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1.  E4F1 dysfunction results in autophagic cell death in myeloid leukemic cells 
Autophagy  2011;7(12):1566-1567.
The multifunctional E4F1 protein was originally identified as a cellular target of the E1A adenoviral oncoprotein. Although E4F1 is implicated in several key oncogenic pathways, its roles in tumorigenesis remain unclear. Using a genetically engineered mouse model of myeloid leukemia (histiocytic sarcomas, HS) based on the genetic inactivation of the tumor suppressor Ink4a/Arf locus, we have recently unraveled an unsuspected function of E4F1 in the survival of leukemic cells. In vivo, genetic ablation of E4F1 in established myeloid tumors results in tumor regression. E4F1 inactivation results in a cascade of alterations originating from dysfunctional mitochondria that induce increased reactive oxygen species (ROS) levels and ends in massive autophagic cell death in HS transformed, but not normal myeloid cells. E4F1 depletion also induces cell death in various human myeloid leukemic cell lines, including acute myeloid leukemic (AML) cell lines. Interestingly, the E4F1 protein is overexpressed in a large proportion of human AML samples. These data provide new insights into E4F1-associated survival functions implicated in tumorigenesis and could open the path for new therapeutic strategies.
PMCID: PMC3288034  PMID: 22024746
E4F1; histiocytic sarcoma; mitochondria; autophagy; cell death; leukemic cells; reactive oxygen species
2.  E4F1 dysfunction results in autophagic cell death in myeloid leukemic cells 
Autophagy  2011;7(12):1566-1567.
The multifunctional E4F1 protein was originally identified as a cellular target of the E1A adenoviral oncoprotein. Although E4F1 is implicated in several key oncogenic pathways, its roles in tumorigenesis remain unclear. Using a genetically engineered mouse model of myeloid leukemia (histiocytic sarcomas, HS) based on the genetic inactivation of the tumor suppressor Ink4a/Arf locus, we have recently unraveled an unsuspected function of E4F1 in the survival of leukemic cells. In vivo, genetic ablation of E4F1 in established myeloid tumors results in tumor regression. E4F1 inactivation results in a cascade of alterations originating from dysfunctional mitochondria that induce increased reactive oxygen species (ROS) levels and ends in massive autophagic cell death in HS transformed, but not normal myeloid cells. E4F1 depletion also induces cell death in various human myeloid leukemic cell lines, including acute myeloid leukemic (AML) cell lines. Interestingly, the E4F1 protein is overexpressed in a large proportion of human AML samples. These data provide new insights into E4F1-associated survival functions implicated in tumorigenesis and could open the path for new therapeutic strategies.
PMCID: PMC3288034  PMID: 22024746
Animals; Autophagy; Cell Survival; Cell Transformation, Neoplastic; pathology; Disease Models, Animal; Humans; Leukemia, Myeloid; metabolism; pathology; Mice; RNA, Small Interfering; metabolism; Reactive Oxygen Species; metabolism; Repressor Proteins; metabolism; E4F1; histiocytic sarcoma; mitochondria; autophagy; cell death; leukemic cells; reactive oxygen species
3.  Ancient autophagy 
Autophagy  2013;9(4):445-446.
These days, when we talk about the origin of a protein, or even a pathway, we are typically referring to evolutionary lineages based on nucleotide sequences. For example, is a particular protein’s function conserved? How far back did it first appear? Are there homologs in higher eukaryotes? However, a simpler question (or perhaps I should say, a non-molecular biology question) is when was the process first detected in the paleontological record? Of course I assumed that macroautophagy was ancient, but a new finding (see p. 632 in this issue of the journal) provides an unexpected—and exciting—piece of information for our field. For the first time, scientists have discovered fossil evidence for an actual subcellular pathway—and it looks like it might actually be autophagy (I admit I am biased, but you can decide for yourself).
PMCID: PMC3627661  PMID: 23388466
autophagy; fossil; lysosome; stress; vacuole
4.  Autophagy researchers 
Autophagy  2013;9(4):447-450.
PMCID: PMC3627662
5.  DAMPs and autophagy 
Autophagy  2013;9(4):451-458.
