophages.We found that Escherichia coli K235 LPS increased tyrosine phosphorylation of several proteins in the RAW 264.7 murine macrophage cell line and in resident peritoneal macrophages from C3H/HeSNJ mice. Changes in tyrosine phosphorylation were detectable by 4-5 min, reached a maximum by 15 min, and declined after 30-60 min. Protein tyrosine phosphorylation increased following stimulation with LPS at 100 pg/ml and was maximal with 10 ng/ml. Similar changes in tyrosine phosphorylation were induced by Salmonella minnesota R595 LPS and by the biologically active domain of LPS, lipid A, but not by the inactive lipid A derivative N2-monoacylglucosamine 1-phosphate. Phorbol 12-myristate 13-acetate also stimulated protein tyrosine phosphorylation, but some of the modulated proteins were different than those phosphorylated by LPS. Treatment ofRAW 264.7 cells with a tyrosine kinase inhibitor, herbimycin A, inhibited both LPS-stimulated tyrosine phosphorylation and LPS-stimulated release of arachidonic acid metabolites. Thus, increased protein tyrosine phosphorylation is a rapid LPSactivated signaling event that may mediate release of arachidonic acid metabolites in RAW 264.7 cells.

Lipopolysaccharide and Raf-1 Kinase Regulate Secretory Interleukin-1 Receptor Antagonist Gene Expression by Mutually Antagonistic Mechanisms

“…The increases in MAPK activity observed in the in vitro kinase assay were consistent with observation of decreased migration of immunoreactive MAPK. This result is indicative of increased tyrosine phosphorylation, which has been shown to correlate with increased MAPK activity (51,74). These results demonstrate that LPS treatment as well as transfection with pRSV-Raf-BXB increases p42 MAPK activity in RAW 264.7 cells.…”

“…LPS is thought to signal in part through interaction with CD14, a glycosylphosphatidylinositol-linked protein found on the surface of monocytic cells (76). Signaling events which have been identified in monocytic cells following stimulation with LPS include phosphorylation of a number of cellular proteins and activation of the Src family tyrosine kinases Lyn, Hck, and Fgr (68,74,75). In addition, LPS stimulation has been reported to activate p42/44 mitogenactivated protein kinases (MAPKs) in monocytes and macrophages (44,75).…”

Protein-Tyrosine Kinase Syk Expressed in Human Nasal Fibroblasts and Its Effect on RANTES Production

“…We also found Syk expression in human nasal polyp-derived fibroblasts. LPS augments tyrosine phosphorylation (11,12,14), which results in phosphorylation or activation of mitogen-activated protein (MAP) kinases: 44-and 42-kDa MAP kinases (extracellular signal-related kinase 1 and 2) (14, 32), stress-activated protein kinase/ JNK (33), and p38 kinase (10,14,34). In this study, we demonstrated that LPS induced tyrosine phosphorylation of Syk and activated JNK1 in nasal fibroblast lines.…”

Toll‐like receptor‐mediated tyrosine phosphorylation of paxillin via MyD88‐dependent and ‐independent pathways

“…LPS has been reported to increase tyrosine phosphorylation in macrophages [21,22,31]. Since little is reported about the effects of pathogens other than LPS, it is of interest to examine whether the phosphorylation is an event commonly induced by diverse TLR ligands or an event specifically induced by LPS.…”