Current questions and possible controversies in autophagy

Unraveling molecular aberrations and pioneering therapeutic strategies in osteosarcoma

Osteosarcoma, a rare primary bone cancer, presents diverse molecular aberrations that underscore its complexity. Despite the persistent endeavors by researchers, the limited amelioration in the five-year survival rate indicates that current therapeutic strategies prove inadequate in addressing the clinical necessities. Advancements in molecular profiling have facilitated an enhanced comprehension of the biology of osteosarcoma, offering a promising outlook for treatment. There is an urgent need to develop innovative approaches to address the complex challenges of osteosarcoma, ultimately contributing to enhanced patient outcomes. This review explores the nexus between osteosarcoma and cancer predisposition syndromes, intricacies in its somatic genome, and clinically actionable alterations. This review covers treatment strategies, including surgery, chemotherapy, immune checkpoint inhibitors (ICIs), and tyrosine kinase inhibitors (TKIs). Innovative treatment modalities targeting diverse pathways, including multi-target tyrosine kinases, cell cycle, PI3K/mTOR pathway, and DNA damage repair (DDR), offer promising interventions. This review also covers promising avenues, including antibody-drug conjugates (ADCs) and immunotherapy strategies, such as cytokines, adoptive cellular therapy (ACT), ICIs, and cancer vaccines. This comprehensive exploration contributes to a holistic understanding, offering guidance for clinical applications to advance the management of osteosarcoma.

Therapeutic strategies of targeting non-apoptotic regulated cell death (RCD) with small-molecule compounds in cancer

Regulated cell death (RCD) is a controlled form of cell death orchestrated by one or more cascading signaling pathways, making it amenable to pharmacological intervention. RCD subroutines can be categorized as apoptotic or non-apoptotic and play essential roles in maintaining homeostasis, facilitating development, and modulating immunity. Accumulating evidence has recently revealed that RCD evasion is frequently the primary cause of tumor survival. Several non-apoptotic RCD subroutines have garnered attention as promising cancer therapies due to their ability to induce tumor regression and prevent relapse, comparable to apoptosis. Moreover, they offer potential solutions for overcoming the acquired resistance of tumors toward apoptotic drugs. With an increasing understanding of the underlying mechanisms governing these non-apoptotic RCD subroutines, a growing number of small-molecule compounds targeting single or multiple pathways have been discovered, providing novel strategies for current cancer therapy. In this review, we comprehensively summarized the current regulatory mechanisms of the emerging non-apoptotic RCD subroutines, mainly including autophagy-dependent cell death, ferroptosis, cuproptosis, disulfidptosis, necroptosis, pyroptosis, alkaliptosis, oxeiptosis, parthanatos, mitochondrial permeability transition (MPT)-driven necrosis, entotic cell death, NETotic cell death, lysosome-dependent cell death, and immunogenic cell death (ICD). Furthermore, we focused on discussing the pharmacological regulatory mechanisms of related small-molecule compounds. In brief, these insightful findings may provide valuable guidance for investigating individual or collaborative targeting approaches towards different RCD subroutines, ultimately driving the discovery of novel small-molecule compounds that target RCD and significantly enhance future cancer therapeutics.

Plausible Role of Mitochondrial DNA Copy Number in Neurodegeneration-a Need for Therapeutic Approach in Parkinson's Disease (PD)

Parkinson's disease (PD) is an advancing age-associated progressive brain disorder which has various diverse factors, among them mitochondrial dysfunction involves in dopaminergic (DA) degeneration. Aging causes a rise in mitochondrial abnormalities which leads to structural and functional modifications in neuronal activity and cell death in PD. This ends in deterioration of mitochondrial function, mitochondrial alterations, mitochondrial DNA copy number (mtDNA CN) and oxidative phosphorylation (OXPHOS) capacity. mtDNA levels or mtDNA CN in PD have reported that mtDNA depletion would be a predisposing factor in PD pathogenesis. To maintain the mtDNA levels, therapeutic approaches have been focused on mitochondrial biogenesis in PD. The depletion of mtDNA levels in PD can be influenced by autophagic dysregulation, apoptosis, neuroinflammation, oxidative stress, sirtuins, and calcium homeostasis. The current review describes the regulation of mtDNA levels and discusses the plausible molecular pathways in mtDNA CN depletion in PD pathogenesis. We conclude by suggesting further research on mtDNA depletion which might show a promising effect in predicting and diagnosing PD.

Regulation of Autophagy via Carbohydrate and Lipid Metabolism in Cancer

Metabolic changes are an important component of tumor cell progression. Tumor cells adapt to environmental stresses via changes to carbohydrate and lipid metabolism. Autophagy, a physiological process in mammalian cells that digests damaged organelles and misfolded proteins via lysosomal degradation, is closely associated with metabolism in mammalian cells, acting as a meter of cellular ATP levels. In this review, we discuss the changes in glycolytic and lipid biosynthetic pathways in mammalian cells and their impact on carcinogenesis via the autophagy pathway. In addition, we discuss the impact of these metabolic pathways on autophagy in lung cancer.

Mapping autophagosome contents identifies interleukin-7 receptor-α as a key cargo modulating CD4+ T cell proliferation

CD4+ T cells are pivotal cells playing roles in the orchestration of humoral and cytotoxic immune responses. It is known that CD4+ T cell proliferation relies on autophagy, but identification of the autophagosomal cargo involved is missing. Here we create a transgenic mouse model, to enable direct mapping of the proteinaceous content of autophagosomes in primary cells by LC3 proximity labelling. Interleukin-7 receptor-α, a cytokine receptor mostly found in naïve and memory T cells, is reproducibly detected in autophagosomes of activated CD4+ T cells. Consistently, CD4+ T cells lacking autophagy show increased interleukin-7 receptor-α surface expression, while no defect in internalisation is observed. Mechanistically, excessive surface interleukin-7 receptor-α sequestrates the common gamma chain, impairing the interleukin-2 receptor assembly and downstream signalling crucial for T cell proliferation. This study shows that key autophagy substrates can be reliably identified in this mouse model and help mechanistically unravel autophagy's contribution to healthy physiology and disease.

The molecular mechanisms of vulpinic acid induced programmed cell death in melanoma

BACKGROUNDS

Malignant melanoma is an aggressive skin tumor with a rapidly increasing incidence and there is not yet a successful treatment strategy. Vulpinic acid (VA) is derived from secondary metabolites from lichen species. In the current study, we, for the first time, investigated the anti-cancer effects of VA and the underlying mechanism VA induced programmed cell death in melanoma.

METHODS

The anti-cancer effects of VA on melanoma cells were evaluated by the xCELLigence system, flow cytometry, caspase-3 activity and RT-PCR analysis.

RESULTS

Our results showed that VA had a strong anti-proliferative effect on A-375 melanoma cells without damaging human epidermal melanocyte cells. Additionally, VA promoted apoptotic cell death through G2/M arrest and the activation of both intrinsic and extrinsic apoptosis pathways according to the analysis of 88 genes associated with apoptosis by qRT-PCR.

CONCLUSIONS

Our findings suggest that VA could become an alternative topical and transdermal treatment strategy in the treatment of maligned melanoma cancer. However, further investigations are needed to assess the underlying molecular mechanism of VA mediated apoptotic cell death in the treatment of melanoma.

