[Show abstract][Hide abstract] ABSTRACT: The yeast cell wall is constantly remodeled to enable cell growth and division. In this study, we describe a novel type of cell wall modification. We report that the drug amiodarone induces rapid channel formation within the cell wall of the yeast Hansenula polymorpha. Light microscopy shows that shortly after adding amiodarone, spherical structures, which can be stained with DNA binding dyes, form on the cell surface. Electron microphotographs show that amiodarone induces the formation of channels 50-80 nm in diameter in the cell wall that appear to be filled with intracellular material. Using fluorescent microscopy, we demonstrate MitoTracker-positive DNA-containing structures visibly extruded from the cells through these channels. We speculate that the observed channel formation acts to enable the secretion of mitochondrial material from the cell under stressful conditions, thus enabling adaptive changes to the extracellular environment.
[Show abstract][Hide abstract] ABSTRACT: Cell senescence is dependent on the arrest in cell cycle. Here we studied the role of mitochondrial retrograde response signaling in yeast cell survival under a prolonged arrest. We have found that, unlike G1, long-term arrest in mitosis or S phase results in a loss of colony-forming abilities. Consistent with previous observations, loss of mitochondrial DNA significantly increased the survival of arrested cells. We found that this was because the loss increases the duration of G1 phase. Unexpectedly, retrograde signaling, which is typically triggered by a variety of mitochondrial dysfunctions, was found to be a negative regulator of the survival after the release from S-phase arrest induced by the telomere replication defect. Deletion of retrograde response genes decreased the arrest-induced death in such cells, whereas deletion of negative regulator of retrograde signaling MKS1 had the opposite effect. We provide evidence that these effects are due to alleviation of the strength of the S-phase arrest.
[Show abstract][Hide abstract] ABSTRACT: Dissipation of transmembrane potential inhibits mitochondrial fusion and thus prevents reintegration of damaged mitochondria into the mitochondrial network. Consequently, damaged mitochondria are removed by autophagy. Does transmembrane potential directly regulate the mitochondrial fusion machinery? It was shown that inhibition of ATP-synthase induces fragmentation of mitochondria while preserving transmembrane potential. Moreover, mitochondria of the yeast Saccharomyces cerevisiae retain the ability to fuse even in the absence of transmembrane potential. Metazoan mitochondria in some cases retain ability to fuse for a short period even in a depolarized state. It also seems unlikely that transmembrane potential-based regulation of mitochondrial fusion would prevent reintegration of mitochondria with damaged ATP-synthase into the mitochondrial network. Such reintegration could lead to clonal expansion of mtDNAs harboring deleterious mutations in ATP synthase. We speculate that transmembrane potential is not directly involved in regulation of mitochondrial fusion but affects mitochondrial NTP/NDP ratio, which in turn regulates their fusion.
No preview · Article · May 2015 · Biochemistry (Moscow)
[Show abstract][Hide abstract] ABSTRACT: There are two main pathways of ATP biosynthesis: glycolysis and oxidative phosphorylation. As a rule, the two pathways are not fully active in a single cell. In this review, we discuss mechanisms of glycolytic inhibition of respiration (Warburg and Crabtree effects). What are the reasons for the existence of this negative feedback? It is known that maximal activation of both processes can cause generation of reactive oxygen species. Oxidative phosphorylation is more efficient from the energy point of view, while glycolysis is safer and favors biomass synthesis. This might be the reason why quiescent cells are mainly using oxidative phosphorylation, while the quickly proliferating ones — glycolysis.
No preview · Article · May 2015 · Biochemistry (Moscow)
[Show abstract][Hide abstract] ABSTRACT: During the last decade, several pieces of convincing evidence were published indicating that aging of living organisms is programmed, being a particular case of programmed death of organism (phenoptosis). Among them, the following observations can be mentioned . Species were described that show negligible aging. In mammals, the naked mole rat is the most impressive example. This is a rodent of mouse size living at least 10-fold longer than a mouse and having fecundity higher than a mouse and no age-related diseases . In some species with high aging rate, genes responsible for active organization of aging by poisoning of the organism with endogenous metabolites have been identified . In women, standard deviations divided by the mean are the same for age of menarche (an event controlled by the ontogenetic program) and for age of menopause (an aging-related event) . Inhibitors of programmed cell death (apoptosis and necrosis) retard and in certain cases even reverse the development of age-dependent pathologies . In aging species, the rate of aging is regulated by the individual which responds by changes in this rate to changes in the environmental conditions. In this review, we consider point  in detail. Data are summarized suggesting that inhibition of aging rate by moderate food restriction can be explained assuming that such restriction is perceived by the organism as a signal of future starvation. In response to this dramatic signal, the organism switches off such an optional program as aging, mobilizing in such a way additional reserves for survival. A similar explanation is postulated for geroprotective effects of heavy muscle work, a lowering or a rise in the external temperature, small amounts of metabolic poisons (hormesis), low doses of radiation, and other deleterious events. On the contrary, sometimes certain positive signals can prolong life by inhibiting the aging program in individuals who are useful for the community (e.g., geroprotective psychological factors). Similarly, dangerous individuals can be eliminated by programmed death due to operation of progeric psychological factors. The interplay of all these signals results in the final decision of the organism concerning its aging - to accelerate or to decelerate this process. Thus, paradoxically, such an originally counterproductive program as aging appears to be useful for the individual since this program can be switched off by the individual for a certain period of time, an action that thereby increases its resources in crucial periods of life.
