Distinct stoichiometry of BKCa channel tetramer phosphorylation specifies channel activation and inhibition by cAMP-dependent protein kinase

Proc Natl Acad Sci U S A. 2004 Aug 10;101(32):11897-902. doi: 10.1073/pnas.0402590101. Epub 2004 Jul 27.

Abstract

Large conductance voltage- and calcium-activated potassium (BK(Ca)) channels are important signaling molecules that are regulated by multiple protein kinases and protein phosphatases at multiple sites. The pore-forming alpha-subunits, derived from a single gene that undergoes extensive alternative pre-mRNA splicing, assemble as tetramers. Although consensus phosphorylation sites have been identified within the C-terminal domain of alpha-subunits, it is not known whether phosphorylation of all or single alpha-subunits within the tetramer is required for functional regulation of the channel. Here, we have exploited a strategy to study single-ion channels in which both the alpha-subunit splice-variant composition is defined and the number of consensus phosphorylation sites available within each tetramer is known. We have used this approach to demonstrate that cAMP-dependent protein kinase (PKA) phosphorylation of the conserved C-terminal PKA consensus site (S899) in all four alpha-subunits is required for channel activation. In contrast, inhibition of BK(Ca) channel activity requires phosphorylation of only a single alpha-subunit at a splice insert (STREX)-specific PKA consensus site (S4(STREX)). Thus, distinct modes of BK(Ca) channel regulation by PKA phosphorylation exist: an "all-or-nothing" rule for activation and a "single-subunit" rule for inhibition. This essentially digital regulation has important implications for the combinatorial and conditional regulation of BK(Ca) channels by reversible protein phosphorylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Calcium / pharmacology
  • Consensus Sequence
  • Cyclic AMP-Dependent Protein Kinases / physiology*
  • Electrophysiology
  • Mice
  • Phosphorylation
  • Potassium Channels / chemistry*
  • Potassium Channels / metabolism*
  • Protein Isoforms
  • Protein Structure, Quaternary
  • Protein Subunits / metabolism

Substances

  • Potassium Channels
  • Protein Isoforms
  • Protein Subunits
  • Cyclic AMP-Dependent Protein Kinases
  • Calcium