The neurotoxic lipopeptide kalkitoxin interacts with voltage-sensitive sodium channels in cerebellar granule neurons.
The marine neurotoxin kalkitoxin, a thiazoline-containing lipid derived from the pantropical marine cyanobacterium Lyngbya majuscula, was assayed for interaction with the tetrodotoxin-sensitive, voltage-sensitive sodium channel (TTX-VSSC) in cerebellar granule neuron cultures (CGN). The naturally occurring isomer of kalkitoxin (KTx-7) blocked veratridine-induced (30 microM) neurotoxicity in a concentration-dependent manner (EC50 22.7 nM [9.5-53.9 nM, 95% confidence interval {CI}]) in CGN. Kalkitoxin was a potent inhibitor (EC50 26.1 nM [12.3-55.0 nM, 95% CI]) of the elevation of intracellular Ca2+ concentration [Ca2+](i) that accompanies exposure of CGN to veratridine. To further explore the potential interaction of KTx-7 with TTX-VSSC, we assessed the influence of KTX-7 on the binding of [3H]batrachotoxin ([3H]BTX) to neurotoxin site 2 on the TTX-VSSC. Although kalkitoxin was without effect on the basal binding of [3H]BTX to intact cerebellar granule neurons, in the presence of the positive allosteric modulator, deltamethrin, [3H]BTX binding was inhibited by KTx-7 in a concentration-dependent manner (11.9 nM [IC50=3.8-37.2 nM, 95% CI]). These results provide both direct and functional evidence for an interaction of kalkitoxin with the neuronal TTX-VSSC.
LePage
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KT
Department of Physiology and Pharmacology, College of Veterinary Medicine, The University of Georgia, Room 2223, Athens, GA 30601, USA. klepage@vet.uga.edu
Goeger
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Yokokawa
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Asano
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Shioiri
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Gerwick
W H
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Murray
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D000818:Animals; D000831:Animals, Newborn; D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002525:Cerebellar Cortex / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008055:Lipids / Q000633:toxicity*; D008387:Marine Toxins / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000633:toxicity*; D009570:Nitriles / Q000494:pharmacology; D011722:Pyrethrins / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D026941:Sodium Channel Blockers / Q000633:toxicity; D015222:Sodium Channels / Q000187:drug effects*; D013844:Thiazoles / Q000633:toxicity*; D014701:Veratridine / Q000633:toxicity
D004338:Drug Combinations; D008055:Lipids; D008387:Marine Toxins; D009498:Neurotoxins; D009570:Nitriles; D011722:Pyrethrins; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013844:Thiazoles; C017180:decamethrin; D014701:Veratridine; C121885:kalkitoxin; D007770:L-Lactate Dehydrogenase; D002118:Calcium