scholarly journals Reticulon protects the integrity of the ER membrane during ER escape of large macromolecular protein complexes

2020 ◽  
Vol 219 (2) ◽  
Author(s):  
Yu-Jie Chen ◽  
Jeffrey M. Williams ◽  
Peter Arvan ◽  
Billy Tsai
Keyword(s):  
Mechanical Stress ◽  
Protein Complexes ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Lysosomal Degradation ◽  
Macromolecular Complexes ◽  
Luminal Side ◽  
Cellular Aggregate ◽  
Macromolecular Protein ◽  
Er Membrane

Escape of large macromolecular complexes from the endoplasmic reticulum (ER), such as a viral particle or cellular aggregate, likely induces mechanical stress initiated on the luminal side of the ER membrane, which may threaten its integrity. How the ER responds to this threat remains unknown. Here we demonstrate that the cytosolic leaflet ER morphogenic protein reticulon (RTN) protects ER membrane integrity when polyomavirus SV40 escapes the ER to reach the cytosol en route to infection. SV40 coopts an intrinsic RTN function, as we also found that RTN prevents membrane damage during ER escape of a misfolded proinsulin aggregate destined for lysosomal degradation via ER-phagy. Our studies reveal that although ER membrane integrity may be threatened during ER escape of large macromolecular protein complexes, the action of RTN counters this, presumably by deploying its curvature-inducing activity to provide membrane flexibility and stability to limit mechanical stress imposed on the ER membrane.

scholarly journals Circadian Interactomics: How Research Into Protein-Protein Interactions Beyond the Core Clock Has Influenced the Model of Circadian Timekeeping

2021 ◽  
pp. 074873042110146
Author(s):  
Alexander E. Mosier ◽  
Jennifer M. Hurley
Keyword(s):  
Circadian Clock ◽  
Protein Interactions ◽  
Large Scale ◽  
Protein Complexes ◽  
Model Organisms ◽  
Protein Protein Interactions ◽  
Macromolecular Complexes ◽  
The Core ◽  
Circadian Control ◽  
Macromolecular Protein

The circadian clock is the broadly conserved, protein-based, timekeeping mechanism that synchronizes biology to the Earth’s 24-h light-dark cycle. Studies of the mechanisms of circadian timekeeping have placed great focus on the role that individual protein-protein interactions play in the creation of the timekeeping loop. However, research has shown that clock proteins most commonly act as part of large macromolecular protein complexes to facilitate circadian control over physiology. The formation of these complexes has led to the large-scale study of the proteins that comprise these complexes, termed here “circadian interactomics.” Circadian interactomic studies of the macromolecular protein complexes that comprise the circadian clock have uncovered many basic principles of circadian timekeeping as well as mechanisms of circadian control over cellular physiology. In this review, we examine the wealth of knowledge accumulated using circadian interactomics approaches to investigate the macromolecular complexes of the core circadian clock, including insights into the core mechanisms that impart circadian timing and the clock’s regulation of many physiological processes. We examine data acquired from the investigation of the macromolecular complexes centered on both the activating and repressing arm of the circadian clock and from many circadian model organisms.

IMPACT OF SORBITOL- INDUCED OSMOTIC STRESS ON SOME BIOCHEMICAL TRAITS OF POTATO IN VITRO

2020 ◽  
Vol 51 (4) ◽  
pp. 1038-1047
Author(s):  
Mawia & et al.
Keyword(s):  
Ascorbic Acid ◽  
Osmotic Stress ◽  
Cytoplasmic Membrane ◽  
Genotypic Variation ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Culture Collection ◽  
Nutritive Medium ◽  
Starting Point

