Promotion of microtubule acetylation plays an important role in degranulation of antigen-activated mast cells

The aim of this study was to investigate whether microtubule acetylation is triggered by antigen stimulation and how it affects mast cell degranulation. The RBL-2H3 cell line was used as a model for mast cells. Acetylation of α-tubulin was analyzed by Western blotting. Intracellular distribution of α-tubulin and acetylated α-tubulin was observed by immunostaining. Degranulation was monitored by measuring the activity of β-hexosaminidase secreted into cell supernatants. Tukey–Kramer test was used to compare differences between groups. Microtubule acetylation proceeds globally in mast cell cytoplasm after antigen stimulation in addition to accelerated formation of microtubule-organizing centers. Pretreatment with 5Z-7-oxozeaenol (5 µmol/l), an inhibitor of TGF-β-activated kinase 1, which is a key activator of α-tubulin acetyltransferase 1, did not affect the distribution and acetylation of microtubules in resting cells; however, it significantly suppressed antigen-evoked microtubule acetylation and their reorganization, and subsequent degranulation (95.0 ± 1.2% inhibition, n = 3, P < 0.01). These results provided new insight into the post-translational modifications of microtubule to regulate mast cell degranulation.