Biologists have unveiled a new twist in a metabolic pathway that cells use to defend themselves against toxins made by disease-causing bacteria. The discovery of this pathway, published in the September 22 issue of the journal Cell, helps 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. Pore-forming toxins compose about a quarter of all known protein toxins that increase the infectivity and severity of bacterial diseases.
When 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.
Caspase-1 also triggers the cell's central regulators for membrane synthesis, which launchs a bout of lipid metabolism. This previously undetected part of the response pathway has important implications for cell survival. The lipids are probably used to repair the cell membrane, stopping the potassium leak, which itself can kill the cell, and also protecting the cell from additional toxic substances lurking outside.
This result is important, because it also explains so much in terms of basic cell physiology. If a cell absorbs too much water, for example, this pathway would be triggered. The lipids formed in the metabolic pathway would enable the cell to enlarge its membrane to accommodate the extra water. Once again,we have the power to utilize true understanding of physiology when we use Guided Visualizations during our hypnosis sessions.