Membrane Lipids Modulate the Activity of the Pore-forming Toxin Sticholysin II

Martinez D¹, Alvarez C¹, Pazos IF¹, Tejuca M¹, Lanio ME¹, Gutierrez-Aguirre I², Barlic A², Lissi EA³ and Gonzalez-Mañas JM²

1 Centro de Estudio de Proteínas. Facultad de Biología. Universidad de la Habana. Cuba; 2  Unidad de Biofísica. Universidad del País Vasco, Bilbao, España; 3 Facultad de Química y Biología. Universidad de Santiago de Chile. Chile.

Sticholysin II (St II) is a cytolysin produced by sea anemone Stichodactyla helianthus, characterized by forming oligomeric pores in natural and model membranes. A general property of this toxin is its preference for membranes containing sphingomyelin (SM). To better characterize the lipid dependence of the cytolysin-membrane interaction, we have evaluated the effect of membrane SM, cholesterol (Cho) and the typical non-bilayer forming lipid dioleyl phosphatidylethanolamine (PE) on binding and functional activity of St II using lipid monolayers and liposomes. The aim of this work was to clarify the role of Cho and PE, both in St II binding and pore formation efficiency. It was found that, albeit inefficiently, St II binds to egg phosphatidylcholine (PC): Cho monolayers and liposomes lacking SM and is able to form active pores in these bilayers. The simultaneous presence of SM and relatively large amounts of Cho (35%) resulted in the highest values of critical pressure and rate of association to monolayers and notably increased the permeabilization ability of this toxin. It is proposed that microdomains present in the bilayers or promoted by the strong SM/toxin interaction could be important for toxin function. The presence in membrane of PE, favored the permeabilization of vesicles induced by Sticholysin, without eliciting significant differences in association. This effect is probably related with the contribution of this lipid to the formation of the lipidic toroidal pore, previously described for sticholysins by us.

Supported by: MUTIS- fellowship, CONICYT-CITM Projects and AlmaMater Project

Correspondence to: calvarez@fbio.uh.cu