RESUMEN

Recently, emerging evidence has suggested that obesity become a prevalent health threat worldwide. Reportedly, CTRP9 can ameliorate HFD induced obesity. However, the molecular mechanism underlying the role of CTRP9 in obesity remains elusive. In this study, we reported its major function in the regulation of lipolysis. First, we found that the expression of CTRP9 was decreased in mature adipocytes and white adipose tissue of obese mice. Then, we showed that overexpression adipose tissue CTRP9 alleviated diet-induced obesity and adipocytes hypertrophy, improved glucose intolerance and raised energy expenditure. Moreover, CTRP9 increased the lipolysis in vitro and vivo. Additionally, we determined that CTRP9 enhanced autophagy flux in adipocytes. Intriguingly, knock down Beclin1 by SiRNA abolished the effect of CTRP9 on lipolysis. Mechanically, CTRP9 enhanced the expression of SNX26. We demonstrated that SNX26 was a component of the ATG14L-Beclin1-VPS34 complex and enhanced the assembly of the autophagy-initiation complex. Collectively, our results suggested that CTRP9 alleviated diet induced obesity through enhancing lipolysis mediated by autophagy-initiation complex formation.

Asunto(s)

Adipocitos , Autofagia , Beclina-1 , Lipólisis , Ratones Endogámicos C57BL , Obesidad , Animales , Obesidad/metabolismo , Ratones , Masculino , Adipocitos/metabolismo , Beclina-1/metabolismo , Dieta Alta en Grasa/efectos adversos , Células 3T3-L1 , Proteínas Relacionadas con la Autofagia/metabolismo , Proteínas Relacionadas con la Autofagia/genética , Adiponectina/metabolismo , Metabolismo Energético , Glicoproteínas

RESUMEN

The autophagy initiation complex is brought about via a highly ordered and stepwise assembly process. Two crucial signaling molecules, mTORC1 and AMPK, orchestrate this assembly by phosphorylating/dephosphorylating autophagy-related proteins. Activation of Atg1 followed by recruitment of both Atg9 vesicles and the PI3K complex I to the PAS (phagophore assembly site) are particularly crucial steps in its formation. Ypt1, a small Rab GTPase in yeast cells, also plays an essential role in the formation of the autophagy initiation complex through multiple regulatory pathways. In this review, our primary focus is to discuss how signaling molecules initiate the assembly of the autophagy initiation complex, and highlight the significant roles of Ypt1 in this process. We end by addressing issues that need future clarification.

Asunto(s)

Proteínas Relacionadas con la Autofagia , Autofagia , Diana Mecanicista del Complejo 1 de la Rapamicina , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Transducción de Señal , Proteínas de Unión al GTP rab , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas Relacionadas con la Autofagia/metabolismo , Proteínas Relacionadas con la Autofagia/genética , Proteínas de Unión al GTP rab/metabolismo , Diana Mecanicista del Complejo 1 de la Rapamicina/metabolismo , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Humanos , Animales , Proteínas Quinasas Activadas por AMP/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Complejos Multiproteicos/metabolismo

RESUMEN

Macroautophagy/autophagy is the major degradation pathway in neurons for eliminating damaged proteins and organelles in Parkinson disease (PD). Like neurons, glial cells are important contributors to PD, yet how autophagy is executed in glia and whether it is using similar interplay as in neurons or other tissues, remain largely elusive. Recently, we reported that the PD risk factor, GAK/aux (cyclin-G-associated kinase/auxilin), regulates the onset of glial autophagy. In the absence of GAK/aux, the number and size of the autophagosomes and autophagosomal precursors increase in adult fly glia and mouse microglia. The protein levels of components in the initiation and class III phosphatidylinositol 3-kinase (PtdIns3K) complexes are generally upregulated. GAK/aux interacts with the master initiation regulator ULK1/Atg1 (unc-51 like autophagy activating kinase 1) via its uncoating domain, hinders autophagy activation by competing with ATG13 (autophagy related 13) for binding to the ULK1 C terminus, and regulates ULK1 trafficking to phagophores. Nonetheless, lack of GAK/aux impairs the autophagic flux and blocks substrate degradation, suggesting that GAK/aux might play additional roles. Overall, our findings reveal a new regulator of autophagy initiation in glia, advancing our understanding on how glia contribute to PD in terms of eliminating pathological protein aggregates.Abbreviations: ATG13: autophagy related 13; GAK/aux: cyclin G associated kinase/auxilin; PtdIns3K: phosphatidylinositol 3-kinase; PD: Parkinson disease; ULK1/Atg1: unc-51 like autophagy activating kinase 1.

