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Abstract
Autophagy and senescence have been described as central features of cell biology, but the interplay between these mechanisms remains obscure. Using a therapeutically relevant model of DNA damage-induced senescence in human glioma cells, we demonstrated that acute treatment with temozolomide induces DNA damage, a transitory activation of PRKAA/AMPK-ULK1 and MAPK14/p38 and the sustained inhibition of AKT-MTOR. This produced a transient induction of autophagy, which was followed by senescence. However, at the single cell level, this coordinated transition was not observed, and autophagy and senescence were triggered in a very heterogeneous manner. Indeed, at a population level, autophagy was highly negatively correlated with senescence markers, while in single cells this correlation did not exist. The inhibition of autophagy triggered apoptosis and decreased senescence, while its activation increased temozolomide-induced senescence, showing that DNA damage-induced autophagy acts by suppressing apoptosis.
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Key Words
- 3MA, 3-methyladenine
- AMP-activated
- AO, acridine orange
- BafA1, bafilomycin A1
- CDKN1A/p21, cyclin-dependent kinase inhibitor 1A (p21 Cip1)
- CPD, cumulative population doubling
- DDR, DNA damage response
- DFM, drug-free medium
- DNA damage
- H2AFX, H2A histone family
- MAP1LC3A/LC3, microtubule-associated protein 1 light chain 3 α
- MTOR, mechanistic target of rapamycin
- MTORC1, MTOR complex 1
- NA, nuclear area
- NMA, nuclear morphometric analysis
- PRKAA/AMPKα, protein kinase
- RAPA, rapamycin
- RPTOR/RAPTOR, regulatory-associated protein of MTOR
- SA-β-gal, senescence associated β-galactosidase assay
- SQSTM1/p62, sequestosome 1
- TMZ, temozolomide
- autophagy
- cP1-4, cellular population 1 to 4
- complex 1
- member X
- nP1–5, nuclear population 1 to 5
- senescence
- single cell
- temozolomide
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2
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Filippi-Chiela EC, Bueno e Silva MM, Thomé MP, Lenz G. Single-cell analysis challenges the connection between autophagy and senescence induced by DNA damage. Autophagy. 2015;11:1099-1113. [PMID: 25701485 DOI: 10.0180/15548627.2015.1009795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Autophagy and senescence have been described as central features of cell biology, but the interplay between these mechanisms remains obscure. Using a therapeutically relevant model of DNA damage-induced senescence in human glioma cells, we demonstrated that acute treatment with temozolomide induces DNA damage, a transitory activation of PRKAA/AMPK-ULK1 and MAPK14/p38 and the sustained inhibition of AKT-MTOR. This produced a transient induction of autophagy, which was followed by senescence. However, at the single cell level, this coordinated transition was not observed, and autophagy and senescence were triggered in a very heterogeneous manner. Indeed, at a population level, autophagy was highly negatively correlated with senescence markers, while in single cells this correlation did not exist. The inhibition of autophagy triggered apoptosis and decreased senescence, while its activation increased temozolomide-induced senescence, showing that DNA damage-induced autophagy acts by suppressing apoptosis.
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Key Words
- 3MA, 3-methyladenine
- AMP-activated
- AO, acridine orange
- BafA1, bafilomycin A1
- CDKN1A/p21, cyclin-dependent kinase inhibitor 1A (p21 Cip1)
- CPD, cumulative population doubling
- DDR, DNA damage response
- DFM, drug-free medium
- DNA damage
- H2AFX, H2A histone family
- MAP1LC3A/LC3, microtubule-associated protein 1 light chain 3 α
- MTOR, mechanistic target of rapamycin
- MTORC1, MTOR complex 1
- NA, nuclear area
- NMA, nuclear morphometric analysis
- PRKAA/AMPKα, protein kinase
- RAPA, rapamycin
- RPTOR/RAPTOR, regulatory-associated protein of MTOR
- SA-β-gal, senescence associated β-galactosidase assay
- SQSTM1/p62, sequestosome 1
- TMZ, temozolomide
- autophagy
- cP1-4, cellular population 1 to 4
- complex 1
- member X
- nP1–5, nuclear population 1 to 5
- senescence
- single cell
- temozolomide
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3
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Abstract
Tafazzin (TAZ) is a phospholipid transacylase that catalyzes the remodeling of cardiolipin, a mitochondrial phospholipid required for oxidative phosphorylation. Mutations of TAZ cause Barth syndrome, which is characterized by mitochondrial dysfunction and dilated cardiomyopathy, leading to premature death. However, the molecular mechanisms underlying the cause of mitochondrial dysfunction in Barth syndrome remain poorly understood. Here we investigated the role of TAZ in regulating mitochondrial function and mitophagy. Using primary mouse embryonic fibroblasts (MEFs) with doxycycline-inducible knockdown of Taz, we showed that TAZ deficiency in MEFs caused defective mitophagosome biogenesis, but not other autophagic processes. Consistent with a key role of mitophagy in mitochondria quality control, TAZ deficiency in MEFs also led to impaired oxidative phosphorylation and severe oxidative stress. Together, these findings provide key insights on mitochondrial dysfunction in Barth syndrome, suggesting that pharmacological restoration of mitophagy may provide a novel treatment for this lethal condition.
