scholarly journals Biochemical and genetic analysis of dominant-negative mutations affecting a yeast G-protein gamma subunit.

1994 ◽  
Vol 14 (7) ◽  
pp. 4571-4578 ◽  
Author(s):  
A V Grishin ◽  
J L Weiner ◽  
K J Blumer
Keyword(s):  
G Protein ◽  
Dominant Negative ◽  
Beta Subunits ◽  
Yeast Saccharomyces Cerevisiae ◽  
Surface Receptors ◽  
Receptor Coupling ◽  
Gamma Subunits ◽  
Dominant Negative Mutations ◽  
Guanine Nucleotide Binding

Heterotrimeric guanine nucleotide-binding proteins (G proteins) consisting of alpha, beta, and gamma subunits mediate signalling between cell surface receptors and intracellular effectors in eukaryotic cells. To define signalling functions of G gamma subunits (STE18 gene product) involved in pheromone response and mating in the yeast Saccharomyces cerevisiae, we isolated and characterized dominant-negative STE18 alleles. We obtained dominant-negative mutations that disrupt C-terminal sequences required for prenylation of G gamma precursors (CAAX box) and that affect residues in the N-terminal half of Ste18p. Overexpression of mutant G gamma subunits in wild-type cells blocked signal transduction; this effect was suppressed upon overexpression of G beta subunits. Mutant G gamma subunits may therefore sequester G beta subunits into nonproductive G beta gamma dimers. Because mutant G gamma subunits blocked the constitutive signal resulting from disruption of the G alpha subunit gene (GPA1), they are defective in functions required for downstream signalling. Ste18p bearing a C107Y substitution in the CAAX box displayed reduced electrophoretic mobility, consistent with a prenylation defect. G gamma subunits carrying N-terminal substitutions had normal electrophoretic mobilities, suggesting that these proteins were prenylated. G gamma subunits bearing substitutions in their N-terminal region or C-terminal CAAX box (C107Y) supported receptor-G protein coupling in vitro, whereas C-terminal truncations caused partial defects in receptor coupling.

scholarly journals Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease

2016 ◽  
Vol 9 (423) ◽  
pp. ra37-ra37 ◽  
Author(s):  
Arthur Marivin ◽  
Anthony Leyme ◽  
Kshitij Parag-Sharma ◽  
Vincent DiGiacomo ◽  
Anthony Y. Cheung ◽  
...  
Keyword(s):  
G Protein ◽  
Mammalian Cells ◽  
Neural Crest Cell ◽  
Craniofacial Development ◽  
Dominant Negative ◽  
Protein Subunit ◽  
Protein Activity ◽  
Guanine Nucleotide Binding Protein ◽  
Heterotrimeric G Protein

Auriculo-condylar syndrome (ACS), a rare condition that impairs craniofacial development, is caused by mutations in a G protein–coupled receptor (GPCR) signaling pathway. In mice, disruption of signaling by the endothelin type A receptor (ETAR), which is mediated by the G protein (heterotrimeric guanine nucleotide–binding protein) subunit Gαq/11 and subsequently phospholipase C (PLC), impairs neural crest cell differentiation that is required for normal craniofacial development. Some ACS patients have mutations in GNAI3, which encodes Gαi3, but it is unknown whether this G protein has a role within the ETAR pathway. We used a Xenopus model of vertebrate development, in vitro biochemistry, and biosensors of G protein activity in mammalian cells to systematically characterize the phenotype and function of all known ACS-associated Gαi3 mutants. We found that ACS-associated mutations in GNAI3 produce dominant-negative Gαi3 mutant proteins that couple to ETAR but cannot bind and hydrolyze guanosine triphosphate, resulting in the prevention of endothelin-mediated activation of Gαq/11 and PLC. Thus, ACS is caused by functionally dominant-negative mutations in a heterotrimeric G protein subunit.

scholarly journals Arabidopsis thaliana Nudix hydrolase AtNUDT7 forms complexes with the regulatory RACK1A protein and Ggamma subunits of the signal transducing heterotrimeric G protein.

2001 ◽  
Vol 58 (4) ◽  
Author(s):  
Kamil Olejnik ◽  
Maria Bucholc ◽  
Anna Anielska-Mazur ◽  
Agata Lipko ◽  
Martyna Kujawa ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
G Protein ◽  
Cellular Response ◽  
Regulatory Protein ◽  
Bimolecular Fluorescence Complementation ◽  
Nudix Hydrolase ◽  
Heterotrimeric G Protein ◽  
Cell Extracts ◽  
Gamma Subunits

Arabidopsis thaliana AtNUDT7 Nudix pyrophosphatase hydrolyzes NADH and ADP-ribose in vitro and is an important factor in the cellular response to diverse biotic and abiotic stresses. Several studies have shown that loss-of-function Atnudt7 mutant plants display many profound phenotypes. However the molecular mechanism of AtNUDT7 function remains elusive. To gain a better understanding of this hydrolase cellular role, proteins interacting with AtNUDT7 were identified. Using AtNUDT7 as a bait in an in vitro binding assay of proteins derived from cultured Arabidopsis cell extracts we identified the regulatory protein RACK1A as an AtNUDT7-interactor. RACK1A-AtNUDT7 interaction was confirmed in a yeast two-hybrid assay and in a pull-down assay and in Bimolecular Fluorescence Complementation (BiFC) analysis of the proteins transiently expressed in Arabidopsis protoplasts. However, no influence of RACK1A on AtNUDT7 hydrolase catalytic activity was observed. In vitro interaction between RACK1A and the AGG1 and AGG2 gamma subunits of the signal transducing heterotrimeric G protein was also detected and confirmed in BiFC assays. Moreover, association between AtNUDT7 and both AGG1 and AGG2 subunits was observed in Arabidopsis protoplasts, although binding of these proteins could not be detected in vitro. Based on the observed interactions we conclude that the AtNUDT7 Nudix hydrolase forms complexes in vitro and in vivo with regulatory proteins involved in signal transduction. Moreover, we provide the initial evidence that both signal transducing gamma subunits bind the regulatory RACK1A protein.

scholarly journals Control of adaptation to mating pheromone by G protein beta subunits of Saccharomyces cerevisiae.

