Channelpedia

Slo2b

Description: potassium channel, subfamily T, member 2
Gene: Kcnt2     Synonyms: Slo2b, kcnt2

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Introduction

KNa channels were first identified in guinea pig cardiomyocytes (Kameyama et al., 1984 [1149]). Subsequently, similar channels were reported in a variety of neurons (Bader et al., 1985 [1150]; Dryer et al., 1989 [1151]; Schwindt et al., 1989 [1152]; Dryer, 1991 [1145]; Egan et al., 1992a [1153]; Haimann et al., 1992 [1143]; Dale, 1993 [13; Safronov and Vogel, 1996 [1155]; Bischoff et al., 1998 [1144]). Like Ca2+ -activated BK and SK channels, the properties of KNa channels appear to be diverse. The reported unitary conductances of these channels range from 105 to 200 pS, and half-maximal activation by Na+ occurs between 7 and 80 mM, depending on cell type and recording conditions (Dryer, 1994 [1148]).


Experimental data


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Gene

KCNT2 (also known as SLICK; KCa4.2; SLO2.1; MGC119610; MGC119611; MGC119612; MGC119613; RP11-58O13.1) encodes Slo2b, a potassium channel, subfamily T, member 2.

http://www.ncbi.nlm.nih.gov/gene/343450

RGD ID Chromosome Position Species
735074 13 53407504-53803012 Rat
1622042 1 142142834-142506838 Mouse
1351112 1 196194913-196577499 Human

Kcnt2 : potassium channel, subfamily T, member 2


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Transcript

Acc No Sequence Length Source
NM_198762 n/A n/A NCBI
NM_001081027 n/A n/A NCBI
NM_198503 n/A n/A NCBI

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Ontology

Accession Name Definition Evidence
GO:0005886 plasma membrane The membrane surrounding a cell that separates the cell from its external environment. It consists of a phospholipid bilayer and associated proteins. IEA
GO:0016021 integral to membrane Penetrating at least one phospholipid bilayer of a membrane. May also refer to the state of being buried in the bilayer with no exposure outside the bilayer. When used to describe a protein, indicates that all or part of the peptide sequence is embedded in the membrane. IEA
GO:0016020 membrane Double layer of lipid molecules that encloses all cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins. IEA

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Interaction

The activity of Slick channels is substantially more sensitive than Slack to changes in intracellular Cl-, and Slick open probability is significant even in the absence of Na+. Moreover, Slick contains a regulatory nucleotidebinding site that is responsible for ATP-dependent inhibition of channel activity. (Bhattacharjee [1141])


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Protein


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Structure


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Distribution


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Expression

Slick (Slo2.1) is selectively expressed in the nervous system and heart. (Bhattacharjee [1141])


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Functional

The physiological roles of KNa channels (such as Slo2b) appear to be distinct in different cell types. For example, in quail trigeminal ganglion neurons and in dorsal root ganglion neurons, it has been suggested that KNa channels regulate the resting membrane potential (Haimann et al., 1992 [1143]; Bischoff et al., 1998 [1144]). In other neurons, KNa channels have been implicated in an apamin-insensitive, Na+-dependent slow afterhyperpolarization (AHP) that follows a burst of action potentials (Dryer, 1994 [1145]). In ferret perigeniculate neurons, such a Na+-dependent slow AHP is an important component of spindle wave activity (Kim and McCormick, 1998 [1146]). It has also been proposed that KNa channels may be activated by a single action potential and may therefore play a role in determining the duration of action potentials (Bertrand et al., 1989 [1147]), although is unclear whether the amount of Na+ influx through a TTX-sensitive Na+ channel during a single action potential is normally sufficient to activate KNa channels (Dryer, 1994 [1148], 1991 [1145]). Activation may depend on the relative rates of influx, diffusion, and extrusion of Na+, the proximity of KNa channels to the source of Na+, and the particular geometry of the space occupied by KNa channels in a given cell type (Dryer, 1994 [1148], 1991 [1145]).

The properties of the Slick channel indicate that its activation by intense neuronal activity or by hypoxia may hyperpolarize specific neurons in the brain and the heart, where the channel is expressed, thereby limiting excitability and energy consumption to maintain cell viability. (Bhattacharjee [1141])


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Kinetics

With similar single-channel conductance to Slack, Slick also rectifies outwardly and is activated by intracellular Na+. In marked contrast to Slack, however, Slick activation occurs very rapidly with step changes in voltage, whereas Slack activation increases with time after a step depolarization. (Bhattacharjee [1141])


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Model


References

Bhattacharjee A et al. Slick (Slo2.1), a rapidly-gating sodium-activated potassium channel inhibited by ATP.
J. Neurosci., 2003 Dec 17 , 23 (11681-91).

Bischoff U et al. Na+-activated K+ channels in small dorsal root ganglion neurones of rat.
J. Physiol. (Lond.), 1998 Aug 1 , 510 ( Pt 3) (743-54).

Bertrand D et al. KNa. A sodium-activated potassium current.
Pflugers Arch., 1989 , 414 Suppl 1 (S76-9).

Dryer SE Na(+)-activated K+ channels: a new family of large-conductance ion channels.
Trends Neurosci., 1994 Apr , 17 (155-60).

Kameyama M et al. Intracellular Na+ activates a K+ channel in mammalian cardiac cells.
Nature, 1984 May 24-30 , 309 (354-6).

Bader CR et al. Sodium-activated potassium current in cultured avian neurones.
Nature, 1985 Oct 10-16 , 317 (540-2).

Dryer SE et al. A Na+-activated K+ current in cultured brain stem neurones from chicks.
J. Physiol. (Lond.), 1989 Mar , 410 (283-96).

Safronov BV et al. Properties and functions of Na(+)-activated K+ channels in the soma of rat motoneurones.
J. Physiol. (Lond.), 1996 Dec 15 , 497 ( Pt 3) (727-34).


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Credits

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