Tityustoxin K Alpha Blocks Voltage-gated Noninactivating K+ Channels and Unblocks Inactivating K+ Channels Blocked by Alpha-dendrotoxin in Synaptosomes

Overview

Journal Proc Natl Acad Sci U S A

Specialty Science

Date 1994 Feb 15

PMID 7509073

Citations 13

Authors

R S Rogowski

B K Krueger

J H COLLINS

M P Blaustein

Affiliations

Soon will be listed here.

Abstract

Two nonhomologous polypeptide toxins, tityustoxin K alpha (TsTX-K alpha) and tityustoxin K beta (TsTX-K beta), purified from the venom of the Brazilian scorpion Tityus serrulatus, selectively block voltage-gated noninactivating K+ channels in synaptosomes (IC50 values of 8 nM and 30 nM, respectively). In contrast, alpha-dendrotoxin (alpha-DTX) and charybdotoxin (ChTX) block voltage-gated inactivating K+ channels in synaptosomes (IC50 values of 90 nM and 40 nM, respectively). We studied interactions among these toxins in 125I-alpha-DTX binding and 86Rb efflux experiments. Both TsTX-K alpha and ChTX completely displaced specifically bound 125I-alpha-DTX from synaptic membranes, but TsTX-K beta had no effect on bound alpha-DTX. TsTX-K alpha and TsTX-K beta blocked the same noninactivating component of 100 mM K(+)-stimulated 86Rb efflux in synaptosomes. Both alpha-DTX and ChTX blocked the same inactivating component of the K(+)-stimulated 86Rb efflux in synaptosomes. Both the inactivating and the noninactivating components of the 100 mM K(+)-stimulated 86Rb efflux were completely blocked when 200 nM TsTX-K beta and either 600 nM alpha-DTX or 200 nM ChTX were present. The effects of TsTX-K alpha and ChTX on 86Rb efflux were also additive. When TsTX-K alpha was added in the presence of alpha-DTX, however, only the noninactivating component of the K(+)-stimulated efflux was blocked. The inactivating component could then be blocked by ChTX, which is structurally homologous to TsTX-K alpha. We conclude that TsTX-K alpha unblocks the voltage-gated inactivating K+ channels in synaptosomes when they are blocked by alpha-DTX, but not when they are blocked by ChTX. TsTX-K alpha binds to a site on the inactivating K+ channel that does not occlude the pore; its binding apparently prevents alpha-DTX (7054 Da), but not ChTX (4300 Da), from blocking the pore. The effects of TsTX-K alpha on 125I-alpha-DTX binding and 86Rb efflux are mimicked by noxiustoxin, which is homologous to TsTX-K alpha and ChTX.

Citing Articles

The First K-Channel Blocker Described from Venom: The Purification, Molecular Cloning, and Functional Characterization of α-KTx4.9 (Tf5).

Monteiro I, Araujo I, Camargos T, Ortiz E, Souza A, Lima J Toxins (Basel). 2025; 17(2).

PMID: 39998113 PMC: 11861696. DOI: 10.3390/toxins17020096.

Effects of Brazilian scorpion venoms on the central nervous system.

Abrahao Nencioni A, Neto E, Freitas L, Dorce V J Venom Anim Toxins Incl Trop Dis. 2018; 24:3.

PMID: 29410679 PMC: 5781280. DOI: 10.1186/s40409-018-0139-x.

Partial purification and functional characterization of Ts19 Frag-I, a novel toxin from Tityus serrulatus scorpion venom.

Lima P, Bordon K, Pucca M, Cerni F, Zoccal K, Faccioli L J Venom Anim Toxins Incl Trop Dis. 2015; 21:49.

PMID: 26628901 PMC: 4666072. DOI: 10.1186/s40409-015-0051-6.

The Mediterranean scorpion Mesobuthus gibbosus (Scorpiones, Buthidae): transcriptome analysis and organization of the genome encoding chlorotoxin-like peptides.

Diego-Garcia E, Caliskan F, Tytgat J BMC Genomics. 2014; 15:295.

PMID: 24746279 PMC: 4234519. DOI: 10.1186/1471-2164-15-295.

Electrophysiological characterization of Ts6 and Ts7, K⁺ channel toxins isolated through an improved Tityus serrulatus venom purification procedure.

Cerni F, Pucca M, Peigneur S, Cremonez C, Bordon K, Tytgat J Toxins (Basel). 2014; 6(3):892-913.

PMID: 24590385 PMC: 3968367. DOI: 10.3390/toxins6030892.

