Abstract
Akt is a critical protein kinase that drives cancer proliferation, modulates metabolism, and is activated by C-terminal phosphorylation. The current structural model for Akt activation by C-terminal phosphorylation has centered on intramolecular interactions between the C-terminal tail and the N lobe of the kinase domain. Here, we employ expressed protein ligation to produce site-specifically phosphorylated forms of purified Akt1 that are well suited for mechanistic analysis. Using biochemical, crystallographic, and cellular approaches, we determine that pSer473-Akt activation is driven by an intramolecular interaction between the C-tail and the pleckstrin homology (PH)-kinase domain linker that relieves PH domain-mediated Akt1 autoinhibition. Moreover, dual phosphorylation at Ser477/Thr479 activates Akt1 through a different allosteric mechanism via an apparent activation loop interaction that reduces autoinhibition by the PH domain and weakens PIP3 affinity. These results provide a new framework for understanding how Akt is controlled in cell signaling and suggest distinct functions for differentially modified Akt forms. Dissecting the molecular interactions leading to Akt activation points to a chain of events distinct from existing models.
Original language | English (US) |
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Pages (from-to) | 897-907.e14 |
Journal | Cell |
Volume | 174 |
Issue number | 4 |
DOIs | |
State | Published - Aug 9 2018 |
Keywords
- X-ray crystal structure
- bisubstrate analog
- expressed protein ligation
- kinase
- mass spectrometry
- peptide
- phosphorylation
- photocrosslinking
ASJC Scopus subject areas
- General Biochemistry, Genetics and Molecular Biology