scholarly journals Rho Family GTPases Are Required for Activation of Jak/STAT Signaling by G Protein-Coupled Receptors

2003 ◽  
Vol 23 (4) ◽  
pp. 1316-1333 ◽  
Author(s):  
Stéphane Pelletier ◽  
François Duhamel ◽  
Philippe Coulombe ◽  
Michel R. Popoff ◽  
Sylvain Meloche
Keyword(s):  
Tyrosine Phosphorylation ◽  
G Protein ◽  
Tyrosine Kinases ◽  
Rho Gtpases ◽  
G Protein Coupled Receptors ◽  
Dependent Manner ◽  
Signal Transducers ◽  
Regulatory Effects ◽  
Rapid Activation ◽  
G Protein Coupled

ABSTRACT As do cytokine receptors and receptor tyrosine kinases, G protein-coupled receptors (GPCRs) signal to Janus kinases (Jaks) and signal transducers and activators of transcription (STATs). However, the early biochemical events linking GPCRs to this signaling pathway have been unclear. Here we show that GPCR-stimulated Rac activity and the subsequent generation of reactive oxygen species are necessary for activating tyrosine phosphorylation of Jaks and STAT-dependent transcription. The requirement for Rac activity can be overcome by addition of hydrogen peroxide. Expression of activated mutants of Rac1 is sufficient to activate Jak2 and STAT-dependent transcription, and the activation of Jak2 correlates with the ability of Rac1 to bind to NADPH oxidase subunit p67phox. We further show that GPCR agonists stimulate tyrosine phosphorylation of STAT1 and STAT3 proteins in a Rac-dependent manner. The tyrosine phosphorylation of STAT3 is biphasic; the first peak of phosphorylation is weak and correlates with rapid activation of Jaks by GPCRs, whereas the second peak is stronger and requires the synthesis of an autocrine factor. Rho also plays an essential role in the induction of STAT transcriptional activity. Our results highlight a novel role for Rho GTPases in mediating the regulatory effects of GPCRs on STAT-dependent gene expression.

scholarly journals G-protein–coupled formyl peptide receptors play a dual role in neutrophil chemotaxis and bacterial phagocytosis

2019 ◽  
Vol 30 (3) ◽  
pp. 346-356 ◽  
Author(s):  
Xi Wen ◽  
Xuehua Xu ◽  
Wenxiang Sun ◽  
Keqiang Chen ◽  
Miao Pan ◽  
...  
Keyword(s):  
G Protein ◽  
Receptor Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Actin Polymerization ◽  
G Protein Coupled Receptors ◽  
Peptide Receptors ◽  
Tyrosine Kinase Signaling ◽  
Formyl Peptide Receptors ◽  
Formyl Peptide ◽  
G Protein Coupled

A dogma of innate immunity is that neutrophils use G-protein–coupled receptors (GPCRs) for chemoattractant to chase bacteria through chemotaxis and then use phagocytic receptors coupled with tyrosine kinases to destroy opsonized bacteria via phagocytosis. Our current work showed that G-protein–coupled formyl peptide receptors (FPRs) directly mediate neutrophil phagocytosis. Mouse neutrophils lacking formyl peptide receptors (Fpr1/2–/–) are defective in the phagocytosis of Escherichia coli and the chemoattractant N-formyl-Met-Leu-Phe (fMLP)-coated beads. fMLP immobilized onto the surface of a bead interacts with FPRs, which trigger a Ca2+response and induce actin polymerization to form a phagocytic cup for engulfment of the bead. This chemoattractant GPCR/Gi signaling works independently of phagocytic receptor/tyrosine kinase signaling to promote phagocytosis. Thus, in addition to phagocytic receptor-mediated phagocytosis, neutrophils also utilize the chemoattractant GPCR/Gi signaling to mediate phagocytosis to fight against invading bacteria.

scholarly journals Ligand bias in receptor tyrosine kinase signaling

2020 ◽  
Vol 295 (52) ◽  
pp. 18494-18507
Author(s):  
Kelly Karl ◽  
Michael D. Paul ◽  
Elena B. Pasquale ◽  
Kalina Hristova
Keyword(s):  
G Protein ◽  
Receptor Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Receptor Tyrosine Kinases ◽  
G Protein Coupled Receptors ◽  
Operational Model ◽  
Tyrosine Kinase Signaling ◽  
Rtk Signaling ◽  
Ligand Bias ◽  
G Protein Coupled

Ligand bias is the ability of ligands to differentially activate certain receptor signaling responses compared with others. It reflects differences in the responses of a receptor to specific ligands and has implications for the development of highly specific therapeutics. Whereas ligand bias has been studied primarily for G protein–coupled receptors (GPCRs), there are also reports of ligand bias for receptor tyrosine kinases (RTKs). However, the understanding of RTK ligand bias is lagging behind the knowledge of GPCR ligand bias. In this review, we highlight how protocols that were developed to study GPCR signaling can be used to identify and quantify RTK ligand bias. We also introduce an operational model that can provide insights into the biophysical basis of RTK activation and ligand bias. Finally, we discuss possible mechanisms underpinning RTK ligand bias. Thus, this review serves as a primer for researchers interested in investigating ligand bias in RTK signaling.

