GSK3B induces autophagy by phosphorylating ULK1.
Experimental & molecular medicine
Unc-51-like autophagy activating kinase 1 (ULK1), a mammalian homolog of the yeast kinase Atg1, has an essential role in autophagy induction. In nutrient and growth factor signaling, ULK1 activity is regulated by various posttranslational modifications, including phosphorylation, acetylation, and ubiquitination. We previously identified glycogen synthase kinase 3 beta (GSK3B) as an upstream regulator of insulin withdrawal-induced autophagy in adult hippocampal neural stem cells. Here, we report that following insulin withdrawal, GSK3B directly interacted with and activated ULK1 via phosphorylation of S405 and S415 within the GABARAP-interacting region. Phosphorylation of these residues facilitated the interaction of ULK1 with MAP1LC3B and GABARAPL1, while phosphorylation-defective mutants of ULK1 failed to do so and could not induce autophagy flux. Furthermore, high phosphorylation levels of ULK1 at S405 and S415 were observed in human pancreatic cancer cell lines, all of which are known to exhibit high levels of autophagy. Our results reveal the importance of GSK3B-mediated phosphorylation for ULK1 regulation and autophagy induction and potentially for tumorigenesis.
10.1038/s12276-021-00570-6
Autophagy and inflammation in ischemic stroke.
Mo Yun,Sun Yin-Yi,Liu Kang-Yong
Neural regeneration research
Appropriate autophagy has protective effects on ischemic nerve tissue, while excessive autophagy may cause cell death. The inflammatory response plays an important role in the survival of nerve cells and the recovery of neural tissue after ischemia. Many studies have found an interaction between autophagy and inflammation in the pathogenesis of ischemic stroke. This study outlines recent advances regarding the role of autophagy in the post-stroke inflammatory response as follows. (1) Autophagy inhibits inflammatory responses caused by ischemic stimulation through mTOR, the AMPK pathway, and inhibition of inflammasome activation. (2) Activation of inflammation triggers the formation of autophagosomes, and the upregulation of autophagy levels is marked by a significant increase in the autophagy-forming markers LC3-II and Beclin-1. Lipopolysaccharide stimulates microglia and inhibits ULK1 activity by direct phosphorylation of p38 MAPK, reducing the flux and autophagy level, thereby inducing inflammatory activity. (3) By blocking the activation of autophagy, the activation of inflammasomes can alleviate cerebral ischemic injury. Autophagy can also regulate the phenotypic alternation of microglia through the nuclear factor-κB pathway, which is beneficial to the recovery of neural tissue after ischemia. Studies have shown that some drugs such as resveratrol can exert neuroprotective effects by regulating the autophagy-inflammatory pathway. These studies suggest that the autophagy-inflammatory pathway may provide a new direction for the treatment of ischemic stroke.
10.4103/1673-5374.274331
p53/microRNA-214/ULK1 axis impairs renal tubular autophagy in diabetic kidney disease.
The Journal of clinical investigation
Dysregulation of autophagy in diabetic kidney disease (DKD) has been reported, but the underlying mechanism and its pathogenic role remain elusive. We show that autophagy was inhibited in DKD models and in human diabetic kidneys. Ablation of autophagy-related gene 7 (Atg7) from kidney proximal tubules led to autophagy deficiency and worse renal hypertrophy, tubular damage, inflammation, fibrosis, and albuminuria in diabetic mice, indicating a protective role of autophagy in DKD. Autophagy impairment in DKD was associated with the downregulation of unc-51-like autophagy-activating kinase 1 (ULK1), which was mediated by the upregulation of microRNA-214 (miR-214) in diabetic kidney cells and tissues. Ablation of miR-214 from kidney proximal tubules prevented a decrease in ULK1 expression and autophagy impairment in diabetic kidneys, resulting in less renal hypertrophy and albuminuria. Furthermore, blockade of p53 attenuated miR-214 induction in DKD, leading to higher levels of ULK1 and autophagy, accompanied by an amelioration of DKD. Compared with nondiabetic samples, renal biopsies from patients with diabetes showed induction of p53 and miR-214, associated with downregulation of ULK1 and autophagy. We found a positive correlation between p53/miR-214 and renal fibrosis, but a negative correlation between ULK1/LC3 and renal fibrosis in patients with diabetes. Together, these results identify the p53/miR-214/ULK1 axis in autophagy impairment in diabetic kidneys, pinpointing possible therapeutic targets for DKD.
10.1172/JCI135536
MAPK1/3 kinase-dependent ULK1 degradation attenuates mitophagy and promotes breast cancer bone metastasis.
