scholarly journals CBMT-17. DEFECTIVE QKI-DEPENDENT LIPID METABOLISM INDUCES GENOMIC INSTABILITY AND SENSITIZES GLIOBLASTOMA TO IMMUNOTHERAPY

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi36-vi36
Author(s):  
Takashi Shingu ◽  
Jian Hu
Keyword(s):  
Genomic Instability ◽  
Mitochondrial Membrane ◽  
Rna Binding ◽  
Cytoplasmic Membrane ◽  
Unsaturated Fatty Acids ◽  
Rna Stability ◽  
Membrane Integrity ◽  
Immune Checkpoints ◽  
Mitochondrial Defects ◽  
And Function

Abstract Despite transformative effects on the therapy of cancers such as melanoma and lung adenocarcinoma, blockade of the T cell immune checkpoints has generated limited impact on glioblastoma. Identifying genetic/genomic alterations that could potentially sensitize the patients to immunotherapy will significantly improve the efficacy of immunotherapy on glioblastoma patients. As part of our effort to identify novel glioma suppressors that affect the interaction of GSCs with their microenvironment, we discovered that the RNA-binding protein Quaking (QKI) is a key regulator of cellular endocytosis. QKI is mutated or deleted in ~34% of human glioblastomas. Supporting QKI’s tumor suppresser function, 92% of the Nestin-CreERT2;QkiL/L;PtenL/L;p53L/L mice developed glioblastoma with a median survival of 105 days, however, the Nestin-CreERT2;PtenL/L;p53L/L mice did not develop any glioma up to a year. Mechanistically, QKI regulates the RNA stability and alternative splicing of numerous protein and lipid components of endolysosomes, particularly the unsaturated fatty acids (UFAs). Functionally, deletion of Qki and inhibition of UFA biosynthesis both decrease endolysosome-mediated receptor degradation, thereby enriching receptors on the cytoplasmic membrane (e.g., Frizzled and Notch1) that are essential for maintaining stemness. This enrichment of receptor signaling enables GSCs to cope with the low ligand levels during their invasion. On the other hand, lower lysosomal activity induced by Qki deletion and UFA loss led to defective mitophagy. We also found that insufficient UFAs in mitochondrial membrane significantly compromised mitochondrial membrane integrity and function. These two mechanisms concomitantly led to accumulation of damaged mitochondria and higher levels of reactive oxygen species (ROS), and consequently genomic instability. Lastly, we found that the higher level of genomic instability induced by Qki loss rendered cells more sensitive to anti-CTLA4 and anti-PD1 antibodies. Taken together, our data suggest that Qki/UFA loss-induced endolysosomal and mitochondrial defects promote gliomagenesis yet render cells vulnerabilities that could be harnessed for therapeutic purposes.

Extracellular antibacterial substances in Anabaena fertilissima CCC597 kill bacteria by triggering oxidative radicals and destroying membrane integrity

Nova Hedwigia ◽  
2020 ◽  
Vol 110 (3) ◽  
pp. 247-267
Author(s):  
Trashi Singh ◽  
Pushpendra Kumar Dwivedi ◽  
Suvendra Nath Bagchi
Keyword(s):  
Cytoplasmic Membrane ◽  
Unsaturated Fatty Acids ◽  
Membrane Integrity ◽  
Antibacterial Properties ◽  
Axenic Culture ◽  
Test Organism ◽  
Concomitant Increase ◽  
Anabaena Fertilissima ◽  
Membrane Bound ◽  
Cytosolic Acidification

An axenic culture of a cyanobacterium in the spent medium produced hexane-extracta- ble compound(s) that antagonized growth of several Gram+ve and –ve bacteria, including a few potential pathogens. Phylogenetic investigations classified the strain to be Anabaena fertilissima strain CCC597. Using Escherichia coli MTCC443 as a test organism, we have shown that ROS (O 2; H 2O 2) production and outer and inner membrane (OM: IM) permeabilization were induced upon such treatments. Consequently, leakage of proteins and cytosolic acidification processes were initi- ated. Suppression of cytoplasmic membrane-bound respiratory O 2consumption was most likely the physiological aberration that killed the bacteria. Several antioxidant enzymes viz. superoxide dis- mutase, catalase, and peroxidases showed concomitant increase in the enzymatic activities and band intensities in the corresponding substrate gels. Notwithstanding, the counteraction mechanism(s) was not preventive, and sufficient oxidative radicals still generated to manifest lipid peroxidation. Chemical analysis of the hexane-extract of A. fertilissima culture filtrates revealed presence of a number of long chain unsaturated fatty acids, including cis-13,16-docosadienoic acid, with proven antibacterial properties.

