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Gunn NJ, Kidd SP, Solomon LB, Yang D, Roscioli E, Atkins GJ. Staphylococcus aureus persistence in osteocytes: weathering the storm of antibiotics and autophagy/xenophagy. Front Cell Infect Microbiol 2024; 14:1403289. [PMID: 38915921 PMCID: PMC11194354 DOI: 10.3389/fcimb.2024.1403289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 05/17/2024] [Indexed: 06/26/2024] Open
Abstract
Staphylococcus aureus is a major causative pathogen of osteomyelitis. Intracellular infections of resident bone cells including osteocytes can persist despite gold-standard clinical intervention. The mechanisms by which intracellular S. aureus evades antibiotic therapy are unknown. In this study, we utilised an in vitro S. aureus infection model of human osteocytes to investigate whether antibiotic-mediated dysregulation of autophagy contributes to this phenomenon. Infected or non-infected osteocyte-like cells were exposed to combinations of rifampicin, vancomycin, and modulators of autophagy. Intracellular bacterial growth characteristics were assessed using colony-forming unit (CFU) analysis, viable bacterial DNA abundance, and the rate of escape into antibiotic-free medium, together with measures of autophagic flux. Rifampicin, alone or in combination with vancomycin, caused a rapid decrease in the culturability of intracellular bacteria, concomitant with stable or increased absolute bacterial DNA levels. Both antibiotics significantly inhibited autophagic flux. However, modulation of autophagic flux did not affect viable bacterial DNA levels. In summary, autophagy was shown to be a factor in the host-pathogen relationship in this model, as its modulation affected the growth state of intracellular S. aureus with respect to both their culturability and propensity to escape the intracellular niche. While rifampicin and vancomycin treatments moderately suppressed autophagic flux acutely, this did not explain the paradoxical response of antibiotic treatment in decreasing S. aureus culturability whilst failing to clear bacterial DNA and hence intracellular bacterial load. Thus, off-target effects of rifampicin and vancomycin on autophagic flux in osteocyte-like cells could not explain the persistent S. aureus infection in these cells.
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Affiliation(s)
- Nicholas J. Gunn
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Stephen P. Kidd
- Australian Centre for Antimicrobial Resistance Ecology, University of Adelaide, Adelaide, SA, Australia
- Research Centre for Infectious Disease, School of Biological Science, University of Adelaide, Adelaide, SA, Australia
| | - Lucian B. Solomon
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
- Department of Orthopaedics and Trauma, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - Dongqing Yang
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
| | - Eugene Roscioli
- Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide, SA, Australia
- Department of Medicine, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
- Centre for Cancer Biology, South Australia (SA) Pathology and University of South Australia, Adelaide, SA, Australia
| | - Gerald J. Atkins
- Biomedical Orthopaedic Research Group, Centre for Orthopaedic and Trauma Research, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
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Chen H, Xu J, Wang P, Shu Q, Huang L, Guo J, Zhang X, Zhang H, Wang Y, Shen Z, Chen X, Zhang Q. Protein phosphatase 2 regulatory subunit B''Alpha silencing inhibits tumor cell proliferation in liver cancer. Cancer Med 2019; 8:7741-7753. [PMID: 31647192 PMCID: PMC6912040 DOI: 10.1002/cam4.2620] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Revised: 09/29/2019] [Accepted: 10/06/2019] [Indexed: 12/24/2022] Open
Abstract
Aim To explore the effects of protein phosphatase 2 regulatory subunit B''Alpha (PPP2R3A) on the proliferation and migration of liver cancer cells. Methods Expression of PPP2R3A in tumor tissues of hepatocellular carcinoma (HCC) patients was detected by immunohistochemistry and western blotting. In two liver cancer cell lines (HepG2 and HuH7), PPP2R3A expression was silenced and then overexpression with PPP2R3A lentiviral vectors, and the effects of PPP2R3A knockdown or overexpression on the proliferation, cell cycle, migration, and invasion of HCC cells were determined in vitro. In a xenograft cancer model in nude mice, the in vivo effects of PPP2R3A knockdown on tumor growth and cancer cell proliferation were evaluated. Results PPP2R3A expression was found in tumor foci in six of eight HCC samples, at a level higher than that in the adjacent para‐tumor tissues. PPP2R3A expression was observed primarily in the cytoplasm of the cancer cells. Knockdown of PPP2R3A resulted in significant inhibition of hepatoma cell proliferation (P < .05), migration (P < .01), and invasion (P < .01) as well as a significant delay in the G1/S transition in both liver cancer lines (P < .05) and increased p53 expression. Conversely, overexpression of PPP2R3A promoted the proliferation (P < .05) and altered cell cycle progression (P < .05) of both liver cancer cell lines. In vivo, PPP2R3A knockdown in liver cancer cells led to significant reductions in the tumor volume (P < .001) and the expression of Ki‐67 in tumor tissues (P < .05). Conclusion PPP2R3A may play a role in liver cancer via the regulation of tumor cell proliferation and invasion.
