Research ArticlePhysiology

MNK2 Inhibits eIF4G Activation Through a Pathway Involving Serine-Arginine–Rich Protein Kinase in Skeletal Muscle

Sci. Signal.  14 Feb 2012:
Vol. 5, Issue 211, pp. ra14
DOI: 10.1126/scisignal.2002466

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Limiting Muscle Mass

Skeletal muscle mass changes in response to activity, the availability of nutrients, and pathologic loss of muscle mass are associated with long-term bed rest, cachexia-inducing diseases, and starvation. Hu et al. used overexpression, knockout, and knockdown studies to show that the kinase MNK2 had a negative regulatory role on proteins involved in protein synthesis under atrophy-promoting conditions. This was unexpected because MNK2 is also part of a eukaryotic translation initiation complex and is one of the two isoforms capable of phosphorylating a component of that complex on a site associated with promotion of protein synthesis. The negative regulatory effects on protein synthesis machinery appeared to involve a kinase-independent interaction with mTOR, a master regulator of protein synthesis, and a kinase-dependent regulation of another kinase, SRPK, which had not been previously implicated in regulation of protein synthesis.