title: Imaging nanometer domains of beta-adrenergic receptor complexes on the surface of cardiac myocytes.
abstract: 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.
authors.affiliation: The Steacie Institute for Molecular Sciences, National Research Council Canada, 100 Sussex Drive, Ottawa, Canada K1A 0R6.
authors.forename: Anatoli
authors.initials: A
authors.lastname: Ianoul
authors.forename: Donna D
authors.initials: DD
authors.lastname: Grant
authors.forename: Yanouchka
authors.initials: Y
authors.lastname: Rouleau
authors.forename: Mahmud
authors.initials: M
authors.lastname: Bani-Yaghoub
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Johnston
authors.forename: John Paul
authors.initials: JP
authors.lastname: Pezacki
mesh_terms: 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
chemical_list: D005456:Fluorescent Dyes; D046912:Multiprotein Complexes; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2