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Neuron Feb 2022Neurodegenerative disorders are characterized by a collapse in proteostasis, as shown by the accumulation of insoluble protein aggregates in the brain. Proteostasis...
Neurodegenerative disorders are characterized by a collapse in proteostasis, as shown by the accumulation of insoluble protein aggregates in the brain. Proteostasis involves a balance of protein synthesis, folding, trafficking, and degradation, but how aggregates perturb these pathways is unknown. Using Parkinson's disease (PD) patient midbrain cultures, we find that aggregated α-synuclein induces endoplasmic reticulum (ER) fragmentation and compromises ER protein folding capacity, leading to misfolding and aggregation of immature lysosomal β-glucocerebrosidase. Despite this, PD neurons fail to initiate the unfolded protein response, indicating perturbations in sensing or transducing protein misfolding signals in the ER. Small molecule enhancement of ER proteostasis machinery promotes β-glucocerebrosidase solubility, while simultaneous enhancement of trafficking improves ER morphology, lysosomal function, and reduces α-synuclein. Our studies suggest that aggregated α-synuclein perturbs the ability of neurons to respond to misfolded proteins in the ER, and that synergistic enhancement of multiple proteostasis branches may provide therapeutic benefit in PD.
Topics: Endoplasmic Reticulum; Humans; Mesencephalon; Neurons; Parkinson Disease; Protein Aggregation, Pathological; Protein Folding; Protein Transport; Proteostasis; alpha-Synuclein
PubMed: 34793693
DOI: 10.1016/j.neuron.2021.10.032 -
The Journal of Physical Chemistry. B Mar 2022Lipid droplets (LDs) are intracellular organelles whose primary function is energy storage. Known to emerge from the endoplasmic reticulum (ER) bilayer, LDs have a... (Review)
Review
Lipid droplets (LDs) are intracellular organelles whose primary function is energy storage. Known to emerge from the endoplasmic reticulum (ER) bilayer, LDs have a unique structure with a core consisting of neutral lipids, triacylglycerol (TG) or sterol esters (SE), surrounded by a phospholipid (PL) monolayer and decorated by proteins that come and go throughout their complex lifecycle. In this Feature Article, we review recent developments in computational studies of LDs, a rapidly growing area of research. We highlight how molecular dynamics (MD) simulations have provided valuable molecular-level insight into LD targeting and LD biogenesis. Additionally, we review the physical properties of TG from different force fields compared with experimental data. Possible future directions and challenges are discussed.
Topics: Endoplasmic Reticulum; Lipid Droplets; Lipid Metabolism; Molecular Dynamics Simulation; Phospholipids; Triglycerides
PubMed: 35263109
DOI: 10.1021/acs.jpcb.2c00292 -
Cell Death and Differentiation Mar 2020Autophagy regulates the degradation of unnecessary or dysfunctional cellular components. This catabolic process requires the formation of a double-membrane vesicle, the... (Review)
Review
Autophagy regulates the degradation of unnecessary or dysfunctional cellular components. This catabolic process requires the formation of a double-membrane vesicle, the autophagosome, that engulfs the cytosolic material and delivers it to the lysosome. Substrate specificity is achieved by autophagy receptors, which are characterized by the presence of at least one LC3-interaction region (LIR) or GABARAP-interaction motif (GIM). Only recently, several receptors that mediate the specific degradation of endoplasmic reticulum (ER) components via autophagy have been identified (the process known as ER-phagy or reticulophagy). Here, we give an update on the current knowledge about the role of ER-phagy receptors in health and disease.
Topics: Animals; Autophagy; Disease; Endoplasmic Reticulum; Homeostasis; Humans
PubMed: 31659280
DOI: 10.1038/s41418-019-0444-0 -
Nature Cell Biology Dec 2022The endoplasmic reticulum (ER) coordinates mRNA translation and processing of secreted and endomembrane proteins. ER-associated degradation (ERAD) prevents the...