Asunto(s)

Autofagia , Enfermedad de Parkinson , Animales , Ratones , Homólogo de la Proteína 1 Relacionada con la Autofagia/metabolismo , Autofagia/fisiología , Proteínas Relacionadas con la Autofagia/metabolismo , Enfermedad de Parkinson/metabolismo , Auxilinas , Neuroglía/metabolismo

RESUMEN

Membrane vesiculation is an energy-costing process. Previous studies paid much attention to proteins with curvature-inducing motifs. Recent publications reveal that the liquid-like protein assembly on membrane surfaces provides an efficient yet structure-independent mechanism for increasing the membrane curvature, which plays important roles in vesicle transport in many aspects. Intrinsically disordered regions (IDRs) within the proteins are highly potent drivers of membrane curvature by providing large hydrodynamic radii to generate steric pressure. Biomolecular condensates formed by phase separation can provide a reaction platform for sequential processes or generate a wetting surface to sequestrate cargos and trigger membrane remodeling. We review the latest progress in yeast and mammalian cells, focus on the mechanism of clathrin-mediated endocytosis (CME) and autophagy initiation, and compare with what we know in model plant Arabidopsis. The comparison may give important insights into the understanding of basic membrane trafficking mechanisms in plant cells.

Asunto(s)

Arabidopsis , Animales , Saccharomyces cerevisiae , Endocitosis , Transporte Biológico , Mamíferos

RESUMEN

Autophagy is a conserved intracellular degradation pathway that generates de novo double-membrane autophagosomes to target a wide range of material for lysosomal degradation. In multicellular organisms, autophagy initiation requires the timely assembly of a contact site between the ER and the nascent autophagosome. Here, we report the in vitro reconstitution of a full-length seven-subunit human autophagy initiation supercomplex built on a core complex of ATG13-101 and ATG9. Assembly of this core complex requires the rare ability of ATG13 and ATG101 to switch between distinct folds. The slow spontaneous metamorphic conversion is rate limiting for the self-assembly of the supercomplex. The interaction of the core complex with ATG2-WIPI4 enhances tethering of membrane vesicles and accelerates lipid transfer of ATG2 by both ATG9 and ATG13-101. Our work uncovers the molecular basis of the contact site and its assembly mechanisms imposed by the metamorphosis of ATG13-101 to regulate autophagosome biogenesis in space and time.

Asunto(s)

Autofagosomas , Autofagia , Humanos , Proteínas Relacionadas con la Autofagia/genética , Proteínas Relacionadas con la Autofagia/metabolismo , Autofagia/fisiología , Autofagosomas/metabolismo , Proteínas de la Membrana/metabolismo , Lípidos

