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Genes 2018, 9(9), 450; https://doi.org/10.3390/genes9090450

Phosphorylation-Dependent Inhibition of Akt1

1
Department of Biochemistry, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
2
Department of Chemistry, Faculty of Science, The University of Western Ontario, London, ON N6A 5C1, Canada
*
Author to whom correspondence should be addressed.
Received: 20 July 2018 / Revised: 10 August 2018 / Accepted: 10 August 2018 / Published: 7 September 2018
(This article belongs to the Special Issue Synthetic DNA and RNA Programming)
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Abstract

Protein kinase B (Akt1) is a proto-oncogene that is overactive in most cancers. Akt1 activation requires phosphorylation at Thr308; phosphorylation at Ser473 further enhances catalytic activity. Akt1 activity is also regulated via interactions between the kinase domain and the N-terminal auto-inhibitory pleckstrin homology (PH) domain. As it was previously difficult to produce Akt1 in site-specific phosphorylated forms, the contribution of each activating phosphorylation site to auto-inhibition was unknown. Using a combination of genetic code expansion and in vivo enzymatic phosphorylation, we produced Akt1 variants containing programmed phosphorylation to probe the interplay between Akt1 phosphorylation status and the auto-inhibitory function of the PH domain. Deletion of the PH domain increased the enzyme activity for all three phosphorylated Akt1 variants. For the doubly phosphorylated enzyme, deletion of the PH domain relieved auto-inhibition by 295-fold. We next found that phosphorylation at Ser473 provided resistance to chemical inhibition by Akti-1/2 inhibitor VIII. The Akti-1/2 inhibitor was most effective against pAkt1T308 and showed four-fold decreased potency with Akt1 variants phosphorylated at Ser473. The data highlight the need to design more potent Akt1 inhibitors that are effective against the doubly phosphorylated and most pathogenic form of Akt1. View Full-Text
Keywords: genetic code expansion; protein kinase B; phosphoinositide dependent kinase 1; phosphoseryl-tRNA synthetase; tRNASep genetic code expansion; protein kinase B; phosphoinositide dependent kinase 1; phosphoseryl-tRNA synthetase; tRNASep
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Balasuriya, N.; McKenna, M.; Liu, X.; Li, S.S.C.; O’Donoghue, P. Phosphorylation-Dependent Inhibition of Akt1. Genes 2018, 9, 450.

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