Auxiliary subunit of the NALCN sodium channel complex, a voltage-gated ion channel responsible for the resting Na(+) permeability that controls neuronal excitability (By similarity). Activated by neuropeptides substance P, neurotensin, and extracellular Ca(2+) that regulates neuronal excitability by controlling the sizes of NALCN-dependent sodium-leak current. UNC80 is essential for NALCN sensitivity to extracellular Ca(2+) (By similarity). NALCN complex consists of NALCN and auxiliary subunits, UNC79, UNC80 and NACL1. These auxiliary subunits are essential for the NALCN complex function (By similarity). Interacts (via N-terminus half) with NALCN; this interaction facilitates NALCN surface localization (By similarity). Interacts with UNC79 (By similarity). UNC80 bridges NALCN to UNC79 (By similarity). Moderately expressed in fetal brain, spinal cord, skeletal muscle, thymus, spleen, fetal liver, small intestine, colon, kidney and uterus. Highly expressed in adrenal gland, prostate and testis, as well as in brain and cerebellum. Phosphorylated on tyrosine residues. The disease is caused by variants affecting the gene represented in this entry. Belongs to the unc-80 family.