Expression of AMP-activated Protein Kinase Subunit Isoforms in Masseter and Tibialis Anterior Muscles of Mice before and after Weaning

The AMP-activated protein kinase (AMPK) acts as a fuel gauge during exercise and stress-induced energy crisis. The function of the masseter muscle changes during postnatal development, along with an alteration in type of muscle fiber. We investigated expression of AMPK subunit isoforms in masseter muscle by quantitative real-time RT-PCR and Western blotting, and compared it with that in tibialis anterior muscle in 2-, 4and 9-week-old mice. The most abundantly expressed isoform of the catalytic subunit was α2, and those of the regulatory subunits were β1, β2 and γ1 in both types of muscle; mRNA expression of all the main isoforms in masseter muscle was higher than that in tibialis anterior muscle. Expression of α protein increased with development in both types of muscle. Messenger RNA expression of regulatory subunit isoforms β1 and γ1 in masseter muscle increased, together with an increase in the amounts of their corresponding proteins. On the other hand, mRNA expression of these isoforms in tibialis anterior muscle decreased with development, while their corresponding proteins increased at a similar rate to that of the development of the α subunit. This altered expression of AMPK subunit isoforms in each muscle during postnatal development may be related to alteration in function of each type of muscle. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16