Regulatory subunit of multiple voltage-gated sodium channel complexes that play important roles in excitable membranes in brain, heart and skeletal muscle. Enhances the presence of the pore-forming alpha subunit at the cell surface and modulates channel gating characteristics and the rate of channel inactivation. Modulates the activity of multiple pore-forming alpha subunits, such as SCN1A, SCN2A, SCN3A, SCN4A, SCN5A and SCN10A. Cell adhesion molecule that plays a critical role in neuronal migration and pathfinding during brain development. Stimulates neurite outgrowth (PubMed:21994374). Has no regulatory function on the SCN2A sodium channel complex (PubMed:14622265). Component of a voltage-sensitive sodium channel complex that consists of a pore-forming alpha subunit and one or more regulatory beta subunits (PubMed:15525788, PubMed:21994374, PubMed:30190309). Interacts with SCN4A (PubMed:8125980). Interacts with NFASC. Interacts with SCN10A (By similarity). Interacts with SCN1A (PubMed:15525788, PubMed:21994374, PubMed:17928445). Interacts with SCN3A (PubMed:21994374). Interacts with SCN5A (PubMed:21994374). Interacts with SCN8A (PubMed:26900580). Detected at nodes of Ranvier on the sciatic nerve. Detected on Purkinje cells and their cell projections and on neuronal cell projections. The overall expression of isoform 1 and isoform 2 is very similar. Isoform 1 is abundantly expressed in skeletal muscle, heart and brain. Isoform 2 is highly expressed in brain and skeletal muscle and present at a very low level in heart, placenta, lung, liver, kidney and pancreas. In brain, isoform 2 is most abundant in the cerebellum, followed by the cerebral cortex and occipital lobe, while isoform 1 levels are higher in the cortex compared to the cerebellum. Isoform 2 is expressed in many regions of the brain, including cerebellar Purkinje cells, cortex pyramidal neurons and many of the neuronal fibers throughout the brain (at protein level). Also detected in dorsal root ganglion, in fibers of the spinal nerve and in cortical neurons and their processes (at protein level). The disease is caused by variants affecting the gene represented in this entry. The gene represented in this entry may be involved in disease pathogenesis. 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. Due to intron 3 retention. Belongs to the sodium channel auxiliary subunit SCN1B (TC 8.A.17) family.