Autophagy is a lysosome-mediated catabolic process involving the degradation of intracellular contents (e.g., proteins and organelles) as well as invading microbes (e.g., parasites, bacteria and viruses). Multiple forms of cellular stress can stimulate this pathway, including nutritional imbalances, oxygen deprivation, immunological response, genetic defects, chromosomal anomalies and cytotoxic stress. Damage-associated molecular pattern molecules (DAMPs) are released by stressed cells undergoing autophagy or injury, and act as endogenous danger signals to regulate the subsequent inflammatory and immune response. A complex relationship exists between DAMPs and autophagy in cellular adaption to injury and unscheduled cell death. Since both autophagy and DAMPs are important for pathogenesis of human disease, it is crucial to understand how they interplay to sustain homeostasis in stressful or dangerous environments.
PMCID: PMC3627663  PMID: 23388380
autophagy; DAMP; stress; HMGB1; ATP; IL1B; injury
6.  Ambra1 knockdown in zebrafish leads to incomplete development due to severe defects in organogenesis 
Autophagy  2013;9(4):476-495.
AMBRA1 is a positive regulator of the BECN1-dependent program of autophagy recently identified in mouse. In this study, we cloned the full-length cDNAs of ambra1a and ambra1b zebrafish paralogous genes. As in mouse, both Ambra1 proteins contain the characteristic WD40 repeat region. The transcripts of both genes are present as maternal RNAs in the eggs and display a gradual decline until 8 hpf, being replaced by zygotic mRNAs from 12 hpf onwards. After 24 hpf, the transcripts are mainly localized in the head, suggesting a possible role in brain development. To check their developmental roles, we adopted morpholino knockdown to block either translation (ATGMOs) or splicing (SPLICMOs). Treatment with ATGMOs causes severe embryonic malformations, as prelarvae could survive for only 3 and 4 days in ambra1a and b morphants, respectively. Treatment with SPLICMOs led to developmental defects only at a late stage, indicating the importance of maternally supplied ambra1 transcripts. Analysis of the levels of Lc3-II, an autophagosome-specific marker, in the presence of lysosome inhibitors evidenced a reduction in the rate of autophagosome formation in both MOs-injected embryos at 48 hpf, more pronounced in the case of ambra1a gene. Although some defects, such as body growth delay, curved shape and hemorrhagic pericardial cavity were present in both morphants, the occurrence of specific phenotypes, such as major abnormalities of brain development in ambra1a morphants, suggests the possible acquisition of specific functions by the two paralogous genes that are both required during development and do not compensate each other following knockdown.
PMCID: PMC3627665  PMID: 23348054
Ambra1; zebrafish; autophagy; development; morpholino
7.  Visualizing the autophagy pathway in avian cells and its application to studying infectious bronchitis virus 
Autophagy  2013;9(4):496-509.
Autophagy is a highly conserved cellular response to starvation that leads to the degradation of organelles and long-lived proteins in lysosomes and is important for cellular homeostasis, tissue development and as a defense against aggregated proteins, damaged organelles and infectious agents. Although autophagy has been studied in many animal species, reagents to study autophagy in avian systems are lacking. Microtubule-associated protein 1 light chain 3 (MAP1LC3/LC3) is an important marker for autophagy and is used to follow autophagosome formation. Here we report the cloning of avian LC3 paralogs A, B and C from the domestic chicken, Gallus gallus domesticus, and the production of replication-deficient, recombinant adenovirus vectors expressing these avian LC3s tagged with EGFP and FLAG-mCherry. An additional recombinant adenovirus expressing EGFP-tagged LC3B containing a G120A mutation was also generated. These vectors can be used as tools to visualize autophagosome formation and fusion with endosomes/lysosomes in avian cells and provide a valuable resource for studying autophagy in avian cells. We have used them to study autophagy during replication of infectious bronchitis virus (IBV). IBV induced autophagic signaling in mammalian Vero cells but not primary avian chick kidney cells or the avian DF1 cell line. Furthermore, induction or inhibition of autophagy did not affect IBV replication, suggesting that classical autophagy may not be important for virus replication. However, expression of IBV nonstructural protein 6 alone did induce autophagic signaling in avian cells, as seen previously in mammalian cells. This may suggest that IBV can inhibit or control autophagy in avian cells, although IBV did not appear to inhibit autophagy induced by starvation or rapamycin treatment.
