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Mizutani T, Furusawa K, Haga H, Kawabata K. Heterogeneous filament network formation by myosin light chain isoforms effects on contractile energy output of single cardiomyocytes derived from human induced pluripotent stem cells. Regen Ther 2016; 3:90-96. [PMID: 31245478 PMCID: PMC6581838 DOI: 10.1016/j.reth.2016.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 02/19/2016] [Accepted: 02/22/2016] [Indexed: 11/23/2022] Open
Abstract
Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) are expected to play an important role in heart therapies, in which hiPSC-CMs should generate sufficient contractile force to pump blood. However, recent studies have shown that the contractility of myocardial mimics composed of hiPSC-CMs is lower than that of adult human myocardium. To examine the mechanism by which contractile force output of hiPSC-CMs is weakened, we measured the contractile force of single hiPSC-CMs and observed the fibrous distribution of myosin II regulatory light chain (MRLC) of cardiac (contributes to beating) and non-cardiac (does not contribute to beating) isoforms. Single hiPSC-CMs were cultured on an extracellular matrix gel, and the contractile force and strain energy exerted on the gel were measured. Strain energy was not uniform between cells and ranged from 0.2 to 5.8 pJ. The combination of contractile force measurement and immunofluorescent microscopy for MRLC isoforms showed that cells with higher strain energy expressed the weakened non-cardiac myosin II fibers compared to those of cells with lower strain energy. Observation of cardiac and non-cardiac MRLC showed that the MRLC isoforms formed heterogeneous filament networks. These results suggest that strain energy output from single hiPSC-CMs depends both cardiac and non-cardiac myosin fibers, which prevent deformation of the cell body. The contractile force output of single hiPSC-CMs is uniform between cells. Cells that output high strain energy generally form weak non-cardiac myosin II fibers. Cardiac myosin II and non-cardiac myosin II construct heterogeneous fiber networks.
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Zhang J, Ng S, Wang J, Zhou J, Tan SH, Yang N, Lin Q, Xia D, Shen HM. Histone deacetylase inhibitors induce autophagy through FOXO1-dependent pathways. Autophagy 2016; 11:629-42. [PMID: 25919885 DOI: 10.1080/15548627.2015.1023981] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Autophagy is a catabolic process in response to starvation or other stress conditions to sustain cellular homeostasis. At present, histone deacetylase inhibitors (HDACIs) are known to induce autophagy in cells through inhibition of mechanistic target of rapamycin (MTOR) pathway. FOXO1, an important transcription factor regulated by AKT, is also known to play a role in autophagy induction. At present, the role of FOXO1 in the HDACIs-induced autophagy has not been reported. In this study, we first observed that HDACIs increased the expression of FOXO1 at the mRNA and protein level. Second, we found that FOXO1 transcriptional activity was enhanced by HDACIs, as evidenced by increased FOXO1 nuclear accumulation and transcriptional activity. Third, suppression of FOXO1 function by siRNA knockdown or by a chemical inhibitor markedly blocked HDACIs-induced autophagy. Moreover, we found that FOXO1-mediated autophagy is achieved via its transcriptional activation, leading to a dual effect on autophagy induction: (i) enhanced expression of autophagy-related (ATG) genes, and (ii) suppression of MTOR via transcription of the SESN3 (sestrin 3) gene. Finally, we found that inhibition of autophagy markedly enhanced HDACIs-mediated cell death, indicating that autophagy serves as an important cell survival mechanism. Taken together, our studies reveal a novel function of FOXO1 in HDACIs-mediated autophagy in human cancer cells and thus support the development of a novel therapeutic strategy by combining HDACIs and autophagy inhibitors in cancer therapy.
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Key Words
- ATG, autophagy-related
- BAF, bafilomycin A1
- CQ, chloroquine
- FOXO, forkhead box O
- FOXO1
- GFP, green fluorescent protein
- MAP1LC3/LC3, microtubule-associated protein 1 light chain 3
- MEF, mouse embryonic fibroblast
- MTOR
- MTOR, mechanistic target of rapamycin
- PI3K, phosphoinositide 3-kinase
- SAHA, suberoylanilide hydroxamic acid
- TSA, trichostatin A
- TSC, tuberous sclerosis
- autophagy
- cancer
- cell death
- histone deacetylase inhibitors
- siRNA, short interfering RNA
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Guo S, Liang Y, Murphy SF, Huang A, Shen H, Kelly DF, Sobrado P, Sheng Z. A rapid and high content assay that measures cyto-ID-stained autophagic compartments and estimates autophagy flux with potential clinical applications. Autophagy 2016; 11:560-72. [PMID: 25714620 PMCID: PMC4502761 DOI: 10.1080/15548627.2015.1017181] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The lack of a rapid and quantitative autophagy assay has substantially hindered the development and implementation of autophagy-targeting therapies for a variety of human diseases. To address this critical issue, we developed a novel autophagy assay using the newly developed Cyto-ID fluorescence dye. We first verified that the Cyto-ID dye specifically labels autophagic compartments with minimal staining of lysosomes and endosomes. We then developed a new Cyto-ID fluorescence spectrophotometric assay that makes it possible to estimate autophagy flux based on measurements of the Cyto-ID-stained autophagic compartments. By comparing to traditional autophagy approaches, we found that this assay yielded a more sensitive, yet less variable, quantification of the stained autophagic compartments and the estimate of autophagy flux. Furthermore, we tested the potential application of this autophagy assay in high throughput research by integrating it into an RNA interference (RNAi) screen and a small molecule screen. The RNAi screen revealed WNK2 and MAP3K6 as autophagy-modulating genes, both of which inhibited the MTOR pathway. Similarly, the small molecule screen identified sanguinarine and actinomycin D as potent autophagy inducers in leukemic cells. Moreover, we successfully detected autophagy responses to kinase inhibitors and chloroquine in normal or leukemic mice using this assay. Collectively, this new Cyto-ID fluorescence spectrophotometric assay provides a rapid, reliable quantification of autophagic compartments and estimation of autophagy flux with potential applications in developing autophagy-related therapies and as a test to monitor autophagy responses in patients being treated with autophagy-modulating drugs.
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Key Words
- 3-MA, 3-methyladenine
- Cyto-ID
- FBS, fetal bovine serum
- GFP, green fluorescent protein
- LAMP1, lysosomal-associated membrane protein 1
- MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 beta
- MAP3K6, mitogen-activated protein kinase kinase kinase 6
- MDC, monodansylcadaverine
- MTOR, mechanistic target of rapamycin
- NS, nonsilencing
- RAB5A, member RAS oncogene family
- RNA interference screen
- RNAi, RNA interference
- SQSTM1, sequestosome 1
- WNK2, WNK lysine deficient protein kinase 2
- autophagy
- autophagy flux
- autophagy response
- mRFP, monomeric red fluorescent protein
- shRNA, short-hairpin RNA
- small molecule screen
- spectrophotometric assay
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Choi SH, Gonen A, Diehl CJ, Kim J, Almazan F, Witztum JL, Miller YI. SYK regulates macrophage MHC-II expression via activation of autophagy in response to oxidized LDL. Autophagy 2016; 11:785-95. [PMID: 25946330 DOI: 10.1080/15548627.2015.1037061] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Adaptive immunity, which plays an important role in the development of atherosclerosis, is mediated by major histocompatibility complex (MHC)-dependent antigen presentation. In atherosclerotic lesions, macrophages constitute an important class of antigen-presenting cells that activate adaptive immune responses to oxidized low-density lipoprotein (OxLDL). It has been reported that autophagy regulates adaptive immune responses by enhancing antigen presentation to MHC class II (MHC-II). In a previous study, we have demonstrated that SYK (spleen tyrosine kinase) regulates generation of reactive oxygen species (ROS) and activation of MAPK8/JNK1 in macrophages. Because ROS and MAPK8 are known to regulate autophagy, in this study we investigated the role of SYK in autophagy, MHC-II expression and adaptive immune response to OxLDL. We demonstrate that OxLDL induces autophagosome formation, MHC-II expression, and phosphorylation of SYK in macrophages. Gene knockout and pharmacological inhibitors of NOX2 and MAPK8 reduced OxLDL-induced autophagy. Using bone marrow-derived macrophages isolated from wild-type and myeloid-specific SYK knockout mice, we demonstrate that SYK regulates OxLDL-induced ROS generation, MAPK8 activation, BECN1-BCL2 dissociation, autophagosome formation and presentation of OxLDL-derived antigens to CD4(+) T cells. ldlr(-/-) syk(-/-) mice fed a high-fat diet produced lower levels of IgG to malondialdehyde (MDA)-LDL, malondialdehyde-acetaldehyde (MAA)-LDL, and OxLDL compared to ldlr(-/-) mice. These results provide new insights into the mechanisms by which SYK regulates MHC-II expression via autophagy in macrophages and may contribute to regulation of adaptive immune responses in atherosclerosis.
