Selective block of Ca²⁺‐dependent K⁺ current in crayfish neuromuscular system and chromaffin cells by sea anemone Bunodosoma cangicum venom

Abstract

The effects of the nematocyst venom of the sea anemone Bunodosoma cangicum on depolarization‐activated currents were studied in opener crayfish muscle fibers and in cultured bovine chromaffin cells. The venom selectively and reversibly blocked the Ca2+ ‐dependent K+ current (IK(Ca)) present in crayfish muscle in a dose‐dependent manner without affecting voltage‐gated Ca2+ or K+ currents. Furthermore, the venom also reduced IK(Ca) in chromaffin cells, without modifying voltage‐gated Na+, Ca2+, or K+ currents. Synaptic transmission in crayfish muscle was also affected by the venom. Repetitive excitatory and inhibitory postsynaptic currents (each associated with a presynaptic action potential) were evoked by each nerve stimulus, suggesting that presynaptic IK(Ca) may control the electrical activity of excitatory and inhibitory presynaptic fibers. We conclude that B. cangicum venom includes a toxin that selectively and reversibly blocks Ca2+ ‐dependent K+ currents in crayfish muscle and in bovine chromaffin cells, and modifies excitatory and inhibitory synaptic transmission, probably abolishing a similar conductance at the presynaptic fibers. © 1995 Wiley‐Liss, Inc.

Identification of hemolytic and neuroactive fractions in the venom of the sea anemone Bunodosoma cangicum

“…Data reported by Araque et al (15) demonstrated that the venom obtained from the same anemone includes a toxin that selectively blocks the Ca 2+ -dependent K + currents in a reversible manner without modifying the Na + currents. Moreover, Harvey et al (13) demonstrated that the venom of the same anemone blocks the binding of labeled DTX (a known K + channel blocker) to synaptosomal preparations.…”

“…Araque et al (15), using mammalian chromaffin cells, demonstrated that the whole venom of B. cangicum had no effects on Na + or K + currents. However, our results clearly show that the Bcg-3 fraction modified these currents in an invertebrate nerve preparation.…”

“…Its venom selectively blocks the Ca 2+ -dependent K + current (I K(Ca) ) present in crayfish muscle fibers in a reversible manner without affecting voltage-gated Ca 2+ or K + currents (15). Furthermore, the venom reduces I K(Ca) in chromaffin cells without modifying voltage-gated Na + , Ca 2+ or K + currents (15). The venom also inhibits the binding of radiolabeled DTX to synaptosomal membranes (13).…”

“…The venom also inhibits the binding of radiolabeled DTX to synaptosomal membranes (13). Although these studies (13,15) described interesting neuroactive effects of whole venom, no attempt was made to purify the toxin(s) responsible for such actions on ionic channels. Furthermore, the presence of cytolytic toxins in the venom has not been explored previously.…”

Caracterização do efeito do BDS 391, um composto analgésico, sobre receptores 5-HT3 e canais iônicos.

“…As anêmonas do mar utilizam rico complexo proteico para capturar suas presas e se defender de predadores. A peçonha destes animais contem neurotoxinas (3-5 kDa), com ação em canais iônicos específicos, e hemolisinas (18)(19)(20), que atuam formando poros em membranas. No entanto, pouco se conhece sobre a atividade biológica de substâncias de baixo peso molecular isoladas da peçonha destes animais.…”