Autophagy
The function of mitophagy in cancer is controversial. ULK1 is critical for induction of macroautophagy/autophagy and has a more specific role in mitophagy in response to hypoxia. Here, we show that ULK1 deficiency induces an invasive phenotype of breast cancer cells under hypoxia and increases osteolytic bone metastasis. Mechanistically, ULK1 depletion attenuates mitophagy ability during hypoxia. As a result, the accumulation of damaged, ROS-generating mitochondria leads to activation of the NLRP3 inflammasome, which induces abnormal soluble cytokines secretion, then promotes the differentiation and maturation of osteoclasts, and ultimately results in bone metastasis. Notably, phosphorylation of ULK1 by MAPK1/ERK2-MAPK3/ERK1 kinase triggers its interaction with BTRC and subsequent K48-linked ubiquitination and proteasome degradation. Also, a clearly negative correlation between the expression levels of ULK1 and p-MAPK1/3 was observed in human breast cancer tissues. The MAP2K/MEK inhibitor trametinib is sufficient to restore mitophagy function via upregulation of ULK1, leading to inhibition of NLRP3 inflammasome activation, thereby reduces bone metastasis. These results indicate that knockout-mediated mitophagy defect promotes breast cancer bone metastasis and provide evidence to explore MAP2K/MEK- MAPK1/3 pathway inhibitors for therapy, especially in cancers displaying low levels of ULK1. ATG: autophagy-related; Baf A1: bafilomycin A; BTRC/β-TrCP: beta-transducin repeat containing E3 ubiquitin protein ligase; CHX: cycloheximide; CM: conditioned media; FBXW7/FBW7: F-box and WD repeat domain containing 7; MAPK1: mitogen-activated protein kinase 1; MTDR: MitoTracker Deep Red; mtROS: mitochondrial reactive oxygen species; microCT: micro-computed tomography; mtROS: mitochondrial reactive oxygen species; OCR: oxygen consumption rate; SQSTM1: sequestosome 1; ACP5/TRAP: acid phosphatase, tartrate resistant; ULK1: unc-51 like autophagy activating kinase 1.
10.1080/15548627.2020.1850609
High-fat diet induces cognitive impairment through repression of SIRT1/AMPK-mediated autophagy.
Experimental neurology
AIMS:Recent evidence suggests an association between a high-fat diet (HFD) and cognitive decline. HFD may reduce synaptic plasticity and cause tau hyperphosphorylation, but the mechanisms involved remain unclear. The purpose of this study was to explore whether Sirtuin1 (SIRT1)/AMP-activated protein kinase (AMPK) pathway was involved in this pathogenic effect in the HFD exposed mice. METHODS:C57BL/6 mice at 12 months of age were fed a standard (9% kcal fat) or high-fat (60% kcal fat) diet for 22 weeks, and Neuro-2a (N2a) cells were treated with normal culture medium or a palmitic acid (PA) medium (100uM) for 40 h. After that, cognitive function was tested by Morris water maze (MWM). The levels of proteins involved in SIRT1/AMPK pathway and autophagy were measured using western blotting and immunofluorescence. We also assessed the phosphorylation of tau protein and synapse. RESULTS:The mice presented impaired learning and memory abilities. We further found decreased levels of synaptophysin (Syn) and brain-derived neurotrophic factor (BDNF), increased tau46 and phosphorylated tau protein, and damaged neurons in mice after HFD or in N2a cells treated with PA medium. Moreover, HFD can also reduce the expression of SIRT1, inhibit AMPK phosphorylation, and block autophagic flow in both mice and cells. After treating the cells with the SIRT1 agonist SRT1720, SIRT1/AMPK pathway and autophagy-related proteins were partially reversed and the number of PA-induced positive cells was alleviated in senescence-associated β-galactosidase (SA-β-gal) staining. CONCLUSIONS:HFD may inhibit the expression of SIRT1/AMPK pathway and disrupt autophagy flux, and result in tau hyperphosphorylation and synaptic dysfunction during aging, which ultimately lead to cognitive decline.
10.1016/j.expneurol.2023.114591
Metabolomics Based on H-NMR Reveal the Regulatory Mechanisms of Dietary Methionine Restriction on Splenic Metabolic Dysfunction in Obese Mice.
