G protein-activated inward rectifier potassium channel 4 (GIRK-4) is a protein that in humans is encoded by the KCNJ5 gene and is a type of G protein-gated ion channel.[5][6]
Potassium channels are present in most mammalian cells, where they participate in a wide range of physiologic responses. The protein encoded by this gene is an integral membrane protein and inward-rectifier type potassium channel. The encoded protein, which has a greater tendency to allow potassium to flow into a cell rather than out of a cell, is controlled by G-proteins. It may associate with other G-protein-activated potassium channel subunits to form a heterotetrameric pore-forming complex.[6]
In humans KCNJ5 is mainly expressed in adrenal gland and pituitary, although it is also detected at low levels in pancreas, spleen, lung, heart and brain.[7] Consistent with this expression pattern, mutations in KCNJ5/Kir3.4 can cause familial hyperaldosteronism type III and a type of long QT syndrome.[8]