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Proc Natl Acad Sci U S A. 2017 Jul 25;114(30):7981-7986. doi: 10.1073/pnas.1705406114. Epub 2017 Jun 19.

UCP1 deficiency causes brown fat respiratory chain depletion and sensitizes mitochondria to calcium overload-induced dysfunction.

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Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115.
Department of Cell Biology, Harvard Medical School, Boston, MA 02115.
Department of Neurosurgery, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02215.
Division of Endocrinology, Beth Israel Deaconess Medical Center, Boston, MA 02215.
Department of Genetics, Harvard Medical School, Boston, MA 02215.
MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom.
Division of Sleep and Circadian Disorders, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02215.
Division of Sleep Medicine, Department of Medicine, Harvard Medical School, Boston, MA 02115.
Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115;


Brown adipose tissue (BAT) mitochondria exhibit high oxidative capacity and abundant expression of both electron transport chain components and uncoupling protein 1 (UCP1). UCP1 dissipates the mitochondrial proton motive force (Δp) generated by the respiratory chain and increases thermogenesis. Here we find that in mice genetically lacking UCP1, cold-induced activation of metabolism triggers innate immune signaling and markers of cell death in BAT. Moreover, global proteomic analysis reveals that this cascade induced by UCP1 deletion is associated with a dramatic reduction in electron transport chain abundance. UCP1-deficient BAT mitochondria exhibit reduced mitochondrial calcium buffering capacity and are highly sensitive to mitochondrial permeability transition induced by reactive oxygen species (ROS) and calcium overload. This dysfunction depends on ROS production by reverse electron transport through mitochondrial complex I, and can be rescued by inhibition of electron transfer through complex I or pharmacologic depletion of ROS levels. Our findings indicate that the interscapular BAT of Ucp1 knockout mice exhibits mitochondrial disruptions that extend well beyond the deletion of UCP1 itself. This finding should be carefully considered when using this mouse model to examine the role of UCP1 in physiology.


ROS; UCP1; brown fat; electron transport chain; mitochondria

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