EEF2K explained

Eukaryotic elongation factor-2 kinase (eEF-2 kinase or eEF-2K), also known as calmodulin-dependent protein kinase III (CAMKIII) and calcium/calmodulin-dependent eukaryotic elongation factor 2 kinase,^[1] is an enzyme that in humans is encoded by the EEF2K gene.^[2]

Function

eEF-2 kinase is a highly conserved protein kinase in the calmodulin-mediated signaling pathway that links multiple up-stream signals to the regulation of protein synthesis. It phosphorylates eukaryotic elongation factor 2 (EEF2) and thus inhibits the EEF2 function.^[3]

Activation

The activity of eEF-2K is dependent on calcium and calmodulin. Activation of eEF-2K proceeds by a sequential two-step mechanism. First, calcium-calmodulin binds with high affinity to activate the kinase domain, triggering rapid autophosphorylation of Thr-348.^{[4] [5]} In the second step, autophosphorylation of Thr-348 leads to a conformational change in the kinase likely supported by the binding of phospho-Thr-348 to an allosteric phosphate binding pocket in the kinase domain. This increases the activity of eEF-2K against its substrate, elongation factor 2.

eEF-2K can gain calcium-independent activity through autophosphorylation of Ser-500. However, calmodulin must remain bound to the enzyme for its activity to be sustained.

Clinical significance

The activity of this kinase is increased in many cancers and may be a valid target for anti-cancer treatment.^{[6] [7]}

It is also suggested that eEF-2K may play a role the rapid anti-depressant effects of ketamine through its regulation of neuronal protein synthesis.^[8]

Cancer

eEF-2K expression is often upregulated in cancer cells, including breast and pancreatic cancers and promotes cell proliferation, survival, motility/migration, invasion and tumorigenesis.^{[9] [10]}