PMCID: PMC3627666  PMID: 23328491
chicken; avian; GFP-LC3; autophagy; primary cells; recombinant adenovirus; coronavirus; infectious bronchitis virus; LC3A; LC3B; LC3C
8.  M98K-OPTN induces transferrin receptor degradation and RAB12-mediated autophagic death in retinal ganglion cells 
Autophagy  2013;9(4):510-527.
Mutations in the autophagy receptor OPTN/optineurin are associated with the pathogenesis of glaucoma and amyotrophic lateral sclerosis, but the underlying molecular basis is poorly understood. The OPTN variant, M98K has been described as a risk factor for normal tension glaucoma in some ethnic groups. Here, we examined the consequence of the M98K mutation in affecting cellular functions of OPTN. Overexpression of M98K-OPTN induced death of retinal ganglion cells (RGC-5 cell line), but not of other neuronal and non-neuronal cells. Enhanced levels of the autophagy marker, LC3-II, a post-translationally modified form of LC3, in M98K-OPTN-expressing cells and the inability of an LC3-binding-defective M98K variant of OPTN to induce cell death, suggested that autophagy contributes to cell death. Knockdown of Atg5 reduced M98K-induced death of RGC-5 cells, further supporting the involvement of autophagy. Overexpression of M98K-OPTN enhanced autophagosome formation and potentiated the delivery of transferrin receptor to autophagosomes for degradation resulting in reduced cellular transferrin receptor levels. Coexpression of transferrin receptor or supplementation of media with an iron donor reduced M98K-induced cell death. OPTN complexes with RAB12, a GTPase involved in vesicle trafficking, and M98K variant shows enhanced colocalization with RAB12. Knockdown of Rab12 increased transferrin receptor level and reduced M98K-induced cell death. RAB12 is present in autophagosomes and knockdown of Rab12 resulted in reduced formation of autolysosomes during starvation-induced autophagy, implicating a role for RAB12 in autophagy. These results also show that transferrin receptor degradation and autophagy play a crucial role in RGC-5 cell death induced by M98K variant of OPTN.
PMCID: PMC3627667  PMID: 23357852
optineurin; autophagy; transferrin receptor; RAB12; glaucoma; retinal ganglion cells
9.  ATG5 regulates plasma cell differentiation 
Autophagy  2013;9(4):528-537.
Autophagy is a conserved homeostatic process in which cytoplasmic contents are degraded and recycled. Two ubiquitin-like conjugation pathways are required for the generation of autophagosomes, and ATG5 is necessary for both of these processes. Studies of mice deficient in ATG5 reveal a key role for autophagy in T lymphocyte function, as well as in B cell development and B-1a B cell maintenance. However, the role of autophagy genes in B cell function and antibody production has not been described. Using mice in which Atg5 is conditionally deleted in B lymphocytes, we showed here that this autophagy gene is essential for plasma cell homeostasis. In the absence of B cell ATG5 expression, antibody responses were significantly diminished during antigen-specific immunization, parasitic infection and mucosal inflammation. Atg5-deficient B cells maintained the ability to produce immunoglobulin and undergo class-switch recombination, yet had impaired SDC1 expression, significantly decreased antibody secretion in response to toll-like receptor ligands, and an inability to upregulate plasma cell transcription factors. These results build upon previous data demonstrating a role for ATG5 in early B cell development, illustrating its importance in late B cell activation and subsequent plasma cell differentiation.
PMCID: PMC3627668  PMID: 23327930
B lymphocytes; ATG5; plasma cell differentiation; antibody secretion; immunity
10.  Linkage of autophagy to fungal development, lipid storage and virulence in Metarhizium robertsii 
Autophagy  2013;9(4):538-549.
