scholarly journals Reticulophagy and Ribophagy: Regulated Degradation of Protein Production Factories

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Eduardo Cebollero ◽  
Fulvio Reggiori ◽  
Claudine Kraft
Keyword(s):  
Protein Production ◽  
Membrane Vesicles ◽  
Protein Aggregates ◽  
Nutrient Deprivation ◽  
Adaptation To Stress ◽  
Transport Pathway ◽  
Double Membrane ◽  
Selective Elimination ◽  
Long Time ◽  
Specific Degradation

During autophagy, cytosol, protein aggregates, and organelles are sequestered into double-membrane vesicles called autophagosomes and delivered to the lysosome/vacuole for breakdown and recycling of their basic components. In all eukaryotes this pathway is important for adaptation to stress conditions such as nutrient deprivation, as well as to regulate intracellular homeostasis by adjusting organelle number and clearing damaged structures. For a long time, starvation-induced autophagy has been viewed as a nonselective transport pathway; however, recent studies have revealed that autophagy is able to selectively engulf specific structures, ranging from proteins to entire organelles. In this paper, we discuss recent findings on the mechanisms and physiological implications of two selective types of autophagy: ribophagy, the specific degradation of ribosomes, and reticulophagy, the selective elimination of portions of the ER.

scholarly journals Autophagy: More Than a Nonselective Pathway

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
Fulvio Reggiori ◽  
Masaaki Komatsu ◽  
Kim Finley ◽  
Anne Simonsen
Keyword(s):  
Membrane Vesicles ◽  
Protein Aggregates ◽  
Catabolic Pathway ◽  
Transport Pathway ◽  
Double Membrane ◽  
Long Time ◽  
Specific Receptors ◽  
Aberrant Protein ◽  
The Impact

Autophagy is a catabolic pathway conserved among eukaryotes that allows cells to rapidly eliminate large unwanted structures such as aberrant protein aggregates, superfluous or damaged organelles, and invading pathogens. The hallmark of this transport pathway is the sequestration of the cargoes that have to be degraded in the lysosomes by double-membrane vesicles called autophagosomes. The key actors mediating the biogenesis of these carriers are the autophagy-related genes (ATGs). For a long time, it was assumed that autophagy is a bulk process. Recent studies, however, have highlighted the capacity of this pathway to exclusively eliminate specific structures and thus better fulfil the catabolic necessities of the cell. We are just starting to unveil the regulation and mechanism of these selective types of autophagy, but what it is already clearly emerging is that structures targeted to destruction are accurately enwrapped by autophagosomes through the action of specific receptors and adaptors. In this paper, we will briefly discuss the impact that the selective types of autophagy have had on our understanding of autophagy.

scholarly journals The Interplay of Reovirus with Autophagy

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Hung-Chuan Chiu ◽  
Sarah Richart ◽  
Fong-Yuan Lin ◽  
Wei-Li Hsu ◽  
Hung-Jen Liu
Keyword(s):  
Infectious Diseases ◽  
Membrane Vesicles ◽  
Protein Aggregates ◽  
Degradation Pathway ◽  
Cytoplasmic Protein ◽  
Cellular Homeostasis ◽  
Double Membrane ◽  
Protein Substrates ◽  
Reovirus Infection ◽  
Physiological Processes

Autophagy participates in multiple fundamental physiological processes, including survival, differentiation, development, and cellular homeostasis. It eliminates cytoplasmic protein aggregates and damaged organelles by triggering a series of events: sequestering the protein substrates into double-membrane vesicles, fusing the vesicles with lysosomes, and then degrading the autophagic contents. This degradation pathway is also involved in various disorders, for instance, cancers and infectious diseases. This paper provides an overview of modulation of autophagy in the course of reovirus infection and also the interplay of autophagy and reovirus.

scholarly journals Sphingomyelin Is Essential for the Structure and Function of the Double-Membrane Vesicles in Hepatitis C Virus RNA Replication Factories

