View article

Potassium channels are tetrameric, membrane-spanning proteins that selectively conduct K⁺ at near diffusion-limited rates. Their remarkable ionic selectivity results from a highly-conserved K⁺ recognition sequence in the pore. The classical function of K⁺ channels is regulation of membrane potential (E_M) and thence vascular tone. In pulmonary artery smooth muscle cells (PASMC), tonic K⁺ egress, driven by a 145/5 mM intracellular/extracellular concentration gradient, contributes to a E_M of about −60 mV. It has been recently discovered that K⁺ channels also participate in vascular remodeling by regulating cell proliferation and apoptosis. PASMC express voltage-gated (K_v), inward rectifier (K_ir), calcium-sensitive (K_Ca), and two-pore (K_2P) channels. Certain K⁺ channels are subject to rapid redox regulation by reactive oxygen species (ROS) derived from the PASMC's oxygen-sensor (mitochondria and/or NADPH …