p62 Stages an interplay between the ubiquitin-proteasome system and autophagy in the heart of defense against proteotoxic stress

The HSP90AA1 gene is involved in heat stress responses and its functional genetic polymorphisms are associated with heat tolerance in Holstein cows

As the stress-inducible isoform of the heat-shock protein 90 (HSP90), the HSP90AA1 gene encodes HSP90α and plays an important role in heat stress (HS) response. Therefore, this study aimed to investigate the role of the HSP90AA1 gene in cellular responses during HS and to identify functional SNPs associated with thermotolerance in Holstein cattle. For the in vitro validation experiment of acute HS, cells from the Madin-Darby bovine kidney cell line were exposed to 42°C for 1 h, and various parameters were assessed, including cell apoptosis, cell autophagy, and the cellular functions of HSP90α by using its inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). Furthermore, the polymorphisms identified in the HSP90AA1 gene and their functions related to HS were validated in vitro. Acute HS exposure induced cell apoptosis, cell autophagy, and upregulated expression of the HSP90AA1 gene. Inhibition of HSP90α by 17-AAG treatment had a significant effect on the expression of the HSP90α protein and increased cell apoptosis. However, autophagy decreased in comparison to the control treatment when cells were exposed to 42°C for 1 h. Five SNPs identified in the HSP90AA1 gene were significantly associated with rectal temperature and respiration score in Holstein cows, in which the rs109256957 SNP is located in the 3' untranslated region (3' UTR). Furthermore, we demonstrated that the 3' UTR of HSP90AA1 is a direct target of bta-miR-1224 by cell transfection with exogenous microRNA (miRNA) mimic and inhibitor. The luciferase assays revealed that the SNP rs109256957 affects the regulation of bta-miR-1224 binding activity and alters the expression of the HSP90AA1 gene. Heat stress-induced HSP90AA1 expression maintains cell survival by inhibiting cell apoptosis and increasing cell autophagy. The rs109256957 located in the 3' UTR region is a functional variation and it affects the HSP90AA1 expression by altering its binding activity with bta-miR-1224, thereby associating with the physiological parameters of Holstein cows.

Sequestosome 1 (p62) mitigates hypoxia-induced cardiac dysfunction by stabilizing hypoxia-inducible factor 1α and nuclear factor erythroid 2-related factor 2

AIMS

Heart failure due to ischaemic heart disease (IHD) is a leading cause of mortality worldwide. A major contributing factor to IHD-induced cardiac damage is hypoxia. Sequestosome 1 (p62) is a multi-functional adaptor protein with pleiotropic roles in autophagy, proteostasis, inflammation, and cancer. Despite abundant expression in cardiomyocytes, the role of p62 in cardiac physiology is not well understood. We hypothesized that cardiomyocyte-specific p62 deletion evokes hypoxia-induced cardiac pathology by impairing hypoxia-inducible factor 1α (Hif-1α) and nuclear factor erythroid 2-related factor 2 (Nrf2) signalling.

METHODS AND RESULTS

Adult mice with germline deletion of cardiomyocyte p62 exhibited mild cardiac dysfunction under normoxic conditions. Transcriptomic analyses revealed a selective impairment in Nrf2 target genes in the hearts from these mice. Demonstrating the functional importance of this adaptor protein, adult mice with inducible depletion of cardiomyocyte p62 displayed hypoxia-induced contractile dysfunction, oxidative stress, and cell death. Mechanistically, p62-depleted hearts exhibit impaired Hif-1α and Nrf2 transcriptional activity. Because findings from these two murine models suggested a cardioprotective role for p62, mechanisms were evaluated using H9c2 cardiomyoblasts. Loss of p62 in H9c2 cells exposed to hypoxia reduced Hif-1α and Nrf2 protein levels. Further, the lack of p62 decreased Nrf2 protein expression, nuclear translocation, and transcriptional activity. Repressed Nrf2 activity associated with heightened Nrf2-Keap1 co-localization in p62-deficient cells, which was concurrent with increased Nrf2 ubiquitination facilitated by the E3 ligase Cullin 3, followed by proteasomal-mediated degradation. Substantiating our results, a gain of p62 in H9c2 cells stabilized Nrf2 and increased the transcriptional activity of Nrf2 downstream targets.

CONCLUSION

Cardiac p62 mitigates hypoxia-induced cardiac dysfunction by stabilizing Hif-1α and Nrf2.

COTE-1 promotes the proliferation and invasion of small cell lung cancer by regulating autophagy activity via the AMPK/mTOR signaling pathway

BACKGROUND

COTE-1 has been found to promote the proliferation and invasion of non-small cell lung cancer. However, the mechanism of COTE-1 in SCLC is still unclear. Exploring the role of COTE-1 in SCLC is expected to provide a potential target for the prognosis and treatment of SCLC.

METHODS

The expression of COTE-1 and ki-67 was detected by immunohistochemical staining. PCR detected COTE-1 expression level. Cell proliferation activity was detected by CCK8 assay. A wound healing test detected cell migrative ability. Transwell invasion assay detected cell invasive ability. The numbers of autophagosomes were observed by transmission electron microscopy. WB detected the expression levels of autophagy-related proteins and AMPK/mTOR pathway-related proteins. The effect of COTE-1 expression level on the proliferation of SCLC tumor tissues was investigated by establishing a mouse SCLC xenograft tumor model.

RESULTS

The expression of COTE-1 in SCLC tissues and cells was higher than that in normal tissues and cells. In SCLC cells with high COTE-1 expression, the expression level of autophagy proteins was notably increased, the number of intracellular autophagosomes increased, and the proliferative activity, migration and invasion abilities were enhanced. COTE-1 promotes autophagy, proliferation, and invasion of SCLC cells under nutrient deprivation by activating the AMPK/mTOR signaling pathway. Activation of autophagy by COTE-1 promotes the proliferation and development of xenograft tumors in a mouse model of SCLC.

CONCLUSION

COTE-1 promotes the proliferation, migration and invasion of small cell lung cancer by mediating autophagy based on the AMPK/mTOR pathway.

Autophagy (but not metabolism) is a key event in mitoxantrone-induced cytotoxicity in differentiated AC16 cardiac cells

Mitoxantrone (MTX) is an antineoplastic agent used to treat advanced breast cancer, prostate cancer, acute leukemia, lymphoma and multiple sclerosis. Although it is known to cause cumulative dose-related cardiotoxicity, the underlying mechanisms are still poorly understood. This study aims to compare the cardiotoxicity of MTX and its' pharmacologically active metabolite naphthoquinoxaline (NAPHT) in an in vitro cardiac model, human-differentiated AC16 cells, and determine the role of metabolism in the cardiotoxic effects. Concentration-dependent cytotoxicity was observed after MTX exposure, affecting mitochondrial function and lysosome uptake. On the other hand, the metabolite NAPHT only caused concentration-dependent cytotoxicity in the MTT reduction assay. When assessing the effect of different inhibitors/inducers of metabolism, it was observed that metyrapone (a cytochrome P450 inhibitor) and phenobarbital (a cytochrome P450 inducer) slightly increased MTX cytotoxicity, while 1-aminobenzotriazole (a suicide cytochrome P450 inhibitor) decreased fairly the MTX-triggered cytotoxicity in differentiated AC16 cells. When focusing in autophagy, the mTOR inhibitor rapamycin and the autophagy inhibitor 3-methyladenine exacerbated the cytotoxicity caused by MTX and NAPHT, while the autophagy blocker, chloroquine, partially reduced the cytotoxicity of MTX. In addition, we observed a decrease in p62, beclin-1, and ATG5 levels and an increase in LC3-II levels in MTX-incubated cells. In conclusion, in our in vitro model, neither metabolism nor exogenously given NAPHT are major contributors to MTX toxicity as seen by the residual influence of metabolism modulators used on the observed cytotoxicity and by NAPHT's low cytotoxicity profile. Conversely, autophagy is involved in MTX-induced cytotoxicity and MTX seems to act as an autophagy inducer, possibly through p62/LC3-II involvement.

The converging roles of sequestosome-1/p62 in the molecular pathways of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD)

Investigations into the pathogenetic mechanisms underlying amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) have provided significant insight into the disease. At the cellular level, ALS and FTD are classified as proteinopathies, which is motor neuron degeneration and death characterized by pathological protein aggregates or dysregulated proteostasis. At both the clinical and molecular level there are common signaling pathways dysregulated across the ALS and FTD spectrum (ALS/FTD). Sequestosome-1/p62 is a multifunctional scaffold protein with roles in several signaling pathways including proteostasis, protein degradation via the ubiquitin proteasome system and autophagy, the antioxidant response, inflammatory response, and apoptosis. Notably these pathways are dysregulated in ALS and FTD. Mutations in the functional domains of p62 provide links to the pathogenetic mechanisms of p62 and dyshomeostasis of p62 levels is noted in several types of ALS and FTD. We present here that the dysregulated ALS and FTD signaling pathways are linked, with p62 converging the molecular mechanisms. This review summarizes the current literature on the complex role of p62 in the pathogenesis across the ALS/FTD spectrum. The focus is on the underlying convergent molecular mechanisms of ALS and FTD-associated proteins and pathways that dysregulate p62 levels or are dysregulated by p62, with emphasis on how p62 is implicated across the ALS/FTD spectrum.

