Membrane organization in G‐protein mechanisms

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154346/1/fsb2008012006.pd

G protein-coupled estrogen receptor (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The G protein-coupled estrogen receptor (GPER, nomenclature as agreed by the NC-IUPHAR Subcommittee on the G protein-coupled estrogen receptor [24]) was identified following observations of estrogen-evoked cyclic AMP signalling in breast cancer cells [2], which mirrored the differential expression of an orphan 7-transmembrane receptor GPR30 [5]. There are observations of both cell-surface and intracellular expression of the GPER receptor [27, 32]. Selective agonist/ antagonists for GPER have been characterized [24]. Antagonists of the nuclear estrogen receptor, such as fulvestrant [10], tamoxifen [27, 32] and raloxifene [23], as well as the flavonoid 'phytoestrogens' genistein and quercetin [16], are agonists of GPER. A complete review of GPER pharmacology has been recently published [24]. The roles of GPER in physiological systems throughout the body (cardiovascular, metabolic, endocrine, immune, reproductive) and in cancer have also been reviewed [24, 25, 18, 15, 8]

G protein-coupled estrogen receptor in GtoPdb v.2021.3

The G protein-coupled estrogen receptor (GPER, nomenclature as agreed by the NC-IUPHAR Subcommittee on the G protein-coupled estrogen receptor [25]) was identified following observations of estrogen-evoked cyclic AMP signalling in breast cancer cells [2], which mirrored the differential expression of an orphan 7-transmembrane receptor GPR30 [6]. There are observations of both cell-surface and intracellular expression of the GPER receptor [28, 33]. Selective agonist/ antagonists for GPER have been characterized [25]. Antagonists of the nuclear estrogen receptor, such as fulvestrant [11], tamoxifen [28, 33] and raloxifene [24], as well as the flavonoid 'phytoestrogens' genistein and quercetin [17], are agonists of GPER. A complete review of GPER pharmacology has been published [25]. The roles of GPER in physiological systems throughout the body (cardiovascular, metabolic, endocrine, immune, reproductive) and in cancer have also been reviewed [25, 26, 19, 16, 9]. The GPER-selective agonist G-1 is currently in Phase I/II clinical trials for cancer (NCT04130516)

Depicting a protein's two faces: GPCR classification by phylogenetic tree‐based HMMs

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116379/1/feb2s0014579303011128.pd

Large-scale purification of [alpha]2-adrenergic receptor-enriched membranes from human platelets. Persistent association of guanine nucleotides with nonpurified membranes

A simple large-scale purification of [alpha]2-adrenergic receptor-enriched membranes from human platelets is described. Binding of the antagonist [3H]yohimbine is enriched 3-5-fold compared to a crude membrane fraction. Binding of low concentrations of the partial agonist 3H-p-aminoclonidine is increased 15-20-fold due to a higher binding affinity for the purified membranes. A soluble inhibitor of 3H-p-aminoclonidine binding to purified membranes is found even in thrice-washed crude platelet membranes. The guanine nucleotides GDP and GTP are found to account for this inhibitory activity. Forskolin-stimulated adenylate cyclase activity is also enriched in the purified membrane fraction. Adenylate cyclase activity is inhibited by [alpha]2-agonist to a comparable extent in all membrane fractions. This membrane preparation should prove useful in studies of [alpha]2-adrenergic receptor mechanisms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26295/1/0000380.pd

Peptides as probes for G protein signal transduction

Triggered by agonist binding to cell surface receptors, the heterotrimeric G proteins dissociate into [alpha] and [beta][gamma] subunits, each activating distinct second messenger pathways. Peptides from the primary sequences of receptors, G proteins, and effectors have been used to study the molecular interactions between these proteins. Receptor-derived peptides from the second, third and fourth intracellular loops and certain naturally occurring peptides antagonize G protein interactions and can directly activate G protein. These peptides bind to G protein sites that include the N and C terminal regions of the [alpha] subunit and a yet to be identified region of the [beta] subunit. Peptides have also been useful in characterizing G protein-effector interactions. The identification of the contact sites between proteins involved in G protein signal transduction should aid in the development of non-peptide mimetic therapeutics which could specifically modify G protein-mediated cellular responses.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31230/1/0000133.pd

Diabetic neuropathy: inhibitory G protein dysfunction involves PKC-dependent phosphorylation of G oα

