1401
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Trehalose, an mTOR-Independent Inducer of Autophagy, Inhibits Human Cytomegalovirus Infection in Multiple Cell Types. J Virol 2015; 90:1259-77. [PMID: 26559848 DOI: 10.1128/jvi.02651-15] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 11/06/2015] [Indexed: 02/08/2023] Open
Abstract
UNLABELLED Human cytomegalovirus (HCMV) is the major viral cause of birth defects and a serious problem in immunocompromised individuals and has been associated with atherosclerosis. Previous studies have shown that the induction of autophagy can inhibit the replication of several different types of DNA and RNA viruses. The goal of the work presented here was to determine whether constitutive activation of autophagy would also block replication of HCMV. Most prior studies have used agents that induce autophagy via inhibition of the mTOR pathway. However, since HCMV infection alters the sensitivity of mTOR kinase-containing complexes to inhibitors, we sought an alternative method of inducing autophagy. We chose to use trehalose, a nontoxic naturally occurring disaccharide that is found in plants, insects, microorganisms, and invertebrates but not in mammals and that induces autophagy by an mTOR-independent mechanism. Given the many different cell targets of HCMV, we proceeded to determine whether trehalose would inhibit HCMV infection in human fibroblasts, aortic artery endothelial cells, and neural cells derived from human embryonic stem cells. We found that in all of these cell types, trehalose induces autophagy and inhibits HCMV gene expression and production of cell-free virus. Treatment of HCMV-infected neural cells with trehalose also inhibited production of cell-associated virus and partially blocked the reduction in neurite growth and cytomegaly. These results suggest that activation of autophagy by the natural sugar trehalose or other safe mTOR-independent agents might provide a novel therapeutic approach for treating HCMV disease. IMPORTANCE HCMV infects multiple cell types in vivo, establishes lifelong persistence in the host, and can cause serious health problems for fetuses and immunocompromised individuals. HCMV, like all other persistent pathogens, has to finely tune its interplay with the host cellular machinery to replicate efficiently and evade detection by the immune system. In this study, we investigated whether modulation of autophagy, a host pathway necessary for the recycling of nutrients and removal of protein aggregates, misfolded proteins, and pathogens, could be used to target HCMV. We found that autophagy could be significantly increased by treatment with the nontoxic, natural disaccharide trehalose. Importantly, trehalose had a profound inhibitory effect on viral gene expression and strongly impaired viral spread. These data constitute a proof-of-concept for the use of natural products targeting host pathways rather than the virus itself, thus reducing the risk of the development of resistance to treatment.
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1402
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Fang X, Zhou J, Liu W, Duan X, Gala U, Sandoval H, Jaiswal M, Tong C. Dynamin Regulates Autophagy by Modulating Lysosomal Function. J Genet Genomics 2015; 43:77-86. [PMID: 26924690 DOI: 10.1016/j.jgg.2015.10.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 10/23/2015] [Accepted: 10/28/2015] [Indexed: 11/27/2022]
Abstract
Autophagy is a central lysosomal degradation pathway required for maintaining cellular homeostasis and its dysfunction is associated with numerous human diseases. To identify players in autophagy, we tested ∼1200 chemically induced mutations on the X chromosome in Drosophila fat body clones and discovered that shibire (shi) plays an essential role in starvation-induced autophagy. shi encodes a dynamin protein required for fission of clathrin-coated vesicles from the plasma membrane during endocytosis. We showed that Shi is dispensable for autophagy initiation and autophagosome-lysosome fusion, but required for lysosomal/autolysosomal acidification. We also showed that other endocytic core machinery components like clathrin and AP2 play similar but not identical roles in regulating autophagy and lysosomal function as dynamin. Previous studies suggested that dynamin directly regulates autophagosome formation and autophagic lysosome reformation (ALR) through its excision activity. Here, we provide evidence that dynamin also regulates autophagy indirectly by regulating lysosomal function.
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Affiliation(s)
- Xuefei Fang
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Jia Zhou
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Wei Liu
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Xiuying Duan
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China
| | - Upasana Gala
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Hector Sandoval
- Howard Hughes Medical Institute, Houston, TX 77030, USA; Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Manish Jaiswal
- Howard Hughes Medical Institute, Houston, TX 77030, USA; Department of Human and Molecular Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Chao Tong
- Life Sciences Institute and Innovation Center for Cell Signaling Network, Zhejiang University, Hangzhou 310058, China.
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1403
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The Role of Organelle Stresses in Diabetes Mellitus and Obesity: Implication for Treatment. Anal Cell Pathol (Amst) 2015; 2015:972891. [PMID: 26613076 PMCID: PMC4646985 DOI: 10.1155/2015/972891] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 10/08/2015] [Indexed: 12/17/2022] Open
Abstract
The type 2 diabetes pandemic in recent decades is a huge global health threat. This pandemic is primarily attributed to the surplus of nutrients and the increased prevalence of obesity worldwide. In contrast, calorie restriction and weight reduction can drastically prevent type 2 diabetes, indicating a central role of nutrient excess in the development of diabetes. Recently, the molecular links between excessive nutrients, organelle stress, and development of metabolic disease have been extensively studied. Specifically, excessive nutrients trigger endoplasmic reticulum stress and increase the production of mitochondrial reactive oxygen species, leading to activation of stress signaling pathway, inflammatory response, lipogenesis, and pancreatic beta-cell death. Autophagy is required for clearance of hepatic lipid clearance, alleviation of pancreatic beta-cell stress, and white adipocyte differentiation. ROS scavengers, chemical chaperones, and autophagy activators have demonstrated promising effects for the treatment of insulin resistance and diabetes in preclinical models. Further results from clinical trials are eagerly awaited.
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1404
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Chandra V, Bhagyaraj E, Nanduri R, Ahuja N, Gupta P. NR1D1 ameliorates Mycobacterium tuberculosis clearance through regulation of autophagy. Autophagy 2015; 11:1987-1997. [PMID: 26390081 PMCID: PMC4824569 DOI: 10.1080/15548627.2015.1091140] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 08/19/2015] [Accepted: 09/01/2015] [Indexed: 01/07/2023] Open
Abstract
NR1D1 (nuclear receptor subfamily 1, group D, member 1), an adopted orphan nuclear receptor, is widely known to orchestrate the expression of genes involved in various biological processes such as adipogenesis, skeletal muscle differentiation, and lipid and glucose metabolism. Emerging evidence suggests that various members of the nuclear receptor superfamily perform a decisive role in the modulation of autophagy. Recently, NR1D1 has been implicated in augmenting the antimycobacterial properties of macrophages and providing protection against Mycobacterium tuberculosis infection by downregulating the expression of the IL10 gene in human macrophages. This antiinfective property of NR1D1 suggests the need for an improved understanding of its role in other host-associated antimycobacterial pathways. The results presented here demonstrate that in human macrophages either ectopic expression of NR1D1 or treatment with its agonist, GSK4112, enhanced the number of acidic vacuoles as well as the level of MAP1LC3-II, a signature molecule for determination of autophagy progression, in a concentration- and time-dependent manner. Conversely, a decrease in NR1D1 in knockdown cells resulted in the reduced expression of lysosomal-associated membrane protein 1, LAMP1, commensurate with a decrease in the level of transcription factor EB, TFEB. This is indicative of that NR1D1 may have a regulatory role in lysosome biogenesis. NR1D1 being a repressor, its positive regulation on LAMP1 and TFEB is suggestive of an indirect byzantine mechanism of action. Its role in the modulation of autophagy and lysosome biogenesis together with its ability to repress IL10 gene expression supports the theory that NR1D1 has a pivotal antimycobacterial function in human macrophages.
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Affiliation(s)
- Vemika Chandra
- CSIR- Institute of Microbial Technology; Chandigarh, India
| | - Ella Bhagyaraj
- CSIR- Institute of Microbial Technology; Chandigarh, India
| | | | - Nancy Ahuja
- CSIR- Institute of Microbial Technology; Chandigarh, India
| | - Pawan Gupta
- CSIR- Institute of Microbial Technology; Chandigarh, India
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1405
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Grootaert MOJ, da Costa Martins PA, Bitsch N, Pintelon I, De Meyer GRY, Martinet W, Schrijvers DM. Defective autophagy in vascular smooth muscle cells accelerates senescence and promotes neointima formation and atherogenesis. Autophagy 2015; 11:2014-2032. [PMID: 26391655 PMCID: PMC4824610 DOI: 10.1080/15548627.2015.1096485] [Citation(s) in RCA: 210] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 09/03/2015] [Accepted: 09/15/2015] [Indexed: 12/13/2022] Open
Abstract
Autophagy is triggered in vascular smooth muscle cells (VSMCs) of diseased arterial vessels. However, the role of VSMC autophagy in cardiovascular disease is poorly understood. Therefore, we investigated the effect of defective autophagy on VSMC survival and phenotype and its significance in the development of postinjury neointima formation and atherosclerosis. Tissue-specific deletion of the essential autophagy gene Atg7 in murine VSMCs (atg7-/- VSMCs) caused accumulation of SQSTM1/p62 and accelerated the development of stress-induced premature senescence as shown by cellular and nuclear hypertrophy, CDKN2A-RB-mediated G1 proliferative arrest and senescence-associated GLB1 activity. Transfection of SQSTM1-encoding plasmid DNA in Atg7+/+ VSMCs induced similar features, suggesting that accumulation of SQSTM1 promotes VSMC senescence. Interestingly, atg7-/- VSMCs were resistant to oxidative stress-induced cell death as compared to controls. This effect was attributed to nuclear translocation of the transcription factor NFE2L2 resulting in upregulation of several antioxidative enzymes. In vivo, defective VSMC autophagy led to upregulation of MMP9, TGFB and CXCL12 and promoted postinjury neointima formation and diet-induced atherogenesis. Lesions of VSMC-specific atg7 knockout mice were characterized by increased total collagen deposition, nuclear hypertrophy, CDKN2A upregulation, RB hypophosphorylation, and GLB1 activity, all features typical of cellular senescence. To conclude, autophagy is crucial for VSMC function, phenotype, and survival. Defective autophagy in VSMCs accelerates senescence and promotes ligation-induced neointima formation and diet-induced atherogenesis, implying that autophagy inhibition as therapeutic strategy in the treatment of neointimal stenosis and atherosclerosis would be unfavorable. Conversely, stimulation of autophagy could be a valuable new strategy in the treatment of arterial disease.
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Affiliation(s)
- Mandy OJ Grootaert
- Laboratory of Physiopharmacology; University of Antwerp; Antwerp, Belgium
| | - Paula A da Costa Martins
- Department of Cardiology; Cardiovascular Research Institute Maastricht; Maastricht, The Netherlands
| | - Nicole Bitsch
- Department of Cardiology; Cardiovascular Research Institute Maastricht; Maastricht, The Netherlands
| | - Isabel Pintelon
- Laboratory of Cell Biology and Histology; University of Antwerp; Antwerp, Belgium
| | - Guido RY De Meyer
- Laboratory of Physiopharmacology; University of Antwerp; Antwerp, Belgium
| | - Wim Martinet
- Laboratory of Physiopharmacology; University of Antwerp; Antwerp, Belgium
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1406
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Zhang M, Kenny SJ, Ge L, Xu K, Schekman R. Translocation of interleukin-1β into a vesicle intermediate in autophagy-mediated secretion. eLife 2015; 4:e11205. [PMID: 26523392 PMCID: PMC4728131 DOI: 10.7554/elife.11205] [Citation(s) in RCA: 262] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 10/30/2015] [Indexed: 12/23/2022] Open
Abstract
Recent evidence suggests that autophagy facilitates the unconventional secretion of the pro-inflammatory cytokine interleukin 1β (IL-1β). Here, we reconstituted an autophagy-regulated secretion of mature IL-1β (m-IL-1β) in non-macrophage cells. We found that cytoplasmic IL-1β associates with the autophagosome and m-IL-1β enters into the lumen of a vesicle intermediate but not into the cytoplasmic interior formed by engulfment of the autophagic membrane. In advance of secretion, m-IL-1β appears to be translocated across a membrane in an event that may require m-IL-1β to be unfolded or remain conformationally flexible and is dependent on two KFERQ-like motifs essential for the association of IL-1β with HSP90. A vesicle, possibly a precursor of the phagophore, contains translocated m-IL-1β and later turns into an autophagosome in which m-IL-1β resides within the intermembrane space of the double-membrane structure. Completion of IL-1β secretion requires Golgi reassembly and stacking proteins (GRASPs) and multi-vesicular body (MVB) formation.
