Marine Biotechnology

, Volume 8, Issue 1, pp 1–10 | Cite as

Peptide Toxins in Sea Anemones: Structural and Functional Aspects

Open Access
Review Article

Abstract

Sea anemones are a rich source of two classes of peptide toxins, sodium channel toxins and potassium channel toxins, which have been or will be useful tools for studying the structure and function of specific ion channels. Most of the known sodium channel toxins delay channel inactivation by binding to the receptor site 3 and most of the known potassium channel toxins selectively inhibit Kv1 channels. The following peptide toxins are functionally unique among the known sodium or potassium channel toxins: APETx2, which inhibits acid-sensing ion channels in sensory neurons; BDS-I and II, which show selectivity for Kv3.4 channels and APETx1, which inhibits human ether-a-go-go-related gene potassium channels. In addition, structurally novel peptide toxins, such as an epidermal growth factor (EGF)-like toxin (gigantoxin I), have also been isolated from some sea anemones although their functions remain to be clarified.

Keywords

peptide toxin potassium channel toxin sea anemone sodium channel toxin 

Introduction

Members of the phylum Cnidaria commonly possess specialized stinging organelles (nematocysts) to capture prey animals. On chemical or physical stimulation, the thread tubule folded in the nematocyst is discharged and penetrates the epithelium of the victim. Simultaneously, toxins in the nematocyst enter the victim through the thread tubule, leading to its paralysis. Apart from the inherent biological function in sea anemones, nematocyst toxins from some species of sea anemones such as Anemonia sulcata and Phyllodiscus semoni are even dangerous to humans. When an individual is stung by nematocysts, local inflammations, including severe pain, redness, and edema are immediately induced by toxins.

In general, sea anemone toxins are considerably stable compared to other cnidarian toxins (typically jellyfish toxins). Thus, a number of toxins have so far been isolated from various species of sea anemones and well characterized, although it is not always clear whether these toxins are derived from nematocysts. Most of the sea anemone toxins are divided into the following three classes: 20-kDa pore-forming cytolysins inhibitable by sphingomyelin (now called actinoporins; Kem, 1988; Anderluh and Macek, 2002), 3- to 5-kDa neurotoxins acting on voltage-gated sodium channels (Kem, 1988; Kem et al., 1990; Norton, 1991), and 3.5- to 6.5-kDa neurotoxins acting on voltage-gated Kv1 potassium channels (Castañeda et al., 1995; Schweitz et al., 1995; Cotton et al., 1997; Gendeh et al., 1997; Minagawa et al., 1998a). Of the three classes of toxins, both sodium and potassium channel peptide toxins have been useful tools for studying the structure and function of ion channels, because of their high affinity to the specific channel. Besides the well-characterized peptide toxins, structurally and/or functionally novel peptide toxins, which seem to be promising pharmacological reagents, have recently emerged from some species of sea anemones.

In this article, accumulated knowledge on the structural and functional aspects of sea anemone peptide toxins is reviewed, with special emphasis on sea anemones as an important source of fascinating pharmacological tools. The three-dimensional structure–function relationships have been clarified for some sea anemone peptide toxins (Gasparini et al., 2004; Mouhat et al., 2004) but are not included in this review because of space limitations.

Sodium Channel Peptide Toxins

Since the first discovery of three toxins in Anemonia sulcata (Béress et al., 1975), more than 50 sodium channel peptide toxins have been isolated and/or cloned from various species of sea anemones. As proposed by Norton (1991), most of the sea anemone sodium channel toxins can be classified into three types based on the determined amino acid sequences (Figure 1). As listed in Table 1, as many as 33 and 9 toxins have been identified as type 1 and 2 toxins, respectively. For type 1 and 2 toxins, therefore, only some typical sequences are included in Figure 1.
Fig. 1

Amino acid sequences of soidum channel toxins from sea anemones. ApA and ApB are from Anthopleura xanthogrammica (Tanaka et al., 1977; Reimer et al., 1985); ATX II from Anemonia sulcata (Wunderer et al., 1976); Ae I from Actinia equina (Lin et al., 1996); Cp I from Condylactis passiflora (Shiomi et al., 1995); Rc I from Radianthus (Heteractis) crispus (Shiomi et al., 1996); AFT I from Anthopleura fuscoviridis (Sunahara et al., 1987); halcurin from Halcurias sp. (Ishida et al., 1997a,b); RTX I and RTX II from Radianthus (Heteractis) macrodactylus (Zykova et al., 1988a, 1989); Rp III from Radianthus (Heteractis) paumotensis (Metrione et al., 1987); Sh I from Stichodactyla helianthus (Kem et al., 1989); gigantoxin III from Stichodactyla gigantea (Shiomi et al., 2003); PaTX from Entacmaea (Parasicyonis) actinostoloides (Nishida et al., 1985); Da I and Da II from Dofleinia armata (Honma et al., 2003a); Er I from Entacmaea ramsayi (Honma et al., 2003a); ATX III from Anemonia sulcata (Martinez et al., 1977); calitoxins I and II from Calliactis parasitica (Cariello et al., 1989; Spagnuolo et al., 1994). Hydroxy-Pro at position 3 of Cp I and Rc I are denoted by “O.” Identical amino acid residues with ApA, RTX I, PaTX, and calitoxin I are boxed for type 1, 2, and 3 toxins and calitoxins, respectively. Asterisks represent the common amino acid residues for both type 1 and 2 toxins. The lines above and below the sequence of halcurin indicate the residues peculiar to type 1 and 2 toxins, respectively.

Table 1

Distribution of Type 1 and 2 Sodium Channel Toxins in Sea Anemones

Species

Type 1 toxins

Type 2 toxins

References

Family Actiniidae

 Actinia equina

Ae I

 

Lin et al., 1996

 Anemonia erythraea

AETX I

 

Shiomi et al., 1997

 Anemonia sulcata

ATX Ia and Ib

 

Widmer et al., 1988

ATX II

 

Wunderer et al., 1976

ATX V

 

Scheffler et al., 1982

 Anthopleura elegantissima

ApC

 

Norton, 1981

APE 1–1, 1–2, and 2–2

 

Bruhn et al., 2001

 Anthopleura fuscoviridis

AFT I and II

 

Sunahara et al., 1987

 Anthopleura xanthogrammica

ApA

 

Tanaka et al., 1977

ApB

 

Reimer et al., 1985

PCR1–2, 2–1, 2–5, 2–10, 3–6, and 3–7

 

Kelso and Blumenthal, 1998

 Anthopleura sp.

