Peroxisome turnover by micropexophagy: an autophagy-related process

Autophagy in Crohn's Disease: Converging on Dysfunctional Innate Immunity

Crohn's disease (CD) is a chronic inflammatory bowel disease marked by relapsing, transmural intestinal inflammation driven by innate and adaptive immune responses. Autophagy is a multi-step process that plays a critical role in maintaining cellular homeostasis by degrading intracellular components, such as damaged organelles and invading bacteria. Dysregulation of autophagy in CD is revealed by the identification of several susceptibility genes, including ATG16L1, IRGM, NOD2, LRRK2, ULK1, ATG4, and TCF4, that are involved in autophagy. In this review, the role of altered autophagy in the mucosal innate immune response in the context of CD is discussed, with a specific focus on dendritic cells, macrophages, Paneth cells, and goblet cells. Selective autophagy, such as xenophagy, ERphagy, and mitophagy, that play crucial roles in maintaining intestinal homeostasis in these innate immune cells, are discussed. As our understanding of autophagy in CD pathogenesis evolves, the development of autophagy-targeted therapeutics may benefit subsets of patients harboring impaired autophagy.

The emerging mechanisms and functions of microautophagy

'Autophagy' refers to an evolutionarily conserved process through which cellular contents, such as damaged organelles and protein aggregates, are delivered to lysosomes for degradation. Different forms of autophagy have been described on the basis of the nature of the cargoes and the means used to deliver them to lysosomes. At present, the prevailing categories of autophagy in mammalian cells are macroautophagy, microautophagy and chaperone-mediated autophagy. The molecular mechanisms and biological functions of macroautophagy and chaperone-mediated autophagy have been extensively studied, but microautophagy has received much less attention. In recent years, there has been a growth in research on microautophagy, first in yeast and then in mammalian cells. Here we review this form of autophagy, focusing on selective forms of microautophagy. We also discuss the upstream regulatory mechanisms, the crosstalk between macroautophagy and microautophagy, and the functional implications of microautophagy in diseases such as cancer and neurodegenerative disorders in humans. Future research into microautophagy will provide opportunities to develop novel interventional strategies for autophagy- and lysosome-related diseases.

Translating the Arabidopsis thaliana Peroxisome Proteome Insights to Solanum lycopersicum: Consensus Versus Diversity

Peroxisomes are small, single-membrane specialized organelles present in all eukaryotic organisms. The peroxisome is one of the nodal centers of reactive oxygen species homeostasis in plants, which are generated in a high amount due to various stress conditions. Over the past decade, there has been extensive study on peroxisomal proteins and their signaling pathways in the model plant Arabidopsis thaliana, and a lot has been deciphered. However, not much impetus has been given to studying the peroxisome proteome of economically important crops. Owing to the significance of peroxisomes in the physiology of plants during normal and stress conditions, understating its proteome is of much importance. Hence, in this paper, we have made a snapshot of putative peroxisomal matrix proteins in the economically important vegetable crop tomato (Solanum lycopersicum, (L.) family Solanaceae). First, a reference peroxisomal matrix proteome map was generated for Arabidopsis thaliana using the available proteomic and localization studies, and proteins were categorized into various groups as per their annotations. This was used to create the putative peroxisomal matrix proteome map for S. lycopersicum. The putative peroxisome proteome in S. lycopersicum retains the basic framework: the bulk of proteins had peroxisomal targeting signal (PTS) type 1, a minor group had PTS2, and the catalase family retained its characteristic internal PTS. Apart from these, a considerable number of S. lycopersicum orthologs did not contain any “obvious” PTS. The number of PTS2 isoforms was found to be reduced in S. lycopersicum. We further investigated the PTS1s in the case of both the plant species and generated a pattern for canonical and non-canonical PTS1s. The number of canonical PTS1 proteins was comparatively lesser in S. lycopersicum. The non-canonical PTS1s were found to be comparable in both the plant species; however, S. lycopersicum showed greater diversity in the composition of the signal tripeptide. Finally, we have tried to address the lacunas and probable strategies to fill those gaps.

Over Fifty Years of Life, Death, and Cannibalism: A Historical Recollection of Apoptosis and Autophagy

Research in biomedical sciences has changed dramatically over the past fifty years. There is no doubt that the discovery of apoptosis and autophagy as two highly synchronized and regulated mechanisms in cellular homeostasis are among the most important discoveries in these decades. Along with the advancement in molecular biology, identifying the genetic players in apoptosis and autophagy has shed light on our understanding of their function in physiological and pathological conditions. In this review, we first describe the history of key discoveries in apoptosis with a molecular insight and continue with apoptosis pathways and their regulation. We touch upon the role of apoptosis in human health and its malfunction in several diseases. We discuss the path to the morphological and molecular discovery of autophagy. Moreover, we dive deep into the precise regulation of autophagy and recent findings from basic research to clinical applications of autophagy modulation in human health and illnesses and the available therapies for many diseases caused by impaired autophagy. We conclude with the exciting crosstalk between apoptosis and autophagy, from the early discoveries to recent findings.

Lactate and Pyruvate Activate Autophagy and Mitophagy that Protect Cells in Toxic Model of Parkinson's Disease

Intracellular quality control regulated by autophagy process is important for maintenance of cellular homeostasis. Deregulation of autophagy and more specifically mitophagy leads to accumulation of the misfolded proteins and damaged mitochondria that in turn leads to the cell loss. Alteration of autophagy and mitophagy has shown to be involved in the number of disorders including neurodegenerative diseases. Autophagy and mitophagy could be activated by short-time acidification of the cytosol; however, most of the compounds which can induce it are toxic. Here, we tested several organic compounds which are involved in cellular metabolism on their ability to change intracellular pH and induce mitophagy/autophagy. We have found that lactate and pyruvate are able to reduce intracellular pH in non-toxic concentrations. Short-term (2 h) and long-term (24 h) incubation of the cells with lactate and pyruvateinduced mitophagy and autophagy. Incubation of the SH-SY5Y cells or primary neurons and astrocytes with lactate or pyruvate also activated mitophagy and autophagy after MPP + treatment that led to recovery of mitochondrial function and protection of these cells against apoptotic and necrotic death. Thus, pyruvate- or lactate-induced acidification of cytosol activates cell protective mitophagy and autophagy.