Development and validation of a robust epithelial-mesenchymal transition (EMT)-related prognostic signature for hepatocellular carcinoma

OBJECTIVE

Epithelial-to-mesenchymal transition (EMT) is an essential biological process of cancer progression associated with increased metastatic potential and initiation. Herein, we aimed to develop and validate a robust EMT-related prognostic signature that could predict the prognosis of patients with hepatocellular carcinoma (HCC).

METHODS

Messenger RNA expression matrix and clinicopathological data were retrieved from The Cancer Genome Atlas (TCGA) and identified differentially expressed genes (DEGs) between HCC tissues and adjacent non-tumor samples. Univariate Cox regression analysis, least absolute shrinkage and selection operator (LASSO) Cox regression and multivariate Cox regression analysis were performed to establish a prognosis signature. Kaplan-Meier survival curve, time-dependent receiver operating characteristic (ROC), multivariate Cox regression analysis, nomogram, C-index, and decision curve analysis (DCA) were performed to investigate the prognostic performance of the signature. The prognostic performance of the new signature was further validated in an independent external cohort. A support vector machine (SVM) approach was performed to evaluate the diagnostic value of the identified genes.

RESULTS

A seven-gene signature was formulated to classify patients into high-risk and low-risk groups with discrepant overall survival (OS) in two cohorts (all P < 0.0001), and the former illustrated shorter survival time than the latter even stratified by various groups. The new signature has presented an excellent performance for predicting survival prognosis. Multivariate analysis showed that the signature was an independent risk factor for HCC. The SVM classifier based on the seven genes presented an excellent diagnostic power in differentiating early HCC and normal tissues. Gene Set Enrichment Analyses (GSEA) demonstrated multiple biological processes and pathways to provide novel insights into the development of HCC.

CONCLUSION

We established and validated a prognostic signature based on EMT-related genes with good predictive value for HCC survival. The diagnostic performance of the signature had been demonstrated to accurately distinguish early HCC from control individuals.

Different Roles of p62 (SQSTM1) Isoforms in Keratin-Related Protein Aggregation

p62/Sequestosome-1 (p62) is a multifunctional adaptor protein and is also a constant component of disease-associated protein aggregates, including Mallory–Denk bodies (MDBs), in steatohepatitis and hepatocellular carcinoma. We investigated the interaction of the two human p62 isoforms, p62-H1 (full-length isoform) and p62-H2 (partly devoid of PB1 domain), with keratins 8 and 18, the major components of MDBs. In human liver, p62-H2 is expressed two-fold higher compared to p62-H1 at the mRNA level and is present in slightly but not significantly higher concentrations at the protein level. Co-transfection studies in CHO-K1 cells, PLC/PRF/5 cells as well as p62⁻ total-knockout and wild-type mouse fibroblasts revealed marked differences in the cytoplasmic distribution and aggregation behavior of the two p62 isoforms. Transfection-induced overexpression of p62-H2 generated large cytoplasmic aggregates in PLC/PRF/5 and CHO-K1 cells that mostly co-localized with transfected keratins resembling MDBs or (transfection without keratins) intracytoplasmic hyaline bodies. In fibroblasts, however, transfected p62-H2 was predominantly diffusely distributed in the cytoplasm. Aggregation of p62-H2 and p62ΔSH2 as well as the interaction with K8 (but not with K18) involves acquisition of cross-β-sheet conformation as revealed by staining with luminescent conjugated oligothiophenes. These results indicate the importance of considering p62 isoforms in protein aggregation disease.

Artesunate-induced ATG5-related autophagy enhances the cytotoxicity of NK92 cells on endometrial cancer cells via interactions between CD155 and CD226/TIGIT

Uterine corpus endometrial carcinoma (UCEC) is the most prevalent gynecologic cancer in developed countries and lacks efficient therapeutic strategies. Artesunate (ART), a well-modified derivate of artemisinin, exerts potent anti-cancer effects apart from its classical anti-malaria feature. Autophagy is a universal double-edged process in cell survival, and CD155 is a novel immune checkpoint highly expressed in numerous cancers. However, the relationships among ART, autophagy, and CD155 remain unclear in UCEC. In this study, we discovered that ART not only inhibited proliferation and migration, promoted apoptosis, but also induced autophagy in UCEC cells. Meanwhile, ART-induced autophagy elevated the level of CD155 in UCEC cells, thereby enhancing the cytotoxicity of natural killer cell line (NK92) by modulating the interactions between CD155 and its receptors in NK92 cells via upregulation of co-stimulator CD226 and downregulation of co-inhibitor TIGIT. Additionally, ART regulated CD155 partially via ATG5, and knockdown of ATG5 dampened the expression of CD155 in UCEC cells, thus decreasing the cytotoxicity of NK92 cells. Therefore, this study demonstrated the dual anti-cancer effects of ART as it could induce cell-killing directly and indirectly, which provides novel insights into the anti-cancer mechanisms of ART on UCEC.

An updated review of autophagy in ischemic stroke: From mechanisms to therapies

Stroke is a leading cause of mortality and morbidity worldwide. Understanding the underlying mechanisms is important for developing effective therapies for treating stroke. Autophagy is a self-eating cellular catabolic pathway, which plays a crucial homeostatic role in the regulation of cell survival. Increasing evidence shows that autophagy, observed in various cell types, plays a critical role in brain pathology after ischemic stroke. Therefore, the regulation of autophagy can be a potential target for ischemic stroke treatment. In the present review, we summarize the recent progress that research has made regarding autophagy and ischemic stroke, including common signaling pathways, the role of autophagic subtypes (e.g. mitophagy, pexophagy, aggrephagy, endoplasmic reticulum-phagy, and lipophagy) in ischemic stroke, as well as the current methods for autophagy detection and potential therapeutic strategy.

Functional analysis of a gene-edited mouse model to gain insights into the disease mechanisms of a titin missense variant

Titin truncating variants are a well-established cause of cardiomyopathy; however, the role of titin missense variants is less well understood. Here we describe the generation of a mouse model to investigate the underlying disease mechanism of a previously reported titin A178D missense variant identified in a family with non-compaction and dilated cardiomyopathy. Heterozygous and homozygous mice carrying the titin A178D missense variant were characterised in vivo by echocardiography. Heterozygous mice had no detectable phenotype at any time point investigated (up to 1 year). By contrast, homozygous mice developed dilated cardiomyopathy from 3 months. Chronic adrenergic stimulation aggravated the phenotype. Targeted transcript profiling revealed induction of the foetal gene programme and hypertrophic signalling pathways in homozygous mice, and these were confirmed at the protein level. Unsupervised proteomics identified downregulation of telethonin and four-and-a-half LIM domain 2, as well as the upregulation of heat shock proteins and myeloid leukaemia factor 1. Loss of telethonin from the cardiac Z-disc was accompanied by proteasomal degradation; however, unfolded telethonin accumulated in the cytoplasm, leading to a proteo-toxic response in the mice.We show that the titin A178D missense variant is pathogenic in homozygous mice, resulting in cardiomyopathy. We also provide evidence of the disease mechanism: because the titin A178D variant abolishes binding of telethonin, this leads to its abnormal cytoplasmic accumulation. Subsequent degradation of telethonin by the proteasome results in proteasomal overload, and activation of a proteo-toxic response. The latter appears to be a driving factor for the cardiomyopathy observed in the mouse model.

HT-2 toxin affects cell viability of goat spermatogonial stem cells through AMPK-ULK1 autophagy pathways

HT-2 toxin is widely found in moldy crops and is the major metabolite of T-2 toxin, which has been shown to exert various toxic effects in farm animals. However, little is known about the effects of HT-2 toxin on male reproduction, particularly spermatogenesis. This study aims to investigate the toxic effects of HT-2 toxin on goat spermatogonial stem cells (SSCs) and related autophagy-regulated mechanisms. Our results showed that HT-2 toxin exposure resulted in decreased cell viability and proliferation, disrupted SSCs self-renewal, and reduced germ cell-related gene expression. HT-2 toxin exposure also induced oxidative stress and cell apoptosis, as shown by ROS accumulation, increased antioxidant enzyme activity levels, decreased the mitochondrial membrane potential, and increased caspase-9 mRNA and Bcl/bax protein levels. Additionally, HT-2 toxin exposure increased the expression of the autophagy-inducing genes Atg5, Atg7 and Beclin1 and the number of autophagosomes, which indicated that HT-2 toxin induced autophagy in the goat SSCs. Moreover, we also examined a possible mechanism by which HT-2 toxin exposure induced higher expression of AMPK, mTOR and ULK at both the mRNA and protein levels. our results indicated that HT-2 toxin caused apoptosis and autophagy by activating AMPK-mTOR-ULK1 pathway, which further affected SSCs viability.