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Affiliation(s)
- Min Zhang
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - Samuel J Kenny
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Liang Ge
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Randy Schekman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
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1407
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Lin Y, Ding Y, Wang J, Shen J, Kung CH, Zhuang X, Cui Y, Yin Z, Xia Y, Lin H, Robinson DG, Jiang L. Exocyst-Positive Organelles and Autophagosomes Are Distinct Organelles in Plants. PLANT PHYSIOLOGY 2015; 169:1917-32. [PMID: 26358417 PMCID: PMC4634068 DOI: 10.1104/pp.15.00953] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 09/09/2015] [Indexed: 05/23/2023]
Abstract
Autophagosomes are organelles that deliver cytosolic proteins for degradation in the vacuole of the cell. In contrast, exocyst-positive organelles (EXPO) deliver cytosolic proteins to the cell surface and therefore represent a form of unconventional protein secretion. Because both structures have two boundary membranes, it has been suggested that they may have been falsely treated as separate entities. Using suspension culture cells and root tissue cells of transgenic Arabidopsis (Arabidopsis thaliana) plants expressing either the EXPO marker Arabidopsis Exo70E2-GFP or the autophagosome marker yellow fluorescent protein (YFP)-autophagy-related gene 8e/f (ATG8e/f), and using specific antibodies against Exo70E2 and ATG8, we have now established that, in normally growing cells, EXPO and autophagosomes are distinct from one another. However, when cells/roots are subjected to autophagy induction, EXPO as well as autophagosomes fuse with the vacuole. In the presence of concanamycin A, the punctate fluorescent signals from both organelles inside the vacuole remain visible for hours and overlap to a significant degree. Tonoplast staining with FM4-64/YFP-Rab7-like GTPase/YFP-vesicle-associated membrane protein711 confirmed the internalization of tonoplast membrane concomitant with the sequestration of EXPO and autophagosomes. This suggests that EXPO and autophagosomes may be related to one another; however, whereas induction of autophagy led to an increase in the amount of ATG8 recruited to membranes, Exo70E2 did not respond in a similar manner.
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Affiliation(s)
- Youshun Lin
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Yu Ding
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Juan Wang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Jinbo Shen
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Chun Hong Kung
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Xiaohong Zhuang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Yong Cui
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Zhao Yin
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Yiji Xia
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Hongxuan Lin
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - David G Robinson
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
| | - Liwen Jiang
- Centre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.L., Y.D., J.W., J.S., C.H.K., X.Z., Y.C., L.J.);CUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China (L.J.);Department of Biology, Hong Kong Baptist University, Hong Kong, China (Z.Y., Y.X.);Partner State Key Laboratory of Agrobiotechnology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China (Y.X.);National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China (H.L.); andCentre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany (D.G.R.)
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1408
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Autophagy-Related Protein ATG8 Has a Noncanonical Function for Apicoplast Inheritance in Toxoplasma gondii. mBio 2015; 6:e01446-15. [PMID: 26507233 PMCID: PMC4626856 DOI: 10.1128/mbio.01446-15] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Autophagy is a catabolic process widely conserved among eukaryotes that permits the rapid degradation of unwanted proteins and organelles through the lysosomal pathway. This mechanism involves the formation of a double-membrane structure called the autophagosome that sequesters cellular components to be degraded. To orchestrate this process, yeasts and animals rely on a conserved set of autophagy-related proteins (ATGs). Key among these factors is ATG8, a cytoplasmic protein that is recruited to nascent autophagosomal membranes upon the induction of autophagy. Toxoplasma gondii is a potentially harmful human pathogen in which only a subset of ATGs appears to be present. Although this eukaryotic parasite seems able to generate autophagosomes upon stresses such as nutrient starvation, the full functionality and biological relevance of a canonical autophagy pathway are as yet unclear. Intriguingly, in T. gondii, ATG8 localizes to the apicoplast under normal intracellular growth conditions. The apicoplast is a nonphotosynthetic plastid enclosed by four membranes resulting from a secondary endosymbiosis. Using superresolution microscopy and biochemical techniques, we show that TgATG8 localizes to the outermost membrane of this organelle. We investigated the unusual function of TgATG8 at the apicoplast by generating a conditional knockdown mutant. Depletion of TgATG8 led to rapid loss of the organelle and subsequent intracellular replication defects, indicating that the protein is essential for maintaining apicoplast homeostasis and thus for survival of the tachyzoite stage. More precisely, loss of TgATG8 led to abnormal segregation of the apicoplast into the progeny because of a loss of physical interactions of the organelle with the centrosomes. IMPORTANCE By definition, autophagy is a catabolic process that leads to the digestion and recycling of eukaryotic cellular components. The molecular machinery of autophagy was identified mainly in model organisms such as yeasts but remains poorly characterized in phylogenetically distant apicomplexan parasites. We have uncovered an unusual function for autophagy-related protein ATG8 in Toxoplasma gondii: TgATG8 is crucial for normal replication of the parasite inside its host cell. Seemingly unrelated to the catabolic autophagy process, TgATG8 associates with the outer membrane of the nonphotosynthetic plastid harbored by the parasite called the apicoplast, and there it plays an important role in the centrosome-driven inheritance of the organelle during cell division. This not only reveals an unexpected function for an autophagy-related protein but also sheds new light on the division process of an organelle that is vital to a group of important human and animal pathogens.
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1409
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Lou Z, Casali P, Xu Z. Regulation of B Cell Differentiation by Intracellular Membrane-Associated Proteins and microRNAs: Role in the Antibody Response. Front Immunol 2015; 6:537. [PMID: 26579118 PMCID: PMC4620719 DOI: 10.3389/fimmu.2015.00537] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 10/07/2015] [Indexed: 12/17/2022] Open
Abstract
B cells are central to adaptive immunity and their functions in antibody responses are exquisitely regulated. As suggested by recent findings, B cell differentiation is mediated by intracellular membrane structures (including endosomes, lysosomes, and autophagosomes) and protein factors specifically associated with these membranes, including Rab7, Atg5, and Atg7. These factors participate in vesicle formation/trafficking, signal transduction and induction of gene expression to promote antigen presentation, class switch DNA recombination (CSR)/somatic hypermutation (SHM), and generation/maintenance of plasma cells and memory B cells. Their expression is induced in B cells activated to differentiate and further fine-tuned by immune-modulating microRNAs, which coordinates CSR/SHM, plasma cell differentiation, and memory B cell differentiation. These short non-coding RNAs would individually target multiple factors associated with the same intracellular membrane compartments and collaboratively target a single factor in addition to regulating AID and Blimp-1. These, together with regulation of microRNA biogenesis and activities by endosomes and autophagosomes, show that intracellular membranes and microRNAs, two broadly relevant cell constituents, play important roles in balancing gene expression to specify B cell differentiation processes for optimal antibody responses.
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Affiliation(s)
- Zheng Lou
- Department of Microbiology and Immunology, School of Medicine, The University of Texas Health Science Center , San Antonio, TX , USA
| | - Paolo Casali
- Department of Microbiology and Immunology, School of Medicine, The University of Texas Health Science Center , San Antonio, TX , USA
| | - Zhenming Xu
- Department of Microbiology and Immunology, School of Medicine, The University of Texas Health Science Center , San Antonio, TX , USA
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1410
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Yamamoto H, Shima T, Yamaguchi M, Mochizuki Y, Hoshida H, Kakuta S, Kondo-Kakuta C, Noda NN, Inagaki F, Itoh T, Akada R, Ohsumi Y. The Thermotolerant Yeast Kluyveromyces marxianus Is a Useful Organism for Structural and Biochemical Studies of Autophagy. J Biol Chem 2015; 290:29506-18. [PMID: 26442587 DOI: 10.1074/jbc.m115.684233] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Indexed: 11/06/2022] Open
Abstract
Autophagy is a conserved degradation process in which autophagosomes are generated by cooperative actions of multiple autophagy-related (Atg) proteins. Previous studies using the model yeast Saccharomyces cerevisiae have provided various insights into the molecular basis of autophagy; however, because of the modest stability of several Atg proteins, structural and biochemical studies have been limited to a subset of Atg proteins, preventing us from understanding how multiple Atg proteins function cooperatively in autophagosome formation. With the goal of expanding the scope of autophagy research, we sought to identify a novel organism with stable Atg proteins that would be advantageous for in vitro analyses. Thus, we focused on a newly isolated thermotolerant yeast strain, Kluyveromyces marxianus DMKU3-1042, to utilize as a novel system elucidating autophagy. We developed experimental methods to monitor autophagy in K. marxianus cells, identified the complete set of K. marxianus Atg homologs, and confirmed that each Atg homolog is engaged in autophagosome formation. Biochemical and bioinformatic analyses revealed that recombinant K. marxianus Atg proteins have superior thermostability and solubility as compared with S. cerevisiae Atg proteins, probably due to the shorter primary sequences of KmAtg proteins. Furthermore, bioinformatic analyses showed that more than half of K. marxianus open reading frames are relatively short in length. These features make K. marxianus proteins broadly applicable as tools for structural and biochemical studies, not only in the autophagy field but also in other fields.
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Affiliation(s)
- Hayashi Yamamoto
- From the Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503,
| | - Takayuki Shima
- From the Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503
| | - Masaya Yamaguchi
- the Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0812
| | - Yuh Mochizuki
- the Laboratory of In Silico Functional Genomics, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501
| | - Hisashi Hoshida
- the Department of Applied Molecular Bioscience, Yamaguchi University Graduate School of Medicine, Ube 755-8611, and
| | - Soichiro Kakuta
- From the Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503
| | - Chika Kondo-Kakuta
- From the Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503
| | - Nobuo N Noda
- the Institute of Microbial Chemistry, Tokyo 141-0021, Japan
| | - Fuyuhiko Inagaki
- the Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0812
| | - Takehiko Itoh
- the Laboratory of In Silico Functional Genomics, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501
| | - Rinji Akada
- the Department of Applied Molecular Bioscience, Yamaguchi University Graduate School of Medicine, Ube 755-8611, and
| | - Yoshinori Ohsumi
- From the Frontier Research Center, Tokyo Institute of Technology, Yokohama 226-8503,
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1411
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Abstract
When nerve injury occurs, the axon and myelin fragments distal to the injury site have to be cleared away before repair. In this issue, Gomez-Sanchez et al. (2015; J. Cell Biol. http://dx.doi.org/10.1083/jcb.201503019) find that clearance of the damaged myelin within Schwann cells occurs not by phagocytosis but rather via selective autophagy, in a process they term "myelinophagy."
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Affiliation(s)
- Michael Thumm
- University Medicine, Institute of Cellular Biochemistry, University of Göttingen, D-37073 Goettingen, Germany
| | - Mikael Simons
- Department of Neurology, University of Göttingen, D-37073 Goettingen, Germany Cellular Neuroscience, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
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1412
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Magraoui FE, Reidick C, Meyer HE, Platta HW. Autophagy-Related Deubiquitinating Enzymes Involved in Health and Disease. Cells 2015; 4:596-621. [PMID: 26445063 PMCID: PMC4695848 DOI: 10.3390/cells4040596] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/15/2015] [Accepted: 09/30/2015] [Indexed: 02/06/2023] Open
Abstract
Autophagy is an evolutionarily-conserved process that delivers diverse cytoplasmic components to the lysosomal compartment for either recycling or degradation. This involves the removal of protein aggregates, the turnover of organelles, as well as the elimination of intracellular pathogens. In this situation, when only specific cargoes should be targeted to the lysosome, the potential targets can be selectively marked by the attachment of ubiquitin in order to be recognized by autophagy-receptors. Ubiquitination plays a central role in this process, because it regulates early signaling events during the induction of autophagy and is also used as a degradation-tag on the potential autophagic cargo protein. Here, we review how the ubiquitin-dependent steps of autophagy are balanced or counteracted by deubiquitination events. Moreover, we highlight the functional role of the corresponding deubiquitinating enzymes and discuss how they might be involved in the occurrence of cancer, neurodegenerative diseases or infection with pathogenic bacteria.
