The dual functions of α-tubulin acetylation in cellular apoptosis and autophage induced by tanespimycin in lung cancer cells

BACKGROUND: Reversible acetylation of α-tubulin has been implicated in modulating microtuble structures and functions, which may subsequently involve in cellular apoptosis and autophage. But how to trigger apoptosis or autophage at what level of acetylated α-tubulin (Ac-α-tubulin) are not known. This study aims to demonstrate the dual functions and molecular mechanisms of α-tubulin acetylation in cellular apoptosis and autophage induced by tanespimycin in Calu-1 cells simultaneously. METHODS: Calu-1 cells were treated with tanespimycin alone or combined administrations of different agents (including TSA, Docetaxel, Rapamycin, 3-MA and Z-vad) respectively and cell lysates were prepared to detect the given proteins by Western Blot. The cell survival was observed by inverted phase contrast microscope and estimated by SRB assay. HDAC6, TAT1 and Hsp90α/β proteins were knocked down by siRNA technique. RESULTS: By combination administration of tanespimycin with TSA or Docetaxel, the expression of Ac-α-tubulin and cellular apoptosis were enhanced markedly. While combination of tanespimycin and Rapamycin, α-tubulin acetylation and apoptosis were inhibited, but LC3B-II expression was facilitated substantially. When tanespimycin was combined with autophage inhibitor 3-MA, α-tubulin acetylation elevation was apparently, but LC3B-II was attenuated. Apoptosis inhibitor Z-vad blocked partially Caspases activation induced by tanespimycin, but failed to hinder α-tubulin acetylation elevation. According to results of RNA interference, acetyltransferase TAT1, deacetylase HDAC6 and Hsp90 modulated the expression level of α-tubulin acetylation. CONCLUSION: We have elucidated that acetylation of α-tubulin induced by tanespimycin has dual functions in cellular apoptosis and autophage and the level of α-tubulin acetylation reaches a degree Calu-1 cells undergo cell apoptosis rather than autophage, implying that the level of acetylated α-tubulin may determine cell fate for survival or apoptosis.