RESUMEN

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is closely related to various cellular aspects associated with autophagy. However, how SARS-CoV-2 mediates the subversion of the macroautophagy/autophagy pathway remains largely unclear. In this study, we demonstrate that overexpression of the SARS-CoV-2 ORF7a protein activates LC3-II and leads to the accumulation of autophagosomes in multiple cell lines, while knockdown of the viral ORF7a gene via shRNAs targeting ORF7a sgRNA during SARS-CoV-2 infection decreased autophagy levels. Mechanistically, the ORF7a protein initiates autophagy via the AKT-MTOR-ULK1-mediated pathway, but ORF7a limits the progression of autophagic flux by activating CASP3 (caspase 3) to cleave the SNAP29 protein at aspartic acid residue 30 (D30), ultimately impairing complete autophagy. Importantly, SARS-CoV-2 infection-induced accumulated autophagosomes promote progeny virus production, whereby ORF7a downregulates SNAP29, ultimately resulting in failure of autophagosome fusion with lysosomes to promote viral replication. Taken together, our study reveals a mechanism by which SARS-CoV-2 utilizes the autophagic machinery to facilitate its own propagation via ORF7a.Abbreviations: 3-MA: 3-methyladenine; ACE2: angiotensin converting enzyme 2; ACTB/ß-actin: actin beta; ATG7: autophagy related 7; Baf A1: bafilomycin A1; BECN1: beclin 1; CASP3: caspase 3; COVID-19: coronavirus disease 2019; GFP: green fluorescent protein; hpi: hour post-infection; hpt: hour post-transfection; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MERS: Middle East respiratory syndrome; MTOR: mechanistic target of rapamycin kinase; ORF: open reading frame; PARP: poly(ADP-ribose) polymerase; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2; shRNAs: short hairpin RNAs; siRNA: small interfering RNA; SNAP29: synaptosome associated protein 29; SQSTM1/p62: sequestosome 1; STX17: syntaxin 17; TCID50: tissue culture infectious dose; TEM: transmission electron microscopy; TUBB, tubulin, beta; ULK1: unc-51 like autophagy activating kinase 1.

Asunto(s)

Autofagia , COVID-19 , Humanos , Autofagosomas/metabolismo , Autofagia/genética , Caspasa 3/metabolismo , Lisosomas/metabolismo , Macroautofagia , Proteínas Qb-SNARE/metabolismo , Proteínas Qc-SNARE , SARS-CoV-2 , Serina-Treonina Quinasas TOR/metabolismo , Replicación Viral

RESUMEN

Epidermal growth factor receptor (EGFR) plays critical roles in cell proliferation and tumorigenesis. Autophagy has emerged as a potential mechanism involved in the acquired resistance to anti-EGFR treatments, however, the molecular mechanisms has not been fully addressed. In this study, we identified EGFR interacts with STYK1, a positive autophagy regulator, in EGFR kinase activity dependent manner. We found that EGFR phosphorylates STYK1 at Y356 site and STYK1 inhibits activated EGFR mediated Beclin1 tyrosine phosphorylation and interaction between Bcl2 and Beclin1, thus enhances PtdIns3K-C1 complex assembly and autophagy initiation. We also demonstrated that STYK1 depletion increased the sensitivity of NSCLC cells to EGFR-TKIs in vitro and in vivo. Moreover, EGFR-TKIs induced activation of AMPK phosphorylates STYK1 at S304 site. STYK1 S304 collaborated with Y356 phosphorylation to enhance the EGFR-STYK1 interaction and reverse the inhibitory effects of EGFR to autophagy flux. Collectively, these data revealed new roles and cross-talk between STYK1 and EGFR in autophagy regulation and EGFR-TKIs sensitivity in NSCLC.

