Molecular mechanism of pharmacological activation of BK channels

Proc Natl Acad Sci U S A. 2012 Feb 28;109(9):3552-7. doi: 10.1073/pnas.1114321109. Epub 2012 Feb 13.

Abstract

Large-conductance voltage- and Ca(2+)-activated K(+) (Slo1 BK) channels serve numerous cellular functions, and their dysregulation is implicated in various diseases. Drugs activating BK channels therefore bear substantial therapeutic potential, but their deployment has been hindered in part because the mode of action remains obscure. Here we provide mechanistic insight into how the dehydroabietic acid derivative Cym04 activates BK channels. As a representative of NS1619-like BK openers, Cym04 reversibly left-shifts the half-activation voltage of Slo1 BK channels. Using an established allosteric BK gating model, the Cym04 effect can be simulated by a shift of the voltage sensor and the ion conduction gate equilibria toward the activated and open state, respectively. BK activation by Cym04 occurs in a splice variant-specific manner; it does not occur in such Slo1 BK channels using an alternative neuronal exon 9, which codes for the linker connecting the transmembrane segment S6 and the cytosolic RCK1 domain--the S6/RCK linker. In addition, Cym04 does not affect Slo1 BK channels with a two-residue deletion within this linker. Mutagenesis and model-based gating analysis revealed that BK openers, such as Cym04 and NS1619 but not mallotoxin, activate BK channels by functionally interacting with the S6/RCK linker, mimicking site-specific shortening of this purported passive spring, which transmits force from the cytosolic gating ring structure to open the channel's gate.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abietanes / pharmacology*
  • Allosteric Regulation
  • Amino Acid Sequence
  • HEK293 Cells
  • Humans
  • Ion Channel Gating / drug effects*
  • Ion Channel Gating / physiology
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / chemistry
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / drug effects*
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / genetics
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / metabolism
  • Membrane Potentials
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Patch-Clamp Techniques
  • Potassium / metabolism*
  • Protein Conformation
  • Protein Isoforms / chemistry
  • Protein Isoforms / drug effects
  • Protein Isoforms / metabolism
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / drug effects
  • Recombinant Fusion Proteins / metabolism

Substances

  • Abietanes
  • Cym04
  • KCNMA1 protein, human
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
  • Protein Isoforms
  • Recombinant Fusion Proteins
  • dehydroabietic acid
  • Potassium