Type 1 IP3 receptors activate BKCa channels via local molecular coupling in arterial smooth muscle cells

J Gen Physiol. 2010 Sep;136(3):283-91. doi: 10.1085/jgp.201010453. Epub 2010 Aug 16.


Plasma membrane large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels and sarcoplasmic reticulum inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) are expressed in a wide variety of cell types, including arterial smooth muscle cells. Here, we studied BK(Ca) channel regulation by IP(3) and IP(3)Rs in rat and mouse cerebral artery smooth muscle cells. IP(3) activated BK(Ca) channels both in intact cells and in excised inside-out membrane patches. IP(3) caused concentration-dependent BK(Ca) channel activation with an apparent dissociation constant (K(d)) of approximately 4 microM at physiological voltage (-40 mV) and intracellular Ca(2+) concentration ([Ca(2+)](i); 10 microM). IP(3) also caused a leftward-shift in BK(Ca) channel apparent Ca(2+) sensitivity and reduced the K(d) for free [Ca(2+)](i) from approximately 20 to 12 microM, but did not alter the slope or maximal P(o). BAPTA, a fast Ca(2+) buffer, or an elevation in extracellular Ca(2+) concentration did not alter IP(3)-induced BK(Ca) channel activation. Heparin, an IP(3)R inhibitor, and a monoclonal type 1 IP(3)R (IP(3)R1) antibody blocked IP(3)-induced BK(Ca) channel activation. Adenophostin A, an IP(3)R agonist, also activated BK(Ca) channels. IP(3) activated BK(Ca) channels in inside-out patches from wild-type (IP(3)R1(+/+)) mouse arterial smooth muscle cells, but had no effect on BK(Ca) channels of IP(3)R1-deficient (IP(3)R1(-/-)) mice. Immunofluorescence resonance energy transfer microscopy indicated that IP(3)R1 is located in close spatial proximity to BK(Ca) alpha subunits. The IP(3)R1 monoclonal antibody coimmunoprecipitated IP(3)R1 and BK(Ca) channel alpha and beta1 subunits from cerebral arteries. In summary, data indicate that IP(3)R1 activation elevates BK(Ca) channel apparent Ca(2+) sensitivity through local molecular coupling in arterial smooth muscle cells.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenosine / analogs & derivatives
  • Adenosine / pharmacology
  • Animals
  • Antibodies, Monoclonal / pharmacology
  • Aorta / metabolism
  • Calcium Channels / deficiency
  • Calcium Channels / drug effects
  • Calcium Channels / genetics
  • Calcium Channels / metabolism*
  • Calcium Signaling* / drug effects
  • Cell Membrane / metabolism
  • Cerebral Arteries / metabolism
  • Chelating Agents / pharmacology
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Fluorescence Resonance Energy Transfer
  • Fluorescent Antibody Technique
  • Heparin / pharmacology
  • Immunoprecipitation
  • Inositol 1,4,5-Trisphosphate Receptors
  • Ion Channel Gating
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / drug effects
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / metabolism*
  • Male
  • Membrane Potentials
  • Mice
  • Mice, Knockout
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism*
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism*
  • Patch-Clamp Techniques
  • Potassium Channels / drug effects
  • Potassium Channels / metabolism*
  • Protein Binding
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Cytoplasmic and Nuclear / deficiency
  • Receptors, Cytoplasmic and Nuclear / drug effects
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism*
  • Sarcoplasmic Reticulum / metabolism
  • Time Factors


  • Antibodies, Monoclonal
  • BKCa protein, mouse
  • Calcium Channels
  • Chelating Agents
  • Inositol 1,4,5-Trisphosphate Receptors
  • Itpr1 protein, mouse
  • Itpr1 protein, rat
  • Kcnma1 protein, rat
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
  • Potassium Channels
  • Receptors, Cytoplasmic and Nuclear
  • adenophostin A
  • Egtazic Acid
  • Heparin
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Adenosine