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Affiliation(s)
- Fouzi El Magraoui
- Biomedizinische Forschung, Human Brain Proteomics II, Leibniz-Institut für Analytische Wissenschaften - ISAS -e.V. 44139 Dortmund, Germany.
| | - Christina Reidick
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, 44801 Bochum, Germany.
| | - Hemut E Meyer
- Biomedizinische Forschung, Human Brain Proteomics II, Leibniz-Institut für Analytische Wissenschaften - ISAS -e.V. 44139 Dortmund, Germany.
| | - Harald W Platta
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, 44801 Bochum, Germany.
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1413
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Saez-Atienzar S, Bonet-Ponce L, da Casa C, Perez-Dolz L, Blesa JR, Nava E, Galindo MF, Jordan J. Bcl-xL-mediated antioxidant function abrogates the disruption of mitochondrial dynamics induced by LRRK2 inhibition. Biochim Biophys Acta Mol Basis Dis 2015; 1862:20-31. [PMID: 26435084 DOI: 10.1016/j.bbadis.2015.09.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 09/17/2015] [Accepted: 09/29/2015] [Indexed: 12/30/2022]
Abstract
We have used the human neuroblastoma cell line SH-SY5Y overexpressing Bcl-xL (SH-SY5Y/Bcl-xL) to clarify the effects of this mitochondrial protein on the control of mitochondrial dynamics and the autophagic processes which occur after the inhibition of leucine-rich repeat kinase 2 (LRRK2) with GSK2578215A. In wild type (SH-SY5Y/Neo) cells, GSK2578215A (1nM) caused a disruption of mitochondrial morphology and an imbalance in intracellular reactive oxygen species (ROS) as indicated by an increase in dichlorofluorescein fluorescence and 4-hydroxynonenal. However, SH-SY5Y/Bcl-xL cells under GSK2578215A treatment, unlike the wild type, preserved a high mitochondrial membrane potential and did not exhibit apoptotical chromatins. In contrast to wild type cells, in SH-SY5Y/Bcl-xL cells, GSK2578215A did not induce mitochondrial translocation of neither dynamin related protein-1 nor the proapoptotic protein, Bax. In SH-SY5Y/Neo, but not SH-SY5Y/Bcl-xL cells, mitochondrial fragmentation elicited by GSK2578215A precedes an autophagic response. Furthermore, the overexpression of Bcl-xL protein restores the autophagic flux pathway disrupted by this inhibitor. SH-SY5Y/Neo, but not SH-SY5Y/Bcl-xL cells, responded to LRRK2 inhibition by an increase in the levels of acetylated tubulin, indicating that this was abrogated by Bcl-xL overexpression. This hyperacetylation of tubulin took place earlier than any of the above-mentioned events suggesting that it is involved in the autophagic flux interruption. Pre-treatment with tempol prevented the GSK2578215A-induced mitochondrial fragmentation, autophagy and the rise in acetylated tubulin in SH-SY5Y/Neo cells. Thus, these data support the notion that ROS act as a second messenger connexion between LRRK2 inhibition and these deleterious responses, which are markedly alleviated by the Bcl-xL-mediated ROS generation blockade.
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Affiliation(s)
- Sara Saez-Atienzar
- Grupo de Neurofarmacología, Dpto. Ciencias Médicas, Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, IDINE, Albacete, Spain; Facultad de Medicina y Odontología, Universidad Católica de Valencia ¨San Vicente Mártir, Valencia, Spain; Unidad de Neuropsicofarmacología Traslacional, Complejo Hospitalario Universitario de Albacete, Albacete, Spain
| | - Luis Bonet-Ponce
- Facultad de Medicina y Odontología, Universidad Católica de Valencia ¨San Vicente Mártir, Valencia, Spain
| | - Carmen da Casa
- Grupo de Neurofarmacología, Dpto. Ciencias Médicas, Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, IDINE, Albacete, Spain; Unidad de Neuropsicofarmacología Traslacional, Complejo Hospitalario Universitario de Albacete, Albacete, Spain
| | - Laura Perez-Dolz
- Grupo de Neurofarmacología, Dpto. Ciencias Médicas, Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, IDINE, Albacete, Spain; Unidad de Neuropsicofarmacología Traslacional, Complejo Hospitalario Universitario de Albacete, Albacete, Spain
| | - Jose R Blesa
- Facultad de Medicina y Odontología, Universidad Católica de Valencia ¨San Vicente Mártir, Valencia, Spain
| | - Eduardo Nava
- Grupo de Neurofarmacología, Dpto. Ciencias Médicas, Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, IDINE, Albacete, Spain
| | - Maria F Galindo
- Unidad de Neuropsicofarmacología Traslacional, Complejo Hospitalario Universitario de Albacete, Albacete, Spain.
| | - Joaquín Jordan
- Grupo de Neurofarmacología, Dpto. Ciencias Médicas, Facultad de Medicina de Albacete, Universidad de Castilla-La Mancha, IDINE, Albacete, Spain.
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1414
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Yao F, Lv YC, Zhang M, Xie W, Tan YL, Gong D, Cheng HP, Liu D, Li L, Liu XY, Zheng XL, Tang CK. Apelin-13 impedes foam cell formation by activating Class III PI3K/Beclin-1-mediated autophagic pathway. Biochem Biophys Res Commun 2015; 466:637-43. [DOI: 10.1016/j.bbrc.2015.09.045] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 09/08/2015] [Indexed: 12/24/2022]
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1415
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Meijer AJ, Lorin S, Blommaart EF, Codogno P. Regulation of autophagy by amino acids and MTOR-dependent signal transduction. Amino Acids 2015; 47:2037-63. [PMID: 24880909 PMCID: PMC4580722 DOI: 10.1007/s00726-014-1765-4] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Accepted: 05/12/2014] [Indexed: 01/05/2023]
Abstract
Amino acids not only participate in intermediary metabolism but also stimulate insulin-mechanistic target of rapamycin (MTOR)-mediated signal transduction which controls the major metabolic pathways. Among these is the pathway of autophagy which takes care of the degradation of long-lived proteins and of the elimination of damaged or functionally redundant organelles. Proper functioning of this process is essential for cell survival. Dysregulation of autophagy has been implicated in the etiology of several pathologies. The history of the studies on the interrelationship between amino acids, MTOR signaling and autophagy is the subject of this review. The mechanisms responsible for the stimulation of MTOR-mediated signaling, and the inhibition of autophagy, by amino acids have been studied intensively in the past but are still not completely clarified. Recent developments in this field are discussed.
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Affiliation(s)
- Alfred J Meijer
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
| | - Séverine Lorin
- UPRES EA4530, Université Paris-Sud, Faculté de Pharmacie, 5 rue Jean-Baptiste Clément, 92296, Châtenay-Malabry Cedex, France
| | - Edward F Blommaart
- Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands
| | - Patrice Codogno
- INSERM U1151-CNRS UMR 8253, Université Paris Descartes, 14 rue Maria Helena Vieira Da Silva CS61431, 75993, Paris Cedex 14, France
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1416
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Hu G, McQuiston T, Bernard A, Park YD, Qiu J, Vural A, Zhang N, Waterman SR, Blewett NH, Myers TG, Kehrl JH, Uzel G, Klionsky DJ, Williamson PR. Tor-dependent post-transcriptional regulation of autophagy: Implications for cancer therapeutics. Mol Cell Oncol 2015; 3:e1078923. [PMID: 27857968 DOI: 10.1080/23723556.2015.1078923] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 07/28/2015] [Accepted: 07/29/2015] [Indexed: 10/23/2022]
Abstract
Paradoxically, both anticancer immunosurveillance and tumor progression have been associated with intact autophagy, which is regulated by the target of rapamycin (Tor1). Here, we describe the potential impact on the design of cancer therapeutics of a newly described highly conserved post-transcriptional mechanism whereby Tor regulates autophagy.
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Affiliation(s)
- Guowu Hu
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Travis McQuiston
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Amélie Bernard
- Life Sciences Institute, University of Michigan , Ann Arbor, MI, USA
| | - Yoon-Dong Park
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Jin Qiu
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Ali Vural
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Nannan Zhang
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Scott R Waterman
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Nathan H Blewett
- Intramural Research Program in Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health , Bethesda , MD, USA
| | - Timothy G Myers
- Genomic Technologies Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health , MD, USA
| | - John H Kehrl
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Gulbu Uzel
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
| | - Daniel J Klionsky
- Life Sciences Institute, University of Michigan , Ann Arbor, MI, USA
| | - Peter R Williamson
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD, USA
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1417
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High-fat diet induces cardiomyocyte apoptosis via the inhibition of autophagy. Eur J Nutr 2015; 55:2245-54. [DOI: 10.1007/s00394-015-1034-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 09/01/2015] [Indexed: 10/23/2022]
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1418
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Jin X, Li F, Zheng X, Liu Y, Hirayama R, Liu X, Li P, Zhao T, Dai Z, Li Q. Carbon ions induce autophagy effectively through stimulating the unfolded protein response and subsequent inhibiting Akt phosphorylation in tumor cells. Sci Rep 2015; 5:13815. [PMID: 26338671 PMCID: PMC4559768 DOI: 10.1038/srep13815] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Accepted: 08/06/2015] [Indexed: 01/12/2023] Open
Abstract
Heavy ion beams have advantages over conventional radiation in radiotherapy due to their superb biological effectiveness and dose conformity. However, little information is currently available concerning the cellular and molecular basis for heavy ion radiation-induced autophagy. In this study, human glioblastoma SHG44 and cervical cancer HeLa cells were irradiated with carbon ions of different linear energy transfers (LETs) and X-rays. Our results revealed increased LC3-II and decreased p62 levels in SHG44 and HeLa cells post-irradiation, indicating marked induction of autophagy. The autophagic level of tumor cells after irradiation increased in a LET-dependent manner and was inversely correlated with the sensitivity to radiations of various qualities. Furthermore, we demonstrated that high-LET carbon ions stimulated the unfolded protein response (UPR) and mediated autophagy via the UPR-eIF2α-CHOP-Akt signaling axis. High-LET carbon ions more severely inhibited Akt-mTOR through UPR to effectively induce autophagy. Thus, the present data could serve as an important radiobiological basis to further understand the molecular mechanisms by which high-LET radiation induces cell death.
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Affiliation(s)
- Xiaodong Jin
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China
| | - Feifei Li
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaogang Zheng
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan Liu
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ryoichi Hirayama
- Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan
| | - Xiongxiong Liu
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China
| | - Ping Li
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China
| | - Ting Zhao
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China
| | - Zhongying Dai
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China
| | - Qiang Li
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China.,Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou 730000, China
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1419
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Horenkamp FA, Kauffman KJ, Kohler LJ, Sherwood RK, Krueger KP, Shteyn V, Roy CR, Melia TJ, Reinisch KM. The Legionella Anti-autophagy Effector RavZ Targets the Autophagosome via PI3P- and Curvature-Sensing Motifs. Dev Cell 2015; 34:569-76. [PMID: 26343456 DOI: 10.1016/j.devcel.2015.08.010] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 06/18/2015] [Accepted: 08/12/2015] [Indexed: 02/06/2023]
Abstract
Autophagy is a conserved membrane transport pathway used to destroy pathogenic microbes that access the cytosol of cells. The intracellular pathogen Legionella pneumophila interferes with autophagy by delivering an effector protein, RavZ, into the host cytosol. RavZ acts by cleaving membrane-conjugated Atg8/LC3 proteins from pre-autophagosomal structures. Its remarkable efficiency allows minute quantities of RavZ to block autophagy throughout the cell. To understand how RavZ targets pre-autophagosomes and specifically acts only on membrane-associated Atg8 proteins, we elucidated its structure. Revealed is a catalytic domain related in fold to Ulp family deubiquitinase-like enzymes and a C-terminal PI3P-binding module. RavZ targets the autophagosome via the PI3P-binding module and a catalytic domain helix, and it preferentially binds high-curvature membranes, intimating localization to highly curved domains in autophagosome intermediate membranes. RavZ-membrane interactions enhance substrate affinity, providing a mechanism for interfacial activation that also may be used by host autophagy proteins engaging only lipidated Atg8 proteins.