Autophagy is a highly conserved process that maintains intracellular homeostasis by degrading proteins or organelles in all eukaryotes. The effect of autophagy on fungal biology and infection of insect pathogens is unknown. Here, we report the function of MrATG8, an ortholog of yeast ATG8, in the entomopathogenic fungus Metarhizium robertsii. MrATG8 can complement an ATG8-defective yeast strain and deletion of MrATG8 impaired autophagy, conidiation and fungal infection biology in M. robertsii. Compared with the wild-type and gene-rescued mutant, Mratg8Δ is not inductive to form the infection-structure appressorium and is impaired in defense response against insect immunity. In addition, accumulation of lipid droplets (LDs) is significantly reduced in the conidia of Mratg8Δ and the pathogenicity of the mutant is drastically impaired. We also found that the cellular level of a LD-specific perilipin-like protein is significantly lowered by deletion of MrATG8 and that the carboxyl terminus beyond the predicted protease cleavage site is dispensable for MrAtg8 function. To corroborate the role of autophagy in fungal physiology, the homologous genes of yeast ATG1, ATG4 and ATG15, designated as MrATG1, MrATG4 and MrATG15, were also deleted in M. robertsii. In contrast to Mratg8Δ, these mutants could form appressoria, however, the LD accumulation and virulence were also considerably impaired in the mutant strains. Our data showed that autophagy is required in M. robertsii for fungal differentiation, lipid biogenesis and insect infection. The results advance our understanding of autophagic process in fungi and provide evidence to connect autophagy with lipid metabolism.
PMCID: PMC3627669  PMID: 23380892
Metarhizium robertsii; autophagy; appressorium; sporulation; cell differentiation; perilipin; lipid metabolism; virulence
11.  Hypertonic stress promotes autophagy and microtubule-dependent autophagosomal clusters 
Autophagy  2013;9(4):550-567.
Osmotic homeostasis is fundamental for most cells, which face recurrent alterations of environmental osmolality that challenge cell viability. Protein damage is a consequence of hypertonic stress, but whether autophagy contributes to the osmoprotective response is unknown. Here, we investigated the possible implications of autophagy and microtubule organization on the response to hypertonic stress. We show that hypertonicity rapidly induced long-lived protein degradation, LC3-II generation and Ptdlns3K-dependent formation of LC3- and ATG12-positive puncta. Lysosomotropic agents chloroquine and bafilomycin A1, but not nutrient deprivation or rapamycin treatment, further increased LC3-II generation, as well as ATG12-positive puncta, indicating that hypertonic stress increases autophagic flux. Autophagy induction upon hypertonic stress enhanced cell survival since cell death was increased by ATG12 siRNA-mediated knockdown and reduced by rapamycin. We additionally showed that hypertonicity induces fast reorganization of microtubule networks, which is associated with strong reorganization of microtubules at centrosomes and fragmentation of Golgi ribbons. Microtubule remodeling was associated with pericentrosomal clustering of ATG12-positive autolysosomes that colocalized with SQSTM1/p62 and ubiquitin, indicating that autophagy induced by hypertonic stress is at least partly selective. Efficient autophagy by hypertonic stress required microtubule remodeling and was DYNC/dynein-dependent as autophagosome clustering was enhanced by paclitaxel-induced microtubule stabilization and was reduced by nocodazole-induced tubulin depolymerization as well as chemical (EHNA) or genetic [DCTN2/dynactin 2 (p50) overexpression] interference of DYNC activity. The data document a general and hitherto overlooked mechanism, where autophagy and microtubule remodeling play prominent roles in the osmoprotective response.
PMCID: PMC3627670  PMID: 23380587
autophagy; osmotic stress; microtubule; tubulin; apoptosis; rapamycin; ATG12; MAP1LC3/LC3; SQSTM1/p62; ubiquitin; MAPRE1/EB1; dynein; lysosome; proteasome; Golgi apparatus; MTOC
12.  Features of autophagic cell death in Plasmodium liver-stage parasites 
Autophagy  2013;9(4):568-580.
Analyzing molecular determinants of Plasmodium parasite cell death is a promising approach for exploring new avenues in the fight against malaria. Three major forms of cell death (apoptosis, necrosis and autophagic cell death) have been described in multicellular organisms but which cell death processes exist in protozoa is still a matter of debate. Here we suggest that all three types of cell death occur in Plasmodium liver-stage parasites. Whereas typical molecular markers for apoptosis and necrosis have not been found in the genome of Plasmodium parasites, we identified genes coding for putative autophagy-marker proteins and thus concentrated on autophagic cell death. We characterized the Plasmodium berghei homolog of the prominent autophagy marker protein Atg8/LC3 and found that it localized to the apicoplast. A relocalization of PbAtg8 to autophagosome-like vesicles or vacuoles that appear in dying parasites was not, however, observed. This strongly suggests that the function of this protein in liver-stage parasites is restricted to apicoplast biology.