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Key Words
- 3MA, 3-methyladenine
- APCs, antigen-presenting cells
- BCR, B cell receptor
- BMDM, bone marrow-derived macrophage
- Baf, bafilomycin A1
- DPI, diphenyleneiodonium
- FCGR, Fc fragment of IgG
- GFP, green fluorescent protein
- HFD, high-fat diet
- IL2, interleukin 2
- ITAM, immunoreceptor tyrosine-based activation motif
- IgG, immunoglobulin G
- IgM, immunoglobulin M
- LPS, lipopolysaccharide
- MAA-LDL, malondialdehyde-acetaldehyde modified low density lipoprotein
- MAP1LC3/LC3, microtubule-associated protein 1 light chain 3
- MAPK, mitogen-activated protein kinase
- MDA-LDL, malondialdehyde modified low density lipoprotein
- MHC-II
- MHC-II, major histocompatibility complex class II
- NOX, NAPDH oxidase
- OSE, oxidation specific epitopes
- OxLDL
- OxLDL, oxidized low density lipoprotein
- PBS, phosphate-buffered saline
- PIC, piceatannol
- ROS
- ROS, reactive oxygen species
- SYK
- SYK, spleen tyrosine kinase
- TCR, T cell receptor
- TLR4, toll-like receptor 4
- TNF, tumor necrosis factor
- autophagy
- low affinity, receptor
- mmLDL, minimally modified low density lipoprotein
- oxidation-specific antibodies
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Abstract
West Nile virus (WNV) is a neurotropic mosquito-borne flavivirus responsible for recurrent outbreaks of meningitis and encephalitis. Several studies analyzing the interactions of this pathogen with the autophagic pathway have reported opposite results with evidence for and against the upregulation of autophagy in infected cells. In this regard, we have recently reported that minimal genetic changes (single amino acid substitutions) in nonstructural proteins of WNV can modify the ability of the virus to induce autophagic features such as LC3 modification and aggregation in infected cells. We think that these results could help explain some of the previously reported discrepancies. These findings could also aid in deciphering the interactions of this pathogen with the autophagic pathway at the molecular level aimed to develop feasible antiviral strategies to combat this pathogen, and other related flaviviruses.
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Abstract
BECN1/Beclin 1 is regarded as a critical component in the class III phosphatidylinositol 3-kinase (PtdIns3K) complex to trigger autophagy in mammalian cells. Despite its significant role in a number of cellular and physiological processes, the exact function of BECN1 in autophagy remains controversial. Here we created a BECN1 knockout human cell line using the TALEN technique. Surprisingly, the complete loss of BECN1 had little effect on LC3 (MAP1LC3B/LC3B) lipidation, and LC3B puncta resembling autophagosomes by fluorescence microscopy were still evident albeit significantly smaller than those in the wild-type cells. Electron microscopy (EM) analysis revealed that BECN1 deficiency led to malformed autophagosome-like structures containing multiple layers of membranes under amino acid starvation. We further confirmed that the PtdIns3K complex activity and autophagy flux were disrupted in BECN1−/− cells. Our results demonstrate the essential role of BECN1 in the functional formation of autophagosomes, but not in LC3B lipidation.
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Key Words
- ATG, autophagy related
- BCL2L1/Bcl-xL, BCL2-like 1
- BECN1
- BECN1, Beclin 1, autophagy related
- BECN1P1/BECN2, Beclin 1, autophagy related, pseudogene 1
- BafA1, bafilomycin A1
- EM, electron microscopy
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- GFP, green fluorescent protein
- KO, knockout
- LC3
- MAP1LC3-I/LC3-I, soluble, proteolytically processed microtubule-associated protein 1 light chain 3
- MAP1LC3-II/LC3-II, proteolytically processed and lipid-modified microtubule-associated protein 1 light chain 3
- MAP1LC3/LC3, microtubule-associated protein 1 light chain 3
- MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 β
- PIK3C3/VPS34, phosphatidylinositol 3-kinase, catalytic subunit type 3
- PIK3R4/VPS15, phosphoinositide-3-kinase, regulatory subunit 4
- PtdIns3K
- PtdIns3K, phosphatidylinositol 3-kinase
- SQSTM1/p62, sequestosome 1
- TALEN, transcription activator-like effector nuclease
- TUBB, tubulin, β class I
- UVRAG, UV radiation resistance associated
- ZFYVE1/DFCP1, zinc finger, FYVE domain containing 1.
- autophagosome
- autophagy
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Romano V, Quadri Z, Baralle FE, Buratti E. The structural integrity of TDP-43 N-terminus is required for efficient aggregate entrapment and consequent loss of protein function. Prion 2016; 9:1-9. [PMID: 25635624 DOI: 10.1080/19336896.2015.1011885] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nuclear factor TDP-43 has been shown to play a key role in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia, where TDP-43 aggregates accumulate in patient's affected neurons and this event can cause neuronal dysfunction. A major focus of today's research is to discover the critical factors that lead to TDP-43 aggregation and the consequences for neuronal metabolism. From a structural point of view, several lines of evidence point toward TDP-43 C-terminus as a key domain able to mediate this process. Regarding this region, we have recently described a novel cellular TDP-43 aggregation model based on 12 tandem repetitions of its 339-366 Q/N rich prion-like domain. In addition, we have shown and confirmed that a minimal TDP-43 construct constituted by the N and C-terminal regions, but lacking both RRM domains, induce aggregation of endogenous TDP-43 and leads to its total loss of function as seen by changes in the alternative splicing of endogenous genes. In this work, we further characterize this model and show the importance of the N-terminus structure in the loss of function process. In addition, from a biochemical point of view we report that, as shown in a previous version of this model (GFP 12 × Q/N), the endogenous TDP-43 trapped in the aggregates undergoes the 2 most important post-translational modifications seen in pathological TDP-43 inclusions: ubiquitination and hyperphosphorylation.