[Sirt3 gene knockout protects mice from Alzheimer's disease through activating autophagy]

OBJECTIVE

To investigate the protective effect of Sirt3 gene knockout on Alzheimer's disease (AD) in mice.

METHODS

The animal model of AD was established by intraperitoneal injection of D-galactose and brain-localized injection of amyloid β-protein (Aβ)1-40 in wild type C57BL/6 mice and Sirt3 gene knockout mice. Morris water maze, Y maze and tail suspension test were used to assess the cognitive function and anxiety-like behaviors in mice. Aβ deposition in the hippocampus was detected by immunofluorescent staining. Western blotting analysis was conducted to detect the expression of related proteins in the brain. Mouse cortical primary neurons were cultured and AD cell model was established. MTT assay was used to detect cell viability after modeling.

RESULTS

Behavioral results showed that cognitive deficits were found in wide type mice after induction of AD as its prolonged escape latency (P<0.05) and decreased crossing number of platform and target zone duration (all P<0.05); while the knockout of Sirt3 alleviated cognitive deficit induced by AD (all P<0.05). Aβ immunofluorescence staining showed that the deposition of Aβ in the hippocampal region and expression of cleaved caspase 3 in the brain in Sirt3 knockout mice was reduced compared with that of wild type mice (all P<0.05). The expression of LC3-Ⅱ and P62 increased after AD was induced in wild type mice, while the autophagy in Sirt3 knockout mice was activated as the increase expression of LC3-Ⅱ and decrease expression of P62 (all P<0.05). In the AD cell model, the results of MTT assay were consistent with the animal experiments, and the protective effect of Sirt3 knockdown was eliminated after the treatment of the autophagy inhibitor chloroquine (all P<0.05).

CONCLUSIONS

The knockdown of Sirt3 shows a protective effect on AD induced by D-galactose and Aβ1-40 in mice, which may be related to its function of activating autophagy.

Cardamonin Reduces Acetaminophen-Induced Acute Liver Injury in Mice via Activating Autophagy and NFE2L2 Signaling

Cardamonin (CD), a naturally occurring chalcone derived from the Alpinia species, has been shown to exert antioxidant and anti-inflammatory activity, but its role in the prevention of acetaminophen- (APAP-) induced hepatotoxicity remains elusive. The objective of this study was to determine the protective effects of CD against APAP-induced acute liver injury (ALI) and the underlying mechanisms. Wild-type or transcription factor nuclear factor erythroid 2-related factor 2- (NFE2L2-) deficient mice were treated with CD (50 or 100 mg/kg, i.p.) or vehicle for 24 h. Subsequently, these mice were challenged with APAP (400 mg/kg, i.p.) for 6 h. Liver and blood samples were collected to evaluate liver injury and protein abundance. Treatment with CD significantly reduced APAP-induced hepatotoxicity. Furthermore, CD effectively reduced APAP-induced inflammation by inhibiting high mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), and NOD-like receptor protein 3 (NLRP3) signaling. In addition, CD induced activation of sequestosome 1 (p62) and NFE2L2 signaling and facilitated autophagy. By applying autophagy inhibitor 3-methyladenine (3-MA; 20 mg/kg, i.p.), further mechanistic exploration revealed that NFE2L2 deficiency promoted autophagic activity induced by CD treatment, which was conducive to the hepatoprotective effect of CD against APAP-induced hepatoxicity in NFE2L2^−/− mice. Overall, data suggest that CD has hepatoprotective effect against APAP-induced ALI, which might contribute to the activation of NFE2L2 and autophagy.

Cellular Protein Quality Control in Diabetic Cardiomyopathy: From Bench to Bedside

Heart failure is a serious comorbidity and the most common cause of mortality in diabetes patients. Diabetic cardiomyopathy (DCM) features impaired cellular structure and function, culminating in heart failure; however, there is a dearth of specific clinical therapy for treating DCM. Protein homeostasis is pivotal for the maintenance of cellular viability under physiological and pathological conditions, particularly in the irreplaceable cardiomyocytes; therefore, it is tightly regulated by a protein quality control (PQC) system. Three evolutionarily conserved molecular processes, the unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), and autophagy, enhance protein turnover and preserve protein homeostasis by suppressing protein translation, degrading misfolded or unfolded proteins in cytosol or organelles, disposing of damaged and toxic proteins, recycling essential amino acids, and eliminating insoluble protein aggregates. In response to increased cellular protein demand under pathological insults, including the diabetic condition, a coordinated PQC system retains cardiac protein homeostasis and heart performance, on the contrary, inappropriate PQC function exaggerates cardiac proteotoxicity with subsequent heart dysfunction. Further investigation of the PQC mechanisms in diabetes propels a more comprehensive understanding of the molecular pathogenesis of DCM and opens new prospective treatment strategies for heart disease and heart failure in diabetes patients. In this review, the function and regulation of cardiac PQC machinery in diabetes mellitus, and the therapeutic potential for the diabetic heart are discussed.

The Multifunctional Protein p62 and Its Mechanistic Roles in Cancers

The multifunctional signaling hub p62 is well recognized as a ubiquitin sensor and a selective autophagy receptor. As a ubiquitin sensor, p62 promotes NFκB activation by facilitating TRAF6 ubiquitination and aggregation. As a selective autophagy receptor, p62 sorts ubiquitinated substrates including p62 itself for lysosome-mediated degradation. p62 plays crucial roles in myriad cellular processes including DNA damage response, aging/senescence, infection and immunity, chronic inflammation, and cancerogenesis, dependent on or independent of autophagy. Targeting p62-mediated autophagy may represent a promising strategy for clinical interventions of different cancers. In this review, we summarize the transcriptional and post-translational regulation of p62, and its mechanistic roles in cancers, with the emphasis on its roles in regulation of DNA damage response and its connection to the cGAS-STING-mediated antitumor immune response, which is promising for cancer vaccine design.

Cytoprotective autophagy induction by withaferin A in prostate cancer cells involves GABARAPL1

Withaferin A (WA) is a naturally occurring steroidal lactone with proven cancer chemopreventive activity in preclinical models of different cancers including prostate adenocarcinoma. Previously we compared the RNA-seq data from control and WA-treated 22Rv1 human prostate cancer cells to identify mechanistic targets of this phytochemical. The Gene Ontology pathway analysis of the RNA-seq data revealed significant upregulation of genes associated with autophagy upon WA treatment in 22Rv1 cells. In this study, we extended these findings to investigate the mechanism underlying WA-induced autophagy. Initially, we confirmed autophagy induction by WA treatment by transmission electron microscopy using three prostate cancer cell lines (LNCaP, 22Rv1, and PC-3). Fourteen common genes altered by 8- and 16-hour exposure to WA were identified from human autophagy PCR array and these results were consistent with the RNA-seq data. Two key autophagy markers (LC3BII and SQSTM1) were robustly increased in WA-exposed LNCaP, 22Rv1, and PC-3 cells as determined by immunoblotting, and this effect was elevated in the presence of autophagy inhibitor bafilomycin A1 (BafA1). BafA1 treatment augmented WA's cytotoxicity and subsequently its proapoptotic potential. WA treatment induced GABARAPL1 (ATG8L) protein expression in all three cell lines and its knockdown by RNA interference attenuated WA-mediated apoptosis. WA-induced autophagy was not affected in the presence of an antioxidant (EUK134). Taken together, the present study reveals that WA-mediated autophagy is cytoprotective and mediated by GABARAPL1.

Clinical significance of SQSTM1/P62 and nuclear factor-κB expression in pancreatic carcinoma

BACKGROUND

Overexpression of SQSTM1 (sequestosome 1, P62) and nuclear factor-κB (NF-κB) plays an important role in the invasion and metastasis of a variety of malignant tumors.

AIM

To explore the expression of P62 and NF-κB in pancreatic cancer and their relationship with clinicopathological features.

METHODS

The expression levels of P62 and NF-κB were analyzed by immunohistochemistry with a tissue chip containing 40 cases of human pancreatic carcinoma. Then we analyzed the correlation among P62 expression, phospho-P65 expression, and clinicopathological features of pancreatic carcinoma samples.