Hk2a, 7a, 8a, and 16a

 

Wang et al., 2004

 Bunodosoma caissarum

Bc III

 

Malpezzi et al., 1993

 Bunodosoma cangicum

Cangitoxin

 

Cunha et al., 2005

 Bunodosoma granulifera

Bg II and III

 

Loret et al., 1994

 Condylactis passiflora

Cp I and II

 

Shiomi et al., 1995

Family Stichodactylidae

 Antheopsis maculata

Am III

 

Honma et al., 2005

 Radianthus (Heteractis) crispus

Rc I

 

Shiomi et al., 1996

 Radianthus (Heteractis) macrodactylus

 

RTX I

Zykova and Kozlovskaya, 1989

 

RTX II

Zykova et al., 1988a

 

RTX III

Zykova et al., 1985b

 

RTX IV and V

Zykova et al., 1988b

 Radianthus (Heteractis) paumotensis

 

Rp II

Schweitz et al., 1985

 

Rp III

Metrione et al., 1987

 Stichodactyla gigantea

Gigantoxin II

Gigantoxin III

Shiomi et al., 2003

 Stichodactyla helianthus

 

Sh I

Kem et al., 1989

Type 1 and 2 toxins are composed of 46 to 49 amino acid residues, except for Ae I of 54 residues (Lin et al., 1996), and cross-linked by three disulfide bridges (4–46, 6–36, and 29–47; numbering is based on the amino acid sequence of ApA). Ten residues including six Cys residues are completely conserved between type 1 and 2 toxins. In view of the fact that a toxin (halcurin) with structural features of both type 1 and 2 toxins is present in Halcurias sp. (Ishida et al., 1997a), the most primitive species belonging to the suborder Endocoelantheae compared to the other species so far studied of the suborder Nynantheae, both type 1 and 2 toxins are considered to have evolved from the same ancestor gene. However, they are immunologically distinguishable from each other because no antigenic cross-reactivity between both types of toxins is recognized (Schweitz et al., 1985; Kem et al., 1989). It is interesting to note that the distribution of type 1 and 2 toxins seems to be related to the taxonomical position of sea anemones; members of the family Actiniidae contain only type 1 toxins, while either type 1 or 2 toxins or both type 1 and 2 toxins are found in those of the family Stichodactylidae.

Type 3 sodium channel toxins are shorter peptides composed of 27 to 32 amino acid residues. Previously, two toxins, PaTX from Entacmaea actinostoloides (formerly called Parasicyonis actinostoloides; Nishida et al., 1985) and ATX III from Anemonia sulcata (Martinez et al., 1977), have been tentatively classified into type 3 toxins (Norton, 1991). However, PaTX and ATX III are cross-linked by four and three disulfide bridges, respectively, implying that they share no structural scaffold. In our recent study, two toxins (Da I and II) isolated from Dofleinia armata and one toxin (Er I) from Entacmaea ramsayi were found to be homologous with PaTX (Honma et al., 2003a), suggesting a wide distribution of PaTX-like toxins in sea anemones. Therefore, it may be reasonable to include only PaTX and its analogs in the category of type 3 toxins.

At least six different receptor sites for neurotoxins are known for the mammalian sodium channels. Similar to α-scorpion toxins, sea anemone type 1–3 toxins bind to the receptor site 3 of sodium channels and prolong the open state of the channels during the depolarization procedure (Catterall and Béress, 1978; Vincent et al., 1980; Schweitz et al., 1981; Warashina et al., 1988a,b; Norton, 1991). Because of this unique action on the sodium channels, some of the known sea anemone sodium channel toxins, such as ATX II from Anemonia sulcata (Wunderer et al., 1976) and anthopleurin A (ApA; Tanaka et al., 1977) and B (ApB; Reimer et al., 1985) from Anthopleura xanthogrammica, have been used as valuable pharmacological reagents in many laboratories of the world. Detailed molecular studies on the interaction with sodium channels have been performed using ApB and its various site-directed mutants. The results show that the flexibility of the region 8–17 (Arg-14 loop) is essential for toxin binding to sodium channels (Seibert et al., 2003). As for individual residues, Arg-12 within the Arg-14 loop and Leu-18 and Ser-19 proximal to the C-terminus of the loop greatly contribute to toxin affinity (Gallagher and Blumenthal, 1994; Dias-Kadambi et al., 1996; Seibert et al., 2004). It is worth mentioning that ApB has no selectivity for neuronal and cardiac sodium channels, while ApA is selective for cardiac channels. This difference in selectivity between ApA and ApB is associated with the replacements at positions 12 and 49 (Khera et al., 1995). Furthermore, experiments using mutants of either neuronal sodium channels (Rogers et al., 1996) or cardiac sodium channels (Benzinger et al., 1998) suggested that the receptor site 3 is involved in the extracellular loop IVS3-S4 and that anionic residues (Glu-1613 and Glu-1616 for neuronal channels and Asp-1612 for cardiac channels) in the IVS3-S4 loop electrostatically interact with basic residues of toxins. However, more recent study using six different sodium channel genes (Nav1.1-1.6) showed that some nearby amino acids, which are different in the channels, contribute to the interaction with toxins (Oliveira et al., 2004).

Besides the type 1–3 toxins described above, two novel sodium channel toxins, calitoxins I and II (46 amino acid residues) distinguishable by only one replacement at position 6, have been isolated or cloned from Calliactis parasitica (Cariello et al., 1989; Spagnuolo et al., 1994). Both calitoxins are comparable to type 1 and 2 toxins as to chain length and disulfide bridge pattern but their entire amino acid sequences greatly differ from those of type 1 and 2 toxins. They act on voltage-gated sodium channels probably in a similar manner to type 1–3 toxins.