DFF40 translocates to the mitochondria during apoptosis and regulates mitochondrial integrity and function

2021 ◽  
Author(s):  
Merve Kulbay ◽  
Bruno Johnson ◽  
Guillaume Ricaud ◽  
Marie-Noelle Séguin-Grignon ◽  
Valérie Malboeuf ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Cell Metabolism ◽  
Membrane Integrity ◽  
Basal Respiration ◽  
Mtdna Copy Number ◽  
Apoptosis Resistance ◽  
Atp Production ◽  
Mitochondrial Integrity ◽  
Resistance Pathway ◽  
And Function

Abstract DNA fragmentation factor 40 (DFF40), or the caspase-activated DNase (CAD), is an endonuclease specific for double-stranded DNA. Alterations in its function and expression have been linked to apoptosis resistance, a mechanism likely used by cancer cells. Although, how the DFF40-related apoptosis resistance pathway occurs remains unclear. Here we sought to determine if DFF40 could localize to the mitochondrion, a localization not reported in the literature until now, and further regulate cell metabolism when apoptosis is activated. We demonstrated that DFF40 localizes in mitochondria through its N-terminal domain, and its agglomeration is accentuated in apoptosis-activated cells. We also found that a loss of DFF40 expression induces a higher mitochondrial mass, mtDNA copy number, mitochondrial membrane potential, and glycolysis rates in resting T cells. The induction of apoptosis in DFF40 deficient cells doesn’t alter ATP production levels, basal respiration, and mitochondrial membrane integrity. Our study reveals that DFF40 may act as a regulator of mitochondria, and its loss could compromise mitochondrial integrity in pathologies such as cancer.

scholarly journals Rbfox2 is Critical for Maintaining Alternative Polyadenylation and Mitochondrial Health in Myoblasts

2020 ◽  
Author(s):  
Jun Cao ◽  
Elizabeth Jaworski ◽  
Kempaiah Rayavara ◽  
KarryAnne Belanger ◽  
Amanda Sooter ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Rna Binding ◽  
Heart Diseases ◽  
Mitochondrial Gene ◽  
Alternative Polyadenylation ◽  
Mitochondrial Genes ◽  
Fine Tuning ◽  
Inner Mitochondrial Membrane ◽  
Altered Expression ◽  
And Function

ABSTRACTThe RNA binding protein RBFOX2 is linked to heart and skeletal muscle diseases; yet, RBFOX2-regulated RNA networks have not been systematically identified. Although RBFOX2 has a well-known function in alternative splicing (AS), it is unclear whether RBFOX2 has other roles in RNA metabolism that affect gene expression and function. Utilizing state of the art techniques Poly(A)-ClickSeq (PAC-seq) and nanopore cDNA sequencing, we revealed a new role for RBFOX2 in fine tuning alternative polyadenylation (APA) of pre-mRNAs in myoblasts. We found that depletion of RBFOX2 altered expression of mitochondrial genes. We identified the mitochondrial gene Slc25a4 gene that transports ATP/ADP across inner mitochondrial membrane as a target of RBFOX2. Dissecting how RBFOX2 affects Slc25a4 APA uncovered that RBFOX2 binding motifs near the distal polyadenylation site (PAS) are critical for expression of Slc25a4. Consistent with changes in expression of mitochondrial genes, loss of RBFOX2 altered mitochondrial membrane potential and induced mitochondrial swelling. Our results unveiled a novel role for RBFOX2 in maintaining APA decisions and expression of mitochondrial genes in myoblasts relevant to heart diseases.

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 Recent Advances and Future Prospects in Immune Checkpoint (ICI)-Based Combination Therapy for Advanced HCC

Cancers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1949
Author(s):  
Yawen Dong ◽  
Jeffrey Sum Lung Wong ◽  
Ryohichi Sugimura ◽  
Ka-On Lam ◽  
Bryan Li ◽  
...  
Keyword(s):  
Immune Checkpoint ◽  
Cytotoxic T Lymphocyte ◽  
Checkpoint Inhibitors ◽  
Immune Checkpoints ◽  
Advanced Hcc ◽  
Oncogenic Pathways ◽  
Vegf Pathway ◽  
And Function ◽  
Endothelial Growth Factor

Advanced, unresectable hepatocellular carcinoma has a dismal outcome. Multiple immune checkpoint inhibitors (ICIs) targeting the programmed-cell death 1 pathway (PD-1/L1) have been approved for the treatment of advanced HCC. However, outcomes remain undesirable and unpredictable on a patient-to-patient basis. The combination of anti-PD-1/L1 with alternative agents, chiefly cytotoxic T-lymphocyte antigen-4 (CTLA-4) ICIs or agents targeting other oncogenic pathways such as the vascular endothelial growth factor (VEGF) pathway and the c-MET pathway, has, in addition to the benefit of directly targeting alterative oncogenic pathways, in vitro evidence of synergism through altering the genomic and function signatures of T cells and expression of immune checkpoints. Several trials have been completed or are underway evaluating such combinations. Finally, studies utilizing transcriptomics and organoids are underway to establish biomarkers to predict ICI response. This review aims to discuss the biological rationale and clinical advances in ICI-based combinations in HCCs, as well as the progress and prospects of the search for the aforementioned biomarkers in ICI treatment of HCC.