2020 ◽  
Vol 94 (23) ◽  
Author(s):  
Hossam Gewaid ◽  
Haruyo Aoyagi ◽  
Minetaro Arita ◽  
Koichi Watashi ◽  
Ryosuke Suzuki ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Protein Production ◽  
Rna Viruses ◽  
Ectopic Expression ◽  
Membrane Vesicles ◽  
Hcv Rna ◽  
Independent System ◽  
Double Membrane ◽  
Transfer Protein

ABSTRACT Some plus-stranded RNA viruses generate double-membrane vesicles (DMVs), one type of the membrane replication factories, as replication sites. Little is known about the lipid components involved in the biogenesis of these vesicles. Sphingomyelin (SM) is required for hepatitis C virus (HCV) replication, but the mechanism of SM involvement remains poorly understood. SM biosynthesis starts in the endoplasmic reticulum (ER) and gives rise to ceramide, which is transported from the ER to the Golgi by the action of ceramide transfer protein (CERT), where it can be converted to SM. In this study, inhibition of SM biosynthesis, either by using small-molecule inhibitors or by knockout (KO) of CERT, suppressed HCV replication in a genotype-independent manner. This reduction in HCV replication was rescued by exogenous SM or ectopic expression of the CERT protein, but not by ectopic expression of nonfunctional CERT mutants. Observing low numbers of DMVs in stable replicon cells treated with a SM biosynthesis inhibitor or in CERT-KO cells transfected with either HCV replicon or with constructs that drive HCV protein production in a replication-independent system indicated the significant importance of SM to DMVs. The degradation of SM of the in vitro-isolated DMVs affected their morphology and increased the vulnerability of HCV RNA and proteins to RNase and protease treatment, respectively. Poliovirus, known to induce DMVs, showed decreased replication in CERT-KO cells, while dengue virus, known to induce invaginated vesicles, did not. In conclusion, these findings indicated that SM is an essential constituent of DMVs generated by some plus-stranded RNA viruses. IMPORTANCE Previous reports assumed that sphingomyelin (SM) is essential for HCV replication, but the mechanism was unclear. In this study, we showed for the first time that SM and ceramide transfer protein (CERT), which is in the SM biosynthesis pathway, are essential for the biosynthesis of double-membrane vesicles (DMVs), the sites of viral replication. Low numbers of DMVs were observed in CERT-KO cells transfected with replicon RNA or with constructs that drive HCV protein production in a replication-independent system. HCV replication was rescued by ectopic expression of the CERT protein, but not by CERT mutants, that abolishes the binding of CERT to vesicle-associated membrane protein-associated protein (VAP) or phosphatidylinositol 4-phosphate (PI4P), indicating new roles for VAP and PI4P in HCV replication. The biosynthesis of DMVs has great importance to replication by a variety of plus-stranded RNA viruses. Understanding of this process is expected to facilitate the development of diagnosis and antivirus.

scholarly journals Bacterial outer membrane vesicles engineered with lipidated antigens as a platform for Staphylococcus aureus vaccine

2019 ◽  
Vol 116 (43) ◽  
pp. 21780-21788 ◽  
Author(s):  
Carmela Irene ◽  
Laura Fantappiè ◽  
Elena Caproni ◽  
Francesca Zerbini ◽  
Andrea Anesi ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Outer Membrane ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Vaccine Platform ◽  
Transport Pathway ◽  
Protective Antigens ◽  
Tlr4 Agonist ◽  
Engineering Strategy ◽  
Bacterial Outer Membrane

