Dependence of the acid-sensitive ion channel, ASIC1a, on extracellular Ca(2+) ions.
The early H(+)-induced current in the embryonic spinal cord neurone depends on extracellular Ca(2+) for its function. We have studied the Ca(2+)-dependence of homo- and heteromultimeric acid-sensing ion channels (ASICs) expressed in Cos cells. It was found that single-channel conductance of both the ASIC2a and the ASIC1a channel is reduced at membrane potentials more negative than -40 mV by elevated extracellular Ca(2+). Due to this effect on unitary currents, the macroscopic ASIC2a peak current at -60 mV decreases gradually with rising extracellular Ca(2+) concentration. In addition, the macroscopic ASIC1a current is very small at low extracellular Ca(2+) and increases with rising Ca(2+) up to 5 mM before decreasing again at still higher concentrations of extracellular Ca(2+).
de Weille
J
J
Institut de Pharmacologie Cellulaire et Moléculaire, CNRS UPR411, 06540, Valbonne, France. deweille@bram.org
Bassilana
F
F
D062565:Acid Sensing Ion Channels; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D005110:Extracellular Space / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008564:Membrane Potentials / Q000502:physiology; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D009994:Osmolar Concentration; D020033:Protein Isoforms / Q000378:metabolism / Q000502:physiology; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
C568266:ASIC1 protein, human; C112231:ASIC3 protein, human; D062565:Acid Sensing Ion Channels; D007477:Ions; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D000584:Amiloride; D002118:Calcium