Autophagy in farm animals: current knowledge and future challenges

Autophagy (a process of cellular self-eating) is a conserved cellular degradative process that plays important roles in maintaining homeostasis and preventing nutritional, metabolic, and infection-mediated stresses. Surprisingly, little attention has been paid to the role of this cellular function in species of agronomical interest, and the details of how autophagy functions in the development of phenotypes of agricultural interest remain largely unexplored. Here, we first provide a brief description of the main mechanisms involved in autophagy, then review our current knowledge regarding autophagy in species of agronomical interest, with particular attention to physiological functions supporting livestock animal production, and finally assess the potential of translating the acquired knowledge to improve animal development, growth and health in the context of growing social, economic and environmental challenges for agriculture.Abbreviations: AKT: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ASC: adipose-derived stem cells; ATG: autophagy-related; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; BVDV: bovine viral diarrhea virus; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CMA: chaperone-mediated autophagy; CTSB: cathepsin B; CTSD: cathepsin D; DAP: Death-Associated Protein; ER: endoplasmic reticulum; GFP: green fluorescent protein; Gln: Glutamine; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; IF: immunofluorescence; IVP: in vitro produced; LAMP2A: lysosomal associated membrane protein 2A; LMS: lysosomal membrane stability; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MDBK: Madin-Darby bovine kidney; MSC: mesenchymal stem cells; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NBR1: NBR1 autophagy cargo receptor; NDV: Newcastle disease virus; NECTIN4: nectin cell adhesion molecule 4; NOD1: nucleotide-binding oligomerization domain 1; OCD: osteochondritis dissecans; OEC: oviduct epithelial cells; OPTN: optineurin; PI3K: phosphoinositide-3-kinase; PPRV: peste des petits ruminants virus; RHDV: rabbit hemorrhagic disease virus; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy.

Lipid Droplets and Their Autophagic Turnover via the Raft-Like Vacuolar Microdomains

Although once perceived as inert structures that merely serve for lipid storage, lipid droplets (LDs) have proven to be the dynamic organelles that hold many cellular functions. The LDs' basic structure of a hydrophobic core consisting of neutral lipids and enclosed in a phospholipid monolayer allows for quick lipid accessibility for intracellular energy and membrane production. Whereas formed at the peripheral and perinuclear endoplasmic reticulum, LDs are degraded either in the cytosol by lipolysis or in the vacuoles/lysosomes by autophagy. Autophagy is a regulated breakdown of dysfunctional, damaged, or surplus cellular components. The selective autophagy of LDs is called lipophagy. Here, we review LDs and their degradation by lipophagy in yeast, which proceeds via the micrometer-scale raft-like lipid domains in the vacuolar membrane. These vacuolar microdomains form during nutrient deprivation and facilitate internalization of LDs via the vacuolar membrane invagination and scission. The resultant intra-vacuolar autophagic bodies with LDs inside are broken down by vacuolar lipases and proteases. This type of lipophagy is called microlipophagy as it resembles microautophagy, the type of autophagy when substrates are sequestered right at the surface of a lytic compartment. Yeast microlipophagy via the raft-like vacuolar microdomains is a great model system to study the role of lipid domains in microautophagic pathways.

Knockdown of PEX16 Induces Autophagic Degradation of Peroxisomes

Peroxisome abundance is regulated by homeostasis between the peroxisomal biogenesis and degradation processes. Peroxin 16 (PEX16) is a peroxisomal protein involved in trafficking membrane proteins for de novo peroxisome biogenesis. The present study demonstrates that PEX16 also modulates peroxisome abundance through pexophagic degradation. PEX16 knockdown in human retinal pigment epithelial-1 cells decreased peroxisome abundance and function, represented by reductions in the expression of peroxisome membrane protein ABCD3 and the levels of cholesterol and plasmalogens, respectively. The activation of pexophagy under PEX16 knockdown was shown by (i) abrogated peroxisome loss under PEX16 knockdown in autophagy-deficient ATG5 knockout cell lines, and (ii) increased autophagy flux and co-localization of p62-an autophagy adaptor protein-with ABCD3 in the presence of the autophagy inhibitor chloroquine. However, the levels of cholesterol and plasmalogens did not recover despite the restoration of peroxisome abundance following chloroquine treatment. Thus, PEX16 is indispensable for maintaining peroxisome homeostasis by regulating not only the commonly known biogenesis pathway but also the autophagic degradation of peroxisomes.

Plasmodium falciparum Atg18 localizes to the food vacuole via interaction with the multi-drug resistance protein 1 and phosphatidylinositol 3-phosphate

Autophagy, a lysosome-dependent degradative process, does not appear to be a major degradative process in malaria parasites and has a limited repertoire of genes. To better understand the autophagy process, we investigated Plasmodium falciparum Atg18 (PfAtg18), a PROPPIN family protein, whose members like S. cerevisiae Atg18 (ScAtg18) and human WIPI2 bind PI3P and play an essential role in autophagosome formation. Wild type and mutant PfAtg18 were expressed in P. falciparum and assessed for localization, the effect of various inhibitors and antimalarials on PfAtg18 localization, and identification of PfAtg18-interacting proteins. PfAtg18 is expressed in asexual erythrocytic stages and localized to the food vacuole, which was also observed with other Plasmodium Atg18 proteins, indicating that food vacuole localization is likely a shared feature. Interaction of PfAtg18 with the food vacuole-associated PI3P is essential for localization, as PfAtg18 mutants of PI3P-binding motifs neither bound PI3P nor localized to the food vacuole. Interestingly, wild type ScAtg18 interacted with PI3P, but its expression in P. falciparum showed complete cytoplasmic localization, indicating additional requirement for food vacuole localization. The food vacuole multi-drug resistance protein 1 (MDR1) was consistently identified in the immunoprecipitates of PfAtg18 and P. berghei Atg18, and also interacted with PfAtg18. In contrast with PfAtg18, ScAtg18 did not interact with MDR1, which, in addition to PI3P, could play a critical role in localization of PfAtg18. Chloroquine and amodiaquine caused cytoplasmic localization of PfAtg18, suggesting that these target PfAtg18 transport pathway. Thus, PI3P and MDR1 are critical mediators of PfAtg18 localization.

Chaperone-Mediated Autophagy in the Light of Evolution: Insight from Fish

Chaperone-mediated autophagy (CMA) is a major pathway of lysosomal proteolysis recognized as a key player of the control of numerous cellular functions, and whose defects have been associated with several human pathologies. To date, this cellular function is presumed to be restricted to mammals and birds, due to the absence of an identifiable lysosome-associated membrane protein 2A (LAMP2A), a limiting and essential protein for CMA, in nontetrapod species. However, the recent identification of expressed sequences displaying high homology with mammalian LAMP2A in several fish species challenges that view and suggests that CMA likely appeared earlier during evolution than initially thought. In the present study, we provide a comprehensive picture of the evolutionary history of the LAMP2 gene in vertebrates and demonstrate that LAMP2 indeed appeared at the root of the vertebrate lineage. Using a fibroblast cell line from medaka fish (Oryzias latipes), we further show that the splice variant lamp2a controls, upon long-term starvation, the lysosomal accumulation of a fluorescent reporter commonly used to track CMA in mammalian cells. Finally, to address the physiological role of Lamp2a in fish, we generated knockout medaka for that specific splice variant, and found that these deficient fish exhibit severe alterations in carbohydrate and fat metabolisms, in consistency with existing data in mice deficient for CMA in liver. Altogether, our data provide the first evidence for a CMA-like pathway in fish and bring new perspectives on the use of complementary genetic models, such as zebrafish or medaka, for studying CMA in an evolutionary perspective.