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Key Words
- AdGFP-LC3, recombinant adenovirus expressing GFP tagged MAP1LC3B
- AdTAZ, recombinant adenovirus expressing Myc-tagged TAZ
- BTHS, Barth syndrome
- BafA1, bafilomycin A1
- Barth syndrome
- CCCP, carbonyl cyanide m-chlorophenylhydrazone
- CL, cardiolipin
- Dox, doxycycline
- FCCP, carbonyl cyanide p-triflouromethoxyphenylhydrazone
- LTG, LysoTracker Green
- MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 beta
- MEF, mouse embryonic fibroblast
- MLCL, monolysocardiolipin
- MTR, MitoTracker Red
- PARK2, parkin RBR E3 ubiquitin protein ligase
- PINK1, PTEN-induced putative kinase 1
- SOD2, superoxide dismutase 2 mitochondrial
- TAZ, tafazzin
- TLCL, tetralinoleoyl-cardiolipin
- autophagy
- cardiolipin
- mitochondrial dysfunction
- mitophagosome
- mitophagy
- tafazzin
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Affiliation(s)
- Paul Hsu
- a Department of Cellular and Molecular Physiology ; Hershey , PA USA
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Shen WC, Li HY, Chen GC, Chern Y, Tu PH. Mutations in the ubiquitin-binding domain of OPTN/optineurin interfere with autophagy-mediated degradation of misfolded proteins by a dominant-negative mechanism. Autophagy 2016; 11:685-700. [PMID: 25484089 DOI: 10.4161/auto.36098] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
OPTN (optineurin) is an autophagy receptor and mutations in the OPTN gene result in familial glaucoma (E50K) and amyotrophic lateral sclerosis (ALS) (E478G). However, the mechanisms through which mutant OPTN leads to human diseases remain to be characterized. Here, we demonstrated that OPTN colocalized with inclusion bodies (IBs) formed by mutant HTT/huntingtin protein (mHTT) in R6/2 transgenic mice and IBs formed by 81QNmHTT (nuclear form), 109QmHTT (cytoplasmic form) or the truncated form of TARDBP/TDP-43 (TARDBP(ND251)) in Neuro2A cells. This colocalization required the ubiquitin (Ub)-binding domain (UbBD, amino acids 424 to 511) of OPTN. Overexpression of wild-type (WT) OPTN decreased IBs through K63-linked polyubiquitin-mediated autophagy. E50K or 210 to 410Δ (with amino acids 210 to 410 deleted) whose mutation or deletion was outside the UbBD decreased the IBs formed by 109QmHTT or TARDBP(ND251), as was the case with WT OPTN. In contrast, UbBD mutants, including E478G, D474N, UbBDΔ, 411 to 520Δ and 210 to 520Δ, increased accumulation of IBs. UbBD mutants (E478G, UbBDΔ) retained a substantial ability to interact with WT OPTN, and were found to colocalize with polyubiquitinated IBs, which might occur indirectly through their WT partner in a WT-mutant complex. They decreased autophagic flux evidenced by alteration in LC3 level and turnover and in the number of LC3-positive puncta under stresses like starvation or formation of IBs. UbBD mutants exhibited a weakened interaction with MYO6 (myosin VI) and TOM1 (target of myb1 homolog [chicken]), important for autophagosome maturation, in cells or sorted 109QmHtt IBs. Taken together, our data indicated that UbBD mutants acted as dominant-negative traps through the formation of WT-mutant hybrid complexes to compromise the maturation of autophagosomes, which in turn interfered with OPTN-mediated autophagy and clearance of IBs.
