3 years ago

Repression of VvpM Protease Expression by Quorum Sensing and the cAMP-CRP Complex in Vibrio vulnificus.

Mi-Ae Lee, Jeong-A Kim, Kyu-Ho Lee, You-Chul Jung, Bo-Ram Jang
Septicemia-causing Vibrio vulnificus produces at least three exoproteases, VvpE, VvpS and VvpM, all of which participate in interactions with human cells. Expression of VvpE and VvpS is induced in the stationary phase by multiple transcription factors including Sigma S, SmcR, and cAMP-CRP complex. Distinct roles of VvpM, such as induction of apoptosis, lead us to hypothesize VvpM expression is different from that of the other exoproteases. Its transcription, which was found to be independent of Sigma S, is induced at the early exponential phase and then became negligible upon entry into the stationary phase. SmcR and CRP were studied regarding the control of vvpM expression. Transcription of vvpM was repressed by SmcR and cAMP-CRP complex individually, which specifically bound to the regions -2 to +20 and +6 to +27, respectively, relative to the vvpM transcription initiation site. Derepression of vvpM gene expression was 10- to 40-fold greater in a smcR/crp double mutant relative to the single-gene mutants. Therefore, these results show that the expression of V. vulnificus exoproteases is differentially regulated, and this way, distinct proteases can engage in specific interactions with a host.IMPORTANCE An opportunistic human pathogen, Vibrio vulnificus produces multiple extracellular proteases that are involved in diverse interactions with a host. The total exoproteolytic activity is mainly detected in the supernatants of the high cell-density cultures. However, some proteolytic activity derived from a metalloprotease VvpM was present in the supernatants of the low cell-density cultures sampled at the early growth period. In this study, we present the regulatory mechanism for VvpM expression via repression by at least two transcription factors. This type of transcriptional regulation is exactly the opposite of those for expression of the other V. vulnificus exoproteases. Differential regulation of each exoprotease production then facilitate the pathogen's participation in the distinct interactions with a host.

Publisher URL: http://doi.org/10.1128/JB.00526-17

DOI: 10.1128/JB.00526-17

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