An Overview of Autophagy in Hematopoietic Stem Cell Transplantation

Autophagy is a fundamental homeostatic process crucial for cellular adaptation in response to metabolic stress. Autophagy exerts its effect through degrading intracellular components and recycling them to produce macromolecular precursors and energy. This physiological process contributes to cellular development, maintenance of cellular/tissue homeostasis, immune system regulation, and human disease. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only preferred therapy for most bone marrow-derived cancers. Unfortunately, HSCT can result in several serious and sometimes untreatable conditions due to graft-versus-host disease (GVHD), graft failure, and infection. These are the major cause of morbidity and mortality in patients receiving the transplant. During the last decade, autophagy has gained a considerable understanding of its role in various diseases and cellular processes. In light of recent research, it has been confirmed that autophagy plays a crucial role in the survival and function of hematopoietic stem cells (HSCs), T-cell differentiation, antigen presentation, and responsiveness to cytokine stimulation. Despite the importance of these events to HSCT, the role of autophagy in HSCT as a whole remains relatively ambiguous. As a result of the growing use of autophagy-modulating agents in the clinic, it is imperative to understand how autophagy functions in allogeneic HSCT. The purpose of this literature review is to elucidate the established and implicated roles of autophagy in HSCT, identifying this pathway as a potential therapeutic target for improving transplant outcomes.

Hsa-miR-30a-3p overcomes the acquired protective autophagy of bladder cancer in chemotherapy and suppresses tumor growth and muscle invasion

Bladder cancer (BC) is the second most common urologic cancer in western countries. New strategies for managing high-grade muscle-invasive bladder cancer (MIBC) are urgently required because MIBC has a high risk of recurrence and poor survival. A growing body of evidence indicates that microRNA has potent antitumorigenic properties in various cancers, and thus, therapeutic strategies based on microRNA may show promising results in cancer therapy. Analysis of The Cancer Genome Atlas (TCGA) database indicated that hsa-miR-30a-3p is downregulated in human BC. Our in vitro investigation demonstrated that hsa-miR-30a-3p suppresses the expression of matrix metalloproteinase-2 (MMP-2) and MMP-9 and reduces the cell invasive potential of BC cells. Furthermore, hsa-miR-30a-3p directly targets ATG5, ATG12, and Beclin 1; this in turn improves the chemosensitivity of BC cells to cisplatin through the repression of protective autophagy. In a tumor-xenograft mice model, hsa-miR-30a-3p suppressed muscle invasion. Cotreatment with hsa-miR-30a-3p enhanced the antitumor effect of cisplatin in reducing tumor growth in BC. The current study provides a novel strategy of using hsa-miR-30a-3p as an adjuvant or replacement therapy in future BC treatment.

Integrated Metabolomics and Network Pharmacology to Establish the Action Mechanism of Qingrekasen Granule for Treating Nephrotic Syndrome

Nephrotic syndrome (NS) is a clinical syndrome resulting from abnormal glomerular permeability, mainly manifesting as edema and proteinuria. Qingrekasen granule (QRKSG), a Chinese Uyghur folk medicine, is a single-flavor preparation made from chicory (Cichorium intybus L.), widely used in treating dysuria and edema. Chicory, the main component in QRKSG, effectively treats edema and protects kidneys. However, the active components in QRKSG and its underlying mechanism for treating NS remain unclear. This study explored the specific mechanism and composition of QRKSG on an NS rat model using integrated metabolomics and network pharmacology. First, metabolomics explored the relevant metabolic pathways impacted by QRKSG in the treatment of NS. Secondly, network pharmacology further explored the possible metabolite targets. Afterward, a comprehensive network was constructed using the results from the network pharmacology and metabolomics analysis. Finally, the interactions between the active components and targets were predicted by molecular docking, and the differential expression levels of the target protein were verified by Western blotting. The metabolomics results showed “D-Glutamine and D-glutamate metabolism” and “Alanine, aspartate, and glutamate metabolism” as the main targeted metabolic pathways for treating NS in rats. AKT1, BCL2L1, CASP3, and MTOR were the core QRKSG targets in the treatment of NS. Molecular docking revealed that these core targets have a strong affinity for flavonoids, terpenoids, and phenolic acids. Moreover, the expression levels of p-PI3K, p-AKT1, p-mTOR, and CASP3 in the QRKSG group significantly decreased, while BCL2L1 increased compared to the model group. These findings established the underlying mechanism of QRKSG, such as promoting autophagy and anti-apoptosis through the expression of AKT1, CASP3, BCL2L1, and mTOR to protect podocytes and maintain renal tubular function.

The roles of GTPase-activating proteins in regulated cell death and tumor immunity

GTPase-activating protein (GAP) is a negative regulator of GTPase protein that is thought to promote the conversion of the active GTPase-GTP form to the GTPase-GDP form. Based on its ability to regulate GTPase proteins and other domains, GAPs are directly or indirectly involved in various cell requirement processes. We reviewed the existing evidence of GAPs regulating regulated cell death (RCD), mainly apoptosis and autophagy, as well as some novel RCDs, with particular attention to their association in diseases, especially cancer. We also considered that GAPs could affect tumor immunity and attempted to link GAPs, RCD and tumor immunity. A deeper understanding of the GAPs for regulating these processes could lead to the discovery of new therapeutic targets to avoid pathologic cell loss or to mediate cancer cell death.

Phagophore Closure

Phagophore closure is a critical step during macroautophagy. However, the proteins and mechanisms to regulate this step have been elusive for a long time. In 2017, Rab5 was affirmed to play a role in phagophore closure in yeast. Furthermore, in mammalian cells, ESCRT III was reported to have roles in phagophore closure and mitophagosome closure in vivo in 2018 and 2019, respectively. The role of ESCRT in phagophore closure was confirmed in yeast, both in vivo and in vitro, in 2019. Most importantly, the latter paper found that Atg17 recruited the ESCRT III subunit Snf7 to the phagophore to close it under the control of Rab5. To determine the closure characteristics of autophagosome-like membrane structures in ESCRT mutants, a traditional protease protection assay with immunoblotting was used, accompanied by new techniques that were developed, including immunofluorescence assays, autophagosome completion assays, and the optogenetic closure assay. This study delivered our current understanding of phagophore closure and provided more reference methods to detect membrane closure.

Using Reactome to build an autophagy mechanism knowledgebase

The 21st century has revealed much about the fundamental cellular process of autophagy. Autophagy controls the catabolism and recycling of various cellular components both as a constitutive process and as a response to stress and foreign material invasion. There is considerable knowledge of the molecular mechanisms of autophagy, and this is still growing as new modalities emerge. There is a need to investigate autophagy mechanisms reliably, comprehensively and conveniently. Reactome is a freely available knowledgebase that consists of manually curated molecular events (reactions) organized into cellular pathways (https://reactome.org/). Pathways/reactions in Reactome are hierarchically structured, graphically presented and extensively annotated. Data analysis tools, such as pathway enrichment, expression data overlay and species comparison, are also available. For customized analysis, information can also be programmatically queried. Here, we discuss the curation and annotation of the molecular mechanisms of autophagy in Reactome. We also demonstrate the value that Reactome adds to research by reanalyzing a previously published work on genome-wide CRISPR screening of autophagy components.Abbreviations: CMA: chaperone-mediated autophagy; GO: Gene Ontology; MA: macroautophagy; MI: microautophagy; MTOR: mechanistic target of rapamycin kinase; SQSTM1: sequestosome 1.