RESUMEN

ObjectiveTo observe the effects of Qingzao Jiufeitang on the expression of adenosine 5′-monophosphate （AMP）-activated protein kinase （AMPK）， mammalian target of rapamycin （mTOR）， and UNC-51-like kinase 1 （ULK1） in lung cancer cells after the application of AMPK inhibitor （compound C）. MethodMale C57BL/6J mice were randomly divided into a model group， a cyclophosphamide （CTX） group （50 mg·kg-1）， a Qingzao Jiufeitang group （11 g·kg-1）， an AMPK inhibitor group （10 mg·kg-1）， and a Qingzao Jiufeitang combined with AMPK inhibitor group （combination group） （11 g·kg-1+10 mg·kg-1）. Lewis lung cancer cells were subcutaneously injected into the right axilla to induce a tumor-bearing model. 24 hours after modeling， the mice in the CTX group were intraperitoneally injected once every other day for seven times in total. The mice in the AMPK inhibitor group and the combination group received intraperitoneal injection of compound C， once a day for 14 days. The mice in the Qingzao Jiufeitang group and the combination group were administered orally at the set dose for 14 days before and after modeling. At the end of the experiment， the mice in each group were sacrificed. The tumor-bearing tissues were collected， and the tumor weight of each group was counted. Transmission electron microscopy （TEM） was used to observe the formation of autolysosomes in lung cancer tissues of each group. Western blot was used to detect the protein expression of AMPK， phosphorylated AMPK （p-AMPK）， mTOR， phosphorylated mTOR （p-mTOR）， ULK1， phosphorylated ULK1 （p-ULK1）， microtubule-associated protein 1 light chain 3B （LC3B）， and p62. Hematoxylin-eosin （HE） staining was used to observe the pathological changes of lung cancer in each group. ResultCompared with the model group， the Qingzao Jiufeitang group showed decreased tumor weight （P<0.01）， the formation of autolysosomes under the electron microscope， increased protein expression of p-AMPK， p-ULK1， LC3B， LC3B-Ⅱ， and p-AMPK/AMPK， p-ULK1/ULK1， and LC3B-Ⅱ/LC3B-Ⅰratios （P<0.01， P<0.05）， and reduced protein expression of p-mTOR， p62， and p-mTOR/mTOR ratio （P<0.05）. Compared with the Qingzao Jiufeitang group， the combination group showed no autolysosomes formation under the electron microscope， decreased protein expression of p-AMPK， p-ULK1， LC3B， LC3B-Ⅱ， and p-AMPK/AMPK， p-ULK1/ULK1， LC3B-Ⅱ/LC3B-Ⅰ ratios （P<0.05， P<0.01）， and increased p62 protein expression （P<0.05）. HE staining results showed that the pathological changes of lung cancer tissues in the groups with drug intervention were improved compared with those in the model group. ConclusionQingzao Jiufeitang can promote the elevation of LC3B-Ⅱ and decrease the expression of p62 protein， thus inducing autophagy. The mechanism of autophagy initiation may be achieved by the AMPK/ULK1 pathway instead of the mediation by the AMPK/mTOR/ULK1 pathway.

RESUMEN

VCP, a conserved ATPase, is involved in several cellular processes, and mutations in this protein are associated with various diseases. VCP also plays a role in autophagosome maturation. However, because a deficiency in autophagosome maturation presents a readily observable phenotype, other roles of VCP in autophagy regulation, in particular in the initial steps of autophagosome formation, may have been overlooked. In a recently published paper, using small-molecule inhibitors, Hill et al. showed that VCP regulates autophagy initiation through both stabilization of BECN1 and enhancement of phosphati-dylinositol 3-kinase (PtdIns3K) complex assembly.

Asunto(s)

Autofagia/fisiología , Beclina-1/metabolismo , Proteína que Contiene Valosina/metabolismo , Adenosina Trifosfatasas/metabolismo , Fosfatidilinositol 3-Quinasas Clase III/metabolismo , Humanos

RESUMEN

VCP/p97 is an essential multifunctional protein implicated in a plethora of intracellular quality control systems, and abnormal function of VCP is the underlying cause of several neurodegenerative disorders. We reported that VCP regulates the levels of the macroautophagy/autophagy-inducing lipid phosphatidylinositol-3-phosphate (PtdIns3P) by modulating the activity of the BECN1 (beclin 1)-containing phosphatidylinositol 3-kinase (PtdIns3K) complex. VCP stimulates the deubiquitinase activity of ATXN3 (ataxin 3) to stabilize BECN1 protein levels and also interacts with and promotes the assembly and kinase activity of the PtdIns3K complex. Acute inhibition of VCP activity impairs autophagy induction, demonstrated by a diminished PtdIns3P production and decreased recruitment of early autophagy markers WIPI2 and ATG16L1. Thus, VCP promotes autophagosome biogenesis, in addition to its previously described role in autophagosome maturation.

