( Biologists at the EPFL (Ecole Polytechn...)A new understanding of how cells defend themselves against bacterial pore-forming toxins

The discovery of this pathway, published in the September 22 issue of the journal Cell, advances our understanding of how cells mount a survival response when attacked by bacteria and parasites and also gives insight into the more general process of cell membrane biogenesis.

Bacteria and parasites often use special toxins to perforate the membranes of target cells. These pore-forming toxins are a key weapon in the attack arsenal of some common and virulent bacteria, such as Staphylococcus aureus, well-known for its role in hospital-acquired infections, Streptococcus pneumonie, responsible for middle ear infections and pneumonia, and Helicobacter pylori, implicated in ulcers. Pore-forming toxins compose about a quarter of all known protein toxins that increase the infectivity and severity of bacterial diseases.

Once the toxin perforates the host membrane, ions begin to leak out of the cell. Sensing a drop in its potassium concentration, the cell reacts by forming a multi-protein complex known as an inflammasome. Scientists know that inflammasomes act like a sort of roving security force inside the cell, detecting a variety of danger signals such as bacterial RNA or bits of bacterial flagellin. The inflammasomes join together and activate a protein, caspase-1, that in turn triggers an inflammatory response.

Van der Goot and her colleagues found that in addition to its normal role as a signal for inflammatory response, caspase-1 also triggers the cell's central regulators for membrane synthesis, launching a bout of lipid metabolism. This previously undetected part of the response pathway has important implications for cell survival.

The Swiss team studied the pathway by using RNA interference to silence genes involved. Interr
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Source:Ecole Polytechnique F茅d茅rale de Lausanne