The function of SCN4B (sodium voltage-gated channel beta subunit 4, ENSG00000177098) 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:24297919). Modulates the activity of SCN1A/Nav1.1 (PubMed:33712547). Modulates the activity of SCN2A/Nav1.2 (PubMed:24297919). {ECO:0000269|PubMed:24297919, ECO:0000269|PubMed:33712547}.