Asunto(s)

Autofagia , Fosfatos de Fosfatidilinositol , Beclina-1

RESUMEN

The endoplasmic reticulum (ER) stress response and autophagy are important cellular responses that determine cell fate and whose dysregulation is implicated in the perturbation of homeostasis and diseases. Tonicity-responsive enhancer-binding protein (TonEBP, also called NFAT5) is a pleiotropic stress protein that mediates both protective and pathological cellular responses. Here, we examined the role of TonEBP in ß-cell survival under ER stress. We found that TonEBP increases ß-cell survival under ER stress by enhancing autophagy. The level of TonEBP protein increased under ER stress due to a reduction in its degradation via the ubiquitin-proteasome pathway. In response to ER stress, TonEBP increased autophagosome formations and suppressed the accumulation of protein aggregates and ß-cell death. The Rel-homology domain of TonEBP interacted with FIP200, which is essential for the initiation of autophagy, and was required for autophagy and cell survival upon exposure to ER stress. Mice in which TonEBP was specifically deleted in pancreatic endocrine progenitor cells exhibited defective glucose homeostasis and a loss of islet mass. Taken together, these findings demonstrate that TonEBP protects against ER stress-induced ß-cell death by enhancing autophagy.

Asunto(s)

Estrés del Retículo Endoplásmico/fisiología , Factores de Transcripción NFATC/metabolismo , Autofagia , Supervivencia Celular , Humanos

RESUMEN

Etoposide-induced protein 2.4 (EI24), located on the endoplasmic reticulum (ER) membrane, has been proposed to be an essential autophagy protein. Specific ablation of EI24 in neuronal and liver tissues causes deficiency of autophagy flux. However, the molecular mechanism of the EI24-mediated autophagy process is still poorly understood. Like neurons and hepatic cells, pancreatic ß cells are also secretory cells. Pancreatic ß cells contain large amounts of ER and continuously synthesize and secrete insulin to maintain blood glucose homeostasis. Yet, the effect of EI24 on autophagy of pancreatic ß cells has not been reported. Here, we show that the autophagy process is inhibited in EI24-deficient primary pancreatic ß cells. Further mechanistic studies demonstrate that EI24 is enriched at the ER-mitochondria interface and that the C-terminal domain of EI24 is important for the integrity of the mitochondria-associated membrane (MAM) and autophagy flux. Overexpression of EI24, but not the EI24-ΔC mutant, can rescue MAM integrity and decrease the aggregation of p62 and LC3II in the EI24-deficient group. By mass spectrometry-based proteomics following immunoprecipitation, EI24 was found to interact with voltage-dependent anion channel 1 (VDAC1), inositol 1,4,5-trisphosphate receptor (IP3R), and the outer mitochondrial membrane chaperone GRP75. Knockout of EI24 impairs the interaction of IP3R with VDAC1, indicating that these proteins may form a quaternary complex to regulate MAM integrity and the autophagy process.

Asunto(s)

Proteínas Reguladoras de la Apoptosis/metabolismo , Autofagia , Retículo Endoplásmico/metabolismo , Células Secretoras de Insulina/metabolismo , Mitocondrias/metabolismo , Proteínas Nucleares/metabolismo , Animales , Proteínas Reguladoras de la Apoptosis/genética , Sistemas CRISPR-Cas , Células Cultivadas , Femenino , Células HEK293 , Humanos , Células Secretoras de Insulina/citología , Masculino , Ratones , Proteínas Nucleares/genética , Canal Aniónico 1 Dependiente del Voltaje/metabolismo

RESUMEN

Autophagy is a process of self-degradation that enables the cell to survive when faced with starvation or stressful conditions. The mechanistic target of rapamycin (mTOR), also known as the mammalian target of rapamycin, plays a critical role in maintaining a balance between cellular anabolism and catabolism. mTOR complex 1 (mTORC1) was unveiled as a master regulator of autophagy since inhibition of mTORC1 was required to initiate the autophagy process. Evidence has emerged in recent years to indicate that mTORC1 also directly regulates the subsequent steps of the autophagy process, including the nucleation, autophagosome elongation, autophagosome maturation and termination. By phosphorylating select protein targets of the autophagy core machinery and/or their regulators, mTORC1 can alter their functions, increase their proteasomal degradation or modulate their acetylation status, which is a key switch of the autophagy process. Moreover, it phosphorylates and alters the subcellular localization of transcription factors to suppress the expression of genes needed for autophagosome formation and lysosome biogenesis. The purpose of this review article is to critically analyze current literatures to provide an integrated view of how mTORC1 regulates various steps of the autophagy process.