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Affiliation(s)
- Florian A Horenkamp
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Karlina J Kauffman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Lara J Kohler
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Racquel K Sherwood
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Kathryn P Krueger
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Vladimir Shteyn
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Craig R Roy
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Thomas J Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
| | - Karin M Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
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1420
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Beilina A, Cookson MR. Genes associated with Parkinson's disease: regulation of autophagy and beyond. J Neurochem 2015. [PMID: 26223426 DOI: 10.1111/jnc.13266] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Substantial progress has been made in the genetic basis of Parkinson's disease (PD). In particular, by identifying genes that segregate with inherited PD or show robust association with sporadic disease, and by showing the same genes are found on both lists, we have generated an outline of the cause of this condition. Here, we will discuss what those genes tell us about the underlying biology of PD. We specifically discuss the relationships between protein products of PD genes and show that common links include regulation of the autophagy-lysosome system, an important way by which cells recycle proteins and organelles. We also discuss whether all PD genes should be considered to be in the same pathway and propose that in some cases the relationships are closer, whereas in other cases the interactions are more distant and might be considered separate. Beilina and Cookson review the links between genes for Parkinson's disease (red) and the autophagy-lysosomal system. They propose the hypothesis that many of the known PD genes can be assigned to pathways that affect (I) turnover of mitochondria via mitophagy (II) turnover of several vesicular structures via macroautophagy or chaperone-mediated autophagy or (III) general lysosome function. This article is part of a special issue on Parkinson disease.
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Affiliation(s)
- Alexandra Beilina
- Cell Biology and Gene Expression Section, Laboratory of Neurogenetics, National Institute on Aging, Bethesda, Maryland, USA
| | - Mark R Cookson
- Cell Biology and Gene Expression Section, Laboratory of Neurogenetics, National Institute on Aging, Bethesda, Maryland, USA.
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1421
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Liu XM, Sun LL, Hu W, Ding YH, Dong MQ, Du LL. ESCRTs Cooperate with a Selective Autophagy Receptor to Mediate Vacuolar Targeting of Soluble Cargos. Mol Cell 2015; 59:1035-42. [DOI: 10.1016/j.molcel.2015.07.034] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 07/08/2015] [Accepted: 07/31/2015] [Indexed: 11/16/2022]
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1422
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Orfali N, O'Donovan TR, Nyhan MJ, Britschgi A, Tschan MP, Cahill MR, Mongan NP, Gudas LJ, McKenna SL. Induction of autophagy is a key component of all-trans-retinoic acid-induced differentiation in leukemia cells and a potential target for pharmacologic modulation. Exp Hematol 2015; 43:781-93.e2. [PMID: 25986473 PMCID: PMC4948855 DOI: 10.1016/j.exphem.2015.04.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Revised: 04/27/2015] [Accepted: 04/29/2015] [Indexed: 12/16/2022]
Abstract
Acute myeloid leukemia (AML) is characterized by the accumulation of immature blood cell precursors in the bone marrow. Pharmacologically overcoming the differentiation block in this condition is an attractive therapeutic avenue, which has achieved success only in a subtype of AML, acute promyelocytic leukemia (APL). Attempts to emulate this success in other AML subtypes have thus far been unsuccessful. Autophagy is a conserved protein degradation pathway with important roles in mammalian cell differentiation, particularly within the hematopoietic system. In the study described here, we investigated the functional importance of autophagy in APL cell differentiation. We found that autophagy is increased during all-trans-retinoic acid (ATRA)-induced granulocytic differentiation of the APL cell line NB4 and that this is associated with increased expression of LC3II and GATE-16 proteins involved in autophagosome formation. Autophagy inhibition, using either drugs (chloroquine/3-methyladenine) or short-hairpin RNA targeting the essential autophagy gene ATG7, attenuates myeloid differentiation. Importantly, we found that enhancing autophagy promotes ATRA-induced granulocytic differentiation of an ATRA-resistant derivative of the non-APL AML HL60 cell line (HL60-Diff-R). These data support the development of strategies to stimulate autophagy as a novel approach to promote differentiation in AML.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Adenine/analogs & derivatives
- Adenine/pharmacology
- Antineoplastic Agents/pharmacology
- Antirheumatic Agents/pharmacology
- Autophagy/drug effects
- Autophagy-Related Protein 7
- Autophagy-Related Protein 8 Family
- Cell Differentiation/drug effects
- Chloroquine/pharmacology
- Granulocytes/metabolism
- Granulocytes/pathology
- HL-60 Cells
- Humans
- Leukemia, Promyelocytic, Acute/drug therapy
- Leukemia, Promyelocytic, Acute/genetics
- Leukemia, Promyelocytic, Acute/metabolism
- Leukemia, Promyelocytic, Acute/pathology
- Microfilament Proteins/genetics
- Microfilament Proteins/metabolism
- Microtubule-Associated Proteins/genetics
- Microtubule-Associated Proteins/metabolism
- Neoplasm Proteins/antagonists & inhibitors
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Tretinoin/pharmacology
- Ubiquitin-Activating Enzymes/antagonists & inhibitors
- Ubiquitin-Activating Enzymes/genetics
- Ubiquitin-Activating Enzymes/metabolism
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Affiliation(s)
- Nina Orfali
- Cork Cancer Research Centre, Leslie C. Quick, Jr., Laboratory, Biosciences Institute, University College Cork, Cork, Ireland; Department of Hematology, Cork University Hospital, Cork, Ireland; Department of Pharmacology, Weill Cornell Medical College, New York, New York, USA
| | - Tracey R O'Donovan
- Cork Cancer Research Centre, Leslie C. Quick, Jr., Laboratory, Biosciences Institute, University College Cork, Cork, Ireland
| | - Michelle J Nyhan
- Cork Cancer Research Centre, Leslie C. Quick, Jr., Laboratory, Biosciences Institute, University College Cork, Cork, Ireland
| | - Adrian Britschgi
- Division of Experimental Pathology, Institute of Pathology, University of Bern, Bern, Switzerland
| | - Mario P Tschan
- Division of Experimental Pathology, Institute of Pathology, University of Bern, Bern, Switzerland
| | - Mary R Cahill
- Department of Hematology, Cork University Hospital, Cork, Ireland
| | - Nigel P Mongan
- Department of Pharmacology, Weill Cornell Medical College, New York, New York, USA; Faculty of Medicine and Health Science, School of Veterinary Medicine and Science, University of Nottingham, Nottingham, United Kingdom
| | - Lorraine J Gudas
- Department of Pharmacology, Weill Cornell Medical College, New York, New York, USA
| | - Sharon L McKenna
- Cork Cancer Research Centre, Leslie C. Quick, Jr., Laboratory, Biosciences Institute, University College Cork, Cork, Ireland.
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1423
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Xiao L, Xian H, Lee KY, Xiao B, Wang H, Yu F, Shen HM, Liou YC. Death-associated Protein 3 Regulates Mitochondrial-encoded Protein Synthesis and Mitochondrial Dynamics. J Biol Chem 2015; 290:24961-74. [PMID: 26306039 DOI: 10.1074/jbc.m115.673343] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Indexed: 01/13/2023] Open
Abstract
Mitochondrial morphologies change over time and are tightly regulated by dynamic machinery proteins such as dynamin-related protein 1 (Drp1), mitofusion 1/2, and optic atrophy 1 (OPA1). However, the detailed mechanisms of how these molecules cooperate to mediate fission and fusion remain elusive. DAP3 is a mitochondrial ribosomal protein that involves in apoptosis, but its biological function has not been well characterized. Here, we demonstrate that DAP3 specifically localizes in the mitochondrial matrix. Knockdown of DAP3 in mitochondria leads to defects in mitochondrial-encoded protein synthesis and abnormal mitochondrial dynamics. Moreover, depletion of DAP3 dramatically decreases the phosphorylation of Drp1 at Ser-637 on mitochondria, enhancing the retention time of Drp1 puncta on mitochondria during the fission process. Furthermore, autophagy is inhibited in the DAP3-depleted cells, which sensitizes cells to different types of death stimuli. Together, our results suggest that DAP3 plays important roles in mitochondrial function and dynamics, providing new insights into the mechanism of a mitochondrial ribosomal protein function in cell death.
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Affiliation(s)
- Lin Xiao
- From the Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Hongxu Xian
- From the Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Kit Yee Lee
- From the Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Bin Xiao
- From the Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Hongyan Wang
- the Neuroscience and Behavioural Disorders Program, Duke-NUS Graduate Medical School, Singapore 169857, the NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117573
| | - Fengwei Yu
- the NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117573, the Temasek Life Sciences Laboratory and Department of Biological Sciences, National University of Singapore, 1 Research Link, Singapore 117604, and
| | - Han-Ming Shen
- the Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore
| | - Yih-Cherng Liou
- From the Department of Biological Sciences, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore 117543, the NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117573,
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1424
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de Iriarte Rodríguez R, Pulido S, Rodríguez-de la Rosa L, Magariños M, Varela-Nieto I. Age-regulated function of autophagy in the mouse inner ear. Hear Res 2015; 330:39-50. [PMID: 26235979 DOI: 10.1016/j.heares.2015.07.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 07/22/2015] [Accepted: 07/29/2015] [Indexed: 12/13/2022]
Abstract
Autophagy is a highly conserved catabolic process essential for embryonic development and adult homeostasis. The autophagic machinery supplies energy by recycling intracellular components and facilitates the removal of apoptotic cells. In the inner ear, autophagy has been reported to play roles during early development in the chicken embryo and in the response to otic injury in the adult mouse. However, there are no studies on the expression of the autophagy machinery in the postnatal and adult inner ear. Insulin-like growth factor 1 (IGF-1) is one of the factors that regulate both otic development and cochlear postnatal maturation and function. Here, we hypothesised that autophagy could be one of the processes involved in the cochlear development and functional maturation. We report that autophagy-related genes (ATG) Becn1, Atg4g and Atg5 are expressed in the mouse cochlea, vestibular system and brainstem cochlear nuclei from late developmental stages to adulthood. Atg9 was studied in the mouse cochlea and showed a similar pattern. The presence of autophagic flux was confirmed by decreased sequestosome 1 (SQSTM1/p62) and increased relative levels of microtubule-associated protein light chain 3-II (LC3-II). Inner ear autophagy flux is developmentally regulated and is lower at perinatal stages than in the adult mouse, where an expression plateau is reached at the age of two-months, coinciding with the age at which full functional activity is reached. Expression is maintained in adult mice and declines after the age of twelve months. LC3B labelling showed that autophagy was primarily associated with spiral ganglion neurons. Over time, Igf1 wild type mice showed lower expression of genes coding for IGF-1 high affinity receptor and the family factor IGF-2 than null mice. Parallel analysis of autophagy machinery gene expression showed no significant differences between the genotypes over the lifespan of the null mice. Taken together, these results show that the autophagy machinery expression in the inner ear is regulated with age but is not compromised by the chronic absence of IGF-1. Our data also strongly support that the up-regulation of autophagy machinery genes is concomitant with the functional maturation of the inner ear.
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Affiliation(s)
- Rocío de Iriarte Rodríguez
- Instituto de Investigaciones Biomédicas "Alberto Sols", CSIC-UAM, Madrid, Spain; CIBERER, Unit 761, Instituto de Salud Carlos III, Madrid, Spain
| | - Sara Pulido
- Instituto de Investigaciones Biomédicas "Alberto Sols", CSIC-UAM, Madrid, Spain
| | - Lourdes Rodríguez-de la Rosa
- Instituto de Investigaciones Biomédicas "Alberto Sols", CSIC-UAM, Madrid, Spain; CIBERER, Unit 761, Instituto de Salud Carlos III, Madrid, Spain; IdiPAZ, Instituto de Investigación Sanitaria, Madrid, Spain
| | - Marta Magariños
- Instituto de Investigaciones Biomédicas "Alberto Sols", CSIC-UAM, Madrid, Spain; CIBERER, Unit 761, Instituto de Salud Carlos III, Madrid, Spain; Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain.
| | - Isabel Varela-Nieto
- Instituto de Investigaciones Biomédicas "Alberto Sols", CSIC-UAM, Madrid, Spain; CIBERER, Unit 761, Instituto de Salud Carlos III, Madrid, Spain; IdiPAZ, Instituto de Investigación Sanitaria, Madrid, Spain
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1425
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Awad O, Sarkar C, Panicker LM, Miller D, Zeng X, Sgambato JA, Lipinski MM, Feldman RA. Altered TFEB-mediated lysosomal biogenesis in Gaucher disease iPSC-derived neuronal cells. Hum Mol Genet 2015. [PMID: 26220978 DOI: 10.1093/hmg/ddv297] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Gaucher disease (GD) is caused by mutations in the GBA1 gene, which encodes the lysosomal enzyme glucocerebrosidase (GCase). The severe forms of GD are associated with neurodegeneration with either rapid (Type 2) or slow progression (Type 3). Although the neurodegenerative process in GD has been linked to lysosomal dysfunction, the mechanisms involved are largely unknown. To identify the lysosomal alterations in GD neurons and uncover the mechanisms involved, we used induced pluripotent stem cells (iPSCs) derived from patients with GD. In GD iPSC-derived neuronal cells (iPSC-NCs), GBA1 mutations caused widespread lysosomal depletion, and a block in autophagic flux due to defective lysosomal clearance of autophagosomes. Autophagy induction by rapamycin treatment in GD iPSC-NCs led to cell death. Further analysis showed that in GD iPSC-NCs, expression of the transcription factor EB (TFEB), the master regulator of lysosomal genes, and lysosomal gene expression, were significantly downregulated. There was also reduced stability of the TFEB protein and altered lysosomal protein biosynthesis. Treatment of mutant iPSC-NCs with recombinant GCase (rGCase) reverted the lysosomal depletion and autophagy block. The effect of rGCase on restoring lysosomal numbers in mutant cells was enhanced in the presence of overexpressed TFEB, but TFEB overexpression alone did not reverse the lysosomal depletion phenotype. Our results suggest that GBA1 mutations interfere with TFEB-mediated lysosomal biogenesis, and that the action of GCase in maintaining a functioning pool of lysosomes is exerted in part through TFEB. The lysosomal alterations described here are likely to be a major determinant in GBA1-associated neurodegeneration.
