MiPsummer Programme pdf - Mitochondrial Physiology Society

82
Abstract # 50
MITOCHONDRIAL CARRIER PROTEINS IN FATTY ACID ACTIVATED UNCOUPLING
IN DIFFERENT TISSUES OF HIBERNATING GROUND SQUIRRELS
Komelina N.P., Amerkhanov Z.G.
Institute of Cell Biophysics Russian Academy of Science, Pushchino, Russia.
Background.
Fatty acid - induced uncoupling of mitochondria is known to be mediated by some anion carriers, as
uncoupling proteins (UCPs), adenine nucleotide translocase (ANT) and aspartate/glutamate
antiporter. Well-studied UCP1 in brown fat produce heat using this mechanism. UCP1 activity is
tightly regulated, being inhibited by purine nucleotides and activated by free fatty acids. It is
supposed that similar properties are inherent in UCP2 and UCP3 homologues in different tissues.
ANT is also involved in the fatty acid-induced uncoupling and responsible for the major part of the
thermoregulatory uncoupling in heart- and skeletal- muscle mitochondria of cold-exposure rats and
hibernating ground squirrels.
Objectives.
The aim of our investigation was to reveal functional activity of UCP2 and UCP3 using recoupling
effect of purine nucleotides and to differentiate them from the contribution of ANT in the uncoupling
using its high-specific inhibitor - carboxyatractylate.
Methods.
We measured respiration rate of mitochondria in the presence of oligomycin and rotenone under
addition of 100µM laurate. We tried different order of additions of inhibitors to demonstrate their
independent effects. We used recoupling effect of GDP to indicate activity of UCP3 in skeletal
muscle and UCP2 in lung and spleen of long-tailed hibernating ground squirrels. Mitochondria of
liver were taken as negative control, since there are no any UCPs at significant level. Hibernating
ground squirrels as the object ensured increased level of all UCPs during winter season.
Results.
We found that GDP in millimolar concentrations had
a slight recoupling effect on respiration rate and
membrane potential in all studied mitochondria of
hibernating ground squirrels, including skeletal
muscle, lung, spleen and liver mitochondria.
However, GDP had no effect, if carboxyatractylate in
micromolar concentration was added previously. No
crucial differences were found in compare to liver
mitochondria. At the same time, evident and
independent recoupling effect of glutamate before as
well as after carboxyatractylate, demonstrate activity
of aspartate/glutamate antiporter in fatty acid –
induced uncoupling.
Conclusion.
We concluded that recoupling effect of purine nucleotides in skeletal muscle, lung, spleen and liver
mitochondria of hibernating ground squirrels can be explained by their interaction with ANT rather
then by functioning of UCP2 and UCP3.
Acknowledgments.
This work was partly supported by the Program ‘Integration of Molecular Systems in Physiological Functions’ of the
Russian Academy of Sciences and grant 12-04-31326 from the Russian Fund for Basic Research.