PMCID: PMC3627671  PMID: 23388496
Plasmodium liver-stage; malaria; parasite death; autophagy-like cell death; Atg8; Atg3; Atg7; membrane expansion; apicoplast; organelle growth
13.  Synthesis and screening of 3-MA derivatives for autophagy inhibitors 
Autophagy  2013;9(4):595-603.
Autophagy is a conserved degradation process, which plays important pathophysiological roles. The lack of effective inhibitors of autophagy has been an obstacle in both basic research and understanding the physiological role of autophagy in disease manifestation. The most widely used inhibitor, 3-methyladenine (3-MA), is poorly soluble at room temperature and is effective only at high concentrations. In this study, we synthesized a library of small compounds by chemically modifying 3-MA and screened this library for autophagy inhibitors. Three 3-MA derivatives generated through this approach showed improved solubility and effectiveness in inhibiting autophagy. We demonstrated that chemical modification of an existing autophagy inhibitor is an effective method to generate improved autophagy inhibitors.
PMCID: PMC3627673  PMID: 23412639
autophagy; inhibitor; 3-MA; synthesis; derivatives
14.  Nutrient-driven O-GlcNAc cycling influences autophagic flux and neurodegenerative proteotoxicity 
Autophagy  2013;9(4):604-606.
O-GlcNAcylation is an abundant post-translational modification implicated in human neurodegenerative diseases. We showed that loss-of-function of OGT (O-linked GlcNAc transferase) alleviated, while loss of OGA (O-GlcNAc selective β-N-acetyl-D-glucosaminidase) enhanced, the proteotoxicity of C. elegans neurodegenerative disease models including tauopathy, β-amyloid peptide and polyglutamine expansion. The O-GlcNAc cycling mutants act, in part, by altering insulin signaling, proteasome activity and autophagy. In mutants lacking either of these enzymes of O-GlcNAc cycling, there is a striking accumulation of GFP::LGG-1 (C. elegans homolog of Atg8 and LC3) and increased phosphatidylethanolamine (PE)-modified GFP::LGG-1 upon starvation. We speculate that O-GlcNAc cycling is a key nutrient-responsive regulator of autophagic flux acting at multiple levels including direct modification of BECN1 and BCL2.
PMCID: PMC3627674  PMID: 23328586
neurodegeneration; proteotoxicity; O-GlcNAc; proteostasis; autophagy; proteasome; insulin signaling
15.  Involvement of autophagy in the response of tumor cells to PtdIns3K inhibitors 
Autophagy  2013;9(4):607-608.
The phosphoinositide 3-kinase (PI3K) pathway plays a crucial role in cell proliferation and survival and is frequently activated by genetic and epigenetic alterations in human cancer. An arsenal of pharmacological inhibitors of key signaling enzymes in this pathway, including class IA PI3K isoforms, has been developed in the past decade and several compounds have entered clinical testing in cancer patients. The PIK3CA/p110α isoform is the most studied enzyme of the family and a validated cancer target. The induction of autophagy by PI3K pathway inhibitors has been documented in various cancers, although a clear picture about the significance of this phenomenon is still missing, especially in the in vivo situation. A better understanding of the contribution of autophagy to the action of PI3K inhibitors on tumors cells is important, since it may limit or enhance the action of these compounds, depending on the cellular context.
PMCID: PMC3627675  PMID: 23324613
apoptosis; autophagy; BCL2; MTOR; PI3K; small cell lung cancer
16.  PERK-ing up autophagy during MYC-induced tumorigenesis 
Autophagy  2013;9(4):612-614.
