The existence of resting K+ conductance has been known for some time. Only recently has the Nalcn (sodium leak channel non-selective protein) has been found responsible for the resting Na+ conductance1.
Nalcn is a member of the NaV and CaV channels family which have four homologous repeats of six transmembrane domains. One structural difference is that Nalcn is less positively charged in the voltage sensing segment1. The protein forms voltage-independent non-inactivating channel which is permeable to Na+, K+ and Ca2+ ions1,2.
Evidence suggests that Nalcn is a non-redundant and thus essential channel since knock-out mice display disrupted respiratory rhythm and die with 24 hours of birth. In addition, isolated neurons from these mice have decreased excitability1.
The channel is extensively expressed in the central nervous system1, heart, pituitary and adrenal glands and pancreatic islet cells2,3.
In pancreatic islets, Nalcn is activated by acetylcholine via its physical association with M3 muscarinic receptor, and potentiates insulin secretion induced by glucose uptake2-4.
