title: Gβγ-independent recruitment of G-protein coupled receptor kinase 2 drives tumor necrosis factor α-induced cardiac β-adrenergic receptor dysfunction.
abstract: BACKGROUND
  Proinflammatory cytokine tumor necrosis factor-α (TNFα) induces β-adrenergic receptor (βAR) desensitization, but mechanisms proximal to the receptor in contributing to cardiac dysfunction are not known.
  
  
  RESULTS
  Two different proinflammatory transgenic mouse models with cardiac overexpression of myotrophin (a prohypertrophic molecule) or TNFα showed that TNFα alone is sufficient to mediate βAR desensitization as measured by cardiac adenylyl cyclase activity. M-mode echocardiography in these mouse models showed cardiac dysfunction paralleling βAR desensitization independent of sympathetic overdrive. TNFα-mediated βAR desensitization that precedes cardiac dysfunction is associated with selective upregulation of G-protein coupled receptor kinase 2 (GRK2) in both mouse models. In vitro studies in β2AR-overexpressing human embryonic kidney 293 cells showed significant βAR desensitization, GRK2 upregulation, and recruitment to the βAR complex following TNFα. Interestingly, inhibition of phosphoinositide 3-kinase abolished GRK2-mediated βAR phosphorylation and GRK2 recruitment on TNFα. Furthermore, TNFα-mediated βAR phosphorylation was not blocked with βAR antagonist propranolol. Additionally, TNFα administration in transgenic mice with cardiac overexpression of Gβγ-sequestering peptide βARK-ct could not prevent βAR desensitization or cardiac dysfunction showing that GRK2 recruitment to the βAR is Gβγ independent. Small interfering RNA knockdown of GRK2 resulted in the loss of TNFα-mediated βAR phosphorylation. Consistently, cardiomyocytes from mice with cardiac-specific GRK2 ablation normalized the TNFα-mediated loss in contractility, showing that TNFα-induced βAR desensitization is GRK2 dependent.
  
  
  CONCLUSIONS
  TNFα-induced βAR desensitization is mediated by GRK2 and is independent of Gβγ, uncovering a hitherto unknown cross-talk between TNFα and βAR function, providing the underpinnings of inflammation-mediated cardiac dysfunction.
authors.affiliation: Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA.
authors.forename: Neelakantan T
authors.initials: NT
authors.lastname: Vasudevan
authors.forename: Maradumane L
authors.initials: ML
authors.lastname: Mohan
authors.forename: Manveen K
authors.initials: MK
authors.lastname: Gupta
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Martelli
authors.forename: Afshan K
authors.initials: AK
authors.lastname: Hussain
authors.forename: Yilu
authors.initials: Y
authors.lastname: Qin
authors.forename: Unni M
authors.initials: UM
authors.lastname: Chandrasekharan
authors.forename: David
authors.initials: D
authors.lastname: Young
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Feldman
authors.forename: Subha
authors.initials: S
authors.lastname: Sen
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Dorn
authors.forename: Paul E
authors.initials: PE
authors.lastname: Dicorleto
authors.forename: Sathyamangla V
authors.initials: SV
authors.lastname: Naga Prasad
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004195:Disease Models, Animal; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000378:metabolism*; D057809:HEK293 Cells; D006333:Heart Failure / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009200:Myocardial Contraction / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
chemical_list: D000319:Adrenergic beta-Antagonists; D054769:G-Protein-Coupled Receptor Kinase 2; D036341:Intercellular Signaling Peptides and Proteins; D019869:Phosphatidylinositol 3-Kinases; D011433:Propranolol; D011943:Receptors, Adrenergic, beta; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; C065700:myotrophin; C496568:GRK2 protein, mouse
keywords: G-protein coupled receptor kinase 2; heart failure; inflammation; phosphoinositide 3-kinase; tumor necrosis factor-α; tumor necrosis factor-α receptor 2; β-adrenergic receptor