Pore-forming (alpha) subunit of voltage-gated rapidly inactivating A-type potassium channels. May contribute to I(To) current in heart and I(Sa) current in neurons. Channel properties are modulated by interactions with other alpha subunits and with regulatory subunits. Homotetramer or heterotetramer with KCND1 and/or KCND2. Associates with the regulatory subunits KCNIP1, KCNIP2, KCNIP3 and KCNIP4 (By similarity). Interacts with KCNE1, KCNE2, SCN1B and KCNAB1 and DLG1. Interaction with palmitoylated KCNIP2 and KCNIP3 enhances cell surface expression. Highly expressed in heart and brain, in particular in cortex, cerebellum, amygdala and caudate nucleus. Detected at lower levels in liver, skeletal muscle, kidney and pancreas. Isoform 1 predominates in most tissues. Isoform 1 and isoform 2 are detected at similar levels in brain, skeletal muscle and pancreas. The segment S4 is probably the voltage-sensor and is characterized by a series of positively charged amino acids at every third position. Regulated through phosphorylation at Ser-569 by CaMK2D. The disease is caused by variants affecting the gene represented in this entry. The gene represented in this entry may be involved in disease pathogenesis. Belongs to the potassium channel family. D (Shal) (TC 1.A.1.2) subfamily. Kv4.3/KCND3 sub-subfamily. Leiden Open Variation Database (LOVD)