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A voltage, calcium, and ATP sensitive non selective cation channel in human colonic tumor cells
G Champigny1, B Verrier, M Lazdunski
1Institut de Pharmacologie Moléculaire et Cellulaire du CNRS, Valbonne, France.
Abstract:
A non selective cation channel has been identified in the human colonic cell lines T84 and HT29D4 using the patch clamp technique. The channel is equally permeable to Na+ and K+, has a linear current-voltage relationship and a conductance of about 20 pS in symmetrical NaCl conditions. The channel is not permeable to chloride or to large organic cations such as N-methyl-D-glucamine. The open probability of the channel is voltage dependent. Cytosolic Ca2+ concentrations higher than 0.1 mM are required to activate the channel. The channel is blocked by cytosolic ATP (1 mM). 3',5-dichlorodiphenylamine-2-carboxylic acid and 5-nitro-2-(3-phenylpropylamino)-benzoic acid inhibit the channel when present on the extracellular side. The block is not voltage dependent. 3',5-dichlorodiphenylamine-2-carboxylic acid is the most potent blocker and completely inhibits channel activity at a concentration of 50 microM. The channel is insensitive to amiloride and derivatives.
Insights
Researchers identified a non-selective cation channel in human colon cells. This channel, permeable to sodium and potassium, is activated by calcium and inhibited by ATP and specific compounds.
Area of Science:
- Ion channel physiology
- Cellular biology
- Gastrointestinal research
Background:
- Human colonic cell lines T84 and HT29D4 are crucial models for studying intestinal transport.
- Understanding ion channel function is vital for elucidating epithelial transport mechanisms.
Purpose of the Study:
- To characterize a newly identified non-selective cation channel in human colonic epithelial cells.
- To investigate the biophysical properties, activation, and inhibition of this channel.
Main Methods:
- Utilized the patch clamp technique to record ion channel activity.
- Assessed ion permeability, current-voltage relationships, and channel conductance.
- Investigated the effects of various ions, blockers, and intracellular conditions on channel function.
Main Results:
- Identified a non-selective cation channel equally permeable to Na+ and K+ with ~20 pS conductance.
- The channel's open probability is voltage-dependent, activated by cytosolic Ca2+ (>0.1 mM), and inhibited by cytosolic ATP.
- Extracellular application of 3',5-dichlorodiphenylamine-2-carboxylic acid (50 microM) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid inhibited channel activity; the former was a potent blocker.
Conclusions:
- A novel non-selective cation channel exists in human colonic cells T84 and HT29D4.
- This channel exhibits unique properties regarding ion selectivity, voltage dependence, and specific inhibitors.
- The findings provide insights into colonic ion transport and potential therapeutic targets.