RESULTS

P62 expression was mainly observed in the cytoplasm of pancreatic carcinoma cells. Phosphorylated P65 (phospho-P65) was mainly expressed in the nucleus and cytoplasm of pancreatic carcinoma cells. There was a significant difference in P62 expression among T stages. And a significant difference in phosphor-P65 expression among pathology types was noted. In the cases with strongly positive P62 expression, significant differences were found in age. And there were significant differences in T stage and tumor-node-metastasis stage in the cases with strongly positive phosphor-P65 expression.

CONCLUSION

In pancreatic carcinoma, P62 expression is significantly correlated with T stage. It may be a valuable malignant indicator for human pancreatic carcinoma.

The central regulator p62 between ubiquitin proteasome system and autophagy and its role in the mitophagy and Parkinson's disease

The ubiquitin-proteasome system (UPS) and autophagy are two major degradative pathways of proteins in eukaryotic cells. As about 30% of newly synthesized proteins are known to be misfolded under normal cell conditions, the precise and timely operation of the UPS and autophagy to remove them as well as their tightly controlled regulation, is so important for proper cell function and survival. In the UPS, target proteins are labeled by small proteins called ubiquitin, which are then transported to the proteasome complex for degradation. Alternatively, many greatly damaged proteins are believed to be delivered to the lysosome for autophagic degradation. Although these autophagy and UPS pathways have not been considered to be directly related, many recent studies proposed their close link and dynamic interconversion. In this review, we’ll focus on the several regulatory molecules that function in both UPS and autophagy and their crosstalk. Among the proposed multiple modulators, we will take a closer look at the so-called main connector of UPS-autophagy regulation, p62. Last, the functional role of p62 in the mitophagy and its implication for the pathogenesis of Parkinson’s disease, one of the major neurodegenerative diseases, will be briefly reviewed.

Harnessing Autophagic Network Is Essential for Trophoblast Stem Cell Differentiation

Differentiation of trophoblast stem (TS) cells into various cell lineages of the placenta during mammalian development is accompanied by dynamic changes in its proteome for exerting the highly specialized functions of various cell subtypes. In the present study, we demonstrate that the autophagic machinery, which includes proteins for initiation, vesicle nucleation, and autophagosome maturation are robustly upregulated during differentiation of TS cells. Interestingly, basal levels of autophagy were detectable in the developing mouse placenta as well as TS cells. However, autophagic flux was actively triggered by induction of differentiation evident from LC3 maturation. Formation of Beclin1, Vps34, and PIK3R4 ternary complex at the phagophore assembly site that is typically known to induce autophagy was also enhanced during differentiation. Degradation of the p62/SQSTM1 cargo protein and its colocalization with LC3, a mature autophagosome marker, was most prevalent in the trophoblast giant cells (TGCs) and negligible in other trophoblast cells at day 6 of differentiation. Furthermore, disruption of autophagy by impairing lysosomal fusion in TS cells before induction of differentiation led to a decrease in the giant cell and spongiotrophoblast cell markers Prl3d1, Prl2c2, Prl4a1, and Tpbpα upon differentiation. In addition, inhibition of autophagy was associated with a decrease in nuclear size of TGCs. Taken together, these data highlight that autophagy is a necessary prelude in commitment of trophoblast differentiation from the multipotent TS cells probably by regulating protein turnover at the onset of differentiation.

Degradation of the Tumor Suppressor PDCD4 Is Impaired by the Suppression of p62/SQSTM1 and Autophagy

PDCD4 (programmed cell death 4) is a tumor suppressor that plays a crucial role in multiple cellular functions, such as the control of protein synthesis and transcriptional control of some genes, the inhibition of cancer invasion and metastasis. The expression of this protein is controlled by synthesis, such as via transcription and translation, and degradation by the ubiquitin-proteasome system. The mitogens, known as tumor promotors, EGF (epidermal growth factor) and TPA (12-O-tetradecanoylphorbol-13-acetate) stimulate the degradation of PDCD4 protein. However, the whole picture of PDCD4 degradation mechanisms is still unclear, we therefore investigated the relationship between PDCD4 and autophagy. The proteasome inhibitor MG132 and the autophagy inhibitor bafilomycin A1 were found to upregulate the PDCD4 levels. PDCD4 protein levels increased synergistically in the presence of both inhibitors. Knockdown of p62/SQSTM1 (sequestosome-1), a polyubiquitin binding partner, also upregulated the PDCD4 levels. P62 and LC3 (microtubule-associated protein 1A/1B-light chain 3)-II were co-immunoprecipitated by an anti-PDCD4 antibody. Colocalization particles of PDCD4, p62 and the autophagosome marker LC3 were observed and the colocalization areas increased in the presence of autophagy and/or proteasome inhibitor(s) in Huh7 cells. In ATG (autophagy related) 5-deficient Huh7 cells in which autophagy was impaired, the PDCD4 levels were increased at the basal levels and upregulated in the presence of autophagy inhibitors. Based on the above findings, we concluded that after phosphorylation in the degron and ubiquitination, PDCD4 is degraded by both the proteasome and autophagy systems.

Flavorings-Related Lung Disease: A Brief Review and New Mechanistic Data

Flavorings-related lung disease is a potentially disabling and sometimes fatal lung disease of workers making or using flavorings. First identified almost 20 years ago in microwave popcorn workers exposed to butter-flavoring vapors, flavorings-related lung disease remains a concern today. In some cases, workers develop bronchiolitis obliterans, a severe form of fixed airways disease. Affected workers have been reported in microwave popcorn, flavorings, and coffee production workplaces. Volatile α-dicarbonyl compounds, particularly diacetyl (2,3-butanedione) and 2,3-pentanedione, are implicated in the etiology. Published studies on diacetyl and 2,3-pentanedione document their ability to cause airway epithelial necrosis, damage biological molecules, and perturb protein homeostasis. With chronic exposure in rats, they produce airway fibrosis resembling bronchiolitis obliterans. To add to this knowledge, we recently evaluated airway toxicity of the 3-carbon α-dicarbonyl compound, methylglyoxal. Methylglyoxal inhalation causes epithelial necrosis at even lower concentrations than diacetyl. In addition, we investigated airway toxicity of mixtures of diacetyl, acetoin, and acetic acid, common volatiles in butter flavoring. At ratios comparable to workplace scenarios, the mixtures or diacetyl alone, but not acetic acid or acetoin, cause airway epithelial necrosis. These new findings add to existing data to implicate α-dicarbonyl compounds in airway injury and flavorings-related lung disease.

SQSTM1/p62 is involved in docosahexaenoic acid-induced cellular autophagy in glioblastoma cell lines

Docosahexaenoic acid (DHA) is the most abundant n-3 polyunsaturated fatty acid in the human brain and works as an anticancer agent to induce cell cycle arrest and apoptosis in glioblastoma multiforme (GBM) cell lines. However, little is known about the connection between DHA and autophagy in GBM cells. We found that high-dose DHA caused cellular autophagy in cultured U251 and U118 GBM cell lines, but there was no effect with a low dose. Moreover, after treatment with a high dose of DHA at 12, 24, and 48 h, the protein expression of SQSTM1/p62 decreased in DHA-treated U251 cells at 12 and 24 h, but increased at 48 h, while in DHA-treated U118 cells, the protein expression increased at all time points. Interestingly, the level of SQSTM1/p62 mRNA was elevated in both DHA-treated U251 and U118 cells at all time points, indicating that DHA activated SQSTM1/p62 transcription in both cell lines. Furthermore, downregulation of SQSTM1/p62 by siRNA attenuated DHA-induced cellular autophagy in both cell lines. This report confirms that high-dose DHA induces cellular autophagy in GBM cells, and demonstrates that SQSTM1/p62 acts as a regulator and participates in DHA-induced autophagy.

Tongxinluo Ameliorates Myocardial Ischemia-Reperfusion Injury Mainly via Activating Parkin-Mediated Mitophagy and Downregulating Ubiquitin-Proteasome System

OBJECTIVE

To investigate the protective effects and mechanism of Chinese herbal compound Tongxinluo Capsule (, TXL) on the Parkin-mediated mitophagy and the ubiquitin-proteasome system in a rat model of myocardial ischemia-reperfusion injury (MIRI).

METHODS

Seventy adult male Sprague-Dawley rats were randomly divided into 7 groups: sham group, MIRI group, low- and high-dose TXL (0.5 and 1 g·kg^-1·d^-1, respectively) groups, atorvastatin (ATV) group (7.2 g·kg^-1·d^-1), chloroquine (CQ) group (10 g·kg^-1·d^-1), and highdose TXL + CQ group. After pharmacological administration for 7 days, rats underwent left anterior descending artery ligation surgery to establish the MIRI models with 50 min ischemia followed by 4 h reperfusion. Blood was taken for cardiac troponin I (cTnI) detection and hearts were harvested for infarct staining and apoptosis detection. The autophagy or mitophagy proteins and ubiquitinated proteins were detected by Western blotting.