Potassium Channel Peptide Toxins

It has not been long since sea anemone potassium channel peptide toxins were discovered in the mid-1990s. Nevertheless, much knowledge on their structures and functions has been accumulated in the last decade. Based on the structural and functional differences, the 11 potassium channel peptide toxins so far isolated can be classified into three types as shown in Figure 2.
Fig. 2

Amino acid sequences of potassium channel toxins from sea anemones. ShK is from Stichodactyla helianthus (Castañeda et al., 1995); AsKS (kaliseptine), AsKC 1-3 (kalicludines 1–3), BDS-I and BDS-II from Anemonia sulcata (Schweitz et al., 1995; Diochot et al., 1998); BgK from Bunodosoma granulifera (Cotton et al., 1997); HmK from Radianthus (Heteractis) magnifica (Gendeh et al., 1997); AeK from Actinia equina (Minagawa et al., 1998a); APET×1 from Anthopleura elegantissima (Diochot et al., 2003). Identical residues with ShK, AsKC 1, and BDS-I are boxed for type 1, 2, and 3 toxins, respectively. For reference, the amino acid sequences of dendrotoxin I, a potassium channel toxin from black mamba, and BPTI (bovine pancreatic trypsin inhibitor) are aligned with those of type 2 toxins.

Type 1 potassium channel toxins blocking Kv1 (Shaker) potassium channels include ShK from Stichodactyla helianthus (Castañeda et al., 1995), AsKS (kaliseptine) from Anemonia sulcata (Schweitz et al.,1995),BgK from Bunodosoma granulifera (Cotton et al., 1997), HmK from Heteractis magnifica (Gendeh et al., 1997), and AeK from Actinia equina (Minagawa et al., 1998a). These toxins are composed of 35 to 37 amino acid residues and cross-linked by three disulfide bridges (3–35, 12–28, and 17–32; numbering is based on the amino acid sequence of ShK). Alanine scanning experiments identified three residues, Ser-20, Lys-22, and Tyr-23, as essential for the binding of ShK to rat brain potassium channels (Pennington et al., 1996). Similar experiments carried out on BgK also proved that the corresponding residues (Ser-23, Lys-25, and Tyr-26) are involved in the binding to rat brain potassium channels (Dauplais et al., 1997) and Kv1.1, Kv1.2, Kv1.3, and Kv1.6 channels (Alessandri-Haber et al., 1999; Gilquin et al., 2002). These three residues are completely conserved in the other type 1 toxins. Of the three residues, the dyad (Lys-Tyr) is considered to be especially important for the biding to potassium channels. It is interesting to note that scorpion toxins blocking Kv1 channels, such as charybdotoxin and margatoxin, contain a similar dyad composed of Lys and a hydrophobic residue (e.g., Lys-27 and Tyr-36 for charybdotoxin), which is critical for their binding to Kv1 channels (Dauplais et al., 1997; Gasparini et al., 2004). Although there is a distinct difference in molecular scaffold between sea anemone type 1 potassium channel toxins and scorpion potassium channel toxins, the important dyads of both toxins superimpose in the three-dimensional structures. It is thus assumed that structurally unrelated toxins (sea anemone and scorpion toxins) have undergone convergent evolution to bind to the same region of structurally related targets (Gasparini et al., 2004).

Type 2 potassium channel toxins, AsKC 1-3 (kalicludines 1–3), are composed of 58 or 59 amino acid residues and also exhibit blocking of Kv1 channels with much less potency than type 1 toxins (Schweitz et al., 1995). In accordance with the sequence homologies with Kunitz-type protease inhibitors, such as bovine pancreatic trypsin inhibitor (BPTI), AsKCs have protease inhibitory activity although less potently than BPTI. As compared to the three residues (Lys-15, Ala-16, and Ile-19) of BPTI, which are known to be important to bind to trypsin, AsKCs have a significant replacement (Ile by Pro) at position 19, leading to their weaker inhibitory activity than BPTI. In relation to this, dendrotoxins, Kv1 channel blockers from either green or black mamba, also share high sequence homologies with Kunitz-type protease inhibitors but exhibit no protease inhibitory activity.

It should be noted that various species of sea anemones contain Kunitz-type protease inhibitors (Wunderer et al., 1981; Zykova et al., 1985a; Antuch et al., 1993; Ishida et al., 1997b; Minagawa et al., 1997, 1998b). Sea anemone protease inhibitors have been considered to function to inhibit endogenous proteases in animals themselves or to protect the toxins injected into prey animals or predators from rapid degradation. However, the finding of potassium channel toxins with protease inhibitory activity, such as AsKCs, leads us to assume that sea anemone protease inhibitors serve not only as defensive substances but also as offensive substances to paralyze prey animals. It is interesting to examine whether the sea anemone protease inhibitors so far isolated have potassium channel toxicity.

Three toxins, BDS-I and II from Anemonia sulcata (Diochot et al., 1998) and APETx1 from Anthopleura elegantissima (Diochot et al., 2003), are members of type 3 potassium channel toxins. BDS-I and II are the first specific blockers of Kv3.4 channels and are substantially inactive to other members of the Kv3 (Shaw) subfamily. Although they show about 25% sequence identities with type 1 sodium channel toxins such as ApA and ATX II, they elicit no effect on sodium channels in cardiac and skeletal muscle cells; they have only a weak effect on tetrodotoxin-sensitive sodium channels in neuroblastoma cells. On the other hand, APETx1 has 64%, 42%, and 42% sequence identities with APETx2, BDS-I, and BDS-II, respectively, and also shares the same structural scaffold with them but its target channel is different. It is a selective blocker of human ether-a-go-go-related gene (HERG or erg1) potassium channels. Besides APETx1, two scorpion toxins, ErgTx from Centruroides noxius (Gurrola et al., 1999) and BeKm-1 from Buthus eupeus (Korolkova et al., 2001), have also been reported to be potent inhibitors of HERG channels.