References

Miller C, Moczydlowski E, Latorre R, Phillips M . Charybdotoxin, a protein inhibitor of single Ca2+-activated K+ channels from mammalian skeletal muscle. Nature. 1985; 313(6000):316-8. DOI: 10.1038/313316a0. View

Bartschat D, Blaustein M . Potassium channels in isolated presynaptic nerve terminals from rat brain. J Physiol. 1985; 361:419-40. PMC: 1192867. DOI: 10.1113/jphysiol.1985.sp015653. View

Harvey A, Anderson A . Dendrotoxins: snake toxins that block potassium channels and facilitate neurotransmitter release. Pharmacol Ther. 1985; 31(1-2):33-55. DOI: 10.1016/0163-7258(85)90036-1. View

Valdivia H, Smith J, Martin B, Coronado R, Possani L . Charybdotoxin and noxiustoxin, two homologous peptide inhibitors of the K+ (Ca2+) channel. FEBS Lett. 1988; 226(2):280-4. DOI: 10.1016/0014-5793(88)81439-x. View

Gimenez-Gallego G, Navia M, Reuben J, KATZ G, Kaczorowski G, Garcia M . Purification, sequence, and model structure of charybdotoxin, a potent selective inhibitor of calcium-activated potassium channels. Proc Natl Acad Sci U S A. 1988; 85(10):3329-33. PMC: 280202. DOI: 10.1073/pnas.85.10.3329. View

Chicchi G, Gimenez-Gallego G, Ber E, Garcia M, Winquist R, Cascieri M . Purification and characterization of a unique, potent inhibitor of apamin binding from Leiurus quinquestriatus hebraeus venom. J Biol Chem. 1988; 263(21):10192-7. View

Benishin C, Sorensen R, Brown W, Krueger B, Blaustein M . Four polypeptide components of green mamba venom selectively block certain potassium channels in rat brain synaptosomes. Mol Pharmacol. 1988; 34(2):152-9. View

Moczydlowski E, Lucchesi K, Ravindran A . An emerging pharmacology of peptide toxins targeted against potassium channels. J Membr Biol. 1988; 105(2):95-111. DOI: 10.1007/BF02009164. View

Schneider M, Rogowski R, Krueger B, Blaustein M . Charybdotoxin blocks both Ca-activated K channels and Ca-independent voltage-gated K channels in rat brain synaptosomes. FEBS Lett. 1989; 250(2):433-6. DOI: 10.1016/0014-5793(89)80771-9. View

10.

Schweitz H, Stansfeld C, Bidard J, Fagni L, Maes P, Lazdunski M . Charybdotoxin blocks dendrotoxin-sensitive voltage-activated K+ channels. FEBS Lett. 1989; 250(2):519-22. DOI: 10.1016/0014-5793(89)80788-4. View

11.

Lucchesi K, Ravindran A, Young H, Moczydlowski E . Analysis of the blocking activity of charybdotoxin homologs and iodinated derivatives against Ca2+-activated K+ channels. J Membr Biol. 1989; 109(3):269-81. DOI: 10.1007/BF01870284. View

12.

Sorensen R, Blaustein M . Rat brain dendrotoxin receptors associated with voltage-gated potassium channels: dendrotoxin binding and receptor solubilization. Mol Pharmacol. 1989; 36(5):689-98. View

13.

Dreyer F . Peptide toxins and potassium channels. Rev Physiol Biochem Pharmacol. 1990; 115:93-136. View

14.

Galvez A, Gimenez-Gallego G, Reuben J, Feigenbaum P, Kaczorowski G, Garcia M . Purification and characterization of a unique, potent, peptidyl probe for the high conductance calcium-activated potassium channel from venom of the scorpion Buthus tamulus. J Biol Chem. 1990; 265(19):11083-90. View

15.

Sugg E, Garcia M, Reuben J, PATCHETT A, Kaczorowski G . Synthesis and structural characterization of charybdotoxin, a potent peptidyl inhibitor of the high conductance Ca2(+)-activated K+ channel. J Biol Chem. 1990; 265(31):18745-8. View

16.

Mackinnon R, Heginbotham L, Abramson T . Mapping the receptor site for charybdotoxin, a pore-blocking potassium channel inhibitor. Neuron. 1990; 5(6):767-71. DOI: 10.1016/0896-6273(90)90335-d. View

17.

Hurst R, Busch A, Kavanaugh M, Osborne P, North R, Adelman J . Identification of amino acid residues involved in dendrotoxin block of rat voltage-dependent potassium channels. Mol Pharmacol. 1991; 40(4):572-6. View

18.

Stocker M, Pongs O, Hoth M, Heinemann S, Stuhmer W, Schroter K . Swapping of functional domains in voltage-gated K+ channels. Proc Biol Sci. 1991; 245(1313):101-7. DOI: 10.1098/rspb.1991.0094. View

19.

Blaustein M, Rogowski R, Schneider M, Krueger B . Polypeptide toxins from the venoms of Old World and New World scorpions preferentially block different potassium channels. Mol Pharmacol. 1991; 40(6):932-42. View

20.

Crest M, Jacquet G, Gola M, Zerrouk H, Benslimane A, Rochat H . Kaliotoxin, a novel peptidyl inhibitor of neuronal BK-type Ca(2+)-activated K+ channels characterized from Androctonus mauretanicus mauretanicus venom. J Biol Chem. 1992; 267(3):1640-7. View