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. Implicated in the regulation of hippocampal replay occurring within sharp wave ripples (SPW-R) important for memory (By similarity). Heterooligomer of a large alpha subunit and a smaller beta subunit. Heterooligomer with SCN2B or SCN4B; disulfide-linked (PubMed:26894959). Heterooligomer with SCN1B or SCN3B; non-covalently linked. Interacts with NEDD4L. Interacts with CALM. Interacts with the conotoxin GVIIJ (PubMed:24497506). Interacts with the scorpion toxin BMK M1 (PubMed:20678086). Expressed in brain (at protein level) (PubMed:10827969). Expressed in cerebellar granule neurons (at protein level) (PubMed:28029095). The sequence contains 4 internal repeats, each with 5 hydrophobic segments (S1, S2, S3, S5, S6) and one positively charged segment (S4). Segments S4 are probably the voltage-sensors and are characterized by a series of positively charged amino acids at every third position. May be ubiquitinated by NEDD4L; which would promote its endocytosis. Phosphorylation at Ser-1506 by PKC in a highly conserved cytoplasmic loop slows inactivation of the sodium channel and reduces peak sodium currents. Sumoylated at Lys-38. Sumoylation is induced by hypoxia, increases voltage-gated sodium current and mediates the early response to acute hypoxia in neurons (PubMed:28029095). Sumoylated SCN2A is located at the cell membrane (PubMed:28029095). Belongs to the sodium channel (TC 1.A.1.10) family. Nav1.2/SCN2A subfamily.