Heat shock protein 70-mediated sensitization of cells to apoptosis by Carboxyl-Terminal Modulator Protein

<p>Abstract</p> <p>Background</p> <p>The serine/threonine protein kinase B (PKB/Akt) is involved in insulin signaling, cellular survival, and transformation. Carboxyl-terminal modulator protein (CTMP) has been identified as a novel PKB binding partner in a yeast two-hybrid screen, and appears to be a negative PKB regulator with tumor suppressor-like properties. In the present study we investigate novel mechanisms by which CTMP plays a role in apoptosis process.</p> <p>Results</p> <p>CTMP is localized to mitochondria. Furthermore, CTMP becomes phosphorylated following the treatment of cells with pervanadate, an insulin-mimetic. Two serine residues (Ser37 and Ser38) were identified as novel <it>in vivo </it>phosphorylation sites of CTMP. Association of CTMP and heat shock protein 70 (Hsp70) inhibits the formation of complexes containing apoptotic protease activating factor 1 and Hsp70. Overexpression of CTMP increased the sensitivity of cells to apoptosis, most likely due to the inhibition of Hsp70 function.</p> <p>Conclusion</p> <p>Our data suggest that phosphorylation on Ser37/Ser38 of CTMP is important for the prevention of mitochondrial localization of CTMP, eventually leading to cell death by binding to Hsp70. In addition to its role in PKB inhibition, CTMP may therefore play a key role in mitochondria-mediated apoptosis by localizing to mitochondria.</p

DJ-1 Null Dopaminergic Neuronal Cells Exhibit Defects in Mitochondrial Function and Structure: Involvement of Mitochondrial Complex I Assembly

DJ-1 is a Parkinson's disease-associated gene whose protein product has a protective role in cellular homeostasis by removing cytosolic reactive oxygen species and maintaining mitochondrial function. However, it is not clear how DJ-1 regulates mitochondrial function and why mitochondrial dysfunction is induced by DJ-1 deficiency. In a previous study we showed that DJ-1 null dopaminergic neuronal cells exhibit defective mitochondrial respiratory chain complex I activity. In the present article we investigated the role of DJ-1 in complex I formation by using blue native-polyacrylamide gel electrophoresis and 2-dimensional gel analysis to assess native complex status. On the basis of these experiments, we concluded that DJ-1 null cells have a defect in the assembly of complex I. Concomitant with abnormal complex I formation, DJ-1 null cells show defective supercomplex formation. It is known that aberrant formation of the supercomplex impairs the flow of electrons through the channels between respiratory chain complexes, resulting in mitochondrial dysfunction. We took two approaches to study these mitochondrial defects. The first approach assessed the structural defect by using both confocal microscopy with MitoTracker staining and electron microscopy. The second approach assessed the functional defect by measuring ATP production, O2 consumption, and mitochondrial membrane potential. Finally, we showed that the assembly defect as well as the structural and functional abnormalities in DJ-1 null cells could be reversed by adenovirus-mediated overexpression of DJ-1, demonstrating the specificity of DJ-1 on these mitochondrial properties. These mitochondrial defects induced by DJ-1mutation may be a pathological mechanism for the degeneration of dopaminergic neurons in Parkinson's disease

Docosahexaenoic acid suppresses breast cancer cell metastasis by targeting matrix-metalloproteinases

Breast cancer is one of the most prevalent cancers in women, and nearly half of breast cancer patients develop distant metastatic disease after therapy. Despite the significant advances that have been achieved in understanding breast cancer metastasis in the past decades, metastatic cancer is still hard to cure. Here, we demonstrated an anti-cancer mechanism of docosahexaenoic acid (DHA) that suppressed lung metastasis in breast cancer. DHA could inhibit proliferation and invasion of breast cancer cells in vitro, and this was mainly through blocking Cox-2-PGE 2 -NF-kappa B-MMPs cascades. DHA treatment significantly decreased Cox-2 and NF-kappa B expression as well as nuclear translocation of NF-kappa B in MDA-MB-231 cells. In addition, DHA also reduced NF-kappa B binding to DNA which may lead to inactivation of MMPs. Moreover, in vivo studies using Fat-1 transgenic mice showed remarkable decrease of tumor growth and metastasis to EO771 cells to lung in DHA-rich environment. In conclusion, DHA attenuated breast cancer progression and lung metastasis in part through suppressing MMPs, and these findings suggest chemoprevention and potential therapeutic strategy to overcome malignant breast cancer.119sciescopu

