Wurm Philipp, Tutz Sarah, Mutsam Beatrice, Vorkapic Dina, Heyne Barbara, Grabner Claudia, Kleewein Katharina, Halscheidt Anja, Schild Stefan, Reidl Joachim
University of Graz, Institute of Molecular Biosciences, Molecular Enzymology and Physiology, Humboldtstraße 50, A-8010 Graz, Austria.
University of Graz, Institute of Molecular Biosciences, Molecular Enzymology and Physiology, Humboldtstraße 50, A-8010 Graz, Austria; BioTechMed-Graz, Austria; NAWI Graz, Austria.
Int J Med Microbiol. 2017 Apr;307(3):154-165. doi: 10.1016/j.ijmm.2017.01.006. Epub 2017 Feb 7.
Vibrio cholerae can colonize the gastrointestinal track of humans and cause the disease cholera. During colonization, the alternative sigma factor, RpoS, controls a process known as "mucosal escape response," defining a specific spatial and temporal response and effecting chemotaxis and motility. In this report, the expression and proteolytic control of RpoS in V. cholerae was characterized. To date, aspects of proteolysis control, the involved components, and proteolysis regulation have not been addressed for RpoS in V. cholerae. Similar to Escherichia coli, we find that the RpoS protein is subjected to regulated intracellular proteolysis, which is mediated by homologues of the proteolysis-targeting factor RssB and the protease complex ClpXP. As demonstrated, RpoS expression transiently peaks after cells are shifted from rich to minimal growth medium. This peak level is dependent on (p)ppGpp-activated rpoS transcription and controlled RpoS proteolysis. The RpoS peak level also correlates with induction of a chemotaxis gene, encoding a methyl-accepting chemotaxis protein, earlier identified to belong to the mucosal escape response pathway. These results suggest that the RpoS expression peak is linked to (p)ppGpp alarmone increase, leading to enhanced motility and chemotaxis, and possibly contributing to the mucosal escape response.
霍乱弧菌可定殖于人类胃肠道并引发霍乱疾病。在定殖过程中，替代σ因子RpoS控制着一种被称为“黏膜逃逸反应”的过程，该过程定义了一种特定的时空反应，并影响趋化性和运动性。在本报告中，对霍乱弧菌中RpoS的表达及蛋白水解调控进行了表征。迄今为止，霍乱弧菌中RpoS的蛋白水解调控方面、涉及的组分以及蛋白水解调节尚未得到研究。与大肠杆菌相似，我们发现RpoS蛋白会受到细胞内调控性蛋白水解的作用，这一过程由蛋白水解靶向因子RssB的同源物和蛋白酶复合体ClpXP介导。如所证实的，当细胞从丰富培养基转移至基本培养基后，RpoS表达会短暂达到峰值。这一峰值水平依赖于（p）ppGpp激活的rpoS转录以及受调控的RpoS蛋白水解。RpoS峰值水平还与一个趋化性基因的诱导相关，该基因编码一种甲基接受趋化蛋白，此前已确定其属于黏膜逃逸反应途径。这些结果表明，RpoS表达峰值与（p）ppGpp警报素增加有关，导致运动性和趋化性增强，并可能对黏膜逃逸反应有贡献。
