The function of Ensembl gene identifier ENSG00000166257 (SCN3B, sodium voltage-gated channel beta subunit 3) is as follows. Regulatory subunit of multiple voltage-gated sodium (Nav) channels directly mediating the depolarization of excitable membranes. 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. The accessory beta subunits participate in localization and functional modulation of the Nav channels (PubMed:20558140, PubMed:21051419). Modulates the activity of SCN2A/Nav1.2, causing a hyperpolarizing shift in the voltage-dependence of inactivation of the channel and increasing the fraction of channels operating in the fast gating mode (By similarity). Modulates the activity of SCN5A/Nav1.5 (PubMed:20558140, PubMed:21051419, PubMed:24567321, PubMed:31950564). Could also regulate the atypical sodium channel SCN7A/Nav2.1 (PubMed:35301303). Modulates the activity of SCN10A/Nav1.8, regulating its oligomerization and accelerating the recovery from inactivation (PubMed:14975698). {ECO:0000250|UniProtKB:Q9JK00, ECO:0000269|PubMed:14975698, ECO:0000269|PubMed:20558140, ECO:0000269|PubMed:21051419, ECO:0000269|PubMed:24567321, ECO:0000269|PubMed:31950564, ECO:0000269|PubMed:35301303}.