This study had as principal objective identification of osmotic-tolerant potato genotypes by using "in vitro" tissue culture and sorbitol as a stimulating agent, to induce water stress, which was added to the  culture nutritive medium in different concentration (0,50, 110, 220, 330 and 440 mM).  The starting point was represented by plantlets culture collection, belonging to eleven potato genotypes: Barcelona, Nectar, Alison, Jelly, Malice, Nazca, Toronto, Farida, Fabulla, Colomba and Spunta. Plantlets were multiplied between two internodes to obtain microcuttings (in sterile condition), which were inoculated on medium. Sorbitol-induced osmotic stress caused a significant reduction in the ascorbic acid, while the concentration of proline, H2O2 and solutes leakage increased compared with the control. Increased the proline content prevented lipid peroxidation, which played a pivotal role in the maintenance of membrane integrity under osmotic stress conditions. The extent of the cytoplasmic membrane damage depends on osmotic stress severity and the genotypic variation in the maintenance of membranes stability was highly associated with the ability of producing more amounts of osmoprotectants (proline) and the non-enzymic antioxidant ascorbic acid in response to osmotic stress level. The results showed that the genotypes Jelly, Nectar, Allison, Toronto, and Colomba are classified as highly osmotic stress tolerant genotypes, while the genotypes Nazca and Farida are classified as osmotic stress susceptible ones.

scholarly journals Exosomes induce endolysosomal permeabilization as a gateway by which exosomal tau seeds escape into the cytosol

2021 ◽  
Author(s):  
Juan Carlos Polanco ◽  
Gabriel Rhys Hand ◽  
Adam Briner ◽  
Chuanzhou Li ◽  
Jürgen Götz
Keyword(s):  
Critical Role ◽  
Membrane Integrity ◽  
Lysosomal Degradation ◽  
Escape Route ◽  
Cellular Invasion ◽  
Endosomal Membrane ◽  
Late Endosomes ◽  
Endosomal Membranes ◽  
Endosomal Pathway ◽  
Tau Aggregation

AbstractThe microtubule-associated protein tau has a critical role in Alzheimer’s disease and other tauopathies. A proposed pathomechanism in the progression of tauopathies is the trans-synaptic spreading of tau seeds, with a role for exosomes which are secretory nanovesicles generated by late endosomes. Our previous work demonstrated that brain-derived exosomes isolated from tau transgenic rTg4510 mice encapsulate tau seeds with the ability to induce tau aggregation in recipient cells. We had also shown that exosomes can hijack the endosomal pathway to spread through interconnected neurons. Here, we reveal how tau seeds contained within internalized exosomes exploit mechanisms of lysosomal degradation to escape the endosome and induce tau aggregation in the cytosol of HEK293T-derived ‘tau biosensor cells’. We found that the majority of the exosome-containing endosomes fused with lysosomes to form endolysosomes. Exosomes induced their permeabilization, irrespective of the presence of tau seeds, or whether the exosomal preparations originated from mouse brains or HEK293T cells. We also found that permeabilization is a conserved mechanism, operating in both non-neuronal tau biosensor cells and primary neurons. However, permeabilization of endolysosomes only occurred in a small fraction of cells, which supports the notion that permeabilization occurs by a thresholded mechanism. Interestingly, tau aggregation was only induced in cells that exhibited permeabilization, presenting this as an escape route of exosomal tau seeds into the cytosol. Overexpression of RAB7, which is required for the formation of endolysosomes, strongly increased tau aggregation. Conversely, inhibition of lysosomal function with alkalinizing agents, or by knocking-down RAB7, decreased tau aggregation. Together, we conclude that the enzymatic activities of lysosomes permeabilize exosomal and endosomal membranes, thereby facilitating access of exosomal tau seeds to cytosolic tau to induce its aggregation. Our data underscore the importance of endosomal membrane integrity in mechanisms of cellular invasion by misfolded proteins that are resistant to lysosomal degradation.

scholarly journals Plasma membrane integrity: implications for health and disease

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Dustin A. Ammendolia ◽  
William M. Bement ◽  
John H. Brumell
Keyword(s):  
Plasma Membrane ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Whole Body ◽  
Plasma Membrane Integrity ◽  
Plasma Membrane Damage ◽  
Cellular Environment ◽  
Health And Disease ◽  
Repair Pathways ◽  
The Impact

