Domains responsible for constitutive and Ca2+-dependent interactions between calmodulin and small conductance Ca2+-activated potassium channels

John E. Keen, Radwan Khawaled, David Farrens, Torben Neelands, Andre Rivard, Chris T. Bond, Aaron Janowsky, Bernd Fakler, John Adelman, James Maylie

Research output: Contribution to journalArticle

182 Citations (Scopus)

Abstract

Small conductance Ca2+-activated potassium channels (SK channels) are coassembled complexes of pore-forming SK a subunits and calmodulin. We proposed a model for channel activation in which Ca2+ binding to calmodulin induces conformational rearrangements in calmodulin and the a subunits that result in channel gating. We now report fluorescence measurements that indicate conformational changes in the a subunit after calmodulin binding and Ca2+ binding to the α subunit-calmodulin complex. Two-hybrid experiments showed that the Ca2+-independent interaction of calmodulin with the subunits requires only the C-terminal domain of calmodulin and is mediated by two noncontiguous subregions; the ability of the E-F hands to bind Ca2+ is not required. Although SK α subunits lack a consensus calmodulin-binding motif, mutagenesis experiments identified two positively charged residues required for Ca2+-independent interactions with calmodulin. Electrophysiological recordings of SK2 channels in membrane patches from oocytes coexpressing mutant calmodulins revealed that channel gating is mediated by Ca2+ binding to the first and second E-F hand motifs in the N- terminal domain of calmodulin. Taken together, the results support a calmodulin- and Ca2+calmodulin-dependent conformational change in the channel α subunits, in which different domains of calmodulin are responsible for Ca2+-dependent and Ca2+-independent interactions. In addition, calmodulin is associated with each α subunit and must bind at least one Ca2+ ion for channel gating. Based on these results, a state model for Ca2+ gating was developed that simulates alterations in SK channel Ca2+ sensitivity and cooperativity associated with mutations in CaM.

Original languageEnglish (US)
Pages (from-to)8830-8838
Number of pages9
JournalJournal of Neuroscience
Volume19
Issue number20
StatePublished - Oct 15 1999

Fingerprint

Potassium Channels
Calmodulin
Small-Conductance Calcium-Activated Potassium Channels
Ion Channel Gating
Hand
Ion Channels
Mutagenesis
Oocytes

Keywords

  • Afterhyperpolarization
  • Ca- independent interactions
  • Ca-gating
  • Calmodulin
  • SK channels
  • State model

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Domains responsible for constitutive and Ca2+-dependent interactions between calmodulin and small conductance Ca2+-activated potassium channels. / Keen, John E.; Khawaled, Radwan; Farrens, David; Neelands, Torben; Rivard, Andre; Bond, Chris T.; Janowsky, Aaron; Fakler, Bernd; Adelman, John; Maylie, James.

In: Journal of Neuroscience, Vol. 19, No. 20, 15.10.1999, p. 8830-8838.

Research output: Contribution to journalArticle

Keen, John E. ; Khawaled, Radwan ; Farrens, David ; Neelands, Torben ; Rivard, Andre ; Bond, Chris T. ; Janowsky, Aaron ; Fakler, Bernd ; Adelman, John ; Maylie, James. / Domains responsible for constitutive and Ca2+-dependent interactions between calmodulin and small conductance Ca2+-activated potassium channels. In: Journal of Neuroscience. 1999 ; Vol. 19, No. 20. pp. 8830-8838.
@article{8f7b9beb35504ce1a0b437fb301c97f4,
title = "Domains responsible for constitutive and Ca2+-dependent interactions between calmodulin and small conductance Ca2+-activated potassium channels",
abstract = "Small conductance Ca2+-activated potassium channels (SK channels) are coassembled complexes of pore-forming SK a subunits and calmodulin. We proposed a model for channel activation in which Ca2+ binding to calmodulin induces conformational rearrangements in calmodulin and the a subunits that result in channel gating. We now report fluorescence measurements that indicate conformational changes in the a subunit after calmodulin binding and Ca2+ binding to the α subunit-calmodulin complex. Two-hybrid experiments showed that the Ca2+-independent interaction of calmodulin with the subunits requires only the C-terminal domain of calmodulin and is mediated by two noncontiguous subregions; the ability of the E-F hands to bind Ca2+ is not required. Although SK α subunits lack a consensus calmodulin-binding motif, mutagenesis experiments identified two positively charged residues required for Ca2+-independent interactions with calmodulin. Electrophysiological recordings of SK2 channels in membrane patches from oocytes coexpressing mutant calmodulins revealed that channel gating is mediated by Ca2+ binding to the first and second E-F hand motifs in the N- terminal domain of calmodulin. Taken together, the results support a calmodulin- and Ca2+calmodulin-dependent conformational change in the channel α subunits, in which different domains of calmodulin are responsible for Ca2+-dependent and Ca2+-independent interactions. In addition, calmodulin is associated with each α subunit and must bind at least one Ca2+ ion for channel gating. Based on these results, a state model for Ca2+ gating was developed that simulates alterations in SK channel Ca2+ sensitivity and cooperativity associated with mutations in CaM.",
keywords = "Afterhyperpolarization, Ca- independent interactions, Ca-gating, Calmodulin, SK channels, State model",
author = "Keen, {John E.} and Radwan Khawaled and David Farrens and Torben Neelands and Andre Rivard and Bond, {Chris T.} and Aaron Janowsky and Bernd Fakler and John Adelman and James Maylie",
year = "1999",
month = "10",
day = "15",
language = "English (US)",
volume = "19",
pages = "8830--8838",
journal = "Journal of Neuroscience",
issn = "0270-6474",
publisher = "Society for Neuroscience",
number = "20",

