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Inflammatory Pores

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Science  06 Oct 2006:
Vol. 314, Issue 5796, pp. 21
DOI: 10.1126/science.314.5796.21c

As part of the process of infection, pathogenic microbes secrete protein toxins, such as aerolysin, that form pores in the target cell's membrane. Gurcel et al. show that exposure of mammalian cells to aerolysin increased the activity of the transcription factor SREBP-2 (sterol response element-binding protein-2), as assessed by a selective increase in gene expression and an increase in total cellular cholesterol as a consequence of both increased biosynthesis and uptake (the low-density lipoprotein receptor is encoded by a SREBP-responsive gene). In addition, exposure of cells to a K+-selective ionophore triggered SREBP-2 activation, and a decrease in intracellular K+ (caused by leakage through the pores) is known to activate the protease caspase 1 via the assembly of inflammasomes containing IPAF, an intracellular pattern recognition receptor. SREBP-2 was not cleaved directly by caspase 1; instead, caspase 1 activated the SREBP-activating pathway that involves SCAP (an escort protein) and S1P and S2P (the two enzymes responsible for SREBP proteolysis and release). Using various pharmacological and RNA interference approaches, the authors showed that activation of the inflammasome, caspase 1, and the SREBPs was required for cell survival after exposure to aerolysin. — NRG

Cell 126, 1135 (2006).

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