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Key Words
- ALS, amyotrophic lateral sclerosis
- Ab, antibody
- BafA1, bafilomycin A1
- CCD, coiled-coil domain
- Ef, FRET efficiency
- FT, filter-trap assay
- HD, Huntington disease
- IBs, inclusion bodies
- IP, immunoprecipitation
- K48, lysine 48
- K63, lysine 63
- LIR, LC3-interacting region
- MYO6, myosin VI
- OPTN, optineurin
- PBS, phosphate-buffered saline
- PFA, paraformaldehyde
- TARDBP/TDP-43
- TARDBP/TDP-43, TAR DNA-binding protein
- TBK1, TANK-binding kinase 1
- TUBA, alpha tubulin
- UPS, ubiquitin-proteasome system
- Ub, ubiquitin B/C/D
- UbBD, ubiquitin-binding domain
- WB, western blot
- WT, wild type
- autophagy
- dominant-negative
- huntingtin
- mHTT, mutant huntingtin
- optineurin
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Affiliation(s)
- Wen-Chuan Shen
- a Taiwan International Graduate Program in Molecular Medicine; National Yang-Ming University and Academia Sinica ; Taipei , Taiwan
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Melland-Smith M, Ermini L, Chauvin S, Craig-Barnes H, Tagliaferro A, Todros T, Post M, Caniggia I. Disruption of sphingolipid metabolism augments ceramide-induced autophagy in preeclampsia. Autophagy 2016; 11:653-69. [PMID: 25853898 DOI: 10.1080/15548627.2015.1034414] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Bioactive sphingolipids including ceramides are involved in a variety of pathophysiological processes by regulating cell death and survival. The objective of the current study was to examine ceramide metabolism in preeclampsia, a serious disorder of pregnancy characterized by oxidative stress, and increased trophoblast cell death and autophagy. Maternal circulating and placental ceramide levels quantified by tandem mass spectrometry were elevated in pregnancies complicated by preeclampsia. Placental ceramides were elevated due to greater de novo synthesis via high serine palmitoyltransferase activity and reduced lysosomal breakdown via diminished ASAH1 expression caused by TGFB3-induced E2F4 transcriptional repression. SMPD1 activity was reduced; hence, sphingomyelin degradation by SMPD1 did not contribute to elevated ceramide levels in preeclampsia. Oxidative stress triggered similar changes in ceramide levels and acid hydrolase expression in villous explants and trophoblast cells. MALDI-imaging mass spectrometry localized the ceramide increases to the trophophoblast layers and syncytial knots of placentae from pregnancies complicated by preeclampsia. ASAH1 inhibition or ceramide treatment induced autophagy in human trophoblast cells via a shift of the BOK-MCL1 rheostat toward prodeath BOK. Pharmacological inhibition of ASAH1 activity in pregnant mice resulted in increased placental ceramide content, abnormal placentation, reduced fetal growth, and increased autophagy via a similar shift in the BOK-MCL1 system. Our results reveal that oxidative stress-induced reduction of lysosomal hydrolase activities in combination with elevated de novo synthesis leads to ceramide overload, resulting in increased trophoblast cell autophagy, and typifies preeclampsia as a sphingolipid storage disorder.
