Many bacteria attack cells using pore-forming toxins. An efflux of K+ through these pores activates lipid synthesis that helps the cells survive, say Laure Gurcel, F. Gisou van der Goot (University of Geneva, Switzerland), and colleagues.
The group's first clue was that treatment of cells with aerolysin, a pore-forming protein from Aeromonas, triggered processing of SREBP-2. Processed SREBP-2 enters the nucleus and induces transcription; its target genes turn on cholesterol and fatty acid biosynthesis.
After testing many candidates for the source of the signal, the researchers added aerolysin in the presence of high K+ medium. With K+ efflux prevented, the cells did not activate SREBP-2 and died in droves. A K+ ionophore, by contrast, was sufficient to induce SREBP-2 activation.
The pathway that emerged leads from K+ entry to assembly of two so-called inflammasome complexes. These allow autoproteolysis of...