Nuclear translocation of ATG5 induces DNA mismatch repair deficiency (MMR-D)/microsatellite instability (MSI) via interacting with Mis18α in colorectal cancer

BACKGROUND AND PURPOSE

It is well known that microsatellite instability-high (MSI-H) is associated with 5-fluorouracil (5-FU) resistance in colorectal cancer. MSI-H is the phenotype of DNA mismatch repair deficiency (MMR-D), mainly occurring due to hypermethylation of MLH1 promoter CpG island. However, the mechanisms of MMR-D/MSI-H are unclear. We aim to investigate the pathway of MMR-D/MSI-H involved in 5-FU resistance.

EXPERIMENTAL APPROACH

Human colorectal cancer specimens were diagnosed for MSI-H by immunohistochemistry and western blotting. Proteome microarray interactome assay was performed to screen nuclear proteins interacting with ATG5. Nuclear ATG5 and ATG5-Mis18α overexpression were analysed in ATG5^high colorectal cancer bearing mice. The methylation assay determined the hypermethylation of hMLH1 promoter CpG island in freshly isolated human colorectal cancer tissue samples and HT29^atg5 and SW480^atg5 cancer cells.

KEY RESULTS

In ATG5^high colorectal cancer patients, 5-FU-based therapy resulted in nuclear translocation of ATG5, leading to MSI-H. Colorectal cancer in Atg5 Tg mice demonstrated 5-FU resistance, compared to Atg5^+/- and WT mice. Proteome microarray assay identified Mis18α, a protein localized on the centromere and a source for methylation of the underlying chromatin, which responded to the translocated nuclear ATG5 leading to ATG5-Mis18α conjugate overexpression. This resulted in MLH1 deficiency due to hypermethylation of hMLH1 promoter CpG island, while the deletion of nuclear Mis18α failed to induce ATG5-Mis18α complex and MMR-D/MSI-H.

CONCLUSIONS AND IMPLICATIONS

Nuclear ATG5 resulted in MMR-D/MSI-H through its interaction with Mis18α in ATG5^high colorectal cancer cells. We suggest that ATG5-Mis18α or Mis18α may be a therapeutic target for treating colorectal cancer.

Autophagic Cell Death During Development - Ancient and Mysterious

While cell death is a normal and essential component of development and homeostasis, dysregulation of this process underlies most human diseases, including cancer, autoimmunity and neurodegeneration. The best characterized mechanism for cell death is apoptosis, although some cells die by a distinct process known as autophagy-dependent cell death (ADCD). Autophagy is mediated by the formation of double membrane vesicles that contain protein aggregates, damaged organelles like mitochondria, and bulk cytoplasm, which then fuse with lysosomes to degrade and recycle their contents. Autophagy is typically viewed as an adaptive process that allows cells to survive stresses like nutrient deprivation, although increasing evidence suggests that it may also mediate cell death during development and pathogenesis. An aggressive form of autophagy termed autosis has been described in cells following either ischemia/reperfusion injury or in response to autophagy-inducing proteins like Tat-Beclin 1. Despite an extensive literature on autophagic cell death in a variety of contexts, there are still fundamental gaps in our understanding of this process. As examples: Does autophagy directly kill cells and if so how? Is ADCD activated concurrently when cells are triggered to die via apoptosis? And is ADCD essentially a more protracted version of autosis or a distinct pathway? The goal of this mini-review is to summarize the field and to identify some of the major gaps in our knowledge. Understanding the molecular mechanisms that mediate ADCD will not only provide new insights into development, they may facilitate the creation of better tools for both the diagnostics and treatment of disease.

Rab GTPases in Osteoclastic Bone Resorption and Autophagy

Small guanosine triphosphate hydrolases (GTPases) of the Rab family are involved in plasma membrane delivery, fusion events, and lysosomal and autophagic degradation pathways, thereby regulating signaling pathways and cell differentiation and function. Osteoclasts are bone-resorbing cells that maintain bone homeostasis. Polarized vesicular trafficking pathways result in the formation of the ruffled border, the osteoclast’s resorptive organelle, which also assists in transcytosis. Here, we reviewed the different roles of Rab GTPases in the endomembrane machinery of osteoclasts and in bone diseases caused by the dysfunction of these proteins, with a particular focus on autophagy and bone resorption. Understanding the molecular mechanisms underlying osteoclast-related bone disease development is critical for developing and improving therapies.

Inhibiting autophagy potentiates the antitumor efficacy of Euphorbia royleana for canine mammary gland tumors

Background

Canine mammary gland tumors (cMGTs) are the most common neoplasms in intact female canines and viewed as a suitable model for studying human breast cancers. Euphorbia royleana has been reported to have a variety of antitumor efficacies. We have prepared the crude extracts of E. royleana in ethanol and hexane solvents to evaluate the anti-tumor effects for cMGT in vitro and in vivo.

Results

The results showed that E. royleana could inhibit cell proliferation and colony formation in cMGT cells. The suppression of tumor cell growth resulted from necrosis and cell cycle arrest. Moreover, autophagy appears to play a critical role in E. royleana-mediated cell death by triggering cell apoptosis. The in vivo results also revealed that E. royleana treatment could reduce the size of solid tumors while exhibiting low toxicity in cMGT-bearing nude mice.

Conclusions

The anti-tumor mechanisms of E. royleana were firstly verified to show it would cause autophagic cell death, apoptosis, and cell cycle arrest in canine mammary tumor cells. The in vitro and in vivo findings in the present study revealed E. royleana has potential anticancer effects for the treatment of canine mammary gland tumors.

Estrogen and estrogen receptors chauffeur the sex-biased autophagic action in liver

Autophagy, or cellular self-digestion, is an essential cellular process imperative for energy homeostasis, development, differentiation, and survival. However, the intrinsic factors that bring about the sex-biased differences in liver autophagy are still unknown. In this work, we found that autophagic genes variably expresses in the steroidogenic tissues, mostly abundant in liver, and is influenced by the individual's sexuality. Starvation-induced autophagy in a time-dependent female-dominated manner, and upon starvation, a strong gender responsive circulating steroid-HK2 relation was observed, which highlighted the importance of estrogen in autophagy regulation. This was further confirmed by the enhanced or suppressed autophagy upon estrogen addition (male) or blockage (female), respectively. In addition, we found that estrogen proved to be the common denominator between stress management, glucose metabolism, and autophagic action in female fish. To understand further, we used estrogen receptor (ER)α- and ER-β2-knockout (KO) medaka and found ER-specific differences in sex-biased autophagy. Interestingly, starvation resulted in significantly elevated mTOR transcription (compared with control) in male ERα-KO fish while HK2 and ULK activation was greatly decreased in both KO fish in a female oriented fashion. Later, ChIP analysis confirmed that, NRF2, an upstream regulator of mTOR, only binds to ERα, while both ERα and ERβ2 are effectively pulled down the HK2 and LC3. FIHC data show that, in both ER-KO fish, LC3 nuclear-cytoplasmic transport and its associated pathways involving SIRT1 and DOR were greatly affected. Cumulatively, our data suggest that, ERα-KO strongly affected the early autophagic initiation and altered the LC3 nuclear-cytoplasmic translocation, thereby influencing the sex-biased final autophagosome formation in medaka. Thus, existence of steroid responsive autophagy regulatory-switches and sex-biased steroid/steroid receptor availability influences the gender-skewed autophagy. Expectedly, this study may furnish newer appreciation for gender-specific medicine research and therapeutics.