Yang Yuhui,Qian Jing,Li Bowen,Lu Manman,Le Guowei,Xie Yanli
Foods (Basel, Switzerland)
Methionine restriction (MR) has been reported to have many beneficial health effects, including stress resistance enhancement and lifespan extension. However, the effects of MR on the splenic metabolic dysfunction induced by obesity in mice remain unknown. This study aimed to investigate the scientific problem and clarify its possible mechanisms. C57BL/6J mice in the control group were fed a control diet (0.86% methionine, 4.2% fat) for 34 weeks, and others were fed a high-fat diet (0.86% methionine, 24% fat) for 10 weeks to establish diet-induced obese (DIO) mouse models. Then, the obtained DIO mice were randomly divided into two groups: the DIO group (DIO diet), the DIO + MR group (0.17% methionine, 24% fat) for 24 weeks. Our results indicated that MR decreased spleen weight, and spleen and plasma lipid profiles, promoted lipid catabolism and fatty acid oxidation, glycolysis and tricarboxylic acid cycle metabolism, and improved mitochondrial function and ATP generation in the spleen. Moreover, MR normalized the splenic redox state and inflammation-related metabolite levels, and increased plasma levels of immunoglobulins. Furthermore, MR increased percent lean mass and splenic crude protein levels, activated the autophagy pathway and elevated nucleotide synthesis to maintain protein synthesis in the spleen. These findings indicate that MR can ameliorate metabolic dysfunction by reducing lipid accumulation, oxidative stress, and inflammation in the spleen, and the mechanism may be the activation of autophagy pathway.
10.3390/foods10102439
Increasing Fatty Acid Oxidation Prevents High-Fat Diet-Induced Cardiomyopathy Through Regulating Parkin-Mediated Mitophagy.
Shao Dan,Kolwicz Stephen C,Wang Pei,Roe Nathan D,Villet Outi,Nishi Kiyoto,Hsu Yun-Wei A,Flint Galina V,Caudal Arianne,Wang Wang,Regnier Michael,Tian Rong
Circulation
BACKGROUND:Increased fatty acid oxidation (FAO) has long been considered a culprit in the development of obesity/diabetes mellitus-induced cardiomyopathy. However, enhancing cardiac FAO by removing the inhibitory mechanism of long-chain fatty acid transport into mitochondria via deletion of acetyl coenzyme A carboxylase 2 (ACC2) does not cause cardiomyopathy in nonobese mice, suggesting that high FAO is distinct from cardiac lipotoxicity. We hypothesize that cardiac pathology-associated obesity is attributable to the imbalance of fatty acid supply and oxidation. Thus, we here seek to determine whether further increasing FAO by inducing ACC2 deletion prevents obesity-induced cardiomyopathy, and if so, to elucidate the underlying mechanisms. METHODS:We induced high FAO in adult mouse hearts by cardiac-specific deletion of ACC2 using a tamoxifen-inducible model (ACC2 iKO). Control and ACC2 iKO mice were subjected to high-fat diet (HFD) feeding for 24 weeks to induce obesity. Cardiac function, mitochondria function, and mitophagy activity were examined. RESULTS:Despite both control and ACC2 iKO mice exhibiting a similar obese phenotype, increasing FAO oxidation by deletion of ACC2 prevented HFD-induced cardiac dysfunction, pathological remodeling, and mitochondria dysfunction, as well. Similarly, increasing FAO by knockdown of ACC2 prevented palmitate-induced mitochondria dysfunction and cardiomyocyte death in vitro. Furthermore, HFD suppressed mitophagy activity and caused damaged mitochondria to accumulate in the heart, which was attenuated, in part, in the ACC2 iKO heart. Mechanistically, ACC2 iKO prevented HFD-induced downregulation of parkin. During stimulation for mitophagy, mitochondria-localized parkin was severely reduced in control HFD-fed mouse heart, which was restored, in part, in ACC2 iKO HFD-fed mice. CONCLUSIONS:These data show that increasing cardiac FAO alone does not cause cardiac dysfunction, but protects against cardiomyopathy in chronically obese mice. The beneficial effect of enhancing cardiac FAO in HFD-induced obesity is mediated, in part, by the maintenance of mitochondria function through regulating parkin-mediated mitophagy. Our findings also suggest that targeting the parkin-dependent mitophagy pathway could be an effective strategy against the development of obesity-induced cardiomyopathy.
10.1161/CIRCULATIONAHA.119.043319
Role of skeletal muscle autophagy in high-fat-diet-induced obesity and exercise.
