The expression of UCP3 directly correlates to UCP1 abundance in brown adipose tissue

https://doi.org/10.1016/j.bbabio.2015.10.011Get rights and content
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Highlights

  • UCP3 amount in BAT is 0.51 ng/(μg total protein) and is essentially higher than it is in muscles and the heart.

  • UCP3 amount in BAT is nearly 400 times lower than the UCP1 amount.

  • The specific UCP3 transport function may be coherent with the proton transport function of highly abundant UCP1.

  • function of highly abundant UCP1.

Abstract

UCP1 and UCP3 are members of the uncoupling protein (UCP) subfamily and are localized in the inner mitochondrial membrane. Whereas UCP1's central role in non-shivering thermogenesis is acknowledged, the function and even tissue expression pattern of UCP3 are still under dispute. Because UCP3 properties regarding transport of protons are qualitatively identical to those of UCP1, its expression in brown adipose tissue (BAT) alongside UCP1 requires justification. In this work, we tested whether any correlation exists between the expression of UCP1 and UCP3 in BAT by quantification of protein amounts in mouse tissues at physiological conditions, in cold-acclimated and UCP1 knockout mice. Quantification using recombinant UCP3 revealed that the UCP3 amount in BAT (0.51 ng/(μg total tissue protein)) was nearly one order of magnitude higher than that in muscles and heart. Cold-acclimated mice showed an approximate three-fold increase in UCP3 abundance in BAT in comparison to mice in thermoneutral conditions. Surprisingly, we found a significant decrease of UCP3 in BAT of UCP1 knockout mice, whereas the protein amount in skeletal and heart muscles remained constant. UCP3 abundance decreased even more in cold-acclimated UCP1 knockout mice. Protein quantification in UCP3 knockout mice revealed no compensatory increase in UCP1 or UCP2 expression. Our results do not support the participation of UCP3 in thermogenesis in the absence of UCP1 in BAT, but clearly demonstrate the correlation in abundance between both proteins. The latter is important for understanding UCP3's function in BAT.

Abbreviations

BAT
brown adipose tissue
He
heart
GMsc
gastrocnemius muscle
mUCP3
recombinant uncoupling protein 3
RT
room temperature
ScM
scapulae muscle
SkM
skeletal muscle
Sp
spleen
Th
thymus
WB
Western blot

Keywords

Recombinant protein
Anti-UCP3 antibody
UCP3 knockout mice
Cold-acclimated mice
Skeletal muscles
Uncoupling protein 2

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1

Present address: Department of Anatomy, Charité-Universitätsmedizin Berlin, Germany.