Small conductance Ca2+-activated K+ channels and calmodulin. Cell surface expression and gating

Wei Sheng Lee, Thu Jennifer Ngo-Anh, Andrew Bruening-Wright, James Maylie, John P. Adelman

Research output: Contribution to journalArticle

78 Scopus citations

Abstract

Small conductance Ca2+-activated K+ channels (SK channels) are heteromeric complexes of pore-forming α subunits and constitutively bound calmodulin (CaM). The binding of CaM is mediated in part by the electrostatic interaction between residues Arg-464 and Lys-467 of SK2 and Glu-84 and Glu-87 of CaM. Heterologous expression of the double charge reversal in SK2, SK2 R464E/K467E (SK2:64/67), did not yield detectable surface expression or channel activity in whole cell or inside-out patch recordings. Coexpression of SK2:64/67 with wild type CaM or CAM1,2,3,4 a mutant lacking the ability to bind Ca2+, rescued surface expression. In patches from cells coexpressing SK2:64/67 and wild type CaM, currents were recorded immediately following excision into Ca2+-containing solution but disappeared within minutes after excision or immediately upon exposure to Ca2+-free solution and were not reactivated upon reapplication of Ca2+-containing solution. Channel activity was restored by application of purified recombinant Ca2+-CaM or exposure to Ca2+-free CaM followed by application of Ca2+-containing solution. Coexpression of the double charge reversal E84R/E87K in CaM (CaM:84/87) with SK2:64/67 reconstituted stable Ca2+-dependent channel activity that was not lost with exposure to Ca2+-free solution. Therefore, Ca2+-independent interactions with CaM are required for surface expression of SK channels, whereas the constitutive association between the two channel subunits is not an essential requirement for gating.

Original languageEnglish (US)
Pages (from-to)25940-25946
Number of pages7
JournalJournal of Biological Chemistry
Volume278
Issue number28
DOIs
StatePublished - Jul 11 2003

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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