Stimulation of apoptosis by sulindac and piroxicam

1998 ◽  
Vol 95 (3) ◽  
pp. 385-388 ◽  
Author(s):  
William R. WADDELL
Keyword(s):  
Acetic Acid ◽  
Mitochondrial Membrane ◽  
Prostaglandin Synthesis ◽  
Intermembrane Space ◽  
Colon Polyps ◽  
Inner Mitochondrial Membrane ◽  
Normal Cells ◽  
Inhibition Of Prostaglandin Synthesis ◽  
Stimulation Of

1.Sulindac, cis-5-fluoro-2-methyl-1-(p-methylsulphinylbenzylidene)indene-3-acetic acid, inhibits growth of colon polyps and cancers. This effect has been attributed to inhibition of prostaglandin synthesis but more recent observations indicate that, in vitro, cells that do not have cyclo-oxygenase nor RNA for synthesis of such enzymes are affected by sulindac. Therefore the presumptive effect is probably not correct. 2.It has also been found that sulindac stimulates apoptosis. It is herein postulated that in tumour cells such effects may be due to interaction of the anionic form of the drug with protons in the intermembrane space of mitochondria to disrupt the potential across the inner mitochondrial membrane and thereby initiate apoptosis. Normal cells are not affected.

Dynamic organization of the mitochondrial protein import machinery

2016 ◽  
Vol 397 (11) ◽  
pp. 1097-1114 ◽  
Author(s):  
Sebastian P. Straub ◽  
Sebastian B. Stiller ◽  
Nils Wiedemann ◽  
Nikolaus Pfanner
Keyword(s):  
Mitochondrial Membrane ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Membrane Dynamics ◽  
Intermembrane Space ◽  
Mitochondrial Protein Import ◽  
Precursor Proteins ◽  
Dynamic Cooperation

Abstract Mitochondria contain elaborate machineries for the import of precursor proteins from the cytosol. The translocase of the outer mitochondrial membrane (TOM) performs the initial import of precursor proteins and transfers the precursors to downstream translocases, including the presequence translocase and the carrier translocase of the inner membrane, the mitochondrial import and assembly machinery of the intermembrane space, and the sorting and assembly machinery of the outer membrane. Although the protein translocases can function as separate entities in vitro, recent studies revealed a close and dynamic cooperation of the protein import machineries to facilitate efficient transfer of precursor proteins in vivo. In addition, protein translocases were found to transiently interact with distinct machineries that function in the respiratory chain or in the maintenance of mitochondrial membrane architecture. Mitochondrial protein import is embedded in a regulatory network that ensures protein biogenesis, membrane dynamics, bioenergetic activity and quality control.

scholarly journals In Vitro Import of a Nuclearly Encoded tRNA into the Mitochondrion of Trypanosoma brucei

1999 ◽  
Vol 19 (9) ◽  
pp. 6253-6259 ◽  
Author(s):  
Audra E. Yermovsky-Kammerer ◽  
Stephen L. Hajduk
Keyword(s):  
Membrane Potential ◽  
Trypanosoma Brucei ◽  
Mitochondrial Membrane ◽  
Protein Component ◽  
Proper Function ◽  
Mitochondrial Rna ◽  
Inner Mitochondrial Membrane ◽  
Trna Import ◽  
Trna Substrate

ABSTRACT All of the mitochondrial tRNAs of Trypanosoma bruceihave been shown to be encoded in the nucleus and must be imported into the mitochondrion. The import of nuclearly encoded tRNAs into the mitochondrion has been demonstrated in a variety of organisms and is essential for proper function in the mitochondrion. An in vitro import assay has been developed to study the pathway of tRNA import inT. brucei. The in vitro system utilizes crude isolated trypanosome mitochondria and synthetic RNAs transcribed from a cloned nucleus-encoded tRNA gene cluster. The substrate, composed of tRNASer and tRNALeu, is transcribed in tandem with a 59-nucleotide intergenic region. The tandem tRNA substrate is imported rapidly, while the mature-size tRNALeu fails to be imported in this system. These results suggest that the preferred substrate for tRNA import into trypanosome mitochondria is a precursor molecule composed of tandemly linked tRNAs. Import of the tandem tRNA substrate requires (i) a protein component that is associated with the surface of the mitochondrion, (ii) ATP pools both outside and within the mitochondrion, and (iii) a membrane potential. Dissipation of the proton gradient across the inner mitochondrial membrane by treatment with an uncoupling agent inhibits import of the tandem tRNA substrate. Characterization of the import requirements indicates that mitochondrial RNA import proceeds by a pathway including a protein component associated with the outer mitochondrial membrane, ATP-dependent steps, and a mitochondrial membrane potential.

