Mitochondrial responses to anoxia exposure in red eared sliders (Trachemys scripta).

When deprived oxygen, mitochondria from most vertebrates transform from the main site of ATP production to the dominant site of cellular ATP use due to the reverse functioning of the F1FO-ATPase (complex V). The anoxia-tolerant freshwater turtle Trachemys scripta however, has previously been shown to inhibit complex V activity in heart and brain in response to anoxia exposure, but the regulatory mechanism is unknown. To gain insight into the putative regulatory mechanisms underlying the anoxia-induced inhibition of complex V in T. scripta, we examined the effects of two weeks anoxia exposure at 4 °C on the mitochondrial proteome and candidate mechanisms that have been shown to regulate complex V in other organisms. In T. scripta, we confirmed that anoxia exposure resulted in a >80% inhibition of complex V in heart, brain and liver. Incubation of mitochondria with the nitric oxide donor, s-nitrosoglutathione, did not affect complex V activity despite showing the expected inhibition in mice. Proteomics analysis showed anoxia-induced decreases in three peripheral stalk subunits of complex V, possibly pointing to a unique site of regulation. Proteomics analysis also revealed differential expression of numerous enzymes involved with the electron transport system, the tricarboxylic acid cycle, as well as lipid and amino acid metabolism in response to anoxia exposure.