scholarly journals Genomic instability induced by radiation-mimicking chemicals is not associated with persistent mitochondrial degeneration

2021 ◽  
Author(s):  
Luukkonen Jukka ◽  
Höytö Anne ◽  
Sokka Miiko ◽  
Syväoja Juhani ◽  
Juutilainen Jukka ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Ionizing Radiation ◽  
Genomic Instability ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Function ◽  
Mitochondrial Membrane ◽  
Neuroblastoma Cells ◽  
Superoxide Production ◽  
Mitochondrial Activity ◽  
Mitochondrial Superoxide

AbstractIonizing radiation has been shown to cause induced genomic instability (IGI), which is defined as a persistently increased rate of genomic damage in the progeny of the exposed cells. In this study, IGI was investigated by exposing human SH-SY5Y neuroblastoma cells to hydroxyurea and zeocin, two chemicals mimicking different DNA-damaging effects of ionizing radiation. The aim was to explore whether IGI was associated with persistent mitochondrial dysfunction. Changes to mitochondrial function were assessed by analyzing mitochondrial superoxide production, mitochondrial membrane potential, and mitochondrial activity. The formation of micronuclei was used to determine immediate genetic damage and IGI. Measurements were performed either immediately, 8 days, or 15 days following exposure. Both hydroxyurea and zeocin increased mitochondrial superoxide production and affected mitochondrial activity immediately after exposure, and mitochondrial membrane potential was affected by zeocin, but no persistent changes in mitochondrial function were observed. IGI became manifested 15 days after exposure in hydroxyurea-exposed cells. In conclusion, immediate responses in mitochondrial function did not cause persistent dysfunction of mitochondria, and this dysfunction was not required for IGI in human neuroblastoma cells.

scholarly journals Plasma membrane integrity in health and disease: significance and therapeutic potential

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Catarina Dias ◽  
Jesper Nylandsted
Keyword(s):  
Plasma Membrane ◽  
Therapeutic Potential ◽  
Calcium Influx ◽  
Membrane Integrity ◽  
Cell Types ◽  
Physical Parameters ◽  
Membrane Repair ◽  
Plasma Membrane Integrity ◽  
Repair Mechanisms ◽  
And Function

AbstractMaintenance of plasma membrane integrity is essential for normal cell viability and function. Thus, robust membrane repair mechanisms have evolved to counteract the eminent threat of a torn plasma membrane. Different repair mechanisms and the bio-physical parameters required for efficient repair are now emerging from different research groups. However, less is known about when these mechanisms come into play. This review focuses on the existence of membrane disruptions and repair mechanisms in both physiological and pathological conditions, and across multiple cell types, albeit to different degrees. Fundamentally, irrespective of the source of membrane disruption, aberrant calcium influx is the common stimulus that activates the membrane repair response. Inadequate repair responses can tip the balance between physiology and pathology, highlighting the significance of plasma membrane integrity. For example, an over-activated repair response can promote cancer invasion, while the inability to efficiently repair membrane can drive neurodegeneration and muscular dystrophies. The interdisciplinary view explored here emphasises the widespread potential of targeting plasma membrane repair mechanisms for therapeutic purposes.

scholarly journals Analysis of mitochondrial morphology and function with novel fixable fluorescent stains.

1996 ◽  
Vol 44 (12) ◽  
pp. 1363-1372 ◽  
Author(s):  
M Poot ◽  
Y Z Zhang ◽  
J A Krämer ◽  
K S Wells ◽  
L J Jones ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Epifluorescence Microscopy ◽  
Mitochondrial Morphology ◽  
Microtubule Network ◽  
Multiple Features ◽  
Permeabilized Cells ◽  
Dye Staining ◽  
And Function

Investigation of mitochondrial morphology and function has been hampered because photostable, mitochondrion-specific stains that are retained in fixed, permeabilized cells have not been available. We found that in live cell preparations, the CMXRos and H2-CMXRos dyes were more photostable than rhodamine 123. In addition, fluorescence and morphology of mitochondria stained with the CMXRos and CMXRos-H2 dyes were preserved even after formaldehyde fixation and acetone permeabilization. Using epifluorescence microscopy, we showed that CMXRos and H2-CMXRos dye fluorescence fully co-localized with antibodies to subunit I of cytochrome c oxidase, indicating that the dyes specifically stain mitochondria. Confocal microscopy of these mitochondria yielded colored banding patterns, suggesting that these dyes and the mitochondrial enzyme localize to different suborganellar regions. Therefore, these stains provide powerful tools for detailed analysis of mitochondrial fine structure. We also used poisons that decrease mitochondrial membrane potential and an inhibitor of respiration complex II to show by flow cytometry that the fluorescence intensity of CMXRos and H2-CMXRos dye staining responds to changes in mitochondrial membrane potential and function. Hence, CMXRos has the potential to monitor changes in mitochondrial function. In addition, CMXRos staining was used in conjunction with spectrally distinct fluorescent probes for the cell nucleus and the microtubule network to concomitantly evaluate multiple features of cell morphology.

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