Kir4.2 is a member of the family of inward rectifying K+ channels. The family includes 15 members that are structurally and functionally different from the voltage-dependent K+ channels.
The family’s topology consists of two transmembrane domains that flank a single and highly conserved pore region with intracellular N- and C-termini. As is the case for the voltage-dependent K+ channels the functional unit for the Kir channels is composed of four subunit that can assembly as either homo or heteromers.
Kir channels are characterized by a K+ efflux that is limited by depolarizing membrane potentials thus making them essential for controlling resting membrane potential and K+ homeostasis.
Kir4.2 is a member of the Kir4 subfamily that includes one other member: Kir4.1. Kir4.2 can co-assemble with Kir4.1 but also with other Kir channels such as Kir1.1 and Kir5.1.2
The Kir4 subfamily has been classified as weak rectifiers with intermediate conductance.
Kir4.2 is expressed in liver, kidney, pancreas lung and testis. Its physiological function is not well understood but it has been suggested that it could be involved in the regulation of K+ efflux in epithelial cells such as hepatocytes or lung cells.1
