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ELife Sep 2021Removal of damaged organelles via the process of selective autophagy constitutes a major form of cellular quality control. Damaged organelles are recognized by a...
Removal of damaged organelles via the process of selective autophagy constitutes a major form of cellular quality control. Damaged organelles are recognized by a dedicated surveillance machinery, leading to the assembly of an autophagosome around the damaged organelle, prior to fusion with the degradative lysosomal compartment. Lysosomes themselves are also prone to damage and are degraded through the process of lysophagy. While early steps involve recognition of ruptured lysosomal membranes by glycan-binding galectins and ubiquitylation of transmembrane lysosomal proteins, many steps in the process, and their interrelationships, remain poorly understood, including the role and identity of cargo receptors required for completion of lysophagy. Here, we employ quantitative organelle capture and proximity biotinylation proteomics of autophagy adaptors, cargo receptors, and galectins in response to acute lysosomal damage, thereby revealing the landscape of lysosome-associated proteome remodeling during lysophagy. Among the proteins dynamically recruited to damaged lysosomes were ubiquitin-binding autophagic cargo receptors. Using newly developed lysophagic flux reporters including Lyso-Keima, we demonstrate that TAX1BP1, together with its associated kinase TBK1, are both necessary and sufficient to promote lysophagic flux in both HeLa cells and induced neurons (iNeurons). While the related receptor Optineurin (OPTN) can drive damage-dependent lysophagy when overexpressed, cells lacking either OPTN or CALCOCO2 still maintain significant lysophagic flux in HeLa cells. Mechanistically, TAX1BP1-driven lysophagy requires its N-terminal SKICH domain, which binds both TBK1 and the autophagy regulatory factor RB1CC1, and requires upstream ubiquitylation events for efficient recruitment and lysophagic flux. These results identify TAX1BP1 as a central component in the lysophagy pathway and provide a proteomic resource for future studies of the lysophagy process.
Topics: Autophagy; Humans; Lysosomes; Macroautophagy; Protein Binding; Proteomics; Ubiquitin
PubMed: 34585663
DOI: 10.7554/eLife.72328 -
Autophagy Oct 2022Atherosclerosis, the leading cause of cardiovascular death, is driven by hyperlipidemia, inflammation and aggravated by aging. As chaperone-mediated autophagy (CMA), a...
Atherosclerosis, the leading cause of cardiovascular death, is driven by hyperlipidemia, inflammation and aggravated by aging. As chaperone-mediated autophagy (CMA), a selective type of lysosomal degradation for intracellular proteins, diminishes with age and is inhibited by lipid excess, we studied if the decline in CMA could contribute to atherosclerosis pathogenesis. We found that CMA declines in human and murine vasculature with disease progression. Inhibition and reactivation of CMA using transgenic mouse models establishes a protective effect of CMA against atherogenesis. CMA upregulation ameliorates both systemic metabolic parameters, and vascular cell function. Our work suggests CMA reactivation could be a viable therapeutic strategy to prevent and reduce cardiovascular disease.
Topics: Animals; Atherosclerosis; Autophagy; Chaperone-Mediated Autophagy; Humans; Lipids; Lysosomes; Mice; Mice, Transgenic; Molecular Chaperones
PubMed: 35787098
DOI: 10.1080/15548627.2022.2096397 -
International Journal of Molecular... Nov 2023The liver is the primary organ accountable for complex physiological functions, including lipid metabolism, toxic chemical degradation, bile acid synthesis, and glucose... (Review)
Review
The liver is the primary organ accountable for complex physiological functions, including lipid metabolism, toxic chemical degradation, bile acid synthesis, and glucose metabolism. Liver function homeostasis is essential for the stability of bodily functions and is involved in the complex regulation of the balance between cell proliferation and cell death. Cell proliferation-halting mechanisms, including autophagy and senescence, are implicated in the development of several liver diseases, such as cholestasis, viral hepatitis, nonalcoholic fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Among various cell death mechanisms, autophagy is a highly conserved and self-degradative cellular process that recycles damaged organelles, cellular debris, and proteins. This process also provides the substrate for further metabolism. A defect in the autophagy machinery can lead to premature diseases, accelerated aging, inflammatory state, tumorigenesis, and cellular senescence. Senescence, another cell death type, is an active player in eliminating premalignant cells. At the same time, senescent cells can affect the function of neighboring cells by secreting the senescence-associated secretory phenotype and induce paracrine senescence. Autophagy can promote and delay cellular senescence under different contexts. This review decodes the roles of autophagy and senescence in multiple liver diseases to achieve a better understanding of the regulatory mechanisms and implications of autophagy and senescence in various liver diseases.