Bacterial outer membrane vesicles (OMVs) represent an interesting vaccine platform for their built-in adjuvanticity and simplicity of production process. Moreover, OMVs can be decorated with foreign antigens using different synthetic biology approaches. However, the optimal OMV engineering strategy, which should guarantee the OMV compartmentalization of most heterologous antigens in quantities high enough to elicit protective immune responses, remains to be validated. In this work we exploited the lipoprotein transport pathway to engineer OMVs with foreign proteins. Using 5 Staphylococcus aureus protective antigens expressed in Escherichia coli as fusions to a lipoprotein leader sequence, we demonstrated that all 5 antigens accumulated in the vesicular compartment at a concentration ranging from 5 to 20% of total OMV proteins, suggesting that antigen lipidation could be a universal approach for OMV manipulation. Engineered OMVs elicited high, saturating antigen-specific antibody titers when administered to mice in quantities as low as 0.2 μg/dose. Moreover, the expression of lipidated antigens in E. coli BL21(DE3)ΔompAΔmsbBΔpagP was shown to affect the lipopolysaccharide structure, with the result that the TLR4 agonist activity of OMVs was markedly reduced. These results, together with the potent protective activity of engineered OMVs observed in mice challenged with S. aureus Newman strain, makes the 5-combo-OMVs a promising vaccine candidate to be tested in clinics.

scholarly journals Myocardial Damage by SARS-CoV-2: Emerging Mechanisms and Therapies

Viruses ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1880
Author(s):  
Huyen Tran Ho ◽  
Stefan Peischard ◽  
Nathalie Strutz-Seebohm ◽  
Karin Klingel ◽  
Guiscard Seebohm
Keyword(s):  
Immune Response ◽  
Cell Death ◽  
Energy Metabolism ◽  
Programmed Cell Death ◽  
Viral Replication ◽  
Ion Homeostasis ◽  
Membrane Vesicles ◽  
Cardiac Cells ◽  
The Body ◽  
Double Membrane

Evidence is emerging that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect various organs of the body, including cardiomyocytes and cardiac endothelial cells in the heart. This review focuses on the effects of SARS-CoV-2 in the heart after direct infection that can lead to myocarditis and an outline of potential treatment options. The main points are: (1) Viral entry: SARS-CoV-2 uses specific receptors and proteases for docking and priming in cardiac cells. Thus, different receptors or protease inhibitors might be effective in SARS-CoV-2-infected cardiac cells. (2) Viral replication: SARS-CoV-2 uses RNA-dependent RNA polymerase for replication. Drugs acting against ssRNA(+) viral replication for cardiac cells can be effective. (3) Autophagy and double-membrane vesicles: SARS-CoV-2 manipulates autophagy to inhibit viral clearance and promote SARS-CoV-2 replication by creating double-membrane vesicles as replication sites. (4) Immune response: Host immune response is manipulated to evade host cell attacks against SARS-CoV-2 and increased inflammation by dysregulating immune cells. Efficiency of immunosuppressive therapy must be elucidated. (5) Programmed cell death: SARS-CoV-2 inhibits programmed cell death in early stages and induces apoptosis, necroptosis, and pyroptosis in later stages. (6) Energy metabolism: SARS-CoV-2 infection leads to disturbed energy metabolism that in turn leads to a decrease in ATP production and ROS production. (7) Viroporins: SARS-CoV-2 creates viroporins that lead to an imbalance of ion homeostasis. This causes apoptosis, altered action potential, and arrhythmia.

scholarly journals The Origin, Dynamic Morphology, and PI4P-Independent Formation of Encephalomyocarditis Virus Replication Organelles

mBio ◽  
2018 ◽  
Vol 9 (2) ◽  
pp. e00420-18 ◽  
Author(s):  
C. E. Melia ◽  
H. M. van der Schaar ◽  
A. W. M. de Jong ◽  
H. R. Lyoo ◽  
E. J. Snijder ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Rna Synthesis ◽  
Electron Tomography ◽  
Membrane Vesicles ◽  
Encephalomyocarditis Virus ◽  
Escape Mutant ◽  
Membrane Structures ◽  
Double Membrane ◽  
Single Membrane ◽  
Phosphatidylinositol 4