Autophagy in cancer: Recent advances and future directions

Autophagy is being explored as a potential therapeutic target for enhancing the cytotoxic effects of chemotherapeutic regimens in various malignancies. Autophagy plays a very important role in cancer pathogenesis. Here, we discuss the updates on the modulation of autophagy via dynamic interactions with different organelles and the exploitation of selective autophagy for exploring therapeutic strategies. We further discuss the role of autophagy inhibitors in cancer preclinical and clinical trials, novel autophagy inhibitors, and challenges likely to be faced by clinicians while inducting autophagy modulators in clinical practice.

Molecular Mechanisms Underlying Autophagy-Mediated Treatment Resistance in Cancer

Despite advances in diagnostic tools and therapeutic options, treatment resistance remains a challenge for many cancer patients. Recent studies have found evidence that autophagy, a cellular pathway that delivers cytoplasmic components to lysosomes for degradation and recycling, contributes to treatment resistance in different cancer types. A role for autophagy in resistance to chemotherapies and targeted therapies has been described based largely on associations with various signaling pathways, including MAPK and PI3K/AKT signaling. However, our current understanding of the molecular mechanisms underlying the role of autophagy in facilitating treatment resistance remains limited. Here we provide a comprehensive summary of the evidence linking autophagy to major signaling pathways in the context of treatment resistance and tumor progression, and then highlight recently emerged molecular mechanisms underlying autophagy and the p62/KEAP1/NRF2 and FOXO3A/PUMA axes in chemoresistance.

Molecular mechanism of Helicobacter pylori-induced autophagy in gastric cancer

Helicobacter pylori (H. pylori) is a gram-negative pathogen that colonizes gastric epithelial cells. The drug resistance rates of H. pylori have dramatically increased, causing persistent infections. Chronic infection by H. pylori is a critical cause of gastritis, peptic ulcers and even gastric cancer. In host cells, autophagy is stimulated to maintain cellular homeostasis following intracellular pathogen recognition by the innate immune defense system. However, H. pylori-induced autophagy is not consistent during acute and chronic infection. Therefore, a deeper understanding of the association between H. pylori infection and autophagy in gastric epithelial cells could aid the understanding of the mechanisms of persistent infection and the identification of autophagy-associated therapeutic targets for H. pylori infection. The present review describes the role of H. pylori and associated virulence factors in the induction of autophagy by different signaling pathways during acute infection. Additionally, the inhibition of autophagy in gastric epithelial cells during chronic infection was discussed. The present review summarized H. pylori-mediated autophagy and provided insights into its mechanism of action, suggesting the induction of autophagy as a novel therapeutic target for persistent H. pylori infection.

Atg7-dependent canonical autophagy regulates the degradation of aquaporin 2 in prolonged hypokalemia

Prolonged hypokalemia induces a decrease of urinary concentrating ability via down-regulation of aquaporin 2 (AQP2); however, the precise mechanisms remain unknown. To investigate the role of autophagy in the degradation of AQP2, we generated the principal cell-specific Atg7 deletion (Atg7^Δpc) mice. In hypokalemic Atg7-floxed (Atg7^f/f) mice, huge irregular shaped LC3-positive autophagic vacuoles accumulated mainly in inner medullary collecting duct (IMCD) cells. Total- and pS261-AQP2 were redistributed from apical and subapical domains into these vacuoles, which were not co-localized with RAB9. However, in the IMCD cells of hypokalemic Atg7^Δpc mice, these canonical autophagic vacuoles were markedly reduced, whereas numerous small regular shaped LC3-negative/RAB9-positive non-canonical autophagic vacuoles were observed along with diffusely distributed total- and pS261-AQP2 in the cytoplasm. The immunoreactivity of pS256-AQP2 in the apical membrane of IMCD cells was markedly decreased, and no redistribution was observed in both hypokalemic Atg7^f/f and Atg7^Δpc mice. These findings suggest that AQP2 down regulation in hypokalemia was induced by reduced phosphorylation of AQP2, resulting in a reduction of apical plasma labeling of pS256-AQP2 and degradation of total- and pS261-AQP2 via an LC3/ATG7-dependent canonical autophagy pathway.

Activated MLKL attenuates autophagy following its translocation to intracellular membranes

Necroptosis is an inflammatory form of programmed cell death mediated by the pseudokinase mixed-lineage kinase domain-like protein (MLKL). Upon phosphorylation by receptor-interacting protein kinase-3 (RIPK3), MLKL oligomerizes, and translocates to and disrupts the plasma membrane, thereby causing necroptotic cell lysis. Herein, we show that activation of necroptosis in mouse dermal fibroblasts (MDFs) and HT-29 human colorectal cancer cells results in accumulation of the autophagic marker, lipidated LC3B (also known as MAP1LC3B), in an MLKL-dependent manner. Unexpectedly, the necroptosis-induced increase in lipidated LC3B was due to inhibition of autophagic flux, not the activation of autophagy. Inhibition of autophagy by MLKL correlated with a decrease in autophagosome and/or autolysosome function, and required the association of activated MLKL with intracellular membranes. Collectively, our findings uncover an additional role for the MLKL pseudokinase, namely to inhibit autophagy during necroptosis.

Zinc Transporters and the Progression of Breast Cancers

Zinc (Zn) is an essential heavy metal utilized in numerous biological processes in mammals, including its recently described role as a signaling mediator. The movement of Zn in and out of cells, across membranes, is regulated by two protein families: the zinc-regulated transporter (ZRT), iron-regulated transporter (IRT)-like protein (ZIP) and the Zn transporter (ZnT) families. ZIPs and ZnTs maintain intracellular Zn homeostasis and control important cellular functions through Zn signaling. Recent studies have highlighted the role of Zn transporters and Zn in disease. ZIP6, 7, and 10 contribute to human breast cancer progression. ZIP6 is associated with breast tumor grade, size, and stage, suggesting that it is a potent driving force toward malignancy; ZIP7 plays an important role in tamoxifen-resistant breast cancer cells, and ZIP10 is involved in invasion and metastasis of breast cancer cells. These Zn transporters are key molecules in the malignant process; thus, understanding Zn transporters will lead to novel diagnostic and therapeutic strategies for breast cancer. This review discusses the emerging functional roles of Zn and Zn transporters in breast cancer.

