title: Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores.
abstract: Among the toxic polypeptides secreted in the venom of sea anemones, actinoporins are the pore-forming toxins whose toxic activity relies on the formation of oligomeric pores within biological membranes. Intriguingly, actinoporins appear as multigene families that give rise to many protein isoforms in the same individual displaying high sequence identities but large functional differences. However, the evolutionary advantage of producing such similar isotoxins is not fully understood. Here, using sticholysins I and II (StnI and StnII) from the sea anemone Stichodactyla helianthus, it is shown that actinoporin isoforms can potentiate each other's activity. Through hemolysis and calcein releasing assays, it is revealed that mixtures of StnI and StnII are more lytic than equivalent preparations of the corresponding isolated isoforms. It is then proposed that this synergy is due to the assembly of heteropores because (i) StnI and StnII can be chemically cross-linked at the membrane and (ii) the affinity of sticholysin mixtures for the membrane is increased with respect to any of them acting in isolation, as revealed by isothermal titration calorimetry experiments. These results help us understand the multigene nature of actinoporins and may be extended to other families of toxins that require oligomerization to exert toxicity.
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid.
authors.forename: Esperanza
authors.initials: E
authors.lastname: Rivera-de-Torre
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid.
authors.forename: Sara
authors.initials: S
authors.lastname: García-Linares
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares Carlos III, 28029 Madrid, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Alegre-Cebollada
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid.
authors.forename: Javier
authors.initials: J
authors.lastname: Lacadena
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid. Electronic address: ppgf@bbm1.ucm.es.
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid. Electronic address: alvaromp@quim.ucm.es.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Martínez-Del-Pozo
mesh_terms: D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D006461:Hemolysis; D008563:Membrane Lipids / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D018272:Porins / Q000737:chemistry / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism*; D012615:Sea Anemones
chemical_list: D008563:Membrane Lipids; D010743:Phospholipids; D018272:Porins; D020033:Protein Isoforms
keywords: equinatoxin; erythrocyte; ion channel; lipid-protein interaction; lysis; oligomerization; pore-forming-toxin; protein cross-linking; sticholysin; toxin