Inward Rectifier Potassium Channels

Inwardly rectifying potassium (Kir) channels allow K⁺ flow more easily into than out of the cell due to voltage-dependent block by intracellular Mg²⁺ and polyamines. Kir channel proteins are structurally distinct from other potassium channel families, possessing only two membrane-spanning helices. Seven subfamilies of the Kir family have been identified in mammals, exhibiting varying degrees of inward rectification and distinct gating mechanisms. The activity of Kir channels is regulated by diverse molecules, including ions, lipids and proteins. Kir channels are widely expressed in the brain, heart, kidney and pancreas, and play central roles in control of cellular excitability and K⁺ homeostasis. Mutations in the genes encoding Kir channels underlie multiple human diseases. This chapter provides an introduction to their molecular, structural, physiological and pharmacological properties.