Reptilian uncoupling protein: functionality and expression in sub-zero temperatures
2008
SUMMARY Here we report the partial nucleotide sequence of a reptilian uncoupling
protein (repUCP) gene from the European common lizard ( Lacerta
vivipara ). Overlapping sequence analysis reveals that the protein shows
55%, 72% and 77% sequence homology with rat UCP1, UCP2 and UCP3, respectively,
and 73% with bird and fish UCPs. RepUCP gene expression was ubiquitously
detected in 4°C cold-acclimated lizard tissues and upregulated in muscle
tissues by a 20 h exposure to sub-zero temperatures in a supercooling state or
after thawing. In parallel, we show an increase in the co-activators,
peroxisome proliferator-activated receptor γ coactivator-1α
(PGC-1α) and peroxisome proliferator-activated receptors (PPAR), mRNA
expression, suggesting that the mechanisms regulating UCP expression may be
conserved between mammals (endotherms) and reptiles (ectotherms). Furthermore,
mitochondria extracted from lizard skeletal muscle showed a guanosine
diphosphate (GDP)-sensitive non phosphorylating respiration. This last result
indicates an inhibition of extra proton leakage mediated by an uncoupling
protein, providing arguments that repUCP is functional in lizard tissues. This
result is associated with a remarkable GDP-dependent increase in mitochondrial
endogenous H 2 O 2 production. All together, these data
support a physiological role of the repUCP in superoxide limitation by lizard
mitochondria in situations of stressful oxidative reperfusion following a
re-warming period in winter.
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