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 (PubMed:1325650, PubMed:17021166, PubMed:28256214, PubMed:29844171). 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. Heterooligomer with SCN1B or SCN3B; non-covalently linked. Interacts with NEDD4L. Interacts with CALM. Interacts with the conotoxin GVIIJ (PubMed:24497506). Interacts with the spider beta/delta-theraphotoxin-Pre1a (PubMed:28428547). Interacts with the conotoxin KIIIA (PubMed:30765605). Interacts with the spider protoxin-II (PubMed:26894959). 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. Sumoylated SCN2A is located at the cell membrane. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Defects in SCN2A are associated with genetic epilepsy with febrile seizures plus (GEFS+), a familial autosomal dominant epilepsy syndrome, a clinical subset of febrile seizures, characterized by frequent episodes after 6 years of age and various types of subsequent epilepsy. Defects in SCN2A are associated with autism spectrum disorders (ASD). It seems that mutations resulting in sodium channel gain of function and increased neuron excitability lead to infantile seizures, whereas variants resulting in sodium channel loss of function and decrease neuron excitability are associated with ASD. The disease is caused by variants affecting the gene represented in this entry. Belongs to the sodium channel (TC 1.A.1.10) family. Nav1.2/SCN2A subfamily. Contaminating sequence. Sequence of unknown origin in the C-terminal part.