8.B.6 The Ca²⁺Channel-targeting Spider Toxin (CST) Family

A novel polypeptide, designated omega-Lsp-IA, which modulates P-type Ca²⁺ channels, has been purified from the venom of the spider Geolycosa sp. omega-Lsp-IA contains 47 amino acid residues and 4 intramolecular disulfide bridges (Pluzhnikov et al., 2007). It belongs to a group of spider toxins affecting Ca²⁺ channels and may form the inhibitor cystine knot (ICK) fold. A cluster of positively charged residues in the C-terminal loop of the peptide and a regular distribution of hydrophobic residues may play a role in its mechanism of action. At saturating concentration (10nM), the peptide clearly slows down the activation kinetics and partially inhibits the amplitude of P-current in rat cerebellar Purkinje neurons. Prominent deceleration of the activation kinetics is manifested as the appearance of a five-fold slower component of the current activation. Omega-Lsp-IA shows differing effects on different Ca²⁺ channel types. Omega-Agatoxin IVA completely removed the effect of omega-Lsp-IA on the whole-cell Ca²⁺ current. Omega-Lsp-IA appears to act specifically on P-type Ca²⁺channels (Pluzhnikov et al., 2007).

δ-atracotoxin isoforms (δ-ACTX; 8.B.6.3.1) bind to voltage-gated sodium channels in the same way as classical scorpion alpha-toxins. According to the 'voltage-sensor trapping model', delta-ACTX isoforms interact with the voltage sensor S4 transmembrane segment of alpha-subunit domain IV, thereby preventing its normal outward movement and concurrent conformational changes required for inactivation of the channel. As a consequence, prolonged action potentials at autonomic or somatic synapses induce massive transmitter release, resulting in clinical correlates of neuroexcitation (e.g., muscle fasciculation, spasms, paresthesia, tachycardia and diaphoresis) (Luch 2010).

This family belongs to the Huwentoxin Superfamily.

References:

Chong, Y., J.L. Hayes, B. Sollod, S. Wen, D.T. Wilson, P.G. Hains, W.C. Hodgson, K.W. Broady, G.F. King, and G.M. Nicholson. (2007). The omega-atracotoxins: selective blockers of insect M-LVA and HVA calcium channels. Biochem Pharmacol 74: 623-638.

Corzo, G., P. Escoubas, E. Villegas, I. Karbat, D. Gordon, M. Gurevitz, T. Nakajima, and N. Gilles. (2005). A spider toxin that induces a typical effect of scorpion α-toxins but competes with β-toxins on binding to insect sodium channels. Biochemistry 44: 1542-1549.

Corzo, G., P. Escoubas, M. Stankiewicz, M. Pelhate, C.P. Kristensen, and T. Nakajima. (2000). Isolation, synthesis and pharmacological characterization of δ-palutoxins IT, novel insecticidal toxins from the spider Paracoelotes luctuosus (Amaurobiidae). Eur J Biochem 267: 5783-5795.

Khan, S.A., Y. Zafar, R.W. Briddon, K.A. Malik, and Z. Mukhtar. (2006). Spider venom toxin protects plants from insect attack. Transgenic Res 15: 349-357.

Luch, A. (2010). Mechanistic insights on spider neurotoxins. EXS. 100: 293-315.

Pluzhnikov, K., A. Vassilevski, Y. Korolkova, A. Fisyunov, O. Iegorova, O. Krishtal, and E. Grishin. (2007). omega-Lsp-IA, a novel modulator of P-type Ca²⁺ channels. Toxicon. 50: 993-1004.

Trachsel, C., D. Siegemund, U. Kämpfer, L.S. Kopp, C. Bühr, J. Grossmann, C. Lüthi, M. Cunningham, W. Nentwig, L. Kuhn-Nentwig, S. Schürch, and J. Schaller. (2012). Multicomponent venom of the spider Cupiennius salei: a bioanalytical investigation applying different strategies. FEBS J. 279: 2683-2694.

