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Duan J, Liu H, Zhao F, Yuan Q, Ji Y, Cai X, He X, Li X, Li J, Wu K, Gao T, Zhu S, Lin S, Wang MW, Cheng X, Yin W, Jiang Y, Yang D, Xu HE. GPCR activation and GRK2 assembly by a biased intracellular agonist. Nature 2023; 620:676-681. [PMID: 37532940 DOI: 10.1038/s41586-023-06395-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 07/03/2023] [Indexed: 08/04/2023]
Abstract
Phosphorylation of G-protein-coupled receptors (GPCRs) by GPCR kinases (GRKs) desensitizes G-protein signalling and promotes arrestin signalling, which is also modulated by biased ligands1-6. The molecular assembly of GRKs on GPCRs and the basis of GRK-mediated biased signalling remain largely unknown owing to the weak GPCR-GRK interactions. Here we report the complex structure of neurotensin receptor 1 (NTSR1) bound to GRK2, Gαq and the arrestin-biased ligand SBI-5537. The density map reveals the arrangement of the intact GRK2 with the receptor, with the N-terminal helix of GRK2 docking into the open cytoplasmic pocket formed by the outward movement of the receptor transmembrane helix 6, analogous to the binding of the G protein to the receptor. SBI-553 binds at the interface between GRK2 and NTSR1 to enhance GRK2 binding. The binding mode of SBI-553 is compatible with arrestin binding but clashes with the binding of Gαq protein, thus providing a mechanism for its arrestin-biased signalling capability. In sum, our structure provides a rational model for understanding the details of GPCR-GRK interactions and GRK2-mediated biased signalling.
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Affiliation(s)
- Jia Duan
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Zhongshan, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Heng Liu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Fenghui Zhao
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Qingning Yuan
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Yujie Ji
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xiaoqing Cai
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Xinheng He
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xinzhu Li
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Junrui Li
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Kai Wu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Tianyu Gao
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Shengnan Zhu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Shi Lin
- Research Center for Deepsea Bioresources, Sanya, Hainan, China
| | - Ming-Wei Wang
- Research Center for Deepsea Bioresources, Sanya, Hainan, China
| | - Xi Cheng
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Wanchao Yin
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- Zhongshan Institute for Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Zhongshan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yi Jiang
- Lingang Laboratory, Shanghai, China
| | - Dehua Yang
- University of Chinese Academy of Sciences, Beijing, China.
- The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
- Research Center for Deepsea Bioresources, Sanya, Hainan, China.
| | - H Eric Xu
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
- University of Chinese Academy of Sciences, Beijing, China.
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China.
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Huang CJ, Slusher AL, Whitehurst M, Wells M, Mock JT, Maharaj A, Shibata Y. Acute aerobic exercise mediates G protein-coupled receptor kinase 2 expression in human PBMCs. Life Sci 2015; 135:87-91. [PMID: 26092485 DOI: 10.1016/j.lfs.2015.05.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 04/22/2015] [Accepted: 05/21/2015] [Indexed: 11/17/2022]
Abstract
AIMS G protein-coupled receptor kinase 2 (GRK2), a cytosolic enzyme desensitizing G protein-couple receptors (e.g., β-adrenergic receptors [β-ARs]), is involved in regulation of hypertension, congestive heart failure, and inflammatory response. Since cellular GRK2 levels change quickly in response to exogenous/endogenous stimuli, this study examined whether GRK2 levels in human peripheral blood mononuclear cells (PBMCs) would increase during acute aerobic exercise and be associated with plasma IL-6 and cardiorespiratory fitness levels. MAIN METHODS Eighteen subjects (8 men and 10 women), ages 18 to 30 years, were recruited to perform a 30-minute bout of acute aerobic exercise at 75% VO2max. KEY FINDINGS Our results demonstrated that women exhibited significantly greater exercise-induced GRK2 expression in PBMCs compared to men. IL-6 modulation is independent of GRK2 expression. Furthermore, the percent change in GRK2 expression was negatively correlated with cardiorespiratory fitness levels (relative VO2max), but not plasma IL-6. SIGNIFICANCE Acute aerobic exercise induces a greater GRK2 expression in women than men, while increased cardiorespiratory fitness is associated with exercise-induced GRK2 expression in PBMCs. Gender could be a contributor to regulate this GRK2 responsiveness to acute aerobic exercise.