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Key Words
- 2-OE, 2-oleoylethanolamine
- 3-KDS, 3-keto dihydrosphingosine
- 3-MA, 3-methyladenine
- ACTB, actin β
- ASAH1, N-acylsphingosine amidohydrolase (acid ceramidase) 1
- BECN1, Beclin 1, autophagy related
- BOK
- BOK, BCL2-related ovarian killer
- BafA1, bafilomycin A1
- CANX, calnexin
- CASP3 (caspase 3, apoptosis-related cysteine peptidase)
- CERs, ceramides
- CT, cytotrophoblast cells
- D-NMAPPD, N-[(1R,2R)-2-hydroxyl-1-(hydroxyL-methyl)-2-(4-nitrophenyl) ethyl]-tetradecanamide
- DHCer, dihydro-ceramide
- E2F4, E2F transcription factor 4, p107/p130-binding
- HIF1A, hypoxia inducible factor 1, α, subunit (basic helix-loop-helix transcription factor)
- LAMP1, lysosomal-associated membrane protein 1
- LC-MS/MS, liquid chromatography-tandem mass spectrometry
- LC3B-II, cleaved and lipidated form of microtubule-associated protein 1 light chain 3 β (MAP1LC3B/LC3B)
- MALDI-MS, matrix-assisted laser desorption/ionization-mass spectrometry
- MCL1
- MCL1, myeloid cell leukemia 1
- PE, preeclampsia
- PTC, preterm control
- S1P, sphingosine-1-phosphate
- SM, sphingomyelin
- SMPD1, sphingomyelin phosphodiesterase 1, acid lysosomal (acid sphingomyelinase)
- SNP, sodium nitroprusside (III)
- SPH, sphingosine
- SPT, serine palmitoyltransferase
- SQSTM1/p62, sequestosome 1
- ST, syncytium/syncytiotrophoblast cells
- Sa, sphinganine
- TC, term control
- TGFB, transforming growth factor β
- autophagy
- oxidative stress
- placenta
- preeclampsia
- siRNA, small-interfering ribonucleic acid
- sphingolipid metabolism
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Affiliation(s)
- Megan Melland-Smith
- a The Lunenfeld-Tanenbaum Research Institute; Mount Sinai Hospital ; Toronto , ON Canada
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Namkoong S, Lee KI, Lee JI, Park R, Lee EJ, Jang IS, Park J. The integral membrane protein ITM2A, a transcriptional target of PKA-CREB, regulates autophagic flux via interaction with the vacuolar ATPase. Autophagy 2016; 11:756-68. [PMID: 25951193 PMCID: PMC4509440 DOI: 10.1080/15548627.2015.1034412] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The PKA-CREB signaling pathway is involved in many cellular processes including autophagy. Recent studies demonstrated that PKA-CREB inhibits autophagy in yeast; however, the role of PKA-CREB signaling in mammalian cell autophagy has not been fully characterized. Here, we report that the integral membrane protein ITM2A expression is positively regulated by PKA-CREB signaling and ITM2A expression interferes with autophagic flux by interacting with vacuolar ATPase (v-ATPase). The ITM2A promoter contains a CRE element, and mutation at the CRE consensus site decreases the promoter activity. Forskolin treatment and PKA expression activate the ITM2A promoter confirming that ITM2A expression is dependent on the PKA-CREB pathway. ITM2A expression results in the accumulation of autophagosomes and interferes with autolysosome formation by blocking autophagic flux. We demonstrated that ITM2A physically interacts with v-ATPase and inhibits lysosomal function. These results support the notion that PKA-CREB signaling pathway regulates ITM2A expression, which negatively regulates autophagic flux by interfering with the function of v-ATPase.
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Key Words
- BafA1, bafilomycin A1
- CRE, cAMP response element
- CREB
- CREB, cAMP responsive element binding protein
- ChIP, chromatin immunoprecipitation
- EBSS, Earle's balanced salt solution
- ITM2A
- ITM2A, integral membrane protein 2A
- LAMP1, lysosomal-associated membrane protein 1
- MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 β
- MAPK, mitogen-activated protein kinase
- MTOR, mechanistic target of rapamycin
- PKA
- PKA, protein kinase A
- SQSTM1, sequestosome 1
- TPA, 12-O-tetradecanoylphorbol-13-acetate
- autophagy
- cAMP, cyclic adenosine monophosphate
- tfLC3, tandem fluorescent-tagged LC3
- v-ATPase
- v-ATPase, vacuolar ATPase.