AbstractPlasma membrane integrity is essential for cellular homeostasis. In vivo, cells experience plasma membrane damage from a multitude of stressors in the extra- and intra-cellular environment. To avoid lethal consequences, cells are equipped with repair pathways to restore membrane integrity. Here, we assess plasma membrane damage and repair from a whole-body perspective. We highlight the role of tissue-specific stressors in health and disease and examine membrane repair pathways across diverse cell types. Furthermore, we outline the impact of genetic and environmental factors on plasma membrane integrity and how these contribute to disease pathogenesis in different tissues.

scholarly journals Fluorescent Chitosan Nanogels Developed for Targeting Endothelial Cells of Axillary Lymph Nodes

2020 ◽  
Vol 4 (1) ◽  
pp. 12
Author(s):  
Miruna-Silvia Stan ◽  
Ionela Cristina Nica ◽  
Juliette Moreau ◽  
Maïté Callewaert ◽  
Cyril Cadiou ◽  
...  
Keyword(s):  
Membrane Damage ◽  
Membrane Integrity ◽  
Simian Virus 40 ◽  
Cancer Diagnostics ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Microvascular Endothelial Cell ◽  
Axillary Lymph Nodes ◽  
Cell Periphery ◽  
Axillary Lymph

Nanogels are a novel class of three-dimensional cross-linked polymers able to retain high amounts of water in their network structure, with large potential applications in nanomedicine. In our study, the polymer matrix selected was chitosan, as this polysaccharide biopolymer composed of N-acetylglucosamine and glucosamine residues exhibits great biocompatibility and low toxicity. The preparation was performed by ionic gelation in the presence of hyaluronic acid and sodium tripolyphosphate, with rhodamine or fluorescein isothiocyanate molecules grafted on a chitosan backbone. In order to validate the possible usage of these chitosan-fluorophores conjugates for fluorescence imaging purposes in cancer diagnostics and therapy, their biological effect was assessed on SVEC4-10 cells (a simian virus 40-transformed mouse microvascular endothelial cell line). Cell viability, membrane integrity and nanogels uptake were examined following exposure for 6 and 24 h at concentrations up to 120 µg/mL. A good biocompatibility was obtained after both time intervals of incubation with nanogels, with no increase in cell death or membrane damage being noticed as compared to control. By examination on confocal laser scanning microscopy, both types of fluorescent nanogels agglomerated on the surface of the cell membrane, their cellular internalization being observed only for few cells, preferentially at the cell periphery. In conclusion, based on the biocompatibility of the nanogels, these can further incorporate gadolinium for an improved magnetic resonance imaging effect in nanomedicine.

Hydraulic consequences of enzymatic breakdown of grapevine pit membranes

2021 ◽  
Author(s):  
Ana Clara Fanton ◽  
Craig Brodersen
Keyword(s):  
Hydraulic Conductivity ◽  
Vascular System ◽  
Membrane Surface ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Biological Response ◽  
Plant Host ◽  
Important Species ◽  
Membrane Area ◽  
Pit Membrane

Abstract Xylella fastidiosa (Xf) is the xylem-dwelling bacterial agent associated with Pierce’s Disease (PD), which leads to significant declines in productivity in agriculturally important species like grapevine (Vitis vinifera). Xf spreads through the xylem network by digesting the pit membranes between adjacent vessels, thereby potentially changing the hydraulic properties of the stem. However, the effects of Xf on water transport varies depending on the plant host and the infection stage, presenting diverse outcomes. Here, we investigated the effects of polygalacturonase, an enzyme known to be secreted by Xf when it produces biofilm on the pit membrane surface, on stem hydraulic conductivity and pit membrane integrity. Experiments were performed on six grapevine genotypes with varying levels of PD resistance, with the expectation that pit membrane resistance to degradation by polygalacturonase may play a role in PD-resistance. Our objective was to study a single component of this pathosystem in isolation to better understand the mechanisms behind reported changes in hydraulics, thereby excluding the biological response of the plant to the presence of Xf in the vascular system. Pit membrane damage only occurred in stems perfused with polygalacturonase. Although the damaged pit membrane area was small (2-9% of the total pit aperture area), membrane digestion led to significant changes in the median air-seeding thresholds, and most importantly, shifted frequency distribution. Finally, enzyme perfusion also resulted in a universal reduction in stem hydraulic conductivity, suggesting the development of tyloses may not be the only contributing factor to reduced hydraulic conductivity in infected grapevine.