The endoplasmic reticulum (ER) coordinates mRNA translation and processing of secreted and endomembrane proteins. ER-associated degradation (ERAD) prevents the accumulation of misfolded proteins in the ER, but the physiological regulation of this process remains poorly characterized. Here, in a genetic screen using an ERAD model substrate in Caenorhabditis elegans, we identified an anti-viral RNA interference pathway, referred to as ER-associated RNA silencing (ERAS), which acts together with ERAD to preserve ER homeostasis and function. Induced by ER stress, ERAS is mediated by the Argonaute protein RDE-1/AGO2, is conserved in mammals and promotes ER-associated RNA turnover. ERAS and ERAD are complementary, as simultaneous inactivation of both quality-control pathways leads to increased ER stress, reduced protein quality control and impaired intestinal integrity. Collectively, our findings indicate that ER homeostasis and organismal health are protected by synergistic functions of ERAS and ERAD.
Topics: RNA Interference; Endoplasmic Reticulum
PubMed: 36471127
DOI: 10.1038/s41556-022-01025-4 -
Current Opinion in Structural Biology Jun 2023Cells store lipids as a reservoir of metabolic energy and membrane component precursors in organelles called lipid droplets (LDs). LD formation occurs in the endoplasmic... (Review)
Review
Cells store lipids as a reservoir of metabolic energy and membrane component precursors in organelles called lipid droplets (LDs). LD formation occurs in the endoplasmic reticulum (ER) at LD assembly complexes (LDAC), consisting of an oligomeric core of seipin and accessory proteins. LDACs determine the sites of LD formation and are required for this process to occur normally. Seipin oligomers form a cage-like structure in the membrane that may serve to facilitate the phase transition of neutral lipids in the membrane to form an oil droplet within the LDAC. Modeling suggests that, as the LD grows, seipin anchors it to the ER bilayer and conformational shifts of seipin transmembrane segments open the LDAC dome toward the cytoplasm, enabling the emerging LD to egress from the ER.
Topics: Lipid Droplets; Proteins; Endoplasmic Reticulum; Lipids; Lipid Metabolism
PubMed: 37150040
DOI: 10.1016/j.sbi.2023.102606 -
Frontiers in Immunology 2023Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), the prime causes of morbidity and mortality in critically ill patients, are usually treated by... (Review)
Review
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), the prime causes of morbidity and mortality in critically ill patients, are usually treated by general supportive treatments. Endoplasmic reticulum autophagy (ER-phagy) maintains cellular homeostasis by degrading damaged endoplasmic reticulum (ER) fragments and misfolded proteins. ER-phagy is crucial for maintaining ER homeostasis and improving the internal environment. ER-phagy has a particular role in some aspects, such as immunity, inflammation, cell death, pathogen infection, and collagen quality. In this review, we summarized the definition, epidemiology, and pathophysiology of ALI/ARDS and described the regulatory mechanisms and functions of ER-phagy as well as discussed the potential role of ER-phagy in ALI/ARDS from the perspectives of immunity, inflammation, apoptosis, pathogen infection, and fibrosis to provide a novel and effective target for improving the prognosis of ALI/ARDS.
Topics: Humans; Endoplasmic Reticulum Stress; Autophagy; Endoplasmic Reticulum; Inflammation; Acute Lung Injury
PubMed: 37266445
DOI: 10.3389/fimmu.2023.1152336 -
Journal of Assisted Reproduction and... Jun 2023The storage and release of calcium ions (Ca2 +) in oocyte maturation and fertilization are particularly noteworthy features of the endoplasmic reticulum (ER). The ER... (Review)
Review
The storage and release of calcium ions (Ca2 +) in oocyte maturation and fertilization are particularly noteworthy features of the endoplasmic reticulum (ER). The ER is the largest organelle in the cell composed of rough ER, smooth ER, and nuclear envelope, and is the main site of protein synthesis, transport and folding, and lipid and steroid synthesis. An appropriate calcium signaling response can initiate oocyte development and embryogenesis, and the ER is the central link that initiates calcium signaling. The transition from immature oocytes to zygotes also requires many coordinated organelle reorganizations and changes. Therefore, the purpose of this review is to generalize information on the function, structure, interaction with other organelles, and spatiotemporal localization of the ER in mammalian oocytes. Mechanisms related to maintaining ER homeostasis have been extensively studied in recent years. Resolving ER stress through the unfolded protein response (UPR) is one of them. We combined the clinical problems caused by the ER in in vitro maturation (IVM), and the mechanisms of ER have been identified by single-cell RNA-seq. This article systematically reviews the functions of ER and provides a reference for assisted reproductive technology (ART) research.
