Rapid and simple screening of the apoptotic compounds based on Hsp70 inhibition using luciferase as an intracellular reporter

HSP70 is a powerful antiapoptotic protein that can block the extrinsic and intrinsic pathways of apoptosis. The present study describes a rapid, sensitive, and inexpensive system using luciferase as a reporter for the functional analysis of apoptotic compounds. For this approach, the co-transformation of Escherichia coli cells was performed with two expression vectors containing Hsp70 and firefly luciferase. It was found that the luciferase inactivated by heat treatment (40-46 degrees C for 10 min) was approximately reactivated at room temperature and regained 70% of its initial activity before heat inactivation after 60 min. The results show that the reactivation of thermally inactivated luciferase was inhibited in living cells by treatment with VER-155008 and pifitrin-mu as Hsp70 inhibitors, with half-maximal inhibitory concentration of 124 and 384 mu M, respectively. The sensitivity of this method for detecting VER-155008 and pifitrin-mu was about 8 and 25 mu M, respectively. Also, this reporter system showed no response to doxorubicin and dactinomycin, which bind to DNA, and we used these anticancer compounds as control compounds. Therefore, for the first time, a rapid and simple real-time system using luciferase as a reporter is introduced for the screening of apoptosis-inducing compounds based on suppression of Hsp70 in E. coli cells.