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Advances in Experimental Medicine and... 2021Autophagy is a major intracellular degradation/recycling system that ubiquitously exists in eukaryotic cells. Autophagy contributes to the turnover of cellular...
Autophagy is a major intracellular degradation/recycling system that ubiquitously exists in eukaryotic cells. Autophagy contributes to the turnover of cellular components through engulfing portions of the cytoplasm or organelles and delivering them to the lysosomes/vacuole to be degraded. The trafficking of autophagosomes and their fusion with lysosomes are important steps that complete their maturation and degradation. In cells such as neuron, autophagosomes traffic long distances along the axon, while in other specialized cells such as cardiomyocytes, it is unclear how and even whether autophagosomes are transported. Therefore, it is important to learn more about the processes and mechanisms of autophagosome trafficking to lysosomes/vacuole during autophagy. The mechanisms of autophagosome trafficking are similar to those of other organelles trafficking within cells. The machinery mainly includes cytoskeletal systems such as actin and microtubules, motor proteins such as myosins and the dynein-dynactin complex, and other proteins like LC3 on the membrane of autophagosomes. Factors regulating autophagosome trafficking have not been widely studied. To date the main reagents identified for disrupting autophagosome trafficking include: 1. Microtubule polymerization reagents, which disrupt microtubules by interfering with microtubule dynamics, thus directly influence microtubule-dependent autophagosome trafficking 2. F-actin-depolymerizing drugs, which inhibit autophagosome formation, and also subsequently inhibit autophagosome trafficking 3. Motor protein regulators, which directly affect autophagosome trafficking.
Topics: Autophagosomes; Autophagy; Dyneins; Lysosomes; Microtubules
PubMed: 34260022
DOI: 10.1007/978-981-16-2830-6_5 -
Developmental Cell Dec 2023The sequence of morphological intermediates that leads to mammalian autophagosome formation and closure is a crucial yet poorly understood issue. Previous studies have...
The sequence of morphological intermediates that leads to mammalian autophagosome formation and closure is a crucial yet poorly understood issue. Previous studies have shown that yeast autophagosomes evolve from cup-shaped phagophores with only one closure point, and mammalian studies have inferred that mammalian phagophores also have single openings. Our superresolution microscopy studies in different human cell lines in conditions of basal and nutrient-deprivation-induced autophagy identified autophagosome precursors with multifocal origins that evolved into unexpected finger-like phagophores with multiple openings before becoming more spherical structures. Compatible phagophore structures were observed with whole-mount and conventional electron microscopy. This sequence of events was visualized using advanced SIM superresolution live microscopy. The finger-shaped phagophore apertures remained open when ESCRT function was compromised. The efficient closure of autophagic structures is important for their release from the recycling endosome. This has important implications for understanding how autophagosomes form and capture various cargoes.
Topics: Animals; Humans; Autophagosomes; Autophagy; Endosomes; Cell Line; Phagocytosis; Mammals
PubMed: 37683632
DOI: 10.1016/j.devcel.2023.08.016 -
Cells Aug 2021Autophagy is a conserved self-degradation process that is activated under a wide variety of stresses and physiological conditions [...].
Autophagy is a conserved self-degradation process that is activated under a wide variety of stresses and physiological conditions [...].
Topics: Animals; Apoptosis; Autophagosomes; Autophagy; Autophagy-Related Proteins; Humans; Signal Transduction
PubMed: 34440756
DOI: 10.3390/cells10081987 -
Cells Nov 2022Eukaryotes utilize different communication strategies to coordinate processes between different cellular compartments either indirectly, through vesicular transport, or... (Review)
Review
Eukaryotes utilize different communication strategies to coordinate processes between different cellular compartments either indirectly, through vesicular transport, or directly, via membrane contact sites (MCSs). MCSs have been implicated in lipid metabolism, calcium signaling and the regulation of organelle biogenesis in various cell types. Several studies have shown that MCSs play a crucial role in the regulation of macroautophagy, an intracellular catabolic transport route that is characterized by the delivery of cargoes (proteins, protein complexes or aggregates, organelles and pathogens) to yeast and plant vacuoles or mammalian lysosomes, for their degradation and recycling into basic metabolites. Macroautophagy is characterized by the de novo formation of double-membrane vesicles called autophagosomes, and their biogenesis requires an enormous amount of lipids. MCSs appear to have a central role in this supply, as well as in the organization of the autophagy-related (ATG) machinery. In this review, we will summarize the evidence for the participation of specific MCSs in autophagosome formation, with a focus on the budding yeast and mammalian systems.
