Gene regulation in autophagy and apoptosis juncture
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ABSTRACT: Autophagy to apoptosis switching event is an unexplored area. We were interested to explore the gene expression profile at this juncture. Our Microarray data emphasized that among all eNOS and p62 genes were markedly induced. In fuctional level eNOS expression activates mTORC1 followed by inhibition of autophagy. This ultimately allowed accumulation of p62 . Intraccellular accumulation of p62 sequestered unfolded toxic protein aggregates in mitochondria and ER resulting in to impaired redox regulation. Intraccelular ROS generation further sensitized cells for apoptosis and tilted autophagic response to apoptosis. Cells were treated with Tunicamycin as an inducer of both autophagy and apoptosis. At early stage of Tunicamycin treatment 24h , prostate cancer cell PC3 showed activation of autophagic process where apoptosis was not evident. Sustained ER stress with Tunicamycin induced late apoptoisis at 72h of treatment. Hence we isolated total RNA from Untreated cells, cells with Tunicamycin treatment after 24h and 72h. Further the RNA were used to perform whole genome microarray to analyze the gene expression profile at autophagy and apoptosis juncture. The selected genes were also validated by qPCR and western bot. Morover RNAi study were implemented to evaluate the signaling crosstalk at the juncture of autophagy and apoptosis.
Project description:Autophagy to apoptosis switching event is an unexplored area. We were interested to explore the gene expression profile at this juncture. Our Microarray data emphasized that among all eNOS and p62 genes were markedly induced. In fuctional level eNOS expression activates mTORC1 followed by inhibition of autophagy. This ultimately allowed accumulation of p62 . Intraccellular accumulation of p62 sequestered unfolded toxic protein aggregates in mitochondria and ER resulting in to impaired redox regulation. Intraccelular ROS generation further sensitized cells for apoptosis and tilted autophagic response to apoptosis.
Project description:Huntington's disease (HD) is a dominantly inherited genetic disease caused by mutant huntingtin (htt) protein with expanded polyglutamine tracts. A neuropathological hallmark of HD is the presence of neuronal inclusions of mutant htt. p62 is an important regulatory protein in selective autophagy, a process by which aggregated proteins are degraded, and it is associated with several neurodegenerative disorders including HD. Here we investigated the effect of p62 depletion in three HD model mice: R6/2, HD190QG and HD120QG mice. We found that loss of p62 in these models led to longer lifespans and reduced nuclear inclusions, although cytoplasmic inclusions increased with polyglutamine length. In mouse embryonic fibroblasts (MEFs) with or without p62, mutant htt with a nuclear localization signal (NLS) showed no difference in nuclear inclusion between the two MEF types. In the case of mutant htt without NLS, however, p62 depletion increased cytoplasmic inclusions. Furthermore, to examine the effect of impaired autophagy in HD model mice, we crossed R6/2 mice with Atg5 conditional knockout mice. These mice also showed decreased nuclear inclusions and increased cytoplasmic inclusions, similar to HD mice lacking p62. These data suggest that the genetic ablation of p62 in HD model mice enhances cytoplasmic inclusion formation by interrupting autophagic clearance of polyQ inclusions. This reduces polyQ nuclear influx and paradoxically ameliorates disease phenotypes by decreasing toxic nuclear inclusions. Gene expression profiles were analyzed to examine the effects of p62 depletion in mouse with or without mutant huntingtin exon 1 To examine the effect of p62 depletion on the transcriptome of Huntington's disease model mice, we crossed p62 knockout mice with HD model mice. We extracted total RNA from the striatum of these mice at 8 weeks and used for a microaaray analysis. The samples are HD transgenic mice with p62 knockout (HD_p62KO), HD mice with normal p62 (HD_p62WT), non-HD-transgenic mice with p62 knockout (NT_p62KO), and non-HD-transgenic mice with normal p62 (NT_p62WT).
