TAILIEUCHUNG - Báo cáo Y học: Expression of uncoupling protein-3 in subsarcolemmal and intermyofibrillar mitochondria of various mouse muscle types and its modulation by fasting

Uncoupling protein-3 (UCP3) is a mitochondrial innermembrane protein abundantly expressed in rodent and human skeletal muscle which may be involved in energy dissipation. Many studies have been performed on the metabolic regulation of UCP3 mRNA level, but little is known about UCP3 expression at the protein level. Two populations of mitochondria have been described in skeletal muscle, subsarcolemmal (SS) and intermyofibrillar (IMF), which differ in their intracellular localization and possibly also their metabolic role | Eur. J. Biochem. 269 2878-2884 2002 FEBS 2002 doi Expression of uncoupling protein-3 in subsarcolemmal and intermyofibrillar mitochondria of various mouse muscle types and its modulation by fasting Maria Jimenez Cedric Yvon Lorenz Lehr Bertrand Léger Patrick Keller Aaron Russell Francoise Kuhne Pierre Flandin Jean-Paul Giacobino and Patrick Muzzin Department of Medical Biochemistry Faculty of Medicine University of Geneva Switzerland Uncoupling protein-3 UCP3 is a mitochondrial inner-membrane protein abundantly expressed in rodent and human skeletal muscle which may be involved in energy dissipation. Many studies have been performed on the metabolic regulation of UCP3 mRNA Ivvel uut litile is known about UCP3 expression at the protein level. Two populations ofmitochondria have been described in skeletal muscle subsarcolemmal SS and intermyofibrillar IMF which differ in their intracellular localization and possibly also their metabolic role. To examine if UCP3 ÍS diffeven-tially expressed in these two populations and in different mouse muscle types we developed a new protocol for isolation ofSS and IMF mitochondria and carefully validated a new UCP3 antibody. The data show that the density ofUCP3 is higher in the mitochondria ofglycolytic muscles tibialis anterior and gastrocnemius than in those ofoxi-dative muscle soleus . They also show that SS mitochondria contain more UCP3 per mg ofprotein than IMF mitochondria. Taken together these results suggest that oxidative muscle and the mitochondria most closely associated with myofibrils are most efficient at producing ATP. We then determined the effect of a 44-h fast which e i ytly increases UCP3 mRNA in muscle on UCP3 protein expression in gastrocnemius mitochondria. We found that fasting moderately increases or does not change UCP3 protein in gastrocnemius SS or IMF mitochondria respectively. These results show that modulation ofUCP3 expression at the mRNA level .

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