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Maitotoxin, a cationic channel activator
L I Escobar1, C Salvador, M Martínez
1Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, México, D.F.
Abstract:
Maitotoxin (MTX), a water soluble polyether obtained from the marine dinoflagellate Gambierdiscus toxicus is one of the entities responsible for Ciguatera, a form of seafood poisoning. This toxin is a potent activator of changes in the intracellular Ca2+ concentrations of cells from a wide variety of organisms. Evidence published in the last few years strongly suggests that this toxin has no ionophoretic activity. Molecular mechanics studies, shown for the first time in this review, models MTX as a molecular 'wire'. The present work compiles the few studies developed with electrophysiological techniques. All these reports indicate that MTX is activating a voltage independent, nonselective cationic channel, which in some preparations requires the presence of extracellular Ca2+ for channel activation. The conductance estimated from a variety of tissues is in the order of 12-40 pS. Thus far, no specific blocker has been identified for this channel. The nature of the MTX receptor remains a mistery.
Insights
Maitotoxin (MTX), a marine toxin causing ciguatera seafood poisoning, activates a nonselective cation channel. This channel, independent of voltage, may require extracellular calcium for activation, with its receptor still unknown.
Area of Science:
- Marine biology
- Toxicology
- Cellular physiology
Background:
- Maitotoxin (MTX) is a potent marine toxin produced by Gambierdiscus toxicus, implicated in ciguatera seafood poisoning.
- MTX is known to induce significant changes in intracellular calcium (Ca2+) concentrations across various cell types.
- Recent evidence suggests MTX lacks ionophoretic activity, challenging previous understandings of its mechanism.
Purpose of the Study:
- To review and synthesize existing electrophysiological studies on Maitotoxin's cellular effects.
- To elucidate the mechanism by which MTX alters cellular ion concentrations.
- To characterize the properties of the channel activated by MTX.
Main Methods:
- Compilation and analysis of published electrophysiological studies.
- Molecular mechanics modeling to understand MTX structure-function relationships.
- Review of experimental data on MTX-induced cellular responses.
Main Results:
- MTX activates a voltage-independent, nonselective cationic channel.
- Channel activation may necessitate extracellular calcium in certain biological preparations.
- Estimated channel conductance ranges from 12 to 40 pS across different tissues.
- No specific blockers for the MTX-activated channel have been identified to date.
Conclusions:
- Maitotoxin likely functions by activating a specific cation channel rather than through direct ion transport.
- The precise nature of the MTX receptor remains unidentified, warranting further investigation.
- Understanding this channel is crucial for comprehending ciguatera pathogenesis and potential therapeutic targets.