Send to

Choose Destination
J Biol Chem. 2017 Feb 3;292(5):2032-2045. doi: 10.1074/jbc.M116.753277. Epub 2016 Dec 12.

Signal Integration at Elongation Factor 2 Kinase: THE ROLES OF CALCIUM, CALMODULIN, AND SER-500 PHOSPHORYLATION.

Author information

From the Graduate Program in Cell and Molecular Biology and
Division of Chemical Biology and Medicinal Chemistry, University of Texas, Austin, Texas 78712.
From the Graduate Program in Cell and Molecular Biology and.
the Department of Chemistry, City College of New York, New York, New York 10031, and.
the Graduate Center, City University of New York, New York, New York 10016.
From the Graduate Program in Cell and Molecular Biology and


Eukaryotic elongation factor 2 kinase (eEF-2K), the only calmodulin (CaM)-dependent member of the unique α-kinase family, impedes protein synthesis by phosphorylating eEF-2. We recently identified Thr-348 and Ser-500 as two key autophosphorylation sites within eEF-2K that regulate its activity. eEF-2K is regulated by Ca2+ ions and multiple upstream signaling pathways, but how it integrates these signals into a coherent output, i.e. phosphorylation of eEF-2, is unclear. This study focuses on understanding how the post-translational phosphorylation of Ser-500 integrates with Ca2+ and CaM to regulate eEF-2K. CaM is shown to be absolutely necessary for efficient activity of eEF-2K, and Ca2+ is shown to enhance the affinity of CaM toward eEF-2K. Ser-500 is found to undergo autophosphorylation in cells treated with ionomycin and is likely also targeted by PKA. In vitro, autophosphorylation of Ser-500 is found to require Ca2+ and CaM and is inhibited by mutations that compromise binding of phosphorylated Thr-348 to an allosteric binding pocket on the kinase domain. A phosphomimetic Ser-500 to aspartic acid mutation (eEF-2K S500D) enhances the rate of activation (Thr-348 autophosphorylation) by 6-fold and lowers the EC50 for Ca2+/CaM binding to activated eEF-2K (Thr-348 phosphorylated) by 20-fold. This is predicted to result in an elevation of the cellular fraction of active eEF-2K. In support of this mechanism, eEF-2K knock-out MCF10A cells reconstituted with eEF-2K S500D display relatively high levels of phospho-eEF-2 under basal conditions. This study reports how phosphorylation of a regulatory site (Ser-500) integrates with Ca2+ and CaM to influence eEF-2K activity.


CaMK-III; S500D; Ser-500; Thr-348; calcium; calmodulin (CaM); eEF-2K; phosphorylation; translation; translation elongation factor

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center