Autophagy facilitates type I collagen synthesis in periodontal ligament cells

Autophagy is a lysosomal protein degradation system in which the cell self-digests its intracellular protein components and organelles. Defects in autophagy contribute to the pathogenesis of age-related chronic diseases, such as myocardial infarction and rheumatoid arthritis, through defects in the extracellular matrix (ECM). However, little is known about autophagy in periodontal diseases characterised by the breakdown of periodontal tissue. Tooth-supportive periodontal ligament (PDL) tissue contains PDL cells that produce various ECM proteins such as collagen to maintain homeostasis in periodontal tissue. In this study, we aimed to clarify the physiological role of autophagy in periodontal tissue. We found that autophagy regulated type I collagen synthesis by elimination of misfolded proteins in human PDL (HPDL) cells. Inhibition of autophagy by E-64d and pepstatin A (PSA) or siATG5 treatment suppressed collagen production in HPDL cells at mRNA and protein levels. Immunoelectron microscopy revealed collagen fragments in autolysosomes. Accumulation of misfolded collagen in HPDL cells was confirmed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. E-64d and PSA treatment suppressed and rapamycin treatment accelerated the hard tissue-forming ability of HPDL cells. Our findings suggest that autophagy is a crucial regulatory process that facilitates type I collagen synthesis and partly regulates osteoblastic differentiation of PDL cells.

Autophagy and LRRK2 in the Aging Brain

Autophagy is a highly conserved process by which long-lived macromolecules, protein aggregates and dysfunctional/damaged organelles are delivered to lysosomes for degradation. Autophagy plays a crucial role in regulating protein quality control and cell homeostasis in response to energetic needs and environmental challenges. Indeed, activation of autophagy increases the life-span of living organisms, and impairment of autophagy is associated with several human disorders, among which neurodegenerative disorders of aging, such as Parkinson’s disease. These disorders are characterized by the accumulation of aggregates of aberrant or misfolded proteins that are toxic for neurons. Since aging is associated with impaired autophagy, autophagy inducers have been viewed as a strategy to counteract the age-related physiological decline in brain functions and emergence of neurodegenerative disorders. Parkinson’s disease is a hypokinetic, multisystemic disorder characterized by age-related, progressive degeneration of central and peripheral neuronal populations, associated with intraneuronal accumulation of proteinaceous aggregates mainly composed by the presynaptic protein α-synuclein. α-synuclein is a substrate of macroautophagy and chaperone-mediated autophagy (two major forms of autophagy), thus impairment of its clearance might favor the process of α-synuclein seeding and spreading that trigger and sustain the progression of this disorder. Genetic factors causing Parkinson’s disease have been identified, among which mutations in the LRRK2 gene, which encodes for a multidomain protein encompassing central GTPase and kinase domains, surrounded by protein-protein interaction domains. Six LRRK2 mutations have been pathogenically linked to Parkinson’s disease, the most frequent being the G2019S in the kinase domain. LRRK2-associated Parkinson’s disease is clinically and neuropathologically similar to idiopathic Parkinson’s disease, also showing age-dependency and incomplete penetrance. Several mechanisms have been proposed through which LRRK2 mutations can lead to Parkinson’s disease. The present article will focus on the evidence that LRRK2 and its mutants are associated with autophagy dysregulation. Studies in cell lines and neurons in vitro and in LRRK2 knock-out, knock-in, kinase-dead and transgenic animals in vivo will be reviewed. The role of aging in LRRK2-induced synucleinopathy will be discussed. Possible mechanisms underlying the LRRK2-mediated control over autophagy will be analyzed, and the contribution of autophagy dysregulation to the neurotoxic actions of LRRK2 will be examined.

Sucrose Starvation Induces Microautophagy in Plant Root Cells

Autophagy is an essential system for degrading and recycling cellular components for survival during starvation conditions. Under sucrose starvation, application of a papain protease inhibitor E-64d to the Arabidopsis root and tobacco BY-2 cells induced the accumulation of vesicles, labeled with a fluorescent membrane marker FM4-64. The E-64d-induced vesicle accumulation was reduced in the mutant defective in autophagy-related genes ATG2, ATG5, and ATG7, suggesting autophagy is involved in the formation of these vesicles. To clarify the formation of these vesicles in detail, we monitored time-dependent changes of tonoplast, and vesicle accumulation in sucrose-starved cells. We found that these vesicles were derived from the tonoplast and produced by microautophagic process. The tonoplast proteins were excluded from the vesicles, suggesting that the vesicles are generated from specific membrane domains. Concanamycin A treatment in GFP-ATG8a transgenic plants showed that not all FM4-64-labeled vesicles, which were derived from the tonoplast, contained the ATG8a-containing structure. These results suggest that ATG8a may not always be necessary for microautophagy.

Autophagic Machinery of Plant Peroxisomes

Peroxisomes are cell organelles that play an important role in plants in many physiological and developmental processes. The plant peroxisomes harbor enzymes of the β-oxidation of fatty acids and the glyoxylate cycle; photorespiration; detoxification of reactive oxygen and nitrogen species; as well as biosynthesis of hormones and signal molecules. The function of peroxisomes in plant cells changes during plant growth and development. They are transformed from organelles involved in storage lipid breakdown during seed germination and seedling growth into leaf peroxisomes involved in photorespiration in green parts of the plant. Additionally, intensive oxidative metabolism of peroxisomes causes damage to their components. Therefore, unnecessary or damaged peroxisomes are degraded by selective autophagy, called pexophagy. This is an important element of the quality control system of peroxisomes in plant cells. Despite the fact that the mechanism of pexophagy has already been described for yeasts and mammals, the molecular mechanisms by which plant cells recognize peroxisomes that will be degraded via pexophagy still remain unclear. It seems that a plant-specific mechanism exists for the selective degradation of peroxisomes. In this review, we describe the physiological role of pexophagy in plant cells and the current hypotheses concerning the mechanism of plant pexophagy.

