An acid‐sensing ion channel from shark (Squalus acanthias) mediates transient and sustained responses to protons

摘要: Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. They implicated in synaptic transmission, detection of painful acidosis, and possibly sour taste. The typical ASIC current is a transient, completely desensitizing that can be blocked by the diuretic amiloride. ASICs present chordates but absent other animals. have been cloned from urochordates, jawless vertebrates, cartilaginous shark bony fish, chicken different mammals. Strikingly, all so far characterized vertebrates not gated protons, suggesting proton gating evolved relatively late fish primitive had unknown mechanism. Recently, amino acids crucial for rat ASIC1a identified. These residues conserved ASIC1b (sASIC1b), prompting us to re-evaluate sensitivity sASIC1b. Here we show that, contrary previous findings, sASIC1b indeed protons with half-maximal activation at pH 6.0. desensitizes quickly incompletely, efficiently encoding transient as well sustained signals. Our results conservation predict an increase our understanding evolution ASICs.