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Black widow spider toxin-induced calcium fluxes and transmitter release in a neurosecretory cell line
Abstract:
Several polypeptide neurotoxins affect presynaptic functions by interfering with chemical neurotransmission. This group of toxins includes botulinum toxin, tetanus toxin, beta-bungaro-toxin and black widow spider toxin (BWSTx). While the effect of the first three toxins is mainly a rapid and severe block of neurotransmitter release, BWSTx affects transmission by a massive stimulation of mediator release. Despite various hypotheses put forward to explain the action of BWSTx at the level of nerve terminals, there is still a considerable degree of uncertainty as to the cation dependence of venom action. Study of the toxin mode of action at the biochamical level has been hampered by the complexity and cellular heterogeneity of the preparations used, neuromuscular junction or synaptosomes. PC12 cell line, derived from a rat phaeochromocytoma, seems to be an excellent model in view of its property of synthesising and storing noradrenaline, dopamine and acetylcholine, and releasing them in depolarising conditions. We have recently shown that highly purified BWSTx stimulates secretion from PC12 cells of previously taken up radioactive dopamine (DA) and noradrenaline (NA) (ref. 14 and manuscript in preparation). We report here that the earliest detectable event after toxin treatment of such cells is a massive increase of cytosolic calcium.
Insights
Black widow spider toxin (BWSTx) triggers massive neurotransmitter release by causing a rapid surge in intracellular calcium. This study utilizes PC12 cells to investigate the early biochemical events underlying BWSTx neurotoxicity.
Area of Science:
- Neuroscience
- Biochemistry
- Toxicology
Background:
- Several neurotoxins, including botulinum and tetanus toxins, disrupt presynaptic function and chemical neurotransmission.
- Black widow spider toxin (BWSTx) uniquely stimulates mediator release, unlike other neurotoxins that primarily block neurotransmitter release.
- Understanding BWSTx's mechanism is challenging due to the complexity of traditional models like neuromuscular junctions and synaptosomes.
Purpose of the Study:
- To investigate the cation dependence and biochemical mechanisms of BWSTx action at the nerve terminal level.
- To utilize the PC12 cell line, a well-characterized model for neurotransmitter synthesis and release, to study BWSTx.
- To identify the earliest cellular events following BWSTx exposure in a controlled cellular model.
Main Methods:
- Utilized the PC12 cell line, derived from rat phaeochromocytoma, known for synthesizing and releasing catecholamines and acetylcholine.
- Administered highly purified BWSTx to PC12 cells previously loaded with radioactive dopamine (DA) and noradrenaline (NA).
- Monitored cytosolic calcium levels as an early indicator of cellular response to BWSTx treatment.
Main Results:
- BWSTx treatment of PC12 cells induced the secretion of previously uptaken radioactive dopamine and noradrenaline.
- The earliest detectable event following BWSTx exposure in PC12 cells was a significant increase in cytosolic calcium.
- This massive calcium influx is proposed as a key initial step in BWSTx-mediated neurotransmitter release.
Conclusions:
- The PC12 cell line provides a suitable model for studying the biochemical effects of BWSTx.
- BWSTx-induced neurotransmitter release is preceded by a substantial rise in intracellular calcium levels.
- The findings suggest that calcium mobilization is a critical early event in the mechanism of action of black widow spider venom.