Leptin Stimulates Fatty Acid Oxidation and Peroxisome Proliferator-Activated Receptor α Gene Expression in Mouse C2C12 Myoblasts by Changing the Subcellular Localization of the α2 Form of AMP-Activated Protein Kinase

Abstract

Leptin stimulates fatty acid oxidation in skeletal muscle through the activation of AMP-activated protein kinase (AMPK) and the induction of gene expression, such as that for peroxisome proliferator-activated receptor α (PPARα). We now show that leptin stimulates fatty acid oxidation and PPARα gene expression in the C2C12 muscle cell line through the activation of AMPK containing the α2 subunit (α2AMPK) and through changes in the subcellular localization of this enzyme. Activated α2AMPK containing the β1 subunit was shown to be retained in the cytoplasm, where it phosphorylated acetyl coenzyme A carboxylase and thereby stimulated fatty acid oxidation. In contrast, α2AMPK containing the β2 subunit transiently increased fatty acid oxidation but underwent rapid translocation to the nucleus, where it induced PPARα gene transcription. A nuclear localization signal and Thr¹⁷² phosphorylation of α2 were found to be essential for nuclear translocation of α2AMPK, whereas the myristoylation of β1 anchors α2AMPK in the cytoplasm. The prevention of α2AMPK activation and the change in its subcellular localization inhibited the metabolic effects of leptin. Our data thus suggest that the activation of and changes in the subcellular localization of α2AMPK are required for leptin-induced stimulation of fatty acid oxidation and PPARα gene expression in muscle cells.

SUPPLEMENTAL MATERIAL

This work was supported by a Grant-in-Aid for Scientific Research (B) (16390062) (to Y.M.), a Grant-in-Aid for Exploratory Research (17659069) (to Y.M.), a Grant-in-Aid for Young Scientists (A) (18689023) (to A.S.), and a Grant-in-Aid for Young Scientists (B) (18790629) (to S.O.) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan; a research award from Diko Foundation (to Y.M.); the Smoking Research Foundation (to Y.M.); and the Japan Foundation for Applied Enzymology (to Y.M.).

We thank H. Esumi and T. Ogura for expression plasmids, K. Kameda (Ehime University, Japan) for a constitutively active form of the α1 subunit of AMPK used as a positive control for the AMPK activity assay, and the Center for Analytical Instruments at the National Institute for Basic Biology (Okazaki) for DNA sequencing.