title: Requirement of S-adenosyl-L-methionine-mediated methylation for human monocyte chemotaxis.
abstract: The chemotactic response of motile bacteria requires the methylation of specific proteins by S-adenosyl-L-methionine. To determine whether methylation is required for the chemotaxis of human leukocytes, we studied the effects of inhibition of S-adenosyl-L-methionine-mediated methylation on monocyte chemotactic responsiveness. Methylation was inhibited in monocytes by treating the cells with substances that produced elevations in intracellular S-adenosyl-L-homocysteine, a competitive inhibitor of S-adenosyl-L-methionine methylation. Treatment of isolated monocytes with the adenosine deaminase inhibitor, erythro-9-(2-hydroxy-3-nonyl)adenine, plus exogenous adenosine and L-homocysteine thiolactone increased intracellular S-adenosyl-L-homocysteine levels by as much as 1500-fold. Concomitant with increases in S-adenosyl-L-homocysteine were a decrease in monocyte protein carboxy-O-methylation as well as a marked inhibition of monocyte chemotactic responsiveness. Conditions that almost completely inhibited methylation and chemotaxis did not depress monocyte phagocytosis, indicating that this latter function either is independent of S-adenosyl-L-methionine-mediated methylation or is extremely resistant to inhibition of such reactions by S-adenosyl-L-homocysteine. These studies indicate that S-adenosyl-L-methionine-mediated methylation is required for the chemotaxis of eukaryotic cells and that the chemotactic and phagocytic functions of human monocytes have different requirements for methylation.
mesh_terms: D058892:Adenosine Deaminase Inhibitors; D001798:Blood Proteins / Q000378:metabolism; D002634:Chemotaxis, Leukocyte; D006801:Humans; D008745:Methylation; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D010587:Phagocytosis; D012435:S-Adenosylhomocysteine / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism*
chemical_list: D058892:Adenosine Deaminase Inhibitors; D001798:Blood Proteins; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine