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Cells Apr 2020Microautophagy is a type of autophagy. It is characterized by direct enclosing with the vacuolar/lysosomal membrane, which completes the isolation and uptake of cell... (Review)
Review
Microautophagy is a type of autophagy. It is characterized by direct enclosing with the vacuolar/lysosomal membrane, which completes the isolation and uptake of cell components in the vacuole. Several publications present evidence that plants exhibit microautophagy. Plant microautophagy is involved in anthocyanin accumulation in the vacuole, eliminating damaged chloroplasts and degrading cellular components during starvation. However, information on the molecular mechanism of microautophagy is less available than that on the general macroautophagy, because the research focusing on microautophagy has not been widely reported. In yeast and animals, it is suggested that microautophagy can be classified into several types depending on morphology and the requirements of autophagy-related () genes. This review summarizes the studies on plant microautophagy and discusses possible techniques for a future study in this field while taking into account the information on microautophagy obtained from yeast and animals.
Topics: Animals; Microautophagy; Models, Biological; Plant Proteins; Plants; Saccharomyces cerevisiae
PubMed: 32260410
DOI: 10.3390/cells9040887 -
Journal of Cell Science Sep 2020Autophagy is fundamental for cell and organismal health. Two types of autophagy are conserved in eukaryotes: macroautophagy and microautophagy. During macroautophagy,... (Review)
Review
Autophagy is fundamental for cell and organismal health. Two types of autophagy are conserved in eukaryotes: macroautophagy and microautophagy. During macroautophagy, autophagosomes deliver cytoplasmic constituents to endosomes or lysosomes, whereas during microautophagy lytic organelles take up cytoplasm directly. While macroautophagy has been investigated extensively, microautophagy has received much less attention. Nonetheless, it has become clear that microautophagy has a broad range of functions in biosynthetic transport, metabolic adaptation, organelle remodeling and quality control. This Review discusses the selective and non-selective microautophagic processes known in yeast, plants and animals. Based on the molecular mechanisms for the uptake of microautophagic cargo into lytic organelles, I propose to distinguish between fission-type microautophagy, which depends on ESCRT proteins, and fusion-type microautophagy, which requires the core autophagy machinery and SNARE proteins. Many questions remain to be explored, but the functional versatility and mechanistic diversity of microautophagy are beginning to emerge.
Topics: Animals; Autophagy; Endosomes; Lysosomes; Microautophagy; Saccharomyces cerevisiae
PubMed: 32907930
DOI: 10.1242/jcs.246322 -
Cell Biology International Mar 2020Peroxisomicine A1 (PA1) is a potential antineoplastic agent with high and selective toxicity toward peroxisomes of tumor cells. Pexophagy is a selective autophagy...
Peroxisomicine A1 (PA1) is a potential antineoplastic agent with high and selective toxicity toward peroxisomes of tumor cells. Pexophagy is a selective autophagy process that degrades damaged peroxisomes; this process has been studied mainly in methylotrophic yeasts. There are two main modes of pexophagy in yeast: macropexophagy and micropexophagy. Previous studies showed that peroxisomes damaged by a prolonged exposition to PA1 are eliminated by macropexophagy. In this work, Candida boidinii was grown in methanol-containing media, and PA1 was added to the cultures at 2 µg/mL after they reached the mid-exponential growth phase. Samples were taken at 5, 10, 15, 20, and 25 min after the addition of PA1 and processed for ultrastructural analysis. Typical morphological characteristics of micropexophagy were observed: the direct engulfment of peroxisomes by the vacuolar membrane and the presence of the micropexophagic membrane apparatus (MIPA), which mediates the fusion between the opposing tips of the vacuole to complete sequestration of peroxisomes from the cytosol. In conclusion, here we report that, in addition to macropexophagy, peroxisomes damaged by PA1 can be eliminated by micropexophagy. This information is useful to deepen the knowledge of the mechanism of action of PA1 and of that of pexophagy per se.
Topics: Anthracenes; Antineoplastic Agents; Candida; Fungal Proteins; Macroautophagy; Microautophagy; Peroxisomes
PubMed: 31814220
DOI: 10.1002/cbin.11280 -
Biomolecules Dec 2022Atherosclerosis (AS) is a lipid-driven disorder of the artery intima characterized by the equilibrium between inflammatory and regressive processes. A protein complex... (Review)
Review
Atherosclerosis (AS) is a lipid-driven disorder of the artery intima characterized by the equilibrium between inflammatory and regressive processes. A protein complex called NLRP3 inflammasome is involved in the release of mature interleukin-1β (IL-1β), which is connected to the initiation and progression of atherosclerosis. Autophagy, which includes macroautophagy, chaperone-mediated autophagy (CMA), and microautophagy, is generally recognized as the process by which cells transfer their constituents to lysosomes for digestion. Recent studies have suggested a connection between vascular inflammation and autophagy. This review summarizes the most recent studies and the underlying mechanisms associated with different autophagic pathways and NLRP3 inflammasomes in vascular inflammation, aiming to provide additional evidence for atherosclerosis research.
