Probably participates in establishing action potential waveform and excitability of neuronal and muscle tissues. Inward rectifier potassium channels are characterized by a greater tendency to allow potassium to flow into the cell rather than out of it. Their voltage dependence is regulated by the concentration of extracellular potassium; as external potassium is raised, the voltage range of the channel opening shifts to more positive voltages. The inward rectification is mainly due to the blockage of outward current by internal magnesium. Can be blocked by extracellular barium or cesium.
PKA consensus site S425 required for PKA-mediated effects on Kir2.1 channels. PKA activation reduced outward IK1 for heteromeric Kir2.1 WT+V227F channels after 2 hours of PKA activation.
KCNJ2 encodes Kir2.1, a pore-forming subunit of the cardiac inward rectifier current, I(K1). This PKA-simulated catecholaminergic stimulation caused marked reduction of outward I(K1) compared with Kir2.1-WT. PKA-induced reduction in I(K1) was eliminated by mutating the phosphorylation site at serine 425 (S425N).