IkappaB kinase epsilon and TANK-binding kinase 1 activate AKT by direct phosphorylation.

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Citation

Xie X, Zhang D, Zhao B, Lu MK, You M, Condorelli G, Wang CY, Guan KL

IkappaB kinase epsilon and TANK-binding kinase 1 activate AKT by direct phosphorylation.

Proc Natl Acad Sci U S A. 2011 Apr 19;108(16):6474-9. doi: 10.1073/pnas.1016132108. Epub 2011 Apr 4.

PubMed ID
21464307 [ View in PubMed
]
Abstract

AKT activation requires phosphorylation of the activation loop (T308) by 3-phosphoinositide-dependent protein kinase 1 (PDK1) and the hydrophobic motif (S473) by the mammalian target of rapamycin complex 2 (mTORC2). We recently observed that phosphorylation of the AKT hydrophobic motif was dramatically elevated, rather than decreased, in mTOR knockout heart tissues, indicating the existence of other kinase(s) contributing to AKT phosphorylation. Here we show that the atypical IkappaB kinase epsilon and TANK-binding kinase 1 (IKKepsilon/TBK1) phosphorylate AKT on both the hydrophobic motif and the activation loop in a manner dependent on PI3K signaling. This dual phosphorylation results in a robust AKT activation in vitro. Consistently, we found that growth factors can induce AKT (S473) phosphorylation in Rictor(-/-) cells, and this effect is insensitive to mTOR inhibitor Torin1. In IKKepsilon/TBK1 double-knockout cells, AKT activation by growth factors is compromised. We also observed that TBK1 expression is elevated in the mTOR knockout heart tissues, and that TBK1 is required for Ras-induced mouse embryonic fibroblast transformation. Our observations suggest a physiological function of IKKepsilon/TBK1 in AKT regulation and a possible mechanism of IKKepsilon/TBK1 in oncogenesis by activating AKT.

DrugBank Data that Cites this Article

Polypeptides
NameUniProt ID
RAC-alpha serine/threonine-protein kinaseP31749Details
Serine/threonine-protein kinase TBK1Q9UHD2Details
Inhibitor of nuclear factor kappa-B kinase subunit epsilonQ14164Details