scholarly journals Metastable GPCR dimers trigger the basal signal by recruiting G-proteins

2020 ◽  
Author(s):  
Rinshi S. Kasai ◽  
Takahiro K. Fujiwara ◽  
Akihiro Kusumi
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Single Molecule ◽  
Resting State ◽  
G Protein Coupled Receptors ◽  
Β2 Adrenergic Receptor ◽  
Low Levels ◽  
Protein Recruitment ◽  
Novel Drug ◽  
G Protein Coupled

G-protein-coupled receptors (GPCRs) constitute the largest family of integral membrane proteins in the human genome and are responsible for various important signaling pathways for vision, olfaction, gustation, emotion, cell migration, etc. A distinct feature of the GPCR-family proteins is that many GPCRs, including the prototypical GPCR, β2-adrenergic receptor (β2AR), elicit low levels of basal constitutive signals without agonist stimulation, which function in normal development and various diseases1–3. However, how the basal signals are induced is hardly known. Another general distinctive feature of GPCRs is to form metastable homo-dimers, with lifetimes on the order of 0.1 s, even in the resting state. Here, our single-molecule-based quantification4 determined the dissociation constant of β2AR homo-dimers in the PM (1.6 ± 0.29 copies/μm2) and their lifetimes (83.2 ± 6.4 ms), and furthermore found that, in the resting state, trimeric G-proteins were recruited to both β2AR monomers and homo-dimers. Importantly, inverse agonists, which suppress the GPCR’s basal constitutive activity, specifically blocked the G-protein recruitment to GPCR homo-dimers, without affecting that to monomers. These results indicate that the G-proteins recruited to transient GPCR homo-dimers are responsible for inducing their basic constitutive signals. These results suggest novel drug development strategies to enhance or suppress GPCR homo-dimer formation.

scholarly journals Signaling from G Protein-coupled Receptors to ERK5/Big MAPK 1 Involves Gαqand Gα12/13Families of Heterotrimeric G Proteins

2000 ◽  
Vol 275 (28) ◽  
pp. 21730-21736 ◽  
Author(s):  
Shigetomo Fukuhara ◽  
Maria Julia Marinissen ◽  
Mario Chiariello ◽  
J. Silvio Gutkind
Keyword(s):  
G Protein ◽  
G Proteins ◽  
G Protein Coupled Receptors ◽  
Heterotrimeric G Proteins ◽  
G Protein Coupled

scholarly journals A monomeric G protein-coupled receptor isolated in a high-density lipoprotein particle efficiently activates its G protein

2007 ◽  
Vol 104 (18) ◽  
pp. 7682-7687 ◽  
Author(s):  
Matthew R. Whorton ◽  
Michael P. Bokoch ◽  
Søren G. F. Rasmussen ◽  
Bo Huang ◽  
Richard N. Zare ◽  
...  
Keyword(s):  
High Density Lipoprotein ◽  
G Protein ◽  
G Proteins ◽  
Single Molecule ◽  
Density Lipoprotein ◽  
High Density ◽  
Phospholipid Bilayer ◽  
X Ray Crystallography ◽  
Signaling Complex ◽  
G Protein Coupled

G protein-coupled receptors (GPCRs) respond to a diverse array of ligands, mediating cellular responses to hormones and neurotransmitters, as well as the senses of smell and taste. The structures of the GPCR rhodopsin and several G proteins have been determined by x-ray crystallography, yet the organization of the signaling complex between GPCRs and G proteins is poorly understood. The observations that some GPCRs are obligate heterodimers, and that many GPCRs form both homo- and heterodimers, has led to speculation that GPCR dimers may be required for efficient activation of G proteins. However, technical limitations have precluded a definitive analysis of G protein coupling to monomeric GPCRs in a biochemically defined and membrane-bound system. Here we demonstrate that a prototypical GPCR, the β2-adrenergic receptor (β2AR), can be incorporated into a reconstituted high-density lipoprotein (rHDL) phospholipid bilayer particle together with the stimulatory heterotrimeric G protein, Gs. Single-molecule fluorescence imaging and FRET analysis demonstrate that a single β2AR is incorporated per rHDL particle. The monomeric β2AR efficiently activates Gs and displays GTP-sensitive allosteric ligand-binding properties. These data suggest that a monomeric receptor in a lipid bilayer is the minimal functional unit necessary for signaling, and that the cooperativity of agonist binding is due to G protein association with a receptor monomer and not receptor oligomerization.

New thoughts on the role of the βγ subunit in G protein signal transduction

2000 ◽  
Vol 78 (5) ◽  
pp. 537-550 ◽  
Author(s):  
Barbara Vanderbeld ◽  
Gregory M Kelly
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
G Proteins ◽  
G Protein Coupled Receptors ◽  
Limited Information ◽  
Α Subunit ◽  
Downstream Effectors ◽  
Receptor Signal ◽  
G Protein Coupled

Heterotrimeric G proteins are involved in numerous biological processes, where they mediate signal transduction from agonist-bound G-protein-coupled receptors to a variety of intracellular effector molecules and ion channels. G proteins consist of two signaling moieties: a GTP-bound α subunit and a βγ heterodimer. The βγ dimer, recently credited as a significant modulator of G-protein-mediated cellular responses, is postulated to be a major determinant of signaling fidelity between G-protein-coupled receptors and downstream effectors. In this review we have focused on the role of βγ signaling and have included examples to demonstrate the heterogeneity in the heterodimer composition and its implications in signaling fidelity. We also present an overview of some of the effectors regulated by βγ and draw attention to the fact that, although G proteins and their associated receptors play an instrumental role in development, there is rather limited information on βγ signaling in embryogenesis.Key words: G protein, βγ subunit, G-protein-coupled receptor, signal transduction, adenylyl cyclase.

scholarly journals Signaling by G protein coupled receptors and G proteins: a perspective

Oncogene ◽  
2001 ◽  
Vol 20 (13) ◽  
pp. 1530-1531 ◽  
Author(s):  
N Dhanasekaran ◽  
J Silvio Gutkind
Keyword(s):  
G Protein ◽  
G Proteins ◽  
G Protein Coupled Receptors ◽  
G Protein Coupled
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