Activators of Procaspase-7

University Of California, San Francisco, San Francisco CA

Investigators

Abstract

DESCRIPTION (provided by applicant): Our primary objective is to develop a high throughput screening assay focused on the discovery of novel small molecules that promote activation of procaspase-7. Programmed cell death, or apoptosis, is used by multicellular organisms to eradicate physiologically- divergent cells that threaten development, homeostasis and overall survival. Disruption of the apoptotic cycle can lead to a number of life-threatening human disorders including cancer, immunodeficiency, autoimmune and neurodegenerative diseases. Apoptosis is initiated by a variety of pathways which incorporate a family of cysteine proteases, known as caspases, that cleave specific proteins that drive cell death. Apoptotic caspases are divided into "initiators" and "effectors" with the initiator caspases -8 and -9 converging to activate effector caspases -3 and -7. Effector caspases -3 and -7 then execute the final steps of apoptosis by destroying actin, nuclear lamin and many anti-apoptotic regulatory proteins. Significantly, an allosteric cavity has recently been discovered at the homodimeric interface of these highly conserved caspases and small molecules targeted to this region have been shown to regulate caspase activity. Such compounds cause reversible rearrangements that mimic their procaspase antecedents. This discovery represents an exciting opportunity for the potential identification of small molecule agonists that promote activation of procaspases and, thus, stimulate cellular apoptosis independent of regulatory cleavage by upstream initiator caspases -8 and -9. The identification of lead compounds with drug-like properties that allosterically induce procaspase-7 activation would be a significant and novel advancement in cancer therapeutics. We aim to use HTS combinatorial library screening to identify lead compounds that target allosteric surface cavities of procaspase 7. Procaspase-7 will be expressed and purified and a high throughput procaspase-7 activation fluorescence assay will be developed in both 96-well and 384-well formats. Hits from the HTS screens will be analyzed for specificity, mode of binding and structure activity relationships and common structural features will be established. Structures of procaspase-7 in complex with promising molecules will be determined by x-ray crystallography. HTS hits will subsequently be optimized into drug leads. The identification of lead compounds with drug-like properties that allosterically induce procaspase-7 activation would be a significant and novel advancement in cancer therapeutics.