LT-IIc, A Bacterial Type II Heat-Labile Enterotoxin, Induces Specific Lethality in Triple Negative Breast Cancer Cells by Modulation of Autophagy and Induction of Apoptosis and Necroptosis

Triple negative breast cancer (TNBC) remains a serious health problem with poor prognosis and limited therapeutic options. To discover novel approaches to treat TNBC, we screened cholera toxin (CT) and the members of the bacterial type II heat-labile enterotoxin family (LT-IIa, LT-IIb, and LT-IIc) for cytotoxicity in TNBC cells. Only LT-IIc significantly reduced viability of the TNBC cell lines BT549 and MDA-MB-231 (IC₅₀ = 82.32 nM). LT-IIc had no significant cytotoxic effect on MCF10A (IC₅₀ = 2600 nM), a non-tumorigenic breast epithelial cell line, and minimal effects on MCF7 and T47D, ER⁺ cells, or SKBR-3 cells, HER2⁺ cells. LT-IIc stimulated autophagy through inhibition of the mTOR pathway, while simultaneously inhibiting autophagic progression, as seen by accumulation of LC3B-II and p62. Morphologically, LT-IIc induced the formation of enlarged LAMP2+ autolysosomes, which was blocked by co-treatment with bafilomycin A1. LT-IIc induced apoptosis as demonstrated by the increase in caspase 3/7 activity and Annexin V staining. Co-treatment with necrostatin-1, however, demonstrated that the lethal response of LT-IIc is elicited, in part, by concomitant induction of necroptosis. Knockdown of ATG-5 failed to rescue LT-IIc-induced cytotoxicity, suggesting LT-IIc can exert its cytotoxic effects downstream or independently of autophagophore initiation. Collectively, these experiments demonstrate that LT-IIc acts bifunctionally, inducing autophagy, while simultaneously blocking autolysosomal progression in TNBC cells, inducing a specific cytotoxicity in this breast cancer subtype.

Targeted Inhibition of ULK1 Promotes Apoptosis and Suppresses Tumor Growth and Metastasis in Neuroblastoma

Neuroblastoma is the most common extracranial solid malignancy in the pediatric population, accounting for over 9% of all cancer-related deaths in children. Autophagy is a cell self-protective mechanism that promotes tumor cell growth and survival, making it an attractive target for treating cancer. However, the role of autophagy in neuroblastoma tumor growth and metastasis is largely undefined. Here we demonstrate that targeted inhibition of an essential autophagy kinase, unc-51 like autophagy kinase 1 (ULK1), with a recently developed small-molecule inhibitor of ULK1, SBI-0206965, significantly reduces cell growth and promotes apoptosis in SK-N-AS, SH-SY5Y, and SK-N-DZ neuroblastoma cell lines. Furthermore, inhibition of ULK1 by a dominant-negative mutant of ULK1 (dnULK1^K46N) significantly reduces growth and metastatic disease and prolongs survival of mice bearing SK-N-AS xenograft tumors. We also show that SBI-0206965 sensitizes SK-N-AS cells to TRAIL treatment, but not to mTOR inhibitors (INK128, Torin1) or topoisomerase inhibitors (doxorubicin, topotecan). Collectively, these findings demonstrate that ULK1 is a viable drug target and suggest that inhibitors of ULK1 may provide a novel therapeutic option for the treatment of neuroblastoma. Mol Cancer Ther; 17(11); 2365-76. ©2018 AACR.

Detection and Clearance of Damaged Lysosomes by the Endo-Lysosomal Damage Response and Lysophagy

Lysosomal membrane permeabilization or lysosomal rupture is recognized as a common and severe stress condition relevant for infection, cellular degeneration and cancer. However, the cellular response mechanisms that protect cells from the consequences of lysosomal damage and ensure lysosomal quality control and homeostasis have only recently been explored. Key elements of this response involve the specific sensing of the damage followed by extensive modification of the organelles with ubiquitin to mark them for clearance by selective macroautophagy, termed lysophagy. Efficient lysophagy is ensured by additional layers of regulation, including modulation by the ubiquitin-directed AAA-ATPase VCP/p97. Lysophagy shares many features with mitophagy, the macroautophagic removal of damaged mitochondria. This review aims to gather available data from different fields and to define the key steps necessary for sensing and subsequent clearance of damaged lysosomes. We conclude with a discussion of disease implications with a focus on neurodegeneration.

Maternal Glucose Supplementation in a Murine Model of Chorioamnionitis Alleviates Dysregulation of Autophagy in Fetal Brain

Fetal brain injury induced by intrauterine inflammation is a major risk factor for adverse neurological outcomes, including cerebral palsy, cognitive dysfunction, and behavioral disabilities. There are no adequate therapies for neuronal protection to reduce fetal brain injury, especially new strategies that may apply promptly and conveniently. In this study, we explored the effect of maternal glucose administration in a mouse model of intrauterine inflammation at term. Our results demonstrated that maternal glucose supplementation significantly increased survival birth rate and improved the neurobehavioral performance of pups exposed to intrauterine inflammation. Furthermore, we demonstrated that maternal glucose administration improved myelination and oligodendrocyte development in offspring exposed to intrauterine inflammation. Though the maternal blood glucose concentration was temporally prevented from decrease induced by intrauterine inflammation, the glucose concentration in fetal brain was not recovered by maternal glucose supplementation. The adenosine triphosphate (ATP) level and autophagy in fetal brain were regulated by maternal glucose supplementation, which may prevent dysregulation of cellular metabolism. Our study is the first to provide evidence for the role of maternal glucose supplementation in the cell survival of fetal brain during intrauterine inflammation and further support the possible medication with maternal glucose treatment.

Mechanisms and context underlying the role of autophagy in cancer metastasis

Macroautophagy/autophagy is a fundamental cellular degradation mechanism that maintains cell homeostasis, regulates cell signaling, and promotes cell survival. Its role in promoting tumor cell survival in stress conditions is well characterized, and makes autophagy an attractive target for cancer therapy. Emerging research indicates that autophagy also influences cancer metastasis, which is the primary cause of cancer-associated mortality. However, data demonstrate that the regulatory role of autophagy in metastasis is multifaceted, and includes both metastasis-suppressing and -promoting functions. The metastasis-suppressing functions of autophagy, in particular, have important implications for autophagy-based treatments, as inhibition of autophagy may increase the risk of metastasis. In this review, we discuss the mechanisms and context underlying the role of autophagy in metastasis, which include autophagy-mediated regulation of focal adhesion dynamics, integrin signaling and trafficking, Rho GTPase-mediated cytoskeleton remodeling, anoikis resistance, extracellular matrix remodeling, epithelial-to-mesenchymal transition signaling, and tumor-stromal cell interactions. Through this, we aim to clarify the context-dependent nature of autophagy-mediated metastasis and provide direction for further research investigating the role of autophagy in cancer metastasis.