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Affiliation(s)
- Chun-Jung Huang
- Exercise Biochemistry Laboratory, Department of Exercise Science and Health Promotion, Florida Atlantic University, Boca Raton, FL, USA.
| | - Aaron L Slusher
- Exercise Biochemistry Laboratory, Department of Exercise Science and Health Promotion, Florida Atlantic University, Boca Raton, FL, USA; Department of Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, VA, USA
| | - Michael Whitehurst
- Exercise Biochemistry Laboratory, Department of Exercise Science and Health Promotion, Florida Atlantic University, Boca Raton, FL, USA
| | - Marie Wells
- Exercise Biochemistry Laboratory, Department of Exercise Science and Health Promotion, Florida Atlantic University, Boca Raton, FL, USA
| | - J Thomas Mock
- Exercise Biochemistry Laboratory, Department of Exercise Science and Health Promotion, Florida Atlantic University, Boca Raton, FL, USA; University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Arun Maharaj
- Exercise Biochemistry Laboratory, Department of Exercise Science and Health Promotion, Florida Atlantic University, Boca Raton, FL, USA
| | - Yoshimi Shibata
- Department of Biomedical Science, College of Medicine, Florida Atlantic University, Boca Raton, FL, USA
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Maier D, Cheng S, Faubert D, Hipfner DR. A broadly conserved g-protein-coupled receptor kinase phosphorylation mechanism controls Drosophila smoothened activity. PLoS Genet 2014; 10:e1004399. [PMID: 25009998 PMCID: PMC4091690 DOI: 10.1371/journal.pgen.1004399] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 04/08/2014] [Indexed: 01/20/2023] Open
Abstract
Hedgehog (Hh) signaling is essential for normal growth, patterning, and homeostasis of many tissues in diverse organisms, and is misregulated in a variety of diseases including cancer. Cytoplasmic Hedgehog signaling is activated by multisite phosphorylation of the seven-pass transmembrane protein Smoothened (Smo) in its cytoplasmic C-terminus. Aside from a short membrane-proximal stretch, the sequence of the C-terminus is highly divergent in different phyla, and the evidence suggests that the precise mechanism of Smo activation and transduction of the signal to downstream effectors also differs. To clarify the conserved role of G-protein-coupled receptor kinases (GRKs) in Smo regulation, we mapped four clusters of phosphorylation sites in the membrane-proximal C-terminus of Drosophila Smo that are phosphorylated by Gprk2, one of the two fly GRKs. Phosphorylation at these sites enhances Smo dimerization and increases but is not essential for Smo activity. Three of these clusters overlap with regulatory phosphorylation sites in mouse Smo and are highly conserved throughout the bilaterian lineages, suggesting that they serve a common function. Consistent with this, we find that a C-terminally truncated form of Drosophila Smo consisting of just the highly conserved core, including Gprk2 regulatory sites, can recruit the downstream effector Costal-2 and activate target gene expression, in a Gprk2-dependent manner. These results indicate that GRK phosphorylation in the membrane proximal C-terminus is an evolutionarily ancient mechanism of Smo regulation, and point to a higher degree of similarity in the regulation and signaling mechanisms of bilaterian Smo proteins than has previously been recognized.
