Regulatory subunit of multiple voltage-gated sodium (Nav) channels directly mediating the depolarization of excitable membranes (PubMed:19808477, PubMed:23559163, PubMed:26894959, PubMed:30765605, PubMed:30765606, PubMed:35277491, PubMed:36823201). Navs, also called VGSCs (voltage-gated sodium channels) or VDSCs (voltage-dependent sodium channels), operate by switching between closed and open conformations depending on the voltage difference across the membrane. In the open conformation they allow Na(+) ions to selectively pass through the pore, along their electrochemical gradient. The influx of Na+ ions provokes membrane depolarization, initiating the propagation of electrical signals throughout cells and tissues (PubMed:19808477, PubMed:23559163, PubMed:26894959). The accessory beta subunits participate in localization and functional modulation of the Nav channels (PubMed:19808477, PubMed:23559163). Modulates the activity of SCN1A/Nav1.1, SCN2A/Nav1.2, SCN2A/Nav1.3, SCN5A/Nav1.5, SCN8A/Nav1.6, SCN9A/Nav1.7 and SCN10A/Nav1.8 (PubMed:19808477, PubMed:23559163, PubMed:26894959, PubMed:30765605, PubMed:30765606, PubMed:35277491, PubMed:36823201). {ECO:0000269|PubMed:19808477, ECO:0000269|PubMed:23559163, ECO:0000269|PubMed:26894959, ECO:0000269|PubMed:30765605, ECO:0000269|PubMed:30765606, ECO:0000269|PubMed:35277491, ECO:0000269|PubMed:36823201}. This is the function of ENSG00000149575 (SCN2B, sodium voltage-gated channel beta subunit 2).