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Koenig U, Fobker M, Lengauer B, Brandstetter M, Resch GP, Gröger M, Plenz G, Pammer J, Barresi C, Hartmann C, Rossiter H. Autophagy facilitates secretion and protects against degeneration of the Harderian gland. Autophagy 2016; 11:298-313. [PMID: 25484081 PMCID: PMC4502725 DOI: 10.4161/15548627.2014.978221] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The epithelial derived Harderian gland consists of 2 types of secretory cells. The more numerous type A cells are responsible for the secretion of lipid droplets, while type B cells produce dark granules of multilamellar bodies. The process of autophagy is constitutively active in the Harderian gland, as confirmed by our analysis of LC3 processing in GFP-LC3 transgenic mice. This process is compromised by epithelial deletion of Atg7. Morphologically, the Atg7 mutant glands are hypotrophic and degenerated, with highly vacuolated cells and pyknotic nuclei. The mutant glands accumulate lipid droplets coated with PLIN2 (perilipin 2) and contain deposits of cholesterol, ubiquitinated proteins, SQSTM1/p62 (sequestosome 1) positive aggregates and other metabolic products such as porphyrin. Immunofluorescence stainings show that distinct cells strongly aggregate both proteins and lipids. Electron microscopy of the Harderian glands reveals that its organized structure is compromised, and the presence of large intracellular lipid droplets and heterologous aggregates. We attribute the occurrence of large vacuoles to a malfunction in the formation of multilamellar bodies found in the less abundant type B Harderian gland cells. This defect causes the formation of large tertiary lysosomes of heterologous content and is accompanied by the generation of tight lamellar stacks of endoplasmic reticulum in a pseudo-crystalline form. To test the hypothesis that lipid and protein accumulation is the cause for the degeneration in autophagy-deficient Harderian glands, epithelial cells were treated with a combination of the proteasome inhibitor and free fatty acids, to induce aggregation of misfolded proteins and lipid accumulation, respectively. The results show that lipid accumulation indeed enhanced the toxicity of misfolded proteins and that this was even more pronounced in autophagy-deficient cells. Thus, we conclude autophagy controls protein and lipid catabolism and anabolism to facilitate bulk production of secretory vesicles of the Harderian gland.
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Key Words
- Atg12, autophagy related 12
- Atg7, autophagy related 7
- BCA, bicinchoninic acid assay
- BODIPY, boron-dipyrromethene fluorescent dye
- BSA, bovine serum albumin
- Cre, Cre recombinase
- DMSO, dimethyl sulfoxide
- ELISA, enzyme-linked immunosorbent assay
- ER, edoplasmic reticulum
- FC, free cholesterol
- GFP, green fluorescent protein
- HaGl, Harderian gland
- Harderian gland
- KLICK, keratosis lineariz with ichthyosis congenita and sclerosing keratoderma
- KRT14, Keratin 14
- LD, Lipid drops
- LSM, laser scanning microscope
- MAP1LC3A/B (LC3), microtubule-associated protein 1 light chain 3 α/β
- MG132
- MG312, synthetic peptide Z-Leu-Leu-Leu-al
- ORO, oil red O
- PARP, poly (ADP-ribose) polymerase
- PCR, polymerase chain reaction
- PLIN2, perilipin 2
- RFU, relative fluorecent units
- SQSTM1, sequestosome 1/p62
- SQSTM1/p62
- TBS-T, Tris buffered saline with Tween 20
- TLC, thin layer chromatography
- UV, ultraviolet
- aggregates
- aggresome
- autophagy
- cholesterol
- degenerative diseases
- f, floxed
- keratinocytes
- lipotoxicity
- lysosome
- multilamellar bodies
- palmitate
- perilipin 2/adipophilin
- proteasome inhibitor
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Liu K, Zhao E, Ilyas G, Lalazar G, Lin Y, Haseeb M, Tanaka KE, Czaja MJ. Impaired macrophage autophagy increases the immune response in obese mice by promoting proinflammatory macrophage polarization. Autophagy 2016; 11:271-84. [PMID: 25650776 DOI: 10.1080/15548627.2015.1009787] [Citation(s) in RCA: 341] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Recent evidence that excessive lipid accumulation can decrease cellular levels of autophagy and that autophagy regulates immune responsiveness suggested that impaired macrophage autophagy may promote the increased innate immune activation that underlies obesity. Primary bone marrow-derived macrophages (BMDM) and peritoneal macrophages from high-fat diet (HFD)-fed mice had decreased levels of autophagic flux indicating a generalized impairment of macrophage autophagy in obese mice. To assess the effects of decreased macrophage autophagy on inflammation, mice with a Lyz2-Cre-mediated knockout of Atg5 in macrophages were fed a HFD and treated with low-dose lipopolysaccharide (LPS). Knockout mice developed systemic and hepatic inflammation with HFD feeding and LPS. This effect was liver specific as knockout mice did not have increased adipose tissue inflammation. The mechanism by which the loss of autophagy promoted inflammation was through the regulation of macrophage polarization. BMDM and Kupffer cells from knockout mice exhibited abnormalities in polarization with both increased proinflammatory M1 and decreased anti-inflammatory M2 polarization as determined by measures of genes and proteins. The heightened hepatic inflammatory response in HFD-fed, LPS-treated knockout mice led to liver injury without affecting steatosis. These findings demonstrate that autophagy has a critical regulatory function in macrophage polarization that downregulates inflammation. Defects in macrophage autophagy may underlie inflammatory disease states such as the decrease in macrophage autophagy with obesity that leads to hepatic inflammation and the progression to liver injury.
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Key Words
- ARG1, arginase 1
- BMDM, bone marrow-derived macrophages
- CCL, chemokine (C-C motif) ligand
- CD, chow diet
- CHIL3/CHI3L3, chitinase-like 3
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- GFP, green fluorescent protein
- GPT, glutamic pyruvic transaminase, soluble
- HFD, high-fat diet
- IFNG, interferon gamma
- IL, interleukin
- Kupffer cells
- LPS, lipopolysaccharide
- MAP1LC3/LC3B, microtubule-associated protein 1 light chain 3 β
- MAPK, mitogen-activated protein kinase
- MGL2, macrophage galactose N-acetyl-galactosamine specific lectin 2
- NOS2, nitric oxide synthase 2, inducible
- PBS, phosphate-buffered saline
- PTGS2, prostaglandin-endoperoxide synthase 2
- RETNLA, resistin like α;
- STAT, signal transducer and activator of transcription
- TNF, tumor necrosis factor
- TUNEL, terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick end-labeling
- WAT, white adipose tissue
- autophagy
- innate immunity
- lipopolysaccharide
- macrophage
- obesity
- polarization
- qRT-PCR, quantitative real-time PCR
- steatohepatitis
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Chen JH, Zhang P, Chen WD, Li DD, Wu XQ, Deng R, Jiao L, Li X, Ji J, Feng GK, Zeng YX, Jiang JW, Zhu XF. ATM-mediated PTEN phosphorylation promotes PTEN nuclear translocation and autophagy in response to DNA-damaging agents in cancer cells. Autophagy 2016; 11:239-52. [PMID: 25701194 DOI: 10.1080/15548627.2015.1009767] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
PTEN (phosphatase and tensin homolog), a tumor suppressor frequently mutated in human cancer, has various cytoplasmic and nuclear functions. PTEN translocates to the nucleus from the cytoplasm in response to oxidative stress. However, the mechanism and function of the translocation are not completely understood. In this study, topotecan (TPT), a topoisomerase I inhibitor, and cisplatin (CDDP) were employed to induce DNA damage. The results indicate that TPT or CDDP activates ATM (ATM serine/threonine kinase), which phosphorylates PTEN at serine 113 and further regulates PTEN nuclear translocation in A549 and HeLa cells. After nuclear translocation, PTEN induces autophagy, in association with the activation of the p-JUN-SESN2/AMPK pathway, in response to TPT. These results identify PTEN phosphorylation by ATM as essential for PTEN nuclear translocation and the subsequent induction of autophagy in response to DNA damage.
