| Abstract: | Cellular tubulin is subject to a posttranslational modification involving the reversible addition to tyrosine through peptide linkage to the C-terminal glutamate of the alpha-chain. The synthetic peptide chemoattractant, N-formyl-methionyl-leucyl-phenylalanine, causes a specific, dose-dependent stimulation of tubulin tyrosinolation in rabbit leukocytes. This stimulation is prevented by carbobenzoxy-phenylalanyl-methionine, benzoyl-tyrosine ethylester, and nordihydroguaiaretic acid, which are all inhibitors of chemotaxis presumed to act via membrane-associated events. The combination of 3-deazaadenosine and homocysteine thiolactone, which inhibits phospholipid methylation, and quinacrine, an inhibitor of phospholipase A2, also abolishes the response to the peptide. Colchicine, however, which causes a marked disassembly of cellular microtubules in these cells and also inhibits chemotaxis, does not have any inhibitory effect on the basal or peptide-stimulated rate of tubulin tyrosinolation. In contrast, taxol, a microtubule-stabilizing agent, has an inhibitory effect on both the basal and peptide-stimulated tyrosine incorporation. Taxol also inhibits chemotaxis in rabbit leukocytes. The results strongly suggest the role of closely linked membrane-cytoskeleton interactions in leukocyte chemotaxis, in which tyrosinolation of tubulin may be functionally involved. |
