POSTER NO: 205

Human Programmed cell death 5 (PDCD5) - an active caspase-3 binding protein and positive regulator for apoptosis

¹Xianting Li, ²Xiaoning Mo, ¹Donglan Xia, ¹Ying Wang, ¹Yanan Liu, ²Quansheng Song, ²Yingmei Zhang, ¹Dalong Ma
¹Lab of Medical Immunology, School of Basic Medical Science, Peking University, Xueyuan Road 38, Beijing 100083, P.R. China, ²Peking University Center for Human Disease Genomics and Lab of Medical Immunology, School of Basic Medical Science, Peking University, Xueyuan Road 38, Beijing 100083, P.R. China

Programmed cell death5 (PDCD5), formerly named TF-1 cell apoptosis related gene-19 (TFAR19), is an apoptosis-related gene cloned in our laboratory (Biochem Biophy Res Comm 1999,254:203-210). It encodes a protein that shares significant homology to the corresponding proteins of species ranging from yeast to mice. Previous studies have shown that PDCD5 can facilitate apoptosis in many cell lines and the expression of PDCD5 is increased upon induction of apoptosis; in the process of apoptosis, PDCD5 redistributed between the cytosol and nucleolus (FEBS letter, 2001, 509(2)191-196 ). However, the mechanism of PDCD5 facilitating apoptosis is unclear. Our previous studies have indicated that antisense inhibition of PDCD5 could attenuate the activtity of caspase-3. Here we construct five deletants of PDCD5 according the exon sequences, and expressed them in E.coli as GST-fusion protein. The pull-down assays show that GST-wtPDCD5 can interact with active caspase-3 and this interaction was not affected by the specific inhibitor(Ac-DEVD-CHO) of caspase-3. Using ELISA method we found that the exon-6 (acidic oligopeptide) of PDCD5 enhance the interaction of PDCD5 and active caspase-3. Exon3-6 and wtPDCD5 recombinant proteins can promote apoptosis of HL-60 cells and enhance caspase-3 activity. In conclusion, our results indicate that PDCD5 is an active caspase-3 binding protein and the binding site is out of the enzyme activity core, the exon-6 may be an important regulator of caspase-3.