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Key Words
- AKT/PKB, v-akt murine thymoma viral oncogene homolog
- AMPK, protein kinase, AMP-activated
- ATG, autophagy-related
- ATM
- ATM, ATM serine/threonine kinase
- Baf.A1, bafilomycin A1
- CASP3, caspase 3, apoptosis-related cysteine peptidase
- CCND1, cyclin D1
- CDDP, cisplatin
- CENPC/CENP-C, centromere protein C
- CITED1/p300/CBP, Cbp/p300-interacting transactivator, with Glu/Asp-rich C-terminal domain, 1
- CSNK2/CK2, casein kinase 2
- DNA damage
- DSBs, DNA double-strand breaks
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- GFP, green fluorescent protein
- GLTSCR2/PICT-1, glioma tumor suppressor candidate region gene 2
- GSK3B, glycogen synthase kinase 3 β
- GST, glutathione S-transferase
- H2A histone family
- H2AFX
- JUN
- MAP1LC3/LC3, microtubule-associated protein 1 light chain 3
- MTORC1, mechanistic target of rapamycin complex 1
- MVP, major vault protein
- NC, normal control
- NEDD4, neural precursor cell expressed, developmentally down-regulated 4, E3 ubiquitin protein ligase
- PAGE, polyacrylamide gel electrophoresis
- PARP, poly (ADP-ribose) polymerase 1
- PI3K, phosphoinositide 3-kinase
- PMSF, phenylmethanesulfonyl fluoride
- PPase, protein phosphatase
- PTEN
- PTEN, phosphatase and tensin homolog
- PtdIns(3, 4, 5)P3, phosphatidylinositol (3, 4, 5)-trisphosphate
- RAD51, RAD51 recombinase
- RPS6KB/p70S6K
- SDS, sodium dodecyl sulfate
- SESN2, sestrin 2
- SQSTM1/p62, sequestosome 1
- TP53, tumor protein p53
- TPT, topotecan
- TUBA4A, tubulin, α, 4a
- WT, wild type
- YFP, yellow fluorescent protein
- autophagy
- jun proto-oncogene
- member X
- ribosomal protein S6 kinase, 70kDa
- siRNA, small interfering RNA
- topotecan
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He J, Yu JJ, Xu Q, Wang L, Zheng JZ, Liu LZ, Jiang BH. Downregulation of ATG14 by EGR1-MIR152 sensitizes ovarian cancer cells to cisplatin-induced apoptosis by inhibiting cyto-protective autophagy. Autophagy 2016; 11:373-84. [PMID: 25650716 DOI: 10.1080/15548627.2015.1009781] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Cisplatin is commonly used in ovarian cancer treatment by inducing apoptosis in cancer cells as a result of lethal DNA damage. However, the intrinsic and acquired resistance to cisplatin in cancer cells remains a big challenge for improving overall survival. The cyto-protective functions of autophagy in cancer cells have been suggested as a potential mechanism for chemoresistance. Here, we reported MIR152 as a new autophagy-regulating miRNA that plays a role in cisplatin-resistance. We showed that MIR152 expression was dramatically downregulated in the cisplatin-resistant cell lines A2780/CP70, SKOV3/DDP compared with their respective parental cells, and in ovarian cancer tissues associated with cisplatin-resistance. Overexpression of MIR152 sensitized cisplatin-resistant ovarian cancer cells by reducing cisplatin-induced autophagy, enhancing cisplatin-induced apoptosis and inhibition of cell proliferation. A mouse subcutaneous xenograft tumor model using A2780/CP70 cells with overexpressing MIR152 was established and displayed decreased tumor growth in response to cisplatin. We also identified that ATG14 is a functional target of MIR152 in regulating autophagy inhibition. Furthermore, we found that EGR1 (early growth response 1) regulated the MIR152 gene at the transcriptional level. Ectopic expression of EGR1 enhanced efficacy of chemotherapy in A2780/CP70 cells. More importantly, these findings were relevant to clinical cases. Both EGR1 and MIR152 expression levels were significantly lower in ovarian cancer tissues with high levels of ERCC1 (excision repair cross-complementation group 1), a marker for cisplatin-resistance. Collectively, these data provide insights into novel mechanisms for acquired cisplatin-resistance. Activation of EGR1 and MIR152 may be a useful therapeutic strategy to overcome cisplatin-resistance by preventing cyto-protective autophagy in ovarian cancer.
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Key Words
- ANXA5, annexin A5
- ATG14
- ATG14, autophagy-related 14
- CSF1, colony stimulating factor 1 (macrophage)
- EGR1
- EGR1, early growth response 1
- ERCC1
- ERCC1, excision repair cross-complementation group 1
- FOXO, forkhead box O
- GFP, green fluorescent protein
- MAPILC3/LC3, microtubule-associated protein 1 light chain 3
- MIR152
- MTOR, mechanistic target of rapamycin
- PI, propidium iodide
- RPS6KB1, ribosomal protein S6 kinase, 70kDa, polypeptide 1
- SQSTM1, sequestosome 1
- autophagy
- cisplatin-resistance
- ovarian cancer
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Patil P, Uechi T, Kenmochi N. Incomplete splicing of neutrophil-specific genes affects neutrophil development in a zebrafish model of poikiloderma with neutropenia. RNA Biol 2016; 12:426-34. [PMID: 25849198 DOI: 10.1080/15476286.2015.1017240] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Poikiloderma with neutropenia (PN) is a rare inherited disorder characterized by poikiloderma, facial dysmorphism, pachyonychia, short stature and neutropenia. The molecular testing of PN patients has identified mutations in the C16orf57 gene, which encodes a protein referred to as USB1 (U Six Biogenesis 1). In this study, we developed a zebrafish model of PN by the microinjection of morpholino antisense oligos to suppress usb1 gene function. Severe morphological defects, including a bent tail, thin yolk extension and reduced body length, were predominant in the Usb1-suppressed embryos (morphants). We also observed significantly decreased number of neutrophils in the morphants by Sudan Black staining. Interestingly, the splicing of genes involved in neutrophil differentiation and development, such as mpx, ncf1, ela3l and npsn, was aberrant in the morphants. However, the splicing of haematopoietic precursors and erythroid-specific genes was unaltered. Importantly, the neutrophil defects were almost completely rescued by co-injection of ela3l mRNA, the most markedly affected gene in the morphants. Our study demonstrated a possible role of USB1 in modulating the tissue-specific gene splicing that eventually leads to the impaired development of neutrophils. This zebrafish model could serve as a valuable tool to investigate the causative role of USB1 in PN pathogenesis.
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Daemen S, van Zandvoort MAMJ, Parekh SH, Hesselink MKC. Microscopy tools for the investigation of intracellular lipid storage and dynamics. Mol Metab 2015; 5:153-163. [PMID: 26977387 PMCID: PMC4770264 DOI: 10.1016/j.molmet.2015.12.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 12/19/2015] [Accepted: 12/27/2015] [Indexed: 12/01/2022] Open
Abstract
Background Excess storage of lipids in ectopic tissues, such as skeletal muscle, liver, and heart, seems to associate closely with metabolic abnormalities and cardiac disease. Intracellular lipid storage occurs in lipid droplets, which have gained attention as active organelles in cellular metabolism. Recent developments in high-resolution microscopy and microscopic spectroscopy have opened up new avenues to examine the physiology and biochemistry of intracellular lipids. Scope of review The aim of this review is to give an overview of recent technical advances in microscopy, and its application for the visualization, identification, and quantification of intracellular lipids, with special focus to lipid droplets. In addition, we attempt to summarize the probes currently available for the visualization of lipids. Major conclusions The continuous development of lipid probes in combination with the rapid development of microscopic techniques can provide new insights in the role and dynamics of intracellular lipids. Moreover, in situ identification of intracellular lipids is now possible and promises to add a new dimensionality to analysis of lipid biochemistry, and its relation to (patho)physiology.
