Caveolins and intracellular calcium regulation in human airway smooth muscle.
Regulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) is a key factor in airway smooth muscle (ASM) tone. In vascular smooth muscle, specialized membrane microdomains (caveolae) expressing the scaffolding protein caveolin-1 are thought to facilitate cellular signal transduction. In human ASM cells, we tested the hypothesis that caveolae mediate Ca(2+) responses to agonist stimulation. Fluorescence immunocytochemistry with confocal microscopy, as well as Western blot analysis, was used to determine that agonist receptors (M(3) muscarinic, bradykinin, and histamine) and store-operated Ca(2+) entry (SOCE)-regulatory mechanisms colocalize with caveolin-1. Although caveolin-2 coexpressed with caveolin-1, caveolin-3 was absent. In fura 2-loaded ASM cells, [Ca(2+)](i) responses to 1 microM ACh, 10 microM histamine, and 10 nM bradykinin, as well as SOCE, were attenuated (each to a different extent) after disruption of caveolae by the cholesterol-chelating drug methyl-beta-cyclodextrin. Transfection of ASM cells with 50 nM caveolin-1 small interfering RNA significantly weakened caveolin-1 expression and blunted [Ca(2+)](i) responses to bradykinin and histamine, as well as SOCE, but the response to ACh was less intense. These results indicate that caveolae are present in ASM and that caveolin-1 contributes to regulation of [Ca(2+)](i) responses to agonist.
Prakash
Y S
YS
Departments of Anesthesiology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA . prakash.ys@mayo.edu
Thompson
Michael A
MA
Vaa
Brianna
B
Matabdin
Ihaab
I
Peterson
Timothy E
TE
He
Tongrong
T
Pabelick
Christina M
CM
D015153:Blotting, Western; D001920:Bradykinin / Q000494:pharmacology; D001980:Bronchi / Q000166:cytology / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D021941:Caveolae / Q000502:physiology*; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D051243:Caveolin 2 / Q000235:genetics / Q000378:metabolism*; D051244:Caveolin 3 / Q000235:genetics / Q000378:metabolism*; D004594:Electrophysiology; D005453:Fluorescence; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D009130:Muscle, Smooth / Q000502:physiology*; D043587:Receptor, Muscarinic M3 / Q000235:genetics / Q000378:metabolism; D018002:Receptors, Bradykinin / Q000235:genetics / Q000378:metabolism; D011968:Receptors, Histamine / Q000235:genetics / Q000378:metabolism; D012137:Respiratory System / Q000166:cytology / Q000378:metabolism
D051242:Caveolin 1; D051243:Caveolin 2; D051244:Caveolin 3; D043587:Receptor, Muscarinic M3; D018002:Receptors, Bradykinin; D011968:Receptors, Histamine; D006632:Histamine; D001920:Bradykinin; D002118:Calcium