AMPK Methods and Protocols

unrelated to metabolic issues [2, 3, 6]. Historically, the first con-

nection between AMPK and protein synthesis has been established

in hepatocytes [7, 8]. These studies demonstrated an AMPK-

mediated reduction of protein translation correlating to the inhibi-

tion of two of its important signaling regulators, the p70 ribosomal

S6 protein kinase (p70S6K) and the eukaryotic elongation factor-

2 (eEF2), involved in the pre-initiation and elongation steps of

protein formation, respectively (Fig. 1). The precise molecular

mechanism linking AMPK to these elements has been deciphered

later and implicates several AMPK substrates. First, AMPK phos-

phorylates and activates the eEF2 kinase (eEF2K) responsible for

eEF2 inactivation [7, 9, 10] (Fig.1). Second, AMPK inhibits

Fig. 1AMPK activation inhibits different signaling pathways involved in cardiac hypertrophy. This scheme
represents the four main pathways involved in hypertrophy development. They comprise the ERK1/2 and NFAT
pathways involved in the stimulation of transcription of pro-hypertrophic genes (left part) and the p70S6K and
eEF2 pathways involved in the stimulation of protein synthesis (right part). AMPK inhibits these four pathways
(seetext for more details).Dashed linesindicate indirect activation or inhibition. Abbreviations: CaM
calmodulin,IGF-1insulin-like growth factor-1,PDK1phosphoinositide-dependent kinase-1,PEphenylpehr-
ine,PI3Kphosphatidylinositol-3-kinase,PIP 2 phosphatidylinositol 4,5-bisphosphate,PIP 3 phosphatidylinositol
3,4,5-triphosphate,PKBprotein kinase B,PKCprotein kinase C,pS6ribosomal protein S6

322 Florence Mailleux et al.