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Key Words
- BODIPY, Boron-dipyrromethene
- CARS, coherent anti-stokes Raman scattering
- CLEM, correlative light electron microscopy
- CLSM, confocal laser scanning microscopy
- DIC, differential interference microscopy
- FA, fatty acid
- FIB-SEM, focused ion beam scanning electron microscopy
- FLIP, fluorescence loss in photobleaching
- FRAP, fluorescent recovery after photobleaching
- FRET, fluorescence resonance energy transfer
- Fluorescent lipid probes
- GFP, green fluorescent protein
- HCV, hepatitis C virus
- LD, lipid droplet
- Lipid droplets
- Live-cell imaging
- Metabolic disease
- NBD, nitro-benzoxadiazolyl
- PALM, photoactivation localization microscopy
- SBEM, serial block face scanning electron microscopy
- SIMS, Secondary Ion Mass Spectrometry
- SRS, Stimulated Raman Scattering
- STED, stimulated emission depletion
- STORM, stochastic optical reconstruction microscopy
- Super-resolution
- TAG, triacylglycerol
- TEM, transmission electron microscopy
- TOF-SIMS, time-of-flight SIMS
- TPLSM, two-photon laser scanning microscopy
- Vibrational microscopy
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Wachsmuth M, Domin G, Lorenz R, Serfling R, Findeiß S, Stadler PF, Mörl M. Design criteria for synthetic riboswitches acting on transcription. RNA Biol 2015; 12:221-31. [PMID: 25826571 DOI: 10.1080/15476286.2015.1017235] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Riboswitches are RNA-based regulators of gene expression composed of a ligand-sensing aptamer domain followed by an overlapping expression platform. The regulation occurs at either the level of transcription (by formation of terminator or antiterminator structures) or translation (by presentation or sequestering of the ribosomal binding site). Due to a modular composition, these elements can be manipulated by combining different aptamers and expression platforms and therefore represent useful tools to regulate gene expression in synthetic biology. Using computationally designed theophylline-dependent riboswitches we show that 2 parameters, terminator hairpin stability and folding traps, have a major impact on the functionality of the designed constructs. These have to be considered very carefully during design phase. Furthermore, a combination of several copies of individual riboswitches leads to a much improved activation ratio between induced and uninduced gene activity and to a linear dose-dependent increase in reporter gene expression. Such serial arrangements of synthetic riboswitches closely resemble their natural counterparts and may form the basis for simple quantitative read out systems for the detection of specific target molecules in the cell.
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65
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Xu C, Feng K, Zhao X, Huang S, Cheng Y, Qian L, Wang Y, Sun H, Jin M, Chuang TH, Zhang Y. Regulation of autophagy by E3 ubiquitin ligase RNF216 through BECN1 ubiquitination. Autophagy 2015; 10:2239-50. [PMID: 25484083 PMCID: PMC4502788 DOI: 10.4161/15548627.2014.981792] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Autophagy is an evolutionarily conserved biological process involved in an array of physiological and pathological events. Without proper control, autophagy contributes to various disorders, including cancer and autoimmune and inflammatory diseases. It is therefore of vital importance that autophagy is under careful balance. Thus, additional regulators undoubtedly deepen our understanding of the working network, and provide potential therapeutic targets for disorders. In this study, we found that RNF216 (ring finger protein 216), an E3 ubiquitin ligase, strongly inhibits autophagy in macrophages. Further exploration demonstrates that RNF216 interacts with BECN1, a key regulator in autophagy, and leads to ubiquitination of BECN1, thereby contributing to BECN1 degradation. RNF216 was involved in the ubiquitination of lysine 48 of BECN1 through direct interaction with the triad (2 RING fingers and a DRIL [double RING finger linked]) domain. We further showed that inhibition of autophagy through overexpression of RNF216 in alveolar macrophages promotes Listeria monocytogenes growth and distribution, while knockdown of RNF216 significantly inhibited these outcomes. These effects were confirmed in a mouse model of L. monocytogenes infection, suggesting that manipulating RNF216 expression could be a therapeutic approach. Thus, our study identifies a novel negative regulator of autophagy and suggests that RNF216 may be a target for treatment of inflammatory diseases.
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Key Words
- Atg, autophagy-related
- BALF, bronchoalveolar lavage fluid
- BECN1
- BMDM, bone marrow-derived macrophage
- CFU, colony-forming unit
- GFP, green fluorescent protein
- HRP, horseradish peroxidase
- LPS, lipopolysaccharide
- MAP1LC3A, microtubule-associated protein 1 light chain 3 α
- MOI, multiplicity of infection
- NFKB, nuclear factor of kappa light polypeptide gene enhancer in B-cells
- PBS, phosphate-buffered saline
- RIPK1, receptor (TNFRSF)-interacting serine-threonine kinase 1
- RNF216
- RNF216, ring finger protein 216;TIRAP, toll-interleukin 1 receptor (TIR) domain containing adaptor protein
- TICAM1/TRIF, toll-like receptor adaptor molecule 1
- TICAM2, toll-like receptor adaptor molecule 2
- TLR, toll-like receptor
- TNF, tumor necrosis factor
- TRAF, TNF receptor-associated factor
- Triad, 2 RING fingers and a DRIL (double RING finger linked)
- Ub, ubiquitin
- autophagy
- i.t., intratracheally
- protein degradation
- shRNA, short hairpin RNA
- ubiquitination
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Brandstaetter H, Kishi-Itakura C, Tumbarello DA, Manstein DJ, Buss F. Loss of functional MYO1C/myosin 1c, a motor protein involved in lipid raft trafficking, disrupts autophagosome-lysosome fusion. Autophagy 2015; 10:2310-23. [PMID: 25551774 PMCID: PMC4502697 DOI: 10.4161/15548627.2014.984272] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
MYO1C, a single-headed class I myosin, associates with cholesterol-enriched lipid rafts and facilitates their recycling from intracellular compartments to the cell surface. Absence of functional MYO1C disturbs the cellular distribution of lipid rafts, causes the accumulation of cholesterol-enriched membranes in the perinuclear recycling compartment, and leads to enlargement of endolysosomal membranes. Several feeder pathways, including classical endocytosis but also the autophagy pathway, maintain the health of the cell by selective degradation of cargo through fusion with the lysosome. Here we show that loss of functional MYO1C leads to an increase in total cellular cholesterol and its disrupted subcellular distribution. We observe an accumulation of autophagic structures caused by a block in fusion with the lysosome and a defect in autophagic cargo degradation. Interestingly, the loss of MYO1C has no effect on degradation of endocytic cargo such as EGFR, illustrating that although the endolysosomal compartment is enlarged in size, it is functional, contains active hydrolases, and the correct pH. Our results highlight the importance of correct lipid composition in autophagosomes and lysosomes to enable them to fuse. Ablating MYO1C function causes abnormal cholesterol distribution, which has a major selective impact on the autophagy pathway.
