Proton-gated sodium channel; it is activated by a drop of the extracellular pH and then becomes rapidly desensitized. Generates a biphasic current with a fast inactivating and a slow sustained phase. Has high selectivity for sodium ions and can also transport lithium ions with high efficiency. Can also transport potassium ions, but with lower efficiency. It is nearly impermeable to the larger rubidium and cesium ions. Inhibited by the diuretic amiloride. Homotrimer or heterotrimer with other ASIC proteins (By similarity). Interacts with ASIC1/ACCN2B. Expressed in central nervous system. Expressed 30 hours post-fertilization (hpf) in the anterior and posterior lateral line ganglia where it persisted until at least 48 hpf. Also expressed between 30 and 72 hpf in the telencephalon. Expressed in the ventral thalamus, ventral midbrain, ventral cerebellum, and ventral hindbrain from 30 hpf. By 48 hpf, expressed also in the dorsal thalamus and hypothalamus. At 72 hpf, weak expression was apparent in the habenulae. Channel opening involves a conformation change that affects primarily the extracellular domain and the second transmembrane helix and its orientation in the membrane. In the open state, the second transmembrane helix is nearly perpendicular to the plane of the membrane; in the desensitized state it is strongly tilted. Besides, the second transmembrane domain is discontinuously helical in the open state. The GAS motif of the selectivity filter is in an extended conformation, giving rise to a distinct kink in the polypeptide chain. A domain swap between subunits gives rise to a full-length transmembrane helix (By similarity). Belongs to the amiloride-sensitive sodium channel (TC 1.A.6) family. ASIC1 subfamily.