Topics: Humans; Aging; Cellular Senescence; Non-alcoholic Fatty Liver Disease; Autophagy
PubMed: 38069199
DOI: 10.3390/ijms242316880 -
Autophagy Aug 2021Different types of autophagy co-exist in all mammalian cells, however, the specific contribution of each of these autophagic pathways to the maintenance of cellular... (Review)
Review
Different types of autophagy co-exist in all mammalian cells, however, the specific contribution of each of these autophagic pathways to the maintenance of cellular proteostasis and cellular function remains unknown. In this work, we have investigated the consequences of failure of chaperone-mediated autophagy (CMA) in neurons and compared the impact, on the neuronal proteome, of CMA loss to that of macroautophagy loss. We found that these autophagic pathways are non-redundant and that CMA is the main one responsible for maintenance of the metastable proteome (the one at risk of aggregation). We demonstrate that loss of CMA, as the one that occurs in aging, has a synergistic effect with the proteotoxicity associated with neurodegenerative conditions such as Alzheimer disease (AD) and, conversely, that, pharmacological enhancement of CMA is effective in improving both behavior and pathology in two different AD mouse models.
Topics: Aging; Animals; Autophagy; Chaperone-Mediated Autophagy; Humans; Lysosomes; Neurons; Proteostasis
PubMed: 34110247
DOI: 10.1080/15548627.2021.1935007 -
Animal Models and Experimental Medicine Feb 2023Autophagy is one of the degradation pathways to remove proteins or damaged organelles in cells that plays an important role in neuroprotection. Different stages of... (Review)
Review
Autophagy is one of the degradation pathways to remove proteins or damaged organelles in cells that plays an important role in neuroprotection. Different stages of autophagy are regulated by autophagy-related genes, and many molecules such as transcription factor EB (TFEB) are involved. The complete autophagy process plays an important role in maintaining the dynamic balance of autophagy and is crucial to the homeostasis of intracellular substance and energy metabolism. Autophagy balance is disrupted in neurodegenerative diseases, accounting for a variety of degeneration disorders. These impairments can be alleviated or treated by the regulation of autophagy through molecules such as TFEB.
Topics: Humans; Neurodegenerative Diseases; Lysosomes; Autophagy; Organelles; Homeostasis
PubMed: 35730702
DOI: 10.1002/ame2.12229 -
Molecular Medicine (Cambridge, Mass.) Oct 2023Autophagy is an explicit cellular process to deliver dissimilar cytoplasmic misfolded proteins, lipids and damaged organelles to the lysosomes for degradation and... (Review)
Review
Autophagy is an explicit cellular process to deliver dissimilar cytoplasmic misfolded proteins, lipids and damaged organelles to the lysosomes for degradation and elimination. The mechanistic target of rapamycin (mTOR) is the main negative regulator of autophagy. The mTOR pathway is involved in regulating neurogenesis, synaptic plasticity, neuronal development and excitability. Exaggerated mTOR activity is associated with the development of temporal lobe epilepsy, genetic and acquired epilepsy, and experimental epilepsy. In particular, mTOR complex 1 (mTORC1) is mainly involved in epileptogenesis. The investigation of autophagy's involvement in epilepsy has recently been conducted, focusing on the critical role of rapamycin, an autophagy inducer, in reducing the severity of induced seizures in animal model studies. The induction of autophagy could be an innovative therapeutic strategy in managing epilepsy. Despite the protective role of autophagy against epileptogenesis and epilepsy, its role in status epilepticus (SE) is perplexing and might be beneficial or detrimental. Therefore, the present review aims to revise the possible role of autophagy in epilepsy.
Topics: Animals; Epilepsy; Signal Transduction; TOR Serine-Threonine Kinases; Sirolimus; Autophagy; Disease Models, Animal
PubMed: 37880579
DOI: 10.1186/s10020-023-00742-2 -
Nature Communications Jul 2023Cellular homeostasis is governed by removal of damaged organelles and protein aggregates by selective autophagy mediated by cargo adaptors such as p62/SQSTM1....
