title: Membrane-damaging action of staphylococcal alpha-toxin on phospholipid-cholesterol liposomes.
abstract: The mechanism of membrane damage by staphylococcal alpha-toxin was studied using carboxyfluorescein (internal marker)-loaded multilamellar liposomes prepared from various phospholipids and cholesterol. Liposomes composed of phosphatidylcholine or sphingomyelin and cholesterol bound alpha-toxin and released carboxyfluorescein in a dose dependent manner, when they were exposed to alpha-toxin of concentrations higher than 1 or 8 micrograms/ml, respectively. In contrast, the other liposomes composed of phosphatidylethanolamine, phosphatidylserine, phosphatidylglycerol or phosphatidylinositol plus cholesterol were not susceptible to the toxin even at high concentrations up to 870 micrograms/ml. The insensitive liposomes containing either phosphatidylserine or phosphatidylglycerol were made sensitive to alpha-toxin by inserting phosphatidylcholine into the liposomal membranes. In addition, phosphorylcholine inhibited the toxin-induced marker release from liposomes. These results indicated that the choline-containing phospholipids are required for the interaction between alpha-toxin and liposomal membranes. Susceptibility of liposomes containing phosphatidylcholine or sphingomyelin increased with the increase in cholesterol contents of the liposomes. Based on these results, we propose that the choline-containing phospholipids are possible membrane components or structures responsible for the toxin-membrane interaction, which leads to damage of membranes. Furthermore, cholesterol may facilitate the interaction between alpha-toxin and membrane as a structural component of the membrane.
mesh_terms: D001427:Bacterial Toxins; D002784:Cholesterol; D005452:Fluoresceins; D006460:Hemolysin Proteins; D007700:Kinetics; D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; D013109:Sphingomyelins
chemical_list: D001427:Bacterial Toxins; D005452:Fluoresceins; D006460:Hemolysin Proteins; D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; D013109:Sphingomyelins; C021091:staphylococcal alpha-toxin; C024098:6-carboxyfluorescein; D002784:Cholesterol