Correlation of Autophagosome Formation with Degradation and Endocytosis Arabidopsis Regulator of G-Protein Signaling (RGS1) through ATG8a

Damaged or unwanted cellular proteins are degraded by either autophagy or the ubiquitin/proteasome pathway. In Arabidopsis thaliana, sensing of D-glucose is achieved by the heterotrimeric G protein complex and regulator of G-protein signaling 1 (AtRGS1). Here, we showed that starvation increases proteasome-independent AtRGS1 degradation, and it is correlated with increased autophagic flux. RGS1 promoted the production of autophagosomes and autophagic flux; RGS1-yellow fluorescent protein (YFP) was surrounded by vacuolar dye FM4-64 (red fluorescence). RGS1 and autophagosomes co-localized in the root cells of Arabidopsis and BY-2 cells. We demonstrated that the autophagosome marker ATG8a interacts with AtRGS1 and its shorter form with truncation of the seven transmembrane and RGS1 domains in planta. Altogether, our data indicated the correlation of autophagosome formation with degradation and endocytosis of AtRGS1 through ATG8a.

Emerging lysosomal pathways for quality control at the endoplasmic reticulum

Protein misfolding occurring in the endoplasmic reticulum (ER) might eventually lead to aggregation and cellular distress, and is a primary pathogenic mechanism in multiple human disorders. Mammals have developed evolutionary-conserved quality control mechanisms at the level of the ER. The best characterized is the ER-associated degradation (ERAD) pathway, through which misfolded proteins translocate from the ER to the cytosol and are subsequently proteasomally degraded. However, increasing evidence indicates that additional quality control mechanisms apply for misfolded ER clients that are not eligible for ERAD. This review focuses on the alternative, ERAD-independent, mechanisms of clearance of misfolded polypeptides from the ER. These processes, collectively referred to as ER-to-lysosome-associated degradation, involve ER-phagy, microautophagy or vesicular transport. The identification of the underlying molecular mechanisms is particularly important for developing new therapeutic approaches for human diseases associated with protein aggregate formation.

ER-phagy: shaping up and destressing the endoplasmic reticulum

The endoplasmic reticulum (ER) network has central roles in metabolism and cellular organization. The ER undergoes dynamic alterations in morphology, molecular composition and functional specification. Remodelling of the network under fluctuating conditions enables the continual performance of ER functions and minimizes stress. Recent data have revealed that selective autophagy‐mediated degradation of ER fragments, or ER‐phagy, fundamentally contributes to this remodelling. This review provides a perspective on established views of selective autophagy, comparing these with emerging mechanisms of ER‐phagy and related processes. The text discusses the impact of ER‐phagy on the function of the ER‐ and the cell, both in normal physiology and when dysregulated within disease settings. Finally, unanswered questions regarding the mechanisms and significance of ER‐phagy are highlighted.

Dual Role of Autophagy in Diseases of the Central Nervous System

Autophagy is a vital lysosomal degradation and recycling pathway in the eukaryotic cell, responsible for maintaining an intricate balance between cell survival and cell death, necessary for neuronal survival and function. This dual role played by autophagy raises the question whether this process is a protective or a destructive pathway, the contributor of neuronal cell death or a failed attempt to repair aberrant processes? Deregulated autophagy at different steps of the pathway, whether excessive or downregulated, has been proposed to be associated with neurodegenerative disorders such as Alzheimer's-, Huntington's-, and Parkinson's-disease, known for their intracellular accumulation of protein aggregates. Recent observations of impaired autophagy also appeared in psychiatric disorders such as schizophrenia and bipolar disorder suggesting an additional contribution to the pathophysiology of mental illness. Here we review the current understanding of autophagy's role in various neuropsychiatric disorders and, hitherto, the prevailing new potential autophagy-related therapeutic strategies for their treatment.

Cigarette smoke extract may induce lysosomal storage disease-like adverse health effects

Cigarette smoke is known to be associated with the incidence of a variety of pulmonary diseases, and alveolar macrophages are a key player in the defense mechanism against inhalable toxicants. Herein, we have found that a hydrophilic fraction in smoke extracts from 3R4F reference cigarettes (CSE) contains high concentrations of volatile substances compared to cigarette smoke condensate (amphoteric fraction). We also identified the toxic mechanism of CSE using MH-S, a mouse alveolar macrophage cell line. CSE decreased cell viability accompanying increased lactate dehydrogenase release. Additionally, mitochondrial volume and the potential increased along with enhanced expression of mitochondrial fusion proteins and decreased adenosine triphosphate production. Similarly, CSE clearly induced increase of catalase activity and intracellular calcium concentration and decrease of endoplasmic reticulum and lysosome volume at the highest dose. More interestingly, damaged organelles accumulated in the cytosol, and CSE-containing particles specifically penetrated to mitochondria. Meanwhile, any significant change in autophagy related protein expression was not found in CSE-treated cells. Subsequently, we evaluated the effects of CSE on secretion of inflammatory related cytokines and chemokines, considering the relationship between organelle damage and the disturbed immune response. Very importantly, we found that expression of innate and adaptive immunity related mediators is disrupted following CSE exposure. Taken together, we suggest that CSE may cause the accumulation of damaged organelles in the cytoplasm by impairing selective autophagic function. In addition, this accumulation is responsible for the inadequate ability of immune cells to repair the damage of lung tissue following exposure to CSE.

New Insights on Intermediary Metabolism for a Better Understanding of Nutrition in Teleosts

The rapid development of aquaculture production throughout the world over the past few decades has led to the emergence of new scientific challenges to improve fish nutrition. The diet formulations used for farmed fish have been largely modified in the past few years. However, bottlenecks still exist in being able to suppress totally marine resources (fish meal and fish oil) in diets without negatively affecting growth performance and flesh quality. A better understanding of fish metabolism and its regulation by nutrients is thus mandatory. In this review, we discuss four fields of research that are highly important for improving fish nutrition in the future: ( a) fish genome complexity and subsequent consequences for metabolism, ( b) microRNAs (miRNAs) as new actors in regulation of fish metabolism, ( c) the role of autophagy in regulation of fish metabolism, and ( d) the nutritional programming of metabolism linked to the early life of fish.

