scholarly journals Downregulation of autophagy by Met30-mediated Atg9 ubiquitination

2020 ◽  
Vol 118 (1) ◽  
pp. e2005539118
Author(s):  
Yuchen Feng ◽  
Aileen R. Ariosa ◽  
Ying Yang ◽  
Zehan Hu ◽  
Jörn Dengjel ◽  
...  
Keyword(s):  
Posttranslational Modification ◽  
Stress Conditions ◽  
Nutrient Deprivation ◽  
Dependent Manner ◽  
Autophagy Flux ◽  
Cellular Homeostasis ◽  
Molecular Process ◽  
Additional Layer ◽  
Response To Stress ◽  
Multiple Stages

Macroautophagy/autophagy is a highly conserved eukaryotic molecular process that facilitates the recycling of superfluous cytoplasmic materials, damaged organelles, and invading pathogens, resulting in proper cellular homeostasis and survival during stress conditions. Autophagy is stringently regulated at multiple stages, including control at transcriptional, translational, and posttranslational levels. In this work, we identified a mechanism by which regulation of autophagy is achieved through the posttranslational modification of Atg9. Here, we show that, in order to limit autophagy to a low, basal level during normal conditions, Atg9 is ubiquitinated and subsequently targeted for degradation in a proteasome-dependent manner through the action of the E3 ligase Met30. When cells require increased autophagy flux to respond to nutrient deprivation, the proteolysis of Atg9 is significantly reduced. Overall, this work reveals an additional layer of mechanistic regulation that allows cells to further maintain appropriate levels of autophagy and to rapidly induce this process in response to stress.

scholarly journals Dichotomous roles of TGF-β in human cancer

2016 ◽  
Vol 44 (5) ◽  
pp. 1441-1454 ◽  
Author(s):  
Jennifer J. Huang ◽  
Gerard C. Blobe
Keyword(s):  
Signaling Pathway ◽  
Cancer Progression ◽  
Transforming Growth Factor ◽  
Human Cancer ◽  
Transforming Growth Factor Β ◽  
Dependent Manner ◽  
Biological Processes ◽  
Cellular Homeostasis ◽  
Angiogenic Therapy ◽  
Promising Strategy

Transforming growth factor-β (TGF-β) mediates numerous biological processes, including embryonic development and the maintenance of cellular homeostasis in a context-dependent manner. Consistent with its central role in maintaining cellular homeostasis, inhibition of TGF-β signaling results in disruption of normal homeostatic processes and subsequent carcinogenesis, defining the TGF-β signaling pathway as a tumor suppressor. However, once carcinogenesis is initiated, the TGF-β signaling pathway promotes cancer progression. This dichotomous function of the TGF-β signaling pathway is mediated through altering effects on both the cancer cells, by inducing apoptosis and inhibiting proliferation, and the tumor microenvironment, by promoting angiogenesis and inhibiting immunosurveillance. Current studies support inhibition of TGF-β signaling either alone, or in conjunction with anti-angiogenic therapy or immunotherapy as a promising strategy for the treatment of human cancers.

Thermal and Starvation Stress Response of Escherichia coli O157:H7 Isolates Selected from Agricultural Environments

2016 ◽  
Vol 79 (10) ◽  
pp. 1673-1679 ◽  
Author(s):  
ACHYUT ADHIKARI ◽  
ANDY BARY ◽  
CRAIG COGGER ◽  
CALEB JAMES ◽  
GÜLHAN ÜNLÜ ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Heat Stress ◽  
Stress Response ◽  
Weibull Model ◽  
Stress Conditions ◽  
Inactivation Kinetics ◽  
Escherichia Coli O157 ◽  
Starvation Stress ◽  
E Coli ◽  
Response To Stress