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Affiliation(s)
- Ola Awad
- Department of Microbiology and Immunology
| | | | | | | | - Xianmin Zeng
- Buck Institute for Age Research, Novato, CA, USA
| | | | - Marta M Lipinski
- Department of Anesthesiology, Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA and
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1426
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Descloux C, Ginet V, Clarke PGH, Puyal J, Truttmann AC. Neuronal death after perinatal cerebral hypoxia-ischemia: Focus on autophagy-mediated cell death. Int J Dev Neurosci 2015. [PMID: 26225751 DOI: 10.1016/j.ijdevneu.2015.06.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Neonatal hypoxic-ischemic encephalopathy is a critical cerebral event occurring around birth with high mortality and neurological morbidity associated with long-term invalidating sequelae. In view of the great clinical importance of this condition and the lack of very efficacious neuroprotective strategies, it is urgent to better understand the different cell death mechanisms involved with the ultimate aim of developing new therapeutic approaches. The morphological features of three different cell death types can be observed in models of perinatal cerebral hypoxia-ischemia: necrotic, apoptotic and autophagic cell death. They may be combined in the same dying neuron. In the present review, we discuss the different cell death mechanisms involved in neonatal cerebral hypoxia-ischemia with a special focus on how autophagy may be involved in neuronal death, based: (1) on experimental models of perinatal hypoxia-ischemia and stroke, and (2) on the brains of human neonates who suffered from neonatal hypoxia-ischemia.
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Affiliation(s)
- C Descloux
- Department of Fundamental Neurosciences (DNF), University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland; Clinic of Neonatology, Department of Pediatrics and Pediatric Surgery, University Hospital Center and University of Lausanne, 1011 Lausanne, Vaud, Switzerland
| | - V Ginet
- Department of Fundamental Neurosciences (DNF), University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - P G H Clarke
- Department of Fundamental Neurosciences (DNF), University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland
| | - J Puyal
- Department of Fundamental Neurosciences (DNF), University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland; Clinic of Neonatology, Department of Pediatrics and Pediatric Surgery, University Hospital Center and University of Lausanne, 1011 Lausanne, Vaud, Switzerland
| | - A C Truttmann
- Department of Fundamental Neurosciences (DNF), University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland; Clinic of Neonatology, Department of Pediatrics and Pediatric Surgery, University Hospital Center and University of Lausanne, 1011 Lausanne, Vaud, Switzerland.
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1427
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Patergnani S, Missiroli S, Marchi S, Giorgi C. Mitochondria-Associated Endoplasmic Reticulum Membranes Microenvironment: Targeting Autophagic and Apoptotic Pathways in Cancer Therapy. Front Oncol 2015; 5:173. [PMID: 26284195 PMCID: PMC4515599 DOI: 10.3389/fonc.2015.00173] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 07/10/2015] [Indexed: 12/11/2022] Open
Abstract
Autophagy is a tightly regulated catabolic pathway that terminates in the lysosomal compartment after the formation of a cytoplasmic vacuole that engulfs macromolecules and organelles. Notably, autophagy is associated with several human pathophysiological conditions, playing either a cytoprotective or cytopathic role. Many studies have investigated the role of autophagy in cancer. However, whether autophagy suppresses tumorigenesis or provides cancer cells with a rescue mechanism under unfavorable conditions remains unclear. Mitochondria-associated membranes (MAMs) are juxtaposed between the endoplasmic reticulum and mitochondria and have been identified as critical hubs in the regulation of apoptosis and tumor growth. One key function of MAMs is to provide asylum to a number of proteins with tumor suppressor and oncogenic properties. Accordingly, mechanistic studies during tumor progression suggest a strong involvement of these proteins at various steps of the autophagic process. This paper discusses the present state of our knowledge about the intimate molecular networks between MAMs and autophagy in cancer cells and addresses how these networks might be manipulated to improve anticancer therapeutics.
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Affiliation(s)
- Simone Patergnani
- Laboratory for Technologies of Advanced Therapies (LTTA), Section of Pathology, Oncology and Experimental Biology, Department of Morphology, Surgery and Experimental Medicine, University of Ferrara , Ferrara , Italy
| | - Sonia Missiroli
- Laboratory for Technologies of Advanced Therapies (LTTA), Section of Pathology, Oncology and Experimental Biology, Department of Morphology, Surgery and Experimental Medicine, University of Ferrara , Ferrara , Italy
| | - Saverio Marchi
- Laboratory for Technologies of Advanced Therapies (LTTA), Section of Pathology, Oncology and Experimental Biology, Department of Morphology, Surgery and Experimental Medicine, University of Ferrara , Ferrara , Italy
| | - Carlotta Giorgi
- Laboratory for Technologies of Advanced Therapies (LTTA), Section of Pathology, Oncology and Experimental Biology, Department of Morphology, Surgery and Experimental Medicine, University of Ferrara , Ferrara , Italy
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1428
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Parallel damage in mitochondrial and lysosomal compartments promotes efficient cell death with autophagy: The case of the pentacyclic triterpenoids. Sci Rep 2015. [PMID: 26213355 PMCID: PMC4515638 DOI: 10.1038/srep12425] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The role of autophagy in cell death is still controversial and a lot of debate has concerned the transition from its pro-survival to its pro-death roles. The similar structure of the triterpenoids Betulinic (BA) and Oleanolic (OA) acids allowed us to prove that this transition involves parallel damage in mitochondria and lysosome. After treating immortalized human skin keratinocytes (HaCaT) with either BA or OA, we evaluated cell viability, proliferation and mechanism of cell death, function and morphology of mitochondria and lysosomes, and the status of the autophagy flux. We also quantified the interactions of BA and OA with membrane mimics, both in-vitro and in-silico. Essentially, OA caused mitochondrial damage that relied on autophagy to rescue cellular homeostasis, which failed upon lysosomal inhibition by Chloroquine or Bafilomycin-A1. BA caused parallel damage on mitochondria and lysosome, turning autophagy into a destructive process. The higher cytotoxicity of BA correlated with its stronger efficiency in damaging membrane mimics. Based on these findings, we underlined the concept that autophagy will turn into a destructive outcome when there is parallel damage in mitochondrial and lysosomal membranes. We trust that this concept will help the development of new drugs against aggressive cancers.
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1429
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Ahn HH, Oh Y, Lee H, Lee W, Chang JW, Pyo HK, Nah DH, Jung YK. Identification of glucose-6-phosphate transporter as a key regulator functioning at the autophagy initiation step. FEBS Lett 2015; 589:2100-9. [PMID: 25982172 DOI: 10.1016/j.febslet.2015.05.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 05/04/2015] [Accepted: 05/06/2015] [Indexed: 12/11/2022]
Abstract
Autophagy is a catabolic process involving autophagosome formation via lysosome. However, the initiation step of autophagy is largely unknown. We found an interaction between ULK1 and ATG9 in mammalian cells and utilized the interaction to identify novel regulators of autophagy upstream of ULK1. We established a cell-based screening assay employing bimolecular fluorescence complementation. By performing gain-of-function screening, we identified G6PT as an autophagy activator. G6PT enhanced the interaction between N-terminal Venus-tagged ULK1 and C-terminal Venus-tagged ATG9, and increased autophagic flux independent of its transport activity. G6PT negatively regulated mTORC1 activity, demonstrating that G6PT functions upstream of mTORC1 in stimulating autophagy.
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Affiliation(s)
- Hye-Hyun Ahn
- Global Research Laboratory, School of Biological Science, Seoul National University, Gwanak-gu, Seoul, Republic of Korea; Interdisciplinary Graduate Program in Genetic Engineering, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
| | - Yumin Oh
- Russel H. Morgan Department of Radiology and Radiological Science, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Huikyong Lee
- Global Research Laboratory, School of Biological Science, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
| | - WonJae Lee
- Global Research Laboratory, School of Biological Science, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
| | - Jae-Woong Chang
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Ha-Kyung Pyo
- Global Research Laboratory, School of Biological Science, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
| | - Do hyung Nah
- Global Research Laboratory, School of Biological Science, Seoul National University, Gwanak-gu, Seoul, Republic of Korea; Interdisciplinary Graduate Program in Genetic Engineering, Seoul National University, Gwanak-gu, Seoul, Republic of Korea
| | - Yong-Keun Jung
- Global Research Laboratory, School of Biological Science, Seoul National University, Gwanak-gu, Seoul, Republic of Korea; Interdisciplinary Graduate Program in Genetic Engineering, Seoul National University, Gwanak-gu, Seoul, Republic of Korea.
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1430
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Mareninova OA, Sendler M, Malla SR, Yakubov I, French SW, Tokhtaeva E, Vagin O, Oorschot V, Lüllmann-Rauch R, Blanz J, Dawson D, Klumperman J, Lerch MM, Mayerle J, Gukovsky I, Gukovskaya AS. Lysosome associated membrane proteins maintain pancreatic acinar cell homeostasis: LAMP-2 deficient mice develop pancreatitis. Cell Mol Gastroenterol Hepatol 2015; 1:678-694. [PMID: 26693174 PMCID: PMC4673685 DOI: 10.1016/j.jcmgh.2015.07.006] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS The pathogenic mechanism of pancreatitis is poorly understood. Recent evidence implicates defective autophagy in pancreatitis responses; however, the pathways mediating impaired autophagy in pancreas remain largely unknown. Here, we investigate the role of lysosome associated membrane proteins (LAMPs) in pancreatitis. METHODS We analyzed changes in LAMPs in experimental models and human pancreatitis, and the underlying mechanisms: LAMP de-glycosylation and degradation. LAMP cleavage by cathepsin B (CatB) was analyzed by mass spectrometry. We used mice deficient in LAMP-2 to assess its role in pancreatitis. RESULTS Pancreatic levels of LAMP-1 and LAMP-2 greatly decrease across various pancreatitis models and in human disease. Pancreatitis does not trigger LAMPs' bulk de-glycosylation, but induces their degradation via CatB-mediated cleavage of LAMP molecule close to the boundary between luminal and transmembrane domains. LAMP-2 null mice spontaneously develop pancreatitis that begins with acinar cell vacuolization due to impaired autophagic flux, and progresses to severe pancreas damage characterized by trypsinogen activation, macrophage-driven inflammation, and acinar cell death. LAMP-2 deficiency causes a decrease in pancreatic digestive enzymes content, stimulates the basal and inhibits CCK-induced amylase secretion by acinar cells. The effects of LAMP-2 knockout and acute cerulein pancreatitis overlap, which corroborates the pathogenic role of LAMP decrease in experimental pancreatitis models. CONCLUSIONS The results indicate a critical role for LAMPs, particularly LAMP-2, in maintaining pancreatic acinar cell homeostasis, and provide evidence that defective lysosomal function, resulting in impaired autophagy, leads to pancreatitis. Mice with LAMP-2 deficiency present a novel genetic model of human pancreatitis caused by lysosomal/autophagic dysfunction.