Synergistic anticancer effect of acteoside and temozolomide-based glioblastoma chemotherapy

Temozolomide (TMZ) is an alkylating agent commonly used as a first‑line treatment for high‑grade glioblastoma. However, TMZ has short half‑life and frequently induces tumor resistance, which can limit its therapeutic efficiency. In the present study, it was hypothesized that combined treatment with TMZ and acteoside has synergistic effects in glioblastoma therapy. Using cell viability and wound‑healing assays, it was determined that this treatment regimen reduced cell viability and migration to a greater extent than either TMZ or acteoside alone. Following previous reports that TMZ affected autophagy in glioma cells, the present study examined the effects of TMZ + acteoside combination treatment on apoptosis and autophagy. The TMZ + acteoside combination treatment increased the cleavage of caspase‑3 and levels of B‑cell lymphoma 2 (Bcl‑2)‑associated X protein and phosphorylated p53, and decreased the level of Bcl‑2. The combination treatment increased microtubule‑associated protein 1 light chain 3 and apoptosis‑related gene expression. It was also determined that TMZ + acteoside induced apoptosis and autophagy through the mitogen‑activated protein kinase signaling pathway. These findings suggest that acteoside has beneficial effects on TMZ‑based glioblastoma therapy.

Influence of Hydrogen-rich Saline on Hepatocyte Autophagy During Laparoscopic Liver Ischaemia-reperfusion Combined Resection Injury in Miniature Pigs

Introduction

The purpose of this study was to investigate the protective effect of hydrogen-rich saline (HRS) against liver ischaemia-reperfusion combined resection injury.

Material and Methods

Eighteen miniature pigs were randomly divided into three groups: a sham operated group (sham group, laparoscopic liver ischaemia-reperfusion combined resection injury group (IRI group), and a hydrogen-rich saline intervention group (IRI + HRS group). Samples of hepatic tissue and serum were collected at the time of reperfusion and then 3 h, 1 d, and 3 d post reperfusion. Liver function, oxidative stress, autophagy-related mRNA genes, and protein expression were evaluated. Changes in cell and tissue ultrastructure were examined by transmission electron microscopy.

Results

Compared with the sham group, the level of autophagy of hepatocytes increased in the IRI and IRI + HRS groups, corresponding to high oxidative stress and severe liver function injury. Liver function, antioxidant content, autophagy levels, and liver injury were improved after intervention with HRS in the IRI + HRS group compared with the IRI group.

Conclusion

Intervention with hydrogen-rich saline could exert a protective effect against liver ischaemia-reperfusion combined resection injury through the reduction of oxidative stress and hepatocyte autophagy.

Autophagy: The Last Defense against Cellular Nutritional Stress

Homeostasis of nutrient metabolism is critical for maintenance of the normal physiologic status of the cell and the integral health of humans and mammals. In vivo, there is a highly efficient and precise process involved in nutrient recycling and organelle cleaning. This process is named autophagy, and it can be induced in response to the dynamic change of nutrients. When cells face nutritional stress, such as stress caused by nutrient deficiency or nutrient excess, the autophagy pathway will be activated. Generally, when nutrients are withdrawn, cells will sense the signs of starvation and respond. AMP-activated protein kinase and the mammalian target of rapamycin, two of the major metabolic kinases, are responsible for monitoring cellular energy and the concentration of amino acids, respectively. Nutrient excess also induces autophagy, mainly via the reactive oxygen species and endoplasmic reticulum stress pathway. When nutritional stress activates the autophagy pathway, the nutrients or damaged organelles will be recycled for cell survival. However, if autophagy is overwhelmingly induced, autophagic cell death will possibly occur. The balance of the autophagy induction is the crucial factor for cell survival or death. Herein, we summarize the current knowledge on the induction of autophagy, the autophagy response under nutritional stresses, and autophagic cell death and related diseases, which will highlight the process of nutritional stress-induced autophagy and its important physiologic and/or pathologic roles in cell metabolism and diseases, and shed light on the research into the mechanism and clinical applications of autophagy induced by nutritional stresses.

Autophagy and lysosomal pathways in nervous system disorders

Autophagy is an evolutionarily conserved pathway for delivering cytoplasmic cargo to lysosomes for degradation. In its classically studied form, autophagy is a stress response induced by starvation to recycle building blocks for essential cellular processes. In addition, autophagy maintains basal cellular homeostasis by degrading endogenous substrates such as cytoplasmic proteins, protein aggregates, damaged organelles, as well as exogenous substrates such as bacteria and viruses. Given their important role in homeostasis, autophagy and lysosomal machinery are genetically linked to multiple human disorders such as chronic inflammatory diseases, cardiomyopathies, cancer, and neurodegenerative diseases. Multiple targets within the autophagy and lysosomal pathways offer therapeutic opportunities to benefit patients with these disorders. Here, I will summarize the mechanisms of autophagy pathways, the evidence supporting a pathogenic role for disturbed autophagy and lysosomal degradation in nervous system disorders, and the therapeutic potential of autophagy modulators in the clinic.

Is Huntingtin Dispensable in the Adult Brain?

Huntingtin (HTT) is an essential protein during early embryogenesis and the development of the central nervous system (CNS). Conditional knock-out of mouse Huntingtin (Htt) expression in the CNS beginning during neural development, as well as reducing Htt expression only during embryonic and early postnatal stages, results in neurodegeneration in the adult brain. These findings suggest that HTT is important for the development and/or maintenance of the CNS, but they do not address the question of whether HTT is required specifically in the adult CNS for its normal functions and/or homeostasis. Recently, it was reported that although removing Htt expression in young adult mice causes lethality due to acute pancreatitis, loss of Htt expression in the adult brain is well tolerated and does not result in either motor deficits or neurodegeneration for up to 7 months after Htt inactivation. However, recent studies have also demonstrated that HTT participates in several cellular functions that are important for neuronal homeostasis and survival including sensing reactive oxygen species (ROS), DNA damage repair, and stress responses, in addition to its role in selective macroautophagy. In this review, HTT's functions in development and in the adult CNS will be discussed in the context of these recent discoveries, together with a discussion of their potential impact on the design of therapeutic strategies for Huntington's disease (HD) aimed at lowering total HTT expression.

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.

Arginine vasopressin ameliorates spatial learning impairments in chronic cerebral hypoperfusion via V1a receptor and autophagy signaling partially

Chronic cerebral hypoperfusion (CCH) is a major factor contributing to neurological disorders and cognitive decline. Autophagy activation is believed to provide both beneficial and detrimental roles during hypoxic/ischemic cellular injury. Although arginine vasopressin (AVP) has been strongly involved in many behaviors, especially in learning and memory, the effects of AVP on CCH and their molecular mechanisms remain unclear. Here, to investigate whether there was neuroprotective effects of AVP on CCH through V1a receptor (an AVP receptor) signaling, permanent bilateral carotid arteries occlusion (two vessel occlusion, 2VO) was used to establish a rat model of CCH, and hypertonic saline (5.3%) was injected intraperitoneally to induce the secretion of AVP. Results showed that hypertonic saline effectively alleviated spatial learning and memory deficit, enhanced synaptic plasticity of CA3-CA1 hippocampal synapses, upregulated N-methyl-d-aspartate receptor subunit 2B (NR2B) and postsynaptic density protein 95 (PSD-95) surface expressions, reduced oxidative stress and increased Nissl bodies in 2VO model rats. These phenomena were significantly decreased by V1a receptor antagonist SR49059. Interestingly, hypertonic saline also upregulated autophagy in the hippocampus of 2VO rats partly through V1a receptor. These findings imply that AVP has a beneficial role for the treatment of cognitive impairments partly through V1a receptor signaling in CCH, which is possibly related to improving synaptic plasticity by promoting NR2B and PSD-95 externalization and by enhancing autophagy.