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Affiliation(s)
- Huijuan Chen
- Department of Liver Transplantation, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China.,Graduate School, Anhui Medical University, Hefei, China
| | - Jing Xu
- National Translational Science Center for Molecular Medicine & Department of Cell Biology, State Key Laboratory of Cancer Biology, Fourth Military Medical University, Xi'an, China
| | - Peixiao Wang
- Department of Gastroenterology, Henan Children's Hospital, Zhengzhou, China
| | - Qingming Shu
- Pathology Department, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
| | - Lihong Huang
- Medical Department, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
| | - Jing Guo
- Medical Department, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
| | - Xuyi Zhang
- Medical Department, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
| | - Hongying Zhang
- Medical Department, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
| | - Ying Wang
- Department of Liver Transplantation, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
| | - Zhongyang Shen
- Department of Liver Transplantation, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China.,Department of Transplantation Surgery, Tianjin First Central Hospital, Tianjin, China
| | - Xinguo Chen
- Department of Liver Transplantation, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
| | - Qing Zhang
- Department of Liver Transplantation, The Third Medical Centre, Chinese PLA (People's Liberation Army) General Hospital, Beijing, China
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Shin JH, Park CW, Yoon G, Hong SM, Choi KY. NNMT depletion contributes to liver cancer cell survival by enhancing autophagy under nutrient starvation. Oncogenesis 2018; 7:58. [PMID: 30093610 PMCID: PMC6085294 DOI: 10.1038/s41389-018-0064-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/27/2018] [Accepted: 06/21/2018] [Indexed: 12/19/2022] Open
Abstract
Nicotinamide N-methyl transferase (NNMT) transfers a methyl group from S-adenosyl-L-methionine (SAM) to nicotinamide (NAM), producing 1-methylnicotinamide (1MNA). NNMT has been implicated in several cancer types and recently in metabolism, but its role in autophagy regulation has not yet been investigated. In this study, we determined that NNMT negatively regulated autophagy at the stage of ULK1 activation through protein phosphatase 2A (PP2A) activity. Specifically, NNMT knockdown increased PP2A methylation and subsequently enhanced phosphatase activity. Consequent p-ULK1 (S638) dephosphorylation derepressed ULK1 activity, resulting in autophagy induction. Accordingly, NNMT downregulation rescued tumor cells under nutrient deficiency in vivo, which was alleviated by ULK1 inhibitor treatment. In summary, our results suggest a novel mechanism by which tumor cells protect themselves against nutrient deprivation through NNMT suppression to accelerate autophagy.
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Affiliation(s)
- Ji Hye Shin
- Department of Life Sciences, Pohang University of Science and Technology, 77 Cheongam-ro, Nam-gu, Pohang, Gyeongbuk, 37673, Korea
| | - Chang Wook Park
- Biokogen Inc. Korea National Food Cluster #255, 110 Dongchonje-gil, Wanggung-myeon, Iksan, Jeonbuk, 54576, Korea
| | - Gyesoon Yoon
- Department of Biochemistry, Ajou University School of Medicine, 164 World cup-ro, Yeongtong-gu, Suwon, Gyeonggi, 16499, Korea
- Department of Biomedical Science, Graduate School, Ajou University, 164 World cup-ro, Yeongtong-gu, Suwon, Gyeonggi, 16499, Korea
| | - Sun Mi Hong
- Department of Biochemistry, Ajou University School of Medicine, 164 World cup-ro, Yeongtong-gu, Suwon, Gyeonggi, 16499, Korea.
| | - Kwan Yong Choi
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, 77 Cheongam-ro, Nam-gu, Pohang, Gyeongbuk, 37673, Korea.