Prostaglandin independence of kinin-stimulated renin release

1987 ◽  
Vol 252 (5) ◽  
pp. F794-F799 ◽  
Author(s):  
W. H. Beierwaltes
Keyword(s):  
Channel Blocker ◽  
Dienoic Acid ◽  
Prostaglandin Synthesis ◽  
Renin Release ◽  
Cyclooxygenase Inhibitor ◽  
Concomitant Increase ◽  
Isolated Glomeruli ◽  
Free Media ◽  
Stimulation Of

Bradykinin can increase prostaglandin synthesis and also stimulate renin release in vitro. Because prostaglandins also stimulate renin, studies were performed to determine whether bradykinin stimulation of renin is a function of prostaglandin synthesis. Isolated glomeruli with attendant arteriolar attachments were harvested from rat kidneys and superfused. The effluent was analyzed for renin, prostaglandins E2 and I2 (6-keto-PGF1 alpha). Bradykinin (10(-5) M) increased renin by 50% with a concomitant increase in prostacyclin (PGI2) but not in prostaglandin E2 (PGE2). The cyclooxygenase inhibitor meclofenamate (1.6 X 10(-5) M) inhibited bradykinin-induced PGI2 synthesis but not the concurrent increase in renin release. Additionally, neither the phospholipase inhibitor quinacrine (10(-2) M) nor the prostacyclin synthetase inhibitor 9,11-azoprosta-5,13-dienoic acid (Azo analogue-1) (5.67 X 10(-6) M) eliminated bradykinin-induced renin release. Superfusion with calcium-free media and EDTA increased basal renin release 2.5-fold, and bradykinin stimulated a twofold increase in renin release. Neither a high (10(-2) M) media calcium nor the calcium channel blocker nifedipine (10(-6) M) eliminated bradykinin stimulation of renin. These results suggest that bradykinin stimulation of renin is at least partially independent of prostaglandin synthesis and that bradykinin must act by some prostaglandin-independent pathway to induce renin release from isolated glomeruli.

scholarly journals Membrane-tethering of cytochrome c accelerates regulated cell death in yeast

2020 ◽  
Vol 11 (9) ◽  
Author(s):  
Alexandra Toth ◽  
Andreas Aufschnaiter ◽  
Olga Fedotovskaya ◽  
Hannah Dawitz ◽  
Pia Ädelroth ◽  
...  
Keyword(s):  
Cell Death ◽  
Oxidative Phosphorylation ◽  
Mitochondrial Membrane ◽  
Mitochondrial Respiratory Chain ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Fitness Advantage ◽  
Regulated Cell Death ◽  
Membrane Tethering ◽  
Membrane Anchoring

Abstract Intrinsic apoptosis as a modality of regulated cell death is intimately linked to permeabilization of the outer mitochondrial membrane and subsequent release of the protein cytochrome c into the cytosol, where it can participate in caspase activation via apoptosome formation. Interestingly, cytochrome c release is an ancient feature of regulated cell death even in unicellular eukaryotes that do not contain an apoptosome. Therefore, it was speculated that cytochrome c release might have an additional, more fundamental role for cell death signalling, because its absence from mitochondria disrupts oxidative phosphorylation. Here, we permanently anchored cytochrome c with a transmembrane segment to the inner mitochondrial membrane of the yeast Saccharomyces cerevisiae, thereby inhibiting its release from mitochondria during regulated cell death. This cytochrome c retains respiratory growth and correct assembly of mitochondrial respiratory chain supercomplexes. However, membrane anchoring leads to a sensitisation to acetic acid-induced cell death and increased oxidative stress, a compensatory elevation of cellular oxygen-consumption in aged cells and a decreased chronological lifespan. We therefore conclude that loss of cytochrome c from mitochondria during regulated cell death and the subsequent disruption of oxidative phosphorylation is not required for efficient execution of cell death in yeast, and that mobility of cytochrome c within the mitochondrial intermembrane space confers a fitness advantage that overcomes a potential role in regulated cell death signalling in the absence of an apoptosome.

scholarly journals SFXN1 is a mitochondrial serine transporter required for one-carbon metabolism

Science ◽  
2018 ◽  
Vol 362 (6416) ◽  
pp. eaat9528 ◽  
Author(s):  
Nora Kory ◽  
Gregory A. Wyant ◽  
Gyan Prakash ◽  
Jelmi uit de Bos ◽  
Francesca Bottanelli ◽  
...  
Keyword(s):  
Carbon Metabolism ◽  
Mitochondrial Membrane ◽  
Mitochondrial Pathway ◽  
Genetic Screen ◽  
Inner Mitochondrial Membrane ◽  
Unknown Mechanism ◽  
One Carbon Metabolism ◽  
The One ◽  
Mitochondrial Membrane Protein

One-carbon metabolism generates the one-carbon units required to synthesize many critical metabolites, including nucleotides. The pathway has cytosolic and mitochondrial branches, and a key step is the entry, through an unknown mechanism, of serine into mitochondria, where it is converted into glycine and formate. In a CRISPR-based genetic screen in human cells for genes of the mitochondrial pathway, we found sideroflexin 1 (SFXN1), a multipass inner mitochondrial membrane protein of unclear function. Like cells missing mitochondrial components of one-carbon metabolism, those null for SFXN1 are defective in glycine and purine synthesis. Cells lacking SFXN1 and one of its four homologs, SFXN3, have more severe defects, including being auxotrophic for glycine. Purified SFXN1 transports serine in vitro. Thus, SFXN1 functions as a mitochondrial serine transporter in one-carbon metabolism.

