Voltage-gated ion channel responsible for the resting Na(+) permeability that controls neuronal excitability. NALCN channel functions as a multi-protein complex, which consists at least of NALCN, NALF1, UNC79 and UNC80. NALCN is the voltage-sensing, pore-forming subunit of the NALCN channel complex. NALCN channel complex is constitutively active and conducts monovalent cations but is blocked by physiological concentrations of extracellular divalent cations (By similarity). In addition to its role in regulating neuronal excitability, is required for normal respiratory rhythm, systemic osmoregulation by controlling the serum sodium concentration and in the regulation of the intestinal pace-making activity in the interstitial cells of Cajal (PubMed:21177381, PubMed:22508057). Plays a critical role in both maintenance of spontaneous firing of substantia nigra pars reticulata (SNr) neurons and physiological modulation of SNr neuron excitability (PubMed:27177420). NALCN channel is also activated by neuropeptides such as neurotensin and substance P (SP) through a SRC family kinases-dependent pathway (PubMed:19092807). In addition, NALCN activity is enhanced/modulated by several GPCRs, such as CHRM3 (PubMed:19092807, PubMed:19575010, PubMed:21040849). Inhibited by low micromolar concentrations of Gd(3+) and high micromolar concentrations of verapamil. Insensitive to tetrodotoxin (TTX) and potentiated by low external Ca(2+) concentration. Found in a complex with NALCN, UNC79, UNC80 and NACL1; these auxiliary subunits are indispensable for the function of the NALCN channel (By similarity). Interacts with UNC80; required for the NALCN activation/inhibition by GPCRs in neurons (PubMed:19092807, PubMed:21040849). Found in a complex with NALCN, UNC79 and UNC80; UNC80 bridges NALCN to UNC79 (PubMed:21040849). Interacts with CHRM3 (PubMed:19575010). Widely expressed in the brain and spinal cord neurons (PubMed:17448995). Expressed also in pancreatic islet cells (PubMed:19575010). Contains 24 transmembrane helices (TM) that form four homologous functional repeats connected by intracellular linkers. Each of the four internal repeats contains five hydrophobic transmembrane segments (S1, S2, S3, S5, S6) and one positively charged transmembrane segment (S4). S4 segments represent the voltage-sensor. S4 transmembrane segments lack some of the charged residues (K and R) found at every third position in the S4s of the NaV, CaV, and KV channels. Pore-forming loops (P loops) between S5 and S6 of each domain form an EEKE sodium- ion selectivity filter a mixture between the EEEE found in the CaVs and the DEKA of NaVs. Voltage-sensing domains (VSDs), formed by S1 to S4 of each domain, detect changes in membrane potential and induce the opening or closing of the ion-conducting pore domain, formed by S5 and S6. Phosphorylated on tyrosine residues. Deficient mice exhibit abnormal breathing at birth and die within 24 hours. Belongs to the NALCN family. NALCN was also originally reported to be a voltage-independent, cation-nonselective channel which is permeable to sodium, potassium and calcium ions (PubMed:17448995). However, NALCN is recently reported to be selective only for monovalent cations and to be blocked by extracellular divalent cations (By similarity). Futhemore, coexpression of NALCN, UNC79, UNC80, and NALF1 results in voltage-dependent NALCN currents (By similarity).