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 (By similarity). Homomultimeric and heteromultimeric association with KCNJ2, resulting in an enhanced G-protein-induced current. Association, via its PDZ-recognition domain, with LIN7A, LIN7B, LIN7C, DLG1, CASK and APBA1 plays a key role in its localization and trafficking (By similarity). May also associate with GIRK1 or GIRK4 to form a G-protein-activated heteromultimer pore-forming unit. The resulting inward current is much larger. Interacts with TAX1BP3. TAX1BP3 competes with LIN7 family members for KCNJ4 binding (By similarity). TAX1BP3 binding promotes dissociation of KCNJ4 from LIN7 famaly members and KCNJ4 internalization. Belongs to the inward rectifier-type potassium channel (TC 1.A.2.1) family. KCNJ4 subfamily.