Further reading

• Nairn AC, Palfrey HC . Identification of the major Mr 100,000 substrate for calmodulin-dependent protein kinase III in mammalian cells as elongation factor-2 . The Journal of Biological Chemistry . 262 . 36 . 17299–303 . Dec 1987 . 10.1016/S0021-9258(18)45377-X . 3693353 . free .
• Redpath NT, Price NT, Severinov KV, Proud CG . Regulation of elongation factor-2 by multisite phosphorylation . European Journal of Biochemistry . 213 . 2 . 689–99 . Apr 1993 . 8386634 . 10.1111/j.1432-1033.1993.tb17809.x .
• Pavur KS, Petrov AN, Ryazanov AG . Mapping the functional domains of elongation factor-2 kinase . Biochemistry . 39 . 40 . 12216–24 . Oct 2000 . 11015200 . 10.1021/bi0007270 .
• Diggle TA, Subkhankulova T, Lilley KS, Shikotra N, Willis AE, Redpath NT . Phosphorylation of elongation factor-2 kinase on serine 499 by cAMP-dependent protein kinase induces Ca2+/calmodulin-independent activity . The Biochemical Journal . 353 . Pt 3 . 621–6 . Feb 2001 . 11171059 . 1221608 . 10.1042/0264-6021:3530621 .
• Knebel A, Morrice N, Cohen P . A novel method to identify protein kinase substrates: eEF2 kinase is phosphorylated and inhibited by SAPK4/p38delta . The EMBO Journal . 20 . 16 . 4360–9 . Aug 2001 . 11500363 . 125581 . 10.1093/emboj/20.16.4360 .
• Wang X, Li W, Williams M, Terada N, Alessi DR, Proud CG . Regulation of elongation factor 2 kinase by p90(RSK1) and p70 S6 kinase . The EMBO Journal . 20 . 16 . 4370–9 . Aug 2001 . 11500364 . 125559 . 10.1093/emboj/20.16.4370 .
• Arora S, Yang JM, Craft J, Hait W . Detection of anti-elongation factor 2 kinase (calmodulin-dependent protein kinase III) antibodies in patients with systemic lupus erythematosus . Biochemical and Biophysical Research Communications . 293 . 3 . 1073–6 . May 2002 . 12051769 . 10.1016/S0006-291X(02)00324-8 .
• Wistow G, Bernstein SL, Wyatt MK, Fariss RN, Behal A, Touchman JW, Bouffard G, Smith D, Peterson K . Expressed sequence tag analysis of human RPE/choroid for the NEIBank Project: over 6000 non-redundant transcripts, novel genes and splice variants . Molecular Vision . 8 . 205–20 . Jun 2002 . 12107410 .
• Knebel A, Haydon CE, Morrice N, Cohen P . Stress-induced regulation of eukaryotic elongation factor 2 kinase by SB 203580-sensitive and -insensitive pathways . The Biochemical Journal . 367 . Pt 2 . 525–32 . Oct 2002 . 12171600 . 1222910 . 10.1042/BJ20020916 .
• Browne GJ, Finn SG, Proud CG . Stimulation of the AMP-activated protein kinase leads to activation of eukaryotic elongation factor 2 kinase and to its phosphorylation at a novel site, serine 398 . The Journal of Biological Chemistry . 279 . 13 . 12220–31 . Mar 2004 . 14709557 . 10.1074/jbc.M309773200 . free .
• Browne GJ, Proud CG . A novel mTOR-regulated phosphorylation site in elongation factor 2 kinase modulates the activity of the kinase and its binding to calmodulin . Molecular and Cellular Biology . 24 . 7 . 2986–97 . Apr 2004 . 15024086 . 371112 . 10.1128/MCB.24.7.2986-2997.2004 .
• Brill LM, Salomon AR, Ficarro SB, Mukherji M, Stettler-Gill M, Peters EC . Robust phosphoproteomic profiling of tyrosine phosphorylation sites from human T cells using immobilized metal affinity chromatography and tandem mass spectrometry . Analytical Chemistry . 76 . 10 . 2763–72 . May 2004 . 15144186 . 10.1021/ac035352d .
• Li X, Alafuzoff I, Soininen H, Winblad B, Pei JJ . Levels of mTOR and its downstream targets 4E-BP1, eEF2, and eEF2 kinase in relationships with tau in Alzheimer's disease brain . The FEBS Journal . 272 . 16 . 4211–20 . Aug 2005 . 16098202 . 10.1111/j.1742-4658.2005.04833.x . 43085490 .
• Kimura K, Wakamatsu A, Suzuki Y, Ota T, Nishikawa T, Yamashita R, Yamamoto J, Sekine M, Tsuritani K, Wakaguri H, Ishii S, Sugiyama T, Saito K, Isono Y, Irie R, Kushida N, Yoneyama T, Otsuka R, Kanda K, Yokoi T, Kondo H, Wagatsuma M, Murakawa K, Ishida S, Ishibashi T, Takahashi-Fujii A, Tanase T, Nagai K, Kikuchi H, Nakai K, Isogai T, Sugano S . Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes . Genome Research . 16 . 1 . 55–65 . Jan 2006 . 16344560 . 1356129 . 10.1101/gr.4039406 .
• Hait WN, Wu H, Jin S, Yang JM . Elongation factor-2 kinase: its role in protein synthesis and autophagy . Autophagy . 2 . 4 . 294–6 . 2007 . 16921268 . 10.4161/auto.2857 . free .
• Beausoleil SA, Villén J, Gerber SA, Rush J, Gygi SP . A probability-based approach for high-throughput protein phosphorylation analysis and site localization . Nature Biotechnology . 24 . 10 . 1285–92 . Oct 2006 . 16964243 . 10.1038/nbt1240 . 14294292 .
• Olsen JV, Blagoev B, Gnad F, Macek B, Kumar C, Mortensen P, Mann M . Global, in vivo, and site-specific phosphorylation dynamics in signaling networks . Cell . 127 . 3 . 635–48 . Nov 2006 . 17081983 . 10.1016/j.cell.2006.09.026 . 7827573 . free .

