Synaptosomal glutamate release induced by the fraction Bc2 from the venom of the sea anemone Bunodosoma caissarum

Abstract

The effect of a fraction (Bc2) from the venom of the sea anemone Bunodosoma caissarum on [3H]glutamate release from rat cortical synaptosomes was investigated. Bc2 (2-20 microg/ml) provoked massive glutamate release without causing synaptosome disruption. Glutamate release stimulated by Bc2 was independent of extracellular Ca2+ and of voltage-sensitive Na+ channels, and it was completely abolished by the addition of sphingomyelin. No definitive evidence about the mechanism underlying the stimulatory effect of Bc2 is available as yet. However, a direct interaction with the exocytotic machinery cannot be ruled out.

The Sea Anemone Toxin Bc2 Induces Continuous or Transient Exocytosis, in the Presence of Sustained Levels of High Cytosolic Ca2+ in Chromaffin Cells

“…Amperometry in intact cells provides a good alternative to study the sustained component of quantal release and the mechanism of action of new toxins that could help to understand better the early exocytotic process. We found that Bc2 (0.6 nM) is able to release rapidly about 900 vesicles in a time of approximately 70 s; this effect was irreversible but it is not related to cell damage since lactate dehydrogenase measurements performed under the same experimental conditions as described here remained unaltered in comparison to control (data not shown) and also previously observed (20). We have fitted the exocytotic rate curve to a single exponential with a time constant of 10.5 s, faster than the time constant calculated for the fast exocytotic component induced by prolonged depolarization with 70 mM K ϩ ( ϭ 15.1) where 228 vesicles are rapidly released.…”

“…Materials and Solutions-Bc2 was purified from the Brazilian sea anemone B. caissarum mucus as described previously (20). The toxin was kept in aliquots (0.1 mM) at Ϫ20°C and then further diluted, as needed, on the day of use.…”

“…More recently, we have seen that Bc2 (20 kDa), the main cytolysin present in the brazilian sea anemone Bunodosoma caissarum, induces extensive glutamate release from rat cortical synaptosomes (20). This effect was independent of extracellular Ca 2ϩ and Na ϩ and was inhibited by the lipid sphingomyelin, a classical inhibitor of the sea anemone cytolysins activity.…”

Developmental Biology of Neoplastic Growth

“…The pore formed is likely to allow diffusion of small molecules ranging from 400 to 900 Da and cations such as Ca 2+ . Bc2 (20 kDa), isolated from the sea anemone Bunodosoma caissarum, was shown to promote glutamate release from rat cortical synaptosomes (Migues et al 1999) and catecholamine release from bovine chromaffin cells (Ales et al 2000). Most interestingly, the effect of this toxin was reversible by simple washing, suggesting the specific and reversible nature of the pore formed.…”

Behavioral and electroencephalographic analysis of seizures induced by intrahippocampal injection of granulitoxin, a neurotoxic peptide from the sea anemone Bunodosoma granulifera

“…The cardiac stimulant type 1 peptides, such as anthopleurin-A, anthopleurin-B and anemone toxin (ATX-II), have been well studied and their possible useful applications as therapeutic agents with a combination of positive inotropic and antiarrhythmic activities in human heart diseases have been suggested (4,7). The pharmacological effects of some anemone peptides on the nervous system have also been studied, such as the effect of a central stimulant substance isolated from the sea anemone Stoichactis kenti on mouse brain monoamines (8), the potent excitatory effect of anthopleurin-B on frog spinal cord (9), the possible application of ShI as an insecticide based on its negligible mammalian neurotoxicity as compared to its potent neurotoxicity in crustacea (4,10), the ATX-II-induced increase in persistent sodium current and its effects on the firing properties of rat neocortical pyramidal neurones (11), and the synaptosomal glutamate release induced by fraction Bc2 from the sea anemone Bunodosoma caissarum venom (12).…”