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Affiliation(s)
- Dominic Maier
- Institut de recherches cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Department of Anatomy & Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Shuofei Cheng
- Institut de recherches cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Department of Anatomy & Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Denis Faubert
- Institut de recherches cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Proteomics Core Facility, IRCM, Montreal, Quebec, Canada
| | - David R. Hipfner
- Institut de recherches cliniques de Montréal (IRCM), Montreal, Quebec, Canada
- Department of Anatomy & Cell Biology, McGill University, Montreal, Quebec, Canada
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
- * E-mail:
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Ubagai T, Nakano R, Kikuchi H, Ono Y. Gene expression analysis of TREM1 and GRK2 in polymorphonuclear leukocytes as the surrogate biomarkers of acute bacterial infections. Int J Med Sci 2014; 11:215-21. [PMID: 24465168 PMCID: PMC3894407 DOI: 10.7150/ijms.7231] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 12/11/2013] [Indexed: 12/23/2022] Open
Abstract
OBJECTIVE In the acute stage of infectious diseases such as pneumonia and sepsis, sequelae hypercytokinemia and cytokine storm are often observed simultaneously. During bacterial infections, activated polymorphonuclear leukocytes (PMNs) cause inflammation and organ dysfunction in severely ill patients. Gene expression of the triggering receptor on myeloid cells (TREM)-1 and G-coupled-protein receptor kinase (GRK)-2 in PMNs isolated from patients was analysed to identify genes correlated with the severity of pathophysiological conditions. METHODS mRNA levels of TREM1 and GRK2 in the PMNs from 26 patients (13 with pneumonia, 5 with severe sepsis, and 8 with septic shock) were analysed by using quantitative real-time PCR. The synthesised soluble form (s)TREM-1 was incubated with normal PMNs to investigate its biological functions in vitro. RESULTS Copies of TREM1 transcript were 0.7- to 2.1-fold higher in patients with pneumonia compared to those of normal subjects; the average fold-change was 1.1-fold. The mRNA levels of patients suffering from severe sepsis and septic shock were 0.34- and 0.33-fold lower compared to those of healthy subjects, respectively. TREM1 mRNA levels in 5 of 26 patients in convalescent stages recovered to normal levels. The mRNA levels of GRK2 in the PMNs of patients were also downregulated. The synthesised sTREM-1 upregulated the mRNA levels of TREM1 in normal PMNs. CONCLUSIONS TREM1 mRNA levels were inversely correlated with the severity of pathophysiological conditions in acute bacterial infections. The gene expression levels of TREM1 in PMNs isolated from patients with bacterial infections may be used as a surrogate biomarker for determining the severity.
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Affiliation(s)
- Tsuneyuki Ubagai
- Department of Microbiology & Immunology, Teikyo University School of Medicine. Tokyo 173-8605, Japan
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Wang H, Heijnen CJ, van Velthoven CTJ, Willemen HLDM, Ishikawa Y, Zhang X, Sood AK, Vroon A, Eijkelkamp N, Kavelaars A. Balancing GRK2 and EPAC1 levels prevents and relieves chronic pain. J Clin Invest 2013; 123:5023-34. [PMID: 24231349 DOI: 10.1172/jci66241] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 09/12/2013] [Indexed: 01/12/2023] Open
Abstract
Chronic pain is a major clinical problem, yet the mechanisms underlying the transition from acute to chronic pain remain poorly understood. In mice, reduced expression of GPCR kinase 2 (GRK2) in nociceptors promotes cAMP signaling to the guanine nucleotide exchange factor EPAC1 and prolongs the PGE2-induced increase in pain sensitivity (hyperalgesia). Here we hypothesized that reduction of GRK2 or increased EPAC1 in dorsal root ganglion (DRG) neurons would promote the transition to chronic pain. We used 2 mouse models of hyperalgesic priming in which the transition from acute to chronic PGE2-induced hyperalgesia occurs. Hyperalgesic priming with carrageenan induced a sustained decrease in nociceptor GRK2, whereas priming with the PKCε agonist ΨεRACK increased DRG EPAC1. When either GRK2 was increased in vivo by viral-based gene transfer or EPAC1 was decreased in vivo, as was the case for mice heterozygous for Epac1 or mice treated with Epac1 antisense oligodeoxynucleotides, chronic PGE2-induced hyperalgesia development was prevented in the 2 priming models. Using the CFA model of chronic inflammatory pain, we found that increasing GRK2 or decreasing EPAC1 inhibited chronic hyperalgesia. Our data suggest that therapies targeted at balancing nociceptor GRK2 and EPAC1 levels have promise for the prevention and treatment of chronic pain.