Using Drosophila Models of Amyloid Toxicity to Study Autophagy in the Pathogenesis of Alzheimer's Disease

Autophagy is a conserved catabolic pathway that involves the engulfment of cytoplasmic components such as large protein aggregates and organelles that are delivered to the lysosome for degradation. This process is important in maintaining neuronal function and raises the possibility of a role for autophagy in neurodegenerative diseases. Alzheimer's disease (AD) is the most prevalent form of these diseases and is characterized by the accumulation of amyloid plaques in the brain which arise due to the misfolding and aggregation of toxic peptides, including amyloid beta (Aβ). There is substantial evidence from both AD patients and animal models that autophagy is dysregulated in this disease. However, it remains to be determined whether this is protective or pathogenic as there is evidence that autophagy can act to promote the degradation as well as function in the generation of toxic Aβ peptides. Understanding the molecular details of the extensive crosstalk that occurs between the autophagic and endolysosomal cellular pathways is essential for identifying the molecular details of amyloid toxicity. Drosophila models that express the toxic proteins that aggregate in AD have been generated and have been shown to recapitulate hallmarks of the disease. Here we focus on what is known about the role of autophagy in amyloid toxicity in AD from mammalian models and how Drosophila models can be used to further investigate AD pathogenesis.

mTOR: An attractive therapeutic target for osteosarcoma?

Osteosarcoma (OS) is a common primary malignant bone tumor with high morbidity and mortality in children and young adults. How to improve poor prognosis of OS due to resistance to chemotherapy remains a challenge. Recently, growing findings show activation of mammalian target of rapamycin (mTOR), is associated with OS cell growth, proliferation, metastasis. Targeting mTOR may be a promising therapeutic approach for treating OS. This review summarizes the roles of mTOR pathway in OS and present research status of mTOR inhibitors in the context of OS. In addition, we have attempted to discuss how to design a better treatment project for OS by combining mTOR inhibitor with other drugs.

Autophagy induced during apoptosis degrades mitochondria and inhibits type I interferon secretion

Cells undergoing Bax/Bak-mediated apoptosis exhibit signs of autophagy, but how it is activated and its significance is unknown. By directly activating Bax/Bak with BH3-only proteins or BH3 mimetic compounds, we demonstrate that mitochondrial damage correlated with a rapid increase in intracellular [AMP]/[ATP], phosphorylation of 5' AMP-activated protein kinase (AMPK), and activation of unc-51 like autophagy activating kinase 1 (ULK1). Consequently, autophagic flux was triggered early in the apoptotic pathway, as activation of the apoptosome and caspases were not necessary for its induction. Bax/Bak-triggered autophagy resulted in the clearance of damaged mitochondria in an ATG5/7-dependent manner that did not require Parkin. Importantly, Bax/Bak-mediated autophagy inhibited the secretion of the pro-inflammatory cytokine interferon-β (IFN-β) produced in response to mitochondrial damage, but not another cytokine interleukin-6 (IL-6). These findings show that Bax/Bak stimulated autophagy is essential for ensuring immunological silence during apoptosis.

Cross-talk between protein synthesis, energy metabolism and autophagy in cancer

Translation is a pivotal step in the regulation of gene expression as well as one of the most energy consuming processes in the cell. Dysregulation of translation caused by the aberrant function of upstream signaling pathways and/or perturbations in the expression or function of components of the translation machinery is frequent in cancer. In this review, we discuss emerging findings that highlight hitherto unappreciated aspects of signaling to the translation apparatus with the particular focus on emerging connections between protein synthesis, autophagy and energy homeostasis in cancer.

Effects of ginkgol C17:1 on cisplatin-induced autophagy and apoptosis in HepG2 cells

Previous studies have demonstrated that ginkgol C17:1 significantly inhibits human liver cancer cells and enhances the anticancer activity of cisplatin in vivo and in vitro. However, the mechanism and biological function of ginkgol C17:1 on cells undergoing chemotherapy remain unclear. The aim of the present study was to determine the antitumor activity and mechanism of ginkgol C17:1 in combination with cisplatin in human hepatoblastoma HepG2 cells. The green fluorescent protein (GFP)-light chain 3 (LC3) adenovirus was transfected into HepG2 cells and autophagic flux was determined using fluorescence microscopy. Western blot analysis was also conducted to measure the expression of proteins associated with apoptosis, autophagy and their associated signaling pathways. Compared with the control group, autophagic flux and nucleus aberration rates were significantly increased (P<0.05), and the expression of proteins associated with autophagy and apoptosis were increased in the groups treated with cisplatin or ginkgol C17:1, respectively. However, following co-treatment with ginkgol C17:1 and cisplatin, the autophagic flux and the expression of autophagy proteins decreased; however, the nucleus aberration rate and apoptosis protein expression significantly increased (P<0.05) compared with the group treated with cisplatin alone. Additionally, the signaling pathways of autophagy and apoptosis were also activated following treatment with cisplatin, alone and in combination with ginkgol C17:1. Taken together, these results indicate that ginkgol C17:1 inhibits cisplatin-induced autophagy via AMP-activated protein kinase/ULK1signaling and increases cisplatin-induced apoptosis in HepG2 cells via the phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin pathway.

In Search of a Converging Cellular Mechanism in Nanotoxicology and Nanomedicine in the Treatment of Cancer

Multiple applications of nanomaterials have raised concern with regard to their toxicity. With increasing research into nanomaterial safety, mechanisms involved in the toxic effects of nanomaterials have begun to emerge. The importance of nanomaterial-induced lysosomal membrane permeabilization through overloading or direct damage of the lysosomal compartment, resulting in the blockade of autophagosome-lysosome fusion and autophagy dysfunction, as well as inflammasome activation were cited as emerging mechanisms of nanomaterial toxicity. It has recently been proposed that these very mechanisms leading to nanomaterial toxicity may be utilized in nanotherapeutics. This review discusses these nanomaterial-induced mechanisms in detail and how it has been exploited in cancer research. This review also addresses certain considerations that need to be kept in mind when using nanomaterials in therapeutics.

5-Aminoimidazole-4-carboxamide ribonucleoside-induced autophagy flux during differentiation of monocytic leukemia cells

Pharmacological modulators of AMP-dependent kinase (AMPK) have been suggested in treatment of cancer. The biguanide metformin and 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) have been reported to inhibit proliferation of solid tumors and hematological malignancies, but their role in differentiation is less explored. Our previous study demonstrated that AICAR alone induced AMPK-independent expression of differentiation markers in monocytic U937 leukemia cells, and no such effects were observed in response to metformin. The aim of this study was to determine the mechanism of AICAR-mediated effects and to test for the possible role of autophagy in differentiation of leukemia cells. The results showed that AICAR-mediated effects on the expression of differentiation markers were not mimicked by A769662, a more specific direct AMPK activator. Long-term incubation of U937 cells with AICAR and other differentiation agents, all-trans-retinoic acid (ATRA) and phorbol 12-myristate 13-acetate, increased the expression of the autophagy marker LC3B-II, and these effects were not observed in response to metformin. Western blot and immunofluorescence analyses of U937 cells treated with bafilomycin A1 or transfected with mRFP-GFP-LC3 proved that the increase in the expression of LC3B-II was due to an increase in autophagy flux, and not to a decrease in lysosomal degradation. 3-Methyladenine inhibited the expression of differentiation markers in response to all inducers, but had stimulatory effects on autophagy flux at dose that effectively inhibited the production of phosphatidylinositol 3-phosphate. The small inhibitory RNA-mediated down-modulation of Beclin 1 and hVPS34 had no effects on AICAR and ATRA-mediated increase in the expression of differentiation markers. These results show that AICAR and other differentiation agents induce autophagy flux in U937 cells and that the effects of AICAR and ATRA on the expression of differentiation markers do not depend on the normal levels of key proteins of the classical or canonical autophagy pathway.