RESULTS

Compared with the sham group, the MIRI group exhibited a larger infarcted area (27.13%±0.01%, P<0.01), a higher apoptotic index (34.33%±2.03% vs.1.81%±0.03%, P<0.01), and higher cTnI expression (14.18±1.01 vs. 7.96±0.32, P<0.01). The mitochondrial integrity was damaged in the MIRI group, while TXL and ATV alleviated the damage of MIRI. More autophagosomes were observed in the high-dose TXL group than in the MIRI group (7.00±0.58 vs. 4.33±1.15, P<0.05). More amounts of PTEN-induced putative kinase protein 1 (PINK1) and Parkin translocated onto the mitochondria were detected in the high-dose TXL group than in the MIRI group (P<0.05). The ubiquitin response was signifificantly downregulated in the high-dose TXL group relative to the MIRI group (P<0.05). CQ administration abolished the activation of autophagy flux and the PINK1/ Parkin pathway induced by high-dose of TXL.

CONCLUSIONS

TXL ameliorates MIRI via activating Parkin-mediated mitophagy in rats. The downregulation of the ubiquitin-proteasome system is also involved.

Role of Autophagy in Proteostasis: Friend and Foe in Cardiac Diseases

Due to ageing of the population, the incidence of cardiovascular diseases will increase in the coming years, constituting a substantial burden on health care systems. In particular, atrial fibrillation (AF) is approaching epidemic proportions. It has been identified that the derailment of proteostasis, which is characterized by the loss of homeostasis in protein biosynthesis, folding, trafficking, and clearance by protein degradation systems such as autophagy, underlies the development of common cardiac diseases. Among various safeguards within the proteostasis system, autophagy is a vital cellular process that modulates clearance of misfolded and proteotoxic proteins from cardiomyocytes. On the other hand, excessive autophagy may result in derailment of proteostasis and therefore cardiac dysfunction. Here, we review the interplay between autophagy and proteostasis in the healthy heart, discuss the imbalance between autophagy and proteostasis during cardiac diseases, including AF, and finally explore new druggable targets which may limit cardiac disease initiation and progression.

Autophagy exacerbates electrical remodeling in atrial fibrillation by ubiquitin-dependent degradation of L-type calcium channel

Autophagy, a bidirectional degradative process extensively occurring in eukaryotes, has been revealed as a potential therapeutic target for several cardiovascular diseases. However, its role in atrial fibrillation (AF) remains largely unknown. This study aimed to determine the role of autophagy in atrial electrical remodeling under AF condition. Here, we reported that autophagic flux was markedly activated in atria of persistent AF patients and rabbit model of atrial rapid pacing (RAP). We also observed that the key autophagy-related gene7 (ATG7) significantly upregulated in AF patients as well as tachypacing rabbits. Moreover, lentivirus-mediated ATG7 knockdown and overexpression in rabbits were employed to clarify the effects of autophagy on atrial electrophysiology via intracardiac operation and patch-clamp experiments. Lentivirus-mediated ATG7 knockdown or autophagy inhibitor chloroquine (CQ) restored the shortened atrial effective refractory period (AERP) and alleviated the AF vulnerability caused by tachypacing in rabbits. Conversely, ATG7 overexpression significantly promoted the incidence and persistence of AF and decreased L-type calcium channel (Cav1.2 α-subunits), along with abbreviated action potential duration (APD) and diminished L-type calcium current (I_Ca,L). Furthermore, the co-localization and interaction of Cav1.2 with LC3B-positive autophagosomes enhanced when autophagy was activated in atrial myocytes. Tachypacing-induced autophagic degradation of Cav1.2 required ubiquitin signal through the recruitment of ubiquitin-binding proteins RFP2 and p62, which guided Cav1.2 to autophagosomes. These findings suggest that autophagy induces atrial electrical remodeling via ubiquitin-dependent selective degradation of Cav1.2 and provide a novel and promising strategy for preventing AF development.

Emodin Attenuates Autophagy Response to Protect the Pancreas From Acute Pancreatitis Failure

OBJECTIVES

The aim of this study was to investigate the effects of emodin on attenuating autophagy response in acute pancreatitis (AP) models.

METHODS

Acute pancreatitis was induced in Wistar rats by injecting 3% sodium taurocholate into the biliopancreatic duct. Emodin (40 mg/kg per day) was then given intragastrically, administrated 2 hours after AP induction. Rats were killed 24 hours after AP induction. The pancreatic injury was assessed using biochemical and histological approaches. Autophagosomes in pancreatic acinar cells were observed by electron microscopy. The expression levels of microtubule-associated protein 1 light chain 3 (LC3) B/A, beclin-1, and p62/SQSTM1 (p62) were detected by Western blotting, quantitative real-time polymerase chain reaction, and immunohistochemistry in pancreatic tissues.

RESULTS

Compared with non-emodin-treated rats, the pathological injuries of the pancreas of emodin-treated rats were significantly alleviated, and autophagy vacuole formation was reduced within pancreatic acinar cells. Administration of emodin led to a reduction in the autophagy-associated protein level of LC3 (B/A) and p62 but not beclin-1. The transcript levels of LC3B, beclin-1, and p62 were decreased in the emodin-treated rats compared with non-emodin-treated rats.

CONCLUSIONS

Our data demonstrate that emodin plays a critical role in ameliorating AP, possibly by down-regulating autophagic protein levels.

Role of PERK-eIF2α signaling pathway in fetal male rats with hypospadias induced by di-n-butyl phthalate

This study aims to explore the role of PERK-eIF2α signaling pathway in fetal male rats with hypospadias induced by maternal exposure to di-n-butyl phthalate (DBP). DBP was used to treat pregnant SD rats by gastric intubation from gestation day (GD) 14-18 to construct a hypospadias rat model. The amount, weight, anogenital distance (AGD), and hypospadias incidence of rats were recorded and the genital tubercle (GT) of fetal male rats was collected on GD 19. Western blotting was performed to detect the expressions of PERK-eIF2α pathway- and autophagy-related proteins, and cell apoptosis was detected using TUNEL method. Then, GT fibroblasts of fetal rats were obtained and transfected with PERK-siRNA to detect cell apoptosis and autophagy in each transfected group. The incidence of hypospadias was 43.49% in fetal male rats induced by DBP. The fetal rats in DBP group presented the decreased birth weight and anogenital distance (AGD)/body weight ratio than the Control group (all P < 0.05). Further, p-PERK, p-eIF2α and ATF4 protein expressions and the ratio of LC3-II/LC3-I were greatly increased in the GTs of fetal rats, while apoptosis index (AI) and P62 protein expression were evidently decreased (all P < 0.05). In addition, the apoptosis rate was increased in GT fibroblasts after transfection of PERK-siRNA with the increased P62 and reduced LC3-II/LC3-I ratio (all P < 0.05). Activation of PERK-eIF2α signaling pathway can influence the GT development of fetal male rats with hypospadias induced by DBP through activation of autophagy and inhibition of apoptosis.

Synaptic activity protects against AD and FTD-like pathology via autophagic-lysosomal degradation

Changes in synaptic excitability and reduced brain metabolism are among the earliest detectable alterations associated with the development of Alzheimer's disease (AD). Stimulation of synaptic activity has been shown to be protective in models of AD beta-amyloidosis. Remarkably, deep brain stimulation (DBS) provides beneficial effects in AD patients, and represents an important therapeutic approach against AD and other forms of dementia. While several studies have explored the effect of synaptic activation on beta-amyloid, little is known about Tau protein. In this study, we investigated the effect of synaptic stimulation on Tau pathology and synapses in in vivo and in vitro models of AD and frontotemporal dementia (FTD). We found that chronic DBS or chemically induced synaptic stimulation reduced accumulation of pathological forms of Tau and protected synapses, while chronic inhibition of synaptic activity worsened Tau pathology and caused detrimental effects on pre- and post-synaptic markers, suggesting that synapses are affected. Interestingly, degradation via the proteasomal system was not involved in the reduction of pathological Tau during stimulation. In contrast, chronic synaptic activation promoted clearance of Tau oligomers by autophagosomes and lysosomes. Chronic inhibition of synaptic activity resulted in opposite outcomes, with build-up of Tau oligomers in enlarged auto-lysosomes. Our data indicate that synaptic activity counteracts the negative effects of Tau in AD and FTD by acting on autophagy, providing a rationale for therapeutic use of DBS and synaptic stimulation in tauopathies.

