Tubulin tyrosinolation in human polymorphonuclear leukocytes: studies in normal subjects and in patients with the Chediak-Higashi syndrome

We have recently reported a specific dose-dependent stimulation of posttranslational incorporation of tyrosine into tubulin alpha-chains of rabbit peritoneal leukocytes as induced by the synthetic peptide chemoattractant formyl-methionyl-leucyl-phenylalanine (FMLP). The present study reports a similar, specific stimulation of tubulin tyrosinolation in human polymorphonuclear leukocytes (PMN). When compared to normal PMN, both the resting and FMLP-stimulated levels of posttranslational tyrosine incorporation were two- to threefold higher in PMN of three patients with the Chediak-Higashi syndrome (CHS). The concentration of cellular tubulin and the specific activity of tubulin tyrosine ligase were similar in PMN of CHS patients and normal donors and resembled that of other non-neuronal cells. The high levels of tyrosine incorporation in PMN of CHS patients were normalized by the administration of ascorbate, both in vitro and in in vivo experiments. In vitro addition of ascorbate also inhibited the FMLP-induced stimulation of tyrosine incorporation in both normal and CHS cells. Normalization of higher levels of tyrosine incorporation in PMN of CHS patients and the inhibition of FMLP-induced stimulation of tubulin tyrosinolation in normal and CHS cells as observed with ascorbate could also be affected by other reducing agents such as reduced glutathione, cysteine, or dithiothreitol. These results suggest a possible relationship between cellular redox and tubulin tyrosinolation in PMN.