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Goldberg AA, Nkengfac B, Sanchez AMJ, Moroz N, Qureshi ST, Koromilas AE, Wang S, Burelle Y, Hussain SN, Kristof AS. Regulation of ULK1 Expression and Autophagy by STAT1. J Biol Chem 2016; 292:1899-1909. [PMID: 28011640 DOI: 10.1074/jbc.m116.771584] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Indexed: 02/02/2023] Open
Abstract
Autophagy involves the lysosomal degradation of cytoplasmic contents for regeneration of anabolic substrates during nutritional or inflammatory stress. Its initiation occurs rapidly after inactivation of the protein kinase mammalian target of rapamycin (mTOR) (or mechanistic target of rapamycin), leading to dephosphorylation of Unc-51-like kinase 1 (ULK1) and autophagosome formation. Recent studies indicate that mTOR can, in parallel, regulate the activity of stress transcription factors, including signal transducer and activator of transcription-1 (STAT1). The current study addresses the role of STAT1 as a transcriptional suppressor of autophagy genes and autophagic activity. We show that STAT1-deficient human fibrosarcoma cells exhibited enhanced autophagic flux as well as its induction by pharmacological inhibition of mTOR. Consistent with enhanced autophagy initiation, ULK1 mRNA and protein levels were increased in STAT1-deficient cells. By chromatin immunoprecipitation, STAT1 bound a putative regulatory sequence in the ULK1 5'-flanking region, the mutation of which increased ULK1 promoter activity, and rendered it unresponsive to mTOR inhibition. Consistent with an anti-apoptotic effect of autophagy, rapamycin-induced apoptosis and cytotoxicity were blocked in STAT1-deficient cells but restored in cells simultaneously exposed to the autophagy inhibitor ammonium chloride. In vivo, skeletal muscle ULK1 mRNA and protein levels as well as autophagic flux were significantly enhanced in STAT1-deficient mice. These results demonstrate a novel mechanism by which STAT1 negatively regulates ULK1 expression and autophagy.
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Affiliation(s)
- Alexander A Goldberg
- From the Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, McGill University, Montreal, Quebec H4A 3J1, Canada
| | - Bernard Nkengfac
- From the Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, McGill University, Montreal, Quebec H4A 3J1, Canada
| | - Anthony M J Sanchez
- From the Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, McGill University, Montreal, Quebec H4A 3J1, Canada
| | - Nikolay Moroz
- From the Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, McGill University, Montreal, Quebec H4A 3J1, Canada
| | - Salman T Qureshi
- From the Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, McGill University, Montreal, Quebec H4A 3J1, Canada
| | - Antonis E Koromilas
- the Lady Davis Institute for Medical Research, McGill University, Sir Mortimer B. Davis-Jewish General Hospital, Montreal, Quebec H3T 1E2, Canada
| | - Shuo Wang
- the Lady Davis Institute for Medical Research, McGill University, Sir Mortimer B. Davis-Jewish General Hospital, Montreal, Quebec H3T 1E2, Canada
| | - Yan Burelle
- Faculty of Pharmacy, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Sabah N Hussain
- From the Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, McGill University, Montreal, Quebec H4A 3J1, Canada
| | - Arnold S Kristof
- From the Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, McGill University, Montreal, Quebec H4A 3J1, Canada.