RESUMEN

Three-dimensional (3D) models are acquiring importance in cancer research due to their ability to mimic multiple features of the tumor microenvironment more accurately than standard monolayer two-dimensional (2D) cultures. Several groups, including our laboratory, are now accumulating evidence that autophagy in solid tumors is also better represented in 3D than in 2D. Here we detail how we generate 3D models, both in vitro multicellular spheroids generated from cell lines and ex vivo tumor fragment spheroids generated from tumor samples, and how autophagy can be measured in 3D cultures.

Asunto(s)

Autofagia/fisiología , Técnicas de Cultivo de Célula/métodos , Mesotelioma/patología , Esferoides Celulares/patología , Proteínas Adaptadoras Transductoras de Señales/análisis , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Relacionadas con la Autofagia/análisis , Proteínas Relacionadas con la Autofagia/metabolismo , Técnicas de Cultivo de Célula/instrumentación , Línea Celular Tumoral , Humanos , Microscopía Fluorescente/instrumentación , Microscopía Fluorescente/métodos , Proteínas Asociadas a Microtúbulos/análisis , Proteínas Asociadas a Microtúbulos/metabolismo , Tubulina (Proteína)/análisis , Tubulina (Proteína)/metabolismo

RESUMEN

Unc-51-like-kinase 1 (ULK1) is a target of both the mechanistic target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK), whose role is to facilitate the initiation of autophagy in response to starvation. Upon glucose starvation, dissociation of mTOR from ULK1 and phosphorylation by AMPK leads to the activation of ULK1 activity. Here, we provide evidence that ULK1 is the attachment of O-linked N-acetylglucosamine (O-GlcNAcylated) on the threonine 754 site by O-linked N-acetylglucosamine transferase (OGT) upon glucose starvation. ULK1 O-GlcNAcylation occurs after dephosphorylation of adjacent mTOR-dependent phosphorylation on the serine 757 site by protein phosphatase 1 (PP1) and phosphorylation by AMPK. ULK1 O-GlcNAcylation is crucial for binding and phosphorylation of ATG14L, allowing the activation of lipid kinase VPS34 and leading to the production of phosphatidylinositol-(3)-phosphate (PI(3)P), which is required for phagophore formation and initiation of autophagy. Our findings provide insights into the crosstalk between dephosphorylation and O-GlcNAcylation during autophagy and specify a molecular framework for potential therapeutic intervention in autophagy-related diseases.

Asunto(s)

Proteínas Adaptadoras del Transporte Vesicular/metabolismo , Homólogo de la Proteína 1 Relacionada con la Autofagia/metabolismo , Proteínas Relacionadas con la Autofagia/metabolismo , Autofagia , Fosfatidilinositol 3-Quinasas Clase III/metabolismo , Glucosamina/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Quinasas Activadas por AMP/metabolismo , Secuencia de Aminoácidos , Autofagosomas/metabolismo , Línea Celular , Glucosa/deficiencia , Glicosilación , Humanos , N-Acetilglucosaminiltransferasas/metabolismo , Fosforilación , Treonina/metabolismo

RESUMEN

Cryptococcus neoformans (Cn) is a deadly fungal pathogen whose intracellular lifestyle is important for virulence. Host mechanisms controlling fungal phagocytosis and replication remain obscure. Here, we perform a global phosphoproteomic analysis of the host response to Cryptococcus infection. Our analysis reveals numerous and diverse host proteins that are differentially phosphorylated following fungal ingestion by macrophages, thereby indicating global reprogramming of host kinase signaling. Notably, phagocytosis of the pathogen activates the host autophagy initiation complex (AIC) and the upstream regulatory components LKB1 and AMPKα, which regulate autophagy induction through their kinase activities. Deletion of Prkaa1, the gene encoding AMPKα1, in monocytes results in resistance to fungal colonization of mice. Finally, the recruitment of AIC components to nascent Cryptococcus-containing vacuoles (CnCVs) regulates the intracellular trafficking and replication of the pathogen. These findings demonstrate that host AIC regulatory networks confer susceptibility to infection and establish a proteomic resource for elucidating host mechanisms that regulate fungal intracellular parasitism.

