Acid-sensing ion channel

Acid-sensing ion channels (ASICs) are neuronal voltage-insensitive sodium channels activated by extracellular protons. ASIC1 also shows low Ca²⁺ permeability. ASIC proteins are a subfamily of the ENaC/Deg superfamily of ion channels. These genes have splice variants that encode for several isoforms that are marked by a suffix. In mammals, acid-sensing ion channels (ASIC) are encoded by five genes that produce ASIC protein subunits: ASIC1, ASIC2, ASIC3, ASIC4, and ASIC5. Three of these protein subunits assemble to form the ASIC, which can combine into both homotrimeric and heterotrimeric channels typically found in both the central nervous system and peripheral nervous system. However, the most common ASICs are homotrimeric ASIC1a (an isoform of ASIC1) and heterotrimeric ASIC1a/2a (where ASIC2a is an isoform of ASIC2) and homotrimeric ASIC3. ASIC2b is non-functional on its own but modulates channel activity when participating in heteromultimers and ASIC4 has no known function. On a broad scale, ASICs are potential drug targets due to their involvement in pathological states such as retinal damage, seizures, and ischemic brain injury.