Localization of exercise- and denervation-responsive elements in the mouseGLUT4 gene

Exercise training increases the expression of GLUT4 in skeletal muscle. Pre vious studies demonstrated that the exercise-responsive element(s) of the m urine GLUT4 gene are located between bases -1001 and -442 relative to the t ranscription start site. To further characterize the regulatory elements in the GLUT4 gene, the regulation of GLUT4 minigenes containing -701, -551, - 442, or -423 bp of the 5'-flanking region was studied in transgenic mice. A ll minigenes studied showed significant expression in skeletal muscle and h eart, including the -423 GLUT4 minigene that lacked the msocyte enhancer fa ctor 2 (MEF2)-binding domain (-CTAAAAA-TAG-) located between bases -437 and -428. The -701-and -551-bp constructs were expressed in brown adipose tiss ues while the -442 and -423 constructs were not. In skeletal muscle, either swimming or treadmill running up-regulated GLUT4 minigene mRNA levels in - 701 and -551 transgenic mice, but not in the -442 and -423 transgenic mice. Denervation of the gastrocnemius muscle by sectioning of the sciatic nerve down-regulated minigene and endogenous GLUT4 mRNAs in all -701, -551, -442 , and -423 transgenic mice. These data indicate that exercise-responsive el ement(s) and brown adipocyte specific element(s) are located within 109 bp between bases -551 and -442 of the GLUT4 gene, hut that the cia-element for denervation-induced down-regulation of the GLUT4 gene is located downstrea m of base -423. Finally, the MEF2 binding site between bases -437 and -428 is not necessary for expression of GLUT4 in skeletal muscles and heart; the cis-element mediating this effect is also located downstream of base -423. (C) 2000 Academic Press.