scholarly journals Effects of freezing and activation on membrane quality and DNA damage in Xenopus tropicalis and Xenopus laevis spermatozoa

2017 ◽  
Vol 29 (8) ◽  
pp. 1556 ◽  
Author(s):  
S. Morrow ◽  
J. Gosálvez ◽  
C. López-Fernández ◽  
F. Arroyo ◽  
W. V. Holt ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Subsequent Development ◽  
Xenopus Tropicalis ◽  
Model Organisms ◽  
Sperm Chromatin ◽  
Dna Integrity ◽  
Sperm Cryopreservation ◽  
Sperm Plasma Membrane

There is growing concern over the effect of sperm cryopreservation on DNA integrity and the subsequent development of offspring generated from this cryopreserved material. In the present study, membrane integrity and DNA stability of Xenopus laevis and Xenopus tropicalis spermatozoa were evaluated in response to cryopreservation with or without activation, a process that happens upon exposure to water to spermatozoa of some aquatic species. A dye exclusion assay revealed that sperm plasma membrane integrity in both species decreased after freezing, more so for X. laevis than X. tropicalis spermatozoa. The sperm chromatin dispersion (SCD) test showed that for both X. tropicalis and X. laevis, activated frozen spermatozoa produced the highest levels of DNA fragmentation compared with all fresh samples and frozen non-activated samples (P < 0.05). Understanding the nature of DNA and membrane damage that occurs in cryopreserved spermatozoa from Xenopus species represents the first step in exploiting these powerful model organisms to understand the developmental consequences of fertilising with cryopreservation-damaged spermatozoa.

scholarly journals New techniques for real-time monitoring of reverse osmosis membrane integrity for virus removal

2018 ◽  
Vol 13 (4) ◽  
pp. 947-957 ◽  
Author(s):  
V. S. Frenkel ◽  
Y. Cohen
Keyword(s):  
Real Time ◽  
Reverse Osmosis ◽  
Health Hazard ◽  
Membrane Damage ◽  
Membrane Integrity ◽  
Enteric Viruses ◽  
Water Stream ◽  
Potential Health ◽  
Integrity Monitoring ◽  
Virus Removal

Abstract This paper presents methodology, concept and results of the WateReuse Foundation project WFR – 09 – 06b when developing a high pressure membrane, reverse osmosis (RO) and nanofiltration (NF) online membrane integrity testing (MIT) technique. The use of pressure-driven membrane processes, particularly RO, has grown significantly over the past few decades in water treatment and reuse applications to safeguard water supplies against harmful pathogens and impurities. In principle, RO membranes should provide a complete physical barrier to the passage of nanosize pathogens (e.g., enteric viruses). However, in the presence of imperfections and/or membrane damage, membrane breaches as small as 20 to 30 nm can allow enteric viruses to pass through the membrane and contaminate the product water stream, thereby posing a potential health hazard that is of particular concern for potable water production. This project was focused on evaluating a pulsed-marker membrane integrity monitoring (PM-MIMo) approach for RO processes on the basis of the use of a fluorescent marker. The monitoring approach employs pulsed dosing (via a precision metering pump) of a marker into the RO feed stream coupled with online marker concentration monitoring in the RO permeate by an inline spectrofluorometer. Membrane integrity is then inferred on the basis of real-time analysis of the marker permeate time − profile concentration in response. The basic concept of the PM-MIMo approach for detecting membrane breaches was successfully demonstrated, by comparing intact and damaged membranes, in a series of experiments using a diagnostic plate-and-frame RO system and spiral-wound RO pilot system. Results of the developed technique are presented in the project report to allow the industry to consider adopting this technique for RO/NF online integrity monitoring.

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