Adiponectin modulates oxidative stress-induced mitophagy and protects C2C12 myoblasts against apoptosis

Adiponectin (APN), also known as apM1, Acrp30, GBP28 and adipoQ, is a circulating hormone that is predominantly produced by adipose tissue. Many pharmacological studies have demonstrated that this protein possesses potent anti-diabetic, anti-atherogenic and anti-inflammatory properties. Although several studies have demonstrated the antioxidative activity of this protein, the regulatory mechanisms have not yet been defined in skeletal muscles. The aim of the present study was to examine the cytoprotective effects of APN against damage induced by oxidative stress in mouse-derived C2C12 myoblasts. APN attenuated H₂O₂-induced growth inhibition and exhibited scavenging activity against intracellular reactive oxygen species that were induced by H₂O₂. Furthermore, treating C2C12 cells with APN significantly induced heme oxygenase-1 (HO-1) and nuclear factor-erythroid 2 related factor 2 (Nrf2). APN also suppressed H₂O₂-induced mitophagy and partially inhibited the colocalization of mitochondria with autophagosomes/lysosomes, correlating with the expression of Pink1 and Parkin and mtDNA. Moreover, APN protected C2C12 myoblasts against oxidative stress-induced apoptosis. Furthermore, APN significantly reduced the mRNA and protein expression levels of Bax. These data suggest that APN has a moderate regulatory role in oxidative stress-induced mitophagy and suppresses apoptosis. These findings demonstrate the antioxidant potential of APN in oxidative stress-associated skeletal muscle diseases.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Asparagine slows down the breakdown of storage lipid and degradation of autophagic bodies in sugar-starved embryo axes of germinating lupin seeds

The research was conducted on embryo axes of yellow lupin (Lupinus luteus L.), white lupin (Lupinus albus L.) and Andean lupin (Lupinus mutabilis Sweet), which were isolated from imbibed seeds and cultured for 96h in vitro under different conditions of carbon and nitrogen nutrition. Isolated embryo axes were fed with 60mM sucrose or were sugar-starved. The effect of 35mM asparagine (a central amino acid in the metabolism of germinating lupin seeds) and 35mM nitrate (used as an inorganic kind of nitrogen) on growth, storage lipid breakdown and autophagy was investigated. The sugar-starved isolated embryo axes contained more total lipid than axes fed with sucrose, and the content of this storage compound was even higher in sugar-starved isolated embryo axes fed with asparagine. Ultrastructural observations showed that asparagine significantly slowed down decomposition of autophagic bodies, and this allowed detailed analysis of their content. We found peroxisomes inside autophagic bodies in cells of sugar-starved Andean lupin embryo axes fed with asparagine, which led us to conclude that peroxisomes may be degraded during autophagy in sugar-starved isolated lupin embryo axes. One reason for the slower degradation of autophagic bodies was the markedly lower lipolytic activity in axes fed with asparagine.

Selective endosomal microautophagy is starvation-inducible in Drosophila

Autophagy delivers cytosolic components to lysosomes for degradation and is thus essential for cellular homeostasis and to cope with different stressors. As such, autophagy counteracts various human diseases and its reduction leads to aging-like phenotypes. Macroautophagy (MA) can selectively degrade organelles or aggregated proteins, whereas selective degradation of single proteins has only been described for chaperone-mediated autophagy (CMA) and endosomal microautophagy (eMI). These 2 autophagic pathways are specific for proteins containing KFERQ-related targeting motifs. Using a KFERQ-tagged fluorescent biosensor, we have identified an eMI-like pathway in Drosophila melanogaster. We show that this biosensor localizes to late endosomes and lysosomes upon prolonged starvation in a KFERQ- and Hsc70-4- dependent manner. Furthermore, fly eMI requires endosomal multivesicular body formation mediated by ESCRT complex components. Importantly, induction of Drosophila eMI requires longer starvation than the induction of MA and is independent of the critical MA genes atg5, atg7, and atg12. Furthermore, inhibition of Tor signaling induces eMI in flies under nutrient rich conditions, and, as eMI in Drosophila also requires atg1 and atg13, our data suggest that these genes may have a novel, additional role in regulating eMI in flies. Overall, our data provide the first evidence for a novel, starvation-inducible, catabolic process resembling endosomal microautophagy in the Drosophila fat body.

The peroxisome as a cell signaling organelle

Peroxisomes participate in lipid metabolism, and are a major source of ROS in the cell. Their importance in cellular energy balance and redox homeostasis is well-established, as is the need to maintain peroxisome homeostasis to prevent pathologies associated with too few, or too many, of these organelles. How cells regulate peroxisome number has remained somewhat elusive. Recently, the tumor suppressors ATM and TSC, which regulate mTORC1 signaling, have been localized to peroxisomes. When activated by peroxisomal ROS, ATM signals to TSC to repress mTORC1 signaling and increase autophagic flux in cells, and also phosphorylates the peroxisomal protein PEX 5 to target peroxisomes for selective autophagy (pexophagy), providing a mechanism for regulation of peroxisomal homeostasis using ROS as a rheostat.