Acid-Sensing Ion Channel Peptide Toxin

APETx2 (42 amino acid residues) isolated from Anthopleura elegantissima (Diochot et al., 2004) is functionally quite unique. Although it shares 36% to 64% sequence identities with type 3 potassium channel toxins, BDS-I and II from Anemonia sulcata and APETx1 from Anthopleura elegantissima (Figure 3), it inhibits not potassium channels but acid-sensing ion channels (ASICs, H+-gated sodium channels; Waldmann and Lazdunski, 1998) in sensory neurons, which are implicated in the modulation of pain sensation. ASICs are formed by homomeric or heteromeric association of six different subunits (ASIC1a, ASIC1b, ASIC2a, ASIC2b, ASIC3, and ASIC4) and only ASIC3 channels and ASIC3-containing channels are affected by APETx2. Until the discovery of APETx2, psalmotoxin 1 (PcTX1) from the tarantula Psalmopoeus cambridgei has been the sole toxin acting on ASICs (Escoubas et al., 2000). However, APETx2 has no sequence homology with PcTX1 and is functionally discriminated from PcTX1 inhibiting homomeric ASIC1a channels. Since APETx2 is the first specific inhibitor for ASIC3 channels and ASIC3-containing channels, it will be a promising tool to study the physiological involvement of ASIC3 channels in neuronal excitability and pain coding.
Fig. 3

Alignment of the amino acid sequence of APET×2 (Diochot et al., 2004) with those of BDS-I and BDS-II from Anemonia sulcata (Diochot et al., 1998) and APET×1 from Anthopleura elegantissima (Diochot et al., 2003). Identical residues with APET×2 are boxed.

Other Structurally Novel Peptide Toxins

In addition to the peptide toxins described above, the following structurally novel peptide toxins have been isolated although not functionally characterized: AETX II and III from Anemonia erythraea (Shiomi et al., 1997), gigantoxin I from Stichodactyla gigantea (Shiomi et al., 2003; Honma et al., 2003b), and Am I and II from Antheopsis maculata (Honma et al., 2005a).

AETX II and III are composed of 59 amino acid residues and are highly homologous with each other (Figure 4). There are only four substitutions between both toxins. These toxins are featured by the presence of as many as 10 Cys residues probably forming five disulfide bridges. Moreover, they are most potently lethal to crabs among the peptide toxins so far isolated from sea anemones by our laboratory; the LD50 values of AETX II and III against crabs are 0.53 and 0.28 μg/kg, respectively.
Fig. 4

Amino acid sequences of AETX II and III from Anemonia erythraea (Shiomi et al., 1997). Identical residues are boxed.

Gigantoxin I, which is not lethal but potently paralytic to crabs with an ED50 of 215 μg/kg, was discovered through a careful observation of the symptoms of crabs injected with samples. Very surprisingly, it shows about 35% sequence homologies with epidermal growth factors (EGFs) from mammals (Figure 5). Consistent with the structural resemblance in Figure 5, gigantoxin I displays EGF activity, as evidenced by rounding of human epidermoid carcinoma A431 cells and tyrosine phosphorylation of the EGF receptor in the cells, although much less potently than human EGF. The finding of an EGF-like molecule (gigantoxin I) with both toxic and EGF activities in the sea anemone S. gigantea, which is the nearest to the phylogenetic root of the animal kingdom, allows us to assume that the ancestors of EGFs originally had functioned as toxins as in the case of gigantoxin I and that they had lost toxic properties during the evolution process.
Fig. 5

Alignment of the amino acid sequence of gigantoxin I (Shiomi et al., 2003) with those of mammalian epidermal growth factors (EGFs). Identical residues with gigantoxin I are boxed.

Am I (27 amino acid residues) appears to act on sodium channels from the lethality to crabs (LD50 830 μg/kg). Differing from all the known sea anemone peptide toxins, Am I has only four Cys residues, suggesting its unique conformation to be clarified (Figure 6). It is also interesting to note that the Am I precursor contains as many as six copies of Am I. On the other hand, Am II (46 amino acid residues) is only paralytic to crabs (ED50 420 μg/kg), similar to gigantoxin I. It should be emphasized that the crab assay is a simple and useful tool to discover new toxins, such as Am II and gigantoxin I, if only the symptoms induced in crabs by samples are carefully observed. It is worth mentioning that Am II is homologous to APETx2 (ASIC3 channel blocker), BDS-I (Kv3.4 channel blocker), BDS-II (Kv3.4 channel blocker), and APETx1 (HERG channel blocker) with 28%, 39%, 39%, and 37% sequence identities, respectively (Figure 6). Despite the structuralsimilarity, APETx2, BDS-I, BDS-II, and APETx1 target different ion channels. Am II may act to specialized ion channels or one of the ion channels targeted by these four toxins.
Fig. 6

Amino acid sequences of Am I and II from Antheopsis maculata (Honma et al., 2005). The amino acid sequences of four peptide toxins, BDS-I and BDS-II from Anemonia sulcata (Diochot et al., 1998) and APET×1 and APET×2 from Anthopleura elegantissima (Diochot et al., 2003, 2004), are aligned with that of Am II. Hydroxy-Pro at position 24 of Am II is denoted by “O.” Identical residues with Am II are boxed.