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Affiliation(s)
- Olga A. Mareninova
- VA Greater Los Angeles Healthcare System, Los Angeles, California
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | - Matthias Sendler
- Department of Medicine A, University Medicine, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
| | - Sudarshan Ravi Malla
- Department of Medicine A, University Medicine, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
| | - Iskandar Yakubov
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | | | - Elmira Tokhtaeva
- VA Greater Los Angeles Healthcare System, Los Angeles, California
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | - Olga Vagin
- VA Greater Los Angeles Healthcare System, Los Angeles, California
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | - Viola Oorschot
- University Medical Center Utrecht, Utrecht, the Netherlands
- Monash Micro Imaging, Monash University, Melbourne, Victoria, Australia
| | | | - Judith Blanz
- Biochemical Institute, Christian-Albrechts-University Kiel, Kiel, Germany
| | - David Dawson
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | | | - Markus M. Lerch
- Department of Medicine A, University Medicine, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
| | - Julia Mayerle
- Department of Medicine A, University Medicine, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
| | - Ilya Gukovsky
- VA Greater Los Angeles Healthcare System, Los Angeles, California
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
| | - Anna S. Gukovskaya
- VA Greater Los Angeles Healthcare System, Los Angeles, California
- David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California
- Correspondence Address correspondence to: Anna S. Gukovskaya, PhD, Pancreatic Research Group, West Los Angeles VA Healthcare Center, 11301 Wilshire Boulevard, Building 258, Room 340, Los Angeles, California 90073. fax: 310-268-4981.
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1431
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Small-molecule enhancers of autophagy modulate cellular disease phenotypes suggested by human genetics. Proc Natl Acad Sci U S A 2015. [PMID: 26195741 DOI: 10.1073/pnas.1512289112] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Studies of human genetics and pathophysiology have implicated the regulation of autophagy in inflammation, neurodegeneration, infection, and autoimmunity. These findings have motivated the use of small-molecule probes to study how modulation of autophagy affects disease-associated phenotypes. Here, we describe the discovery of the small-molecule probe BRD5631 that is derived from diversity-oriented synthesis and enhances autophagy through an mTOR-independent pathway. We demonstrate that BRD5631 affects several cellular disease phenotypes previously linked to autophagy, including protein aggregation, cell survival, bacterial replication, and inflammatory cytokine production. BRD5631 can serve as a valuable tool for studying the role of autophagy in the context of cellular homeostasis and disease.
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1432
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Lipatova Z, Segev N. A Role for Macro-ER-Phagy in ER Quality Control. PLoS Genet 2015; 11:e1005390. [PMID: 26181331 PMCID: PMC4504476 DOI: 10.1371/journal.pgen.1005390] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 06/23/2015] [Indexed: 11/18/2022] Open
Abstract
The endoplasmic-reticulum quality-control (ERQC) system shuttles misfolded proteins for degradation by the proteasome through the well-defined ER-associated degradation (ERAD) pathway. In contrast, very little is known about the role of autophagy in ERQC. Macro-autophagy, a collection of pathways that deliver proteins through autophagosomes (APs) for degradation in the lysosome (vacuole in yeast), is mediated by autophagy-specific proteins, Atgs, and regulated by Ypt/Rab GTPases. Until recently, the term ER-phagy was used to describe degradation of ER membrane and proteins in the lysosome under stress: either ER stress induced by drugs or whole-cell stress induced by starvation. These two types of stresses induce micro-ER-phagy, which does not use autophagic organelles and machinery, and non-selective autophagy. Here, we characterize the macro-ER-phagy pathway and uncover its role in ERQC. This pathway delivers 20-50% of certain ER-resident membrane proteins to the vacuole and is further induced to >90% by overexpression of a single integral-membrane protein. Even though such overexpression in cells defective in macro-ER-phagy induces the unfolded-protein response (UPR), UPR is not needed for macro-ER-phagy. We show that macro-ER-phagy is dependent on Atgs and Ypt GTPases and its cargo passes through APs. Moreover, for the first time the role of Atg9, the only integral-membrane core Atg, is uncoupled from that of other core Atgs. Finally, three sequential steps of this pathway are delineated: Atg9-dependent exit from the ER en route to autophagy, Ypt1- and core Atgs-mediated pre-autophagsomal-structure organization, and Ypt51-mediated delivery of APs to the vacuole.
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Affiliation(s)
- Zhanna Lipatova
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Nava Segev
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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1433
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Popelka H, Klionsky DJ. Post-translationally-modified structures in the autophagy machinery: an integrative perspective. FEBS J 2015; 282:3474-88. [PMID: 26108642 DOI: 10.1111/febs.13356] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 06/11/2015] [Accepted: 06/19/2015] [Indexed: 01/10/2023]
Abstract
Autophagy is a self-cleaning process that occurs at a constitutive basal level, and is upregulated in response to stress. Macroautophagy (hereafter autophagy) is the most robust type of autophagy, where cargo (specific or nonspecific) is engulfed within a double-membrane structure termed an autophagosome. This process needs to be tightly regulated to maintain normal cellular homeostasis and prevent dysfunction; therefore, a fuller knowledge of the mechanisms of autophagy regulation is crucial for understanding the entire pathway. The autophagy-related proteins are the primary components that carry out autophagy. Many of these proteins are conserved from yeast to humans. A number of significant discoveries with regard to protein functional domains, protein-protein interactions or post-translational modifications of proteins involved in autophagy have been reported in parallel with, or followed by, solving the NMR or crystal structures of autophagy proteins or their protein domains. In the present review, we summarize structural insights gathered to date on the proteins of the autophagy machinery that are modulated by a post-translational modification, specifically phosphorylation, acetylation, ubiquitination and/or SUMOylation. For each protein, we link the reported results with information on the propensity of the corresponding amino acid sequence toward order/disorder. This integrative approach yields a comprehensive overview for each post-translationally modified protein, and also reveals areas for further investigation.
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Affiliation(s)
- Hana Popelka
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
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1434
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Activation of Autophagy by Metals in Chlamydomonas reinhardtii. EUKARYOTIC CELL 2015; 14:964-73. [PMID: 26163317 DOI: 10.1128/ec.00081-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Accepted: 07/05/2015] [Indexed: 12/31/2022]
Abstract
Autophagy is an intracellular self-degradation pathway by which eukaryotic cells recycle their own material in response to specific stress conditions. Exposure to high concentrations of metals causes cell damage, although the effect of metal stress on autophagy has not been explored in photosynthetic organisms. In this study, we investigated the effect of metal excess on autophagy in the model unicellular green alga Chlamydomonas reinhardtii. We show in cells treated with nickel an upregulation of ATG8 that is independent of CRR1, a global regulator of copper signaling in Chlamydomonas. A similar effect on ATG8 was observed with copper and cobalt but not with cadmium or mercury ions. Transcriptome sequencing data revealed an increase in the abundance of the protein degradation machinery, including that responsible for autophagy, and a substantial overlap of that increased abundance with the hydrogen peroxide response in cells treated with nickel ions. Thus, our results indicate that metal stress triggers autophagy in Chlamydomonas and suggest that excess nickel may cause oxidative damage, which in turn activates degradative pathways, including autophagy, to clear impaired components and recover cellular homeostasis.
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1435
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Gomez-Sanchez JA, Carty L, Iruarrizaga-Lejarreta M, Palomo-Irigoyen M, Varela-Rey M, Griffith M, Hantke J, Macias-Camara N, Azkargorta M, Aurrekoetxea I, De Juan VG, Jefferies HBJ, Aspichueta P, Elortza F, Aransay AM, Martínez-Chantar ML, Baas F, Mato JM, Mirsky R, Woodhoo A, Jessen KR. Schwann cell autophagy, myelinophagy, initiates myelin clearance from injured nerves. J Cell Biol 2015; 210:153-68. [PMID: 26150392 PMCID: PMC4494002 DOI: 10.1083/jcb.201503019] [Citation(s) in RCA: 305] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 06/03/2015] [Indexed: 02/07/2023] Open
Abstract
Although Schwann cell myelin breakdown is the universal outcome of a remarkably wide range of conditions that cause disease or injury to peripheral nerves, the cellular and molecular mechanisms that make Schwann cell-mediated myelin digestion possible have not been established. We report that Schwann cells degrade myelin after injury by a novel form of selective autophagy, myelinophagy. Autophagy was up-regulated by myelinating Schwann cells after nerve injury, myelin debris was present in autophagosomes, and pharmacological and genetic inhibition of autophagy impaired myelin clearance. Myelinophagy was positively regulated by the Schwann cell JNK/c-Jun pathway, a central regulator of the Schwann cell reprogramming induced by nerve injury. We also present evidence that myelinophagy is defective in the injured central nervous system. These results reveal an important role for inductive autophagy during Wallerian degeneration, and point to potential mechanistic targets for accelerating myelin clearance and improving demyelinating disease.
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Affiliation(s)
- Jose A Gomez-Sanchez
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, England, UK
| | - Lucy Carty
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, England, UK
| | - Marta Iruarrizaga-Lejarreta
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain
| | - Marta Palomo-Irigoyen
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain
| | - Marta Varela-Rey
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain
| | - Megan Griffith
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, England, UK
| | - Janina Hantke
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, England, UK
| | - Nuria Macias-Camara
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain
| | - Mikel Azkargorta
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain ProteoRed-ISCIII
| | - Igor Aurrekoetxea
- Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque Country (UPV/EHU), 48940 Leioa, Spain Biocruces Health Research Institute, 48903 Barakaldo, Spain
| | - Virginia Gutiérrez De Juan
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain
| | - Harold B J Jefferies
- The Francis Crick Institute, Lincoln's Inn Fields Laboratory, London WC2A 3LY, England, UK
| | - Patricia Aspichueta
- Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque Country (UPV/EHU), 48940 Leioa, Spain Biocruces Health Research Institute, 48903 Barakaldo, Spain
| | - Félix Elortza
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain ProteoRed-ISCIII
| | - Ana M Aransay
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain
| | - María L Martínez-Chantar
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain Biochemistry and Molecular Biology Department, University of the Basque Country (UPV/EHU), E-48080 Bilbao, Spain
| | - Frank Baas
- Department of Genome Analysis, Academic Medical Centre, 1105 AZ Amsterdam, Netherlands
| | - José M Mato
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain
| | - Rhona Mirsky
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, England, UK
| | - Ashwin Woodhoo
- CIC bioGUNE, Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), 48160 Derio, Bizkaia, Spain Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
| | - Kristján R Jessen
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, England, UK
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1436
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Abstract
Autophagy is an intracellular catabolic pathway essential for the recycling of proteins and larger substrates such as aggregates, apoptotic corpses, or long-lived and superfluous organelles whose accumulation could be toxic for cells. Because of its unique feature to engulf part of cytoplasm in double-membrane cup-shaped structures, which further fuses with lysosomes, autophagy is also involved in the elimination of host cell invaders and takes an active part of the innate and adaptive immune response. Its pivotal role in maintenance of the inflammatory balance makes dysfunctions of the autophagy process having important pathological consequences. Indeed, defects in autophagy are associated with a wide range of human diseases including metabolic disorders (diabetes and obesity), inflammatory bowel disease (IBD), and cancer. In this review, we will focus on interrelations that exist between inflammation and autophagy. We will discuss in particular how mediators of inflammation can regulate autophagy activity and, conversely, how autophagy shapes the inflammatory response. Impact of genetic polymorphisms in autophagy-related gene on inflammatory bowel disease will be also discussed.
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1437
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A conserved mechanism of TOR-dependent RCK-mediated mRNA degradation regulates autophagy. Nat Cell Biol 2015; 17:930-942. [PMID: 26098573 PMCID: PMC4528364 DOI: 10.1038/ncb3189] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 05/14/2015] [Indexed: 12/17/2022]
Abstract
Autophagy is an essential eukaryotic pathway requiring tight regulation to maintain homeostasis and preclude disease. Using yeast and mammalian cells, we report a conserved mechanism of autophagy regulation by RNA helicase RCK family members in association with the decapping enzyme Dcp2. Under nutrient-replete conditions, Dcp2 undergoes TOR-dependent phosphorylation and associates with RCK members to form a complex with autophagy-related (ATG) mRNA transcripts, leading to decapping, degradation and autophagy suppression. Simultaneous with the induction of ATG mRNA synthesis, starvation reverses the process, facilitating ATG mRNA accumulation and autophagy induction. This conserved post-transcriptional mechanism modulates fungal virulence and the mammalian inflammasome, the latter providing mechanistic insight into autoimmunity reported in a patient with a PIK3CD/p110δ gain-of-function mutation. We propose a dynamic model wherein RCK family members, in conjunction with Dcp2, function in controlling ATG mRNA stability to govern autophagy, which in turn modulates vital cellular processes affecting inflammation and microbial pathogenesis.
