西亚试剂：Cell-cycle-regulated activation of Akt kinase by phosphoryl

Pengda Liu, Michael Begley, Wojciech Michowski, Hiroyuki Inuzuka, Miriam Ginzberg,Daming Gao, Peiling Tsou, Wenjian Gan, Antonella Papa, Byeong Mo Kim, Lixin Wan, Amrik Singh, Bo Zhai, Min Yuan, Zhiwei Wang, Steven P. Gygi, Tae Ho Lee, Kun-Ping Lu, Alex Toker, Pier Paolo Pandolfi, John M. Asara, Marc W. Kirschner, Piotr Sicinski, Lewis Cantley& Wenyi Wei

Akt, also known as protein kinase B, plays key roles in cell proliferation, survival and me-tabolism. Akt hyperactivation contributes to many pathophysiological conditions, including human cancers, and is closely associated with poor prognosis and chemo- or radiotherapeutic resistance. Phosphorylation of Akt at S473 (ref. 5) and T308 (ref. 6) activates Akt. However, it remains unclear whether further mechanisms account for full Akt activation, and whether Akt hyperactivation is 1inked to misregulated cell cycle progression, another cancer hallmark7. Here we report that Akt activity fluctuates across the cell cycle, mirroring cyclin A expressi0n. Mechanistically, phosphorylation of S477 and T479 at the Akt extreme carboxy terminus by cyclin-dependent kinase 2 (Cdk2)/cyclin A or mTORC2, under distinct physiological conditions, promotes Akt activation through facilitating, or functionally compensating for, S473 phosphorylation. Furthermore, deletion of the cyclin A2 allele in the mouse olfactory bulb leads to reduced S477/T479 phosphorylation and elevated cellular apoptosis. Notably, cyclin A2-deletion-induced cellular apoptosis in mouse embryonic stem cells is partly rescued by S477D/T479E-Akt1, supporting a physiological role for cyclin A2 in governing Akt activation. Together, the results of our study show Akt S477/T479 phosphorylation to be an essential layer of the Akt activation mechanism to regulate its physiological functions, thereby providing a new mechanistic 1ink between aberrant cell cycle progression and Akt hyperactivation in cancer.

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