We examined the hypothesis that decreased inhibitory G protein function in diabetic neuropathy is associated with increased protein kinase C (PKC)-dependent phosphorylation of the G oα subunit. Streptozotocin-induced diabetic rats were studied between 4 and 8 weeks after onset of diabetes and compared with aged-matched healthy animals as controls. Opioid-mediated inhibition of forskolin-stimulated cyclic AMP was significantly less in dorsal root ganglia (DRGs) from diabetic rats compared with controls. Activation of PKC in DRGs from control rats was associated with a significant decrease in opioid-mediated inhibition of forskolin-stimulated cyclic AMP that was similar to the decrease in inhibition observed in DRGs from diabetic rats. Both basal and PKC-mediated labeling of G oα with 32 P i was significantly less in DRGs from diabetic rats, supporting increased endogenous PKC-dependent phosphorylation of G oα . Probing of immunoprecipitated G oα with an anti-phospho-serine/threonine specific antibody revealed a significant increase in baseline phosphorylation in diabetic DRGs. Activation of PKC produced a significant increase in phosphorylation in control DRGs but no significant increase in G oα in diabetic DRGs. Phosphorylation of PKC-α was increased, PKC-β II was unchanged and PKC-δ decreased in diabetic DRGs. These results suggest that diminished inhibitory G protein function observed in DRGs neurons from diabetic rats involves an isoform-specific PKC-dependent pathway.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66385/1/j.1471-4159.2003.01912.x.pd

Sensitization of human α 1 ‐ and α 2 ‐adrenergic venous responses by guanadrel sulfate

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109986/1/cptclpt1990190.pd

Conditional disruption of interactions between Gαi2 and regulator of G protein signaling (RGS) proteins protects the heart from ischemic injury

Abstract Background Regulator of G protein signaling (RGS) proteins suppress G protein coupled receptor signaling by catalyzing the hydrolysis of Gα-bound guanine nucleotide triphosphate. Transgenic mice in which RGS-mediated regulation of Gαi2 is lost (RGS insensitive Gαi2 G184S) exhibit beneficial (protection against ischemic injury) and detrimental (enhanced fibrosis) cardiac phenotypes. This mouse model has revealed the physiological significance of RGS/Gαi2 interactions. Previous studies of the Gαi2 G184S mutation used mice that express this mutant protein throughout their lives. Thus, it is unclear whether these phenotypes result from chronic or acute Gαi2 G184S expression. We addressed this issue by developing mice that conditionally express Gαi2 G184S. Methods Mice that conditionally express RGS insensitive Gαi2 G184S were generated using a floxed minigene strategy. Conditional expression of Gαi2 G184S was characterized by reverse transcription polymerase chain reaction and by enhancement of agonist-induced inhibition of cAMP production in isolated cardiac fibroblasts. The impact of conditional RGS insensitive Gαi2 G184S expression on ischemic injury was assessed by measuring contractile recovery and infarct sizes in isolated hearts subjected to 30 min ischemia and 2 hours reperfusion. Results We demonstrate tamoxifen-dependent expression of Gαi2 G184S, enhanced inhibition of cAMP production, and cardioprotection from ischemic injury in hearts conditionally expressing Gαi2 G184S. Thus the cardioprotective phenotype previously reported in mice expressing Gαi2 G184S does not require embryonic or chronic Gαi2 G184S expression. Rather, cardioprotection occurs following acute (days rather than months) expression of Gαi2 G184S. Conclusions These data suggest that RGS proteins might provide new therapeutic targets to protect the heart from ischemic injury. We anticipate that this model will be valuable for understanding the time course (chronic versus acute) and mechanisms of other phenotypic changes that occur following disruption of interactions between Gαi2 and RGS proteins.http://deepblue.lib.umich.edu/bitstream/2027.42/109553/1/40360_2014_Article_315.pd

Receptor-selective Effects of Endogenous RGS3 and RGS5 to Regulate Mitogen-activated Protein Kinase Activation in Rat Vascular Smooth Muscle Cells

Regulators of G protein signaling (RGS) proteins compose a highly diverse protein family best known for inhibition of G protein signaling by enhancing GTP hydrolysis by Galpha subunits. Little is known about the function of endogenous RGS proteins. In this study, we used synthetic ribozymes targeted to RGS2, RGS3, RGS5, and RGS7 to assess their function. After demonstrating the specificity of in vitro cleavage by the RGS ribozymes, rat aorta smooth muscle cells were used for transient transfection with the RGS-specific ribozymes. RGS3 and RGS5 ribozymes differentially enhanced carbachol- and angiotensin II-induced MAP kinase activity, respectively, whereas RGS2 and RGS7 ribozymes had no effect. This enhancement was pertussis toxin-insensitive. Thus RGS3 is a negative modulator of muscarinic m3 receptor signaling, and RGS5 is a negative modulator of angiotensin AT1a receptor signaling through G(q/11). Also, RGS5 ribozyme enhanced angiotensin-stimulated inositol phosphate release. These results indicate the feasibility of using the ribozyme technology to determine the functional role of endogenous RGS proteins in signaling pathways and to define novel receptor-selective roles of endogenous RGS3 and RGS5 in modulating MAP kinase responses to either carbachol or angiotensin