Project description:Glioblastoma (GBM) carries a dismal prognosis largely due to acquired resistance to the standard treatment, which incorporates the chemotherapy temozolomide (TMZ). Inhibiting the proteasomal pathway is an emerging strategy, where combination treatments are under clinical investigation. We hypothesized that pre-treatment of GBM with bortezomib (BTZ) might sensitize glioblastoma to TMZ by abolishing autophagy survival signals to augment DNA damage and apoptosis. P3 patient-derived GBM cells as well as the tumor cell lines U87, HF66, A172 and T98G were investigated for clonogenic survival after single or combined treatment with TMZ and BTZ in vitro. Change in autophagic flux was examined after experimental treatments in conjunction with inhibitors of autophagy or downregulation of autophagy-related genes -5 and -7 (ATG5 and ATG7, respectively). Autophagic flux was increased in TMZ-resistant P3 and T98G cells as indicated by diminished levels of the autophagy markers LC3A/B-II and increased STX17, higher protein degradation and no formation of p62 bodies nor induction of apoptosis. In contrast, BTZ treatment attenuated ULK1 mRNA, total and phosphorylated protein, and accumulated LC3A/B-II, p62 and autophagosomes analogously to Baf1 and chloroquine autophagy inhibitors. These autophagosomes did not fuse with lysosomes, indicated by attenuated STX17 expression and reduced degradation of long-lived proteins, which culminated in enhanced caspase-3/8 dependent apoptosis. BTZ synergistically enhanced TMZ efficacy, attenuated tumor cell proliferation, triggered ATM/Chk2 DNA damage signalling to further augment caspase-3/8 mediated apoptosis in the TMZ resistant P3 and T98G GBM cells. Genetic or chemical inhibition of autophagy (with CRISPR-CAs9 ATG5, ATG7 shRNA, MRT68921 or VPS34-IN1) abrogated BTZ efficacy and rescued BTZ+ TMZ treated GBM cells from death. We conclude that Bortezomib ameliorates temozolomide resistance through ATG5/7-dependent abrogated autophagic flux and may be amenable in combination treatment regimens for TMZ refractory GBM patients.
Project description:Age-related cell loss underpins many senescence-associated diseases. Senile cataract is a primary blindness-causing age-related ocular disease. Apoptosis of lens epithelial cells (LECs) is the common cellular basis of senile cataract resulted from prolonged exposure to oxidative stress, the mechanism of which remains elusive. Here we reported the concomitance of increased autophagy and apoptosis in the same LEC from senile cataract patients. Oxidative stress triggered autophagy preceded apoptosis, while blocking autophagy by ablation of Atg7 or Atg3 gene remarkably suppressed apoptosis in HLE-B3 cell line. We identified autophagy adaptor SQSTM1/p62 as the critical scaffold protein to sustain a pro-survival signaling PKCι-NF-κB cascades, which antagonized the pro-apoptotic signaling in LECs. Importantly, prolonged autophagy in human senescent LECs responding to oxidative stress induced extensive degradation of p62 protein and therefore facilitated apoptosis. Moreover, pharmacological inhibitor of autophagy, 3-MA, significantly rescued apoptosis of human senescent LECs challenged by oxidative stress. Collectively, our data demonstrated that hyperactivation of autophagy aggravates age-related apoptotic cell death via inhibiting the p62-PKCι-NF-κB pro-survival axis in human senescent LECs. This work expands the understanding of the etiology of senile cataract and provides insight for mechanisms of age-related cell death in senescence-associated diseases.
Project description:Miz1 is a zinc finger protein that regulates expression of cell cycle inhibitors as part of a complex with Myc. Cell cycle-independent functions of Miz1 are poorly understood. Here, we use a Nestin-Cre transgene to delete an essential domain of Miz1 in the central nervous system (Miz1M-NM-^TPOZNes). Miz1M-NM-^TPOZNes mice display cerebellar neurodegeneration characterized by the progressive loss of Purkinje cells. Chromatin immunoprecipitation sequencing and biochemical analyses show that Miz1 activates transcription upon binding to a non-palindromic sequence present in core promoters. Target genes of Miz1 encode regulators of autophagy and proteins involved in vesicular transport that are required for autophagy. Miz1M-NM-^TPOZ neuronal progenitors and fibroblasts show reduced autophagic flux. Consistently, polyubiquitinated proteins and p62/Sqtm1 accumulate in the cerebella of Miz1M-NM-^TPOZNes mice, characteristic features of defective autophagy. Our data suggest that Miz1 may link cell growth and ribosome biogenesis to the transcriptional regulation of vesicular transport and autophagy. ChIP-Seq with H190 and G18 on an Illumina Genome Analyzer IIx.
Project description:Epigenetic factors and related small molecules have emerged to be strongly involved in autophagy process. Here we report that two inhibitors of histone H3K4 demethylase KDM1A/LSD1, 2-PCPA and GSK-LSD1, are able to induce autophagy in multiple cell lines. The two small molecules induced accumulation of LC3II, formation of autophagosome, fusion of autophagosome with lysosome and SQSTM1/p62 degradation. 2-PCPA treatment inhibits cell proliferation through cell cycle arrest but not inducing cell death. Exogenous expression of KDM1A/LSD1 impaired the autophagic phenotypes triggered by 2-PCPA. The autophagy induced by 2-PCPA requires LC3-II processing machinery. But depletion of BECN1 and ULK1 with siRNA did not affect the LC3-II accumulation triggered by 2-PCPA. 2-PCPA treatment induces the change of global gene expression program, including a series of autophagy-related genes, such as SQSTM1/p62. Taken together, our data indicate that KDM1A/LSD1 inhibitors induce autophagy through affecting the expression of autophagy-related genes and in a BECN1-independent manner.
