An amiloride-sensitive H+-gated Na+ channel in Caenorhabditis elegans body wall muscle cells.
About 30 genes are predicted to encode degenerin/epithelial sodium channels (DEG/ENaCs) in Caenorhabditis elegans but the gating mode of these channels has not been determined. Using the whole-cell configuration of the patch-clamp technique in acutely dissected C. elegans, we investigated the effects of H+ as a potential activating factor of DEG/ENaCs on electrical properties of body wall muscle cells. Under current-clamp conditions, decreasing external pH from 7.2 to 6.1 led to a reversible depolarization of muscle cells associated with a decrease in input resistance which was partially inhibited by amiloride. Under voltage-clamp conditions, extracellular acidification activated an inward desensitizing current at -60 mV. In the absence of external Ca2+, H+ -gated channels were found to be slightly more permeable to Na+ than to K+ and were blocked by amiloride with a K0.5 of 31 microm at -60 mV. An inward current could be also activated by protons in a GABA receptor null mutant in the presence of D-tubocurare and in an unc-105 null mutant. These results demonstrate that ion channels sharing common properties with mammalian acid-sensing ion channels (ASICs) are functional in C. elegans muscle which should prove useful for understanding proton sensing in animals.
Jospin
Maëlle
M
Physiologie Intégrative, Cellulaire et Moléculaire, UMR CNRS 5123, Université C. Bernard Lyon I, 43 bd du 11 Novembre 1918, 69622 Villeurbanne cedex, France.
Allard
Bruno
B
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000819:agonists / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology*; D011522:Protons; D062687:Sodium Channel Agonists; D015222:Sodium Channels / Q000502:physiology*
D029742:Caenorhabditis elegans Proteins; C094927:Deg-1 protein, C elegans; D008565:Membrane Proteins; D011522:Protons; D062687:Sodium Channel Agonists; D015222:Sodium Channels; D000584:Amiloride