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
Famous quotes containing the words role of, role and/or channels:
“The traditional American husband and father had the responsibilities—and the privileges—of playing the role of primary provider. Sharing that role is not easy. To yield exclusive access to the role is to surrender some of the potential for fulfilling the hero fantasy—a fantasy that appeals to us all. The loss is far from trivial.”
—Faye J. Crosby (20th century)
“American feminists have generally stressed the ways in which men and women should be equal and have therefore tried to put aside differences.... Social feminists [in Europe] ... believe that men and society at large should provide systematic support to women in recognition of their dual role as mothers and workers.”
—Sylvia Ann Hewitt (20th century)
“It is worth the while to detect new faculties in man,—he is so much the more divine; and anything that fairly excites our admiration expands us. The Indian, who can find his way so wonderfully in the woods, possesses an intelligence which the white man does not,—and it increases my own capacity, as well as faith, to observe it. I rejoice to find that intelligence flows in other channels than I knew. It redeems for me portions of what seemed brutish before.”
—Henry David Thoreau (1817–1862)