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Pengo N, Agrotis A, Prak K, Jones J, Ketteler R. A reversible phospho-switch mediated by ULK1 regulates the activity of autophagy protease ATG4B. Nat Commun 2017; 8:294. [PMID: 28821708 PMCID: PMC5562857 DOI: 10.1038/s41467-017-00303-2] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 06/20/2017] [Indexed: 12/26/2022] Open
Abstract
Upon induction of autophagy, the ubiquitin-like protein LC3 is conjugated to phosphatidylethanolamine (PE) on the inner and outer membrane of autophagosomes to allow cargo selection and autophagosome formation. LC3 undergoes two processing steps, the proteolytic cleavage of pro-LC3 and the de-lipidation of LC3-PE from autophagosomes, both executed by the same cysteine protease ATG4. How ATG4 activity is regulated to co-ordinate these events is currently unknown. Here we find that ULK1, a protein kinase activated at the autophagosome formation site, phosphorylates human ATG4B on serine 316. Phosphorylation at this residue results in inhibition of its catalytic activity in vitro and in vivo. On the other hand, phosphatase PP2A-PP2R3B can remove this inhibitory phosphorylation. We propose that the opposing activities of ULK1-mediated phosphorylation and PP2A-mediated dephosphorylation provide a phospho-switch that regulates the cellular activity of ATG4B to control LC3 processing.Upon autophagy induction, LC3 is cleaved by the protease ATG4 and conjugated to the autophagosomal membrane; however, its removal is mediated by the same protease. Here the authors show that ULK1-mediated phosphorylation and PP2A-mediated dephosphorylation of ATG4 regulates its cellular activity to control LC3 processing.
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Affiliation(s)
- N Pengo
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - A Agrotis
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - K Prak
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - J Jones
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - R Ketteler
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK.
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5
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López-García I, Gerő D, Szczesny B, Szoleczky P, Olah G, Módis K, Zhang K, Gao J, Wu P, Sowers LC, DeWitt D, Prough DS, Szabo C. Development of a stretch-induced neurotrauma model for medium-throughput screening in vitro: identification of rifampicin as a neuroprotectant. Br J Pharmacol 2016; 175:284-300. [PMID: 27723079 DOI: 10.1111/bph.13642] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 09/19/2016] [Accepted: 09/26/2016] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND AND PURPOSE We hypothesized that an in vitro, stretch-based model of neural injury may be useful to identify compounds that decrease the cellular damage in neurotrauma. EXPERIMENTAL APPROACH We screened three neural cell lines (B35, RN33B and SH-SY5Y) subjected to two differentiation methods and selected all-trans-retinoic acid-differentiated B35 rat neuroblastoma cells subjected to rapid stretch injury, coupled with a subthreshold concentration of H2 O2 , for the screen. The model induced marked alterations in gene expression and proteomic signature of the cells and culminated in delayed cell death (LDH release) and mitochondrial dysfunction [reduced 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) conversion]. Follow-up studies utilized human stem cell-derived neurons subjected to rapid stretch injury. KEY RESULTS From screening of a composite library of 3500 drugs, five drugs (when applied in a post-treatment regimen relative to stretch injury) improved both LDH and MTT responses. The effects of rifampicin were investigated in further detail. Rifampicin reduced cell necrosis and apoptosis and improved cellular bioenergetics. In a second model (stretch injury in human stem cell-derived neurons), rifampicin pretreatment attenuated LDH release, protected against the loss of neurite length and maintained neuron-specific class III β-tubulin immunoreactivity. CONCLUSIONS AND IMPLICATIONS We conclude that the current model is suitable for medium-throughput screening to identify compounds with neuroprotective potential. Rifampicin, when applied either in pre- or post-treatment, improves the viability of neurons subjected to stretch injury and protects against neurite loss. Rifampicin may be a candidate for repurposing for the therapy of traumatic brain injury. LINKED ARTICLES This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.
