Faculty Opinions recommendation of Site-directed mutagenesis of the Arabidopsis heterotrimeric G protein β subunit suggests divergent mechanisms of effector activation between plant and animal G proteins.

Prostanoid receptors belong to the class of heptahelical plasma membrane receptors. For the five prostanoids, eight receptor subtypes have been identified. They display an overall sequence similarity of roughly 30%. Based on sequence comparison, single amino acids in different subtypes of different species have previously been identified by site-directed mutagenesis or in hybrid receptors that appear to be essential for ligand binding or G-protein coupling. Based on this information, a series of mutants of the human FP receptor was generated and characterized in ligand-binding and second-messenger-formation studies. It was found that mutation of His-81 to Ala in transmembrane domain 2 and of Arg-291 to Leu in transmembrane domain 7, which are putative interaction partners for the prostanoid's carboxyl group, abolished ligand binding. Mutants in which Ser-263 in transmembrane domain 6 or Asp-300 in transmembrane domain 7 had been replaced by Ala or Gln, respectively, no longer discriminated between prostaglandins PGF2α and PGD2. Thus distortion of the topology of transmembrane domains 6 and 7 appears to interfere with the cyclopentane ring selectivity of the receptor. PGF2α-induced inositol formation was strongly reduced in the mutant Asp-300Gln, inferring a role for this residue in agonist-induced G-protein activation.

Download Full-text

The Arabidopsis heterotrimeric G‐protein β subunit,AGB1, is required for guard cell calcium sensing and calcium‐induced calcium release

The Plant Journal ◽

10.1111/tpj.14318 ◽

2019 ◽

Cited By ~ 1

Author(s):

Byeong Wook Jeon ◽

Biswa R. Acharya ◽

Sarah M. Assmann

Keyword(s):

G Protein ◽

Guard Cell ◽

Calcium Release ◽

Β Subunit ◽

Heterotrimeric G Protein ◽

Cell Calcium ◽

Calcium Sensing ◽

Calcium Induced Calcium Release

Download Full-text

Anesthetics Inhibit Acetylcholine-promoted Guanine Nucleotide Exchange of Heterotrimeric G Proteins of Airway Smooth Muscle

Anesthesiology ◽

10.1097/00000542-200407000-00019 ◽

2004 ◽

Vol 101 (1) ◽

pp. 120-126 ◽

Cited By ~ 2

Author(s):

Chie Sakihara ◽

William J. Perkins ◽

David O. Warner ◽

Keith A. Jones

Keyword(s):

Smooth Muscle ◽

Muscle Contraction ◽

G Protein ◽

Muscarinic Receptor ◽

G Proteins ◽

Airway Smooth Muscle ◽

Smooth Muscle Contraction ◽

Heterotrimeric G Proteins ◽

Nucleotide Exchange ◽

Heterotrimeric G Protein

Background Anesthetics inhibit airway smooth muscle contraction in part by a direct effect on the smooth muscle cell. This study tested the hypothesis that the anesthetics halothane and hexanol, which both relax airway smooth muscle in vitro, inhibit acetylcholine-promoted nucleotide exchange at the alpha subunit of the Gq/11 heterotrimeric G protein (Galphaq/11; i.e., they inhibit muscarinic receptor-Galphaq/11 coupling). Methods The effect of halothane (0.38 +/- 0.02 mm) and hexanol (10 mm) on basal and acetylcholine-stimulated Galphaq/11 guanosine nucleotide exchange was determined in membranes prepared from porcine tracheal smooth muscle. The nonhydrolyzable, radioactive form of guanosine-5'-triphosphate, [S]GTPgammaS, was used as the reporter for Galphaq/11 subunit dissociation from the membrane to soluble fraction, which was immunoprecipitated with rabbit polyclonal anti-Galphaq/11 antiserum. Results Acetylcholine caused a significant time- and concentration-dependent increase in the magnitude of Galphaq/11 nucleotide exchange compared with basal values (i.e., without acetylcholine), reaching a maximal difference at 100 microm (35.9 +/-2.9 vs. 9.8 +/-1.2 fmol/mg protein, respectively). Whereas neither anesthetic had an effect on basal Galphaq/11 nucleotide exchange, both halothane and hexanol significantly inhibited the increase in Galphaq/11 nucleotide exchange produced by 30 microm acetylcholine (by 59% and 68%, respectively). Conclusions Halothane and hexanol interact with the receptor-heterotrimeric G-protein complex in a manner that prevents acetylcholine-promoted exchange of guanosine-5(')-triphosphate for guanosine-5'-diphosphate at Galphaq/11. These data are consistent with the ability of anesthetics to interfere with cellular processes mediated by heterotrimeric G proteins in many cells, including effects on muscarinic receptor-G-protein regulation of airway smooth muscle contraction.

Download Full-text

Heterotrimeric G-Protein Signalers and RGSs in Aspergillus fumigatus

Pathogens ◽

10.3390/pathogens9110902 ◽

2020 ◽

Vol 9 (11) ◽

pp. 902

Author(s):

Hee-Soo Park ◽

Min-Ju Kim ◽

Jae-Hyuk Yu ◽

Kwang-Soo Shin

Keyword(s):

Aspergillus Fumigatus ◽

Signaling Pathways ◽

Signaling Pathway ◽

G Protein ◽

G Proteins ◽

Pathogenic Fungus ◽

G Protein Signaling ◽

Protein Signaling ◽

Heterotrimeric G Protein ◽

External Signals

The heterotrimeric G-protein (G-protein) signaling pathway is one of the most important signaling pathways that transmit external signals into the inside of the cell, triggering appropriate biological responses. The external signals are sensed by various G-protein-coupled receptors (GPCRs) and transmitted into G-proteins consisting of the α, β, and γ subunits. Regulators of G-protein signaling (RGSs) are the key controllers of G-protein signaling pathways. GPCRs, G-proteins, and RGSs are the primary upstream components of the G-protein signaling pathway, and they are highly conserved in most filamentous fungi, playing diverse roles in biological processes. Recent studies characterized the G-protein signaling components in the opportunistic pathogenic fungus Aspergillus fumigatus. In this review, we have summarized the characteristics and functions of GPCRs, G-proteins, and RGSs, and their regulatory roles in governing fungal growth, asexual development, germination, stress tolerance, and virulence in A. fumigatus.

Download Full-text