Integrative metabolomics as emerging tool to study autophagy regulation

Recent technological developments in metabolomics research have enabled in-depth characterization of complex metabolite mixtures in a wide range of biological, biomedical, environmental, agricultural, and nutritional research fields. Nuclear magnetic resonance spectroscopy and mass spectrometry are the two main platforms for performing metabolomics studies. Given their broad applicability and the systemic insight into metabolism that can be obtained it is not surprising that metabolomics becomes increasingly popular in basic biological research. In this review, we provide an overview on key metabolites, recent studies, and future opportunities for metabolomics in studying autophagy regulation. Metabolites play a pivotal role in autophagy regulation and are therefore key targets for autophagy research. Given the recent success of metabolomics, it can be expected that metabolomics approaches will contribute significantly to deciphering the complex regulatory mechanisms involved in autophagy in the near future and promote understanding of autophagy and autophagy-related diseases in living cells and organisms.

Molecular definitions of autophagy and related processes

Over the past two decades, the molecular machinery that underlies autophagic responses has been characterized with ever increasing precision in multiple model organisms. Moreover, it has become clear that autophagy and autophagy-related processes have profound implications for human pathophysiology. However, considerable confusion persists about the use of appropriate terms to indicate specific types of autophagy and some components of the autophagy machinery, which may have detrimental effects on the expansion of the field. Driven by the overt recognition of such a potential obstacle, a panel of leading experts in the field attempts here to define several autophagy-related terms based on specific biochemical features. The ultimate objective of this collaborative exchange is to formulate recommendations that facilitate the dissemination of knowledge within and outside the field of autophagy research.

PKM2-mediated inhibition of autophagy facilitates Tat's inducing HIV-1 transactivation

Considerable evidence has shown that autophagy has an important role in HIV-1 infection. However, it is still unknown whether metabolism-regulated autophagy pathway is involved in Tat-mediated HIV-1 transactivation. This study demonstrated that treatment of Tat in TZM-bl cells significantly down-regulated protein levels of Beclin-1, Atg-5, Atg-7, and LC3B-II and up-regulated of p62 levels. Blockage of autophagy enhanced Tat-induced HIV-1 transactivation in TZM-bl cells. Moreover, we found that Tat activated the Akt/mTOR and inhibited AMPK signaling pathway that was related to its up-regulation of PKM2 expression. In addition, we showed that PI3K/AKT activation and AMPK inhibtion was required for the PKM2-mediated inhibition of autophagy in Tat-treated TZM-bl cells. In conclusion, our data reveals that PKM2-mediated autophagy inhibition is required for Tat-mediated HIV-1 transactivation. Metabolism-related autophagic pathway may act as a promising diagnostic and therapeutic tool for HIV-1 infection in the future.

Autophagy enhanced the radioresistance of non-small cell lung cancer by regulating ROS level under hypoxia condition

PURPOSE

Tumor resistance towards radiation has been a big obstacle in the poor prognosis of lung cancer. It has been reported that hypoxia and autophagy partly contribute to this resistance. However, there is controversy over whether autophagy plays a positive role in cancer therapy or not. We aim to find out the specific mechanism of radiation resistance.

MATERIALS AND METHODS

A549 cells were treated with conditioned medium (CM) under 12 h hypoxia or normoxia before irradiation, followed by the measurement of clonogenic survival, reactive oxygen species (ROS), signal of mitochondria and autophagy flux. In some experiments, the A549 cells were respectively transfected with LC3 small interfering RNA (siRNA), or treated with Earle's Balanced Salt Solution (EBSS).

RESULTS

We found that hypoxia enhanced cell radioresistance by increasing the induction of autophagy. And after hypoxia stress, the number of mitochondria was reduced but the cellular ROS level was enhanced. It was significant that autophagy may enhance cell radioresistance by reducing ROS during hypoxic treatment.

CONCLUSIONS

We elucidated the possible mechanisms of autophagy in regulating cancer cell death or survival. These results supply a new opinion about the intrinsic factor of radioresistance of hypoxia tumors.

Identification of novel small molecule Beclin 1 mimetics activating autophagy

Anti-apoptotic proteins Bcl-2 and Bcl-xL could block autophagy by binding to Beclin 1 protein, an essential inducer of autophagy. Compounds mimicking Beclin 1 might be able to disrupt Bcl-xL/2-Beclin 1 interaction, free out Beclin 1, and thus trigger autophagy. In order to identify small molecule Beclin 1 mimetics, a fluorescence polarization-based high-throughput screening of 50,316 compounds was carried out with a Z' score of 0.82 ± 0.05, and an outcome of 58 hits. After the structure analysis, three acridine analogues were unveiled and confirmed using the fluorescence polarization assay and the surface plasmon resonance assay. Moreover, a set of 17 additional acridine analogues was prepared and tested. Compound 7 showed selectivity for Bcl-xL (K_D = 6.5 μM) over Bcl-2 (K_D = 160 μM) protein, and potent cytotoxicity (nanomolar scale) in PC-3, PC-3a and DU145 prostate cancer cells. Furthermore, induction of autophagy was also demonstrated in PC-3 and PC-3a cells treated with some acridine compounds by LC3 conversion immunoblotting and LC3 fluorescence microscopy. These Beclin 1 mimetics will be invaluable tools for developing novel autophagy inducers, better understanding the roles of autophagy in cancer, and will contribute to cancer therapy.

'Did He Who Made the Lamb Make Thee?' New Developments in Treating the 'Fearful Symmetry' of Acute Myeloid Leukemia

Malignant cells must circumvent endogenous cell death pathways to survive and develop into cancers. Acquired cell death resistance also sets up malignant cells to survive anticancer therapies. Acute Myeloid Leukemia (AML) is an aggressive blood cancer characterized by high relapse rate and resistance to cytotoxic therapies. Recent collaborative profiling projects have led to a greater understanding of the 'fearful symmetry' of the genomic landscape of AML, and point to the development of novel potential therapies that can overcome factors linked to chemoresistance. We review here the most recent research in the genetics of AML and how these discoveries have led, or might lead, to therapies that specifically activate cell death pathways to substantially challenge this 'fearful' disease.

Autophagy-from molecular mechanisms to clinical relevance

Autophagy is a lysosomal degradation pathway of eukaryotic cells that is highly conserved from yeast to mammals. During this process, cooperating protein complexes are recruited in a hierarchic order to the phagophore assembly site (PAS) to mediate the elongation and closure of double-membrane vesicles called autophagosomes, which sequester cytosolic components and deliver their content to the endolysosomal system for degradation. As a major cytoprotective mechanism, autophagy plays a key role in the stress response against nutrient starvation, hypoxia, and infections. Although numerous studies reported that impaired function of core autophagy proteins also contributes to the development and progression of various human diseases such as neurodegenerative disorders, cardiovascular and muscle diseases, infections, and different types of cancer, the function of this process in human diseases remains unclear. Evidence often suggests a controversial role for autophagy in the pathomechanisms of these severe disorders. Here, we provide an overview of the molecular mechanisms of autophagy and summarize the recent advances on its function in human health and disease.