ABSTRACTPicornaviruses induce dramatic rearrangements of endomembranes in the cells that they infect to produce dedicated platforms for viral replication. These structures, termed replication organelles (ROs), have been well characterized for theEnterovirusgenus of thePicornaviridae. However, it is unknown whether the diverse RO morphologies associated with enterovirus infection are conserved among other picornaviruses. Here, we use serial electron tomography at different stages of infection to assess the three-dimensional architecture of ROs induced by encephalomyocarditis virus (EMCV), a member of theCardiovirusgenus of the family of picornaviruses that is distantly related. Ultrastructural analyses revealed connections between early single-membrane EMCV ROs and the endoplasmic reticulum (ER), establishing the ER as a likely donor organelle for their formation. These early single-membrane ROs appear to transform into double-membrane vesicles (DMVs) as infection progresses. Both single- and double-membrane structures were found to support viral RNA synthesis, and progeny viruses accumulated in close proximity, suggesting a spatial association between RNA synthesis and virus assembly. Further, we explored the role of phosphatidylinositol 4-phosphate (PI4P), a critical host factor for both enterovirus and cardiovirus replication that has been recently found to expedite enterovirus RO formation rather than being strictly required. By exploiting an EMCV escape mutant, we found that low-PI4P conditions could also be overcome for the formation of cardiovirus ROs. Collectively, our data show that despite differences in the membrane source, there are striking similarities in the biogenesis, morphology, and transformation of cardiovirus and enterovirus ROs, which may well extend to other picornaviruses.IMPORTANCELike all positive-sense RNA viruses, picornaviruses induce the rearrangement of host cell membranes to form unique structures, or replication organelles (ROs), that support viral RNA synthesis. Here, we investigate the architecture and biogenesis of cardiovirus ROs and compare them with those induced by enteroviruses, members of the well-characterized picornavirus genusEnterovirus. The origins and dynamic morphologies of cardiovirus ROs are revealed using electron tomography, which points to the endoplasmic reticulum as the donor organelle usurped to produce single-membrane tubules and vesicles that transform into double-membrane vesicles. We show that PI4P, a critical lipid for cardiovirus and enterovirus replication, is not strictly required for the formation of cardiovirus ROs, as functional ROs with typical morphologies are formed under phosphatidylinositol 4-kinase type III alpha (PI4KA) inhibition in cells infected with an escape mutant. Our data show that the transformation from single-membrane structures to double-membrane vesicles is a conserved feature of cardiovirus and enterovirus infections that likely extends to other picornavirus genera.

scholarly journals Ultrastructural Evidence for Direct Renal Infection with SARS-CoV-2

2020 ◽  
Vol 31 (8) ◽  
pp. 1683-1687 ◽  
Author(s):  
Evan A. Farkash ◽  
Allecia M. Wilson ◽  
Jeffrey M. Jentzen
Keyword(s):  
Renal Failure ◽  
Light Microscopy ◽  
Virus Assembly ◽  
Light And Electron Microscopy ◽  
Membrane Vesicles ◽  
Renal Tissue ◽  
Double Membrane ◽  
Renal Tubular Epithelium ◽  
Renal Tubular ◽  
Renal Infection

BackgroundA significant fraction of patients with coronavirus disease 2019 (COVID-19) display abnormalities in renal function. Retrospective studies of patients hospitalized with COVID-19 in Wuhan, China, report an incidence of 3%–7% progressing to ARF, a marker of poor prognosis. The cause of the renal failure in COVID-19 is unknown, but one hypothesized mechanism is direct renal infection by the causative virus, SARS-CoV-2.MethodsWe performed an autopsy on a single patient who died of COVID-19 after open repair of an aortic dissection, complicated by hypoxic respiratory failure and oliguric renal failure. We used light and electron microscopy to examine renal tissue for evidence of SARS-CoV-2 within renal cells.ResultsLight microscopy of proximal tubules showed geographic isometric vacuolization, corresponding to a focus of tubules with abundant intracellular viral arrays. Individual viruses averaged 76 µm in diameter and had an envelope studded with crown-like, electron-dense spikes. Vacuoles contained double-membrane vesicles suggestive of partially assembled virus.ConclusionsThe presence of viral particles in the renal tubular epithelium that were morphologically identical to SARS-CoV-2, and with viral arrays and other features of virus assembly, provide evidence of a productive direct infection of the kidney by SARS-CoV-2. This finding offers confirmatory evidence that direct renal infection occurs in the setting of AKI in COVID-19. However, the frequency and clinical significance of direct infection in COVID-19 is unclear. Tubular isometric vacuolization observed with light microscopy, which correlates with double-membrane vesicles containing vacuoles observed with electronic microscopy, may be a useful histologic marker for active SARS-CoV-2 infection in kidney biopsy or autopsy specimens.

