High-throughput, cell-based screens to identify small-molecule inhibitors of ricin toxin and related category b ribosome inactivating proteins (RIPs).

Ricin is a member of the ubiquitous ribosome-inactivating protein (RIP) family of toxins. The Centers for Disease Control and Prevention (CDC) classify ricin and related toxins as Category B biothreat agents. There are currently no antidotes or therapeutics to counteract RIPs in humans. The discovery of effective small-molecule inhibitors of RIPs is increasingly possible, however, due to the availability and accessibility of diverse small-molecule chemical libraries coupled with robust robotics and automated screening methodologies. In this article, we describe a cell-based, high-throughput screening strategy and secondary assays that we have successfully used to identify compounds that target ricin toxin's enzymatic activity and intracellular trafficking, as well as stress-activated signaling pathways associated with cell death. The methods described in the protocol are amenable to the other RIPs.