A structural motif in the C-terminal tail of slo1 confers carbon monoxide sensitivity to human BK Ca channels

Pflugers Arch. 2008 Jun;456(3):561-72. doi: 10.1007/s00424-007-0439-4. Epub 2008 Jan 5.

Abstract

Carbon monoxide (CO) is a potent activator of large conductance, calcium-dependent potassium (BK Ca) channels of vascular myocytes and carotid body glomus cells or when heterologously expressed. Using the human BK Ca channel alpha1-subunit (hSlo1; KCNMA1) stably and transiently expressed in human embryonic kidney 293 cells, the mechanism and structural basis of channel activation by CO was investigated in inside-out, excised membrane patches. Activation by CO was concentration dependent (EC50 approximately 20 microM), rapid, reversible, and evoked a shift in the V 0.5 of -20 mV. CO evoked no changes in either single channel conductance or in deactivation rate but augmented channel activation rate. Activation was independent of the redox state of the channel, or associated compounds/protein partners, and was partially dependent on [Ca2+]i in the physiological range (100-1,000 nM). Importantly, CO "super-stimulated" BK Ca activity even in saturating [Ca2+]i. Single or double mutation of two histidine residues previously implicated in CO sensing did not suppress CO activation but replacing the S9-S10 module of the C-terminal of Slo1 with that of Slo3 completely prevented the action of CO. These findings show that a motif in the S9-S10 part of the C-terminal is essential for CO activation and suggest that this gas transmitter activates the BK Ca channel by redox-independent changes in gating.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Binding Sites
  • Calcium / metabolism
  • Carbon Monoxide / metabolism*
  • Cell Line
  • Humans
  • Ion Channel Gating*
  • Kinetics
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / chemistry
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / genetics
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / metabolism*
  • Membrane Potentials
  • Mutagenesis, Site-Directed
  • Oxidation-Reduction
  • Patch-Clamp Techniques
  • Protein Binding
  • Protein Conformation
  • Protein Structure, Tertiary
  • Transfection

Substances

  • KCNMA1 protein, human
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
  • Carbon Monoxide
  • Calcium