Norepinephrine- and epinephrine-induced distinct beta2-adrenoceptor signaling is dictated by GRK2 phosphorylation in cardiomyocytes.
Agonist-dependent activation of G protein-coupled receptors induces diversified receptor cellular and signaling properties. Norepinephrine (NE) and epinephrine (Epi) are two endogenous ligands that activate adrenoceptor (AR) signals in a variety of physiological stress responses in animals. Here we use cardiomyocyte contraction rate response to analyze the endogenous beta(2)AR signaling induced by Epi or NE in cardiac tissue. The Epi-activated beta(2)AR induced a rapid contraction rate increase that peaked at 4 min after stimulation. In contrast, the NE-activated beta(2)AR induced a much slower contraction rate increase that peaked at 10 min after stimulation. Whereas both drugs activated beta(2)AR coupling to G(s) proteins, only Epi-activated receptors were capable of coupling to G(i) proteins. Subsequent studies showed that the Epi-activated beta(2)AR underwent a rapid phosphorylation by G protein-coupled receptor kinase 2 (GRK2) and subsequent dephosphorylation on serine residues 355 and 356, which was critical for sufficient receptor recycling and G(i) coupling. In contrast, the NE-activated beta(2)ARs underwent slow GRK2 phosphorylation, receptor internalization and recycling, and failed to couple to G(i). Moreover, inhibiting beta(2)AR phosphorylation by betaARK C terminus or dephosphorylation by okadaic acid prevented sufficient recycling and G(i) coupling. Together, our data revealed that distinct temporal phosphorylation of beta(2)AR on serine 355 and 356 by GRK2 plays a critical role for dictating receptor cellular events and signaling properties induced by Epi or NE in cardiomyocytes. This study not only helps us understand the endogenous agonist-dependent beta(2)AR signaling in animal heart but also offers an example of how G protein-coupled receptor signaling may be finely regulated by GRK in physiological settings.
Department of Molecular and Integrative Physiology, University of Illinois at Urbana Champaign, Urbana, Illinois 61822, USA.
Yongyu
Y
Wang
Vania
V
De Arcangelis
Xiaoguang
X
Gao
Biswarathan
B
Ramani
Yi-sook
YS
Jung
Yang
Y
Xiang
D000316:Adrenergic alpha-Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D000818:Animals; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004837:Epinephrine / Q000378:metabolism / Q000494:pharmacology*; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology*; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects*; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D013997:Time Factors
D000316:Adrenergic alpha-Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D004791:Enzyme Inhibitors; D018343:Receptors, Adrenergic, beta-2; D019319:Okadaic Acid; C496568:GRK2 protein, mouse; D054769:G-Protein-Coupled Receptor Kinase 2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D009638:Norepinephrine; D004837:Epinephrine