The Bacillus subtilis YufLM two-component system regulates the expression of the malate transporters MaeN (YufR) and YflS, and is essential for utilization of malate in minimal medium.

The Gram-positive bacterium Bacillus subtilis has a complete set of enzymes for the tricarboxylic acid (TCA) cycle and can grow aerobically using most of the TCA cycle intermediates (malate, fumarate, succinate and citrate) as a sole carbon source. The B. subtilis genome sequence contains three paralogous two-component regulatory systems, CitST, DctSR and YufLM. CitST and DctSR activate the expression of a transporter of the Mg(2+)-citrate complex (CitM) and a fumarate and succinate transporter (DctP), respectively. These findings prompted an investigation of whether the YufL sensor and its cognate regulator, YufM, play a role in malate uptake. This paper reports that the YufM regulator shows in vitro binding to the promoter region of two malate transporter genes, maeN and yflS, and is responsible for inducing their expression in vivo. It was also found that inactivation of the yufM or maeN genes resulted in bacteria that could not grow in a minimal salts medium containing malate as a sole carbon source, indicating that the induction of the MaeN transporter by the YufM regulator is essential for the utilization of malate as a carbon source. Inactivation of the yufL gene resulted in the constitutive expression of MaeN. This expression was suppressed by reintroduction of the kinase domain of YufL, indicating that the YufL sensor is required for proper signal detection and signalling specificity. The authors propose that a phosphatase activity of YufL plays an important role in the YufLM two-component regulatory system. The studies reported here have revealed that members of a set of paralogous two-component regulatory systems in B. subtilis, CitST, DctSR and YufLM, are involved in a related function--uptake (and metabolism) of the TCA cycle intermediates--but with distinct substrate specificities.

Inhibition of induction of myofibroblasts by interferon gamma in a human fibroblast cell line.

Interferon gamma (IFNgamma) has been reported as a possible therapeutic agent for contractile diseases in clinical trials and in vitro studies. It is not yet clear, however, whether IFNgamma simply inhibits myofibroblast generation or downregulates alpha smooth muscle actin (alphaSMA) production in myofibroblasts. In this study, we attempted to clarify how IFNgamma acts in the generation of myofibroblasts, and the production of alphaSMA by myofibroblasts, using immunofluorescence staining, cell capture enzyme immunoassay (CC-EIA) and the reverse transcription polymerase chain reaction (RT-PCR) for alphaSMA. We examined whether IFNgamma could block the TGFbeta1-promoted changes in myofibroblasts or the generation of myofibroblasts by TGFbeta1. IFNgamma strongly blocked the generation of myofibroblasts and moderately inhibited the production of alphaSMA in TGFbeta1-promoted myofibrobasts. These findings indicate that IFNgamma may be effective in the early stage of contractile diseases to prevent the progression of contractile lesions.