Role of Kir Channels
Kir channels are found in multiple cell types, including macrophages, cardiac and kidney cells, leukocytes, neurons, and endothelial cells. By mediating a small depolarizing K+ current at negative membrane potentials, they help establish resting membrane potential, and in the case of the Kir3 group, they help mediate inhibitory neurotransmitter responses, but their roles in cellular physiology vary across cell types:
| Location | Function |
| cardiac myocytes | Kir channels close upon depolarization, slowing membrane repolarization and helping maintain a more prolonged cardiac action potential. This type of inward-rectifier channel is distinct from delayed rectifier K+ channels, which help repolarize nerve and muscle cells after action potentials; and potassium leak channels, which provide much of the basis for the resting membrane potential. |
| endothelial cells | Kir channels are involved in regulation of nitric oxide synthase. |
| kidneys | Kir export surplus potassium into collecting tubules for removal in the urine, or alternatively may be involved in the reuptake of potassium back into the body. |
| neurons and in heart cells | G-protein activated IRKs (Kir3) are important regulators, modulated by neurotransmitters. A mutation in the GIRK2 channel leads to the weaver mouse mutation. "Weaver" mutant mice are ataxic and display a neuroinflammation-mediated degeneration of their dopaminergic neurons. Relative to non-ataxic controls, Weaver mutants have deficits in motor coordination and changes in regional brain metabolism. Weaver mice have been examined in labs interested in neural development and disease for over 30 years. |
| pancreatic beta cells | KATP channels (composed of Kir6.2 and SUR1 subunits) control insulin release. |
Read more about this topic: Inward-rectifier Potassium Ion Channel
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