Abstract
Mitochondrial alternative oxidase (AOX) is predicted to be present in mitochondria of several invertebrate taxa including tardigrades. Independently of the reason concerning the enzyme occurrence in animal mitochondria, expression of AOX in human mitochondria is regarded as a potential therapeutic strategy. Till now, relevant data were obtained due to heterologous AOX expression in cells and animals without natively expressed AOX. Application of animals natively expressing AOX could importantly contribute to the research. Thus, we decided to investigate AOX activity in intact specimens of the tardigrade Hypsibius exemplaris. We observed that H. exemplaris specimens' tolerance to the blockage of the mitochondrial respiratory chain (MRC) cytochrome pathway was diminished in the presence of AOX inhibitor and the inhibitor-sensitive respiration enabled the tardigrade respiration under condition of the blockage. Importantly, these observations correlated with relevant changes of the mitochondrial inner membrane potential (Δψ) detected in intact animals. Moreover, detection of AOX at protein level required the MRC cytochrome pathway blockage. Overall, we demonstrated that AOX activity in tardigrades can be monitored by the animals' behavior observation as well as by measurement of intact specimens' whole-body respiration and Δψ. Furthermore, it is also possible to check the impact of the MRC cytochrome pathway blockage on AOX level as well as AOX inhibition in the absence of the blockage on animal functioning. Thus, H. exemplaris could be consider as a whole-animal model suitable to study AOX.
Highlights
It is suggested that the mitochondrial respiratory chain (MRC) of many invertebrates contains the alternative oxidase (AOX), an enzyme that provides a secondary oxidative pathway to the classical cytochrome pathway (e.g. [1]) but till natively expressed AOX level and activity have not been detected simultaneously in intact animals
The effect of antimycin A (AA) added separately or in the presence of potassium cyanide (KCN) was tested to check the effectiveness of the MRC cytochrome pathway inhibition by KCN
Since the animal treatment with AA in the presence of KCN did not increase the effect of KCN added separately (Additional file 1), we concluded that addition of KCN caused efficient inhibition of the MRC cytochrome pathway
Summary
It is suggested that the mitochondrial respiratory chain (MRC) of many invertebrates contains the alternative oxidase (AOX), an enzyme that provides a secondary oxidative pathway to the classical cytochrome pathway (e.g. [1]) but till natively expressed AOX level and activity have not been detected simultaneously in intact animals. It is suggested that the mitochondrial respiratory chain (MRC) of many invertebrates contains the alternative oxidase (AOX), an enzyme that provides a secondary oxidative pathway to the classical cytochrome pathway [1]) but till natively expressed AOX level and activity have not been detected simultaneously in intact animals. The tardigrade Hypsibius exemplaris has the active mitochondrial alternative oxidase
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