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Affiliation(s)
- Sim Namkoong
- a Division of Biological Science and Technology; Yonsei University ; Wonju , Korea
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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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Affiliation(s)
- Ruina He
- a Biodynamic Optical Imaging Center (BIOPIC); Peking-Tsinghua Center for Life Sciences; State Key Laboratory of Protein and Plant Gene Research; School of Life Sciences; Peking University ; Beijing , China
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Zhang SF, Wang XY, Fu ZQ, Peng QH, Zhang JY, Ye F, Fu YF, Zhou CY, Lu WG, Cheng XD, Xie X. TXNDC17 promotes paclitaxel resistance via inducing autophagy in ovarian cancer. Autophagy 2016; 11:225-38. [PMID: 25607466 DOI: 10.1080/15548627.2014.998931] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Paclitaxel is recommended as a first-line chemotherapeutic agent against ovarian cancer, but drug resistance becomes a major limitation of its success clinically. The key molecule or mechanism associated with paclitaxel resistance in ovarian cancer still remains unclear. Here, we showed that TXNDC17 screened from 356 differentially expressed proteins by LC-MS/MS label-free quantitative proteomics was more highly expressed in paclitaxel-resistant ovarian cancer cells and tissues, and the high expression of TXNDC17 was associated with poorer prognostic factors and exhibited shortened survival in 157 ovarian cancer patients. Moreover, paclitaxel exposure induced upregulation of TXNDC17 and BECN1 expression, increase of autophagosome formation, and autophagic flux that conferred cytoprotection for ovarian cancer cells from paclitaxel. TXNDC17 inhibition by siRNA or enforced overexpression by a pcDNA3.1(+)-TXNDC17 plasmid correspondingly decreased or increased the autophagy response and paclitaxel resistance. Additionally, the downregulation of BECN1 by siRNA attenuated the activation of autophagy and cytoprotection from paclitaxel induced by TXNDC17 overexpression in ovarian cancer cells. Thus, our findings suggest that TXNDC17, through participation of BECN1, induces autophagy and consequently results in paclitaxel resistance in ovarian cancer. TXNDC17 may be a potential predictor or target in ovarian cancer therapeutics.
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Key Words
- 95% CI, 95% confidence interval
- ALDOC, aldolase C, fructose-bisphosphate
- ATG5, autophagy-related 5
- BECN1
- BECN1, Beclin 1, autophagy-related
- BafA1, bafilomycin A1
- CNN3, calponin 3, acidic
- DAPI, 4', 6-diamidino-2-phenylindole
- FLNA, filamin A, α
- GO, gene ontology
- GenMAPP, gene microarray pathway profiler
- HBSS, Hank's balanced salt solution
- HR, hazard ratio
- KEGG, Kyoto encyclopedia of genes and genome
- LC-MS/MS, liquid chromatography-mass spectrometry/ mass spectrometry
- MAP1LC3B/LC3B, microtubule-associated protein 1 light chain 3 β
- OS, overall survival
- PFS, progression-free survival
- PGAM1, phosphoglycerate mutase 1 (brain)
- SQSTM1, sequestosome 1
- TNF, tumor necrosis factor
- TXN, thioredoxin
- TXNDC17
- TXNDC17, thioredoxin domain containing 17
- UTP23, small subunit (SSU) processome component, homolog (yeast)
- autophagy
- ovarian cancer
- paclitaxel resistance
- siRNA, short interfering RNA
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Affiliation(s)
- Song-Fa Zhang
- a Women's Reproductive Health Laboratory of Zhejiang Province; Women's Hospital; School of Medicine ; Zhejiang University ; Hangzhou , China
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Affiliation(s)
- Hemma Brandstaetter
- a Cambridge Institute for Medical Research ; University of Cambridge ; Cambridge , UK
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10
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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: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Affiliation(s)
- Zhenda Wang
- a Key Laboratory of Medical Immunology; Ministry of Health ; Peking University Health Science Center ; Beijing , China
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Lefort S, Joffre C, Kieffer Y, Givel AM, Bourachot B, Zago G, Bieche I, Dubois T, Meseure D, Vincent-Salomon A, Camonis J, Mechta-Grigoriou F. Inhibition of autophagy as a new means of improving chemotherapy efficiency in high-LC3B triple-negative breast cancers. Autophagy 2015; 10:2122-42. [PMID: 25427136 DOI: 10.4161/15548627.2014.981788] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The triple-negative breast cancer (TN BC) subtype is the most aggressive form of invasive BC. Despite intensive efforts to improve BC treatments, patients with TN BC continue to exhibit poor survival, with half developing resistance to chemotherapy. Here we identify autophagy as a key mechanism in the progression and chemoresistance of a subset of TN tumors. We demonstrate that LC3B, a protein involved in autophagosome formation, is a reliable marker of poor prognosis in TN BC, validating this prognostic value at both the mRNA and protein levels in several independent cohorts. We also show that LC3B has no prognostic value for other BC subtypes (Luminal or HER2 BC), thus revealing a specific impact of autophagy on TN tumors. Autophagy is essential for the proliferative and invasive properties in 3D of TN BC cells characterized by high LC3B levels. Interestingly, the activity of the transcriptional co-activator YAP1 (Yes-associated protein 1) is regulated by the autophagy process and we identify YAP1 as a new actor in the autophagy-dependent proliferative and invasive properties of high-LC3B TN BC. Finally, inhibiting autophagy by silencing ATG5 or ATG7 significantly impaired high-LC3B TN tumor growth in vivo. Moreover, using a patient-derived TN tumor transplanted into mice, we show that an autophagy inhibitor, chloroquine, potentiates the effects of chemotherapeutic agents. Overall, our data identify LC3B as a new prognostic marker for TN BC and the inhibition of autophagy as a promising therapeutic strategy for TN BC patients.
