2P270 Structural analysis of coupling element between β2 adrenergic receptor and G-protein(22A. Bioinformatics: Structural genomics,Poster)

G protein-coupled receptors are the most pervasive signaling superfamily in the body and act as receptors to endogenous agonists and drugs. For β-agonist-mediated bronchodilation, the receptor-G protein-effector network consists of the β2-adrenergic receptor (β2AR), Gs, and adenylyl cyclase, expressed on airway smooth muscle (ASM). Using ASM-targeted transgenesis, we previously explored which of these three early signaling elements represents a limiting factor, or bottleneck, in transmission of the signal from agonist binding to ASM relaxation. Here we overexpressed Gαs in transgenic mice and found that agonist-promoted relaxation of airways was enhanced in direct proportion to the level of Gαs expression. Contraction of ASM from acetylcholine was not affected in Gαs transgenic mice, nor was relaxation by bitter taste receptors. Furthermore, agonist-promoted (but not basal) cAMP production in ASM cells from Gαs-transgenic mice was enhanced compared with ASM from nontransgenic littermates. Agonist-promoted inhibition of platelet-derived growth factor-stimulated ASM proliferation was also enhanced in Gαs mouse ASM. The enhanced maximal β-agonist response was of similar magnitude for relaxation, cAMP production, and growth inhibition. Taken together, it appears that a limiting factor in β-agonist responsiveness in ASM is the expression level of Gαs. Gene therapy or pharmacological means of increasing Gαs (or its coupling efficiency to β2AR) thus represent an interface for development of novel therapeutic agents for improvement of β-agonist therapy.

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Porcine hepatic response to sepsis and its amplification by an adrenergic receptor α1 agonist and a β2 antagonist

Clinical Science ◽

10.1042/cs0950467 ◽

1998 ◽

Vol 95 (4) ◽

pp. 467-478 ◽

Cited By ~ 2

Author(s):

D. TIGHE ◽

R. MOSS ◽

D. BENNETT

Keyword(s):

Inflammatory Response ◽

G Protein ◽

Protein Complex ◽

Adrenergic Receptor ◽

Receptor Agonist ◽

Cell Surface Receptor ◽

Ultrastructural Changes ◽

Β2 Adrenergic Receptor ◽

Adrenergic Receptor Agonist ◽

Septic Group

1.We investigated the effect of adrenergic receptor stimulation or inhibition on the hepatic ultrastructural changes in a porcine faecal peritonitis model of multi-organ failure. We infused either the α1 adrenergic receptor agonist methoxamine or the β2 adrenergic receptor antagonist ICI 118551 during 8 ;h of the study. 2.Anaesthetized pigs (25–30 ;kg) were divided into four non-septic groups (control, non-septic, non-septic methoxamine and non-septic ICI 118551) and three septic groups (septic, septic methoxamine and septic ICI 118551). 3.Changes in hepatic ultrastructure were measured by morphometric analysis. The septic group was significantly worse than all the non-septic groups. Septic methoxamine and septic ICI 118551 were significantly worse than the septic group. 4.Septic methoxamine and septic ICI 118551 had a significantly increased perisinusoidal space; septic methoxamine had significant hepatocyte vacuolation. 5.Hepatic ultrastructural changes were independent of hepatic blood flow. 6.Septic methoxamine had significant myocardial depression. 7.The α1 adrenergic receptor agonist methoxamine or the β2 antagonist ICI 118551 both amplified the hepatic injury normally found during sepsis in our porcine model. 8.These findings suggest that during sepsis a protective endogenous β2 adrenergic receptor-mediated anti-inflammatory response is activated via cell membrane transduction to stimulate the trimeric G-protein complex Gs and activate the second cell messenger cAMP. 9.In addition, it is likely that α1 adrenergic receptor agonists amplify the inflammatory response by stimulating the cell-surface receptor-linked trimeric G-protein complex to activate Gq and the second cell messenger phospholipase C.

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Receptor-Mediated Adenylyl Cyclase Activation Through XLαs, the Extra-Large Variant of the Stimulatory G Protein α-Subunit

Molecular Endocrinology ◽

10.1210/me.2002-0054 ◽

2002 ◽

Vol 16 (8) ◽

pp. 1912-1919 ◽

Cited By ~ 88

Author(s):

Murat Bastepe ◽

Yasemin Gunes ◽

Beatriz Perez-Villamil ◽

Joy Hunzelman ◽

Lee S. Weinstein ◽

...