The sea anemone peptide toxins described above are all derived from the whole bodies, tentacles or secreted mucus. However, we recently found that the extract from special aggressive organs (acrorhagi) of Actinia equina is toxic to crabs. The acrorhagi are located in a ring around the base of the tentacles in certain species of sea anemones belonging to the family Actiniidae and used to fight with nonspecific non-clonemates. Two novel peptide toxins, acrorhagins I (50 amino acid residues) and II (44 amino acid residues), were isolated from the acrorhagi of A. equina (Figure 7; Honma et al., 2005b). Acrorhagin I has no sequence homologies with any toxins from other biological sources. On the other hand, acrorhagin II is somewhat homologous (20% to 27% identity) with hainantoxin-I (sodium channel toxin) from the Chinese bird spider Selenocosmia hainana (Li et al., 2003), ω-conotoxin MVIIB (calcium channel toxin) from the cone snail Conus magus (Olivera et al., 1985), and Tx 3-2 (calcium channel toxin) from the Brazilian armed spider Phoneutria nigriventer (Cordeiro et al., 1993). However, there is a distinct difference in the location of Cys residues between acrorhagin II and the other three toxins, suggestingthat acrorhagin II has a different conformation from the other three toxins. Our results strongly suggest the acrorhagi to be a new source of peptide toxins.
Fig. 7

Amino acid sequences of acrorhagins I and II from acrorhagi of Actinia equina (Honma et al., in press). The amino acid sequences of three peptide toxins, hainantoxin-I from the Chinese bird spider Selenocosmia hainana (Li et al., 2003), ω-conotoxin MVIIB from the cone snail Conus magus (Olivera et al., 1985), and Tx 3-2 from the Brazilian armed spider Phoneutria nigriventer (Cordeiro et al., 1993), are aligned with that of acrorhagin II. Identical residues with acrorhagin II are boxed.

Concluding Remarks

In the early 1990s, it was once concluded that sodium channel toxins binding to the receptor site 3 are the sole family of sea anemone peptide toxins. However, potassium channel peptide toxins have emerged as a new family of peptide toxins in the mid-1990s and structurally and functionally novel peptide toxins have also been discovered one after another. As a result of extensive studies on sea anemone peptide toxins, some of them have been used as valuable tools in studying the structure and function of ion channels. Importantly, only about 40 species have been examined for peptide toxins, although more than 800 species of sea anemones are recorded in the world. In the course of our screening for toxins in sea anemones, all species tested have been found to contain toxins that are lethal or paralytic to crabs, suggesting the universal distribution of peptide toxins in sea anemones. This article ends with the hope that future study on sea anemone peptide toxins will discover fascinating new molecules acting on specific ion channels, expanding our understanding of the structure and function of various ion channels deeply implicated in the physiology of animals.