Docosahexaenoic Acid Induces Cell Death in Human Non-Small Cell Lung Cancer Cells by Repressing mTOR via AMPK Activation and PI3K/Akt Inhibition

The anticancer properties and mechanism of action of omega-3 polyunsaturated fatty acids (ω3-PUFAs) have been demonstrated in several cancers; however, the mechanism in lung cancer remains unclear. Here, we show that docosahexaenoic acid (DHA), a ω3-PUFA, induced apoptosis and autophagy in non-small cell lung cancer (NSCLC) cells. DHA-induced cell death was accompanied by AMP-activated protein kinase (AMPK) activation and inactivated phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling. Knocking down AMPK and overexpressing Akt increased mTOR activity and attenuated DHA-induced cell death, suggesting that DHA induces cell death via AMPK- and Akt-regulated mTOR inactivation. This was confirmed in Fat-1 transgenic mice, which produce ω3-PUFAs. Lewis lung cancer (LLC) tumor cells implanted into Fat-1 mice showed slower growth, lower phospho-Akt levels, and higher levels of apoptosis and autophagy than cells implanted into wild-type mice. Taken together, these data suggest that DHA-induced apoptosis and autophagy in NSCLC cells are associated with AMPK activation and PI3K/Akt inhibition, which in turn lead to suppression of mTOR; thus ω3-PUFAs may be utilized as potential therapeutic agents for NSCLC treatment

PMA synergistically enhances apicularen A-induced cytotoxicity by disrupting microtubule networks in HeLa cells

Background: Combination therapy is key to improving cancer treatment efficacy. Phorbol 12-myristate 13-acetate (PMA), a well-known PKC activator, increases the cytotoxicity of several anticancer drugs. Apicularen A induces cytotoxicity in tumor cells through disrupting microtubule networks by tubulin down-regulation. In this study, we examined whether PMA increases apicularen A-induced cytotoxicity in HeLa cells. Methods: Cell viability was examined by thiazolyl blue tetrazolium (MTT) assays. To investigate apoptotic potential of apicularen A, DNA fragmentation assays were performed followed by extracting genomic DNA, and caspase-3 activity assays were performed by fluorescence assays using fluorogenic substrate. The cell cycle distribution induced by combination with PMA and apicularen A was examined by flow cytometry after staining with propidium iodide (PI). The expression levels of target proteins were measured by Western blotting analysis using specific antibodies, and alpha-tubulin mRNA levels were assessed by reverse transcription polymerase chain reaction (RT-PCR). To examine the effect of combination of PMA and apicularen A on the microtubule architecture, alpha-tubulin protein and nuclei were visualized by immunofluorescence staining using an anti-alpha-tubulin antibody and PI, respectively. Results: We found that apicularen A induced caspase-dependent apoptosis in HeLa cells. PMA synergistically increased cytotoxicity and apoptotic sub-G1 population induced by apicularen A. These effects were completely blocked by the PKC inhibitors Ro31-8220 and Go6983, while caspase inhibition by Z-VAD-fmk did not prevent cytotoxicity. RNA interference using siRNA against PKC alpha, but not PKC beta and PKC gamma, inhibited cytotoxicity induced by combination PMA and apicularen A. PMA increased the apicularen A-induced disruption of microtubule networks by further decreasing alpha- and beta-tubulin protein levels in a PKC-dependent manner. Conclusions: These results suggest that the synergy between PMA and apicularen A is involved by PKC alpha activation and microtubule disruption, and that may inform the development of novel approaches to treat cancer.112sciescopu

Rottlerin induces autophagy and apoptotic cell death through a PKC-delta-independent pathway in HT1080 human fibrosarcoma cells

