Coupling of a P2Z-like purinoceptor to a fatty acid-activated K(+) channel in toad gastric smooth muscle cells.
1. Extracellular application of ATP generates two whole-cell currents in toad gastric smooth muscle cells: an immediate inward non-selective cation current (due to the activation of a P2X or P2Z-like receptor) and a slowly developing outward K(+) current. The inward non-selective cation current depends on the continuous presence of ATP while the outward K(+) current can last for minutes after ATP application ceases. 2. In cell-attached patches, application of ATP to the extra-patch membrane can activate K(+) channels in the patch indicating that a diffusible cellular messenger may be involved. The characteristics of these K(+) channels are similar to those of a previously described fatty acid-activated K(+) channel that is also a stretch-activated channel. 3. This whole-cell K(+) current can be induced by ATP in the absence of extracellular Ca(2+) (with EGTA present to chelate trace amounts). However, the current generated in the presence of extracellular Ca(2+) is considerably larger. 4. The pharmacological profiles for the activation of the non-selective cation current and the K(+) current are similar, suggesting that the same P2Z-like receptor could be mediating both responses. This type of plasma membrane receptor/channel-channel coupling by a process that does not appear to involve Ca(2+) flow through the receptor/channel or a subsequent membrane potential change may be representative of a new class of signalling mechanisms.
Zou
H
H
Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655, USA. imaging.ionchannels@umassmed.edu
Ugur
M
M
Drummond
R M
RM
Singer
J J
JJ
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D002024:Bufo marinus; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D004553:Electric Conductivity; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005227:Fatty Acids / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology; D005753:Gastric Mucosa / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D013270:Stomach / Q000166:cytology
D005227:Fatty Acids; D015221:Potassium Channels; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D019204:GTP-Binding Proteins; D002118:Calcium