Brown adipose tissue (BAT) expresses two uncoupling proteins, UCP1 and UCP3. While the physiological role played by UCP1 is quite well established, that of UCP3 has not been elucidated yet. To obtain further insight into this aspect, we evaluated the impact of the absence of this protein on BAT mitochondria. To this aim, we used 8 weeks old wild type (WT) and UCP3 knockout (KO) female mice, housed at thermoneutrality. We performed functional, molecular and histological analysis. The lack of UCP3 significantly reduces respiration rate of alpha-glycerophosphate energized mitochondria (when detected in basal condition, in the presence of GDP, as well as in the presence of FCCP) and the amplitude of membrane potential, thus indicating an inhibition of the respiratory chain activity. At the same time, the absence of UCP3 enhances both the percentage of electrons leaking from respiratory chain and reducing oxygen to superoxide, and the mitochondrial level of lipid hydroperoxides, i.e. two factors known to influence the activity of the respiratory chain complexes and their assembly in supercomplexes. In line with this possibility, our BN-PAGE-based analysis shows a significant inhibition of the in gel activities of both complex I and complex IV in mitochondria from BAT of UCP3 KO mice compared to WT controls. In addition the analysis of the electrophoretic profile of supercomplexes, obtained from digitonin-solubilized mitochondria, shows that mitochondria from UCP3 KO mice contain significant lower amount of specific respiratory supercomplexes, whose apparent molecular weight is between 800 kDa and 750 kDa. Moreover, in UCP3 KO mice, variations in mitochondrial functionality are also associated with alterations in mitochondrial morphology, as revealed by electron microscopy analysis. As a whole, these data indicate that in BAT UCP3 plays a significant role in influencing respiratory chain complexes activity and assembly, thus preserving mitochondrial functionality.
Absence of UCP3 Influences mitochondrial functionality in brown adipose tissue.
DE MATTEIS, RITA;
2016
Abstract
Brown adipose tissue (BAT) expresses two uncoupling proteins, UCP1 and UCP3. While the physiological role played by UCP1 is quite well established, that of UCP3 has not been elucidated yet. To obtain further insight into this aspect, we evaluated the impact of the absence of this protein on BAT mitochondria. To this aim, we used 8 weeks old wild type (WT) and UCP3 knockout (KO) female mice, housed at thermoneutrality. We performed functional, molecular and histological analysis. The lack of UCP3 significantly reduces respiration rate of alpha-glycerophosphate energized mitochondria (when detected in basal condition, in the presence of GDP, as well as in the presence of FCCP) and the amplitude of membrane potential, thus indicating an inhibition of the respiratory chain activity. At the same time, the absence of UCP3 enhances both the percentage of electrons leaking from respiratory chain and reducing oxygen to superoxide, and the mitochondrial level of lipid hydroperoxides, i.e. two factors known to influence the activity of the respiratory chain complexes and their assembly in supercomplexes. In line with this possibility, our BN-PAGE-based analysis shows a significant inhibition of the in gel activities of both complex I and complex IV in mitochondria from BAT of UCP3 KO mice compared to WT controls. In addition the analysis of the electrophoretic profile of supercomplexes, obtained from digitonin-solubilized mitochondria, shows that mitochondria from UCP3 KO mice contain significant lower amount of specific respiratory supercomplexes, whose apparent molecular weight is between 800 kDa and 750 kDa. Moreover, in UCP3 KO mice, variations in mitochondrial functionality are also associated with alterations in mitochondrial morphology, as revealed by electron microscopy analysis. As a whole, these data indicate that in BAT UCP3 plays a significant role in influencing respiratory chain complexes activity and assembly, thus preserving mitochondrial functionality.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