Stress in the tumor microenvironment in the form of hypoxia and low glucose/amino acid levels activates the evolutionarily conserved cellular adaptation program called the unfolded protein response (UPR) promoting cell survival in such conditions. Our recent studies showed that cell autonomous stress such as activation of the proto-oncogene MYC/c-Myc, can also trigger the UPR and induce endoplasmic reticulum (ER) stress-mediated autophagy. Amelioration of ER stress or autophagy enhances cancer cell death in vitro and attenuates tumor growth in vivo. Here we will discuss the role of the UPR and autophagy in MYC-induced transformation. Our findings demonstrate that the EIF2AK3/PERK-EIF2S1/eIF2α-ATF4 arm of the UPR promotes tumorigenesis by activating autophagy and enhancing tumor formation. Therefore, the UPR is an attractive target in MYC-driven cancers.
PMCID: PMC3627677  PMID: 23328692
unfolded protein response; EIF2AK3/PERK; c-Myc; ULK1; ATF4; Burkitt lymphoma
17.  The role of mannose-6-phosphate receptor and autophagy in influencing the outcome of combination therapy 
Autophagy  2013;9(4):615-616.
Combining two different treatment modalities for targeting malignancies is gaining importance, with preclinical/clinical results indicating higher success rates in eradicating tumors or having longer remission periods. A better understanding of the synergy between the treatments helps in optimizing the dose and time of administration. We found that chemotherapy enhanced the levels of insulin-like growth factor 2 receptor/cation-independent mannose-6-phosphate receptor (IGF2R) on the surface of tumor cells, which leads to better tumor targeting by cytotoxic T cells (CTLs). Early evidence indicates that upregulation of IGF2R involves the autophagy pathway.
PMCID: PMC3627678  PMID: 23324210
chemotherapy; immunotherapy; mannose-6-phosphate receptor; autophagy
18.  Latrepirdine (Dimebon®), a potential Alzheimer therapeutic, regulates autophagy and neuropathology in an Alzheimer mouse model 
Autophagy  2013;9(4):617-618.
Alzheimer disease (AD) is a form of neurodegeneration that develops over the course of multiple decades and as a result of the accumulation of the pathogenic amyloid-β (Aβ) peptide, also known as A4. In late-stage AD, failure of autophagic clearance results in neuronal cell bodies that are almost entirely consumed by autophagic vacuoles (AVs). Previously, we have shown that the potential AD drug latrepirdine (aka Dimebon®), a Russian antihistamine that has shown mixed results in phase II clinical trials in AD, regulates metabolism of the amyloid-β/A4 precursor protein (APP). In two Molecular Psychiatry papers in 2012, we sought to determine the mechanism through which latrepirdine regulates APP metabolism and to determine, using an Alzheimer mouse model, whether latrepirdine provides protection from the toxicity associated with the accumulation of Aβ. In cultured cells, we provided evidence that latrepirdine stimulates MTOR- and ATG5-dependent autophagy, leading to the reduction of intracellular levels of APP metabolites, including Aβ. Consistent with this finding, we found that chronic latrepirdine administration resulted in increased levels of the biomarkers thought to correlate with autophagy activation in the brains of TgCRND8 (APP K670M, N671L, V717F) or wild-type mice, and that treatment was associated with abrogation of behavioral deficit, reduction in Aβ neuropathology, and prevention of autophagic failure among TgCRND8 mice.
PMCID: PMC3627679  PMID: 23380933
Alzheimer; therapeutics; latrepirdine; dimebon; synuclein; macroautophagy; amyloid; lysosome; presenilin; neurodegeneration
19.  Targeting NFKB by autophagy to polarize hepatoma-associated macrophage differentiation 
Autophagy  2013;9(4):619-621.
Tumor-associated macrophages (TAMs) have been linked to promoting tumor progression by stimulating angiogenesis, cell growth and inflammation. NFKB activity in TAMs may mediate inflammation-associated tumor formation. However, most isolated TAMs from established tumors express a M2 phenotype with less NFKB activation and show a strong immunosuppressive phenomenon. How tumors affect the dynamic of NFKB activity in TAMs, and hence maintain their pro-tumor M2 phenotype is still poorly understood. We recently found that hepatoma-derived toll-like receptor 2 (TLR2)-related ligands are capable of stimulating M2 macrophage differentiation via controlling NFKB RELA/p65 protein homeostasis by selective autophagy. TLR2 signal induces NFKB RELA cytosolic ubiquitination and leads to its degradation by SQSTM1/p62-mediated autophagy. Inhibition of autophagy will rescue NFKB activity and shape the phenotype of hepatoma-polarized M2 macrophages. This suggests that autophagy might play a role in manipulating TAM functions and tumor-associated immune responses. Our study also demonstrates that autophagy can directly control a transcriptional factor in addition to its regulatory molecules. This finding uncovers a new role of autophagy in controlling cellular functions.
