Regulatory subunit of Kv4/D (Shal)-type voltage-gated rapidly inactivating A-type potassium channels. Modulates KCND2 channel density, inactivation kinetics and rate of recovery from inactivation in a calcium-dependent and isoform-specific manner. Modulates KCND3/Kv4.3 currents. Isoform 4 does not increase KCND2 expression at the cell membrane. Isoform 4 retains KCND3 in the endoplasmic reticulum and negatively regulates its expression at the cell membrane.
Subcellular locations: Cell membrane, Cytoplasm, Peroxisome