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1438
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Button RW, Luo S, Rubinsztein DC. Autophagic activity in neuronal cell death. Neurosci Bull 2015; 31:382-94. [PMID: 26077705 DOI: 10.1007/s12264-015-1528-y] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 05/11/2015] [Indexed: 12/19/2022] Open
Abstract
As post-mitotic cells with great energy demands, neurons depend upon the homeostatic and waste-recycling functions provided by autophagy. In addition, autophagy also promotes survival during periods of harsh stress and targets aggregate-prone proteins associated with neurodegeneration for degradation. Despite this, autophagy has also been controversially described as a mechanism of programmed cell death. Instances of autophagic cell death are typically associated with elevated numbers of cytoplasmic autophagosomes, which have been assumed to lead to excessive degradation of cellular components. Due to the high activity and reliance on autophagy in neurons, these cells may be particularly susceptible to autophagic death. In this review, we summarize and assess current evidence in support of autophagic cell death in neurons, as well as how the dysregulation of autophagy commonly seen in neurodegeneration can contribute to neuron loss. From here, we discuss potential treatment strategies relevant to such cell-death pathways.
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Affiliation(s)
- Robert W Button
- Peninsula Schools of Medicine and Dentistry, Institute of Translational and Stratified Medicine, University of Plymouth, Research Way, Plymouth, PL6 8BU, UK
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1439
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Wang Y, Huang C, Zhang H, Wu R. Autophagy in glaucoma: Crosstalk with apoptosis and its implications. Brain Res Bull 2015; 117:1-9. [PMID: 26073842 DOI: 10.1016/j.brainresbull.2015.06.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Revised: 05/05/2015] [Accepted: 06/04/2015] [Indexed: 01/07/2023]
Abstract
Glaucoma is characterized by elevated intraocular pressure that causes progressive loss of retinal ganglion cells (RGCs). Autophagy is a lysosomal degradative process that updates the cellular components and plays an important role in cellular homeostasis. Recent studies have shown that autophagy is involved in the pathophysiological process of glaucoma. The role played by autophagy in glaucoma is complex, and conflicting evidence shows that autophagy promotes both RGC survival and death. The understanding of the major pattern of RGC loss and the crosstalk between autophagy and apoptosis remains limited in glaucoma. This review focuses on the relationship between autophagy and glaucoma, particularly on the influence of autophagy on apoptosis in glaucoma. Further research on autophagy in glaucoma may provide a novel understanding of the glaucoma pathology and novel treatment targets for glaucoma in the future.
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Affiliation(s)
- Yao Wang
- Eye Institute and Affiliated Xiamen Eye Center, Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Xiamen, Fujian 361102, China; Department of Ophthalmology, First Hospital of Xi'an, Shaanxi Institute of Ophthalmology, Shaanxi Provincial Key Lab of Ophthalmology, Xi'an, Shaanxi 710002, China
| | - Changquan Huang
- Eye Institute and Affiliated Xiamen Eye Center, Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Xiamen, Fujian 361102, China
| | - Hongbing Zhang
- Department of Ophthalmology, First Hospital of Xi'an, Shaanxi Institute of Ophthalmology, Shaanxi Provincial Key Lab of Ophthalmology, Xi'an, Shaanxi 710002, China
| | - Renyi Wu
- Eye Institute and Affiliated Xiamen Eye Center, Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Xiamen, Fujian 361102, China.
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1440
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Sanjurjo L, Aran G, Roher N, Valledor AF, Sarrias MR. AIM/CD5L: a key protein in the control of immune homeostasis and inflammatory disease. J Leukoc Biol 2015; 98:173-84. [PMID: 26048980 DOI: 10.1189/jlb.3ru0215-074r] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 04/12/2015] [Indexed: 01/16/2023] Open
Abstract
CD5L, a soluble protein belonging to the SRCR superfamily, is expressed mostly by macrophages in lymphoid and inflamed tissues. The expression of this protein is transcriptionally controlled by LXRs, members of the nuclear receptor family that play major roles in lipid homeostasis. Research undertaken over the last decade has uncovered critical roles of CD5L as a PRR of bacterial and fungal components and in the control of key mechanisms in inflammatory responses, with involvement in processes, such as infection, atherosclerosis, and cancer. In this review, we summarize the current knowledge of CD5L, its roles at the intersection between lipid homeostasis and immune response, and its potential use as a diagnostic biomarker in a variety of diseases, such as TB and liver cirrhosis.
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Affiliation(s)
- Lucía Sanjurjo
- *Innate Immunity Group, Health Sciences Research Institute Germans Trias i Pujol, Badalona, Spain; Evolutive Immunology Group, Institute of Biotechnology and Biomedicine, Universitat Autònoma de Barcelona, Barcelona, Spain; Nuclear Receptor Group, Department of Physiology and Immunology, School of Biology, University of Barcelona, Barcelona, Spain; and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, Barcelona, Spain
| | - Gemma Aran
- *Innate Immunity Group, Health Sciences Research Institute Germans Trias i Pujol, Badalona, Spain; Evolutive Immunology Group, Institute of Biotechnology and Biomedicine, Universitat Autònoma de Barcelona, Barcelona, Spain; Nuclear Receptor Group, Department of Physiology and Immunology, School of Biology, University of Barcelona, Barcelona, Spain; and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, Barcelona, Spain
| | - Nerea Roher
- *Innate Immunity Group, Health Sciences Research Institute Germans Trias i Pujol, Badalona, Spain; Evolutive Immunology Group, Institute of Biotechnology and Biomedicine, Universitat Autònoma de Barcelona, Barcelona, Spain; Nuclear Receptor Group, Department of Physiology and Immunology, School of Biology, University of Barcelona, Barcelona, Spain; and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, Barcelona, Spain
| | - Annabel F Valledor
- *Innate Immunity Group, Health Sciences Research Institute Germans Trias i Pujol, Badalona, Spain; Evolutive Immunology Group, Institute of Biotechnology and Biomedicine, Universitat Autònoma de Barcelona, Barcelona, Spain; Nuclear Receptor Group, Department of Physiology and Immunology, School of Biology, University of Barcelona, Barcelona, Spain; and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, Barcelona, Spain
| | - Maria-Rosa Sarrias
- *Innate Immunity Group, Health Sciences Research Institute Germans Trias i Pujol, Badalona, Spain; Evolutive Immunology Group, Institute of Biotechnology and Biomedicine, Universitat Autònoma de Barcelona, Barcelona, Spain; Nuclear Receptor Group, Department of Physiology and Immunology, School of Biology, University of Barcelona, Barcelona, Spain; and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, Barcelona, Spain
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1441
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Abstract
The main function of the heart is to pump blood to the different parts of the organism, a task that is efficiently accomplished through proper electric and metabolic coupling between cardiac cells, ensured by gap junctions (GJ). Cardiomyocytes are the major cell population in the heart, and as cells with low mitotic activity, are highly dependent upon mechanisms of protein degradation. In the heart, both the ubiquitin-proteasome system (UPS) and autophagy participate in the fine-tune regulation of cardiac remodelling and function, either in physiological or pathological conditions. Indeed, besides controlling cardiac signalling pathways, UPS and autophagy have been implicated in the turnover of several myocardial proteins. Degradation of Cx43, the major ventricular GJ protein, has been associated to up-regulation of autophagy at the onset of heart ischemia and ischemia/reperfusion (I/R), which can have profound implications upon cardiac function. In this review, we present recent studies devoted to the involvement of autophagy and UPS in heart homoeostasis, with a particular focus on GJ.
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1442
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Structure of the Atg101-Atg13 complex reveals essential roles of Atg101 in autophagy initiation. Nat Struct Mol Biol 2015; 22:572-80. [PMID: 26030876 DOI: 10.1038/nsmb.3036] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 04/29/2015] [Indexed: 12/18/2022]
Abstract
Atg101 is an essential component of the autophagy-initiating ULK complex in higher eukaryotes, but it is absent from the functionally equivalent Atg1 complex in budding yeast. Here, we report the crystal structure of the fission yeast Atg101-Atg13 complex. Atg101 has a Hop1, Rev7 and Mad2 (HORMA) architecture similar to that of Atg13. Mad2 HORMA has two distinct conformations (O-Mad2 and C-Mad2), and, intriguingly, Atg101 resembles O-Mad2 rather than the C-Mad2-like Atg13. Atg13 HORMA from higher eukaryotes possesses an inherently unstable fold, which is stabilized by Atg101 via interactions analogous to those between O-Mad2 and C-Mad2. Mutational studies revealed that Atg101 is responsible for recruiting downstream factors to the autophagosome-formation site in mammals via a newly identified WF finger. These data define the molecular functions of Atg101, providing a basis for elucidating the molecular mechanisms of mammalian autophagy initiation by the ULK complex.
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1443
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Interference with the Autophagic Process as a Viral Strategy to Escape from the Immune Control: Lesson from Gamma Herpesviruses. J Immunol Res 2015; 2015:546063. [PMID: 26090494 PMCID: PMC4451563 DOI: 10.1155/2015/546063] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 04/13/2015] [Accepted: 04/28/2015] [Indexed: 12/14/2022] Open
Abstract
We summarized the most recent findings on the role of autophagy in antiviral immune response. We described how viruses have developed strategies to subvert the autophagic process. A particular attention has been given to Epstein-Barr and Kaposi's sarcoma associated Herpesvirus, viruses studied for many years in our laboratory. These two viruses belong to γ-Herpesvirus subfamily and are associated with several human cancers. Besides the effects on the immune response, we have described how autophagy subversion by viruses may also concur to the enhancement of their replication and to viral tumorigenesis.
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1444
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Ma B, Liu B, Cao W, Gao C, Qi Z, Ning Y, Chen YG. The Wnt Signaling Antagonist Dapper1 Accelerates Dishevelled2 Degradation via Promoting Its Ubiquitination and Aggregate-induced Autophagy. J Biol Chem 2015; 290:12346-12354. [PMID: 25825496 PMCID: PMC4424364 DOI: 10.1074/jbc.m115.654590] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 03/30/2015] [Indexed: 11/22/2023] Open
Abstract
Autophagy is a regulated process that sequesters and transports cytoplasmic materials such as protein aggregates via autophagosomes to lysosomes for degradation. Dapper1 (Dpr1), an interacting protein of Dishevelled (Dvl), antagonizes Wnt signaling by promoting Dishevelled degradation via lysosomes. However, the mechanism is unclear. Here, we show that Dpr1 promotes the von Hippel-Lindau tumor suppressor (VHL)-mediated ubiquitination of Dvl2 and its autophagic degradation. Knockdown of Dpr1 decreases the interaction between Dvl2 and pVHL, resulting in reduced ubiquitination of Dvl2. Dpr1-mediated autophagic degradation of Dvl2 depends on Dvl2 aggregation. Moreover, the aggregate-prone proteins Dvl2, p62, and the huntingtin mutant Htt103Q promote autophagy in a Dpr1-dependent manner. These protein aggregates enhance the Beclin1-Vps34 interaction and Atg14L puncta formation, indicating that aggregated proteins stimulate autophagy initiation. Ubiquitination is not essential for the aggregate-induced autophagy initiation as inhibition of the ubiquitin-activation E1 enzyme activity did not block the aggregate-induced Atg14L puncta formation. Our findings suggest that Dpr1 promotes the ubiquitination of Dvl2 by pVHL and mediates the protein aggregate-elicited autophagy initiation.
