Nomenclature of Voltage-Gated Sodium Channels

been given different names, so that there are multiple Sodium Channels synonyms for many of sodium channel isoforms. To eliminate confusion resulting from the multiplicity of names, we propose a standardized nomenclature for Voltage-gated sodium channels are critical elements of voltage-gated sodium channels (Table 1). This nomen-action potential initiation and propagation in excitable clature is based on the one for voltage-gated potassium cells because they are responsible for the initial depolar-channels (Chandy, 1991) that is now in common use. It ization of the membrane. These channels consist of a utilizes a numerical system to define subfamilies and highly processed ␣ subunit that is ‫062ف‬ kDa, associated subtypes based on similarities among the amino acid with auxiliary ␤ subunits (reviewed by Catterall, 2000). sequences of the channels. A comparable nomenclature Sodium channels in the adult CNS contain ␤1 (or ␤3) has been proposed for voltage-gated calcium channels and ␤2 subunits, while channels in adult skeletal muscle (Ertel et al., 2000). The name consists of the chemical have only the ␤1 subunit. The pore-forming ␣ subunit symbol of the principal permeating ion (Na) with the is sufficient for functional expression, but the kinetics principal physiological regulator (voltage) indicated as and voltage dependence of channel gating are modified a subscript (Na V). The number following the subscript by the ␤ subunits. indicates the gene subfamily (currently only Na V 1), and A variety of different sodium channels have been iden-the number following the decimal point identifies the tified by electrophysiological recording, biochemical pu-specific channel isoform (e.g., Na V 1.1). That number has rification, and molecular cloning (reviewed by Goldin, been assigned according to the approximate order in 2001). The sodium channels are the founding members which each gene was identified. Splice variants of each of the superfamily of ion channels that includes voltage-family member are identified by lowercase letters follow-gated potassium and calcium channels. Unlike the dif-ing the numbers (e.g., Na V 1.1a). ferent classes of potassium and calcium channels, the The nine mammalian sodium channel isoforms that functional properties of the known sodium channels are have been identified and functionally expressed are all relatively similar. Despite their similarity of function, the greater than 50% identical in amino acid sequence in sodium channels have been named in many different the transmembrane and extracellular domains, where ways, with no consistent nomenclature for the various the amino acid sequence is similar enough for clear isoforms. …