A voltage-gated chloride channel in ascidian embryos modulated by both the cell cycle clock and cell volume.
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.
Villaz
M
M
Department of Zoology, University of Washington, Seattle 98195, USA.
Cinniger
J C
JC
Moody
W J
WJ
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016477:Artifacts; D002453:Cell Cycle / Q000502:physiology; D048429:Cell Size / Q000502:physiology; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000201:enzymology / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015640:Ion Channel Gating / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D009995:Osmosis / Q000502:physiology; D011494:Protein Kinases / Q000378:metabolism; D014561:Urochordata / Q000196:embryology*
D018118:Chloride Channels; D002712:Chlorides; D004791:Enzyme Inhibitors; C001020:N(6),N(6)-dimethyladenine; D000242:Cyclic AMP; D011494:Protein Kinases; D000225:Adenine