Interleukin-1β Activates a MYC-Dependent Metabolic Switch in Kidney Stromal Cells Necessary for Progressive Tubulointerstitial Fibrosis

Background Kidney injury is characterized by persisting inflammation and fibrosis, yet mechanisms by which inflammatory signals drive fibrogenesis remain poorly defined.Methods RNA sequencing of fibrotic kidneys from patients with CKD identified a metabolic gene signature comprising loss of mitochondrial and oxidative phosphorylation gene expression with a concomitant increase in regulators and enzymes of glycolysis under the control of PGC1α and MYC transcription factors, respectively. We modeled this metabolic switch in vivo, in experimental murine models of kidney injury, and in vitro in human kidney stromal cells (SCs) and human kidney organoids.Results In mice, MYC and the target genes thereof became activated in resident SCs early after kidney injury, suggesting that acute innate immune signals regulate this transcriptional switch. In vitro, stimulation of purified human kidney SCs and human kidney organoids with IL-1β recapitulated the molecular events observed in vivo, inducing functional metabolic derangement characterized by increased MYC-dependent glycolysis, the latter proving necessary to drive proliferation and matrix production. MYC interacted directly with sequestosome 1/p62, which is involved in proteasomal degradation, and modulation of p62 expression caused inverse effects on MYC expression. IL-1β stimulated autophagy flux, causing degradation of p62 and accumulation of MYC. Inhibition of the IL-1R signal transducer kinase IRAK4 in vivo or inhibition of MYC in vivo as well as in human kidney organoids in vitro abrogated fibrosis and reduced tubular injury.Conclusions Our findings define a connection between IL-1β and metabolic switch in fibrosis initiation and progression and highlight IL-1β and MYC as potential therapeutic targets in tubulointerstitial diseases.

Nerve growth factor-induced Akt/mTOR activation protects the ischemic heart via restoring autophagic flux and attenuating ubiquitinated protein accumulation

The dysregulation of autophagy is related to a variety of cardiovascular diseases, such as myocardial ischemia/reperfusion (I/R). Nerve growth factor (NGF) has been shown to have therapeutic potential in ischaemic heart injury. In this study, we demonstrate that NGF administration can accelerate autophagic flux and attenuate protein ubiquitination in myocardial I/R heart. Our results showed that NGF could restored heart function and decreased the apoptosis of cardiomyocytes which induced by myocardial I/R injury. The protective effect of NGF is associated with the inhibition of autophagy related proteins. On another hand, NGF enhances the clearance of ubiquitinated protein and increases the survival of myocardial cell in vivo and in vitro. Additionally, NGF could activate the PI3K/AKT and mTOR signaling pathways. These results suggested that the cardioprotective effect of NGF is related to the restoration of autophagic flux and attenuation of protein ubiquitination via the activation of PI3K/AKT and mTOR pathway.

Cardiac fibrosis in mouse expressing DsRed tetramers involves chronic autophagy and proteasome degradation insufficiency

Proteinopathy in the heart which often manifests excessive misfolded/aggregated proteins in cardiac myocytes can result in severe fibrosis and heart failure. Here we developed a mouse model, which transgenically express tetrameric DsRed, a red fluorescent protein (RFP), in an attempt to mimic the pathological mechanisms ofcardiac fibrosis. Whilst DsRed is expressed and forms aggregation in most mouse organs, certain pathological defects are specifically recapitulated in cardiac muscle cells including mitochondria damages, aggresome-like residual bodies, excessive ubiquitinated proteins, and the induction of autophagy. The proteinopathy and cellular injuries caused by DsRed aggregates may be due to impaired or overburdened ubiquitin-proteasome system and autophagy-lysosome systems. We further identified that DsRed can be ubiquitinated and associated with MuRF1, a muscle-specific E3 ligase. Concomitantly, an activation of NF-κB signaling and a strong TIMP1 induction were noted, suggesting that RFP-induced fibrosis was augmented by a skewed balance between TIMP1 and MMPs. Taken together, our study highlights the molecular consequences of uncontrolled protein aggregation leading to congestive heart failure, and provides novel insights into fibrosis formation that can be exploited for improved therapy.

Impaired Protein Quality Control During Left Ventricular Remodeling in Mice With Cardiac Restricted Overexpression of Tumor Necrosis Factor

BACKGROUND

Sustained inflammation in the heart is sufficient to provoke left ventricular dysfunction and left ventricular remodeling. Although inflammation has been linked to many of the biological changes responsible for adverse left ventricular remodeling, the relationship between inflammation and protein quality control in the heart is not well understood.

METHODS AND RESULTS

To study the relationship between chronic inflammation and protein quality control, we used a mouse model of dilated cardiomyopathy driven by cardiac restricted overexpression of TNF (tumor necrosis factor; Myh6-sTNF). Myh6-sTNF mice develop protein aggregates containing ubiquitin-tagged proteins within cardiac myocytes related to proteasome dysfunction and impaired autophagy. The 26S proteasome was dysfunctional despite normal function of the core 20S subunit. We found an accumulation of autophagy substrates in Myh6-sTNF mice, which were also seen in tissue from patients with end-stage heart failure. Moreover, there was evidence of impaired autophagosome clearance after chloroquine administration in these mice indicative of impaired autophagic flux. Finally, there was increased mammalian target of rapamycin complex 1 (mTORC1) activation, which has been linked to inhibition of both the proteasome and autophagy.

CONCLUSIONS

Myh6-sTNF mice with sustained inflammatory signaling develop proteasome dysfunction and impaired autophagic flux that is associated with enhanced mTORC1 activation.

The TRPV1 ion channel regulates thymocyte differentiation by modulating autophagy and proteasome activity

Autophagy and the ubiquitin-proteasome system (UPS) control thymus cell homeostasis under resting and endoplasmic reticulum (ER) stress conditions. Several evidence support a cross-talk between UPS and autophagy; abrogation of UPS responses stimulates autophagy, and vice versa the inhibition of autophagy alters the UPS functions.

Herein, we found that TRPV1 activation induces ER stress, proteasome dysfunction and autophagy in thymocytes by modulating the expression of UPR-related genes. The TRPV1-mediated autophagy prevents the UPR activation by inhibiting BiP, Grp94 and ERp57 chaperone protein expression.

Thymocytes from TRPV1 KO mice display both autophagy and proteasome dysfunctions, resulting in increased apoptotic cells and reduced total DP thymocyte number.

In addition, positive selection of thymocytes triggered by anti-TCRβ/CD2 Ab-mediated costimulation induces apoptosis in thymocytes from TRPV1 KO as compared with WT mice. Stimulation of TRPV1 KO thymocytes with anti-TCRβ/CD2 mAbs modulates the expression of CD4 antigen on purified DP thymocytes, with reduced number of mature, single positive (SP) CD4 and increased number of immature SP CD4^low and DP CD4^lowCD8⁺ thymocytes, further supporting the intrinsic role of TRPV1 in T cell maturation. Finally, a reduction in CD8⁺ and CD4⁺ T cells is evidenced in the peripheral blood and spleen of TRPV1 KO, as compared with WT mice. Therapeutic strategy by restraining or stimulating the TRPV1 expression and functions in thymocytes might represent a new pharmacological tool in the regulation of different inflammatory T cell responses.

Effect of treadmill exercise on skeletal muscle autophagy in rats with obesity induced by a high-fat diet

[Purpose]

This study aimed to investigate the effects of treadmill exercise on body weight, blood biochemistry, and autophagy.

[Methods]

Triglyceride, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, insulin, and glucose levels were measured, the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) score was calculated, and the soleus muscle was analyzed for autophagy-related factors (Beclin-1, p62, LC3, Lamp-2) in rats with obesity induced by a high-fat diet. Eight-week-old Sprague Dawley rats were fed a high-fat diet for 35 weeks and then subjected to 10 weeks of treadmill exercise. The experimental group was divided into a Normal Diet-Sedentary (ND-SED, n=8) group, an (High-Fat Diet-Sedentary (HF-SED, n=8) group, and an High-Fat Diet + Treadmill Exercise (HF-TE, n=8) group. The intensity of treadmill exercise was set as 8 m/min for 5 min, 11 m/min for 5 min, 15 m/min for 20 min, and 11 m/min for the last 5 minutes. A glucose tolerance test was performed at the 2nd and 8th week of exercise by sampling of tail blood.

[Results]

With endurance exercise, the HFTE group showed a significant decrease in body weight, with improved blood biochemical indices and HOMA-IR scores, in comparison with the HF-SED group. However, there was no significant difference in Beclin-1, p62, LC3, and Lamp-2 proteins as measured by autophagic flux in the soleus muscle.

[Conclusion]

Treadmill exercise induced improvements in body weight, body fat, and biochemical indicators of obesity and Type 2 diabetes, but had no effect on autophagy in soleus muscle.

