KCa4.2 channels
| Channel | KCa4.2 |
| Description | Sodium-activated potassium channel gated by voltage, internal Na+ and Cl-, and inhibited by ATP |
| Other names | Slick, Slo2.1, KCNT2 |
| Molecular information | Human: 1138aa, NM_198503; chr. 1q31.3, KCNT2 |
| Mouse: 1131aa, XM_136252, chr. 1 | |
| Rat: 1142aa, NM_198762, chr. 13q13 | |
| Associated subunits | No β-subunits identified; binding to PSD-95 scaffolding protein via first PDZ domain4 |
| Functional Assays | Voltage-clamp, patch-clamp |
| Current | K+-selective |
| Conductance | 141pS (130 mM symmetric K+), multiple subconductance states1 |
| Ion Selectivity | K+-selective |
| Activation | Gated by voltage (weakly voltage-sensitive) and synergistically by internal Na+ and Cl- (5-fold increase in NPo when Na+ raised from 1–100 mM, with 30 mM Cl-; 5-fold increase in NPo when Cl- raised from 3–130 mM, with 5 mM Na+)1 |
| Inactivation | None |
| Activators | None |
| Blockers | TEA, >60% block by 20 mM; quindine, >90% block by 1.0 mM1 |
| Gating inhibitors | Intracellular ATP, >80% block by 5.0 mM |
| Radioligands | None |
| Channel distribution | Ubiquitous (mouse Slo2.1)5; brain (olfactory bulb, supraoptic nucleus, hippocampus, somatosensory and visual cortex, thalamus, deep cerebellar nucleus, oculomotor nucleus, auditory nuclei), heart2 (rat Slick); neuronal immunohistochemical staining observed in cell bodies and axonal tracts |
| Physiological functions | Not established |
| Mutations and pathophysiology | Not established; C. elegans slo-2 loss-of-function mutants are hypersensitive to hypoxic death4,5 |
| Pharmacological significance | Not established; native KNa channels proposed to protect against hypoxic insult in cardiac muscles3 |
aa, amino acids; chr., chromosome; PDZ, postsynaptic density 95/disc-large/zona occludens; TEA, tetraethylammonium.
↵1. Bhattacharjee A, Gan L, and Kaczmarek LK (2002) Localization of the Slack potassium channel in the rat central nervous system. J Comp Neurol 454:241-254
↵2. Bhattacharjee A, Joiner WJ, Wu M, Yang Y, Sigworth FJ, and Kaczmarek LK (2003) Slick (Slo2.1), a rapidly-gated sodium-activated potassium channel inhibited by ATPJ. Neurosci 23:11681-11691
↵3. Kameyama M, Kakei M, Sato R, Shibasaki T, Matsuda H, and Irisawa H (1984) Intracellular Na+ activates a K+ channel in mammalian cardiac cells. Nature (Lond) 309:354-356
↵4. Yuan A, Dourado M, Butler A, Walton N, Wei A, and Salkoff L (2000) SLO-2, a K+ channel with an unusual Cl- dependence Nat Neurosci 3:771-779
↵5. Yuan A, Santi CM, Wei A, Wang Z-W, Pollak K, Nonet M, Kaczmarek L, Crowder CM, and Salkoff L (2003) The sodium-activated potassium channel is encoded by a member of the Slo gene family. Neuron 37:765-773