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Tubulin Acetylation (tubulin + acetylation)
Selected AbstractsAlcohol-induced alterations in hepatic microtubule dynamics can be explained by impaired histone deacetylase 6 function,HEPATOLOGY, Issue 5 2008Blythe D. Shepard We have been using polarized, hepatic WIF-B cells to examine ethanol-induced liver injury. These cells polarize in culture and maintain numerous liver-specific activities including the ability to metabolize alcohol. Previously, we found that microtubules were more highly acetylated and more stable in ethanol-treated WIF-B cells and that increased microtubule acetylation required ethanol metabolism and was likely mediated by acetaldehyde. This study was aimed at identifying the mechanism responsible for increased microtubule acetylation. We examined the expression of two known microtubule deacetylases, histone deacetylase 6 (HDAC6) and Sirtuin T2 (SirT2), in WIF-B cells. Immunoblotting, immunofluorescence microscopy, and assays using the SirT2 inhibitor nicotinamide revealed that WIF-B cells do not express SirT2. In contrast, HDAC6 was highly expressed in WIF-B cells. Addition of trichostatin A (TSA), an HDAC6 inhibitor, induced microtubule acetylation to the same extent as in ethanol-treated cells (approximately threefold). Although immunofluorescence labeling revealed that HDAC6 distribution did not change in ethanol-treated cells, immunoblotting showed HDAC6 protein levels slightly decreased. HDAC6 solubility was increased in nocodazole-treated cells, suggesting impaired microtubule binding. Direct microtubule binding assays confirmed this hypothesis. The decreased microtubule binding was partially prevented by 4-methyl pyrazole, indicating the effect was in part mediated by acetaldehyde. Interestingly, HDAC6 from ethanol-treated cells was able to bind and deacetylate exogenous tubulin to the same extent as control, suggesting that ethanol-induced tubulin modifications prevented HDAC6 binding to endogenous microtubules. Conclusion: We propose that lower HDAC6 levels combined with decreased microtubule binding lead to increased tubulin acetylation in ethanol-treated cells. (HEPATOLOGY 2008.) [source] Vorinostat increases carboplatin and paclitaxel activity in non-small cell lung cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 3 2010Taofeek K. Owonikoko Abstract We observed a 53% response rate in non-small cell lung cancer (NSCLC) patients treated with vorinostat plus paclitaxel/carboplatin in a Phase I trial. Studies were undertaken to investigate the mechanism (s) underlying this activity. Growth inhibition was assessed in NSCLC cells by MTT assay after 72 hr of continuous drug exposure. Vorinostat (1 ,M) inhibited growth by: 17% ± 7% in A549, 28% ± 6% in 128-88T, 39% ± 8% in Calu1 and 41% ± 7% in 201T cells. Vorinostat addition to carboplatin or paclitaxel led to significantly greater growth inhibition than chemotherapy alone in all 4 cell lines. Vorinostat (1 ,M) synergistically increased the growth inhibitory effects of carboplatin/paclitaxel in 128-88T cells. When colony formation was measured after drug withdrawal, vorinostat significantly increased the effects of carboplatin but not paclitaxel. The % colony formation was control 100%; 1 ,M vorinostat, 83% ± 10%; 5 ,M carboplatin, 41% ± 11%; carboplatin/vorinostat, 8% ± 4%; 2 nM paclitaxel, 53% ± 11%; paclitaxel/vorinostat, 46% ± 21%. In A549 and 128-88T, vorinostat potentiated carboplatin induction of gamma-H2AX (a DNA damage marker) and increased ,-tubulin acetylation (a marker for stabilized mictrotubules). In A549, combination of vorinostat with paclitaxel resulted in a synergistic increase in ,-tubulin acetylation, which reversed upon drug washout. We conclude that vorinostat interacts favorably with carboplatin and paclitaxel in NSCLC cells, which may explain the provocative response observed in our clinical trial. This likely involves a vorinostat-mediated irreversible increase in DNA damage in the case of carboplatin and a reversible increase in microtubule stability in the case of paclitaxel. [source] Tau , an inhibitor of deacetylase HDAC6 functionJOURNAL OF NEUROCHEMISTRY, Issue 6 2009Mar Perez Abstract Analysis of brain microtubule protein from patients with Alzheimer's disease showed decreased alpha tubulin levels along with increased acetylation of the alpha tubulin subunit, mainly in those microtubules from neurons containing neurofibrillary tau pathology. To determine the relationship of tau protein and increased tubulin acetylation, we