Asunto(s)

Criptococosis/inmunología , Cryptococcus neoformans/genética , Cryptococcus neoformans/patogenicidad , Interacciones Huésped-Patógeno/inmunología , Transducción de Señal/fisiología , Virulencia/genética , Proteínas Quinasas Activadas por AMP/genética , Proteínas Quinasas Activadas por AMP/metabolismo , Animales , Proteínas Reguladoras de la Apoptosis/metabolismo , Autofagia/fisiología , Homólogo de la Proteína 1 Relacionada con la Autofagia/genética , Homólogo de la Proteína 1 Relacionada con la Autofagia/metabolismo , Transporte Biológico/fisiología , Línea Celular , Coxiella burnetii/patogenicidad , Criptococosis/microbiología , Cryptococcus neoformans/crecimiento & desarrollo , Cryptococcus neoformans/metabolismo , Modelos Animales de Enfermedad , Femenino , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Interacciones Huésped-Patógeno/genética , Interacciones Huésped-Patógeno/fisiología , Macrófagos/inmunología , Macrófagos/metabolismo , Macrófagos/microbiología , Ratones , Ratones Endogámicos C57BL , Monocitos/metabolismo , Fagocitosis , Proteínas Serina-Treonina Quinasas/metabolismo , Proteómica , Células RAW 264.7 , Vacuolas/microbiología , Virulencia/fisiología

RESUMEN

Understanding the role of autophagy in cancer has been limited by the inability to measure this dynamic process in formalin-fixed tissue. We considered that 3-dimensional models including ex vivo tumor, such as we have developed for studying mesothelioma, would provide valuable insights. Using these models, in which we could use lysosomal inhibitors to measure the autophagic flux, we sought a marker of autophagy that would be valid in formalin-fixed tumor and be used to assess the role of autophagy in patient outcome. Autophagy was studied in mesothelioma cell lines, as 2-dimensional (2D) monolayers and 3-dimensional (3D) multicellular spheroids (MCS), and in tumor from 25 chemonaive patients, both as ex vivo 3D tumor fragment spheroids (TFS) and as formalin-fixed tissue. Autophagy was evaluated as autophagic flux by detection of the accumulation of LC3 after lysosomal inhibition and as autophagy initiation by detection of ATG13 puncta. We found that autophagic flux in 3D, but not in 2D, correlated with ATG13 positivity. In each TFS, ATG13 positivity was similar to that of the original tumor. When tested in tissue microarrays of 109 chemonaive patients, higher ATG13 positivity correlated with better prognosis and provided information independent of known prognostic factors. Our results show that ATG13 is a static marker of the autophagic flux in 3D models of mesothelioma and may also reflect autophagy levels in formalin-fixed tumor. If confirmed, this marker would represent a novel prognostic factor for mesothelioma, supporting the notion that autophagy plays an important role in this cancer.

Asunto(s)

Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Relacionadas con la Autofagia/metabolismo , Autofagia/fisiología , Mesotelioma/metabolismo , Mesotelioma/terapia , Animales , Técnicas de Cultivo de Célula , Línea Celular , Formaldehído , Humanos , Resultado del Tratamiento

RESUMEN

The Atg1/ULK complex functions as the most upstream factor among Atg proteins to initiate autophagy. ATG101 is a constitutive component of the Atg1/ULK complex in most eukaryotes except for budding yeast, and plays an essential role in autophagy; however, the structure and functions of ATG101 were largely unknown. Recently, we determined the crystal structure of fission yeast Atg101 in complex with the closed HORMA domain of Atg13, revealing that Atg101 is also a HORMA protein with an open conformation. These 2 HORMA proteins play essential roles in autophagy initiation through recruiting downstream factors to the autophagosome formation site.