Mechanistic roles of autophagy in hematopoietic differentiation

Autophagy is increasingly recognized for its active role in development and differentiation. In particular, its role in the differentiation of hematopoietic cells has been extensively studied, likely because blood cells are accessible, easy to identify and purify, and their progenitor tree is well defined. This review aims to discuss the mechanisms by which autophagy impacts on differentiation, using hematopoietic cell types as examples. Autophagy's roles include the remodeling during terminal differentiation, the maintenance of a long-lived cell type, and the regulation of the balance between self-renewal and quiescence in stem-like cells. We discuss and compare the mechanistic roles of autophagy, such as prevention of apoptosis, supply of energy metabolites and metabolic adaption, and selective degradation of organelles and of regulatory factors.

Simulated ischemia/reperfusion-induced p65-Beclin 1-dependent autophagic cell death in human umbilical vein endothelial cells

Myocardial ischemia/reperfusion (I/R) injury detrimentally alters the prognosis of patients undergoing revascularization after acute myocardial infarction. Our previous study demonstrated that NF-κB-induced autophagy plays a detrimental role in cardiac I/R injury using a rabbit myocardial I/R model. In this study, we sought to explore the specific mechanism of this autophagy-mediated cell damage in an in vitro simulated ischemia/reperfusion (sI/R) model using human umbilical vein endothelial cells. Our current study demonstrates that simulated I/R induces autophagy in a p65-Beclin 1-dependent manner, which can be suppressed with the inhibition of NF-κB. Furthermore, rapamycin which promotes autophagy, exacerbates sI/R-induced cell death. While 3-methyladenine rescues cell damage. Our data thus suggest that I/R promotes NF-κB p65 activity mediated Beclin 1-mediated autophagic flux, thereby exacerbating myocardial injury.

Regulation of actin nucleation and autophagosome formation

Autophagy is a process of self-eating, whereby cytosolic constituents are enclosed by a double-membrane vesicle before delivery to the lysosome for degradation. This is an important process which allows for recycling of nutrients and cellular components and thus plays a critical role in normal cellular homeostasis as well as cell survival during stresses such as starvation or hypoxia. A large number of proteins regulate various stages of autophagy in a complex and still incompletely understood series of events. In this review, we will discuss recent studies which provide a growing body of evidence that actin dynamics and proteins that influence actin nucleation play an important role in the regulation of autophagosome formation and maturation.

[Valproic acid activates autophagy in multiple myeloma cell lines RPMI8226 and U266]

目的

探讨丙戊酸钠对多发性骨髓瘤（MM）细胞株RPMI8226和U266细胞自噬的影响。

方法

丙戊酸钠处理RPMI8226和U266细胞，吖啶橙染色后采用荧光显微镜观察细胞自噬形态学变化，MTT法检测细胞增殖抑制的变化，流式细胞术检测细胞凋亡，实时定量PCR（RT-PCR）和Western Blot法检测细胞自噬相关因子LC3、Beclin1的变化。

结果

荧光显微镜观察到RPMI8226及U266细胞存在基础水平的自噬现象，丙戊酸钠作用后能够诱导细胞自噬增多；MTT法检测结果显示丙戊酸钠对细胞增殖抑制具有时间及浓度依赖性，作用24 h后半数抑制浓度分别为（12.03±0.23）mmol/L和（10.16±0.37) mmol/L。8 mmol/L丙戊酸钠作用24 h后，RPMI8226、U266细胞LC3 mRNA表达水平（22.45±0.07、0.06±0.02）、Beclin1 mRNA表达水平（283.09±17.3、1.53±0.01）与空白对照组（1.00± 0.00、1.00±0.00）比较，差异均有统计学意义（P值均<0.05）。随着丙戊酸钠浓度增加和作用时间延长，LC3、Beclin1蛋白表达水平逐渐增加，LC3Ⅰ向LC3Ⅱ的转化率逐渐升高。

结论

RPMI8226和U266细胞中存在基础水平的自噬现象，丙戊酸钠对MM细胞的自噬有激活作用，这可能是丙戊酸钠治疗MM的机制之一。

BAX-BAK1-independent LC3B lipidation by BH3 mimetics is unrelated to BH3 mimetic activity and has only minimal effects on autophagic flux

Inhibition of prosurvival BCL2 family members can induce autophagy, but the mechanism is controversial. We have provided genetic evidence that BCL2 family members block autophagy by inhibiting BAX and BAK1, but others have proposed they instead inhibit BECN1. Here we confirm that small molecule BH3 mimetics can induce BAX- and BAK1-independent MAP1LC3B/LC3B lipidation, but this only occurred at concentrations far greater than required to induce apoptosis and dissociate canonical BH3 domain-containing proteins that bind more tightly than BECN1. Because high concentrations of a less-active enantiomer of ABT-263 also induced BAX- and BAK1-independent LC3B lipidation, induction of this marker of autophagy appears to be an off-target effect. Indeed, robust autophagic flux was not induced by BH3 mimetic compounds in the absence of BAX and BAK1. Therefore at concentrations that are on target and achievable in vivo, BH3 mimetics only induce autophagy in a BAX- and BAK1-dependent manner.

Autophagy and Mammalian Viruses: Roles in Immune Response, Viral Replication, and Beyond

Autophagy is an important cellular catabolic process conserved from yeast to man. Double-membrane vesicles deliver their cargo to the lysosome for degradation. Hence, autophagy is one of the key mechanisms mammalian cells deploy to rid themselves of intracellular pathogens including viruses. However, autophagy serves many more functions during viral infection. First, it regulates the immune response through selective degradation of immune components, thus preventing possibly harmful overactivation and inflammation. Additionally, it delivers virus-derived antigens to antigen-loading compartments for presentation to T lymphocytes. Second, it might take an active part in the viral life cycle by, eg, facilitating its release from cells. Lastly, in the constant arms race between host and virus, autophagy is often hijacked by viruses and manipulated to their own advantage. In this review, we will highlight key steps during viral infection in which autophagy plays a role. We have selected some exemplary viruses and will describe the molecular mechanisms behind their intricate relationship with the autophagic machinery, a result of host-pathogen coevolution.

Withaferin-A--A Natural Anticancer Agent with Pleitropic Mechanisms of Action

Cancer, being the second leading cause of mortality, exists as a formidable health challenge. In spite of our enormous efforts, the emerging complexities in the molecular nature of disease progression limit the real success in finding an effective cancer cure. It is now conceivable that cancer is, in fact, a progressive illness, and the morbidity and mortality from cancer can be reduced by interfering with various oncogenic signaling pathways. A wide variety of structurally diverse classes of bioactive phytochemicals have been shown to exert anticancer effects in a large number of preclinical studies. Multiple lines of evidence suggest that withaferin-A can prevent the development of cancers of various histotypes. Accumulating data from different rodent models and cell culture experiments have revealed that withaferin-A suppresses experimentally induced carcinogenesis, largely by virtue of its potent anti-oxidative, anti-inflammatory, anti-proliferative and apoptosis-inducing properties. Moreover, withaferin-A sensitizes resistant cancer cells to existing chemotherapeutic agents. The purpose of this review is to highlight the mechanistic aspects underlying anticancer effects of withaferin-A.