title: Caged ligands to study the role of intracellular GPCRs.
abstract: In addition to cell surface membranes, numerous G protein-coupled receptors (GPCRs) are located on intracellular membranes including the nuclear envelope. Although the role of numerous GPCRs at the cell surface has been well characterized, the physiological function of these same receptors located on intracellular membranes remains to be determined. Here, we employ a novel caged Ang-II analog, cAng-II, to compare the effects of the activation of cell surface versus intracellular angiotensin receptors in intact cardiomyocytes. When added extracellularly to HEK 293 cells, Ang-II and photolysed cAng-II increased ERK1/2 phosphorylation (via AT1R) and cGMP production (AT2R). In contrast unphotolysed cAng-II did not. Cellular uptake of cAng-II was 6-fold greater than that of Ang-II and comparable to the HIV TAT(48-60) peptide. Intracellular photolysis of cAng-II induced an increase in nucleoplasmic Ca(2+) ([Ca(2+)]n) that was greater than that induced by extracellular application of Ang-II. We conclude that cell-permeable ligands that can access intracellular GPCRs may evoke responses distinct from those with access restricted to the same receptor located on the cell surface.
authors.affiliation: Department of Medicine, Université de Montréal, Canada; Montreal Heart Institute, Canada.
authors.forename: Artavazd
authors.initials: A
authors.lastname: Tadevosyan
authors.affiliation: Montreal Heart Institute, Canada.
authors.forename: Louis R
authors.initials: LR
authors.lastname: Villeneuve
authors.affiliation: INRS-Institut Armand-Frappier, Université du Québec, Canada; Laboratoire International Associé Samuel de Champlain, Canada.
authors.forename: Alain
authors.initials: A
authors.lastname: Fournier
authors.affiliation: INRS-Institut Armand-Frappier, Université du Québec, Canada; Laboratoire International Associé Samuel de Champlain, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Chatenet
authors.affiliation: Department of Medicine, Université de Montréal, Canada; Montreal Heart Institute, Canada; Department of Pharmacology and Therapeutics, McGill University, Canada. Electronic address: stanley.nattel@icm-mhi.org.
authors.forename: Stanley
authors.initials: S
authors.lastname: Nattel
authors.affiliation: Department of Medicine, Université de Montréal, Canada; Montreal Heart Institute, Canada; Department of Pharmacology and Therapeutics, McGill University, Canada; Department of Biochemistry and Molecular Medicine, Université de Montréal, Canada. Electronic address: bruce.g.allen@umontreal.ca.
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Allen
mesh_terms: D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004285:Dogs; D057809:HEK293 Cells; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D008024:Ligands; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000378:metabolism*
chemical_list: D008024:Ligands; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D018160:Receptors, Cytoplasmic and Nuclear; D043562:Receptors, G-Protein-Coupled; D000804:Angiotensin II
keywords: Angiotensin II; Angiotensin receptors; Intracrine signalling; Live cell imaging; Nuclear GPCR