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Martin E, Harel S, Nkengfac B, Hamiche K, Neault M, Jenna S. pix-1 controls early elongation in parallel with mel-11 and let-502 in Caenorhabditis elegans. PLoS One 2014; 9:e94684. [PMID: 24732978 PMCID: PMC3986101 DOI: 10.1371/journal.pone.0094684] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 03/17/2014] [Indexed: 12/17/2022] Open
Abstract
Cell shape changes are crucial for metazoan development. During Caenorhabditis elegans embryogenesis, epidermal cell shape changes transform ovoid embryos into vermiform larvae. This process is divided into two phases: early and late elongation. Early elongation involves the contraction of filamentous actin bundles by phosphorylated non-muscle myosin in a subset of epidermal (hypodermal) cells. The genes controlling early elongation are associated with two parallel pathways. The first one involves the rho-1/RHOA-specific effector let-502/Rho-kinase and mel-11/myosin phosphatase regulatory subunit. The second pathway involves the CDC42/RAC-specific effector pak-1. Late elongation is driven by mechanotransduction in ventral and dorsal hypodermal cells in response to body-wall muscle contractions, and involves the CDC42/RAC-specific Guanine-nucleotide Exchange Factor (GEF) pix-1, the GTPase ced-10/RAC and pak-1. In this study, pix-1 is shown to control early elongation in parallel with let-502/mel-11, as previously shown for pak-1. We show that pix-1, pak-1 and let-502 control the rate of elongation, and the antero-posterior morphology of the embryos. In particular, pix-1 and pak-1 are shown to control head, but not tail width, while let-502 controls both head and tail width. This suggests that let-502 function is required throughout the antero-posterior axis of the embryo during early elongation, while pix-1/pak-1 function may be mostly required in the anterior part of the embryo. Supporting this hypothesis we show that low pix-1 expression level in the dorsal-posterior hypodermal cells is required to ensure high elongation rate during early elongation.
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Affiliation(s)
- Emmanuel Martin
- Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada
| | - Sharon Harel
- Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada
| | - Bernard Nkengfac
- Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada
| | - Karim Hamiche
- Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada
| | - Mathieu Neault
- Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada
| | - Sarah Jenna
- Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada
- * E-mail:
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Abstract
OBJECTIVE To evaluate the effects of physiological levels of mitochondrial-derived reactive oxygen species (ROS) on skeletal muscle autophagy, a proteolytic pathway designed to regulate contractile and myofilament homeostasis and to recycle long-lived proteins and damaged organelles. RESULTS Basal levels of autophagy and autophagy triggered by 1.5 to 4 h of acute nutrient deprivation, rapamycin treatment, or leucine deprivation were measured in differentiated C2C12 myotubes using long-lived protein degradation assays, LC3B lipidation, autophagy-related gene expression, and electron microscopy. Preincubation with the general antioxidants tempol (superoxide dismutase mimic) and N-acetyl cysteine (NAC) or the mitochondria-specific antioxidants mito-tempol and SS31 significantly decreased the rates of long-lived protein degradation and LC3B flux and blocked the induction of autophagy-related gene expression. Mitochondrial ROS levels significantly increased in response to acute nutrient deprivation and rapamycin treatment. Mito-tempol and tempol blocked this response. Antioxidants decreased AMP-activated protein kinase (AMPK) phosphorylation by 40% and significantly increased protein kinase B (AKT) phosphorylation, but exerted no effects on mTORC1-dependent ULK1 phosphorylation on Ser(555). NAC significantly decreased basal LC3B autophagic flux in skeletal muscles of mice. INNOVATION We report for the first time that endogenous ROS promote skeletal muscle autophagy at the basal level and in response to acute nutrient starvation and mTORC1 inhibition. We also report for the first time that mitochondrial-derived ROS promote skeletal muscle autophagy and that this effect is mediated, in part, through regulation of autophagosome initiation and AKT inhibition. CONCLUSION Mitochondrial-derived ROS promote skeletal muscle autophagy and this effect is mediated, in part, through activation of AMPK and inhibition of AKT.