References

  1. Alessandri-Haber, N, Lecoq, A, Gasparini, S, Grangier-Macmath, G, Jacquet, G, Harvey, AL, Medeiros, C, Rowan, EG, Gola, M, Ménez, A, Crest, M 1999Mapping the functional anatomy of BgK on Kv1.1, Kv1.2, and Kv1.3. Clues to design analogs with enhanced selectivityJ Biol Chem2743565335661CrossRefGoogle Scholar
  2. Anderluh, G, Macek, P 2002Cytolytic peptide and protein toxins from sea anemones (Anthozoa: Actiniaria)Toxicon40111124CrossRefGoogle Scholar
  3. Antuch, W, Berndt, KD, Chavez, MA, Delfin, J, Wuethrich, K 1993The NMR solution structure of a Kunitz-type protease inhibitor from the sea anemone Stichodactyla helianthusEur J Biochem212675684CrossRefGoogle Scholar
  4. Benzinger, GR, Kyle, JW, Blumenthal, KM, Hanck, DA 1998A specific interaction between the cardiac sodium channel and site-3 toxin anthopleurin BJ Biol Chem2738084CrossRefGoogle Scholar
  5. Béress, L, Béress, R, Wunderer, G 1975Isolation and characterization of three polypeptides with neurotoxicity from Anemonia sulcataFEBS Lett50311314CrossRefGoogle Scholar
  6. Bruhn, T, Schaller, C, Schulze, C, Sanchez-Rodriguez, J, Dannmeier, C, Ravens, U, Heubach, JF, Eckhardt, K, Schmidtmayer, J, Schmidt, H, Anerios, A, Wachter, E, Béress, L 2001Isolation and characterisation of five neurotoxic and cardiotoxic polypeptides from the sea anemone Anthopleura elegantissimaToxicon39693702CrossRefGoogle Scholar
  7. Cariello, L, Santis, A, Fiore, F, Piccoli, R, Spagnuolo, A, Zanetti, L, Parente, A 1989Calitoxin, a neurotoxic peptide from the sea anemone Calliactis parasitica: amino acid sequence and electrophysiological propertiesBiochemistry2824842489CrossRefGoogle Scholar
  8. Castañeda, O, Sotolongo, V, Amor, AM, Stöklin, R, Anderson, AJ, Harvey, AL, Engström, Å, Wernstedt, C, Karlsson, E 1995Characterization of a potassium channel toxin from the Caribbean sea anemone Stichodactyla helianthusToxicon33603613CrossRefGoogle Scholar
  9. Catterall, WA, Béress, L 1978Sea anemone toxin and scorpion toxin share a common receptor site associated with the action potential sodium ionophoreJ Biol Chem25373937396Google Scholar
  10. Cordeiro, MDN, Figueiredo, SG, Valentim, ADC, Diniz, CR, Eickstedt, VR, Gilroy, J, Richardson, M 1993Purification and amino acid sequences of six Tx3 type neurotoxins from the venom of the Brazilian `armed' spider Phoneutria nigriventer (keys.)Toxicon313542CrossRefGoogle Scholar
  11. Cotton, J, Crest, M, Bouet, F, Alessandri, N, Gola, M, Forest, E, Karlsson, E, Castañeda, O, Harvey, AL, Vita, C, Ménez, A 1997A potassium-channel toxin from the sea anemone Bunodosoma granulifera, an inhibitor for Kv1 channels. Revision of the amino acid sequence, disulfide-bridge assignment, chemical synthesis, and biological activityEur J Biochem244192202CrossRefGoogle Scholar
  12. Cunha, RB, Santana, ANC, Amaral, PC, Carvalho, MDF, Carvalho, DMF, Cavalheiro, EA, Maigret, B, Ricart, CAO, Cardi, BA, Sousa, MV, Carvalho, KM 2005Primary structure, behavioral and electroencephalographic effects of an epileptogenic peptide from the sea anemone Bunodosoma cangicumToxicon45207217CrossRefGoogle Scholar
  13. Dauplais, M, Lecoq, A, Song, J, Cotton, J, Jamin, N, Gilquin, B, Roumestand, C, Vita, C, Medeiros, CL, Rowan, EG, Harvey, AL, Ménez, A 1997On the convergent evolution of animal toxins. Conservation of a diad of functional residues in potassium channel-blocking toxins with unrelated structuresJ Biol Chem27243024309Google Scholar
  14. Dias-Kadambi, BL, Drum, CL, Hanck, DA, Blumenthal, KM 1996Leucine 18, a hydrophobic residue essential for high affinity binding of anthopleurin B to the voltage-sensitive sodium channelJ Biol Chem27194229428Google Scholar
  15. Diochot, S, Schweitz, H, Béress, L, Lazdunski, M 1998Sea anemone peptides with a specific blocking activity against the fast inactivating potassium channel Kv3.4J Biol Chem27367446749CrossRefGoogle Scholar
  16. Diochot, S, Loret, E, Bruhn, T, Béress, L, Lazdunski, M 2003APETx1, a new toxin from the sea anemone Anthopleura elegantissima, blocks voltage-gated human ether-a-go-go-related gene potassium channelsMol Pharmacol645969CrossRefGoogle Scholar
  17. Diochot, S, Baron, A, Rash, LD, Deval, E, Escoubas, P, Scarzello, S, Salinas, M, Lazdunski, M 2004A new sea anemone peptide, APETx2, inhibits ASIC3, a major acid-sensitive channel in sensory neuronsEMBO J2315161525CrossRefGoogle Scholar
  18. Escoubas, P, Weille, JR, Lecoq, A, Diochot, S, Waldmann, R, Champigny, G, Moinier, D, Menez, A, Lazdunski, M 2000Isolation of a tarantula toxin specific for a class of proton-gated Na+ channelsJ Biol Chem2752511625121CrossRefGoogle Scholar
  19. Gallagher, MJ, Blumenthal, KM 1994Importance of the unique cationic residues arginine 12 and lysine 49 in the activity of the cardiotonic polypeptide anthopleurin BJ Biol Chem269254259Google Scholar
  20. Gasparini, S, Gilquin, B, Ménez, A 2004Comparison of sea anemone and scorpion toxins binding to Kv1 channels: an example of convergent evolutionToxicon43901908CrossRefGoogle Scholar
  21. Gendeh, GS, Young, LC, Medeiros, LC, Jeyaseelan, K, Harvey, AL, Chung, MCM 1997A new potassium channel toxin from the sea anemone Heteractis magnifica: isolation, cDNA cloning, and functional expressionBiochemistry361146111471CrossRefGoogle Scholar
  22. Gilquin, B, Racape, J, Wrisch, A, Visan, V, Lecoq, A, Grissmer, S, Ménez, A, Gasparini, S 2002Structure of the BgK–Kv1.1 complex based on distance restraints identified by double mutant cycles. Molecular basis for convergent evolution of Kv1 channel blockersJ Biol Chem2773740637413CrossRefGoogle Scholar
  23. Gurrola, GB, Rosati, B, Rocchetti, M, Pimienta, G, Zaza, A, Arcangeli, A, Olivotto, M, Possani, LD, Wanke, E 1999A toxin to nervous, cardiac, and endocrine ERG K+ channels isolated from Centruroides noxius scorpion venomFASEB J13953962Google Scholar
  24. Honma, T, Iso, T, Ishida, M, Nagashima, Y, Shiomi, K 2003aOccurrence of type 3 sodium channel peptide toxins in two species of sea anemones (Dofleinia armata and Entacmaea ramsayi)Toxicon41637639CrossRefGoogle Scholar
  25. Honma, T, Nagai, H, Nagashima, Y, Shiomi, K 2003bMolecular cloning of an epidermal growth factor-like toxin and two sodium channel toxins from the sea anemone Stichodactyla giganteaBiochim Biophys Acta1652103106Google Scholar
  26. Honma, T, Hasegawa, Y, Ishida, M, Nagai, H, Nagashima, Y, Shiomi, K 2005aIsolation and molecular cloning of novel peptide toxins from the sea anemone Antheopsis maculataToxicon453341CrossRefGoogle Scholar
  27. Honma, T, Minagawa, S, Nagai, H, Ishida, M, Nagashima, Y, Shiomi, K 2005bNovel peptide toxins from acrorhagi, aggressive organs of the sea anemone Actinia equinaToxicon46768774CrossRefGoogle Scholar
  28. Ishida, M, Yokoyama, A, Shimakura, K, Nagashima, Y, Shiomi, K 1997aHalcurin, a polypeptide toxin in the sea anemone Halcurias sp., with a structural resemblance to type 1 and 2 toxinsToxicon35537544CrossRefGoogle Scholar
  29. Ishida, M, Minagawa, S, Miyauchi, K, Shimakura, K, Nagashima, Y, Shiomi, K 1997bAmino acid sequences of Kunitz-type protease inhibitors from the sea anemone Actinia equinaFish Sci63794798Google Scholar
  30. Kelso, GJ, Blumenthal, KM 1998Identification and characterization of novel sodium channel toxins from the sea anemone Anthopleura xanthogrammicaToxicon364151CrossRefGoogle Scholar
  31. Kem, WR 1988

    Sea anemone toxins: structure and action

    Hessinger, DALenhoff, HM eds. The Biology of NematocystsAcademic PressNew York375405
    Google Scholar
  32. Kem, WR, Parten, B, Pennington, MW, Price, DA, Dunn, BM 1989Isolation, characterization, and amino acid sequence of a polypeptide neurotoxin occurring in the sea anemone Stichodactyla helianthusBiochemistry2834833489CrossRefGoogle Scholar
  33. Kem, WR, Pennington, MW, Dunn, BM 1990

    Sea anemone polypeptide toxins affecting sodium channels. Initial structure-activity investigations