Colletotrichum orbiculare FAM1 Encodes a Novel Woronin Body-Associated Pex22 Peroxin Required for Appressorium-Mediated Plant Infection

The cucumber anthracnose fungus Colletotrichum orbiculare forms specialized cells called appressoria for host penetration. We identified a gene, FAM1, encoding a novel peroxin protein that is essential for peroxisome biogenesis and that associates with Woronin bodies (WBs), dense-core vesicles found only in filamentous ascomycete fungi which function to maintain cellular integrity. The fam1 disrupted mutants were unable to grow on medium containing oleic acids as the sole carbon source and were nonpathogenic, being defective in both appressorium melanization and host penetration. Fluorescent proteins carrying peroxisomal targeting signals (PTSs) were not imported into the peroxisomes of fam1 mutants, suggesting that FAM1 is a novel peroxisomal biogenesis gene (peroxin). FAM1 did not show significant homology to any Saccharomyces cerevisiae peroxins but resembled conserved filamentous ascomycete-specific Pex22-like proteins which contain a predicted Pex4-binding site and are potentially involved in recycling PTS receptors from peroxisomes to the cytosol. C. orbiculare FAM1 complemented the peroxisomal matrix protein import defect of the S. cerevisiae pex22 mutant. Confocal microscopy of Fam1-GFP (green fluorescent protein) fusion proteins and immunoelectron microscopy with anti-Fam1 antibodies showed that Fam1 localized to nascent WBs budding from peroxisomes and mature WBs. Association of Fam1 with WBs was confirmed by colocalization with WB matrix protein CoHex1 (C. orbiculare Hex1) and WB membrane protein CoWsc (C. orbiculare Wsc) and by subcellular fractionation and Western blotting with antibodies to Fam1 and CoHex1. In WB-deficient cohex1 mutants, Fam1 was redirected to the peroxisome membrane. Our results show that Fam1 is a WB-associated peroxin required for pathogenesis and raise the possibility that localized receptor recycling occurs in WBs.

IMPORTANCE

Colletotrichum orbiculare is a fungus causing damaging disease on Cucurbitaceae plants. In this paper, we characterize a novel peroxisome biogenesis gene from this pathogen called FAM1. Although no genes with significant homology are present in Saccharomyces cerevisiae, FAM1 contains a predicted Pex4-binding site typical of Pex22 proteins, which function in the recycling of PTS receptors from peroxisomes to the cytosol. We show that FAM1 complements the defect in peroxisomal matrix protein import of S. cerevisiae pex22 mutants and that fam1 mutants are completely defective in peroxisome function, fatty acid metabolism, and pathogenicity. Remarkably, we found that this novel peroxin is specifically localized on the bounding membrane of Woronin bodies, which are small peroxisome-derived organelles unique to filamentous ascomycete fungi that function in septal pore plugging. Our finding suggests that these fungi have coopted the Woronin body for localized receptor recycling during matrix protein import.

ATM functions at the peroxisome to induce pexophagy in response to ROS

Peroxisomes are highly metabolic, autonomously replicating organelles that generate ROS as a by product of fatty acid β-oxidation. Consequently, cells must maintain peroxisome homeostasis, or risk pathologies associated with too few peroxisomes, such as peroxisome biogenesis disorders, or too many peroxisomes, inducing oxidative damage and promoting diseases such as cancer. We report that the PEX5 peroxisome import receptor binds ataxia-telangiectasia mutated (ATM) and localizes this kinase to the peroxisome. In response to reactive oxygen species (ROS), ATM signaling activates ULK1 and inhibits mTORC1 to induce autophagy. Specificity for autophagy of peroxisomes (pexophagy) is provided by ATM phosphorylation of PEX5 at Ser141, which promotes PEX5 mono-ubiquitination at K209, and recognition of ubiquitinated PEX5 by the autophagy adapter protein p62, directing the autophagosome to peroxisomes to induce pexophagy. These data reveal an important new role for ATM in metabolism as a sensor of ROS that regulates pexophagy.

Inhibitory effects of Guben Yiliu Formula II (II) and its blood activation prescriptions on the growth of MCF-7 human breast cancer xenografts in nude mice

OBJECTIVE

To investigate the inhibitory effects of Guben Yiliu Formula II(II, GFII) and its blood activation prescription (BAP) on the growth of MCF-7 human breast cancer xenografts in nude mice, and explore their mechanisms of action.

METHODS

After the establishment of the MCF-7 human breast cancer xenograft model in nude mice, the mice in the GFII and BAP groups were administered with GFII (6.56 g/mL) and BAP (1.65 g/mL) by gavage for 28 days, respectively. The tumor volume and weight were measured twice a week throughout the treatment period. Apoptotic cells were identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. The expression of microtubule associated protein 1 light chain 3 (LC3) was examined by immunohistochemistry, and Western blotting analysis was performed to detect the expression of anti-apoptotic protein Bcl-2 and LC3, as well as the effects on phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway.

RESULTS

Compared with the control group, the GFII and BAP groups could significantly inhibit the growth of MCF-7 human breast cancer xenografts in nude mice. The expression of Bcl-2 protein was lower in the GFII and BAP than in the control group, whereas both the percentage of apoptotic cells and LC3-II/LC3-I ratio were higher than in the control group. In addition, significantly reduced expression of phospho-Akt, phosphor-mTOR and mTOR were observed in the blood activation group (P<0.05).

CONCLUSIONS

To some extent, the GFII and its BAP can exert their inhibitory effect on the growth of MCF-7 human breast cancer xenografts by inducing the cell apoptosis and autophagy. In addition to the induction of cell apoptosis, we also found that the BAP of GFII could induce cell autophagy by inhibiting of PI3K/Akt/mTOR signaling pathway, and then suppress the breast cancer cell growth.

Plant peroxisomes are degraded by starvation-induced and constitutive autophagy in tobacco BY-2 suspension-cultured cells

Very recently, autophagy has been recognized as an important degradation pathway for quality control of peroxisomes in Arabidopsis plants. To further characterize the role of autophagy in plant peroxisome degradation, we generated stable transgenic suspension-cultured cell lines of heterotrophic Nicotiana tabacum L. cv. Bright Yellow 2 expressing a peroxisome-targeted version of enhanced yellow fluorescent protein. Indeed, this cell line model system proved advantageous for detailed cytological analyses of autophagy stages and for quantification of cellular peroxisome pools under different culturing conditions and upon inhibitor applications. Complementary biochemical, cytological, and pharmacological analyses provided convincing evidence for peroxisome degradation by bulk autophagy during carbohydrate starvation. This degradation was slowed down by the inhibitor of autophagy, 3-methyladenine (3-MA), but the 3-MA effect ceased at advanced stages of starvation, indicating that another degradation mechanism for peroxisomes might have taken over. 3-MA also caused an increase particularly in peroxisomal proteins and cellular peroxisome numbers when applied under nutrient-rich conditions in the logarithmic growth phase, suggesting a high turnover rate for peroxisomes by basal autophagy under non-stress conditions. Together, our data demonstrate that a great fraction of the peroxisome pool is subject to extensive autophagy-mediated turnover under both nutrient starvation and optimal growth conditions. Our analyses of the cellular pool size of peroxisomes provide a new tool for quantitative investigations of the role of plant peroxisomes in reactive oxygen species metabolism.

A sterol-enriched vacuolar microdomain mediates stationary phase lipophagy in budding yeast

During stationary phase growth in yeast, a feed-forward loop exists in which lipophagy stimulates vacuolar microdomain formation, which, in turn, further promotes lipophagy.

