Absence of mitochondrial uncoupling protein 3: Effect on thymus and spleen in the fed and fasted mice

Abstract

Mitochondrial uncoupling protein 3 (UCP3) is consituitively expressed in mitochondria from thymus and spleen of mice, and confocal microscopy has been used to visualize UCP3 in situ in mouse thymocytes. UCP3 is present decrease by a half in thymus and a fifth in spleen after three weeks, probably reflecting the suckling to weaning transition. UCP3 protein levels increase ~3-fold in thymus on starvation, but expression levels in spleen were unaffected by starvation. Lack of UCP3 had little effect on thymus mass or thymocyte number . However, lack of UCP3 affected spleen mass and splenocyte number (in the fasted state) and results in reduced CD4+ single positive cell numbers and reduced double negative cells in the thymus, but as a 2-fold increase in the proportion of CD4 + , CD8 + and DP cells in spleen. Starvation attenuates these proportionate differences in the spleen. A lack of UCP3 had no apparent effect on basal oxygen consumption of thymocytes or splenocytes or on oxygen consumption due to mitochondrial proton leak. Splenocytes from UCP3 knock-out mice are also more resistant to apoptosis than those from wild-type mice. Overall we can conclude that UCP3 affects thymocyte and spleen cell profiles in the fed and fasted state.