AMP-activated Protein Kinase Up-regulates Mitogen-activated Protein (MAP) Kinase-interacting Serine/Threonine Kinase 1a-dependent Phosphorylation of Eukaryotic Translation Initiation Factor 4E

Xiaoqing Zhu,Vivian Dahlmans,Ramon Thali,Christian Preisinger,Benoit Viollet,J Willem Voncken,Dietbert Neumann

doi:10.1074/jbc.c116.740498

Abstract

AMP-activated protein kinase (AMPK) is a molecular energy sensor that acts to sustain cellular energy balance. Although AMPK is implicated in the regulation of a multitude of ATP-dependent cellular processes, exactly how these processes are controlled by AMPK as well as the identity of AMPK targets and pathways continues to evolve. Here we identify MAP kinase-interacting serine/threonine protein kinase 1a (MNK1a) as a novel AMPK target. Specifically, we show AMPK-dependent Ser(353) phosphorylation of the human MNK1a isoform in cell-free and cellular systems. We show that AMPK and MNK1a physically interact and that in vivo MNK1a-Ser(353) phosphorylation requires T-loop phosphorylation, in good agreement with a recently proposed structural regulatory model of MNK1a. Our data suggest a physiological role for MNK1a-Ser(353) phosphorylation in regulation of the MNK1a kinase, which correlates with increased eIF4E phosphorylation in vitro and in vivo.

Highlights

Balancing catabolic and anabolic processes is fundamental to energy homeostasis and metabolic adaptation
MAP kinaseinteracting serine/threonine protein kinase 1a (MNK1a) Is a Novel AMPK Target in Vitro—The online tool Scansite predicted the presence of a putative AMPK phosphorylation motif LQRNSSTMDL in MNK1a; this domain is absent in MNK1b
Mnk1aWT and MNK1aS352A were clearly detected by autoradiography, the MNK1aS353A mutant protein was not radiolabeled under these conditions (Fig. 1E)

Summary

ACCELERATED COMMUNICATION crossmark

AMP-activated Protein Kinase Up-regulates Mitogen-activated Protein (MAP) Kinaseinteracting Serine/Threonine Kinase 1a-dependent Phosphorylation of Eukaryotic Translation Initiation Factor 4E*. We identify MAP kinaseinteracting serine/threonine protein kinase 1a (MNK1a) as a novel AMPK target. High-density protein microarrays enable the rapid identification of potentially novel human kinase substrates at a proteomic scale [18]. Using this strategy, we identified MAP kinase-interacting serine/threonine protein kinase 1 (MNK1) as a putative novel AMPK target [19]. The exact biological relevance of this phosphorylation event is still under debate, cellular eIF4E plays an important role in the regulation of mRNA translation, in which interaction with the 5Ј-cap structure of mRNA appears pivotal [26]. Ing serine/threonine protein kinase; IVK, in vitro kinase; AICAR, 5-aminoimidazole-4-carboxamide ribonucleotide; TPA, 12-O-tetradecanoylphorbol13-acetate; 2PY, double polyoma; bACT, ␤-actin; IP, immunoprecipitated; p, phosphorylated; t, total; MEF, mouse embryonic fibroblast; CBB, Coomassie Brilliant Blue; aa, amino acid(s); IB, immunoblot

Results

Discussion

Experimental Procedures

Willem Voncken and Dietbert Neumann