Roles of Autophagy in Ischemic Heart Diseases and the Modulatory Effects of Chinese Herbal Medicine

Autophagy is an evolutionarily conserved degradation process which eliminates dysfunctional proteins and cytoplasmic components to maintain homeostasis for cell survival. Increasing evidence has demonstrated the modulatory role of autophagy in ischemic heart diseases (IHDs). Traditionally, this process has been recognized as having protective functions, such as inhibiting atherosclerosis progression and reducing cell death during the ischemic phase. However, recent studies have suggested its dual roles in myocardial ischemia/reperfusion (MIR) injury. Excessive autophagy may play a deleterious role in cardiac function, due to overwhelming clearance of cellular constituents and proteins. Hence modulation of autophagy to increase cardiomyocyte survival and improve cardiac function is meaningful for the treatment of IHD. Chinese herbal medicine, including extractive compounds and patented drugs, has shown its potential role in treating IHD by addressing autophagy-related mechanisms. This review summarizes the updated knowledge on the molecular basis and modulatory role of autophagy in IHD and the recent progress of Chinese herbal medicine in its treatment.

Autophagy modulation: a potential therapeutic approach in cardiac hypertrophy

Autophagy is an evolutionarily conserved process used by the cell to degrade cytoplasmic contents for quality control, survival for temporal energy crisis, and catabolism and recycling. Rapidly increasing evidence has revealed an important pathogenic role of altered activity of the autophagosome-lysosome pathway (ALP) in cardiac hypertrophy and heart failure. Although an early study suggested that cardiac autophagy is increased and that this increase is maladaptive to the heart subject to pressure overload, more recent reports have overwhelmingly supported that myocardial ALP insufficiency results from chronic pressure overload and contributes to maladaptive cardiac remodeling and heart failure. This review examines multiple lines of preclinical evidence derived from recent studies regarding the role of autophagic dysfunction in pressure-overloaded hearts, attempts to reconcile the discrepancies, and proposes that resuming or improving ALP flux through coordinated enhancement of both the formation and the removal of autophagosomes would benefit the treatment of cardiac hypertrophy and heart failure resulting from chronic pressure overload.

p62 improves AD-like pathology by increasing autophagy

The multifunctional protein p62 is associated with neuropathological inclusions in several neurodegenerative disorders, including frontotemporal lobar degeneration, amyotrophic lateral sclerosis and Alzheimer's disease (AD). Strong evidence shows that in AD, p62 immunoreactivity is associated with neurofibrillary tangles and is involved in tau degradation. However, it remains to be determined whether p62 also plays a role in regulating amyloid-β (Aβ) aggregation and degradation. Using a gene therapy approach, here we show that increasing brain p62 expression rescues cognitive deficits in APP/PS1 mice, a widely used animal model of AD. The cognitive improvement was associated with a decrease in Aβ levels and plaque load. Using complementary genetic and pharmacologic approaches, we found that the p62-mediated changes in Aβ were due to an increase in autophagy. To this end, we showed that removing the LC3-interacting region of p62, which facilitates p62-mediated selective autophagy, or blocking autophagy with a pharmacological inhibitor, was sufficient to prevent the decrease in Aβ. Overall, we believe these data provide the first direct in vivo evidence showing that p62 regulates Aβ turnover.

p62 links the autophagy pathway and the ubiqutin-proteasome system upon ubiquitinated protein degradation

The ubiquitin–proteasome system (UPS) and autophagy are two distinct and interacting proteolytic systems. They play critical roles in cell survival under normal conditions and during stress. An increasing body of evidence indicates that ubiquitinated cargoes are important markers of degradation. p62, a classical receptor of autophagy, is a multifunctional protein located throughout the cell and involved in many signal transduction pathways, including the Keap1–Nrf2 pathway. It is involved in the proteasomal degradation of ubiquitinated proteins. When the cellular p62 level is manipulated, the quantity and location pattern of ubiquitinated proteins change with a considerable impact on cell survival. Altered p62 levels can even lead to some diseases. The proteotoxic stress imposed by proteasome inhibition can activate autophagy through p62 phosphorylation. A deficiency in autophagy may compromise the ubiquitin–proteasome system, since overabundant p62 delays delivery of the proteasomal substrate to the proteasome despite proteasomal catalytic activity being unchanged. In addition, p62 and the proteasome can modulate the activity of HDAC6 deacetylase, thus influencing the autophagic degradation.

A strategy to combine pathway-targeted low toxicity drugs in ovarian cancer

Serous Ovarian Cancers (SOC) are frequently resistant to programmed cell death. However, here we describe that these programmed death-resistant cells are nonetheless sensitive to agents that modulate autophagy. Cytotoxicity is not dependent upon apoptosis, necroptosis, or autophagy resolution. A screen of NCBI yielded more than one dozen FDA-approved agents displaying perturbed autophagy in ovarian cancer. The effects were maximized via combinatorial use of the agents that impinged upon distinct points of autophagy regulation. Autophagosome formation correlated with efficacy in vitro and the most cytotoxic two agents gave similar effects to a pentadrug combination that impinged upon five distinct modulators of autophagy. However, in a complex in vivo SOC system, the pentadrug combination outperformed the best two, leaving trace or no disease and with no evidence of systemic toxicity. Targeting the autophagy pathway in a multi-modal fashion might therefore offer a clinical option for treating recalcitrant SOC.

Nelfinavir is effective against human cervical cancer cells in vivo: a potential treatment modality in resource-limited settings

Objective

The standard treatment for cervical cancer in developed countries includes surgery and chemoradiation, with standard of care lagging in developing countries. Even in the former case, treatment frequently yields recalcitrant tumors and women succumb to disease. Here we examine the impact of nelfinavir, an off-patent viral protease inhibitor, which has shown promise as an antineoplastic agent.

Methods

We evaluated the morphological and proliferative effects of the autophagy-stressing drug nelfinavir in normal and cisplatin-resistant cervical cancer cells. Immunofluorescent validation of autophagy markers was performed and the impact of nelfinavir in an in vivo model of tumor growth was determined.

Results

Nelfinavir exhibits cytotoxicity against both cisplatin-sensitive and -resistant ME-180 human cervical cancer cells in vitro and in vivo. Immunoblotting and immunofluorescence showed an expression of the autophagy marker LC3-II in response to nelfinavir treatment.

Conclusion

Nelfinavir, now available as an inexpensive generic orally dosed agent (Nelvir), is cytotoxic against cervical cancer cells. It acts by burdening the autophagy pathway to impair tumor cell survival and a modest induction of apoptosis. While further studies are needed to elucidate the optimal method of application of nelfinavir, it may represent an appealing global option for the treatment of cervical cancer.

Phospholamban p.Arg14del cardiomyopathy is characterized by phospholamban aggregates, aggresomes, and autophagic degradation

AIMS

The non-desmosomal phospholamban PLN p.Arg14del mutation was identified in patients diagnosed with dilated cardiomyopathy (DCM) and/or arrhythmogenic cardiomyopathy (ACM). We aimed to investigate whether this mutation leads to aggregation, aggresome formation and autophagy of mutant PLN protein.

METHODS AND RESULTS

We studied 20 complete heart specimens of PLN p.Arg14del mutation carriers [mean age 48 ± 15 years; 55% males], either from autopsies or from explants. Gross and microscopic examination showed biventricular cardiomyopathy with histopathological features of both ACM and DCM, i.e. a combination of fibrofatty replacement and interstitial fibrosis. Immunohistochemistry for PLN showed large perinuclear PLN protein aggregates in cardiomyocytes in both ventricles in all examined hearts. The median numbers of PLN-containing aggregates were 12 per 5 mm(2) range 3-48 mm2 in right ventricular myocardium and 13 per 5 mm(2) (range 5-89 mm(2) ) in left ventricular myocardium. Double immunohistochemical staining showed colocalization of autophagy markers p62 (sequestosome-1) and microtubule-associated protein light chain 3 with PLN in all aggregates, suggestive of degradation by selective autophagy. On electron microscopy, the ultrastructural appearance of these PLN-containing aggregates was typical of aggresomes; they were not surrounded by a membrane, and were located adjacent to the microtubular organizing centre. PLN-containing aggregates were not found in 10 PLN-negative cases of idiopathic and genetic DCM or in seven cases of desmosomal ACM.

CONCLUSIONS

PLN p.Arg14del cardiomyopathy is a biventricular cardiomyopathy characterized by large perinuclear PLN protein aggregates with a typical ultrastructural appearance of aggresomes. PLN detected by immunohistochemistry appears to be a sensitive and specific marker for this disease.

CXC chemokine receptor 3 promotes steatohepatitis in mice through mediating inflammatory cytokines, macrophages and autophagy

BACKGROUND & AIMS

CXC chemokine receptor 3 (CXCR3) is involved in virus-related chronic liver inflammation. However, the role of CXCR3 in non-alcoholic steatohepatitis (NASH) remains unclear. We aimed to investigate the role of CXCR3 in NASH.

