RESUMEN
Extracytoplasmic function (ECF) σ factors are a diverse family of alternative σ factors that allow bacteria to sense and respond to changes in the environment. σV is an ECF σ factor found primarily in low-GC Gram-positive bacteria and is required for lysozyme resistance in several opportunistic pathogens. In the absence of lysozyme, σV is inhibited by the anti-σ factor RsiV. In response to lysozyme, RsiV is degraded via the process of regulated intramembrane proteolysis (RIP). RIP is initiated by cleavage of RsiV at site 1, which allows the intramembrane protease RasP to cleave RsiV within the transmembrane domain at site 2 and leads to activation of σV Previous work suggested that RsiV is cleaved by signal peptidase at site 1. Here we demonstrate in vitro that signal peptidase is sufficient for cleavage of RsiV only in the presence of lysozyme and provide evidence that multiple Bacillus subtilis signal peptidases can cleave RsiV in vitro This cleavage is dependent upon the concentration of lysozyme, consistent with previous work that showed that binding to RsiV was required for σV activation. We also show that signal peptidase activity is required for site 1 cleavage of RsiV in vivo Thus, we demonstrate that signal peptidase is the site 1 protease for RsiV.IMPORTANCE Extracytoplasmic function (ECF) σ factors are a diverse family of alternative σ factors that respond to extracellular signals. The ECF σ factor σV is present in many low-GC Gram-positive bacteria and induces resistance to lysozyme, a component of the innate immune system. The anti-σ factor RsiV inhibits σV activity in the absence of lysozyme. Lysozyme binds RsiV, which initiates a proteolytic cascade leading to destruction of RsiV and activation of σV This proteolytic cascade is initiated by signal peptidase, a component of the general secretory system. We show that signal peptidase is necessary and sufficient for cleavage of RsiV at site 1 in the presence of lysozyme. This report describes a role for signal peptidase in controlling gene expression.
Asunto(s)
Bacillus subtilis/enzimología , Proteínas Bacterianas/metabolismo , Proteínas de la Membrana/metabolismo , Muramidasa/metabolismo , Serina Endopeptidasas/metabolismo , Factor sigma/metabolismo , Transducción de Señal , Bacillus subtilis/genética , Bacillus subtilis/fisiología , Proteínas Bacterianas/genética , Regulación Bacteriana de la Expresión Génica , Proteínas de la Membrana/genética , Muramidasa/genética , Dominios Proteicos , Proteolisis , Serina Endopeptidasas/genética , Factor sigma/genética , Estrés FisiológicoRESUMEN
Risperidone is a second-generation antipsychotic that causes weight gain. We hypothesized that risperidone-induced shifts in the gut microbiome are mechanistically involved in its metabolic consequences. Wild-type female C57BL/6J mice treated with risperidone (80 µg/day) exhibited significant excess weight gain, due to reduced energy expenditure, which correlated with an altered gut microbiome. Fecal transplant from risperidone-treated mice caused a 16% reduction in total resting metabolic rate in naïve recipients, attributable to suppression of non-aerobic metabolism. Risperidone inhibited growth of cultured fecal bacteria grown anaerobically more than those grown aerobically. Finally, transplant of the fecal phage fraction from risperidone-treated mice was sufficient to cause excess weight gain in naïve recipients, again through reduced energy expenditure. Collectively, these data highlight a major role for the gut microbiome in weight gain following chronic use of risperidone, and specifically implicates the modulation of non-aerobic resting metabolism in this mechanism.
