Overexpression of the truncated form of Livin reveals a complex interaction with caspase-3.

Disruption in apoptosis are involved in cancer development and progression. Livin-β, has been identified as a critical modulator for cell death in several tumor cell lines. It was demonstrated that a truncated fragment of Livin-β (tLivin) without its N-terminal 52 amino acids is produced in cells through protein cleavage. However, the biological consequence of the cleavage remains largely ignored. In the present study, we report that tLivin exerted a pro-apoptotic effect on cells. The subcellular localization of tLivin was mainly restricted to the cytoplasm. To explore the underlying mechanism, we observed an elevated caspase-3 activity which may account for the apoptosis. Furthermore, we observed that tLivin was further cleaved into a smaller fragment in cells. This second cleavage was possibly related to activated caspase-3. The resulted C-terminal fragment (livC) was an anti-apoptotic factor. Our study may help to deepen our understanding of the role of Livin in the regulation of cell death.