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Key Words
- BafA1, bafilomycin A1
- EGF, epidermal growth factor
- EGFR, epidermal growth factor receptor
- EM, electron microscopy
- GFP, green fluorescent protein
- KD, knockdown
- LAMP1, lysosomal-associated membrane protein 1
- LC3, microtubule-associated protein 1 light chain 3
- MVB, multivesicular body
- MYO1C, myosin IC
- PB, phosphate buffer
- PCIP, pentachloropseudilin
- PtdIns(4, 5)P2, phosphatidylinositol 4, 5-bisphosphate
- RFP, red fluorescent protein
- RPE, retinal pigment epithelium
- autophagy
- cholesterol
- electron microscopy
- lipid raft
- lysosome, MYO1C
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Spang N, Feldmann A, Huesmann H, Bekbulat F, Schmitt V, Hiebel C, Koziollek-Drechsler I, Clement AM, Moosmann B, Jung J, Behrends C, Dikic I, Kern A, Behl C. RAB3GAP1 and RAB3GAP2 modulate basal and rapamycin-induced autophagy. Autophagy 2015; 10:2297-309. [PMID: 25495476 PMCID: PMC4502700 DOI: 10.4161/15548627.2014.994359] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Macroautophagy is a degradative pathway that sequesters and transports cytosolic cargo in autophagosomes to lysosomes, and its deterioration affects intracellular proteostasis. Membrane dynamics accompanying autophagy are mostly elusive and depend on trafficking processes. RAB GTPase activating proteins (RABGAPs) are important factors for the coordination of cellular vesicle transport systems, and several TBC (TRE2-BUB2-CDC16) domain-containing RABGAPs are associated with autophagy. Employing C. elegans and human primary fibroblasts, we show that RAB3GAP1 and RAB3GAP2, which are components of the TBC domain-free RAB3GAP complex, influence protein aggregation and affect autophagy at basal and rapamycin-induced conditions. Correlating the activity of RAB3GAP1/2 with ATG3 and ATG16L1 and analyzing ATG5 punctate structures, we illustrate that the RAB3GAPs modulate autophagosomal biogenesis. Significant levels of RAB3GAP1/2 colocalize with members of the Atg8 family at lipid droplets, and their autophagy modulatory activity depends on the GTPase-activating activity of RAB3GAP1 but is independent of the RAB GTPase RAB3. Moreover, we analyzed RAB3GAP1/2 in relation to the previously reported suppressive autophagy modulators FEZ1 and FEZ2 and demonstrate that both reciprocally regulate autophagy. In conclusion, we identify RAB3GAP1/2 as novel conserved factors of the autophagy and proteostasis network.
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Key Words
- ATG, autophagy-related
- ATG16L1
- ATG3
- BSA, bovine serum albumin
- Bafi, bafilomycin A1
- C. elegans, Caenorhabditis elegans
- CALCOCO2, calcium binding and coiled-coil domain 2
- DAPI, 4’, 6-diamidino-2-phenylindole
- DMSO, dimethyl sulfoxide
- DPH, 1, 6-diphenyl-1, 3, 5-hexatriene
- FEZ, fasciculation and elongation protein zeta
- FEZ1
- FEZ2
- GABARAP, GABA(A) receptor-associated protein
- GEF, guanine nucleotide exchange factor
- GFP, green fluorescent protein
- MAP1LC3, microtubule-associated protein 1 light chain 3
- NBR1, neighbor of BRCA1 gene 1
- PBS, phosphate-buffered saline
- PE, phosphatidylethanolamine
- RAB3GAP1
- RAB3GAP2
- RABGAP, RAB GTPase activating protein
- SQSTM1, sequestosome 1
- TBC domain, TRE2-BUB2-CDC16 domain
- autophagy
- eV, empty vector
- lipid droplets
- proteostasis
- siRNA, small interfering RNA
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Sarkar C, Zhao Z, Aungst S, Sabirzhanov B, Faden AI, Lipinski MM. Impaired autophagy flux is associated with neuronal cell death after traumatic brain injury. Autophagy 2015; 10:2208-22. [PMID: 25484084 PMCID: PMC4502690 DOI: 10.4161/15548627.2014.981787] [Citation(s) in RCA: 236] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Dysregulation of autophagy contributes to neuronal cell death in several neurodegenerative and lysosomal storage diseases. Markers of autophagy are also increased after traumatic brain injury (TBI), but its mechanisms and function are not known. Following controlled cortical impact (CCI) brain injury in GFP-Lc3 (green fluorescent protein-LC3) transgenic mice, we observed accumulation of autophagosomes in ipsilateral cortex and hippocampus between 1 and 7 d. This accumulation was not due to increased initiation of autophagy but rather to a decrease in clearance of autophagosomes, as reflected by accumulation of the autophagic substrate SQSTM1/p62 (sequestosome 1). This was confirmed by ex vivo studies, which demonstrated impaired autophagic flux in brain slices from injured as compared to control animals. Increased SQSTM1 peaked at d 1-3 but resolved by d 7, suggesting that the defect in autophagy flux is temporary. The early impairment of autophagy is at least in part caused by lysosomal dysfunction, as evidenced by lower protein levels and enzymatic activity of CTSD (cathepsin D). Furthermore, immediately after injury both autophagosomes and SQSTM1 accumulated predominantly in neurons. This was accompanied by appearance of SQSTM1 and ubiquitin-positive puncta in the affected cells, suggesting that, similar to the situation observed in neurodegenerative diseases, impaired autophagy may contribute to neuronal injury. Consistently, GFP-LC3 and SQSTM1 colocalized with markers of both caspase-dependent and caspase-independent cell death in neuronal cells proximal to the injury site. Taken together, our data indicated for the first time that autophagic clearance is impaired early after TBI due to lysosomal dysfunction, and correlates with neuronal cell death.
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Key Words
- ACTB, actin
- AIFM1, apoptosis-inducing factor, mitochondrion-associated, 1
- APC, adenomatous polyposis coli
- ATG12, autophagy-related 12
- ATG5, autophagy-related 5
- ATG7, autophagy-related 7
- CAPS12, caspase 12
- CASP3, caspase 3
- CCI, controlled cortical impact
- CD68, CD68 molecule
- CSPG4, chondroitin sulfate proteoglycan 4
- CTSD, cathepsin D
- GFP, green fluorescent protein
- LAMP1, lysosomal-associated membrane protein 1
- LAMP2, lysosomal-associated membrane protein 2
- LC3, microtubule associated protein 1 light chain 3
- RBFOX3, RNA binding protein, fox-1 homolog (C. elegans) 3
- SPTAN1, spectrin, α, non-erythrocytic 1
- SQSTM1, sequestosome 1
- TBI, traumatic brain injury
- ULK1, unc-51 like autophagy activating kinase 1
- autophagy
- autophagy flux
- lysosome
- neuronal cell death
- traumatic brain injury
- β; AIF1/IBA1, allograft inflammatory factor 1
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Wang Z, Hu J, Li G, Qu L, He Q, Lou Y, Song Q, Ma D, Chen Y. PHF23 (plant homeodomain finger protein 23) negatively regulates cell autophagy by promoting ubiquitination and degradation of E3 ligase LRSAM1. Autophagy 2015; 10:2158-70. [PMID: 25484098 DOI: 10.4161/auto.36439] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Autophagy is a multistep process that involves the degradation and digestion of intracellular components by the lysosome. It has been proved that many core autophagy-related molecules participate in this event. However, new component proteins that regulate autophagy are still being discovered. At present, we report PHF23 (PHD finger protein 23) with a PHD-like zinc finger domain that can negatively regulate autophagy. Data from experiments indicated that the overexpression of PHF23 impaired autophagy, as characterized by decreased levels of LC3B-II and weakened degradation of endogenous and exogenous autophagic substrates. Conversely, knockdown of PHF23 resulted in opposite effects. Molecular mechanism studies suggested that PHF23 interacts with LRSAM1, which is an E3 ligase key for ubiquitin-dependent autophagy against invading bacteria. PHF23 promotes the ubiquitination and proteasome degradation of LRSAM1. We also show that the PHD finger of PHF23 is a functional domain needed for the interaction with LRSAM1. Altogether, our results indicate that PHF23 is a negative regulator associated in autophagy via the LRSAM1 signaling pathway. The physical and functional connection between the PHF23 and LRSAM1 needs further investigation.
