Analysis of the Structure and Electrophysiological Actions of Halitoxins: 1,3 Alkyl-pyridinium Salts from Callyspongia ridleyi

Analysis of the Structure and Electrophysiological Actions of Halitoxins: 1,3 Alkyl-pyridinium... We have chemically characterized a preparation of halitoxins, (1,3 alkyl-pyridinium salts) isolated from the marine sponge Callyspongia ridleyi. At concentrations of 50 and 5 μg/ml the halitoxin preparation caused irreversible membrane potential depolarization, decreased input resistance and inhibited evoked action potentials when applied to cultured dorsal root ganglion neurones. Under whole cell voltage clamp the halitoxins produced an increase in cation conductance that was attenuated by replacing sodium with N-methyl-d-glucamine. Fura-2 fluorescence ratiometric calcium imaging was used to directly measure calcium flux into neurones after exposure to halitoxins. Calcium influx, evoked by the halitoxins, persisted when the neurones were bathed in medium containing the voltage-activated calcium channel antagonists cadmium and nickel. Experiments on undifferentiated F-11 cells showed little or no calcium influx in response to depolarizing concentrations of potassium and indicated that halitoxins evoked massive calcium influx in the absence of voltage-activated calcium channels. The halitoxins also produced transient increases in intracellular calcium when F-11 cells were bathed in calcium-free medium suggesting that the toxins could release calcium from intracellular stores. The pore-forming action of the halitoxins was identified when the toxins were applied to artificial lipid bilayers composed of phosphatidylcholine and cholesterol. Halitoxins evoked channel-like activity in the lipid bilayers, with estimated unitary conductances of between 145pS and 2280pS, possibly indicating that distinct channels could be produced by the different components in the preparation of halitoxins. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Analysis of the Structure and Electrophysiological Actions of Halitoxins: 1,3 Alkyl-pyridinium Salts from Callyspongia ridleyi

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2000 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s00232001078
Publisher site
See Article on Publisher Site

Abstract

We have chemically characterized a preparation of halitoxins, (1,3 alkyl-pyridinium salts) isolated from the marine sponge Callyspongia ridleyi. At concentrations of 50 and 5 μg/ml the halitoxin preparation caused irreversible membrane potential depolarization, decreased input resistance and inhibited evoked action potentials when applied to cultured dorsal root ganglion neurones. Under whole cell voltage clamp the halitoxins produced an increase in cation conductance that was attenuated by replacing sodium with N-methyl-d-glucamine. Fura-2 fluorescence ratiometric calcium imaging was used to directly measure calcium flux into neurones after exposure to halitoxins. Calcium influx, evoked by the halitoxins, persisted when the neurones were bathed in medium containing the voltage-activated calcium channel antagonists cadmium and nickel. Experiments on undifferentiated F-11 cells showed little or no calcium influx in response to depolarizing concentrations of potassium and indicated that halitoxins evoked massive calcium influx in the absence of voltage-activated calcium channels. The halitoxins also produced transient increases in intracellular calcium when F-11 cells were bathed in calcium-free medium suggesting that the toxins could release calcium from intracellular stores. The pore-forming action of the halitoxins was identified when the toxins were applied to artificial lipid bilayers composed of phosphatidylcholine and cholesterol. Halitoxins evoked channel-like activity in the lipid bilayers, with estimated unitary conductances of between 145pS and 2280pS, possibly indicating that distinct channels could be produced by the different components in the preparation of halitoxins.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jul 15, 2000

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