No preview · Article · Apr 2015 · Current Aging Science
[Show abstract][Hide abstract] ABSTRACT: Here we present a concept that considers organism aging as an additional facultative function promoting evolution, but counterproductive for an individual. We hypothesize that aging can be inhibited or even arrested when full mobilization of all resources is needed for the survival of an individual. We believe that the organism makes such a decision based on the analysis of signals of special receptors that monitor a number of parameters of the internal and external environment. The amount of available food is one of these parameters. Food restriction is perceived by the organism as a signal of coming starvation; in response to it, the organism inhibits its counterproductive programs, in particular, aging. We hypothesize that the level of protein obtained with food is estimated based on blood concentration of one of the essential amino acids (methionine), of carbohydrates - via glucose level, and fats - based on the level of one of the free fatty acids. When the amount of available food is sufficient, these receptors transmit the signal allowing aging. In case of lack of food, this signal is cancelled, and as a result aging is inhibited, i.e. age-related weakening of physiological functions is inhibited, and lifespan increases (the well-known geroprotective effect of partial food restriction). In Caenorhabditis elegans, lowering of the ambient temperature has a similar effect. This geroprotective effect is removed by the knockout of one of the cold receptors, and replacement of the C. elegans receptor by a similar human receptor restores the ability of low temperature to increase the lifespan of the nematode. A chain of events linking the receptor with the aging mechanism has been discovered in mice - for one of the pain receptors in neurons, the nerve endings of which entwine pancreas β-cells. Age-related activation of these receptors inhibits the work of insulin genes in β-cells. Problems with insulin secretion lead to oxidative stress, chronic inflammation, and type II diabetes, which can be regarded as one of the forms of senile phenoptosis. In conclusion, we consider the role of some psychological factors in the regulation of the aging program.
No preview · Article · Oct 2014 · Biochemistry (Moscow)
[Show abstract][Hide abstract] ABSTRACT: Multiple drug resistance pumps are potential drug targets. Here we asked whether the lipophilic cation dodecyltriphenylphosphonium (C12TPP) can interfere with their functioning. First, we found that suppression of ABC transporter gene PDR5 increases the toxicity of C12TPP in yeast. Second, C12TPP appeared to prevent the efflux of rhodamine 6G - a fluorescent substrate of Pdr5p. Moreover, C12TPP increased the cytostatic effects of some other known Pdr5p substrates. The chemical nature of C12TPP suggests that after Pdr5p-driven extrusion the molecules return to the plasma membrane and then into the cytosol, thus effectively competing with other substrates of the pump.
Full-text · Article · Jul 2014 · Biochemical and Biophysical Research Communications
[Show abstract][Hide abstract] ABSTRACT: Vectors for the expression of the CefT transporter of the MFS family in Acremonium chrysogenum--a producer of beta-lactam antibiotic cephalosporin C--and in Saccharomyces cerevisiae as a fusion with the cyan fluorescent protein (CFP) have been created. The subcellular localization of the CefT-CFP hybrid protein in yeast cells has been investigated. It was shown that the CefT-CFP hybrid protein is capable of complementation of the qdr3, tpo 1, and tpo3 genes encoding for orthologous MFS transporters of Saccharomycetes, making the corresponding strains resistant to spermidine, ethidium bromide, and hygromycin B. High-yield strain VKM F-4081D of A. chrysogenum, expressing the cefT-cfp fusion, was obtained by an agrobacteria conjugated transfer. It was also shown that the constitutive expression of cefT in A. chrysogenum VKM F-4081D led to a change in the biosynthetic profiles of cephalosporin C and its precursors. This resulted in a 25-35% decrease in the finite product accumulated in the cultural liquid with a simultaneous increase in the concentration of its intermediators.
