The multigene families of actinoporins (part I): Isoforms and genetic structure

Valle, Aisel; Alvarado-Mesén, Javier; Lanio, María E.; Álvarez, Carlos; Barbosa, J.A.R.G.; Pazos, Fabiola

doi:10.1016/j.toxicon.2015.06.028

Cited by 32 publications

(42 citation statements)

References 95 publications

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“…It has long been known that individual sea anemone species produce many different actinoporin isoforms that, indeed, are very differently represented in terms of the amount present in their venomous secretions. In this regard, actinoporins represent a well established example of a multigenic protein family (38,39,43,45,46,51,73). They are not, however, the only example of toxic pore-forming multigene protein families (74), suggesting that the results shown now could be of larger significance and not only restricted to the actinoporin family.…”

Section: Discussionmentioning

confidence: 99%

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Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores

Rivera-de-Torre

García‐Linares

Alegre-Cebollada

et al. 2016

Journal of Biological Chemistry

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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.Actinoporins, single polypeptide chains of around 175 amino acids, constitute a family of toxic proteins produced by different sea anemone species. They show basic isoelectric point values and are usually cysteineless (1-4). Actinoporins belong to a much larger group of widely distributed proteins, known as pore-forming toxins, whose toxic activity relies on the formation of pores within biological membranes (5-9). All poreforming toxins show a very similar dual behavior by which they remain mostly monomeric and stably folded in aqueous solution but become oligomeric integral proteins when encountering membranes (2-4, 10 -23).The incorporation of actinoporins into the membrane largely depends on lipid bilayer composition and membrane physicochemical state (18, 24 -29). Both factors influence the conformational changes occurring during the transition from the water media to the inserted states of the protein (30, 31). Thus, high affinity recognition of sphingomyelin (SM) 3 is crucial for specific attachment to a membrane, but the subsequent effects observed also depend on the physical properties derived from its particular composition and not only from its SM content (23, 32). In fact, although still controversial, the presence of cholesterol and the coexistence of different phases in the membrane seem to be important factors, if not for binding then at least for the final formation of the pore (23,28,29,(32)(33)(34)(35)(36).Actinoporins have been isolated from more than 20 different sea anemone species (1, 3, 37-41) in agreement with their rather ubiquitous distribution within the Actinaria order (1). They display high sequence identities (between 60 and 80%) and appear as multigene families, ...

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Section: Discussionmentioning

confidence: 99%

“…Regarding the actinoporin family, it has been proposed that the existence of multiple isoforms would broaden the range of possible prey for a given species (38,39,43,45,46,51,73). In this regard, actinoporins might be similar to immunoglobulins, which require a plethora of highly diverse genes to counteract foreign antigens (45).…”

Section: Discussionmentioning

confidence: 99%

Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores

Rivera-de-Torre

García‐Linares

Alegre-Cebollada

et al. 2016

Journal of Biological Chemistry

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“…Although actinoporins are presumed to be found only in sea anemones, they resemble peptides from other cnidarians, molluscs, crustaceans, vertebrates, fungi, and plants [8,14,15]. The non-venomous function of actinoporin-like peptides remains unknown in most species; however, in bryophytes they are involved in drought tolerance [16], and in fishes they are presumed to be involved in membrane binding [17].…”

Section: Introductionmentioning

confidence: 99%

“…However, functional variation has been explored in a taxonomically restrictive manner, focusing primarily on EqII from Actinia equina (see [27,35,39,40]), and comparative analysis of species-specific isoforms of actinoporins have identified little variation among gene copies [15,41]. We revisit the question of variation in actinoporins by screening genome and transcriptome data of 25 species across four superfamilies.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the Cytolytic Pore-Forming Proteins (Actinoporins) in Sea Anemones

Macrander

Daly

2016

Toxins

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Sea anemones (Cnidaria, Anthozoa, and Actiniaria) use toxic peptides to incapacitate and immobilize prey and to deter potential predators. Their toxin arsenal is complex, targeting a variety of functionally important protein complexes and macromolecules involved in cellular homeostasis. Among these, actinoporins are one of the better characterized toxins; these venom proteins form a pore in cellular membranes containing sphingomyelin. We used a combined bioinformatic and phylogenetic approach to investigate how actinoporins have evolved across three superfamilies of sea anemones (Actinioidea, Metridioidea, and Actinostoloidea). Our analysis identified 90 candidate actinoporins across 20 species. We also found clusters of six actinoporin-like genes in five species of sea anemone (Nematostella vectensis, Stomphia coccinea, Epiactis japonica, Heteractis crispa, and Diadumene leucolena); these actinoporin-like sequences resembled actinoporins but have a higher sequence similarity with toxins from fungi, cone snails, and Hydra. Comparative analysis of the candidate actinoporins highlighted variable and conserved regions within actinoporins that may pertain to functional variation. Although multiple residues are involved in initiating sphingomyelin recognition and membrane binding, there is a high rate of replacement for a specific tryptophan with leucine (W112L) and other hydrophobic residues. Residues thought to be involved with oligomerization were variable, while those forming the phosphocholine (POC) binding site and the N-terminal region involved with cell membrane penetration were highly conserved.

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“…Most actinoporins do not contain Cys residues (Anderluh and Macek 2002;Valle et al 2015Valle et al , 2016, therefore, site-specific mutagenesis introducing a Cys residue has been a useful strategy to analyze the relevance of several amino acid positions to toxin function. Inclusion of a Cys residue in a specific position has allowed (1) the assessment of the structural and functional importance of the replaced residue; (2) the stabilization of conformational states by the non-native S-S bond (Hong et al 2002;Anderluh et al 2003;Kristan et al 2004;Penton et al 2011;Valle et al 2011;Hervis et al 2014); (3) the assessment of thiol-specific fluorescent labels (Malovrh et al 2003;Alegre-Cebollada et al 2007) or spin probe labels.…”

Section: Cys Mutants Of Stsmentioning

confidence: 99%

Biophysical and biochemical strategies to understand membrane binding and pore formation by sticholysins, pore-forming proteins from a sea anemone

et al. 2017

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Actinoporins constitute a unique class of poreforming toxins found in sea anemones that are able to bind and oligomerize in membranes, leading to cell swelling, impairment of ionic gradients and, eventually, to cell death. In this review we summarize the knowledge generated from the combination of biochemical and biophysical approaches to the study of sticholysins I and II (Sts, StI/II), two actinoporins largely characterized by the Center of Protein Studies at the University of Havana during the last 20 years. These approaches include strategies for understanding the toxin structure-function relationship, the protein-membrane association process leading to pore formation and the interaction of toxin with cells. The rational combination of experimental and theoretical tools have allowed unraveling, at least partially, of the complex mechanisms involved in toxin-membrane interaction and of the molecular pathways triggered upon this interaction. The study of actinoporins is important not only to gain an understanding of their biological roles in anemone venom but also to investigate basic molecular mechanisms of protein insertion into membranes, protein-lipid interactions and the modulation of protein conformation by lipid binding. A deeper knowledge of the basic molecular mechanisms involved in Sts-cell interaction, as described in this review, will support the current investigations conducted by our group which focus on the design of immunotoxins against tumor cells and antigen-releasing systems to cell cytosol as Stsbased vaccine platforms.

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The multigene families of actinoporins (part I): Isoforms and genetic structure

Cited by 32 publications

References 95 publications

Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores

Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores

Evolution of the Cytolytic Pore-Forming Proteins (Actinoporins) in Sea Anemones

Biophysical and biochemical strategies to understand membrane binding and pore formation by sticholysins, pore-forming proteins from a sea anemone

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