oligomycins and propionic-acid

Mitochondrial dysfunction can lead to diverse cellular and organismal responses. We used DNA microarrays to characterize the transcriptional responses to different mitochondrial perturbations in Saccharomyces cerevisiae. We examined respiratory-deficient petite cells and respiratory-competent wild-type cells treated with the inhibitors of oxidative phosphorylation antimycin, carbonyl cyanide m-chlorophenylhydrazone, or oligomycin. We show that respiratory deficiency, but not inhibition of mitochondrial ATP synthesis per se, induces a suite of genes associated with both peroxisomal activities and metabolite-restoration (anaplerotic) pathways that would mitigate the loss of a complete tricarboxylic acid cycle. The array data suggested, and direct microscopic observation of cells expressing a derivative of green fluorescent protein with a peroxisomal matrix-targeting signal confirmed, that respiratory deficiency dramatically induces peroxisome biogenesis. Transcript profiling of cells harboring null alleles of RTG1, RTG2, or RTG3, genes known to control signaling from mitochondria to the nucleus, suggests that there are multiple pathways of cross-talk between these organelles in yeast.

Topics: Antimycin A; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Citric Acid Cycle; DNA-Binding Proteins; Enzyme Inhibitors; Fungal Proteins; Gene Expression Regulation, Fungal; Gene Silencing; Genome, Fungal; Intracellular Signaling Peptides and Proteins; Mitochondria; Oligomycins; Oligonucleotide Array Sequence Analysis; Peroxisomes; Phosphorylation; Propionates; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Transcription Factors; Transcription, Genetic

Presynaptic function was investigated at K+-stimulated motor nerve terminals in snake costocutaneous nerve muscle preparations exposed to carbonyl cyanide m-chlorophenylhydrazone (CCCP, 2 M), oligomycin (8 g x ml(-1)) or CCCP and oligomycin together. Miniature endplate currents (MEPCs) were recorded at -150 mV with two-electrode voltage clamp. With all three drug treatments, during stimulation by elevated K+ (35 mM), MEPC frequencies initially increased to values > 350 s(-1), but then declined. The decline occurred more rapidly in preparations treated with CCCP or CCCP and oligomycin together than in those treated with oligomycin alone. Staining with FM1-43 indicated that synaptic vesicle membrane endocytosis occurred at some CCCP- or oligomycin-treated nerve terminals after 120 or 180 min of K+ stimulation, respectively. The addition of glucose to stimulate production of ATP by glycolysis during sustained K+ stimulation attenuated the decline in MEPC frequency and increased the percentage of terminals stained by FM1-43 in preparations exposed to either CCCP or oligomycin. We propose that the decline in K+-stimulated quantal release in preparations treated with CCCP, oligomycin or CCCP and oligomycin together could result from a progressive elevation of intracellular calcium concentration ([Ca2+]i). For oligomycin-treated nerve terminals, a progressive elevation of [Ca2+]i could occur as the cytoplasmic ATP/ADP ratio decreases, causing energy-dependent Ca2+ buffering mechanisms to fail. The decline in MEPC frequency could occur more rapidly in preparations treated with CCCP or CCCP and oligomycin together because mitochondrial Ca2+ buffering and ATP production were both inhibited. Therefore, the proposed sustained elevation of [Ca2+]i could occur more rapidly.

Topics: Action Potentials; Adenosine Triphosphate; Animals; Calcium; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Colubridae; Endocytosis; Enzyme Inhibitors; Fluorescent Dyes; Glucose; Mitochondria; Motor Endplate; Muscle Fibers, Skeletal; Muscle, Skeletal; Oligomycins; Patch-Clamp Techniques; Potassium; Propionates; Pyridinium Compounds; Quaternary Ammonium Compounds; Synaptic Vesicles; Uncoupling Agents

The folate-dependent catabolism of serine was studied in intact rat liver mitochondria and soluble extracts from sonicated mitochondria. Formate and CO2 are both known to be products of the mitochondrial oxidation of carbon 3 of serine. The present work tests the proposal [Barlowe, C. K., & Appling, D. R. (1988) Biofactors 1, 171-176] that carbon 3 of serine is first oxidized to 10-formyltetrahydrofolate, which can be either oxidized to CO2 or converted to formate. Oxidation of carbon 3 of serine to formate and CO2 was shown to be dependent on the respiratory state of the mitochondria. Formate production was greatest in state-3 (actively respiring) mitochondria and lowest in uncoupled mitochondria. In contrast, CO2 production was greatest in uncoupled mitochondria and lowest in respiratory-inhibited mitochondria. Formate production appeared to be favored when high concentrations of NADP+ and ADP were present, but there was no clear correlation between the NADP+:NADPH redox state and CO2 production. In soluble mitochondrial extracts, CO2 production depended on NADP+ and tetrahydrofolate, whereas formate production required ADP in addition to NADP+ and the reduced folate cofactor. Unlike CO2 production, however, formate production showed a complete dependence on a polyglutamylated form of the folate cofactor. These experiments support the proposed folate-mediated serine oxidation as a major pathway for the flux of one-carbon units through mitochondria.

Topics: Adenosine Diphosphate; Animals; Carbon Dioxide; Folic Acid; Formates; Formyltetrahydrofolates; Male; Mitochondria, Liver; NADP; Oligomycins; Oxidation-Reduction; Propionates; Rats; Rats, Sprague-Dawley; Serine