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Swain JD, Fargnoli AS, Katz MG, Tomasulo CE, Sumaroka M, Richardville KC, Koch WJ, Rabinowitz JE, Bridges CR. MCARD-mediated gene transfer of GRK2 inhibitor in ovine model of acute myocardial infarction. J Cardiovasc Transl Res 2012. [PMID: 23208013 DOI: 10.1007/s12265-012-9418-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
β-Adrenergic receptor (βAR) dysfunction in acute myocardial infarction (MI) is associated with elevated levels of the G-protein-coupled receptor kinase-2 (GRK2), which plays a key role in heart failure progression. Inhibition of GRK2 via expression of a peptide βARKct transferred by molecular cardiac surgery with recirculating delivery (MCARD) may be a promising intervention. Five sheep underwent scAAV6-mediated MCARD delivery of βARKct, and five received no treatment (control). After a 3-week period, the branch of the circumflex artery (OM1) was ligated. Quantitative PCR data showed intense βARKct expression in the left ventricle (LV). Circumferential fractional shortening was 23.4 ± 7.1 % (baseline) vs. -2.9 ± 5.2 % (p < 0.05) in the control at 10 weeks. In the MCARD-βARKct group, this parameter was close to baseline. The same trend was observed with LV wall thickening. Cardiac index fully recovered in the MCARD-βARKct group. LV end-diastolic volume and LV end-diastolic pressure did not differ in both groups. MCARD-mediated βARKct gene expression results in preservation of regional and global systolic function after acute MI without arresting progressive ventricular remodeling.
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Affiliation(s)
- JaBaris D Swain
- Department of Surgery, Division of Cardiovascular Surgery, University of Pennsylvania Medical Center, Philadelphia, PA, USA
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Leoratti FMDS, Trevelin SC, Cunha FQ, Rocha BC, Costa PAC, Gravina HD, Tada MS, Pereira DB, Golenbock DT, do Valle Antonelli LR, Gazzinelli RT. Neutrophil paralysis in Plasmodium vivax malaria. PLoS Negl Trop Dis 2012; 6:e1710. [PMID: 22745844 PMCID: PMC3383745 DOI: 10.1371/journal.pntd.0001710] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 05/13/2012] [Indexed: 12/03/2022] Open
Abstract
Background The activation of innate immune responses by Plasmodium vivax results in activation of effector cells and an excessive production of pro-inflammatory cytokines that may culminate in deleterious effects. Here, we examined the activation and function of neutrophils during acute episodes of malaria. Materials and Methods Blood samples were collected from P. vivax-infected patients at admission (day 0) and 30–45 days after treatment with chloroquine and primaquine. Expression of activation markers and cytokine levels produced by highly purified monocytes and neutrophils were measured by the Cytometric Bead Assay. Phagocytic activity, superoxide production, chemotaxis and the presence of G protein-coupled receptor (GRK2) were also evaluated in neutrophils from malaria patients. Principal Findings Both monocytes and neutrophils from P. vivax-infected patients were highly activated. While monocytes were found to be the main source of cytokines in response to TLR ligands, neutrophils showed enhanced phagocytic activity and superoxide production. Interestingly, neutrophils from the malaria patients expressed high levels of GRK2, low levels of CXCR2, and displayed impaired chemotaxis towards IL-8 (CXCL8). Conclusion Activated neutrophils from malaria patients are a poor source of pro-inflammatory cytokines and display reduced chemotactic activity, suggesting a possible mechanism for an enhanced susceptibility to secondary bacterial infection during malaria. Plasmodium vivax is responsible for approximately 60–80% of the malaria cases in the world, and contributes to significant social and economic instability in the developing countries of Latin America and Asia. The pathogenesis of P. vivax malaria is a consequence of host derived inflammatory mediators. Hence, a better understanding of the mechanisms involved in induction of systemic inflammation during P. vivax malaria is critical for the clinical management and prevention of severe disease. The innate immune receptors recognize Plasmodium sp. and initiate a broad spectrum of host defense mechanisms that mediate resistance to infection. However, the innate immune response is the classic “two-edged sword”, and clinical malaria is associated with high levels of circulating pro-inflammatory cytokines. Our findings show that both monocytes and neutrophils are highly activated during malaria. Monocytes produced high levels of IL-1β, IL-6 and TNF-α during acute malaria. On the other hand, neutrophils were a poor source of cytokines, but displayed an enhanced phagocytic activity and superoxide production. Unexpectedly, we noticed an impaired chemotaxis of neutrophils towards an IL-8 (CXCL8) gradient. We proposed that neutrophil paralysis is in part responsible for the enhanced susceptibility to bacterial infection observed in malaria patients.
