Lipopolysaccharide-induced change of phosphorylation of two cytosolic proteins in human monocytes is prevented by inhibitors of ADP-ribosylation.
Interaction of LPS with human monocytes causes altered phosphate labeling of cytosolic proteins of 36 kDa and 38 kDa (p36/38). This property, determined by in vitro studies, is shared by other monocyte activators. Phosphorylated p36/38 are distinct from p38, 42-kDa, and 44-kDa isoforms of mitogen-activated protein kinases expressed in monocytes. Occupation of LPS binding sites by a LPS antagonist, the synthetic tetraacylated bisphosphate precursor of Escherichia coli lipid A (also known as compound 406, lipid IVa, or precursor Ia), prevents LPS-induced changes in the phosphate labeling of the two proteins. Abs against CD14 inhibit protein phosphorylation induced by low concentrations of LPS (10 ng/ml), whereas at high concentrations (1 microgram/ml), the Abs fail to prevent phosphorylation. In addition to phosphorylation, ADP-ribosylation of proteins has been implicated in a number of biologic processes. Here we show that inhibitors of ADP-ribosylation, namely meta-iodobenzylguanidine and nicotinamide, inhibit LPS-initiated altered phosphorylation of p36/38. This loss of phosphate labeling of p36/38 is accompanied by an inhibition of TNF-alpha and Il-6 mRNA and protein production. The synthesis of IL-1 is not affected. This suggests that the inhibitors interfere with specific steps in IL-6 and TNF-alpha production, which are not required for IL-1 synthesis. Taken together, the data indicate that ADP-ribosylation may be involved in LPS-induced alteration of the phosphorylation state of two cytosolic proteins (p36/38) and that these proteins modulate cellular processes leading to TNF-alpha and IL-6 release.
Heine
H
H
Department of Immunology and Cell Biology, Borstel Research Institute, Germany.
Ulmer
A J
AJ
Flad
H D
HD
Hauschildt
S
S
D019797:3-Iodobenzylguanidine; D002478:Cells, Cultured; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D007462:Iodobenzenes / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D009536:Niacinamide / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011506:Proteins / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
D015850:Interleukin-6; D007462:Iodobenzenes; D008070:Lipopolysaccharides; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011506:Proteins; D014409:Tumor Necrosis Factor-alpha; D009536:Niacinamide; D019797:3-Iodobenzylguanidine