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Affiliation(s)
- Isabel López-García
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Domokos Gerő
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Bartosz Szczesny
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Petra Szoleczky
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Gabor Olah
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Katalin Módis
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Kangling Zhang
- Department of Pharmacology, University of Texas Medical Branch, Galveston, TX, USA
| | - Jungling Gao
- Department of Neuroscience & Cell Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Ping Wu
- Department of Neuroscience & Cell Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Lawrence C Sowers
- Department of Pharmacology, University of Texas Medical Branch, Galveston, TX, USA
| | - Doug DeWitt
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Donald S Prough
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
| | - Csaba Szabo
- Department of Anesthesiology, University of Texas Medical Branch, Galveston, TX, USA
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Gupta A, Misra A, Deretic V. Targeted pulmonary delivery of inducers of host macrophage autophagy as a potential host-directed chemotherapy of tuberculosis. Adv Drug Deliv Rev 2016; 102:10-20. [PMID: 26829287 DOI: 10.1016/j.addr.2016.01.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 11/26/2015] [Accepted: 01/21/2016] [Indexed: 12/19/2022]
Abstract
One of the promising host-directed chemotherapeutic interventions in tuberculosis (TB) is based on inducing autophagy as an immune effector. Here we consider the strengths and weaknesses of potential autophagy-based pharmacological intervention. Using the existing drugs that induce autophagy is an option, but it has limitations given the broad role of autophagy in most cells, tissues, and organs. Thus, it may be desirable that the agent being used to modulate autophagy is applied in a targeted manner, e.g. delivered to affected tissues, with infected macrophages being an obvious choice. This review addresses the advantages and disadvantages of delivering drugs to induce autophagy in M. tuberculosis-infected macrophages. One option, already being tested in models, is to design particles for inhalation delivery to lung macrophages. The choice of drugs, drug release kinetics and intracellular residence times, non-target cell exposure and feasibility of use by patients is discussed. We term here this (still experimental) approach, of compartment-targeting, autophagy-based, host-directed therapy as "Track-II antituberculosis chemotherapy."
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Wang H, Liu J, Lin S, Wang B, Xing M, Guo Z, Xu L. MCLR-induced PP2A inhibition and subsequent Rac1 inactivation and hyperphosphorylation of cytoskeleton-associated proteins are involved in cytoskeleton rearrangement in SMMC-7721 human liver cancer cell line. CHEMOSPHERE 2014; 112:141-153. [PMID: 25048900 DOI: 10.1016/j.chemosphere.2014.03.130] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 03/26/2014] [Accepted: 03/27/2014] [Indexed: 06/03/2023]
Abstract
Cyanobacteria-derived toxin microcystin-LR (MCLR) has been widely investigated in its effects on normal cells, there is little information concerning its effects on cancer cells. In the present study, the SMMC-7721 human liver cancer cell line treated with MCLR was used to investigate the change of PP2A, cytoskeleton rearrangement, phosphorylation levels of PP2A substrates that related with cytoskeleton stability and explored underlying mechanisms. Here, we confirmed that MCLR entered into SMMC-7721 cells, bound to PP2A/C subunit and inhibited the activity of PP2A. The upregulation of phosphorylation of the PP2A/C subunit and PP2A regulation protein α4, as well as the change in the association of PP2A/C with α4, were responsible for the decrease in PP2A activity. Another novel finding is that the rearrangement of filamentous actin and microtubules led by MCLR may attribute to the increased phosphorylation of HSP27, VASP and cofilin due to PP2A inhibition. As a result of weakened interactions with PP2A and alterations in its subcellular localization, Rac1 may contribute to the cytoskeletal rearrangement induced by MCLR in SMMC-7721 cells. The current paper presents the first report demonstrating the characteristic of PP2A in MCLR exposed cancer cells, which were more susceptible to MCLR compared with the normal cell lines we previously found, which may be owing to the absence of some type of compensatory mechanisms. The hyperphosphorylation of cytoskeleton-associated proteins and Rac1 inactivation which were induced by inhibition of PP2A are shown to be involved in cytoskeleton rearrangement.
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Affiliation(s)
- Hao Wang
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China
| | - Jinghui Liu
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China
| | - Shuyan Lin
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China
| | - Beilei Wang
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China
| | - Mingluan Xing
- Zhejiang Center for Disease Control and Prevention, Hangzhou 310051, China
| | - Zonglou Guo
- Department of Biosystem Engineering, College of Biosystem Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
| | - Lihong Xu
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou 310058, China.
