Bacterial Cholesterol-Dependent Cytolysins in Inflammasome Activation

PROJECT SUMMARY Bacterial cholesterol-dependent cytolysins (CDCs) constitute the largest group of pore-forming toxins and serve as critical virulence factors for a wide variety of pathogenic bacteria. A number of CDCs are known to activate the NLRP3 inflammasome, a multiprotein innate immune signaling complex responsible for induction of proinflammatory cytokines (e.g., IL-1β and IL-18) and the proinflammatory cell death pyroptosis. Inhibition of NLRP3 inflammasome has been shown to significantly affect bacterial dissemination and pathogenesis. However, the detailed molecular and cellular mechanism underlying CDC-mediated inflammasome activation has not been fully characterized. In this proposal, we propose that CDCs can be grouped into two types based on whether they can directly remodel host organelle to stimulate the NLRP3 inflammasome signaling. This helps the host organisms clear invading bacteria, although excessive inflammation may also result in pathogenesis. Using a combination of SunTag live cell imaging, mass spectrometry analysis and infection models, we aim to define the motifs and host factors responsible for CDCs to reorganize host organelle and activate the NLRP3 inflammasome. We will also determine and characterize the abilities of Type II CDCs to escape the inflammasome activation via inhibition of host organelle remodeling. Our proposed studies will help define this host organelle remodeling activity of bacterial CDCs as potential broad-spectrum therapeutic targets to mitigate a wide range of infectious diseases.