Developmental significance of cyanide-resistant respiration under stressed conditions: experiments in Dictyostelium cells.
We have previously reported that benzohydroxamic acid (BHAM), a potent inhibitor of cyanide (CN)-resistant respiration mediated by alternative oxidase (AOX), induces formation of unique cell masses (i.e., stalk-like cells with a large vacuole and thick cell wall) in starved Dictyostelium cells. Unexpectedly, however, aox-null cells prepared by homologous recombination exhibited normal development under normal culture conditions on agar, indicating that BHAM-induced stalk formation is not solely attributable to inhibition of CN-resistant respiration. This also suggests that a series of pharmacological approaches in the field of life science has serious limitations. Under stress (e.g., in submerged culture), starved aox-null cells exhibited slightly delayed aggregation compared with parental Ax-2 cells; most cells remained as loose aggregates even after prolonged incubation. Also, the developmental defects of aox-null cells became more marked upon incubation for 30 min just after starvation in the presence of ≥ 1.75 mmol/L H(2)O(2). This seems to indicate that CN-resistant respiration could mitigate cellular damage through reactive oxygen species (ROS), because AOX has a potential role in reduction of ROS production. Starved aox-null cells did not develop in the presence of 5 mmol/L KCN (which completely inhibited the conventional cytochrome-mediated respiration) and remained as non-aggregated single cells on agar even after prolonged incubation. Somewhat surprisingly, however, parental Ax-2 cells were found to develop normally, forming fruiting bodies even in the presence of 10 mmol/L KCN. Taken together, these results suggest that CN-resistant respiration might compensate for the production of adenosine tri-phosphate via oxidative phosphorylation.
Kimura
Kei
K
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan.
Kuwayama
Hidekazu
H
Amagai
Aiko
A
Maeda
Yasuo
Y
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D019069:Cell Respiration / Q000187:drug effects; D004023:Dictyostelium / Q000166:cytology / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D024101:Mitochondrial Proteins; D018384:Oxidative Stress / Q000187:drug effects*; D010088:Oxidoreductases / Q000378:metabolism; D010766:Phosphorylation; D010940:Plant Proteins; D011190:Potassium Cyanide / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D000099188:Alternative Oxidase
D000255:Adenosine Triphosphate; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D011190:Potassium Cyanide; D017382:Reactive Oxygen Species; D000099188:Alternative Oxidase