Wang, X., R. Smith, J.I. Fletcher, H. Wilson, C.J. Wood, M.E. Howden, and G.F. King. (1999). Structure-function studies of omega-atracotoxin, a potent antagonist of insect voltage-gated calcium channels. Eur J Biochem 264: 488-494.

Yamaji, N., M.J. Little, H. Nishio, B. Billen, E. Villegas, Y. Nishiuchi, J. Tytgat, G.M. Nicholson, and G. Corzo. (2009). Synthesis, solution structure, and phylum selectivity of a spider δ-toxin that slows inactivation of specific voltage-gated sodium channel subtypes. J. Biol. Chem. 284: 24568-24582.

Examples:

TC#

Name

Organismal Type

Example

8.B.6.1.1

Ω-agatoxin IVA

Spiders

Ω-agatoxin IVA of Agelenopsis aperta (P30288)

8.B.6.1.2

Mu-agatoxin II (37aas)

Spiders

Mu-agatoxin II of Agelenopsis aperta (P11058)

8.B.6.1.3

Mu-agatoxin-Hc1a (Curtatoxin-1) (36aas)

Spiders

Curtatoxin-1 of Hololena curta (P15967)

8.B.6.1.4

U10-Ctenitoxin-Co1a of 37 aas (Trachsel et al. 2012).

Animals

Ctentitoxin of Ctenus ornatus (Oligoctenus ornatus; brazilian spider)

8.B.6.1.5

Putative toxin of 148 aas

Animals

Putative toxin of Tribolium castaneum (red flour beetle)

8.B.6.1.6

U3-Agatoxin Ao1h of 69 aas

Spiders

Agatoxin of Agelena orientalis

8.B.6.1.7

U2-agatoxin Ao1k of 69 aas. Insect active toxin causing rapid but reversible paralysis in crickets. No activity shown in mammals. Does not show effect on mammalian voltage-gated calcium channels.

Spiders

Agatoxin of Agelena orientalis

8.B.6.1.8

Tachystatin-B1 of 42 aas. Exhibits stronger antimicrobial activity against Gram-positive bacteria (S. aureus (IC50 is 7.4 µg/ml)), fungi (C. albicans (IC50 is 3.0 µg/ml) and P. pastoris (IC50 is 0.1 µg/ml)) than Gram-negative bacteria (E.coli, no inhibition at 100 µg/ml). Binds to chitin. Does not cause hemolysis on sheep erythrocytes. Has no blocking activity on the P-type calcium channel.

Animals (crabs)

Tachystatin of Tachypleus tridentatus (Japanese horseshoe crab)

8.B.6.1.9

Delta (δ)-amaurobitoxin-Pl1b of 27 aas and 0 TMSs. Insecticidal toxin. Lethal to lepidopteran larvae. No adverse affect is observed when intracerebroventricularly injected in mice at a dose of 0.2 μg but causes reversible paralysis of legs when injected intracerebroventricularly in mice at a dose of 2.0 μg. Binds to site 4 of insect voltage-gated sodium channel (Nav) and inhibits channel inactivation (Corzo et al. 2000; Corzo et al. 2005).

Amaurobitoxin of Pireneitega luctuosa (Tangled nest spider) (Paracoelotes luctuosus)

Examples:

TC#

Name

Organismal Type

Example

8.B.6.2.1

Delta atracotoxin-Hv1a (Versutoxin) (42aas) (NMR structure available (1VTXA)). Antagonist of insect voltage-gated calcium channels (Chong et al., 2007; Khan et al., 2006; Wang et al., 1999) as well as sodium channels (Luch 2010).

Spiders

Versutoxin of Hadronyche versuta (P13494)

8.B.6.2.2

Delta hexatoxin-Mg1a; Neurotoxin Magi-4 (105aas). Targets sites 3 and 4 of mammalian Na⁺channels; slows inactivation (Yamaji et al., 2009).

Spiders

Neurotoxin Magi-4 of Macrothele gigas (P83560)

8.B.6.2.3

U17-barytoxin-Tl1a; U17-BATX-Tl1a; Toxin ICK-35 of 114 aas with one N-terminal TMS.

U17-BATX-TI1a of Trittame loki

Examples:

TC#

Name

Organismal Type

Example