Caspase-activated phosphoinositide binding by CNT-1 promotes apoptosis by inhibiting the AKT pathway.

Inactivation of cell-survival factors is a crucial step in apoptosis. The phosphoinositide 3-kinase (PI3K)-AKT signaling pathway promotes cell growth, proliferation and survival, and its deregulation causes cancer. How this pathway is suppressed to promote apoptosis is poorly understood. Here we report the identification of a CED-3 caspase substrate in Caenorhabditis elegans, CNT-1, that is cleaved during apoptosis to generate an N-terminal phosphoinositide-binding fragment (tCNT-1). tCNT-1 translocates from the cytoplasm to the plasma membrane and blocks AKT binding to phosphatidylinositol (3,4,5)-trisphosphate, thereby disabling AKT activation and its prosurvival activity. Our findings reveal a new mechanism that negatively regulates AKT cell signaling to promote apoptosis and that may restrict cell growth and proliferation in normal cells.

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