Selective Inhibition of Metacaspase 4 in Arabidopsis Thaliana  

Abstract: Metacaspases are a recently discovered family of cysteine-dependent proteases present in plants, fungi, and lower eukaryotes. They are believed to be involved in regulated cell death in non-metazoan cells, but little is known about their distinct functional properties. Metacaspases have been identified in various forms of protozoa that cause pathogen-induced diseases, which affect millions of people every year. Their biological function in protozoa and their absence in the human host make them an attractive drug target for treatment of such diseases. In this project, we have explored a potential hit towards metacaspase 4 in Arabidopsis Thaliana. The hit compound was successfully identified from high throughput screening, and an initial structure-activity relationship was established by testing a set of synthesized analogues towards the enzyme. The compounds were also tested against metacaspase 9 in Arabidopsis thaliana, where no inhibitory activity was observed. The active site is highly conserved between the different clades of metacaspases, and these results suggest that the hit compound interacts with an allosteric site on the target.   The results presented here provide important information on how selective regulation of metacaspases can be achieved by developing small chemical probes, targeting allosteric sites on the enzyme. Hopefully, this can be applied to other metacaspases systems to evaluate their biological function in protozoa.