A hole in the protective shell almost certainly means death for a cell. That's why she keeps a first aid kit on hand to plug holes caused by bacterial toxins.
Staphylococcus aureus can't help it: If the bacterium wants to live, it has to find a host cell and crack it. Once the tiny creature that causes life-threatening diseases such as pneumonia and sepsis has found a suitable victim, it abuses it with special toxins that drill holes into the attacked cells. The fate of the victim is usually sealed: once the cell has been perforated, it only has a small chance of survival. Conversely, the survival of the attacker is secured for now. Incidentally, numerous other pathogenic bacteria also proceed according to the same principle.
But the victims are not quite as defenseless as they might first appear: As the team led by Gisou van der Goot from the Polytechnic University in Lausanne has now discovered, they have a mechanism with which they can protect themselves from attacking bacteria drilled holes.
The researchers investigated the survival mechanisms with which cells try to save themselves from bacterial toxins. To do this, the scientists treated cell cultures with the bacterial toxin aerolysin. This molecule penetrates the cell membrane and forms a pore in it that allows small ions to flow in and out of the cell.
The scientists now observed that the cells perforated with the help of aerolysin lost potassium through the resulting pores. The cells registered this loss as an alarm signal and promptly formed complexes of several proteins, so-called inflammasomes. These are always produced in response to various alarm signals and activate another enzyme, caspase-1, which in turn normally stimulates inflammation through the production of interleukins or starts the cell's suicide program in macrophages.
Van der Goot and colleagues have now discovered a completely different task of the enzyme in their cells perforated by the bacterial toxin: Caspase-1 set the cell's repair mechanism in motion there.
In response to the potassium loss alarm signal, the protein in the m altreated cells first activated another protein called SREBP (sterol r egulatory element binding protein), which in turn stimulated the synthesis of lipids after a further intermediate step.
If the scientists interrupted these processes at any point, many more cells fell victim to the toxin than if the process was allowed to proceed unhindered - the newly discovered mechanism thus increased the chances of survival of the attacked cells.
We do not yet know the details of the pathway by which lipid synthesis ensures cell survival
(Gisou Van der Goot) "We still don't know the details of how lipid synthesis ensures cell survival," says Van der Goot. However, the scientists suspect that the lipids newly synthesized in response to the call for help are ultimately used to plug the holes in the cell membrane.