Rottlerin is widely used as a protein kinase C-delta inhibitor. Recently, several reports have shown the possible apoptosis-inducing effect of rottlerin in some cancer cell lines. Here we report that rottlerin induces not only apoptosis but also autophagy via a PKC-delta-independent pathway in HT1080 human fibrosarcoma cells. Rottlerin treatment induced a dose- and time-dependent inhibition of cell growth, and cytoplasmic vacuolations were markedly shown. These vacuoles were identified as acidic autolysosomes by electron microscopy, acidic vesicular organelle (AVO) staining and transfection of green fluorescent protein-LC3. The LC3-II protein level also increased after treatment with rottlerin. Prolonged exposure to rottlerin eventually caused apoptosis via loss of mitochondrial membrane potential and translocation of AIF from mitochondria to the nucleus. However, the activities of caspase-3, -8 and -9 were not changed, and PARP did not show signs of cleavage. Interestingly, the pretreatment of cells with a specific inhibitor of autophagy (3-methyladenine) accelerated rottlerin-induced apoptosis as revealed by an analysis of the subdiploid fraction and TUNEL assay. Nevertheless, the knockdown of PKC-delta by RNA interference neither affected cell growth nor acidic vacuole formation. Similarly, rottlerin-induced cell death was not prevented by PKC-delta overexpression. Taken together, these findings suggest that rottlerin induces early autophagy and late apoptosis in a PKC-delta-independent manner, and the rottlerin-induced early autophagy may act as a survival mechanism against late apoptosis in HT1080 human fibrosarcoma cells.1137sciescopu

The Omega-3 Polyunsaturated Fatty Acid DHA Induces Simultaneous Apoptosis and Autophagy via Mitochondrial ROS-Mediated Akt-mTOR Signaling in Prostate Cancer Cells Expressing Mutant p53

Docosahexaenoic acid (DHA) induces autophagy-associated apoptotic cell death in wild-type p53 cancer cells via regulation of p53. The present study investigated the effects of DHA on PC3 and DU145 prostate cancer cell lines harboring mutant p53. Results show that, in addition to apoptosis, DHA increased the expression levels of lipidated form LC3B and potently stimulated the autophagic flux, suggesting that DHA induces both autophagy and apoptosis in cancer cells expressing mutant p53. DHA led to the generation of mitochondrial reactive oxygen species (ROS), as shown by the mitochondrial ROS-specific probe mitoSOX. Similarly, pretreatment with the antioxidant N-acetyl-cysteine (NAC) markedly inhibited both the autophagy and the apoptosis triggered by DHA, indicating that mitochondrial ROS mediate the cytotoxicity of DHA in mutant p53 cells. Further, DHA reduced the levels of phospho-Akt and phospho-mTOR in a concentration-dependent manner, while NAC almost completely blocked that effect. Collectively, these findings present a novel mechanism of ROS-regulated apoptosis and autophagy that involves Akt-mTOR signaling in prostate cancer cells with mutant p53 exposed to DHA

Apicularen A acetate induced cell death via AIF translocation and disrupts the microtubule network by down-regulating tubulin in HM7 human colon cancer cells

Apicularen A is a novel antitumor agent and strongly induces death in tumor cells. In this study, we synthesized apicularen A acetate, an acetyl derivative of apicularen A, and investigated its antitumor effect and mechanism in HM7 colon cancer cells. Apicularen A acetate induced apoptotic cell death and caspase-3 activation; however, the pan-caspase inhibitor Z-VAD-fmk could not prevent this cell death. Apicularen A acetate induced the loss of mitochondrial membrane potential and the translocation of apoptosis-inducing factor (AIF) from mitochondria. In addition, apicularen A acetate significantly decreased tubulin mRNA and protein levels and induced disruption of microtubule networks. Taken together, these results indicate that the mechanism of apicularen A acetate involves caspase-independent apoptotic cell death and disruption of microtubule architecture. (C) 2013 Elsevier Inc. All rights reserved.112sciescopu