Topics: Humans; Inflammasomes; Plaque, Atherosclerotic; NLR Family, Pyrin Domain-Containing 3 Protein; Autophagy; Atherosclerosis; Inflammation
PubMed: 36671400
DOI: 10.3390/biom13010015 -
Autophagy Oct 2020Selective autophagy is critical for the regulation of cellular homeostasis in organisms from yeast to humans. This process is a specific degradation pathway for a wide...
UNLABELLED
Selective autophagy is critical for the regulation of cellular homeostasis in organisms from yeast to humans. This process is a specific degradation pathway for a wide variety of substrates including unwanted cytosolic components, such as protein aggregates, damaged and/or superfluous organelles, and pathogens. However, it has been less clear as to whether a protein complex or substructure of an organelle can be targeted for removal by selective autophagy. One example of such a substrate is the nuclear pore complex (NPC), a large macromolecular assembly that is present throughout the nuclear envelope. Here, we highlight two recent studies that demonstrate for the first time that NPCs are targeted for vacuolar degradation through selective autophagy.
ABBREVIATIONS
AIM: Atg8-interacting motif; NE: nuclear envelope; NPC: nuclear pore complex; Nup: nucleoporin; PMN/micronucleophagy: piecemeal microautophagy of the nucleus.
Topics: Autophagy; Cell Nucleus; Cytosol; Macroautophagy; Nuclear Envelope; Nuclear Pore; Nuclear Pore Complex Proteins; Organelles; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Vacuoles
PubMed: 32713250
DOI: 10.1080/15548627.2020.1798199 -
Biomolecules & Therapeutics Jul 2021The gastrointestinal (GI) tract is a series of hollow organs that is responsible for the digestion and absorption of ingested foods and the excretion of waste. Any... (Review)
Review
The gastrointestinal (GI) tract is a series of hollow organs that is responsible for the digestion and absorption of ingested foods and the excretion of waste. Any changes in the GI tract can lead to GI disorders. GI disorders are highly prevalent in the population and account for substantial morbidity, mortality, and healthcare utilization. GI disorders can be functional, or organic with structural changes. Functional GI disorders include functional dyspepsia and irritable bowel syndrome. Organic GI disorders include inflammation of the GI tract due to chronic infection, drugs, trauma, and other causes. Recent studies have highlighted a new explanatory mechanism for GI disorders. It has been suggested that autophagy, an intracellular homeostatic mechanism, also plays an important role in the pathogenesis of GI disorders. Autophagy has three primary forms: macroautophagy, microautophagy, and chaperone-mediated autophagy. It may affect intestinal homeostasis, host defense against intestinal pathogens, regulation of the gut microbiota, and innate and adaptive immunity. Drugs targeting autophagy could, therefore, have therapeutic potential for treating GI disorders. In this review, we provide an overview of current understanding regarding the evidence for autophagy in GI diseases and updates on potential treatments, including drugs and complementary and alternative medicines.
PubMed: 34127572
DOI: 10.4062/biomolther.2021.086 -
International Journal of Molecular... Mar 2021Historically, studies of intracellular membrane trafficking have focused on the secretory and endocytic pathways and their major organelles. However, these pathways are... (Review)
Review
Historically, studies of intracellular membrane trafficking have focused on the secretory and endocytic pathways and their major organelles. However, these pathways are also directly implicated in the biogenesis and function of other important intracellular organelles, the best studied of which are peroxisomes and lipid droplets. There is a large recent body of work on these organelles, which have resulted in the introduction of new paradigms regarding the roles of membrane trafficking organelles. In this review, we discuss the roles of membrane trafficking in the life cycle of lipid droplets. This includes the complementary roles of lipid phase separation and proteins in the biogenesis of lipid droplets from endoplasmic reticulum (ER) membranes, and the attachment of mature lipid droplets to membranes by lipidic bridges and by more conventional protein tethers. We also discuss the catabolism of neutral lipids, which in part results from the interaction of lipid droplets with cytosolic molecules, but with important roles for both macroautophagy and microautophagy. Finally, we address their eventual demise, which involves interactions with the autophagocytotic machinery. We pay particular attention to the roles of small GTPases, particularly Rab18, in these processes.
