Antibodies having markedly different effects on enzymatic activity and induction of acetylcholine release by two presynaptically-acting phospholipase A2 neurotoxins.
The enzymatic and acetylcholine-releasing activities of two presynaptically-acting phospholipase A2 neurotoxins (pseudexin B and scutoxin) were studied in a synaptosomal fraction. Scutoxin (100 nM) induced greater [14C]acetylcholine release than did pseudexin B (100 nM). Both toxins caused fatty acid production in the synaptosomal fraction, although pseudexin B was more active than scutoxin. One monoclonal antibody raised against pseudexin B (#4) had no effect on the enzymatic activity of either pseudexin B or scutoxin. Two other monoclonal antibodies (#3 and #7), also raised against pseudexin B, antagonized the enzymatic activity of pseudexin B and scutoxin. Monoclonal antibody #3 was more effective than #7 in reducing the amount of acetylcholine released by the toxins, whereas #7 was more effective than #3 in reducing fatty acid production. Although antibody #3 caused complete inhibition of phospholipase A2 activity of pseudexin B on purified substrates, it only reduced phospholipase A2 activity by 35% in synaptosomes. These findings support the hypothesis that gross phospholipase A2 activity does not play a role in stimulation of acetylcholine release by the presynaptically-acting phospholipase A2 neurotoxins.
Fletcher
J E
JE
Department of Anesthesiology, Hahnemann University, Philadelphia, PA 19102-1192.
Jiang
M S
MS
Middlebrook
J L
JL
D000109:Acetylcholine / Q000096:biosynthesis*; D000818:Animals; D000906:Antibodies / Q000494:pharmacology*; D001923:Brain Chemistry; D004546:Elapid Venoms / Q000276:immunology / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005227:Fatty Acids / Q000032:analysis; D051379:Mice; D009498:Neurotoxins / Q000276:immunology / Q000494:pharmacology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D013574:Synaptosomes / Q000187:drug effects
D000906:Antibodies; D004546:Elapid Venoms; D005227:Fatty Acids; D009498:Neurotoxins; C026235:Pseudechis venom; C068736:scutoxin A; D010741:Phospholipases A; D054467:Phospholipases A2; D000109:Acetylcholine