Herrenbruck Adrienne R,Bollinger Lance M
Nutrition reviews
Autophagy is a complex degradation pathway responsible for clearing damaged and dysfunctional organelles. High-fat-diet-induced obesity has been shown to alter autophagy throughout the body in a tissue-specific manner. The impact of obesity on skeletal muscle autophagy has yet to be elucidated. This review examines the impact of high-fat-diet-induced obesity and exercise on skeletal muscle autophagy. Better understanding this major quality control mechanism may help develop novel therapies to combat high-fat-diet-induced obesity comorbidities.
10.1093/nutrit/nuz044
Effects of high-fat diet-induced diabetes on autophagy in the murine liver: A systematic review and meta-analysis.
Life sciences
AIMS:We conducted a meta-analysis to investigate whether diabetes induced by a high-fat diet (HFD) has the potential to alter the process of autophagy in the murine liver. METHODS:A systematic literature search was performed with electronic databases (PubMed, EMBASE, Web of Science). Study design, population, intervention, outcome, and risk of bias were analyzed. Given the availability of studies, a quantitative meta-analysis including 23 studies was performed. KEY FINDINGS:The search found 5754 articles, with 48 matching the eligibility criteria, comprising of 1033 animals. The meta-analysis showed that diabetic murines fed with HFD presented an absence of p62 degradation (SMD 4.63, 95 % CI 2.02 to 7.24, p = 0.0005; I = 77 %), higher expression of p-mTOR/mTOR (SMD 5.20, 95 % CI 1.00 to 9.39, p = 0.01; I = 78 %), and a decreased p-AMPK/AMPK ratio (SMD -2.02, 95 % CI -3.96 to -0.09, p = 0.04; I = 85 %) when compared to nondiabetic murines. When associated with streptozotocin, the animals presented decreased ATG-7 and LC3-II. The meta-regression results showed a decrease in autophagy responses due to increased glycemic levels, fat content, and long-term exposure to HFD, and advanced animal age. The common and species-specific protein responses were also consistent with the inhibition of autophagy. SIGNIFICANCE:The normal process of autophagy mechanisms in the liver is less competent after HFD consumption. The destabilization of (auto)phagolysosomes contributes to the perpetuation of diabetes, metabolic dysfunction-associated fatty liver disease, and cell death.
10.1016/j.lfs.2022.121012
Dysfunction of autophagy in high-fat diet-induced non-alcoholic fatty liver disease.
Autophagy
ABBREVIATIONS:ACOX1: acyl-CoA oxidase 1; ADH5: alcohol dehydrogenase 5 (class III), chi polypeptide; ADIPOQ: adiponectin, C1Q and collagen domain containing; ATG: autophagy related; BECN1: beclin 1; CRTC2: CREB regulated transcription coactivator 2; ER: endoplasmic reticulum; F2RL1: F2R like trypsin receptor 1; FA: fatty acid; FOXO1: forkhead box O1; GLP1R: glucagon like peptide 1 receptor; GRK2: G protein-coupled receptor kinase 2; GTPase: guanosine triphosphatase; HFD: high-fat diet; HSCs: hepatic stellate cells; HTRA2: HtrA serine peptidase 2; IRGM: immunity related GTPase M; KD: knockdown; KDM6B: lysine demethylase 6B; KO: knockout; LAMP2: lysosomal associated membrane protein 2; LAP: LC3-associated phagocytosis; LDs: lipid droplets; Li KO: liver-specific knockout; LSECs: liver sinusoidal endothelial cells; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAP3K5: mitogen-activated protein kinase kinase kinase 5; MED1: mediator complex subunit 1; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin complex 1; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; NFE2L2: NFE2 like bZIP transcription factor 2; NOS3: nitric oxide synthase 3; NR1H3: nuclear receptor subfamily 1 group H member 3; OA: oleic acid; OE: overexpression; OSBPL8: oxysterol binding protein like 8; PA: palmitic acid; RUBCNL: rubicon like autophagy enhancer; PLIN2: perilipin 2; PLIN3: perilipin 3; PPARA: peroxisome proliferator activated receptor alpha; PRKAA2/AMPK: protein kinase AMP-activated catalytic subunit alpha 2; RAB: member RAS oncogene family; RPTOR: regulatory associated protein of MTOR complex 1; SCD: stearoyl-CoA desaturase; SIRT1: sirtuin 1; SIRT3: sirtuin 3; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1;SREBF2: sterol regulatory element binding transcription factor 2; STING1: stimulator of interferon response cGAMP interactor 1; STX17: syntaxin 17; TAGs: triacylglycerols; TFEB: transcription factor EB; TP53/p53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VMP1: vacuole membrane protein 1.
10.1080/15548627.2023.2254191