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Key Words
- 3-dimensional culture
- 3D, 3-dimensions
- AC, adriamycin and cyclophosphamide
- ACTB, actin, β
- AP2A1/adaptin, adaptor-related protein complex 2, α 1 subunit
- ATG, autophagy-related
- BC, breast cancer
- BECN1, Beclin 1, autophagy related
- BafA1, bafilomycin A1
- Ctrl, control
- DFS, disease-free survival
- EBSS, Earle's balanced salt solution
- ERBB2/HER2, v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- HScore, histological scoring
- IHC, immunohistochemistry
- LC3B
- Lum, Luminal
- MAP1LC3B/LC3B, microtubule-associated protein one light chain 3 β
- OS, overall survival
- PDX, patient-derived xenografted tumor
- TCGA, The Cancer Genome Atlas
- TGI, tumor growth inhibition
- TN BC, triple-negative breast cancer
- YAP1
- YAP1, Yes-associated protein 1
- autophagy
- breast cancers
- i.p., intra-peritoneal
- prognosis
- response to treatment
- sem, standard error of mean
- three-MA, 3-methyladenine
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Affiliation(s)
- Sylvain Lefort
- a Laboratory of Stress and Cancer; Institut Curie ; Paris , France
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Abstract
Lysosomes play important roles in autophagy, not only in autophagosome degradation, but also in autophagy initiation. In Trypanosoma brucei, an early divergent protozoan parasite, we discovered a previously unappreciated function of the acidocalcisome, a lysosome-related organelle characterized by acidic pH and large content of Ca(2+) and polyphosphates, in autophagy regulation. Starvation- and chemical-induced autophagy is accompanied with acidocalcisome acidification, and blocking the acidification completely inhibits autophagosome formation. Blocking acidocalcisome biogenesis by depleting the adaptor protein-3 complex, which does not affect lysosome biogenesis or function, also inhibits autophagy. Overall, our results support the role of the acidocalcisome, a conserved organelle from bacteria to human, as a relevant regulator in autophagy.
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Key Words
- AO, acridine orange
- AP-3, adaptor protein-3
- ATG, autophagy-related
- BODIPY-CQ, BODIPY-chloroquine
- BafA1, bafilomycin A1
- CQ, chloroquine
- DAPI, 4′, 6-diamidino-2-phenylindole
- MTORC1, mechanistic target of rapamycin complex 1
- PPi, pyrophosphate
- PtdIns3K, phosphatidylinositol 3-kinase
- PtdIns3P, phosphatidylinositol 3-phosphate
- RNAi, RNA interference
- T. brucei, Trypanosoma brucei
- TOR, target of rapamycin
- TbVMA1, the subunit A of V-H+-ATPase in Trypanosoma brucei
- TbVP1, vacuolar pyrophosphatase in Trypanosoma brucei
- TbVPH1, the α, subunit of V-H+-ATPase in Trypanosoma brucei
- Tbβ3, the β3 subunit of adaptor protein-3 complex in Trypanosoma brucei
- Tbδ, the δ, subunit of adaptor protein-3 complex in Trypanosoma brucei
- Trypanosoma brucei
- V-H+-ATPase, vacuolar-type H+-ATPase
- V-PPase, vacuolar pyrophophatase
- acidity
- acidocalcisome
- autophagy
- coumarin-CQ, coumarin-chloroquine
- lysosome-related organelle
- polyP, polyphosphate
- protozoan parasite
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Affiliation(s)
- Feng-Jun Li
- a Department of Biological Sciences ; National University of Singapore ; Singapore
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