Topics: Animals; Oocytes; Unfolded Protein Response; Endoplasmic Reticulum Stress; Oogenesis; Endoplasmic Reticulum; Mammals
PubMed: 37171741
DOI: 10.1007/s10815-023-02782-3 -
Biochimica Et Biophysica Acta.... Jan 2020Lipid droplets (LDs) are ubiquitous organelles that store metabolic energy in the form of neutral lipids (typically triacylglycerols and steryl esters). Beyond being... (Review)
Review
Lipid droplets (LDs) are ubiquitous organelles that store metabolic energy in the form of neutral lipids (typically triacylglycerols and steryl esters). Beyond being inert energy storage compartments, LDs are dynamic organelles that participate in numerous essential metabolic functions. Cells generate LDs de novo from distinct sub-regions at the endoplasmic reticulum (ER), but what determines sites of LD formation remains a key unanswered question. Here, we review the factors that determine LD formation at the ER, and discuss how they work together to spatially and temporally coordinate LD biogenesis. These factors include lipid synthesis enzymes, assembly proteins, and membrane structural requirements. LDs also make contact with other organelles, and these inter-organelle contacts contribute to defining sites of LD production. Finally, we highlight emerging non-canonical roles for LDs in maintaining cellular homeostasis during stress.
Topics: Animals; Endoplasmic Reticulum; Fatty Acids; Homeostasis; Humans; Lipid Droplets; Lipid Metabolism
PubMed: 31352131
DOI: 10.1016/j.bbalip.2019.07.008 -
Proceedings of the Japan Academy.... 2020Autophagy is an intracellular degradation system that is present in most eukaryotes. In the process of autophagy, double membrane vesicles called autophagosomes... (Review)
Review
Autophagy is an intracellular degradation system that is present in most eukaryotes. In the process of autophagy, double membrane vesicles called autophagosomes sequester a wide variety of cellular constituents and deliver them to lytic organelles: lysosomes in mammals and vacuoles in yeast and plants. Although autophagy used to be considered a non-selective process in its target sequestration into autophagosomes, recent studies have revealed that autophagosomes can also selectively sequester certain proteins and organelles that have become unnecessary or harmful for the cell. We recently discovered that the endoplasmic reticulum (ER) is degraded by autophagy in a selective manner in the budding yeast Saccharomyces cerevisiae, and identified "receptor proteins" that play pivotal roles in this "ER-phagy" pathway. Moreover, several ER-phagy receptors in mammalian cells have also been reported. This report provides an overview of our current knowledge on ER-phagy and discuss their mechanisms, physiological roles, and possible links to human diseases.
Topics: Animals; Autophagosomes; Autophagy; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Humans; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 31932525
DOI: 10.2183/pjab.96.001 -
Cells Sep 2021As an important form of selective autophagy in cells, ER-phagy (endoplasmic reticulum-selective autophagy), the autophagic degradation of endoplasmic reticulum (ER),... (Review)
Review
As an important form of selective autophagy in cells, ER-phagy (endoplasmic reticulum-selective autophagy), the autophagic degradation of endoplasmic reticulum (ER), degrades ER membranes and proteins to maintain cellular homeostasis. The relationship between ER-phagy and human diseases, including neurodegenerative disorders, cancer, and other metabolic diseases has been unveiled by extensive research in recent years. Starting with the catabolic process of ER-phagy and key mediators in this pathway, this paper reviews the advances in the mechanism of ER-phagy and its diseases relevance. We hope to provide some enlightenment for further study on ER-phagy and the development of novel therapeutic strategies for related diseases.
Topics: Animals; Autophagy; Endoplasmic Reticulum; Endoplasmic Reticulum Stress; Homeostasis; Humans; Intracellular Membranes
PubMed: 34571977
DOI: 10.3390/cells10092328