Imaging nanometer domains of beta-adrenergic receptor complexes on the surface of cardiac myocytes.
The contraction of cardiac myocytes is initiated by ligand binding to adrenergic receptors contained in nanoscale multiprotein complexes called signalosomes. The composition and number of functional signalosomes within cardiac myocytes defines the molecular basis of the response to adrenergic stimuli. For the first time, we demonstrated the ability of near-field scanning optical microscopy to visualize beta-adrenergic receptors at the nanoscale in situ. On H9C2 cells, mouse neonatal and mouse embryonic cardiac myocytes, we showed that functional receptors are organized into multiprotein domains of approximately 140 nm average diameter. Colocalization experiments in primary cells at the nanometer scale showed that 15-20% of receptors were preassociated in caveolae. These nanoscale complexes were sufficient to effect changes in ligand-induced contraction rate without the requirement for substantial changes in receptor distribution in the cellular membrane. Using fluorescence intensities associated with these nanodomains, we estimated the receptor density within the observed nanometer features and established a lower limit for the number of receptors in the signalosome.
Ianoul
Anatoli
A
The Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, Canada K1A 0R6.
Grant
Donna D
DD
Rouleau
Yanouchka
Y
Bani-Yaghoub
Mahmud
M
Johnston
Linda J
LJ
Pezacki
John Paul
JP
D000818:Animals; D021941:Caveolae / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure*; D005456:Fluorescent Dyes; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D046912:Multiprotein Complexes / Q000096:biosynthesis / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D018342:Receptors, Adrenergic, beta-1 / Q000096:biosynthesis* / Q000737:chemistry; D018343:Receptors, Adrenergic, beta-2 / Q000096:biosynthesis* / Q000737:chemistry
D005456:Fluorescent Dyes; D046912:Multiprotein Complexes; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2