    Hall, SStricharz, G eds. Marine Toxins. Origin, Structure and Molecular PharmacologyAmerican Chemical SocietyWashington, DC279289
    Google Scholar
  34. Khera, PK, Benzinger, GR, Lipkind, G, Drum, CL, Hanck, DA, Blumenthal, KM 1995Multiple cationic residues of anthopleurin B that determine high affinity and channel isoform discriminationBiochemistry3485338541CrossRefGoogle Scholar
  35. Korolkova, YV, Kozlov, SA, Lipkin, AV, Pluzhnikov, KA, Hadley, JK, Filippov, AK, Brown, DA, Angelo, K, Strobaek, D, Jespersen, T, Olesen, SP, Jensen, BS, Grishin, EV 2001An ERG channel inhibitor from the scorpion Buthus eupeusJ Biol Chem27698689876CrossRefGoogle Scholar
  36. Li, D, Xiao, Y, Hu, W, Xie, J, Bosmans, F, Tytgat, J, Liang, S 2003Function and solution structure of hainantoxin-I, a novel insect sodium channel inhibitor from the Chinese bird spider Selenocosmia hainanaFEBS Lett555616622Google Scholar
  37. Lin, XY, Ishida, M, Nagashima, Y, Shiomi, K 1996A polypeptide toxin in the sea anemone Actinia equina homologous with other sea anemone sodium channel toxins: isolation and amino acid sequenceToxicon345765CrossRefGoogle Scholar
  38. Loret, EP, Valle, RM, Mansuelle, P, Sampieri, F, Rochat, H 1994Positively charged amino acid residues located similarly in sea anemone and scorpion toxinsJ Biol Chem2691678516788Google Scholar
  39. Malpezzi, EL, Freitas, JC, Muramoto, K, Kamiya, H 1993Characterization of peptides in sea anemone venom collected by a novel procedureToxicon31853864CrossRefGoogle Scholar
  40. Martinez, G, Kopeyan, C, Schweitz, H, Lazdunski, M 1977Toxin III from Anemonia sulcata: primary structureFEBS Lett84247252CrossRefGoogle Scholar
  41. Metrione, RM, Schweitz, H, Walsh, KA 1987The amino acid sequence of toxin RpIII from the sea anemone, Radianthus paumotensisFEBS Lett2185962CrossRefGoogle Scholar
  42. Minagawa, S, Ishida, M, Shimakura, K, Nagashima, Y, Shiomi, K 1997Isolation and amino acid sequences of two Kunitz-type protease inhibitors from the sea anemone Anthopleura aff. xanthogrammicaComp Biochem Physiol118B381386Google Scholar
  43. Minagawa, S, Ishida, M, Nagashima, Y, Shiomi, K 1998aPrimary structure of a potassium channel toxin from the sea anemone Actinia equinaFEBS Lett427149151CrossRefGoogle Scholar
  44. Minagawa, M, Ishida, M, Shimakura, K, Nagashima, Y, Shiomi, K 1998bAmino acid sequence and biological activities of another Kunitz-type protease inhibitor from the sea anemone Anthopleura aff. xanthogrammicaFish Sci64157161Google Scholar
  45. Mouhat, S, Jouirou, B, Mosbah, A, Waard, M, Sabatier, JM 2004Diversity of folds in animal toxins acting on ion channelsBiochem J378717726CrossRefGoogle Scholar
  46. Nishida, S, Fujita, S, Warashina, A, Satake, M, Tamiya, N 1985Amino acid sequence of a sea anemone toxin from Parasicyonis actinostoloidesEur J Biochem150171173CrossRefGoogle Scholar
  47. Norton, TR 1981Cardiotonic polypeptides from Anthopleura xanthogrammica (Brandt) and A. elegantissima (Brandt)Fed Proc402125Google Scholar
  48. Norton, RS 1991Structure and structure-function relationships of sea anemone proteins that interact with the sodium channelToxicon2910511084CrossRefGoogle Scholar
  49. Oliveira, JS, Redaelli, E, Zaharenko, AJ, Cassulini, RR, Konno, K, Pimenta, DC, Freitas, JC, Clare, JJ, Wanke, E 2004Binding specificity of sea anemone toxins to Nav 1.1–1.6 sodium channels: unexpected contributions from differences in the IV/S3–S4 outer loopJ Biol Chem2793332333335CrossRefGoogle Scholar
  50. Olivera, BM, Gray, WR, Zeikus, R, McIntosh, JM, Varga, J, Rivier, J, Santos, V, Cruz, LJ 1985Peptide neurotoxins from fish-hunting cone snailsScience23013381343Google Scholar
  51. Pennington, MW, Mahnir, VM, Krafte, DS, Zaydenberg, I, Byrnes, ME, Khaytin, I, Crowley, K, Kem, WR 1996Identification of three separate binding sites on SHK toxin, a potent inhibitor of voltage-dependent potassium channels in human T-lymphocytes and rat brainBiochem Biophys Res Commun219696701CrossRefGoogle Scholar
  52. Reimer, NS, Yasunobu, CL, Yasunobu, KT, Norton, TR 1985Amino acid sequence of the Anthopleura xanthogrammica heart stimulant, anthopleurin-BJ Biol Chem26086908693Google Scholar
  53. Rogers, JC, Qu, Y, Tanada, TN, Scheuer, T, Catterall, WA 1996Molecular determinants of high affinity binding of alpha-scorpion toxin and sea anemone toxin in the S3-S4 extracellular loop in domain IV of the Na+ channel alpha subunitJ Biol Chem2711595015962Google Scholar
  54. Scheffler, JJ, Tsugita, A, Linden, G, Schweitz, H, Lazdunski, M 1982The amino acid sequence of toxin V from Anemonia sulcataBiochem Biophys Res Commun107272278CrossRefGoogle Scholar
  55. Schweitz, H, Vincent, JP, Barhanin, J, Frelin, C, Linden, G, Hugues, M, Lazdunski, M 1981Purification and pharmacological properties of eight sea anemone toxins from Anemonia sulcata, Anthopleura xanthogrammica, Stoichactis giganteus, and Actinodendron plumosumBiochemistry2052455252CrossRefGoogle Scholar
