Type 1 IP3 receptors activate BKCa channels via local molecular coupling in arterial smooth muscle cells.
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.
Zhao
Guiling
G
Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
Neeb
Zachary P
ZP
Leo
M Dennis
MD
Pachuau
Judith
J
Adebiyi
Adebowale
A
Ouyang
Kunfu
K
Chen
Ju
J
Jaggar
Jonathan H
JH
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001011:Aorta / Q000378:metabolism; D015220:Calcium Channels / Q000172:deficiency / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002536:Cerebral Arteries / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D005455:Fluorescent Antibody Technique; D006493:Heparin / Q000494:pharmacology; D047468:Immunoprecipitation; D053496:Inositol 1,4,5-Trisphosphate Receptors; D015640:Ion Channel Gating; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013997:Time Factors
D000911:Antibodies, Monoclonal; C530995:BKCa protein, mouse; D015220:Calcium Channels; D002614:Chelating Agents; D053496:Inositol 1,4,5-Trisphosphate Receptors; C025389:Itpr1 protein, mouse; C488910:Itpr1 protein, rat; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D015221:Potassium Channels; D018160:Receptors, Cytoplasmic and Nuclear; C085029:adenophostin A; D004533:Egtazic Acid; D006493:Heparin; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D000241:Adenosine