Topics: Animals; Autophagy; Biological Transport; Endoplasmic Reticulum; Humans; Intracellular Membranes; Lipid Droplets; rab GTP-Binding Proteins
PubMed: 33803444
DOI: 10.3390/ijms22052776 -
Frontiers in Oncology 2020Chaperone-mediated autophagy (CMA) represents a specific way of lysosomal protein degradation and contrary to macro and microautophagy is independent of vesicles... (Review)
Review
Chaperone-mediated autophagy (CMA) represents a specific way of lysosomal protein degradation and contrary to macro and microautophagy is independent of vesicles formation. The role of CMA in different physiopathological processes has been studied for several years. In cancer, alterations of the CMA principal components, Hsc70 and Lamp2A protein and mRNA levels, have been described in malignant cells. However, changes in the expression levels of these CMA components are not always associated with changes in CMA activity and their biological significance must be carefully interpreted case by case. The objective of this review is to discuss whether altering the CMA activity, CMA substrates or CMA components is accurate to avoid cancer progression. In particular, this review will discuss about the evidences in which alterations CMA components Lamp2A and Hsc70 are associated or not with changes in CMA activity in different cancer types. This analysis will help to better understand the role of CMA activity in cancer and to elucidate whether CMA can be considered as target for therapeutics. Further, it will help to define whether the attention of the investigation should be focused on Lamp2A and Hsc70 because they can have an independent role in cancer progression beyond of their participation in altered CMA activity.
PubMed: 33643916
DOI: 10.3389/fonc.2020.614677 -
Aging Cell Oct 2022Autophagy is essential for protein quality control and regulation of the functional proteome. Failure of autophagy pathways with age contributes to loss of proteostasis...
Autophagy is essential for protein quality control and regulation of the functional proteome. Failure of autophagy pathways with age contributes to loss of proteostasis in aged organisms and accelerates the progression of age-related diseases. In this work, we show that activity of endosomal microautophagy (eMI), a selective type of autophagy occurring in late endosomes, declines with age and identify the sub-proteome affected by this loss of function. Proteomics of late endosomes from old mice revealed an aberrant glycation signature for Hsc70, the chaperone responsible for substrate targeting to eMI. Age-related Hsc70 glycation reduces its stability in late endosomes by favoring its organization into high molecular weight protein complexes and promoting its internalization/degradation inside late endosomes. Reduction of eMI with age associates with an increase in protein secretion, as late endosomes can release protein-loaded exosomes upon plasma membrane fusion. Our search for molecular mediators of the eMI/secretion switch identified the exocyst-RalA complex, known for its role in exocytosis, as a novel physiological eMI inhibitor that interacts with Hsc70 and acts directly at the late endosome membrane. This inhibitory function along with the higher exocyst-RalA complex levels detected in late endosomes from old mice could explain, at least in part, reduced eMI activity with age. Interaction of Hsc70 with components of the exocyst-RalA complex places this chaperone in the switch from eMI to secretion. Reduced intracellular degradation in favor of extracellular release of undegraded material with age may be relevant to the spreading of proteotoxicity associated with aging and progression of proteinopathies.
Topics: Aging; Animals; Autophagy; Endosomes; Lysosomes; Mice; Microautophagy; Protein Transport; Proteome
PubMed: 36116133
DOI: 10.1111/acel.13713 -
Cell Death and Differentiation Mar 2023Inflammation leads to systemic osteoporosis or local bone destruction, however, the underlying molecular mechanisms are still poorly understood. In this study, we report...
Inflammation leads to systemic osteoporosis or local bone destruction, however, the underlying molecular mechanisms are still poorly understood. In this study, we report that PRL2 is a negative regulator of osteoclastogenesis and bone absorption. Mice with PRL2 deficiency exhibit a decrease in bone volume and an increase in osteoclast numbers. PRL2 negatively regulates RANKL-induced reactive oxygen species production through the activation of RAC1, thus PRL2 deficient osteoclast precursors have both increased osteoclast differentiation ability and bone resorptive capacity. During inflammation, oxidized PRL2 is a selected substrate of HSC70 and conditions of oxidative stress trigger rapid degradation of PRL2 by HSC70 mediated endosomal microautophagy and chaperone-mediated autophagy. Ablation of PRL2 in mouse models of inflammatory bone disease leads to an increase in the number of osteoclasts and exacerbation of bone damage. Moreover, reduced PRL2 protein levels in peripheral myeloid cells are highly correlated with bone destruction in a mouse arthritis model and in human rheumatoid arthritis, while the autophagy inhibitor hydroxychloroquine blocked inflammation-induced PRL2 degradation and bone destruction in vivo. Therefore, our findings identify PRL2 as a new regulator in osteoimmunity, providing a link between inflammation and osteoporosis. As such, PRL2 is a potential therapeutic target for inflammatory bone disease and inhibition of HSC70 mediated autophagic degradation of PRL2 may offer new therapeutic tools for the treatment of inflammatory bone disease.
Topics: Animals; Humans; Mice; Autophagy; Bone Resorption; Cell Differentiation; Disease Models, Animal; Inflammation; Osteoclasts; Osteogenesis; Osteoporosis; RANK Ligand; HSC70 Heat-Shock Proteins
PubMed: 36182990
DOI: 10.1038/s41418-022-01068-y