Targeting chondroitin sulfate proteoglycan 4 (CSPG4) expression as a Clostridioides difficile therapeutic

Binding to host receptors is a fundamental step in the mechanisms of action for many bacterial toxins, particularly toxins produced by Clostridioides difficile. Blocking or otherwise abrogating toxin binding to receptors not only protects against cytotoxicity but can also in many cases totally prevents disease. In this work, we are investigating a new approach for preventing toxins from engaging cell surface receptors by targeting host signaling pathways that regulate the expression of toxin receptors. Targeting signaling pathways is central to the design of various cancer therapeutics but has not been as readily explored as a treatment strategy for bacterial pathogens. In these studies, we are pursuing this idea by identifying and investigating a host signaling pathway that regulates the C. difficile toxin receptor chondroitin sulfate proteoglycan 4 (CSPG4). As a key receptor for C. difficile toxins, CSPG4 is required for the manifestation of C. difficile disease and eliminating the expression prevents C. difficile disease. In our preliminary work, signaling networks regulating the expression of CSPG4 were identified utilizing a toxin-resistance system that discovered the Hippo pathway controls the expression of CSPG4. Our preliminary studies have demonstrated small molecule inhibitors of Hippo signaling down regulate CSPG4 in vitro and in vivo. Importantly, we were able to protect mice from C. difficile disease by inhibiting Hippo signaling during the primary phase of disease. Building directly from our initial work, Aim 1 will further explore the underlying mechanisms utilized by Hippo signaling to regulate CSPG4 in the presence of C. difficile toxins. Aim 2 will provide fundamental information about how CSPG4 expression patterns in the colon are connected to C. difficile pathogenesis. Aim 3 will assess the therapeutic effectiveness of targeting the Hippo-CSPG4 axis during various clinical manifestations of C. difficile disease. Collectively, these proposed studies will address a critical unmet need by targeting the Hippo-CSPG4 axis as a treatment for C. difficile and by advancing the paradigm of developing therapeutics based on signaling pathways regulating toxin receptors.