Abstract 15070: Micu1 Regulates Mitochondrial Cristae Structure and Function Independent of the Mitochondrial Calcium Uniporter Channel

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Dhanendra Tomar ◽  
Manfred Thomas ◽  
Joanne Garbincius ◽  
Devin Kolmetzky ◽  
Oniel Salik ◽  
...  
Keyword(s):  
Mitochondrial Membrane ◽  
Coiled Coil ◽  
Structure And Function ◽  
Membrane Dynamics ◽  
Size Exclusion ◽  
Null Mouse ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Cytochrome C Release ◽  
And Function

Background: MICU1 is an EF-hand domain containing Ca 2+ -sensor regulating the mitochondrial Ca 2+ uniporter channel and mitochondrial Ca 2+ uptake. MICU1-null mouse and fly models display perinatal lethality with disorganized mitochondrial architecture. Interestingly, these phenotypes are distinct from other mtCU loss-of-function models ( MCU, MICU2, EMRE, MCUR1 ) and thus are likely not explained solely by changes in matrix Ca 2+ content. Using size-exclusion proteomics and co-immunofluorescence, we found that MICU1 localizes to mitochondrial complexes lacking MCU. These observations suggest that MICU1 may have additional cellular functions independent of the MCU. Methods: Biotin-based proximity labeling and proteomics, protein biochemistry, live-cell Ca 2+ imaging, electron microscopy, confocal and super-resolution imaging were utilized to identify and validate MICU1 novel functions. Results: The expression of a MICU1-BioID2 fusion protein in MCU +/+ and MCU -/- cells allowed the identification of the total vs. MCU-independent MICU1 interactome. LC-MS analysis of purified biotinylated proteins identified the mitochondrial contact site and cristae organizing system (MICOS) components Mitofilin (MIC60) and Coiled-coil-helix-coiled-coil helix domain containing 2 (CHCHD2) as MCU independent novel MICU1 interactors. We demonstrate that MICU1 is essential for proper organization of the MICOS complex and that MICU1 ablation results in altered cristae organization, mitochondrial ultrastructure, mitochondrial membrane dynamics, membrane potential, and cell death signaling. We hypothesize that MICU1 is a MICOS Ca 2+ - sensor since perturbing MICU1 is sufficient to modulate cytochrome c release independent of Ca 2+ uptake across the inner mitochondrial membrane. Conclusions: Here, we provide the first experimental evidence of an intermembrane space Ca 2+ - sensor regulating mitochondrial membrane dynamics, independent of changes in matrix Ca 2+ content. This study provides a novel paradigm to understand Ca 2+ -dependent regulation of mitochondrial structure and function and may help explain the mitochondrial remodeling reported to occur in numerous disease states.

scholarly journals Role of cytochrome c heme lyase in mitochondrial import and accumulation of cytochrome c in Saccharomyces cerevisiae.

1991 ◽  
Vol 11 (11) ◽  
pp. 5487-5496 ◽  
Author(s):  
M E Dumont ◽  
T S Cardillo ◽  
M K Hayes ◽  
F Sherman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Mitochondrial Membrane ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Yeast Saccharomyces Cerevisiae ◽  
Apocytochrome C ◽  
Cytochrome C Heme Lyase

Heme is covalently attached to cytochrome c by the enzyme cytochrome c heme lyase. To test whether heme attachment is required for import of cytochrome c into mitochondria in vivo, antibodies to cytochrome c have been used to assay the distributions of apo- and holocytochromes c in the cytoplasm and mitochondria from various strains of the yeast Saccharomyces cerevisiae. Strains lacking heme lyase accumulate apocytochrome c in the cytoplasm. Similar cytoplasmic accumulation is observed for an altered apocytochrome c in which serine residues were substituted for the two cysteine residues that normally serve as sites of heme attachment, even in the presence of normal levels of heme lyase. However, detectable amounts of this altered apocytochrome c are also found inside mitochondria. The level of internalized altered apocytochrome c is decreased in a strain that completely lacks heme lyase and is greatly increased in a strain that overexpresses heme lyase. Antibodies recognizing heme lyase were used to demonstrate that the enzyme is found on the outer surface of the inner mitochondrial membrane and is not enriched at sites of contact between the inner and outer mitochondrial membranes. These results suggest that apocytochrome c is transported across the outer mitochondrial membrane by a freely reversible process, binds to heme lyase in the intermembrane space, and is then trapped inside mitochondria by an irreversible conversion to holocytochrome c accompanied by folding to the native conformation. Altered apocytochrome c lacking the ability to have heme covalently attached accumulates in mitochondria only to the extent that it remains bound to heme lyase.

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