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Affiliation(s)
| | - Silvia Cellone Trevelin
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Fernando Queiroz Cunha
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Bruno Coelho Rocha
- Laboratório de Imunopatologia, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Pedro Augusto Carvalho Costa
- Laboratório de Imunopatologia, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil
| | - Humberto Doriguêtto Gravina
- Laboratório de Imunopatologia, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Mauro Shugiro Tada
- Centro de Pesquisas em Medicina Tropical de Rondônia, Porto Velho, Rondônia, Brazil
| | | | - Douglas Taylor Golenbock
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Lis Ribeiro do Valle Antonelli
- Laboratório de Imunopatologia, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil
| | - Ricardo T. Gazzinelli
- Laboratório de Imunopatologia, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil
- Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail:
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Soltysinska E, Thiele S, Olesen SP, Osadchii OE. Chronic sympathetic activation promotes downregulation of β-adrenoceptor-mediated effects in the guinea pig heart independently of structural remodeling and systolic dysfunction. Pflugers Arch 2011; 462:529-43. [PMID: 21811789 DOI: 10.1007/s00424-011-1005-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 07/25/2011] [Accepted: 07/25/2011] [Indexed: 11/26/2022]
Abstract
It is uncertain if downregulation of β-adrenoceptor signaling pathway is promoted by an enhanced adrenergic tone at an early stage of cardiac disease, or it develops secondary to detrimental local myocardial changes in advanced heart failure. We examined the integrity of β-adrenoceptor signaling pathway upon chronic infusion of isoproterenol, a β-adrenoceptor agonist, at a dose producing no structural left ventricular (LV) remodeling and systolic dysfunction. Subcutaneous isoproterenol infusion (400 μg kg(-1) h(-1) over 16 days) to guinea pigs using osmotic minipumps produced no change in cardiac weights, LV internal dimensions, myocyte cross-sectional area, extent of interstitial fibrosis, and basal contractile function. Isolated, perfused heart preparations from isoproterenol-treated guinea pigs exhibited attenuated responsiveness to acute β-adrenoceptor stimulation, as evidenced by reduced LV developed pressure increase, less shortening of LV epicardial monophasic action potential and effective refractory period, and less myocardial cyclic adenosine monophosphate elevation, in response to isoproterenol exposure, when compared to saline-treated controls. Pharmacological responses to forskolin, an activator of the adenylate cyclase catalytic subunit, were well preserved in isoproterenol-treated hearts. Downregulation of β-adrenoceptor-mediated effects upon chronic isoproterenol infusion was associated with markedly reduced stimulatory G-protein α-subunit (G(sα)) myocardial expression levels. No change in expression levels of β-adrenoceptors, G-protein-coupled receptor kinase 2, inhibitory G-protein α-subunit (G(iα2)), and Ca(v)1.2 and K(v)7.1 ion channels was determined in isoproterenol-treated hearts. We therefore conclude that sustained adrenergic overstimulation may promote downregulation of myocardial β-adrenoceptor-mediated effects independently of structural LV remodeling and systolic failure, an effect attributed to β-adrenoceptor uncoupling from adenylate cyclase due to reduced G(sα)-protein expression.
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Affiliation(s)
- Ewa Soltysinska
- The Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen N, Denmark
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