Genetics ◽  
1994 ◽  
Vol 138 (4) ◽  
pp. 1081-1092 ◽  
Author(s):  
A V Grishin ◽  
J L Weiner ◽  
K J Blumer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
G Protein ◽  
Beta Subunit ◽  
Beta Subunits ◽  
G1 Arrest ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Repeat Units ◽  
Response And Recovery ◽  
In Cis

Abstract The STE4 gene of the yeast Saccharomyces cerevisiae encodes the beta subunit of a heterotrimeric G protein that mediates response to mating pheromones and influences recovery from pheromone-induced growth arrest. To explore how G beta subunits regulate response and recovery (adaptation), we isolated and characterized signaling-defective STE4 alleles (STE4sd). STE4sd mutations resulted in amino acid substitutions in the N-terminal region of Ste4p, proximal to the first of seven repeat units conserved in G protein beta subunits. Genetic tests indicated that STE4sd mutations disrupted functions of Ste4p required for inducing pheromone responses. Wild-type cells that overexpressed STE4sd alleles displayed apparently normal initial responses to pheromone as judged by quantitative mating, G1 arrest and transcriptional assays. However, after undergoing initial G1 arrest, wild-type cells overexpressing STE4sd alleles recovered more quickly from division arrest, suggestive of a hyperadaptive phenotype. Because hyperadaptation occurred when STE4sd alleles were overexpressed in cells lacking Sst1p (Bar1p), Sst2p or the C-terminal domain of the alpha-factor receptor, this phenotype did not involve three principal modes of adaptation in yeast. However, hyperadaptation was abolished when STE4sd mutations were combined in cis with a deletion that removes a segment of Ste4p (residues 310-346) previously implicated in adaptation to pheromone. These results indicate that G beta subunits possess two independent activities, one required for triggering pheromone response and another that promotes adaptation. Potential models for G beta subunit-mediated adaptation are discussed.

scholarly journals G-Protein–Coupled Receptors in Heart Disease

2018 ◽  
Vol 123 (6) ◽  
pp. 716-735 ◽  
Author(s):  
Jialu Wang ◽  
Clarice Gareri ◽  
Howard A. Rockman
Keyword(s):  
G Protein ◽  
Physiological Role ◽  
Guanine Nucleotide Binding Protein ◽  
Surface Receptors ◽  
Downstream Signaling ◽  
Gpcr Activation ◽  
Wide Range ◽  
Health And Disease ◽  
Artery Disease ◽  
Guanine Nucleotide Binding

GPCRs (G-protein [guanine nucleotide-binding protein]–coupled receptors) play a central physiological role in the regulation of cardiac function in both health and disease and thus represent one of the largest class of surface receptors targeted by drugs. Several antagonists of GPCRs, such as βARs (β-adrenergic receptors) and Ang II (angiotensin II) receptors, are now considered standard of therapy for a wide range of cardiovascular disease, such as hypertension, coronary artery disease, and heart failure. Although the mechanism of action for GPCRs was thought to be largely worked out in the 80s and 90s, recent discoveries have brought to the fore new and previously unappreciated mechanisms for GPCR activation and subsequent downstream signaling. In this review, we focus on GPCRs most relevant to the cardiovascular system and discuss traditional components of GPCR signaling and highlight evolving concepts in the field, such as ligand bias, β-arrestin–mediated signaling, and conformational heterogeneity.

scholarly journals Monoclonal antibodies specific for globin chains

Blood ◽  
1983 ◽  
Vol 61 (3) ◽  
pp. 530-539 ◽  
Author(s):  
G Stamatoyannopoulos ◽  
M Farquhar ◽  
D Lindsley ◽  
M Brice ◽  
T Papayannopoulou ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Fetal Hemoglobin ◽  
Beta Subunits ◽  
Gamma Chain ◽  
Globin Chains ◽  
Gamma Subunits ◽  
Species Specific ◽  
Specific Reactions

Abstract Six monoclonal antibodies specific for human globin chains are described. They are produced by stable clones obtained by raising hybridomas using cells of mice immunized with either adult or fetal hemoglobin. Characterization of the antibodies included testing against tetrameric human and other animal hemoglobins, isolated hemoglobin chains, and when indicated, cyanogen bromide fragments. Monoclonals 16- 2 and 37–8 are beta-chain specific. Antibody 31–2 recognizes an antigenic determinant common to the alpha and beta subunits. Monoclonal 30–3 recognizes determinants best expressed in the alpha 2 beta 2 tetramer. Antibody 45–1 recognizes a determinant common to beta and gamma subunits, while antibody 51–7 is gamma-chain specific. None of the monoclonal antibodies recognizes mouse hemoglobin, and they display significant differences in binding to hemoglobins of various species. The species-specific reactions and the knowledge of the primary structures of globins allowed deductions about the antigenic sites recognized by two of the monoclonals (16–2 and 45–1). These antihemoglobin monoclonal antibodies will provide useful probes for studying hemoglobin expression in vivo and in vitro.

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