Caspases and cancer: Connections through circular dichroism spectroscopy

While excessive cell death inevitably leads to negative effects, the endurance of damaged cells in the presence of death signals can be equally detrimental to health. Apoptosis, or programmed cell death, is a highly regulated process in which cues from within or from outside a cell can trigger an irreversible sequence of signals that carry out cell destruction known as the apoptotic cascade. A group of enzymes called caspases play a vital role in this cascade with some participating as initiators and others acting as effectors of protein cleavage and intracellular breakdown. Although it is normal for the activity of caspases to be suppressed during a cell’s lifetime, continued suppression of apoptotic enzymes even in the presence of pro-apoptotic signals is one of the hallmarks of cancer cells. There is evidence that certain metal ions can bind and inhibit caspases, and fluctuations in intracellular Fe3+ concentrations during apoptosis raise the question whether this ion has a similar effect. In this study, plasmid DNA encoding caspase-7 was expressed in E. coli, and the resulting protein was purified using nickel affinity chromatography. The protein’s structure will be analyzed both on its own and in the presence of Fe3+ in order to determine whether interactions are present that may lead to caspase-7 inhibition. Structural changes will be monitored using circular dichroism spectroscopy. Further understanding of cationic interactions with caspases could answer many existing questions about apoptotic resistance in cells and perhaps even lead to the development of treatments for such conditions