Effects of Extracellular Calcium on fASIC1 Currents

• Published in: Annals of the New York Academy of Sciences Vol. 1048; no. 1; pp. 331 - 336
• Main Authors: TODOROVIĆ, NATAŠA, ĆORIĆ, TATJANA, ZHANG, PING, CANESSA, CECILIA
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2005
• Subjects: Acid Sensing Ion Channels; Activation; Affinity; Animals; ASIC; Calcium; Calcium - pharmacology; channel block; Channels; DEG/ENaC; Desensitization; Dose-Response Relationship, Drug; Extracellular Space - metabolism; Fish; Fishes; Gating and risering; Hydrogen-Ion Concentration; Ion Channel Gating - drug effects; Ion Channel Gating - physiology; Membrane Potentials - drug effects; Membrane Potentials - physiology; Membrane Proteins - drug effects; Membrane Proteins - metabolism; Membrane Proteins - physiology; Nerve Tissue Proteins - drug effects; Nerve Tissue Proteins - metabolism; Nerve Tissue Proteins - physiology; Opsanus tau; Preconditioning; Protons; Rats; Sodium Channels - drug effects; Sodium Channels - metabolism; Sodium Channels - physiology
• ISSN: 0077-8923; 1749-6632
• DOI: 10.1196/annals.1342.030

: Fish ASIC1 (fASIC1) cloned from Opsanus tau, unlike the rat ASICs, requires Ca2+ in the extracellular preconditioning solution (pH 7.4) to be activated. Here we show that fASIC1 is interacting with Ca2+ in the same way as mammalian ASICs: extracellular Ca2+ is increasing the proportion of channels available for activation by stabilizing the closed state of the channel; in the activation process Ca2+ is released; H+ compete for the binding site of Ca2+ making the gating mechanism both Ca2+ and H+ dependent; H+ stabilizes the desensitized state; Ca2+ blocks the fASIC1 channel; and the affinity of the block is also modulated by H+. The “Ca2+ activation requirement” of fASIC1 reflects its greater affinity for steady‐state desensitization by H+ compared to mammalian ASIC1.