Kir31Kir34

Kir31Kir34 refers to a potential heteromeric inward-rectifier potassium channel formed by assemblies of Kir3.1 and Kir3.4 subunits, members of the GIRK (G protein–gated inwardly rectifying potassium) channel family. GIRK channels assemble as tetramers from four subunits; the exact subunit composition affects conductance, rectification, trafficking, and regulation by G protein signaling. Kir3.1 is encoded by KCNJ3 and Kir3.4 by KCNJ5. Coassembly of these subunits has been reported in some tissues, producing channels with properties distinct from homomeric Kir3.1 or Kir3.4 channels.

Physiological role: Kir31Kir34 channels are activated by Gβγ subunits released from Gi/o-coupled receptors such as GABA_B, certain muscarinic receptors, and adenosine receptors. Opening the channel increases potassium conductance, tends to hyperpolarize the cell, and dampen excitability. In neurons, such channels contribute to slow inhibitory postsynaptic potentials and help regulate synaptic integration; in the heart, GIRK channels influence atrial refractoriness and heart rate.

Biophysical properties and regulation: Like other GIRK channels, Kir31Kir34 require membrane phosphatidylinositol 4,5-bisphosphate (PIP2) for activity and show strong inward rectification. Channel activity is modulated by intracellular signaling cascades, phosphorylation status, and interacting proteins that affect trafficking and localization.

Clinical and research context: Aberrant GIRK signaling has been linked to neurological and cardiovascular disorders. Studying Kir31Kir34 contributes to understanding how subunit composition shapes channel behavior and GPCR-GIRK coupling, with potential implications for drug targeting of neuronal inhibition and cardiac regulation.