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Affiliation(s)
- Benyu Ma
- From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Bofeng Liu
- From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Weipeng Cao
- From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Chan Gao
- From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhen Qi
- From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yuanheng Ning
- From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ye-Guang Chen
- From the State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
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1445
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Li F, Chung T, Pennington JG, Federico ML, Kaeppler HF, Kaeppler SM, Otegui MS, Vierstra RD. Autophagic recycling plays a central role in maize nitrogen remobilization. THE PLANT CELL 2015; 27:1389-408. [PMID: 25944100 PMCID: PMC4456646 DOI: 10.1105/tpc.15.00158] [Citation(s) in RCA: 155] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 03/19/2015] [Accepted: 04/09/2015] [Indexed: 05/18/2023]
Abstract
Autophagy is a primary route for nutrient recycling in plants by which superfluous or damaged cytoplasmic material and organelles are encapsulated and delivered to the vacuole for breakdown. Central to autophagy is a conjugation pathway that attaches AUTOPHAGY-RELATED8 (ATG8) to phosphatidylethanolamine, which then coats emerging autophagic membranes and helps with cargo recruitment, vesicle enclosure, and subsequent vesicle docking with the tonoplast. A key component in ATG8 function is ATG12, which promotes lipidation upon its attachment to ATG5. Here, we fully defined the maize (Zea mays) ATG system transcriptionally and characterized it genetically through atg12 mutants that block ATG8 modification. atg12 plants have compromised autophagic transport as determined by localization of a YFP-ATG8 reporter and its vacuolar cleavage during nitrogen or fixed-carbon starvation. Phenotypic analyses showed that atg12 plants are phenotypically normal and fertile when grown under nutrient-rich conditions. However, when nitrogen-starved, seedling growth is severely arrested, and as the plants mature, they show enhanced leaf senescence and stunted ear development. Nitrogen partitioning studies revealed that remobilization is impaired in atg12 plants, which significantly decreases seed yield and nitrogen-harvest index. Together, our studies demonstrate that autophagy, while nonessential, becomes critical during nitrogen stress and severely impacts maize productivity under suboptimal field conditions.
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Affiliation(s)
- Faqiang Li
- Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706
| | - Taijoon Chung
- Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706
| | | | - Maria L Federico
- Department of Agronomy, University of Wisconsin, Madison, Wisconsin 53706
| | - Heidi F Kaeppler
- Department of Agronomy, University of Wisconsin, Madison, Wisconsin 53706
| | - Shawn M Kaeppler
- Department of Agronomy, University of Wisconsin, Madison, Wisconsin 53706
| | - Marisa S Otegui
- Department of Botany, University of Wisconsin, Madison, Wisconsin 53706
| | - Richard D Vierstra
- Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706
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1446
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Kelly SP, Bedwell DM. Both the autophagy and proteasomal pathways facilitate the Ubp3p-dependent depletion of a subset of translation and RNA turnover factors during nitrogen starvation in Saccharomyces cerevisiae. RNA (NEW YORK, N.Y.) 2015; 21:898-910. [PMID: 25795416 PMCID: PMC4408797 DOI: 10.1261/rna.045211.114] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 01/05/2015] [Indexed: 05/20/2023]
Abstract
Protein turnover is an important regulatory mechanism that facilitates cellular adaptation to changing environmental conditions. Previous studies have shown that ribosome abundance is reduced during nitrogen starvation by a selective autophagy mechanism termed ribophagy, which is dependent upon the deubiquitinase Ubp3p. In this study, we asked whether the abundance of various translation and RNA turnover factors are reduced following the onset of nitrogen starvation in Saccharomyces cerevisiae. We found distinct differences in the abundance of the proteins tested following nitrogen starvation: (1) The level of some did not change; (2) others were reduced with kinetics similar to ribophagy, and (3) a few proteins were rapidly depleted. Furthermore, different pathways differentially degraded the various proteins upon nitrogen starvation. The translation factors eRF3 and eIF4GI, and the decapping enhancer Pat1p, required an intact autophagy pathway for their depletion. In contrast, the deadenylase subunit Pop2p and the decapping enzyme Dcp2p were rapidly depleted by a proteasome-dependent mechanism. The proteasome-dependent depletion of Dcp2p and Pop2p was also induced by rapamycin, suggesting that the TOR1 pathway influences this pathway. Like ribophagy, depletion of eIF4GI, eRF3, Dcp2p, and Pop2p was dependent upon Ubp3p to varying extents. Together, our results suggest that the autophagy and proteasomal pathways degrade distinct translation and RNA turnover factors in a Ubp3p-dependent manner during nitrogen starvation. While ribophagy is thought to mediate the reutilization of scarce resources during nutrient limitation, our results suggest that the selective degradation of specific proteins could also facilitate a broader reprogramming of the post-transcriptional control of gene expression.
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Affiliation(s)
- Shane P Kelly
- Department of Cell, Developmental and Integrative Biology, Birmingham, Alabama 35294, USA
| | - David M Bedwell
- Department of Cell, Developmental and Integrative Biology, Birmingham, Alabama 35294, USA Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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1447
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Development of fluorescent peptide substrates and assays for the key autophagy-initiating cysteine protease enzyme, ATG4B. Bioorg Med Chem 2015; 23:3237-47. [PMID: 25979376 DOI: 10.1016/j.bmc.2015.04.064] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Revised: 04/14/2015] [Accepted: 04/21/2015] [Indexed: 11/23/2022]
Abstract
An efficient assay for monitoring the activity of the key autophagy-initiating enzyme ATG4B based on a small peptide substrate has been developed. A number of putative small fluorogenic peptide substrates were prepared and evaluated and optimized compounds showed reasonable rates of cleavage but required high enzyme concentrations which limited their value. A modified peptide substrate incorporating a less sterically demanding self-immolative element was designed and synthesized and was shown to have enhanced properties useful for evaluating inhibitors of ATG4B. Substrate cleavage was readily monitored and was linear for up to 4h but enzyme concentrations of about ten-fold higher were required compared to assays using protein substrate LC3 or analogs thereof (such as FRET-LC3). Several known inhibitors of ATG4B were evaluated using the small peptide substrate and gave IC50 values 3-7 fold higher than previously obtained values using the FRET-LC3 substrate.
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1448
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Kim TM, Baek JH, Kim JH, Oh MS, Kim J. Development of in vitro PIK3C3/VPS34 complex protein assay for autophagy-specific inhibitor screening. Anal Biochem 2015; 480:21-7. [PMID: 25862085 DOI: 10.1016/j.ab.2015.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 04/02/2015] [Accepted: 04/03/2015] [Indexed: 12/13/2022]
Abstract
Autophagy is an important catabolic program to respond to a variety of cellular stresses by forming a double membrane vesicle, autophagosome. Autophagy plays key roles in various cellular functions. Accordingly, dysregulation of autophagy is closely associated with diseases such as diabetes, neurodegenerative diseases, cardiomyopathy, and cancer. In this sense, autophagy is emerging as an important therapeutic target for disease control. Among the autophagy machineries, PIK3C3/VPS34 complex functions as an autophagy-triggering kinase to recruit the subsequent autophagy protein machineries on the phagophore membrane. Accumulating evidence showing that inhibition of PIK3C3/VPS34 complex successfully inhibits autophagy makes the complex an attractive target for developing autophagy inhibitors. However, one concern about PIK3C3/VPS34 complex is that many different PIK3C3/VPS34 complexes have distinct cellular functions. In this study, we have developed an in vitro PIK3C3/VPS34 complex monitoring assay for autophagy inhibitor screening in a high-throughput assay format instead of targeting the catalytic activity of the PIK3C3/VPS34 complex, which shuts down all PIK3C3/VPS34 complexes. We performed in vitro reconstitution of an essential autophagy-promoting PIK3C3/VPS34 complex, Vps34-Beclin1-ATG14L complex, in a microwell plate (96-well format) and successfully monitored the complex formation in many different conditions. This PIK3C3/VPS34 complex protein assay would provide a reliable tool for the screening of autophagy-specific inhibitors.
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Affiliation(s)
- Tae-Mi Kim
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea
| | - Jong-Hyuk Baek
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea
| | - Jeong Hee Kim
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Department of Oral Biochemistry and Molecular Biology, School of Dentistry, Kyung Hee University, Seoul 130-701, Republic of Korea
| | - Myung Sook Oh
- Department of Life and Nanopharmaceutical Science, Kyung Hee University, Seoul 130-701, Republic of Korea; Department of Oriental Pharmaceutical Science, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea.
| | - Joungmok Kim
- Department of Oral Biochemistry and Molecular Biology, School of Dentistry, Kyung Hee University, Seoul 130-701, Republic of Korea.
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1449
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Gayral M, Bakan B, Dalgalarrondo M, Elmorjani K, Delluc C, Brunet S, Linossier L, Morel MH, Marion D. Lipid partitioning in maize (Zea mays L.) endosperm highlights relationships among starch lipids, amylose, and vitreousness. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:3551-3558. [PMID: 25794198 DOI: 10.1021/acs.jafc.5b00293] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Content and composition of maize endosperm lipids and their partition in the floury and vitreous regions were determined for a set of inbred lines. Neutral lipids, i.e., triglycerides and free fatty acids, accounted for more than 80% of endosperm lipids and are almost 2 times higher in the floury than in the vitreous regions. The composition of endosperm lipids, including their fatty acid unsaturation levels, as well as their distribution may be related to metabolic specificities of the floury and vitreous regions in carbon and nitrogen storage and to the management of stress responses during endosperm cell development. Remarkably, the highest contents of starch lipids were observed systematically within the vitreous endosperm. These high amounts of starch lipids were mainly due to lysophosphatidylcholine and were tightly linked to the highest amylose content. Consequently, the formation of amylose-lysophosphatidylcholine complexes has to be considered as an outstanding mechanism affecting endosperm vitreousness.
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Affiliation(s)
- Mathieu Gayral
- †INRA, Biopolymers, Interactions, Assemblies Research Unit, La Géraudière 44316 Nantes Cedex 3, France
| | - Bénédicte Bakan
- †INRA, Biopolymers, Interactions, Assemblies Research Unit, La Géraudière 44316 Nantes Cedex 3, France
| | - Michele Dalgalarrondo
- †INRA, Biopolymers, Interactions, Assemblies Research Unit, La Géraudière 44316 Nantes Cedex 3, France
| | - Khalil Elmorjani
- †INRA, Biopolymers, Interactions, Assemblies Research Unit, La Géraudière 44316 Nantes Cedex 3, France
| | | | - Sylvie Brunet
- §Limagrain Cereal Ingredients ZAC Les Portes de Riom, Avenue George Gershwin 63200 RIOM Cedex, France
| | - Laurent Linossier
- §Limagrain Cereal Ingredients ZAC Les Portes de Riom, Avenue George Gershwin 63200 RIOM Cedex, France
| | - Marie-Hélène Morel
- ∥INRA, Agropolymers Engineering and Emerging Technologies, 2 place Pierre Viala, 34060 Montpellier Cedex 02, France
| | - Didier Marion
- †INRA, Biopolymers, Interactions, Assemblies Research Unit, La Géraudière 44316 Nantes Cedex 3, France
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1450
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Tan X, Thapa N, Sun Y, Anderson RA. A kinase-independent role for EGF receptor in autophagy initiation. Cell 2015; 160:145-60. [PMID: 25594178 DOI: 10.1016/j.cell.2014.12.006] [Citation(s) in RCA: 179] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/21/2014] [Accepted: 11/19/2014] [Indexed: 12/30/2022]
Abstract
The epidermal growth factor receptor (EGFR) is upregulated in numerous human cancers. Inhibition of EGFR signaling induces autophagy in tumor cells. Here, we report an unanticipated role for the inactive EGFR in autophagy initiation. Inactive EGFR interacts with the oncoprotein LAPTM4B that is required for the endosomal accumulation of EGFR upon serum starvation. Inactive EGFR and LAPTM4B stabilize each other at endosomes and recruit the exocyst subcomplex containing Sec5. We show that inactive EGFR, LAPTM4B, and the Sec5 subcomplex are required for basal and starvation-induced autophagy. LAPTM4B and Sec5 promote EGFR association with the autophagy inhibitor Rubicon, which in turn disassociates Beclin 1 from Rubicon to initiate autophagy. Thus, the oncoprotein LAPTM4B facilitates the role of inactive EGFR in autophagy initiation. This pathway is positioned to control tumor metabolism and promote tumor cell survival upon serum deprivation or metabolic stress.
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Affiliation(s)
- Xiaojun Tan
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Narendra Thapa
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Yue Sun
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Richard A Anderson
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA.
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