studied the effect of tau on the acetylation-deacetylation of tubulin. Our results indicate that tau binds to the tubulin-deacetylase, histone deacetylase 6 (HDAC6), decreasing its activity with a consequent increase in tubulin acetylation. As expected, increased acetylation was also found in tubulin from wild-type mice compared with tubulin from mice lacking tau because of the tau-mediated inhibition of the deacetylase. In addition, we found that an excess of tau protein, as a HDAC6 inhibitor, prevents induction of autophagy by inhibiting proteasome function. [source] Molecular Reproduction & Development: Volume 77, Issue 4MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2010Article first published online: 23 FEB 2010 Immunofluorescence image of porcine seminiferous tubule with acetylated alpha tubulin (red), beta tubulin (green) and DNA (blue). See Luo et al. (this issue) for the dynamic profile of reversible tubulin acetylation during spermatogenesis. [source] Curcumin disrupts meiotic and mitotic divisions via spindle impairment and inhibition of CDK1 activityCELL PROLIFERATION, Issue 4 2010A. Bielak-Zmijewska Objectives:, Curcumin, a natural compound, is a potent anti-cancer agent, which inhibits cell division and/or induces cell death. It is believed that normal cells are less sensitive to curcumin than malignant cells; however, the mechanism(s) responsible for curcumin's effect on normal cells are poorly understood. The aim of this study was to verify the hypothesis that curcumin affects normal cell division by influencing microtubule stability, using mouse oocyte and early embryo model systems. Materials and methods:, Maturating mouse oocytes and two-cell embryos were treated with different concentrations of curcumin (10,50 ,m), and meiotic resumption and mitotic cleavage were analysed. Spindle and chromatin structure were visualized using confocal microscopy. In addition, acetylation and in vitro polymerization of tubulin, in the presence of curcumin, were investigated and the damage to double-stranded DNA was studied using ,H2A.X. CDK1 activity was measured. Results and conclusions:, We have shown for the first time, that curcumin, in a dose-dependent manner, delays and partially inhibits meiotic resumption of oocytes and inhibits meiotic and mitotic divisions by causing disruption of spindle structure and does not induce DNA damage. Our analysis indicated that curcumin affects CDK1 kinase activity but does not directly affect microtubule polymerization and tubulin acetylation. As our study showed that curcumin impairs generative and somatic cell division, its future clinical use or of its derivatives with improved bioavailability after oral administration, should take into consideration the possibility of extensive side-effects on normal cells. [source] 2135: Influence of Hsp90 and HDAC inhibition and tubulin acetylation on perinuclear protein aggregation in human retinal pigment epithelial cellsACTA OPHTHALMOLOGICA, Issue 2010K KAARNIRANTA Purpose Retinal pigment epithelial (RPE) cells are continually exposed to oxidative stress that contributes to protein misfolding, aggregation and functional abnormalities during aging. The protein aggregates formed at the cell periphery are delivered along the microtubulus network by dynein dependent retrograde trafficking to a juxtanuclear location. Methods Cellular organelles were analysed by transmission electron microscopy of ARPE-19 cells exposed 5 µM MG-132, 0.25 µM geldanamycin (GA), 1 µM trichostatin A (TSA), 1 µM taxol (TAX) or 5 µM nocodazole (NOC) for 24 hours. In addition, the cells were treated simultaneously with GA or TSA or TAX or NOC and MG-132 up to 24 hours. Ubiquitin, Hsp90, Hsp70, acetylated tubulin and Hsc70 protein levels were analyzed by western blotting. Results Hsp90 inhibition by geldanamycin can effectively suppress proteasome inhibitor, MG-132 ,induced protein aggregation in a way that is an independent of HDAC inhibition, or the tubulin acetylation levels in ARPE-19 cells. However, the tubulin acetylation and polymerization state affects the localization of the proteasome-inhibitor ,induced aggregation. Conclusion Hsp90 inhibition is effectively related to regulation of protein aggregation that is independent of HDAC inhibition or tubulin acetylation levels in the RPE cells. Our findings open new perspectives for understanding the pathogenesis of protein aggregation in retinal cells and can be useful for the development of therapeutic treatments to prevent retinal cell deterioration. [source] | |||||||||||||