Cellular homeostasis is governed by removal of damaged organelles and protein aggregates by selective autophagy mediated by cargo adaptors such as p62/SQSTM1. Autophagosomes can assemble in specialized cup-shaped regions of the endoplasmic reticulum (ER) known as omegasomes, which are characterized by the presence of the ER protein DFCP1/ZFYVE1. The function of DFCP1 is unknown, as are the mechanisms of omegasome formation and constriction. Here, we demonstrate that DFCP1 is an ATPase that is activated by membrane binding and dimerizes in an ATP-dependent fashion. Whereas depletion of DFCP1 has a minor effect on bulk autophagic flux, DFCP1 is required to maintain the autophagic flux of p62 under both fed and starved conditions, and this is dependent on its ability to bind and hydrolyse ATP. While DFCP1 mutants defective in ATP binding or hydrolysis localize to forming omegasomes, these omegasomes fail to constrict properly in a size-dependent manner. Consequently, the release of nascent autophagosomes from large omegasomes is markedly delayed. While knockout of DFCP1 does not affect bulk autophagy, it inhibits selective autophagy, including aggrephagy, mitophagy and micronucleophagy. We conclude that DFCP1 mediates ATPase-driven constriction of large omegasomes to release autophagosomes for selective autophagy.
Topics: Macroautophagy; Autophagy; Endoplasmic Reticulum; Adenosine Triphosphatases; Adenosine Triphosphate
PubMed: 37422481
DOI: 10.1038/s41467-023-39641-9 -
Biomedicine & Pharmacotherapy =... Sep 2023With global population aging, age-related diseases, especially sarcopenia, have attracted much attention in recent years. Characterized by low muscle strength, low... (Review)
Review
With global population aging, age-related diseases, especially sarcopenia, have attracted much attention in recent years. Characterized by low muscle strength, low muscle quantity or quality and low physical performance, sarcopenia is one of the major factors associated with an increased risk of falls and disability. Much effort has been made to understand the cellular biological and physiological mechanisms underlying sarcopenia. Autophagy is an important cellular self-protection mechanism that relies on lysosomes to degrade misfolded proteins and damaged organelles. Research designed to obtain new insight into human diseases from the autophagic aspect has been carried out and has made new progress, which encourages relevant studies on the relationship between autophagy and sarcopenia. Autophagy plays a protective role in sarcopenia by modulating the regenerative capability of satellite cells, relieving oxidative stress and suppressing the inflammatory response. This review aims to reveal the specific interaction between sarcopenia and autophagy and explore possible therapies in hopes of encouraging more specific research in need and unlocking novel promising therapies to ameliorate sarcopenia.
Topics: Humans; Sarcopenia; Muscle, Skeletal; Aging; Autophagy; Oxidative Stress
PubMed: 37473679
DOI: 10.1016/j.biopha.2023.115147 -
Viruses May 2021Selective autophagy has emerged as a key mechanism of quality and quantity control responsible for the autophagic degradation of specific subcellular organelles and... (Review)
Review
Selective autophagy has emerged as a key mechanism of quality and quantity control responsible for the autophagic degradation of specific subcellular organelles and materials. In addition, a specific type of selective autophagy (xenophagy) is also activated as a line of defense against invading intracellular pathogens, such as viruses. However, viruses have evolved strategies to counteract the host's antiviral defense and even to activate some proviral types of selective autophagy, such as mitophagy, for their successful infection and replication. This review discusses the current knowledge on the regulation of selective autophagy by human herpesviruses.
Topics: Autophagy; Gene Expression Regulation; Herpesviridae; Host-Pathogen Interactions; Humans; Macroautophagy; Mitophagy
PubMed: 34062931
DOI: 10.3390/v13050820 -
Nature Communications Jan 2024Lipid droplets (LDs) are dynamic lipid storage organelles that can be degraded by autophagy machinery to release neutral lipids, a process called lipophagy. However,...
Lipid droplets (LDs) are dynamic lipid storage organelles that can be degraded by autophagy machinery to release neutral lipids, a process called lipophagy. However, specific receptors and regulation mechanisms for lipophagy remain largely unknown. Here, we identify that ATG14, the core unit of the PI3KC3-C1 complex, also targets LD and acts as an autophagic receptor that facilitates LD degradation. A negative regulator, Syntaxin18 (STX18) binds ATG14, disrupting the ATG14-ATG8 family members interactions and subverting the PI3KC3-C1 complex formation. Knockdown of STX18 activates lipophagy dependent on ATG14 not only as the core unit of PI3KC3-C1 complex but also as the autophagic receptor, resulting in the degradation of LD-associated anti-viral protein Viperin. Furthermore, coronavirus M protein binds STX18 and subverts the STX18-ATG14 interaction to induce lipophagy and degrade Viperin, facilitating virus production. Altogether, our data provide a previously undescribed mechanism for additional roles of ATG14 in lipid metabolism and virus production.
Topics: Lipid Droplets; Lipid Metabolism; Proteins; Autophagy
PubMed: 38245527
DOI: 10.1038/s41467-024-44978-w