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Selective presynaptic insectotoxin (alpha-latroinsectotoxin) isolated from black widow spider venom
L G Magazanik1, I M Fedorova, G I Kovalevskaya
1Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the U.S.S.R., Leningrad.
Neuroscience
|January 1, 1992
Summary
Alpha-latroinsectotoxin from black widow spider venom potently affects insect nerve function but not frog nerve function. Its action on insects shares similarities with alpha-latrotoxin
Area of Science:
- Neuroscience
- Toxicology
- Biochemistry
Background:
- Black widow spider venom contains potent neurotoxins.
- Alpha-latrotoxin affects vertebrate neuromuscular junctions.
- Insect neuromuscular junctions represent a distinct system for toxin study.
Purpose of the Study:
- To investigate the effects of alpha-latroinsectotoxin on insect neuromuscular preparations.
- To compare the action of alpha-latroinsectotoxin in insects with alpha-latrotoxin in vertebrates.
- To elucidate the binding and presynaptic mechanisms of alpha-latroinsectotoxin.
Main Methods:
- Isolation and purification of alpha-latroinsectotoxin.
- Electrophysiological recordings of miniature excitatory postsynaptic potentials in insect larvae.
- Binding assays using radiolabeled toxins and membrane preparations.
- Investigation of cation dependency and effects of concanavalin A.
Main Results:
- Alpha-latroinsectotoxin (4 nM) significantly increased excitatory postsynaptic potential frequency in insect larvae.
- Alpha-latroinsectotoxin did not affect transmitter release in frog nerve endings.
- Toxin binding was saturable and specific, with presynaptic effects dependent on divalent cations (Mg2+ substituting for Ca2+).
- Concanavalin A pretreatment abolished both binding and presynaptic effects in insects.
Conclusions:
- Alpha-latroinsectotoxin exhibits selective presynaptic activity in insects, distinct from its lack of effect on vertebrates.
- The mechanism of action shares similarities with alpha-latrotoxin, suggesting conserved presynaptic modulation.
- Selectivity is likely due to differences in neurotoxin receptor structures between insect and vertebrate nerve endings.