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Holla S, Kurowska-Stolarska M, Bayry J, Balaji KN. Selective inhibition of IFNG-induced autophagy by Mir155- and Mir31-responsive WNT5A and SHH signaling. Autophagy 2013; 10:311-30. [PMID: 24343269 DOI: 10.4161/auto.27225] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Autophagy is one of the major immune mechanisms engaged to clear intracellular infectious agents. However, several pathogens have evolved strategies to evade autophagy. Here, we demonstrated that Mycobacteria, Shigella, and Listeria but not Klebsiella, Staphylococcus, and Escherichia inhibit IFNG-induced autophagy in macrophages by evoking selective and robust activation of WNT and SHH pathways via MTOR. Utilization of gain- or loss-of-function analyses as well as mir155-null macrophages emphasized the role of MTOR-responsive epigenetic modifications in the induction of Mir155 and Mir31. Importantly, cellular levels of PP2A, a phosphatase, were regulated by Mir155 and Mir31 to fine-tune autophagy. Diminished expression of PP2A led to inhibition of GSK3B, thus facilitating the prolonged activation of WNT and SHH signaling pathways. Sustained WNT and SHH signaling effectuated the expression of anti-inflammatory lipoxygenases, which in tandem inhibited IFNG-induced JAK-STAT signaling and contributed to evasion of autophagy. Altogether, these results established a role for new host factors and inhibitory mechanisms employed by the pathogens to limit autophagy, which could be targeted for therapeutic interventions.
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Affiliation(s)
- Sahana Holla
- Department of Microbiology and Cell Biology; Indian Institute of Science; Bangalore, Karnataka India
| | | | - Jagadeesh Bayry
- Centre de Recherche des Cordeliers; Institut National de la Santé et de la Recherche Médicale; Paris, France
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Magnaudeix A, Wilson CM, Page G, Bauvy C, Codogno P, Lévêque P, Labrousse F, Corre-Delage M, Yardin C, Terro F. PP2A blockade inhibits autophagy and causes intraneuronal accumulation of ubiquitinated proteins. Neurobiol Aging 2012; 34:770-90. [PMID: 22892312 DOI: 10.1016/j.neurobiolaging.2012.06.026] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 05/30/2012] [Accepted: 06/29/2012] [Indexed: 12/11/2022]
Abstract
Using cultured cortical neurons, we show that the blockade of protein phosphatase 2A (PP2A), either pharmacologically by okadaic acid or by short hairpin RNA (shRNA)-mediated silencing of PP2A catalytic subunit, inhibited basal autophagy and autophagy induced in several experimental settings (including serum deprivation, endoplasmic reticulum stress, rapamycin, and proteasome inhibition) at early stages before autophagosome maturation. Conversely, PP2A upregulation by PP2A catalytic subunit overexpression stimulates neuronal autophagy. In addition, PP2A blockade resulted in the activation of the negative regulator of autophagy mammalian target of rapamycin complex 1 and 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK) and led to intraneuronal accumulation of p62- and ubiquitin-positive protein inclusions, likely due to autophagy downregulation. These data are consistent with previous findings showing that specific invalidation of the autophagy process in the nervous system of mouse resulted in the accumulation of p62- and ubiquitin-positive protein inclusion bodies. Furthermore, we showed that PP2A inhibition alters the distribution of the microtubule-associated protein 1 light chain(LC) 3-I (MAP LC3-I), a key component of the autophagy molecular machinery. Whether MAP LC3-I distribution in the cell accounts for autophagy regulation remains to be determined. These data are important to human neurodegenerative diseases, especially Alzheimer's disease, because they provide links for the first time between the pathological features of Alzheimer's disease:PP2A downregulation, autophagy disruption, and protein aggregation.