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Affiliation(s)
- Mashrur Rahman
- 1 Department of Critical Care, McGill University Health Centre and Meakins-Christie Laboratories , Montréal, Canada
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Nkengfac B, Pouyez J, Bauwens E, Vandenhaute J, Letesson JJ, Wouters J, De Bolle X. Structural analysis of Brucella abortus RicA substitutions that do not impair interaction with human Rab2 GTPase. BMC Biochem 2012; 13:16. [PMID: 22892012 PMCID: PMC3527289 DOI: 10.1186/1471-2091-13-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 07/30/2012] [Indexed: 01/18/2023]
Abstract
Background Protein-protein interactions are at the basis of many cellular processes, and they are also involved in the interaction between pathogens and their host(s). Many intracellular pathogenic bacteria translocate proteins called effectors into the cytoplasm of the infected host cell, and these effectors can interact with one or several host protein(s). An effector named RicA was recently reported in Brucella abortus to specifically interact with human Rab2 and to affect intracellular trafficking of this pathogen. Results In order to identify regions of the RicA protein involved in the interaction with Rab2, RicA was subjected to extensive random mutagenesis using error prone polymerase chain reaction. The resulting allele library was selected by the yeast two-hybrid assay for Rab2-interacting clones that were isolated and sequenced, following the “absence of interference” approach. A tridimensional model of RicA structure was used to position the substitutions that did not affect RicA-Rab2 interaction, giving a “negative image” of the putative interaction region. Since RicA is a bacterial conserved protein, RicA homologs were also tested against Rab2 in a yeast two-hybrid assay, and the C. crescentus homolog of RicA was found to interact with human Rab2. Analysis of the RicA structural model suggested that regions involved in the folding of the “beta helix” or an exposed loop with the IGFP sequence could also be involved in the interaction with Rab2. Extensive mutagenesis of the IGFP loop suggested that loss of interaction with Rab2 was correlated with insolubility of the mutated RicA, showing that “absence of interference” approach also generates surfaces that could be necessary for folding. Conclusion Extensive analysis of substitutions in RicA unveiled two structural elements on the surface of RicA, the most exposed β-sheet and the IGFP loop, which could be involved in the interaction with Rab2 and protein folding. Our analysis of mutants in the IGFP loop suggests that, at least for some mono-domain proteins such as RicA, protein interaction analysis using allele libraries could be complicated by the dual effect of many substitutions affecting both folding and protein-protein interaction.
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Affiliation(s)
- Bernard Nkengfac
- Molecular Biology Research Unit (URBM), Narilis, University of Namur, 61 Rue Bruxelles, Namur, B-5000, Belgium
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de Barsy M, Jamet A, Filopon D, Nicolas C, Laloux G, Rual JF, Muller A, Twizere JC, Nkengfac B, Vandenhaute J, Hill DE, Salcedo SP, Gorvel JP, Letesson JJ, De Bolle X. Identification of a Brucella spp. secreted effector specifically interacting with human small GTPase Rab2. Cell Microbiol 2011; 13:1044-58. [PMID: 21501366 DOI: 10.1111/j.1462-5822.2011.01601.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Bacteria of the Brucella genus are facultative intracellular class III pathogens. These bacteria are able to control the intracellular trafficking of their vacuole, presumably by the use of yet unknown translocated effectors. To identify such effectors, we used a high-throughput yeast two-hybrid screen to identify interactions between putative human phagosomal proteins and predicted Brucella spp. proteins. We identified a specific interaction between the human small GTPase Rab2 and a Brucella spp. protein named RicA. This interaction was confirmed by GST-pull-down with the GDP-bound form of Rab2. A TEM-β-lactamase-RicA fusion was translocated from Brucella abortus to RAW264.7 macrophages during infection. This translocation was not detectable in a strain deleted for the virB operon, coding for the type IV secretion system. However, RicA secretion in a bacteriological culture was still observed in a ΔvirB mutant. In HeLa cells, a ΔricA mutant recruits less GTP-locked myc-Rab2 on its Brucella-containing vacuoles, compared with the wild-type strain. We observed altered kinetics of intracellular trafficking and faster proliferation of the B. abortusΔricA mutant in HeLa cells, compared with the wild-type control. Altogether, the data reported here suggest RicA as the first reported effector with a proposed function for B. abortus.
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