Acetylation of virulence factor regulatory proteins in V. cholerae

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Abstract The metabolism of pathogenic microorganisms has to be flexible and the efficient replication of pathogenic bacteria in the host depends on an active adaptation process. Vibrio cholerae is exposed to a variety of environments within the human host and eventually has to adapt to the nutrients available at its preferred infection site, the small intestine. The small intestine is the part of the gastrointestinal tract where the majority of digestion and absorption of food takes place, thus providing a variety of nutrients for the bacteria. As V. cholerae start to cause the profuse diarrhea that is the hallmark of the disease, the bacteria have to once again adapt to the resulting changes in nutrient availability to continue the infection process. It can therefore be expected that the metabolic status in V. cholerae changes substantially during the course of infection and that changes in metabolism are coordinated with virulence gene expression. Although a link between the metabolic status and virulence factor expression has been well described in several pathogens, it has not been investigated in detail in V. cholerae. Our preliminary results suggest that different availability of certain carbon sources that have relevance to in vivo conditions affect virulence gene expression in V. cholerae. Moreover, we found that mutations in membrane respiration as well as central metabolism genes, such as enzymes involved in the TCA cycle, affect virulence factor expression in V. cholerae. Based on our observations with defined mutants in the PTA-ACK pathway we concluded that acetyl-CoA (acCoA), but not acetyl-phosphate, plays a role in this signal transduction. We hypothesize that this link between metabolism and virulence gene regulation in V. cholerae occurs via post-translational protein modification, specifically by lysine acetylation of key virulence regulatory proteins. Importantly, a recent study of the global acetylome of V. cholerae revealed lysine acetylation of several important virulence regulatory proteins, including TcpP, AphB, and PhoB. By combining modern mass spectrometry analyses with genetic and biochemical analyses we expect to better understand the mechanism by which acCoA affects virulence factor transcription. We will also examine the roles of putative V. cholerae acetyltransferase genes in virulence factor modification as well as determine additional overall protein acetylation patters (acetylomes). Thus, our study has the potential to, for the first time, demonstrate a role of lysine acetylation in V. cholerae virulence factor regulation and will further establish the importance of central metabolism in the pathogenesis of this organism. Overall, we expect to gain insights into the metabolic pathways of this organism per se and its relation to virulence as an important aspect of host- pathogen interaction. Ultimately, this information could lead to novel intervention strategies aimed at modulating the interplay of central metabolites and virulence factor expression, not only for V. cholerae but potentially other pathogens.