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Key Words
- AML, acute myeloid leukemia
- ATG, autophagy-related
- BafA1, bafilomycin A1
- CALCOCO2, calcium binding and coiled-coil domain 2
- CQ, chloroquine
- EBSS, Earle's balanced salt solution
- FBS, fetal bovine serum
- GFP, green fluorescent protein
- GST, glutathione S-transferase
- IP, immunoprecipitation
- LRSAM1
- LRSAM1, leucine rich repeat and sterile α motif containing 1
- MAP1LC3B/LC3B
- PHD domain
- PHD, plant homeodomain
- PHF23
- PHF23, PHD finger protein 23
- PIK3C3, phosphatidylinositol 3-kinase, catalytic subunit type 3
- SQSTM1, sequestosome 1
- Three-MA, 3-methyladenine
- autophagy
- microtubule-associated protein 1 light chain 3 β
- ubiquitination
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70
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Mimouna S, Bazin M, Mograbi B, Darfeuille-Michaud A, Brest P, Hofman P, Vouret-Craviari V. HIF1A regulates xenophagic degradation of adherent and invasive Escherichia coli (AIEC). Autophagy 2015; 10:2333-45. [PMID: 25484075 PMCID: PMC4502747 DOI: 10.4161/15548627.2014.984275] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The hypoxia inducible transcription factor HIF1 activates autophagy, a general catabolic pathway involved in the maintenance of cellular homeostasis. Dysfunction in both autophagy and HIF1 has been implicated in an increasing number of human diseases, including inflammatory bowel disease (IBD), such as Crohn disease (CD). Adherent invasive E. coli (AIEC) colonize ileal mucosa of CD patients and strongly promote gastrointestinal inflammatory disorders by activation of HIF-dependent responses. Here, we aim to characterize the contribution of HIF1 in xenophagy, a specialized form of autophagy involved in the degradation of intracellular bacteria. Our results showed that endogenous HIF1A knockdown increased AIEC survival in intestinal epithelial cells. We demonstrate that the increase in survival rate correlates with a dramatic impairment of the autophagic flux at the autolysosomal maturation step. Furthermore, we show that AIEC remained within single-membrane LC3-II-positive vesicles and that they were unable to induce the phosphorylation of ULK1. These results suggested that, in the absence of HIF1A, AIEC were found within LC3-associated phagosomes. Using blocking antibodies against TLR5 and CEACAM6, the 2 well-known AIEC-bound receptors, we showed that downstream receptor signaling was necessary to mediate ULK1 phosphorylation. Finally, we provide evidence that HIF1 mediates CEACAM6 expression and that CEACAM6 is necessary to recruit ULK1 in a bacteria-containing signaling hub. Collectively, these results identify a new function for HIF1 in AIEC-dedicated xenophagy, and suggest that coactivation of autophagy and HIF1A expression may be a potential new therapy to resolve AIEC infection in CD patients.
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Key Words
- AIEC, adherent invasive E. coli
- AMPK, AMP-activated protein kinase
- ATG16L1, autophagy-related 16-like 1
- ATG5, autophagy-related 5
- BECN1, Beclin 1, autophagy-related
- BNIP3L, BCL2/adenovirus E1B 19kDa interacting protein 3-like
- CD, Crohn disease
- CEACAM6, carcinoembryonic antigen-related cell adhesion molecule 6 (nonspecific cross reacting antigen)
- CRTC1/TORC1, CREB regulated transcription coactivator 1
- Crohn disease
- EEA1, early endosome antigen 1
- GFP, green fluorescent protein
- HBSS, Hank's balanced salt solution
- HIF1A, hypoxia inducible factor 1, α subunit (basic helix-loop-helix transcription factor)
- IBD, inflammatory bowel disease
- IRGM, immunity-related GTPase family, M
- LAP
- LAP, LC3-associated phagocytosis
- MAP1LC3-II (LC3-II), microtubule-associated protein 1 light chain 3-II
- MOI, multiplicity of infection
- SQSTM1/p62 (SQSTM1), sequestosome 1
- TEM, transmission electron microscopy
- TLR5, toll-like receptor 5
- ULK1, unc-51 like autophagy activating kinase 1
- VAV2, vav 2 guanine nucleotide exchange factor
- autophagy
- bacteria
- hypoxia inducible factor
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Cull B, Prado Godinho JL, Fernandes Rodrigues JC, Frank B, Schurigt U, Williams RA, Coombs GH, Mottram JC. Glycosome turnover in Leishmania major is mediated by autophagy. Autophagy 2015; 10:2143-57. [PMID: 25484087 PMCID: PMC4502677 DOI: 10.4161/auto.36438] [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] [Indexed: 12/17/2022] Open
Abstract
Autophagy is a central process behind the cellular remodeling that occurs during differentiation of Leishmania, yet the cargo of the protozoan parasite's autophagosome is unknown. We have identified glycosomes, peroxisome-like organelles that uniquely compartmentalize glycolytic and other metabolic enzymes in Leishmania and other kinetoplastid parasitic protozoa, as autophagosome cargo. It has been proposed that the number of glycosomes and their content change during the Leishmania life cycle as a key adaptation to the different environments encountered. Quantification of RFP-SQL-labeled glycosomes showed that promastigotes of L. major possess ~20 glycosomes per cell, whereas amastigotes contain ~10. Glycosome numbers were significantly greater in promastigotes and amastigotes of autophagy-defective L. major Δatg5 mutants, implicating autophagy in glycosome homeostasis and providing a partial explanation for the previously observed growth and virulence defects of these mutants. Use of GFP-ATG8 to label autophagosomes showed glycosomes to be cargo in ~15% of them; glycosome-containing autophagosomes were trafficked to the lysosome for degradation. The number of autophagosomes increased 10-fold during differentiation, yet the percentage of glycosome-containing autophagosomes remained constant. This indicates that increased turnover of glycosomes was due to an overall increase in autophagy, rather than an upregulation of autophagosomes containing this cargo. Mitophagy of the single mitochondrion was not observed in L. major during normal growth or differentiation; however, mitochondrial remnants resulting from stress-induced fragmentation colocalized with autophagosomes and lysosomes, indicating that autophagy is used to recycle these damaged organelles. These data show that autophagy in Leishmania has a central role not only in maintaining cellular homeostasis and recycling damaged organelles but crucially in the adaptation to environmental change through the turnover of glycosomes.
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72
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Niyogi S, Docampo R. A novel role of Rab11 in trafficking GPI-anchored trans-sialidase to the plasma membrane of Trypanosoma cruzi. Small GTPases 2015; 6:8-10. [PMID: 25862161 DOI: 10.4161/21541248.2014.978712] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Trypanosoma cruzi, the causative agent of Chagas disease, is a unicellular parasite that possesses a contractile vacuole complex (CVC). This organelle is usually present in free-living protists and is mainly involved in osmoregulation. However, in some organisms, like for example Dictyostelium discoideum, other roles include calcium homeostasis and transference of proteins to the plasma membrane. T. cruzi plasma membrane is very rich in glycosylphosphatidylinositol anchored proteins (GPI-AP) and a very important group of GPI-AP is that of the trans-sialidases. These enzymes catalyze the transfer of sialic acid from host glycoconjugates to mucins present in the surface of the parasite and are important for host cell invasion among other functions. We recently reported that a pathway dependent on the Rab GTPase Rab11 is involved in the traffic of trans-sialidases to the plasma membrane through the CVC of the infective stages of the parasite and that preventing this traffic results in considerable reduction in the ability of T. cruzi to infect host cells. We also found that traffic of other GPI-anchored proteins is also through the CVC but uses a Rab11-independent pathway. These represent unconventional pathways of GPI-anchored protein traffic to the plasma membrane.