Keyword(s):

Adenylyl Cyclase ◽

G Protein ◽

Adrenergic Receptor ◽

Α Subunit ◽

Exon 2 ◽

Amino Terminal ◽

Stimulatory G Protein ◽

Β2 Adrenergic Receptor ◽

Carboxyl Terminal ◽

G Protein Α Subunit

Abstract XLαs, the large variant of the stimulatory G protein α subunit (Gsα), is derived from GNAS1 through the use of an alternative first exon and promoter. Gsα and XLαs have distinct amino-terminal domains, but are identical over the carboxyl-terminal portion encoded by exons 2–13. XLαs can mimic some functions of Gsα, including βγ interaction and adenylyl cyclase stimulation. However, previous attempts to demonstrate coupling of XLαs to typically Gs-coupled receptors have not been successful. We now report the generation of murine cell lines that carry homozygous disruption of Gnas exon 2, and are therefore null for endogenous XLαs and Gsα (GnasE2−/E2−). GnasE2−/E2− cells transfected with plasmids encoding XLαs and different heptahelical receptors, including the β2-adrenergic receptor and receptors for PTH, TSH, and CRF, showed agonist-mediated cAMP accumulation that was indistinguishable from that observed with cells transiently coexpressing Gsα and these receptors. Our findings thus indicate that XLαs is capable of functionally coupling to receptors that normally act via Gsα.

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A New Approach to Docking in the β2-Adrenergic Receptor That Exploits the Domain Structure of G-Protein-Coupled Receptors

Journal of Medicinal Chemistry ◽

10.1021/jm960647n ◽

1997 ◽

Vol 40 (24) ◽

pp. 3871-3886 ◽

Cited By ~ 49

Author(s):

Paul R. Gouldson ◽

Christopher R. Snell ◽

Christopher A. Reynolds

Keyword(s):

G Protein ◽

Domain Structure ◽

Adrenergic Receptor ◽

G Protein Coupled Receptors ◽

New Approach ◽

Β2 Adrenergic Receptor ◽

G Protein Coupled

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Molecular insights into phosphorylation-induced allosteric conformational changes in β2-adrenergic receptor

10.1101/2021.10.01.462841 ◽

2021 ◽

Author(s):

Midhun K Madhu ◽

Annesha Debroy ◽

Rajesh K. Murarka

Keyword(s):

G Protein ◽

Conformational Changes ◽

Adrenergic Receptor ◽

Transmembrane Domain ◽

Conformational Transition ◽

Specific Binding ◽

Experimental Studies ◽

Residue Interaction ◽

Β2 Adrenergic Receptor ◽

Experimental Findings

The large conformational flexibility of G protein-coupled receptors (GPCRs) has been a puzzle in structural and pharmacological studies for the past few decades. Apart from structural rearrangements induced by ligands, enzymatic phosphorylations by GPCR kinases (GRKs) at the carboxy-terminal tail (C-tail) of a GPCR also makes conformational alterations to the transmembrane helices and facilitates the binding of one of its transducer proteins named β-arrestin. Phosphorylation-induced conformational transition of the receptor that causes specific binding to β-arrestin but prevents the association of other transducers such as G proteins lacks atomistic understanding and is elusive to experimental studies. Using microseconds of all-atom conventional and Gaussian accelerated molecular dynamics (GaMD) simulations, we investigate the allosteric mechanism of phosphorylation induced-conformational changes in β2-adrenergic receptor, a well-characterized GPCR model system. Free energy profiles reveal that the phosphorylated receptor samples a new conformational state in addition to the canonical active state corroborating with recent nuclear magnetic resonance experimental findings. The new state has a smaller intracellular cavity that is likely to accommodate β-arrestin better than G protein. Using contact map and inter-residue interaction energy calculations, we found the phosphorylated C-tail adheres to the cytosolic surface of the transmembrane domain of the receptor. Transfer entropy calculations show that the C-tail residues drive the correlated motions of TM residues, and the allosteric signal is relayed via several residues at the cytosolic surface. Our results also illustrate how the redistribution of inter-residue nonbonding interaction couples with the allosteric communication from the phosphorylated C-tail to the transmembrane. Atomistic insight into phosphorylation-induced β-arrestin specific conformation is therapeutically important to design drugs with higher efficacy and fewer side effects. Our results therefore open novel opportunities to fine-tune β-arrestin bias in GPCR signaling.

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