Stationary phase (stat-phase) is a poorly understood physiological state under which cells arrest proliferation and acquire resistance to multiple stresses. Lipid droplets (LDs), organelles specialized for cellular lipid homeostasis, increase in size and number at the onset of stat-phase. However, little is known about the dynamics of LDs under this condition. In this paper, we reveal the passage of LDs from perinuclear endoplasmic reticulum association to entry into vacuoles during the transition to stat-phase. We show that the process requires the core autophagy machinery and a subset of autophagy-related (Atg) proteins involved in selective autophagy. Notably, the process that we term stat-phase lipophagy is mediated through a sterol-enriched vacuolar microdomain whose formation and integrity directly affect LD translocation. Intriguingly, cells defective in stat-phase lipophagy showed disrupted vacuolar microdomains, implying that LD contents, likely sterol esters, contribute to the maintenance of vacuolar microdomains. Together, we propose a feed-forward loop in which lipophagy stimulates vacuolar microdomain formation, which in turn promotes lipophagy during stat-phase.

How Parkinsonian toxins dysregulate the autophagy machinery

Since their discovery, Parkinsonian toxins (6-hydroxydopamine, MPP+, paraquat, and rotenone) have been widely employed as in vivo and in vitro chemical models of Parkinson's disease (PD). Alterations in mitochondrial homeostasis, protein quality control pathways, and more recently, autophagy/mitophagy have been implicated in neurotoxin models of PD. Here, we highlight the molecular mechanisms by which different PD toxins dysregulate autophagy/mitophagy and how alterations of these pathways play beneficial or detrimental roles in dopamine neurons. The convergent and divergent effects of PD toxins on mitochondrial function and autophagy/mitophagy are also discussed in this review. Furthermore, we propose new diagnostic tools and discuss how pharmacological modulators of autophagy/mitophagy can be developed as disease-modifying treatments for PD. Finally, we discuss the critical need to identify endogenous and synthetic forms of PD toxins and develop efficient health preventive programs to mitigate the risk of developing PD.

Function of peroxisomes in plant-pathogen interactions

Peroxisomes are ubiquitous organelles of eukaryotic cells that accomplish a variety of biochemical functions, including β-oxidation of fatty acids, glyoxylate cycle, etc. Many reports have been accumulating that indicate peroxisome related metabolic functions are essential for pathogenic development of plant pathogenic fungi. They include peroxisome biogenesis proteins, peroxins and preferential destruction of peroxisomes, pexophagy. Gene disrupted mutants of anthracnose disease pathogen Colletotrichum orbiculare or rice blast pathogen Magnaporthe oryzae defective in peroxins or pexophagy showed deficiency in pathogenesis. Woronin body, a peroxisome related cellular organelle that is related to endurance of fungal cells against environmental damage has essential roles in pathogenesis of M. oryzae. Also, peroxisome related metabolisms such as β-oxidation and glyoxylate cycle are essential for pathogenesis in several plant pathogenic fungi. In addition, secondary metabolisms including polyketide melanin biosynthesis of C. orbiculare and M. oryzae, and host selective toxins produced by necrotrophic pathogen Alternaria alternata have pivotal roles in fungal pathogenesis. Every such factor was listed and their functions for pathogenesis were demonstrated (Table 18.1 and Fig. 18.1).

Increased levels of reduced cytochrome b and mitophagy components are required to trigger nonspecific autophagy following induced mitochondrial dysfunction

Mitochondria are essential organelles producing most of the energy required for the cell. A selective autophagic process called mitophagy removes damaged mitochondria, which is critical for proper cellular homeostasis; dysfunctional mitochondria can generate excess reactive oxygen species that can further damage the organelle as well as other cellular components. Although proper cell physiology requires the maintenance of a healthy pool of mitochondria, little is known about the mechanism underlying the recognition and selection of damaged organelles. In this study, we investigated the cellular fate of mitochondria damaged by the action of respiratory inhibitors (antimycin A, myxothiazol, KCN) that act on mitochondrial respiratory complexes III and IV, but have different effects with regard to the production of reactive oxygen species and increased levels of reduced cytochromes. Antimycin A and potassium cyanide effectively induced nonspecific autophagy, but not mitophagy, in a wild-type strain of Saccharomyces cerevisiae; however, low or no autophagic activity was measured in strains deficient for genes that encode proteins involved in mitophagy, including ATG32, ATG11 and BCK1. These results provide evidence for a major role of specific mitophagy factors in the control of a general autophagic cellular response induced by mitochondrial alteration. Moreover, increased levels of reduced cytochrome b, one of the components of the respiratory chain, could be the first signal of this induction pathway.

Inflammatory cause of metabolic syndrome via brain stress and NF-κB

Metabolic syndrome, a network of medical disorders that greatly increase the risk for developing metabolic and cardiovascular diseases, has reached epidemic levels in many areas of today's world. Despite this alarming medicare situation, scientific understandings on the root mechanisms of metabolic syndrome are still limited, and such insufficient knowledge contributes to the relative lack of effective treatments or preventions for related diseases. Recent interdisciplinary studies from neuroendocrinology and neuroimmunology fields have revealed that overnutrition can trigger intracellular stresses to cause inflammatory changes mediated by molecules that control innate immunity. This type of nutrition-related molecular inflammation in the central nervous system, particularly in the hypothalamus, can form a common pathogenic basis for the induction of various metabolic syndrome components such as obesity, insulin resistance, and hypertension. Proinflammatory NF-κB pathway has been revealed as a key molecular system for pathologic induction of brain inflammation, which translates overnutrition and resulting intracellular stresses into central neuroendocrine and neural dysregulations of energy, glucose, and cardiovascular homeostasis, collectively leading to metabolic syndrome. This article reviews recent research advances in the neural mechanisms of metabolic syndrome and related diseases from the perspective of pathogenic induction by intracellular stresses and NF-κB pathway of the brain.

Cannabinoid-associated cell death mechanisms in tumor models (review)

In recent years, cannabinoids (the active components of Cannabis sativa) and their derivatives have received considerable interest due to findings that they can affect the viability and invasiveness of a variety of different cancer cells. Moreover, in addition to their inhibitory effects on tumor growth and migration, angiogenesis and metastasis, the ability of these compounds to induce different pathways of cell death has been highlighted. Here, we review the most recent results generating interest in the field of death mechanisms induced by cannabinoids in cancer cells. In particular, we analyze the pathways triggered by cannabinoids to induce apoptosis or autophagy and investigate the interplay between the two processes. Overall, the results reported here suggest that the exploration of molecular mechanisms induced by cannabinoids in cancer cells can contribute to the development of safe and effective treatments in cancer therapy.