ABSTRACT Pathogens exposed to agricultural production environments are subject to multiple stresses that may alter their survival under subsequent stress conditions. The objective of this study was to examine heat and starvation stress response of Escherichia coli O157:H7 strains isolated from agricultural matrices. Seven E. coli O157:H7 isolates from different agricultural matrices—soil, compost, irrigation water, and sheep manure—were selected, and two ATCC strains were used as controls. The E. coli O157:H7 isolates were exposed to heat stress (56°C in 0.1% peptone water for up to 1 h) and starvation (in phosphate-buffered saline at 37°C for 15 days), and their survival was examined. GInaFiT freeware tool was used to perform regression analyses of the surviving populations. The Weibull model was identified as the most appropriate model for response of the isolates to heat stress, whereas the biphasic survival curves during starvation were fitted using the double Weibull model, indicating the adaptation to starvation or a resistant subpopulation. The inactivation time during heating to achieve the first decimal reduction time (δ) calculated with the Weibull parameters was the highest (45 min) for a compost isolate (Comp60A) and the lowest (28 min) for ATCC strain 43895. Two of the nine isolates (ATCC 43895 and a manure isolate) had β < 1, indicating that surviving populations adapted to heat stress, and six strains demonstrated downward concavity (β > 1), indicating decreasing heat resistance over time. The ATCC strains displayed the longest δ2 (>1,250 h) in response to starvation stress, compared with from 328 to 812 h for the environmental strains. The considerable variation in inactivation kinetics of E. coli O157:H7 highlights the importance of evaluating response to stress conditions among individual strains of a specific pathogen. Environmental isolates did not exhibit more robust response to stress conditions in this study compared with ATCC strains.

scholarly journals Bioenergetic and autophagic control by Sirt3 in response to nutrient deprivation in mouse embryonic fibroblasts

2013 ◽  
Vol 454 (2) ◽  
pp. 249-257 ◽  
Author(s):  
Qiuli Liang ◽  
Gloria A. Benavides ◽  
Athanassios Vassilopoulos ◽  
David Gius ◽  
Victor Darley-Usmar ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Survival ◽  
Mitochondrial Respiration ◽  
Energy Demand ◽  
Mammalian Target Of Rapamycin ◽  
Protective Role ◽  
Nutrient Deprivation ◽  
Autophagy Flux ◽  
Jnk Pathway ◽  
Mouse Muscle

Sirt3 (sirtuin 3) is an NAD-dependent deacetylase localized to mitochondria. Sirt3 expression is increased in mouse muscle and liver by starvation, which could protect against the starvation-dependent increase in oxidative stress and protein damage. Damaged proteins and organelles depend on autophagy for removal and this is critical for cell survival, but the role of Sirt3 is unclear. To examine this, we used Sirt3-KO (knockout) mouse embryonic fibroblast cells, and found that, under basal conditions, Sirt3-KO cells exhibited increased autophagy flux compared with WT (wild-type) cells. In response to nutrient deprivation, both WT and KO cells exhibited increased basal and ATP-linked mitochondrial respiration, indicating an increased energy demand. Both cells exhibited lower levels of phosphorylated mTOR (mammalian target of rapamycin) and higher autophagy flux, with KO cells exhibiting lower maximal mitochondrial respiration and reserve capacity, and higher levels of autophagy than WT cells. KO cells exhibit higher phospho-JNK (c-Jun N-terminal kinase) and phospho-c-Jun than WT cells under starvation conditions. However, inhibition of JNK activity in Sirt3-KO cells did not affect LC3-I (light chain 3-I) and LC3-II levels, indicating that Sirt3-regulated autophagy is independent of the JNK pathway. Caspase 3 activation and cell death are significantly higher in Sirt3-KO cells compared with WT cells in response to nutrient deprivation. Inhibition of autophagy by chloroquine exacerbated cell death in both WT and Sirt3-KO cells, and by 3-methyadenine exacerbated cell death in Sirt3-KO cells. These data suggest that nutrient deprivation-induced autophagy plays a protective role in cell survival, and Sirt3 decreases the requirement for enhanced autophagy and improves cellular bioenergetics.

