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Cleavage and inactivation of antiapoptotic Akt/PKB by caspases during apoptosis

2000; Wiley; Volume: 182; Issue: 2 Linguagem: Inglês

10.1002/(sici)1097-4652(200002)182

1097-4652

Susumu Rokudai, Naoya Fujita, Yuichi Hashimoto, Takashi Tsuruo,

Cancer Mechanisms and Therapy

The oncogene Akt/PKB/RAC-PK is a serine/threonine kinase that mediates survival signals and has protective effects against apoptosis induced by a variety of stimuli. The kinase activity of Akt has been demonstrated to be critical in transmitting survival signals. We found that Akt protein was down-regulated during apoptosis. The down-regulation was blocked by a caspase inhibitor, indicating that Akt was cleaved by caspases during apoptosis. The Akt protein incubation with active caspases in vitro revealed that it was cleaved at three sites to produce 40- and 44-kDa fragments. The two cleavage sites were between the NH2-terminal pleckstrin homology domain (PH domain) and the kinase domain (TVAD108↓G and EEMD119↓F) and in the COOH-terminal regulatory domain (SETD434↓T). The loss of COOH-terminal domain of the Akt protein reduced its kinase activity and the overexpression of NH2-terminal and COOH-terminal–deleted Akt fragment increased the sensitivity to apoptosis-inducing stimuli. These results indicate that caspase-dependent cleavage of anti-apoptotic Akt turns off the survival signals, resulting in the acceleration of apoptotic cell death. J. Cell. Physiol. 182:290–296, 2000. © 2000 Wiley-Liss, Inc.