Topics: Animals; Endoplasmic Reticulum; Autophagosomes; Autophagy; Lysosomes; Saccharomyces cerevisiae; Mammals
PubMed: 36497073
DOI: 10.3390/cells11233813 -
Autophagy Jun 2024Macroautophagy/autophagy is a highly conserved metabolic process that degrades intracellular components and recycles bioenergetic substrates. SQSTM1/p62 (sequestosome 1)...
Macroautophagy/autophagy is a highly conserved metabolic process that degrades intracellular components and recycles bioenergetic substrates. SQSTM1/p62 (sequestosome 1) is a classical autophagy receptor that participates in selective autophagy to eliminate abnormal intracellular components and recycle bioenergetic substrates. In autophagy, SQSTM1 recruits ubiquitinated substrates to form SQSTM1 droplets and delivers these cargoes to phagophores, the precursors to autophagosomes. Recently, we reported a previously unidentified SQSTM1 -acylation, which is catalyzed by -acyltransferase ZDHHC19 and reversed by LYPLA1/APT1. -acylation of SQSTM1 enhances the affinity of SQSTM1 droplets with the phagophore membrane, thereby promoting efficient autophagic degradation of ubiquitinated substrates. Our study uncovers the role of the -acylation-deacylation cycle in regulating SQSTM1-mediated selective autophagy.
Topics: Sequestosome-1 Protein; Autophagy; Acylation; Humans; Animals; Autophagosomes
PubMed: 38124295
DOI: 10.1080/15548627.2023.2297623 -
Neuron Mar 2022Neurons depend on autophagy to maintain cellular homeostasis, and defects in autophagy are pathological hallmarks of neurodegenerative disease. To probe the role of...
Neurons depend on autophagy to maintain cellular homeostasis, and defects in autophagy are pathological hallmarks of neurodegenerative disease. To probe the role of basal autophagy in the maintenance of neuronal health, we isolated autophagic vesicles from mouse brain tissue and used proteomics to identify the major cargos engulfed within autophagosomes, validating our findings in rodent primary and human iPSC-derived neurons. Mitochondrial proteins were identified as a major cargo in the absence of mitophagy adaptors such as OPTN. We found that nucleoid-associated proteins are enriched compared with other mitochondrial components. In the axon, autophagic engulfment of nucleoid-enriched mitochondrial fragments requires the mitochondrial fission machinery Drp1. We proposed that localized Drp1-dependent fission of nucleoid-enriched fragments in proximity to the sites of autophagosome biogenesis enhances their capture. The resulting efficient autophagic turnover of nucleoids may prevent accumulation of mitochondrial DNA in the neuron, thus mitigating activation of proinflammatory pathways that contribute to neurodegeneration.
Topics: Animals; Autophagosomes; Autophagy; Brain; Mice; Neurodegenerative Diseases; Neurons
PubMed: 35051374
DOI: 10.1016/j.neuron.2021.12.029 -
Cell Research Feb 2022Under stress, the endomembrane system undergoes reorganization to support autophagosome biogenesis, which is a central step in autophagy. How the endomembrane system...
Under stress, the endomembrane system undergoes reorganization to support autophagosome biogenesis, which is a central step in autophagy. How the endomembrane system remodels has been poorly understood. Here we identify a new type of membrane contact formed between the ER-Golgi intermediate compartment (ERGIC) and the ER-exit site (ERES) in the ER-Golgi system, which is essential for promoting autophagosome biogenesis induced by different stress stimuli. The ERGIC-ERES contact is established by the interaction between TMED9 and SEC12 which generates a short distance opposition (as close as 2-5 nm) between the two compartments. The tight membrane contact allows the ERES-located SEC12 to transactivate COPII assembly on the ERGIC. In addition, a portion of SEC12 also relocates to the ERGIC. Through both mechanisms, the ERGIC-ERES contact promotes formation of the ERGIC-derived COPII vesicle, a membrane precursor of the autophagosome. The ERGIC-ERES contact is physically and functionally different from the TFG-mediated ERGIC-ERES adjunction involved in secretory protein transport, and therefore defines a unique endomembrane structure generated upon stress conditions for autophagic membrane formation.
