A voltage-gated chloride channel in ascidian embryos modulated by both the cell cycle clock and cell volume

• Published in: The Journal of physiology 1995-11, Vol.488 (Pt 3), p.689-699
• Main Authors: Villaz, M, Cinniger, J C, Moody, W J
• Format: Article
• Language: English
• Subjects: Adenine - analogs & derivatives; Adenine - pharmacology; Animals; Cell Cycle - physiology; Cell Size - physiology; Chloride Channels - physiology; Chlorides - metabolism; Cyclic AMP - pharmacology; Embryo, Nonmammalian - cytology; Embryo, Nonmammalian - enzymology; Embryo, Nonmammalian - ultrastructure; Enzyme Inhibitors - pharmacology; Ion Channel Gating - physiology; Membrane Potentials - physiology; Osmosis - physiology; Protein Kinases - metabolism; Urochordata - embryology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.1995.sp021000

1. Eggs of the ascidian Boltenia villosa have an inwardly rectifying Cl- current whose amplitude varies by more than 10-fold during each cell cycle, the largest amplitude being at exit from M-phase. We examined whether this current was also sensitive to changes in cell volume. 2. Cell swelling, produced by direct inflation through a whole-cell recording pipette, greatly increased the amplitude of the Cl- current at all stages of the cell cycle in activated eggs. Swelling was much less effective in unfertilized eggs. 3. The increase in Cl- current amplitude continued for 10-20 min after an increase in diameter that was complete in 10 s, suggesting the involvement of a second messenger system in the response. 4. Treatment of unfertilized eggs with 6-dimethylaminopurine (DMAP), an inhibitor of cell cycle-dependent protein kinases, increased the amplitude of the Cl- current and its sensitivity to swelling to levels characteristic of fertilized eggs. 5. Osmotically produced swelling also increased Cl- current amplitude in unfertilized eggs. 6. We propose that dephosphorylation renders the Cl- channel functional, and that swelling or activation of the egg increases the sensitivity of the channel to dephosphorylation, perhaps by disrupting its links to the cytoskeleton.