Analysis of the structure and electrophysiological actions of halitoxins: 1,3 alkyl-pyridinium salts from Callyspongia ridleyi

R H Scott, A D Whyment, A Foster, K H Gordon, B F Milne, M Jaspars

Research output: Contribution to journalArticle

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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 mu g/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 whale 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 port-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.

Original languageEnglish
Pages (from-to)119-131
Number of pages13
JournalJournal of Membrane Biology
Volume176
Publication statusPublished - 2000

Keywords

  • calcium permeant ion channel
  • pore former
  • halitoxin
  • sensory neurone
  • lipid bilayer
  • SPONGE HALICLONA-VIRIDIS
  • AUREUS ALPHA-TOXIN
  • MARINE SPONGES
  • PORE FORMATION
  • CHANNELS
  • CELLS
  • PERMEABILITY
  • ALKALOIDS
  • PORIFERA
  • BILAYERS

Cite this

Analysis of the structure and electrophysiological actions of halitoxins: 1,3 alkyl-pyridinium salts from Callyspongia ridleyi. / Scott, R H ; Whyment, A D ; Foster, A ; Gordon, K H ; Milne, B F ; Jaspars, M .

In: Journal of Membrane Biology, Vol. 176, 2000, p. 119-131.

Research output: Contribution to journalArticle

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T1 - Analysis of the structure and electrophysiological actions of halitoxins: 1,3 alkyl-pyridinium salts from Callyspongia ridleyi

AU - Scott, R H

AU - Whyment, A D

AU - Foster, A

AU - Gordon, K H

AU - Milne, B F

AU - Jaspars, M

PY - 2000

Y1 - 2000

N2 - 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 mu g/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 whale 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 port-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.

AB - 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 mu g/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 whale 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 port-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.

KW - calcium permeant ion channel

KW - pore former

KW - halitoxin

KW - sensory neurone

KW - lipid bilayer

KW - SPONGE HALICLONA-VIRIDIS

KW - AUREUS ALPHA-TOXIN

KW - MARINE SPONGES

KW - PORE FORMATION

KW - CHANNELS

KW - CELLS

KW - PERMEABILITY

KW - ALKALOIDS

KW - PORIFERA

KW - BILAYERS

M3 - Article

VL - 176

SP - 119

EP - 131

JO - Journal of Membrane Biology

JF - Journal of Membrane Biology

SN - 0022-2631

ER -