Full-text · Article · Jan 2014 · Prikladnaia biokhimiia i mikrobiologiia
[Show abstract][Hide abstract] ABSTRACT: In search of fluorescent uncouplers of oxidative phosphorylation, three esters of fluorescein, n-butyl-, n-octyl-, and n-dodecyl-oxycarbonyl-fluorescein (C4-FL, C8-FL, C12-FL) were synthesized and characterized. With increasing liposomal lipid content, the long-chain alkyl derivatives of fluorescein (C8-FL, C12-FL and commercially available C18-FL), but not C4-FL and unsubstituted fluorescein, exhibited an increase in fluorescence polarization reflecting the dye binding to liposomes. C12-FL induced proton permeability in lipid membranes, while C4-FL was inactive. In contrast to C4-FL and C18-FL, C12-FL and C8-FL increased the respiration rate and decreased the membrane potential of isolated rat liver mitochondria with half-maximal effective concentrations of 700 nM and 300 nM, respectively. The effect of Cn-FL on the respiration correlated with that on proton permeability of the inner mitochondrial membrane, as measured by induction of mitochondria swelling in the potassium acetate medium. Binding of C8-FL to mitochondria depended on their energization, which was apparently associated with pH gradient generation across the inner mitochondrial membrane in the presence of a respiratory substrate. In wild-type yeast cells, C12-FL localized predominantly in plasma membrane, whereas in AD1-8 mutants lacking MDR pumps, it stained cytoplasmic organelles with some preference for mitochondria. Fluorescent uncouplers can be useful as a tool for determining its localization in a cell or distribution between different tissues in a living animal by fluorescent microscopy.
[Show abstract][Hide abstract] ABSTRACT: During the last decade, evidence has been accumulating supporting the hypothesis that aging is genetically programmed and, therefore, precisely timed. This hypothesis poses a question: what is the mechanism of the biological clock that controls aging? Measuring the level of the advanced glycation end products (AGE) is one of the possible principles underlying the functioning of the biological clock. Protein glycation is an irreversible, non-enzymatic, and relatively slow process. Moreover, many types of cells have receptors that can measure AGE level. We propose the existence of a protein that has a lifespan comparable to that of the whole organism. Interaction of the advanced glycation end product generated from this protein with a specific AGE receptor might initiate apoptosis in a vitally important non-regenerating tissue that produces a primary juvenile hormone. This could result in the age-dependent decrease in the level of this hormone leading to aging of the organism.
[Show abstract][Hide abstract] ABSTRACT: Glycolysis lies at the basis of metabolism and cell energy supply. The disregulation of glycolysis is involved in such pathological processes as cancer proliferation, neurodegenerative diseases, and amplification of ischemic damage. Phosphofructokinase-2 (PFK-2), a bifunctional enzyme and regulator of glycolytic flux, has recently emerged as a promising anticancer target. Herein, the computer-aided design of a new class of aminofurazan-triazole regulators of PFK-2 is described along with the results of their in vitro evaluation. The aminofurazan-triazoles differ from other recently described inhibitors of PFK-2 and demonstrate the ability to modulate glycolytic flux in rat muscle lysate, producing a twofold decrease by inhibitors and fourfold increase by activators. The most potent compounds in the series were shown to inhibit the kinase activity of the hypoxia-inducible form of PFK-2, PFKFB3, as well as proliferation of HeLa, lung adenocarcinoma, colon adenocarcinoma, and breast cancer cells at concentrations in the low micromolar range.
[Show abstract][Hide abstract] ABSTRACT: they fuse and divide. Here we summarize data on the protein machinery driving mitochondrial dynamics in yeast and also discuss the factors that affect the fusion-fission balance. Fission is a general stress response of cells, and in the case of yeast this response appears to be prosurvival. At the same time, even under normal conditions yeast mitochondria undergo continuous cycles of fusion and fission. This seems to be a futile cycle and also expensive from the energy point of view. Why does it exist? Benefits might be the same as in the case of sexual reproduction. Indeed, mixing and separating of mitochondrial content allows mitochondrial DNA to segregate and recombine randomly, leading to high variation in the numbers of mutations per individual mitochondrion. This opens a possibility for effective purifying selection-elimination of mitochondria highly contaminated by deleterious mutations. The beneficial action presumes a mechanism for removal of defective mitochondria. We argue that selective mitochondrial autophagy or asymmetrical distribution of mitochondria during cell division could be at the core of such mechanism.
