Adherent state apoptosis assay (ASA): a fast and reliable method to detect apoptosis in adherent cells
Apoptosis is a tightly controlled biochemical process for cell death. Although the induction of apoptosis is an important mechanism for the screening of many valuable products such as drugs, due to the false signals that usually occur during the isolation of cells from the surface of the culture plate, techniques have limitations in measuring apoptosis in adherent cells. In this study, we investigated the use of RLuc/Annexin V, a probe obtained by the fusion of Renilla luciferase (RLuc) with Annexin V and bound to phosphatidylserine (PS) on the surface of suspended apoptotic cells, as a potentially luminescent probe to assay apoptosis in adherent cells such as Chinese Hamster Ovary (CHO) cells. The probe was overexpressed in Escherichia coli BL21 (DE3) and purified by immobilized metal ion chromatography. The probe assayed for detection of apoptosis in CHO cells. The results show that RLuc/Annexin V binds to the CHO cells with no additional treatment for cell suspension, and the signal of RLuc can be detected by a luminometer. The new assay based on RLuc/Annexin V was named as adherent state apoptosis assay (ASA). This may be a new method for studying apoptosis in adherent cells in a rapid, reliable, and non-invasive way.