}

TY - JOUR

T1 - Domains responsible for constitutive and Ca2+-dependent interactions between calmodulin and small conductance Ca2+-activated potassium channels

AU - Keen, John E.

AU - Khawaled, Radwan

AU - Farrens, David

AU - Neelands, Torben

AU - Rivard, Andre

AU - Bond, Chris T.

AU - Janowsky, Aaron

AU - Fakler, Bernd

AU - Adelman, John

AU - Maylie, James

PY - 1999/10/15

Y1 - 1999/10/15

N2 - Small conductance Ca2+-activated potassium channels (SK channels) are coassembled complexes of pore-forming SK a subunits and calmodulin. We proposed a model for channel activation in which Ca2+ binding to calmodulin induces conformational rearrangements in calmodulin and the a subunits that result in channel gating. We now report fluorescence measurements that indicate conformational changes in the a subunit after calmodulin binding and Ca2+ binding to the α subunit-calmodulin complex. Two-hybrid experiments showed that the Ca2+-independent interaction of calmodulin with the subunits requires only the C-terminal domain of calmodulin and is mediated by two noncontiguous subregions; the ability of the E-F hands to bind Ca2+ is not required. Although SK α subunits lack a consensus calmodulin-binding motif, mutagenesis experiments identified two positively charged residues required for Ca2+-independent interactions with calmodulin. Electrophysiological recordings of SK2 channels in membrane patches from oocytes coexpressing mutant calmodulins revealed that channel gating is mediated by Ca2+ binding to the first and second E-F hand motifs in the N- terminal domain of calmodulin. Taken together, the results support a calmodulin- and Ca2+calmodulin-dependent conformational change in the channel α subunits, in which different domains of calmodulin are responsible for Ca2+-dependent and Ca2+-independent interactions. In addition, calmodulin is associated with each α subunit and must bind at least one Ca2+ ion for channel gating. Based on these results, a state model for Ca2+ gating was developed that simulates alterations in SK channel Ca2+ sensitivity and cooperativity associated with mutations in CaM.

AB - Small conductance Ca2+-activated potassium channels (SK channels) are coassembled complexes of pore-forming SK a subunits and calmodulin. We proposed a model for channel activation in which Ca2+ binding to calmodulin induces conformational rearrangements in calmodulin and the a subunits that result in channel gating. We now report fluorescence measurements that indicate conformational changes in the a subunit after calmodulin binding and Ca2+ binding to the α subunit-calmodulin complex. Two-hybrid experiments showed that the Ca2+-independent interaction of calmodulin with the subunits requires only the C-terminal domain of calmodulin and is mediated by two noncontiguous subregions; the ability of the E-F hands to bind Ca2+ is not required. Although SK α subunits lack a consensus calmodulin-binding motif, mutagenesis experiments identified two positively charged residues required for Ca2+-independent interactions with calmodulin. Electrophysiological recordings of SK2 channels in membrane patches from oocytes coexpressing mutant calmodulins revealed that channel gating is mediated by Ca2+ binding to the first and second E-F hand motifs in the N- terminal domain of calmodulin. Taken together, the results support a calmodulin- and Ca2+calmodulin-dependent conformational change in the channel α subunits, in which different domains of calmodulin are responsible for Ca2+-dependent and Ca2+-independent interactions. In addition, calmodulin is associated with each α subunit and must bind at least one Ca2+ ion for channel gating. Based on these results, a state model for Ca2+ gating was developed that simulates alterations in SK channel Ca2+ sensitivity and cooperativity associated with mutations in CaM.

KW - Afterhyperpolarization

KW - Ca- independent interactions

KW - Ca-gating

KW - Calmodulin

KW - SK channels

KW - State model

UR - http://www.scopus.com/inward/record.url?scp=0033570334&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033570334&partnerID=8YFLogxK

M3 - Article

C2 - 10516302

AN - SCOPUS:0033570334

VL - 19

SP - 8830

EP - 8838

JO - Journal of Neuroscience

JF - Journal of Neuroscience

SN - 0270-6474

IS - 20

ER -