Topics: Autophagosomes; Autophagy; Endoplasmic Reticulum; Golgi Apparatus; Protein Transport
PubMed: 34561617
DOI: 10.1038/s41422-021-00563-0 -
Autophagy Nov 2021It would be quite convenient if every protein had one distinct function, one distinct role in just a single cellular process. In the field of macroautophagy/autophagy,...
It would be quite convenient if every protein had one distinct function, one distinct role in just a single cellular process. In the field of macroautophagy/autophagy, however, we are increasingly finding that this is not the case; several autophagy proteins have two or more roles within the process of autophagy and many even "moonlight" as functional members of entirely different cellular processes. This is perhaps best exemplified by the Atg8-family proteins. These dynamic proteins have already been reported to serve several functions both within autophagy (membrane tethering, membrane fusion, binding to cargo receptors, binding to autophagy machinery) and beyond (LC3-associated phagocytosis, formation of EDEMosomes, immune signaling) but as Maruyama and colleagues suggest in their recent report, this list of functions may not yet be complete.
Topics: Animals; Autophagosomes; Autophagy; Autophagy-Related Protein 8 Family; Binding Sites; Humans; Models, Molecular; Molecular Docking Simulation; Mutation
PubMed: 34482799
DOI: 10.1080/15548627.2021.1967566 -
Progress in Biophysics and Molecular... May 2023Autophagy is a highly conserved intracellular degradation system in eukaryotes that maintains cellular and tissue homeostasis. Upon autophagy induction, cytoplasmic... (Review)
Review
Autophagy is a highly conserved intracellular degradation system in eukaryotes that maintains cellular and tissue homeostasis. Upon autophagy induction, cytoplasmic components are engulfed by a double-membrane organelle called the autophagosome that fuses with a lysosome to degrade its contents. In recent years, it has become clear that autophagy becomes dysregulated with aging, which leads to age-related diseases. Kidney function is particularly prone to age-related decline, and aging is the most significant risk factor for chronic kidney disease. This review first discuss the relationship between autophagy and kidney aging. Second, we describe how age-related dysregulation of autophagy occurs. Finally, we discuss the potential of autophagy-targeting drugs to ameliorate human kidney aging and the approaches necessary to discover such agents.
Topics: Humans; Autophagy; Kidney; Autophagosomes; Aging; Organelles
PubMed: 36849016
DOI: 10.1016/j.pbiomolbio.2023.02.005 -
Nature Communications Aug 2023Organelles are shaped by curvature-generating proteins, which include the reticulons and REEPs that are involved in forming the endoplasmic reticulum (ER). A conserved...
Organelles are shaped by curvature-generating proteins, which include the reticulons and REEPs that are involved in forming the endoplasmic reticulum (ER). A conserved REEP subfamily differs from the ER-shaping REEPs in abundance and membrane topology and has unidentified functions. Here, we show that Rop1, the single member of this family in the fission yeast Schizosacharomyces pombe, is crucial for the macroautophagy of organelles and cytosolic proteins. Rop1 is needed for the formation of phagophores, cup-like structures consisting of two closely apposed membrane sheets that encapsulate cargo. It is recruited at early stages to phagophores and is required for their maturation into autophagosomes. Rop1 function relies on its ability to generate high membrane curvature and on its colocalization with the autophagy component Atg2 that is thought to reside at the phagophore rim. We propose that Rop1 facilitates the formation and growth of the double-membrane structure of the autophagosome.
Topics: Membrane Proteins; Autophagosomes; Schizosaccharomyces; Macroautophagy; Autophagy; Autophagy-Related Proteins
PubMed: 37553386
DOI: 10.1038/s41467-023-40530-4