Inhibition of ACh release at an Aplysia synapse by neurotoxic phospholipases A2: specific receptors and mechanisms of action

The Journal of Physiology
P FossierG Baux

Abstract

1. Monochain (OS2) and multichain (taipoxin) neurotoxic phospholipases A2 (PLA2), purified from taipan snake venom, both inhibited ACh release at a concentration of 20 nM (90% inhibition in 2 h) at an identified synapse from buccal ganglion of Aplysia californica. 2. The Na+ current was unchanged upon application of either OS2 or taipoxin. Conversely, presynaptic K+ currents (IA and IK) were increased by taipoxin but not by OS2. In addition, OS2 induced a significant decrease of the presynaptic Ca2+ current (30%) while taipoxin increased this latter current by 20-30%. 3. Bee venom PLA2, another monochain neurotoxic PLA2, also inhibited ACh release while non-toxic enzymatically active PLA2s like OS1 (also purified from taipan snake venom) or porcine pancreatic PLA2 elicited a much weaker inhibition of ACh release, suggesting a specific action of neurotoxic PLA2s versus non-toxic PLA2s on ACh release. 4. Using iodinated OS2, specific high affinity binding sites with molecular masses of 140 and 18 kDa have been identified on Aplysia ganglia. The maximal binding capacities were 55 and 300-400 fmol (mg protein)-1 for membrane preparations from whole and buccal ganglia, respectively. These binding sites are of high affinity for neuro...Continue Reading

Citations

Apr 5, 2003·Journal of Neurochemistry·Patricia NecoLuis M Gutiérrez
Sep 13, 2002·American Journal of Physiology. Cell Physiology·Christopher C SillimanAnirban Banerjee
Jan 27, 1999·Toxicon : Official Journal of the International Society on Toxinology·B G Fry

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