Full-text · Article · Jul 2013 · Oxidative Medicine and Cellular Longevity
[Show abstract][Hide abstract] ABSTRACT: Vectors for the expression of MFS transporter CefT of Acremonium chrysogenum—a producer of beta-lactam antibiotic cephalosporin C—and in Saccharomyces cerevisiae as a fusion with the cyan fluorescent protein (CFP) have been generated. The subcellular localization of the CefT-CFP hybrid protein in yeast cells has been investigated. It was shown that the CefT-CFP hybrid protein is capable of complementation of the qdr3, tpo1, and tpo3 genes encoding for orthologous MFS transporters of Saccharomycetes, making the corresponding strains resistant to spermidine, ethidium bromide, and hygromycin B. High-producing strain A. chrysogenum VKM F 4081D, expressing the cefT-cfp fusion construct, was obtained by an agrobacteria mediated transformation. It was also shown that the constitutive expression of cefT in A. chrysogenum VKM F-4081D led to a change in the biosynthetic profiles of cephalosporin C and its precursors. This resulted in a 25–35% decrease in the amount of the final product accumulated in the cultural liquid with a simultaneous increase in the concentration of its intermediates.
[Show abstract][Hide abstract] ABSTRACT: Since the times of the Bible, an extract of black cumin seeds was used as a medicine to treatmany human pathologies. Thymoquinone (2-demethylplastoquinone derivative) was identified as an active antioxidant component of this extract. Recently, it was shown that conjugates of plastoquinone and penetrating cations are potent mitochondria-targeted antioxidants effective in treating a large number of age-related pathologies. This review summarizes new data on the antioxidant and some other properties of membrane-penetrating cationic compounds where 2-demethylplastoquinone substitutes for plastoquinone. It was found that such a substitution significantly increases a window between anti- and prooxidant concentrations of the conjugates. Like the original plastoquinone derivatives, the novel compounds are easily reduced by the respiratory chain, penetrate through model and natural membranes, specifically accumulate in mitochondria in an electrophoretic fashion, and strongly inhibit H2O2-induced apoptosis at pico- and nanomolar concentrations in cell cultures. At present, cationic demethylplastoquinone derivatives appear to be the most promising mitochondria-targeted drugs of the quinone series.
[Show abstract][Hide abstract] ABSTRACT: Protonophorous uncouplers causing a partial decrease in mitochondrial membrane potential are promising candidates for therapeutic applications. Here we showed that hydrophobic penetrating cations specifically targeted to mitochondria in a membrane potential-driven fashion increased proton-translocating activity of the anionic uncouplers 2,4-dinitrophenol (DNP) and carbonylcyanide-p-trifluorophenylhydrazone (FCCP). In planar bilayer lipid membranes (BLM) separating two compartments with different pH values, DNP-mediated diffusion potential of H(+) ions was enhanced in the presence of dodecyltriphenylphosphonium cation (C12TPP). The mitochondria-targeted penetrating cations strongly increased DNP- and carbonylcyanide m-chlorophenylhydrazone (CCCP)-mediated steady-state current through BLM when a transmembrane electrical potential difference was applied. Carboxyfluorescein efflux from liposomes initiated by the plastoquinone-containing penetrating cation SkQ1 was inhibited by both DNP and FCCP. Formation of complexes between the cation and CCCP was observed spectophotometrically. In contrast to the less hydrophobic tetraphenylphosphonium cation (TPP), SkQ1 and C12TPP promoted the uncoupling action of DNP and FCCP on isolated mitochondria. C12TPP and FCCP exhibited a synergistic effect decreasing the membrane potential of mitochondria in yeast cells. The stimulating action of penetrating cations on the protonophore-mediated uncoupling is assumed to be useful for medical applications of low (non-toxic) concentrations of protonophores.
[Show abstract][Hide abstract] ABSTRACT: Stressed Saccharomyces cerevisiae cells easily lose respiratory function due to deletions in mitochondrial DNA, and this increases their general stress resistance. Is the loss active? We found that erythromycin (an inhibitor of mitochondrial translation) prevents the loss in control cells but not in the ones expressing mitochondrially-encoded protein Var1 in the nucleus. Var1 is a component of mitochondrial ribosomes; it is hydrophilic, positively charged, and prone to aggregation. Addition of DNase altered Var1 content in a preparation of mitochondrial nucleoids. Our data indicate that Var1 physically interacts with mitochondrial DNA and under stress negatively regulates its maintenance.
No preview · Article · Mar 2013 · European journal of cell biology