Project description:Autophagy plays important roles in malignant pathogenesis and drug resistance. We used medicinal chemistry approaches to generate a series of novel agents that inhibit autophagic degradation. ROC-325 was selected as a lead compound for further evaluation. Comprehensive in vitro and in vivo studies were conducted to evaluate the selectivity, tolerability, and efficacy of ROC-325 in preclinical models of renal cell carcinoma (RCC). ROC-325 exhibited superior in vitro anticancer effects than the existing autophagy inhibitor hydroxychloroquine in 12 different tumor models with diverse genetic backgrounds. Focused studies of the mechanism of action and efficacy of ROC-325 in RCC cells showed that drug treatment induced hallmark characteristics of autophagy inhibition including accumulation of autophagosomes with undegraded cargo, lysosomal deacidification, p62 stabilization, and disruption of autophagic flux. Subsequent experiments showed that ROC-325 antagonized RCC growth and survival in an ATG5/7-dependent manner, induced apoptosis, and exhibited favorable selectivity. Oral administration of ROC-325 to mice bearing 786-0 RCC xenografts was well tolerated, significantly more effective at inhibiting tumor progression than HCQ, and inhibited autophagy in vivo. We used microarrays to determine gene expression changes following 24 h treatment with ROC-325 in RCC cell lines and identified differentially expressed genes.
Project description:Background Transforming growth factor β1 (TGF-β1) has a neuroprotective function in traumatic brain injury (TBI) through its anti-inflammatory and immunomodulatory properties. In our previous study, we found that TGF-β1 played a critical role in inhibiting apoptosis and increasing neuronal activity in murine cortical neurons following trauma. However, the precise mechanisms underlying the neuroprotective actions of TGF-β1 on the cortex require further investigation. Methods Thus, in this study, we were aimed to investigate the regulatory function of TGF-β1 on neuronal autophagy and apoptosis using an in vitro primary cortical neuron trauma-injury model. Results To establish the landscape of differentially expressed genes (DEGs) with or without TGF-β1 (10ng/ml) treatment for 24 hours, we performed RNA-sequencing. We observed significant enrichment of DEGs related to autophagy, apoptosis, and the lysosome pathway in trauma-injured cortical neurons. Additionally, transmission electron microscopy (TEM) confirmed the presence of autophagosomes as well as autophagolysosomes. Western blot analysis revealed upregulation of autophagy-related protein light chain 3 (LC3)-Ⅱ/LC3-Ⅰ, sequestosome 1 (SQSTM1)/p62, along with apoptosis-related protein Cleaved-caspase3 in trauma-injured primary cortical neurons. Furthermore, mechanically injured neurons showed an upregulation of lysosomal marker protein lysosomal marker protein (LAMP1) and lysosomal enzyme mature cathepsin D (mCTSD), but a decrease in the activity of CTSD enzyme. These results indicated that apoptosis was up-regulated in mechanically injured neurons at 24 hours, accompanied by lysosomal dysfunction and impaired autophagic flux. Notably, TGF-β1 significantly reversed these changes. Conclusions Therefore, our findings suggested that TGF-β1 exerted neuroprotective effects on mechanically injured neurons by reducing lysosomal dysfunction, decreasing the accumulation of autophagosomes and autophagolysosomes, and enhancing autophagic flux.
Project description:Huntington’s disease (HD) is a dominantly inherited genetic disease caused by mutant huntingtin (htt) protein with expanded polyglutamine tracts. A neuropathological hallmark of HD is the presence of neuronal inclusions of mutant htt. p62 is an important regulatory protein in selective autophagy, a process by which aggregated proteins are degraded, and it is associated with several neurodegenerative disorders including HD. Here we investigated the effect of p62 depletion in three HD model mice: R6/2, HD190QG and HD120QG mice. We found that loss of p62 in these models led to longer lifespans and reduced nuclear inclusions, although cytoplasmic inclusions increased with polyglutamine length. In mouse embryonic fibroblasts (MEFs) with or without p62, mutant htt with a nuclear localization signal (NLS) showed no difference in nuclear inclusion between the two MEF types. In the case of mutant htt without NLS, however, p62 depletion increased cytoplasmic inclusions. Furthermore, to examine the effect of impaired autophagy in HD model mice, we crossed R6/2 mice with Atg5 conditional knockout mice. These mice also showed decreased nuclear inclusions and increased cytoplasmic inclusions, similar to HD mice lacking p62. These data suggest that the genetic ablation of p62 in HD model mice enhances cytoplasmic inclusion formation by interrupting autophagic clearance of polyQ inclusions. This reduces polyQ nuclear influx and paradoxically ameliorates disease phenotypes by decreasing toxic nuclear inclusions. Gene expression profiles were analyzed to examine the effects of p62 depletion in mouse with or without mutant huntingtin exon 1