scholarly journals Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis

2021 ◽  
Vol 22 (19) ◽  
pp. 10772
Author(s):  
Chang Ho Kang ◽  
Eun Seon Lee ◽  
Ganesh M. Nawkar ◽  
Joung Hun Park ◽  
Seong Dong Wi ◽  
...  
Keyword(s):  
Stress Response ◽  
Er Stress ◽  
Stress Conditions ◽  
Negative Regulator ◽  
Light Signaling ◽  
Dependent Manner ◽  
Wild Type ◽  
Er Stress Response ◽  
The Unfolded Protein Response ◽  
Mutant Locus

Interaction between light signaling and stress response has been recently reported in plants. Here, we investigated the role of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a key regulator of light signaling, in endoplasmic reticulum (ER) stress response in Arabidopsis. The cop1-4 mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm). Interestingly, the abundance of nuclear-localized COP1 increased under ER stress conditions. Complementation of cop1-4 mutant plants with the wild-type or variant types of COP1 revealed that the nuclear localization and dimerization of COP1 are essential for its function in plant ER stress response. Moreover, the protein amount of ELONGATED HYPOCOTYL 5 (HY5), which inhibits bZIP28 to activate the unfolded protein response (UPR), decreased under ER stress conditions in a COP1-dependent manner. Accordingly, the binding of bZIP28 to the BIP3 promoter was reduced in cop1-4 plants and increased in hy5 plants compared with the wild type. Furthermore, introduction of the hy5 mutant locus into the cop1-4 mutant background rescued its ER stress-sensitive phenotype. Altogether, our results suggest that COP1, a negative regulator of light signaling, positively controls ER stress response by partially degrading HY5 in the nucleus.

scholarly journals Autophagy Modulation in Mammarenavirus Infection

2020 ◽  
Vol 4 (4) ◽  
pp. 45-51
Author(s):  
Giovanna Gallo ◽  
Julieta Roldán ◽  
Laura Delgui
Keyword(s):  
Public Health ◽  
High Mortality ◽  
Metabolic Pathway ◽  
New World ◽  
Stress Conditions ◽  
Health Concern ◽  
Public Health Concern ◽  
Cellular Homeostasis ◽  
Old World ◽  
Mortality And Morbidity

Mammarenavirus genus groups viruses causing human haemorrhagic diseases, including the New World (NW) Junín virus (JUNV), and the Old World (OW) viruses Lassa (LASV), among others. The high mortality and morbidity rates associated to pathogenic mammarenaviruses, the absence of vaccines and the constant threat of new emerging species, make these viruses a public health concern in endemic areas. Autophagy is a widely-known intracellular metabolic pathway involved in maintaining the cellular homeostasis in response to several stress conditions.

Programmed Cell Death in Plants: Insights Into developmental and Stress-Induced Cell Death

2021 ◽  
Vol 22 ◽  
Author(s):  
Heba T. Ebeed ◽  
Ahmed A. El-helely
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Plant Development ◽  
Molecular Basis ◽  
Stress Conditions ◽  
Similar Form ◽  
Cellular Homeostasis ◽  
Endogenous Factors ◽  
Selective Elimination

: Programmed cell death (PCD) is a fundamental genetically controlled process in most organisms. PCD is responsible for the selective elimination of damaged or unwanted cells and organs to maintain cellular homeostasis during the organ’s development under normal conditions as well as during defense or adaptation to stressful conditions. PCD pathways have been extensively studied in animals. In plants, studies focusing on understanding the pathways of PCD have advanced significantly. However, the knowledge about the molecular basis of PCD is still very limited. Some PCD pathways that have been discovered in animals are not present in plants or found with a similar form. PCD in plants is developmentally controlled (by endogenous factors) to function in organ development and differentiations as well as environmentally induced (by exogenous stimuli) to help the plant in surviving under stress conditions. Here, we present a review of the role of PCD in plant development and explore different examples of stress-induced PCD as well as highlight the main differences between the plant and animal PCD.

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