PMCID: PMC3627680  PMID: 23360732
tumor-associated macrophages; selective autophagy; NFKB; TLR2; SQSTM1/p62
20.  Degradation of the endoplasmic reticulum by autophagy in plants 
Autophagy  2013;9(4):622-623.
Eukaryotic cells have developed sophisticated strategies to contend with environmental stresses faced in their lifetime. Endoplasmic reticulum (ER) stress occurs when the accumulation of unfolded proteins within the ER exceeds the folding capacity of ER chaperones. ER stress responses have been well characterized in animals and yeast, and autophagy has been suggested to play an important role in recovery from ER stress. In plants, the unfolded protein response signaling pathways have been studied, but changes in ER morphology and ER homeostasis during ER stress have not been analyzed previously. Autophagy has been reported to function in tolerance of several stress conditions in plants, including nutrient deprivation, salt and drought stresses, oxidative stress, and pathogen infection. However, whether autophagy also functions during ER stress has not been investigated. The goal of our study was to elucidate the role and regulation of autophagy during ER stress in Arabidopsis thaliana.
PMCID: PMC3627681  PMID: 23360963
endoplasmic reticulum; autophagy; Arabidopsis; IRE1; ER stress
21.  Regulation of interplay between autophagy and apoptosis in the diabetic heart 
Autophagy  2013;9(4):624-625.
Diabetes induces cardiomyocyte apoptosis and suppresses cardiac autophagy, indicating that the interplay between autophagy and apoptotic cell death pathways is important in the pathogenesis of diabetic cardiomyopathy. The potential mechanism, however, remains unknown. We recently reported that diabetes depresses AMP-activated protein kinase (AMPK) activity, inhibits MAPK8/JNK1-BCL2 signaling, and promotes the interaction between BECN1 and BCL2. Concomitantly, diabetes induces cardiomyocyte apoptosis and suppresses cardiac autophagy. Activation of AMPK directly phosphorylates MAPK8, which mediates BCL2 phosphorylation and subsequent BECN1-BCL2 dissociation, leading to restoration of cardiac autophagy, protection against cardiac apoptosis, and ultimately improvement in cardiac structure and function. We conclude that dissociation of BCL2 from BECN1 through activation of MAPK8-BCL2 signaling may be an important mechanism by which AMPK activation restores autophagy, protects against cardiac apoptosis, and prevents diabetic cardiomyopathy.
PMCID: PMC3627682  PMID: 23380689
autophagy; AMPK; diabetes; cardiomyopathy; apoptosis
22.  Improvement of ER stress-induced diabetes by stimulating autophagy 
Autophagy  2013;9(4):626-628.
Pancreatic β-cell dysfunction is central in diabetes. The diabetic milieu may impair proinsulin folding, leading to β-cell endoplasmic reticulum (ER) stress and apoptosis, and thus a worsening of the diabetes. Autophagy is crucial for the well-being of the β-cell; however, the impact of stimulating autophagy on β-cell adaptation to ER stress is unknown. We studied the crosstalk between ER stress and autophagy in a rodent model of diabetes, called Akita, in which proinsulin gene mutation leads to protein misfolding and β-cell demise. We found that proinsulin misfolding stimulates autophagy and, in symmetry, inhibition of autophagy induces β-cell stress and apoptosis. Under conditions of excessive proinsulin misfolding, stimulation of autophagy by inhibiting MTORC1 alleviates stress and prevents apoptosis. Moreover, treatment of diabetic Akita mice with the MTORC1 inhibitor rapamycin improves diabetes and prevents β-cell apoptosis. Thus, autophagy is a central adaptive mechanism in β-cell stress. Stimulation of autophagy may become a novel therapeutic strategy in diabetes.
