Complex phosphorelay events within the Chp chemosensory system of Pseudomonas aeruginosa fine-tune cyclic AMP production and twitching motility (2016)

Undergraduates: Boya Wang, Ruth Silversmith PhD, Matthew C Wolfgang PhD

Faculty Advisor: Matthew Wolfgang
Department: Chemistry

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The Chp chemosensory system plays a central role in detecting host signals and activating virulence gene expression, allowing P. aeruginosa to cause a wide array of diseases. The Chp system controls intracellular cyclic AMP (cAMP) and type IV pilus mediated surface motility (twitching motility). The Chp chemosensory system contains a hybrid ChpA kinase, a serine-containing phosphotransfer domain, a threonine-containing phosphotransfer domain, six histidine-containing phosphotransfer domains, and a CheY-like receiver domain. We hypothesized that multiple domains may be necessary to fine-tune signal transduction for twitching motility and/or intracellular cAMP levels. Point mutants were generated in each of the phosphorylatable Hpt domains and the CheY-like receiver domain and evaluated the impact on cAMP signaling and twitching motility. To assess cAMP signaling, we used an artificial transcriptional reporter system that reflects intracellular cAMP levels. Western blot analysis was used to confirm wild type expression level of the mutant proteins. We are currently testing the impact of single and combination mutations. Loss of the CheY-like receiver domain significantly decreased twitching motility and increased cAMP production. Based on these results, we propose that the CheY-like receiver domain functions as a phosphate sink, thus preventing ChpA from activating downstream pathways until an appropriate signal threshold is achieved.