Kir7.1 channels
| Channel name | Kir7.1 |
| Description | Inwardly rectifying potassium channel Kir7.1 subunit |
| Other names | Kir1.4 |
| Molecular information | Human (KCNJ13): 360aa, Locus ID: 3769, GenBank: AF061118, AJ006128, AJ007557, NM_002242, PMID: 9620703,1 9786970,2 9738472,3 chr. 2q374 |
| Rat (Kcnj13): 360aa, Locus ID: 94341, GenBank: AJ006129, NM_053600, PMID: 9786970,2 chr. 9q35 | |
| Mouse: sequence not in the database | |
| Associated subunits | None reported |
| Functional assays | Voltage-clamp |
| Current | IKir7.1 |
| Conductance | 50fS to 1pS (in 140 mM K+), 2pS (recombinant and in bovine retinal epithelial cells)5 |
| Ion selectivity | Rb+ ≫ K+ > Na+ > Cs+ > Li+ |
| Activation | Activated at voltages lower than — 130 mV; activation is faster than 1 ms at all voltages |
| Inactivation | Essentially noninactivating |
| Activators | None |
| Gating inhibitors | None |
| Blockers | Low sensitivity to Ba2+ (IC50 = 1 mM) and Cs+ (IC50 ∼30 mM), relatively insensitive to block by tetraethylammonium (> 10 mM), 4-aminopyridine (IC50 ∼10 mM) |
| Radioligands | None |
| Channel distribution | Purkinje cells of the cerebellum, pyramidal cells of the hippocampus, choroid plexus, retinal pigment epithelium, thyroid gland, kidney (basolateral membrane of epithelial cells of the proximal tubule), small intestine, stomach, prostate, testis, lung6,7 |
| Physiological functions | Contributes to resting membrane potential of neurons and epithelial cells, transepithelial potassium transport, K+ excretion |
| Mutations and pathophysiology | The M125R mutation increases conductance to ∼1pS and sensitivity to block by Ba2+8 |
| Pharmacological significance | Possible site of side effects for calcium channel blockers |
| Comments | Functional coupling to Na+,K+-ATPase in apical membranes |
aa, amino acids; chr., chromosome.
↵1. Krapivinsky G, Medina I, Eng L, Krapivinsky L, Yang Y, and Clapham DE (1998) A novel inward rectifier K+ channel with unique pore properties. Neuron 20:995-1005
↵2. Döring F, Derst C, Wischmeyer E, Schneggenburger R, Karschin C, Daut J, and Karschin A (1998) The epithelial inward rectifier channel Kir7.1 displays unusual K+ permeation properties. J Neurosci 18: 8625-8636
↵3. Partiseti M, Collura V, Agnel M, Culouscou J-M, and Graham D (1998) Cloning and characterization of a novel human inwardly rectifying potassium channel predominantly expressed in small intestine. FEBS Lett 434:171-176
↵4. Derst C, Döring F, Preisig-Müller R, Daut J, Karschin A, Jeck N, Weber S, Engel H, and Grzeschik K-H (1998) Partial gene structure and assignment to chromosome 2q37 of the human inwardly rectifying K+ channel (Kir7.1) gene (KCNJ13). Genomics 54: 560-563
↵5. Shimura M, Yuan Y, Chang JT, Zjang S, Campochiaro PA, Zack DJ, and Hughes BA (2001) Expression and permeation properties of the K+ channel Kir7.1 in the retinal pigment epithelium. J Physiol 531:329-346
↵6. Nakamura N, Suzuki Y, Sakuta H, Ookata K, and Kawahara K (1999) Inwardly rectifying K+ channel Kir7.1 is highly expressed in thyroid follicular cells, intestinal epithelial cells, and choroid plexus epithelial cells: implication for a functional coupling with Na+,K+-ATPase. Biochem J 342:329-336
↵7. Kusaka S, Inanobe A, Fujita A, Makino Y, Tanemoto M, Matsushita K, Tano Y, and Kurachi Y (2001) Functional Kir7.1 channels localized at the root of apical processes in rat retinal pigment epithelium. J Physiol 531:27-36
↵8. Wischmeyer E, Döring F, and Karschin A (2000) Stable cation coordination at a single outer pore residue defines permeation properties in Kir channels. FEBS Lett 466:115-120