  56. Schweitz, H, Bidard, J-N, Frelin, C, Pauron, D, Vijverberg, HPM, Mahasneh, DM, Lazdunski, M, Vilbois, F, Tsugita, A 1985Purification, sequence, and pharmacological properties of sea anemone toxins from Radianthus paumotensis. A new class of sea anemone toxins acting on the sodium channelBiochemistry2435543561CrossRefGoogle Scholar
  57. Schweitz, H, Bruhn, T, Guillemare, E, Moinier, D, Lancelin, J-M, Béress, L, Lazdunski, M 1995Kalicludines and kaliseptine. Two different classes of sea anemone toxins for voltage-sensitive K+ channelsJ Biol Chem2702512125126Google Scholar
  58. Seibert, AL, Liu, J, Hanck, DA, Blumenthal, KM 2003Arg-14 loop of site 3 anemone toxins: effects of glycine replacement on toxin affinityBiochemistry421451514521CrossRefGoogle Scholar
  59. Seibert, AL, Liu, J, Hanck, DA, Blumenthal, KM 2004Role of Asn-16 and Ser-19 in anthopleurin B binding. Implications for the electrostatic nature of Na(V) site 3Biochemistry4370827089CrossRefGoogle Scholar
  60. Shiomi, K, Lin, XY, Nagashima, Y, Ishida, M 1995Isolation and amino acid sequence of polypeptide toxins in the Caribbean sea anemone Condylactis passifloraFish Sci6110161021Google Scholar
  61. Shiomi, K, Lin, XY, Nagashima, Y, Ishida, M 1996Isolationand amino acid sequence of a polypeptide toxin from the sea anemone Radianthus crispusFish Sci62629633Google Scholar
  62. Shiomi, K, Qian, WH, Lin, XY, Shimakura, K, Nagashima, Y, Ishida, M 1997Novel polypeptide toxins with crab toxicity from the sea anemone Anemonia erythraeaBiochim Biophys Acta1335191198Google Scholar
  63. Shiomi, K, Honma, T, Ide, M, Nagashima, Y, Ishida, M, Chino, M 2003An epidermal growth factor-like toxin and two sodium channel toxins from the sea anemone Stichodactyla giganteaToxicon41229236CrossRefGoogle Scholar
  64. Spagnuolo, A, Zanetti, L, Cariello, L, Piccoli, R 1994Isolation and characterization of two genes encoding calitoxins, neurotoxic peptides from Calliactis parasitica (Cnidaria)Gene138187191CrossRefGoogle Scholar
  65. Sunahara, S, Muramoto, K, Tenma, K, Kamiya, H 1987Amino acid sequence of two sea anemone toxins from Anthopleura fuscoviridisToxicon25211219CrossRefGoogle Scholar
  66. Tanaka, M, Haniu, M, Yasunobu, KT, Norton, TR 1977Amino acid sequence of the Anthopleura xanthogrammica heart stimulant anthopleurin-ABiochemistry16204208Google Scholar
  67. Vincent, JP, Balerna, M, Barhanin, J, Fosset, M, Lazdunski, M 1980Binding of sea anemone toxin to receptor sites associated with gating system of sodium channel in synaptic nerve endings in vitroProc Natl Acad Sci USA7716461650Google Scholar
  68. Waldmann, R, Lazdunski, M 1998H+-gated cation channels: neuronal acid sensors in the NaC/DEG family of ion channelsCurr Opin Neurobiol8418424CrossRefGoogle Scholar
  69. Wang, L, Ou, J, Peng, L, Zhong, X, Du, J, Liu, Y, Huang, Y, Liu, W, Zhang, Y, Dong, M, Xu, AL 2004Functional expression and characterization of four novel neurotoxins from sea anemone Anthopleura spBiochem Biophys Res Commun313163170Google Scholar
  70. Warashina, A, Ogura, T, Fujita, S 1988aBinding properties of sea anemone toxins to sodium channels in the crayfish giant axonComp Biochem Physiol90C351359Google Scholar
  71. Warashina, A, Jiang, ZY, Ogura, T 1988bPotential-dependent action of Anemonia sulcata toxins III and IV on sodium channels in crayfish giant axonsPflugers Arch4118893CrossRefGoogle Scholar
  72. Widmer, H, Wagner, G, Schweitz, H, Lazdunski, M, Wuthrich, K 1988The secondary structure of the toxin ATX Ia from Anemonia sulcata in aqueous solutiondetermined on the basis of complete sequence-specific +H-NMR assignmentsEur J Biochem171177192CrossRefGoogle Scholar
  73. Wunderer, G, Fritz, H, Wachter, E, Machleidt, W 1976Amino-acid sequence of a coelenterate toxin: toxin II from Anemonia sulcataEur J Biochem68193198CrossRefGoogle Scholar
  74. Wunderer, G, Machleidt, W, Fritz, H 1981The broad-specificity protease inhibitor 5 II from the sea anemone Anemonia sulcataMethods Enzymol80816820Google Scholar
  75. Zykova, TA, Kozlovskaya, EP 1989Amino acid sequence of neurotoxin I from the sea anemone Radianthus macrodactylusBioorg Khim1513011306Google Scholar
  76. Zykova, TA, Vinokurov, LM, Markova, LF, Kozlovskaya, EP, Elyakov, GB 1985aAmino-acid sequence of trypsin inhibitor IV from the sea anemone Radianthus macrodactylusBioorg Khim11293301Google Scholar
  77. Zykova, TA, Vinokurov, LM, Kozlovskaya, EP, Elyakov, GB 1985bAmino-acid sequence of neurotoxin III from the sea anemone Radianthus macrodactylusBioorg Khim11302310Google Scholar
  78. Zykova, TA, Kozlovskaya, EP, Elyakov, GB 1988aAmino acid sequence of neurotoxin II from the sea anemone Radianthus macrodactylusBioorg Khim14878882Google Scholar
  79. Zykova, TA, Kozlovskaia, EP, Eliakov, GB 1988bAmino acid sequence of neurotoxins IV and V from the sea anemone Radianthus macrodactylusBioorg Khim1414891494Google Scholar

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  1. 1.Department of Food Science and TechnologyTokyo University of Marine Science and TechnologyTokyoJapan

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