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73
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Chang W, Antoku S, Östlund C, Worman HJ, Gundersen GG. Linker of nucleoskeleton and cytoskeleton (LINC) complex-mediated actin-dependent nuclear positioning orients centrosomes in migrating myoblasts. Nucleus 2015; 6:77-88. [PMID: 25587885 DOI: 10.1080/19491034.2015.1004947] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Myoblast migration is essential for muscle development and repair; however, the factors that contribute to the polarity of migrating myoblasts are relatively unknown. We find that randomly migrating C2C12 myoblasts orient their centrosomes in the direction of migration. Using wounded monolayers, we further show that centrosome orientation is stimulated by the serum factor lysophosphatidic acid (LPA) and involves the rearward movement of the nucleus while the centrosome is maintained at the cell centroid. The rate of nuclear movement correlated with that of actin retrograde flow and both cytochalasin D and blebbistatin prevented nuclear movement and centrosome orientation. Actin-dependent rearward nuclear movement in fibroblasts is mediated by assembly of nuclear membrane nesprin-2G and SUN2 LINC complexes into transmembrane actin-associated nuclear (TAN) lines anchored by A-type lamins and emerin. In C2C12 myoblasts, depletion of nesprin-2G, SUN2 or lamin A/C prevented nuclear movement and endogenous nesprin-2G and a chimeric GFP-mini-nesprin-2G formed TAN lines during nuclear movement. Depleting nesprin-2G strongly interfered with directed cell migration and reduced the efficiency of myoblast fusion into multinucleated myotubes. Our results show that nuclear movement contributes to centrosome orientation and polarity for efficient migration and fusion of myoblasts. Given that mutations in the genes encoding A-type lamins, nesprin-2 and SUN2 cause Emery-Dreifuss muscular dystrophy and related myopathies, our results have implications for understanding the mechanism of disease pathogenesis.
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Corral-Ramos C, Roca MG, Di Pietro A, Roncero MIG, Ruiz-Roldán C. Autophagy contributes to regulation of nuclear dynamics during vegetative growth and hyphal fusion in Fusarium oxysporum. Autophagy 2015; 11:131-44. [PMID: 25560310 DOI: 10.4161/15548627.2014.994413] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the fungal pathogen Fusarium oxysporum, vegetative hyphal fusion triggers nuclear mitotic division in the invading hypha followed by migration of a nucleus into the receptor hypha and degradation of the resident nucleus. Here we examined the role of autophagy in fusion-induced nuclear degradation. A search of the F. oxysporum genome database for autophagy pathway components identified putative orthologs of 16 core autophagy-related (ATG) genes in yeast, including the ubiquitin-like protein Atg8, which is required for the formation of autophagosomal membranes. F. oxysporum Foatg8Δ mutants were generated in a strain harboring H1-cherry fluorescent protein (ChFP)-labeled nuclei to facilitate analysis of nuclear dynamics. The Foatg8Δ mutants did not show MDC-positive staining in contrast to the wild type and the FoATG8-complemented (cFoATG8) strain, suggesting that FoAtg8 is required for autophagy in F. oxysporum. The Foatg8Δ strains displayed reduced rates of hyphal growth, conidiation, and fusion, and were significantly attenuated in virulence on tomato plants and in the nonvertebrate animal host Galleria mellonella. In contrast to wild-type hyphae, which are almost exclusively composed of uninucleated hyphal compartments, the hyphae of the Foatg8Δ mutants contained a significant fraction of hyphal compartments with 2 or more nuclei. The increase in the number of nuclei per hyphal compartment was particularly evident after hyphal fusion events. Time-lapse microscopy analyses revealed abnormal mitotic patterns during vegetative growth in the Foatg8Δ mutants. Our results suggest that autophagy mediates nuclear degradation after hyphal fusion and has a general function in the control of nuclear distribution in F. oxysporum.
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Key Words
- Atg, autophagy-related
- BLAST, basic local alignment search tool
- CFW, calcofluor white
- ChFP, cherry fluorescent protein
- DIC, differential interference contrast
- Fusarium oxysporum
- GFP, green fluorescent protein
- HygR, hygromycin resistant
- MDC, monodansylcadaverine
- ORF, open reading frame
- PCR, polymerase chain reaction
- PDA, potato dextrose agar
- PDB, potato dextrose broth
- PMSF, phenylmethylsulfonyl fluoride
- SM, synthetic medium
- WT, wild-type
- autophagy
- filamentous fungi
- gDNA, genomic DNA
- hyphal fusion
- nuclear dynamics
- virulence
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Kim JH, Hong SB, Lee JK, Han S, Roh KH, Lee KE, Kim YK, Choi EJ, Song HK. Insights into autophagosome maturation revealed by the structures of ATG5 with its interacting partners. Autophagy 2015; 11:75-87. [PMID: 25484072 DOI: 10.4161/15548627.2014.984276] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Autophagy is a bulky catabolic process that responds to nutrient homeostasis and extracellular stress signals and is a conserved mechanism in all eukaryotes. When autophagy is induced, cellular components are sequestered within an autophagosome and finally degraded by subsequent fusion with a lysosome. During this process, the ATG12-ATG5 conjugate requires 2 different binding partners, ATG16L1 for autophagosome elongation and TECPR1 for lysosomal fusion. In our current study, we describe the crystal structures of human ATG5 in complex with an N-terminal domain of ATG16L1 as well as an internal AIR domain of TECPR1. Both binding partners exhibit a similar α-helical structure containing a conserved binding motif termed AFIM. Furthermore, we characterize the critical role of the C-terminal unstructured region of the AIR domain of TECPR1. These findings are further confirmed by biochemical and cell biological analyses. These results provide new insights into the molecular details of the autophagosome maturation process, from its elongation to its fusion with a lysosome.
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Key Words
- AFIM, ATG5 (5)-interacting motif
- AIR, ATG12–ATG5-interacting region
- ATG, autophagy-related
- ATG12
- ATG16
- ATG16N69, ATG16L1 N-terminal 69 residues
- ATG5
- DAPI, 4’, 6-diamidino-2-phenylindole
- FITC, fluorescein isothiocyanate
- FLuc, firefly luciferase
- FP, fluorescent polarization
- GAL4-BD, GAL4-DNA binding domain
- GFP, green fluorescent protein
- HR, helix rich
- ITC, isothermal titration calorimetry
- MR, molecular replacement
- PE, phosphatidylethanolamine
- PH, pleckstrin homology
- PtdIns3P, phosphatidylinositol 3-phosphate
- RLuc, Renilla luciferase
- SPR, surface plasmon resonance
- TECAIR, TECPR1 AIR
- TECPR1
- TECPR1, tectonin β-propeller repeat containing 1
- UFD, ubiquitin-fold domain
- Ubl, ubiquitin-like protein
- VP16-AD, herpes simplex virus VP16 transcription activation domain
- autophagy
- buffer A, buffer containing 50 mM Tris-HCl, pH 8.0, 300 mM NaCl, and 1 mM TCEP
- crystal structure
- lysosome fusion
- r.m.s., root-mean-square
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