PMCID: PMC3627683  PMID: 23380813
diabetes; beta-cell; ER stress; MTOR; rapamycin; autophagy
23.  Autophagy in Antarctica 
Autophagy  2013;9(4):629-631.
The midge Belgica antarctica is the only insect endemic to Antarctica and has the southernmost range of any insect. In its natural environment, B. antarctica frequently faces desiccating conditions, as environmental water is frozen for up to 9 months annually. The molecular mechanisms by which B. antarctica tolerates extreme dehydration are poorly understood, but recent work from our laboratory reports genome-wide expression changes in response to extreme dehydration (~40% water loss), the first genome-scale transcriptome reported for an Antarctic animal. Among transcripts differentially regulated during dehydration, there is coordinated upregulation of numerous genes involved in autophagy, including genes responsible for autophagosome synthesis and autophagy-associated transcription factors. Also, several genes and pathways that interact with and regulate autophagy, e.g., sestrins and proteasomal genes, are concurrently upregulated. This suggests that autophagy and related processes are key elements regulating stress tolerance in this extreme environment.
PMCID: PMC3627684  PMID: 23380735
antarctic midge; dehydration; environmental stress; RNA-seq; autophagy; sestrin
24.  Impaired autophagy by soluble endoglin, under physiological hypoxia in early pregnant period, is involved in poor placentation in preeclampsia 
Autophagy  2013;9(3):303-316.
In early pregnancy, trophoblasts and the fetus experience hypoxic and low-nutrient conditions; nevertheless, trophoblasts invade the uterine myometrium up to one third of its depth and migrate along the lumina of spiral arterioles, replacing the maternal endothelial lining. Here, we showed that autophagy, an intracellular bulk degradation system, occurred in extravillous trophoblast (EVT) cells under hypoxia in vitro and in vivo. An enhancement of autophagy was observed in EVTs in early placental tissues, which suffer from physiological hypoxia. The invasion and vascular remodeling under hypoxia were significantly reduced in autophagy-deficient EVT cells compared with wild-type EVT cells. Interestingly, soluble endoglin (sENG), which increased in sera in preeclamptic cases, suppressed EVT invasion by inhibiting autophagy. The sENG-inhibited EVT invasion was recovered by TGFB1 treatment in a dose-dependent manner. A high dose of sENG inhibited the vascular construction by EVT cells and human umbilical vein endothelial cells (HUVECs), meanwhile a low dose of sENG inhibited the replacement of HUVECs by EVT cells. A protein selectively degraded by autophagy, SQSTM1, accumulated in EVT cells in preeclamptic placental biopsy samples showing impaired autophagy. This is the first report showing that impaired autophagy in EVT contributes to the pathophysiology of preeclampsia.
PMCID: PMC3590252  PMID: 23321791
autophagy; extravillous trophoblast; hypoxia; invasion; preeclampsia; SQSTM1; soluble endoglin
25.  Finding autophagy 
Autophagy  2013;9(3):267.
To tell the truth, I find it difficult to work when flying, or even when sitting in an airport for an extended period of time. So, typically I take along a book to read. And when I truly cannot concentrate, for example when a flight is considerably delayed, I have even been known to resort to word puzzles. Depending on the type, they do not require much attention (that is, you can pick up right where you left off after you glance at the flight status screen for the twentieth or so time, even though you know nothing has changed), or effort (although you need to use a pen or pencil, not a keyboard), but nonetheless they can keep your mind somewhat occupied. I even rationalize doing them based on the assumption that they are sharpening my observational/pattern-finding skills. One type of word puzzle that is particularly mindless, but for that very reason I still enjoy in the above circumstances, is a word search; you are given a grid with letters and/or numbers, and a list of “hidden” terms, and you circle them within the grid, crossing them off the list as you go along. I do admit that the categories of terms used in the typical word searches can become rather mundane (breeds of dog, types of food, words that are followed by “stone,” words associated with a famous movie star, words from a particular television show, etc.). Therefore, on one of my last seminar trips I decided to generate my own word search, using the category of autophagy.
PMCID: PMC3590247  PMID: 23322216
autophagy; lysosome; stress; vacuole; word search

Résultats 1-25 (586)