Notes and References

1. Web site: EEF2K Gene (Protein Coding). GeneCards. Weizmann Institute of Science. 4 November 2015. Aliases for EEF2K Gene
   Eukaryotic Elongation Factor 2 Kinase
   Calcium/Calmodulin-Dependent Eukaryotic Elongation Factor 2 Kinase
   EEF-2 Kinase
   EC 2.7.11.20
   EEF-2K
   Calcium/Calmodulin-Dependent Eukaryotic Elongation Factor-2 Kinase
   Calmodulin-Dependent Protein Kinase III.
2. Ryazanov AG, Ward MD, Mendola CE, Pavur KS, Dorovkov MV, Wiedmann M, Erdjument-Bromage H, Tempst P, Parmer TG, Prostko CR, Germino FJ, Hait WN . Identification of a new class of protein kinases represented by eukaryotic elongation factor-2 kinase . Proceedings of the National Academy of Sciences of the United States of America . 94 . 10 . 4884–9 . May 1997 . 9144159 . 24600 . 10.1073/pnas.94.10.4884 . 1997PNAS...94.4884R . free .
3. Ryazanov AG, Spirin AS . Phosphorylation of elongation factor 2: a key mechanism regulating gene expression in vertebrates . The New Biologist . 2 . 10 . 843–50 . Oct 1990 . 1964087 .
4. Tavares CD, O'Brien JP, Abramczyk O, Devkota AK, Shores KS, Ferguson SB, Kaoud TS, Warthaka M, Marshall KD, Keller KM, Zhang Y, Brodbelt JS, Ozpolat B, Dalby KN . Calcium/calmodulin stimulates the autophosphorylation of elongation factor 2 kinase on Thr-348 and Ser-500 to regulate its activity and calcium dependence . Biochemistry . 51 . 11 . 2232–45 . Mar 2012 . 22329831 . 10.1021/bi201788e . 3401519.
5. Tavares CD, Ferguson SB, Giles DH, Wang Q, Wellmann RM, O'Brien JP, Warthaka M, Brodbelt JS, Ren P, Dalby KN . The molecular mechanism of eukaryotic elongation factor 2 kinase activation . The Journal of Biological Chemistry . 289 . 34 . 23901–16 . Aug 2014 . 25012662 . 10.1074/jbc.m114.577148 . 4156036. free .
6. Web site: Entrez Gene: EEF2K eukaryotic elongation factor-2 kinase.
7. Leprivier G, Remke M, Rotblat B, Dubuc A, Mateo AR, Kool M, Agnihotri S, El-Naggar A, Yu B, Somasekharan SP, Faubert B, Bridon G, Tognon CE, Mathers J, Thomas R, Li A, Barokas A, Kwok B, Bowden M, Smith S, Wu X, Korshunov A, Hielscher T, Northcott PA, Galpin JD, Ahern CA, Wang Y, McCabe MG, Collins VP, Jones RG, Pollak M, Delattre O, Gleave ME, Jan E, Pfister SM, Proud CG, Derry WB, Taylor MD, Sorensen PH . The eEF2 kinase confers resistance to nutrient deprivation by blocking translation elongation . Cell . 153 . 5 . 1064–79 . May 2013 . 23706743 . 10.1016/j.cell.2013.04.055 . 4395874.
8. Monteggia LM, Gideons E, Kavalali ET . The role of eukaryotic elongation factor 2 kinase in rapid antidepressant action of ketamine . Biological Psychiatry . 73 . 12 . 1199–203 . Jun 2013 . 23062356 . 10.1016/j.biopsych.2012.09.006 . 3574622.
9. Tekedereli I, Alpay SN, Tavares CD, Cobanoglu ZE, Kaoud TS, Sahin I, Sood AK, Lopez-Berestein G, Dalby KN, Ozpolat B . Targeted silencing of elongation factor 2 kinase suppresses growth and sensitizes tumors to doxorubicin in an orthotopic model of breast cancer. . PLOS ONE . 7 . 7 . e41171 . Mar 20, 2012 . 22911754 . 10.1371/journal.pone.0041171 . 3401164 . 2012PLoSO...741171T . free .
10. Jan 22, 2014. Targeting elongation factor-2 kinase (eEF-2K) induces apoptosis in human pancreatic cancer cells.. Apoptosis. 19. 1. 241–58. 10.1007/s10495-013-0927-2. 24193916. Ashour AA, Abdel-Aziz AA, Mansour AM, Alpay SN, Huo L, Ozpolat B. 16393302.