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Calcium is permeable through a maitotoxin-activated nonselective cation channel in mouse L cells
M Estacion1, H B Nguyen, J J Gargus
1Department of Physiology and Biophysics, University of California, Irvine 92717, USA.
Abstract:
The shellfish poison maitotoxin causes the irreversible opening of nonselective cation channels in mouse L cell fibroblasts, consistent with the action of this toxin in other cell types and the previously demonstrated existence of 28-pS voltage-insensitive nonselected cation channels that are activated by platelet-derived growth factor in these cells. Toxin-induced opening of these nonselective cation channels led to increases of intracellular calcium and secondary activation of calcium-activated potassium channel. These effects were completely dependent on influx of extracellular calcium, supporting the conclusion that the maitotoxin-activated nonselective cation channels are permeable to calcium as well as to sodium and potassium. The implication of this finding is that calcium signaling through this channel underlies its links into the growth factor response.
Insights
Maitotoxin, a shellfish poison, irreversibly opens nonselective cation channels in mouse cells. This toxin-induced channel activity increases intracellular calcium, impacting cell signaling and growth factor responses.
Area of Science:
- Toxicology
- Cell Biology
- Ion Channel Physiology
Background:
- Maitotoxin is a potent marine toxin known to affect ion channels.
- Mouse L cell fibroblasts possess 28-pS, voltage-insensitive cation channels activated by platelet-derived growth factor.
- The precise mechanism of maitotoxin's action on these channels was not fully elucidated.
Purpose of the Study:
- To investigate the effect of maitotoxin on nonselective cation channels in mouse L cell fibroblasts.
- To determine the ion permeability of maitotoxin-activated channels.
- To elucidate the role of these channels in calcium signaling and cellular responses.
Main Methods:
- Electrophysiological recordings in mouse L cell fibroblasts.
- Application of maitotoxin to assess channel activity.
- Measurement of intracellular calcium concentrations.
- Analysis of ion flux dependency on extracellular calcium.
Main Results:
- Maitotoxin induced irreversible opening of nonselective cation channels in mouse L cells.
- These channels are permeable to calcium (Ca2+), sodium (Na+), and potassium (K+).
- Toxin-induced channel activity led to increased intracellular calcium and secondary activation of calcium-activated potassium channels.
- The observed effects were dependent on extracellular calcium influx.
Conclusions:
- Maitotoxin activates nonselective cation channels in mouse fibroblasts, leading to calcium influx.
- These channels are crucial for maitotoxin-induced calcium signaling.
- Calcium signaling via these channels is implicated in the cellular response to growth factors.