The Structural Determinants of PH Domain-Mediated Regulation of Akt Revealed by Segmental Labeling
- Harvard Medical School, Brigham and Women's Hospital, United States
- Harvard Medical School, Dana-Farber Cancer Institute, United States
- Harvard Medical School, United States
Abstract
Akt is a critical protein kinase that governs cancer cell growth and metabolism. Akt appears to be autoinhibited by an intramolecular interaction between its N-terminal pleckstrin homology (PH) domain and kinase domain, which is relieved by C-tail phosphorylation, but the precise molecular mechanisms remain elusive. Here we use a combination of protein semisynthesis, NMR, and enzymological analysis to characterize structural features of the PH domain in its autoinhibited and activated states. We find that Akt autoinhibition depends on the length/flexibility of the PH-kinase linker. We identify a role for a dynamic short segment in the PH domain that appears to regulate autoinhibition and PDK1-catalyzed phosphorylation of Thr308 in the activation loop. We determine that Akt allosteric inhibitor MK2206 drives distinct PH domain structural changes compared to baseline autoinhibited Akt. These results highlight how the conformational plasticity of Akt governs the delicate control of its catalytic properties.
Data availability
Source data: Enzyme kinetics, fluorescence binding data, western blots, SDSPAGE gels have been deposited in Dryad: http://dx.doi:10.5061/dryad.0p2ngf1xg
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The Structural Determinants of PH Domain-Mediated Regulation of Akt Revealed by Segmental LabelingDryad Digital Repository, doi:10.5061/dryad.0p2ngf1xg.
Article and author information
Author details
Funding
National Cancer Institute (CA74305)
- Philip A Cole
Claudia Adams Barr Program in Innovative Cancer Research
- Haribabu Arthanari
Austrian Science Fund (Schroedinger Fellowship)
- Andras Boeszoermenyi
American Heart Association (19POST34380800)
- Andras Boeszoermenyi
National Institutes of Health (EB002026)
- Haribabu Arthanari
Kwanjeong Educational Foundation (pre-doctoral fellowship)
- Hwan Bae
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Chu et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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The Structural Determinants of PH Domain-Mediated Regulation of Akt Revealed by Segmental Labeling
eLife 9:e59151.
https://doi.org/10.7554/eLife.59151
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Glutamine synthetases (GS) are central enzymes essential for the nitrogen metabolism across all domains of life. Consequently, they have been extensively studied for more than half a century. Based on the ATP-dependent ammonium assimilation generating glutamine, GS expression and activity are strictly regulated in all organisms. In the methanogenic archaeon Methanosarcina mazei, it has been shown that the metabolite 2-oxoglutarate (2-OG) directly induces the GS activity. Besides, modulation of the activity by interaction with small proteins (GlnK1 and sP26) has been reported. Here, we show that the strong activation of M. mazei GS (GlnA1) by 2-OG is based on the 2-OG dependent dodecamer assembly of GlnA1 by using mass photometry (MP) and single particle cryo-electron microscopy (cryo-EM) analysis of purified strep-tagged GlnA1. The dodecamer assembly from dimers occurred without any detectable intermediate oligomeric state and was not affected in the presence of GlnK1. The 2.39 Å cryo-EM structure of the dodecameric complex in the presence of 12.5 mM 2-OG demonstrated that 2-OG is binding between two monomers. Thereby, 2-OG appears to induce the dodecameric assembly in a cooperative way. Furthermore, the active site is primed by an allosteric interaction cascade caused by 2-OG-binding towards an adaption of an open active state conformation. In the presence of additional glutamine, strong feedback inhibition of GS activity was observed. Since glutamine dependent disassembly of the dodecamer was excluded by MP, feedback inhibition most likely relies on the binding of glutamine to the catalytic site. Based on our findings, we propose that under nitrogen limitation the induction of M. mazei GS into a catalytically active dodecamer is not affected by GlnK1 and crucially depends on the presence of 2-OG.
