Mediates voltage-dependent potassium ion permeability of excitable membranes. Assuming opened or closed conformations in response to the voltage difference across the membrane, the protein forms a potassium-selective channel through which potassium ions may pass in accordance with their electrochemical gradient. The channel activity is up-regulated by cAMP. Homotetramer. Interacts with KCN4B/POMP. Interaction with KCN4B/POMP is necessary for the modulation of channel activity by cAMP. Detected in kidney, in proximal tubules, glomerular endothelium, in vascular endothelium and in smooth muscle cells. The N-terminus may be important in determining the rate of inactivation of the channel while the tail may play a role in modulation of channel activity and/or targeting of the channel to specific subcellular compartments. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. Belongs to the potassium channel family. A (Shaker) (TC 1.A.1.2) subfamily. Kv1.8/KCNA10 sub-subfamily.