METHODS

Human liver tissues were obtained from 24 non-alcoholic fatty liver disease (NAFLD) patients and 20 control subjects. CXCR3 knockout (CXCR3(-/-)), obese db/db mice and their wild-type (WT) littermates were used in both methionine-and-choline-deficient (MCD) diet and high-fat high-carbohydrate high-cholesterol (HFHC) diet-induced NASH models. In addition, MCD-fed WT mice were administrated with CXCR3 specific antagonists.

RESULTS

CXCR3 was significantly upregulated in liver tissues of patients with NAFLD and in dietary-induced NASH animal models. Compared with WT littermates, CXCR3(-/-) mice were more resistant to both MCD and HFHC diet-induced steatohepatitis. Induction of CXCR3 in dietary-induced steatohepatitis was associated with the increased expression of hepatic pro-inflammatory cytokines, activation of NF-κB, macrophage infiltration and T lymphocytes accumulation (Th1 and Th17 immune response). CXCR3 was also linked to steatosis through inducing hepatic lipogenic genes. Moreover, CXCR3 is associated with autophagosome-lysosome impairment and endoplasmic reticulum (ER) stress in steatohepatitis as evidenced by LC3-II and p62/SQSTM1 accumulation and the induction of GRP78, phospho-PERK and phospho-eIF2α. Inhibition of CXCR3 using CXCR3 antagonist significantly suppressed MCD-induced steatosis and hepatocytes injury in AML-12 hepatocytes. Blockade of CXCR3 using CXCR3 antagonists in mice reversed the established steatohepatitis.

CONCLUSIONS

CXCR3 plays a pivotal role in NASH development by inducing production of cytokines, macrophage infiltration, fatty acid synthesis and causing autophagy deficiency and ER stress.

Defects in retinal pigment epithelial cell proteolysis and the pathology associated with age-related macular degeneration

Maintenance of protein homeostasis, also referred to as "Proteostasis", integrates multiple pathways that regulate protein synthesis, folding, translocation, and degradation. Failure in proteostasis may be one of the underlying mechanisms responsible for the cascade of events leading to age-related macular degeneration (AMD). This review covers the major degradative pathways (ubiquitin-proteasome and lysosomal involvement in phagocytosis and autophagy) in the retinal pigment epithelium (RPE) and summarizes evidence of their involvement in AMD. Degradation of damaged and misfolded proteins via the proteasome occurs in coordination with heat shock proteins. Evidence of increased content of proteasome and heat shock proteins in retinas from human donors with AMD is consistent with increased oxidative stress and extensive protein damage with AMD. Phagocytosis and autophagy share key molecules in phagosome maturation as well as degradation of their cargo following fusion with lysosomes. Phagocytosis and degradation of photoreceptor outer segments ensures functional integrity of the neural retina. Autophagy rids the cell of toxic protein aggregates and defective mitochondria. Evidence suggesting a decline in autophagic flux includes the accumulation of autophagic substrates and damaged mitochondria in RPE from AMD donors. An age-related decrease in lysosomal enzymatic activity inhibits autophagic clearance of outer segments, mitochondria, and protein aggregates, thereby accelerating the accumulation of lipofuscin. This cumulative damage over a person's lifetime tips the balance in RPE from a state of para-inflammation, which strives to restore cell homeostasis, to the chronic inflammation associated with AMD.

To beat or not to beat: degradation of Cx43 imposes the heart rhythm

The main function of the heart is to pump blood to the different parts of the organism, a task that is efficiently accomplished through proper electric and metabolic coupling between cardiac cells, ensured by gap junctions (GJ). Cardiomyocytes are the major cell population in the heart, and as cells with low mitotic activity, are highly dependent upon mechanisms of protein degradation. In the heart, both the ubiquitin-proteasome system (UPS) and autophagy participate in the fine-tune regulation of cardiac remodelling and function, either in physiological or pathological conditions. Indeed, besides controlling cardiac signalling pathways, UPS and autophagy have been implicated in the turnover of several myocardial proteins. Degradation of Cx43, the major ventricular GJ protein, has been associated to up-regulation of autophagy at the onset of heart ischemia and ischemia/reperfusion (I/R), which can have profound implications upon cardiac function. In this review, we present recent studies devoted to the involvement of autophagy and UPS in heart homoeostasis, with a particular focus on GJ.

bFGF regulates autophagy and ubiquitinated protein accumulation induced by myocardial ischemia/reperfusion via the activation of the PI3K/Akt/mTOR pathway

Autophagy is involved in the development and/or progression of many diseases, including myocardial ischemia/reperfusion (I/R). In this study, we hypothesized a protective role of basic fibroblast growth factor (bFGF) both in vivo and in vitro and demonstrated that excessive autophagy and ubiquitinated protein accumulation is involved in the myocardial I/R model. Our results showed that bFGF improved heart function recovery and increased the survival of cardiomyocytes in myocardial I/R model. The protective effect of bFGF is related to the inhibition of LC3II levels. Additionally, bFGF enhances the clearance of Ub by p62 and increases the survival of H9C2 cells. Moreover, silencing of p62 partially blocks the clearance of Ub and abolishes the anti-apoptosis effect of bFGF. An shRNA against the autophagic machinery Atg7 increased the survival of H9C2 cells co-treated with bFGF and rapamycin. bFGF activates the downstream signaling of the PI3K/Akt/mTOR pathway. These results indicate that the role of bFGF in myocardial I/R recovery is related to the inhibition of excessive autophagy and increased ubiquitinated protein clearance via the activation of PI3K/Akt/mTOR signaling. Overall, our study suggests a new direction for bFGF drug development for heart disease and identifies protein signaling pathways involved in bFGF action.

Autophagy and ubiquitination in cardiovascular diseases

A main function of the heart is to pump blood to the tissues and organs of the body. Although formed by different types of cells, the cardiomyocytes are the ones responsible for the coordinated and synchronized heart contraction. Given their low mitotic activity, cardiomyocytes largely depend on protein degradation mechanisms to maintain proteostasis and energetic balance. Autophagy, one of the main pathways whereby cells eliminate damaged, nonfunctional, or obsolete proteins, and organelles, is vital to ensure cell function, including in cardiomyocytes, both in rest and stress conditions. However, the impact of autophagy activation in the heart, being either protective or harmful, is not consensual and likely depends upon the severity of the stimuli and consequently the autophagy players involved. One of the signals that direct proteins for autophagy degradation, namely in the context of heart disorders, is ubiquitin. Indeed, the attachment of ubiquitin moieties to a target substrate and further recognition by autophagy adaptors constitute a main regulatory pathway that directs proteins to the lysosome. Therefore, a better understanding of the mechanisms and signals that regulate the autophagy process in the heart, including substrates targeting, is of utmost importance to design new approaches directed to this degradation pathway. We have previously shown that ubiquitination of the gap junction (GJ) protein Connexin43 (Cx43) triggers its degradation by autophagy through a process that requires the ubiquitin adaptors epidermal growth factor receptor substrate 15 (Eps15) and p62. This is particularly relevant in the heart because GJs, that form intercellular channels, are responsible for the rapid and efficient anisotropic propagation of the electrical impulse through the cardiomyocytes, essential for synchronized contraction of the cardiac muscle. In this review, we present recent studies devoted to the involvement of autophagy in heart homeostasis, with a particular focus on ubiquitin and GJs.

Clusterin facilitates stress-induced lipidation of LC3 and autophagosome biogenesis to enhance cancer cell survival

We define stress-induced adaptive survival pathways linking autophagy with the molecular chaperone clusterin (CLU) that function to promote anticancer treatment resistance. During treatment stress, CLU co-localizes with LC3 via an LIR-binding sequence within autophagosome membranes, functioning to facilitate LC3–Atg3 heterocomplex stability and LC3 lipidation, and thereby enhance autophagosome biogenesis and autophagy activation. Stress-induced autophagy is attenuated with CLU silencing in CLU^−/− mice and human prostate cancer cells. CLU-enhanced cell survival occurs via autophagy-dependent pathways, and is reduced following autophagy inhibition. Combining CLU inhibition with anticancer treatments attenuates autophagy activation, increases apoptosis and reduces prostate cancer growth. This study defines a novel adaptor protein function for CLU under stress conditions, and highlights how co-targeting CLU and autophagy can amplify proteotoxic stress to delay cancer progression.

The induction of autophagy under stress conditions such as chemotherapy is a contributing factor towards resistance to anticancer therapy. Here, Zhang et al. identify the molecular chaperone clusterin as an adaptor that facilitates lipidation of LC3 and autophagosome biogenesis.