Potassium channel protein Kir3.x subunit (Kir3.x (with x denoting a specific subunit, e.g., Kir3.1, Kir3.2, Kir3.3, Kir3.4))

Potassium channel protein Kir3.x subunit refers to a family of ion channel proteins encoded by several genes (KCNJ3, KCNJ5, KCNJ6, KCNJ9), which function as inwardly rectifying potassium channels gated by G proteins. Each Kir3.x channel is a tetramer of Kir3 subunits, which may form homo- or heteromeric assemblies and are chiefly activated by direct binding of G protein βγ subunits released from GPCRs. These channels play critical roles in regulating neuronal and cardiac excitability, generating inhibitory postsynaptic potentials, modulating heart rate, and influencing hormone secretion. Dysfunction or genetic variation within the Kir3.x family is linked with epilepsy, cardiac arrhythmia, addiction, and other neuropsychiatric and cardiovascular conditions. These properties make Kir3.x channels attractive, but complex, therapeutic targets. The principal safety concerns involve risks of dysrhythmia or abnormal brain activity when the channel's function or expression is altered[1][2][3][5][6][7].

Other names

G protein-gated inwardly rectifying potassium channelGIRK channel (GIRK = G protein-gated inwardly rectifying potassium channel)Kir3.1, Kir3.2, Kir3.3, Kir3.4 (subunit members)KCNJ3, KCNJ5, KCNJ6, KCNJ9 (gene symbols for individual subunits)Girk1, Girk2, Girk3, Girk4

Direct gating via G protein βγ subunits upon GPCR activation. Modulation by membrane phosphoinositides (PIP2). Regulation by protein-protein interaction (e.g., via RGS proteins). Blockade or facilitation of the inward rectifying potassium current.