Inhibitor of Apoptosis (IAP)-like Protein Lacks a Baculovirus IAP Repeat (BIR) Domain and Attenuates Cell Death in Plant and Animal Systems

• DOI: 10.1074/jbc.m111.262204
• Publication Date: 2011-09-17T03:43:22Z
• Authors: Woe Yeon Kim; Sun Yong Lee; Young Jun Jung; Ho Byoung Chae; Ganesh M. Nawkar; Mi Rim Shin; Sun Young Kim; Jin Ho Park; Chang Ho Kang; Yong Hun Chi; Il Pyung Ahn; Dae Jin Yun; Kyun Oh Lee; Young-Myeong Kim; Min Gab Kim; Sang Yeol Lee
• Keywords: 0303 health sciences; Base Sequence; Cell Death; Sequence Homology, Amino Acid; Caspase 3; Cell Survival; Molecular Sequence Data; Arabidopsis; Apoptosis; DNA; Plants, Genetically Modified; Fumonisins; Inhibitor of Apoptosis Proteins; Protein Structure, Tertiary; 03 medical and health sciences; Animals; Humans; Amino Acid Sequence; Baculoviridae; HeLa Cells; Plasmids; Subcellular Fractions

A novel Arabidopsis thaliana inhibitor of apoptosis was identified by sequence homology to other known inhibitor of apoptosis (IAP) proteins. Arabidopsis IAP-like protein (AtILP) contained a C-terminal RING finger domain but lacked a baculovirus IAP repeat (BIR) domain, which is essential for anti-apoptotic activity in other IAP family members. The expression of AtILP in HeLa cells conferred resistance against tumor necrosis factor (TNF)-α/ActD-induced apoptosis through the inactivation of caspase activity. In contrast to the C-terminal RING domain of AtILP, which did not inhibit the activity of caspase-3, the N-terminal region, despite displaying no homology to known BIR domains, potently inhibited the activity of caspase-3 in vitro and blocked TNF-α/ActD-induced apoptosis. The anti-apoptotic activity of the AtILP N-terminal domain observed in plants was reproduced in an animal system. Transgenic Arabidopsis lines overexpressing AtILP exhibited anti-apoptotic activity when challenged with the fungal toxin fumonisin B1, an agent that induces apoptosis-like cell death in plants. In AtIPL transgenic plants, suppression of cell death was accompanied by inhibition of caspase activation and DNA fragmentation. Overexpression of AtILP also attenuated effector protein-induced cell death and increased the growth of an avirulent bacterial pathogen. The current results demonstrated the existence of a novel plant IAP-like protein that prevents caspase activation in Arabidopsis and showed that a plant anti-apoptosis gene functions similarly in plant and animal systems.