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Affiliation(s)
- Amandine Magnaudeix
- Laboratoire d'Histologie, de Biologie Cellulaire et de Cytogénétique, Faculté de Médecine, Université de Limoges, Limoges, France
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10
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Homer CR, Kabi A, Marina-García N, Sreekumar A, Nesvizhskii AI, Nickerson KP, Chinnaiyan AM, Nuñez G, McDonald C. A dual role for receptor-interacting protein kinase 2 (RIP2) kinase activity in nucleotide-binding oligomerization domain 2 (NOD2)-dependent autophagy. J Biol Chem 2012; 287:25565-76. [PMID: 22665475 DOI: 10.1074/jbc.m111.326835] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Autophagy is triggered by the intracellular bacterial sensor NOD2 (nucleotide-binding, oligomerization domain 2) as an anti-bacterial response. Defects in autophagy have been implicated in Crohn's disease susceptibility. The molecular mechanisms of activation and regulation of this process by NOD2 are not well understood, with recent studies reporting conflicting requirements for RIP2 (receptor-interacting protein kinase 2) in autophagy induction. We examined the requirement of NOD2 signaling mediated by RIP2 for anti-bacterial autophagy induction and clearance of Salmonella typhimurium in the intestinal epithelial cell line HCT116. Our data demonstrate that NOD2 stimulates autophagy in a process dependent on RIP2 tyrosine kinase activity. Autophagy induction requires the activity of the mitogen-activated protein kinases MEKK4 and p38 but is independent of NFκB signaling. Activation of autophagy was inhibited by a PP2A phosphatase complex, which interacts with both NOD2 and RIP2. PP2A phosphatase activity inhibited NOD2-dependent autophagy but not activation of NFκB or p38. Upon stimulation of NOD2, the phosphatase activity of the PP2A complex is inhibited through tyrosine phosphorylation of the catalytic subunit in a process dependent on RIP2 activity. These findings demonstrate that RIP2 tyrosine kinase activity is not only required for NOD2-dependent autophagy but plays a dual role in this process. RIP2 both sends a positive autophagy signal through activation of p38 MAPK and relieves repression of autophagy mediated by the phosphatase PP2A.
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Affiliation(s)
- Craig R Homer
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195, USA
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11
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Bánréti Á, Lukácsovich T, Csikós G, Erdélyi M, Sass M. PP2A regulates autophagy in two alternative ways in Drosophila. Autophagy 2012; 8:623-36. [PMID: 22330894 DOI: 10.4161/auto.19081] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Protein phosphatase 2A (PP2A) holoenzyme is a heterotrimeric complex, consisting of A, B and C subunits. The catalytic subunit PP2A-C (microtubule star/mts) binds to the C-terminal part of the scaffold protein PP2A-A (PP2A-29B). In Drosophila, there are three different forms of B subunits (widerborst/wdb, twins/tws and PP2A-B'), which determine the subcellular localization and substrate specificity of the holoenzyme. Previous studies demonstrated that PP2A is involved in the control of TOR-dependent autophagy both in yeast and mammals. Furthermore, in Drosophila, wdb genetically interacts with the PtdIns3K/PTEN/Akt signaling cascade, which is a main upstream regulatory system of dTOR. Here we demonstrate that in Drosophila, two different PP2A complexes (containing B' or wdb subunit) play essential roles in the regulation of starvation-induced autophagy. The PP2A-A/wdb/C complex acts upstream of dTOR, whereas the PP2A-A/B'/C complex functions as a target of dTOR and may regulate the elongation of autophagosomes and their subsequent fusion with lysosomes. We also identified three Drosophila Atg orthologs (Atg14, Atg17 and Atg101), which represent potential targets of the PP2A-A/B'/C complex during autophagy.
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Affiliation(s)
- Ágnes Bánréti
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
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12
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Corcelle EA, Puustinen P, Jäättelä M. Apoptosis and autophagy: Targeting autophagy signalling in cancer cells -'trick or treats'? FEBS J 2009; 276:6084-96. [PMID: 19788415 DOI: 10.1111/j.1742-4658.2009.07332.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Macroautophagy (hereafter referred to as autophagy) is a tightly regulated lysosome-dependent catabolic pathway. During this process, cytosolic constituents are sequestered into autophagosomes, which subsequently fuse with lysosomes to become autolysosomes, where their contents are degraded. Autophagy contributes to the maintenance of the cellular energy homeostasis, to the clearance of damaged organelles and to adaptation to environmental stresses. Accordingly, autophagy defects have been linked to a wide range of human pathologies, including cancer. The recent discovery of several evolutionarily conserved genes involved in autophagosome formation has greatly stimulated the autophagy research, and the complex signalling networks regulating mammalian autophagy have begun to emerge. Here, we draw the current picture of signalling pathways connecting mitogenic and stress-induced signals to the initiation and maturation of autophagosomes and discuss the possibilities of their targeting as therapeutic adjuvants in anticancer therapy.
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Affiliation(s)
- Elisabeth A Corcelle
- Apoptosis Department and Centre for Genotoxic Stress Research, Institute of Cancer Biology, Danish Cancer Society, Copenhagen, Denmark
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