ASIC channels belong to the ENaC/Degenerin superfamily and are proton-gated ion channels which are not voltage-dependent. Six different genes encode the different ASIC subunits and splice variants: ASIC1a, ASIC1b, ASIC2a, ASIC2b, ASIC3 and ASIC4. The topology of ASIC channels is predicted on the basis of that of ENaCs. However, different computational programs have depicted different structures for the ASICs.