This protein mediates the voltage-dependent sodium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a sodium-selective channel through which Na(+) ions may pass in accordance with their electrochemical gradient (   , ). It is a tetrodotoxin-resistant Na(+) channel isoform . This channel is responsible for the initial upstroke of the action potential. Channel inactivation is regulated by intracellular calcium levels .
Subcellular locations: Cell membrane, Cytoplasm, Perinuclear region, Cell membrane, Sarcolemma, T-tubule, Cell junction
RANGRF promotes trafficking to the cell membrane. Colocalizes with PKP2 at intercalated disks in the heart (By similarity).
Found in jejunal circular smooth muscle cells (at protein level). Expressed in human atrial and ventricular cardiac muscle but not in adult skeletal muscle, brain, myometrium, liver, or spleen. Isoform 4 is expressed in brain.