scholarly journals A molecular pore spans the double membrane of the coronavirus replication organelle

Science ◽  
2020 ◽  
Vol 369 (6509) ◽  
pp. 1395-1398 ◽  
Author(s):  
Georg Wolff ◽  
Ronald W. A. L. Limpens ◽  
Jessika C. Zevenhoven-Dobbe ◽  
Ulrike Laugks ◽  
Shawn Zheng ◽  
...  
Keyword(s):  
Drug Target ◽  
Rna Synthesis ◽  
Transmembrane Protein ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Genome Replication ◽  
Messenger Rnas ◽  
Double Membrane ◽  
The Core ◽  
Cryo Electron Microscopy

Coronavirus genome replication is associated with virus-induced cytosolic double-membrane vesicles, which may provide a tailored microenvironment for viral RNA synthesis in the infected cell. However, it is unclear how newly synthesized genomes and messenger RNAs can travel from these sealed replication compartments to the cytosol to ensure their translation and the assembly of progeny virions. In this study, we used cellular cryo–electron microscopy to visualize a molecular pore complex that spans both membranes of the double-membrane vesicle and would allow export of RNA to the cytosol. A hexameric assembly of a large viral transmembrane protein was found to form the core of the crown-shaped complex. This coronavirus-specific structure likely plays a key role in coronavirus replication and thus constitutes a potential drug target.

scholarly journals Virus-induced double-membrane vesicles

2014 ◽  
Vol 17 (1) ◽  
pp. 45-50 ◽  
Author(s):  
Emmanuelle Blanchard ◽  
Philippe Roingeard
Keyword(s):  
Membrane Vesicles ◽  
Double Membrane

Bioinspired nanocarriers for an effective chemotherapy of hepatocellular carcinoma

2018 ◽  
Vol 33 (1) ◽  
pp. 72-81 ◽  
Author(s):  
Lei Xu ◽  
Shuo Wu ◽  
Xiaoqiu Zhou
Keyword(s):  
Hepg2 Cells ◽  
Blood Circulation ◽  
Antitumor Effect ◽  
Membrane Vesicles ◽  
Controlled Drug Release ◽  
Coated Nanoparticles ◽  
Rbc Membrane ◽  
Long Time

Drug-loaded nanoparticles have been widely researched in the antitumor. However, some of them are unsatisfactory in the long blood circulation and controlled drug release. Red blood cell (RBC) membrane vesicles (RV)-coated nanoparticles have gained more and more attention in drug delivery for their many unique advantages, such as excellent stability, long blood circulation, and reduced the macrophage cells uptake. Herein, by utilizing the advantages of RV, we fabricated RV-coated poly(lactide- co-glycolide) (PLGA)–docetaxel (RV/PLGA/DTX) nanoparticles to enhance the antitumor efficiency in vivo. The RV/PLGA/DTX showed spherical morphology with particle size of about 100 nm and zeta potential at −12.63 mV, which could maintain stability for a long time. The RV/PLGA/DTX significantly enhanced cellular uptake of DTX compared to PLGA/DTX in HepG2 cells. Moreover, RV/PLGA/DTX showed the strongest antitumor effect in vitro. Prolonged blood circulation and enhanced DTX accumulation at the tumor site through enhanced permeability and retention (EPR) effect were achieved by RV/PLGA/DTX, which eventually obtained satisfactory antitumor effect and depressed system toxicity on mice bearing HepG2 xenografts mouse models when compared with free DTX. The hematoxylin and eosin (H&E) and immunofluorescence assays further proved the advantages of RV/PLGA/DTX in vivo antitumor. These RV-coated nanoparticles provide a mimetic therapy, completely inhibited the growth of the HepG2 cells, and with simple compositions, suggesting it to be an ideal strategy for improving the antitumor effect of drug-loaded nanoparticles.

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