Arrestin-2 Regulates Akt Activation by G Protein-Coupled Receptors in Platelets.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1525-1525
Author(s):  
Dongjun Li ◽  
Donna S. Woulfe
Keyword(s):  
G Protein ◽  
Genetic Manipulation ◽  
Embryonic Stem ◽  
Phosphatidyl Inositol ◽  
G Protein Coupled Receptors ◽  
Resting Cells ◽  
Dependent Manner ◽  
Akt Phosphorylation ◽  
Receptor Sites ◽  
G Protein Coupled

Abstract Arrestins have been shown to play important roles in G Protein-Coupled Receptor (GPCR) function in many cells, but their roles in platelets remain uncharacterized. While the classical role of arrestins is considered to be the internalization and desensitization of GPCRs, more recent studies suggest that arrestins can serve as scaffolds to recruit phosphatidyl inositol-3 kinases (PI3K)s to Gq-coupled receptors and promote PI3K-dependent signaling. Thrombin stimulates the PI3K-dependent activation of Akt in platelets in a Gq-dependent manner. Therefore, we sought to determine whether arrestins are involved in the PI3K-dependent activation of Akt in platelets. Comparative immunoblots show that of the two non-visual mammalian arrestins, only one, arrestin-2 (β-arrestin-1), is expressed in human and mouse platelets. Immunoprecipitation of arrestin-2 or p85-PI3K from platelet lysates demonstrated that arrestin-2 associates with the p85 subunit of PI3Ka/b in thrombin or ADP-stimulated platelets, but not resting cells. The association can be inhibited by inhibitors of the P2Y12 receptor for ADP, but not by P2Y1 inhibitors. p85-arrestin association is also blocked by inhibitors of src family kinases, as is Akt phosphorylation. To determine whether src family members were part of the p85-arrestin complexes, immunoblots were re-probed with antibodies to src, lyn and fyn. The results show that Lyn is incorporated into thrombin-stimulated arrestin complexes in a P2Y12-dependent manner. To determine whether arrestin-2 is important for Akt phosphorylation in platelets, megakaryocytes differentiated in culture from mouse embryonic stem cells were used as models of platelet signaling, since these cells are amenable to genetic manipulation. Arrestin-2 was inhibited in the cultured megakaryocytes using a siRNA approach, then cells were stimulated with thrombin and Akt phosphorylation was assessed by immunoblotting. Arrestin-2 expression in the cultured megakaryocytes treated with arrestin-2 specific siRNA was suppressed by an average of 53% compared to cells treated with scrambled siRNA, while thrombin-stimulated Akt phosphorylation was suppressed by 98% compared to scrambled siRNA-treated control cells (n=3 experiments, difference is significant, p=.01, unpaired student’s t-test). In conclusion, the results show that arrestin-2, lyn and PI3Kform a tri-molecular complex following stimulation of platelets with ADP or thrombin. Formation of arrestin complexes at activated receptor sites is important for the localized recruitment and src-dependent activation of p85-PI3K, thus promoting activation of Akt by G protein-coupled receptors.

scholarly journals 'Location, location, location': activation and targeting of MAP kinases by G protein-coupled receptors

2003 ◽  
Vol 30 (2) ◽  
pp. 117-126 ◽  
Author(s):  
LM Luttrell
Keyword(s):  
Map Kinase ◽  
G Protein ◽  
Tyrosine Kinases ◽  
Map Kinases ◽  
Focal Adhesions ◽  
G Protein Coupled Receptors ◽  
Cellular Growth ◽  
Substantial Impact ◽  
Kinase Activation ◽  
G Protein Coupled

A growing body of data supports the conclusion that G protein-coupled receptors can regulate cellular growth and differentiation by controlling the activity of MAP kinases. The activation of heterotrimeric G protein pools initiates a complex network of signals leading to MAP kinase activation that frequently involves cross-talk between G protein-coupled receptors and receptor tyrosine kinases or focal adhesions. The dominant mechanism of MAP kinase activation varies significantly between receptor and cell type. Moreover, the mechanism of MAP kinase activation has a substantial impact on MAP kinase function. Some signals lead to the targeting of activated MAP kinase to specific extranuclear locations, while others activate a MAP kinase pool that is free to translocate to the nucleus and contribute to a mitogenic response.

scholarly journals G Protein-coupled Receptors Mediate Two Functionally Distinct Pathways of Tyrosine Phosphorylation in Rat 1a Fibroblasts

1997 ◽  
Vol 272 (50) ◽  
pp. 31648-31656 ◽  
Author(s):  
Louis M. Luttrell ◽  
Yehia Daaka ◽  
Gregory J. Della Rocca ◽  
Robert J. Lefkowitz
Keyword(s):  
Tyrosine Phosphorylation ◽  
G Protein ◽  
G Protein Coupled Receptors ◽  
G Protein Coupled

scholarly journals Sphingosine 1-phosphate receptor 2 antagonist JTE-013 increases the excitability of sensory neurons independently of the receptor

2012 ◽  
Vol 108 (5) ◽  
pp. 1473-1483 ◽  
Author(s):  
Chao Li ◽  
Xian Xuan Chi ◽  
Wenrui Xie ◽  
J. A. Strong ◽  
J.-M. Zhang ◽  
...  
Keyword(s):  
G Protein ◽  
Sensory Neurons ◽  
Neuronal Excitability ◽  
Small Diameter ◽  
G Protein Coupled Receptors ◽  
Prostaglandin E ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Sphingosine 1 Phosphate ◽  
G Protein Coupled

Previously we demonstrated that sphingosine 1-phosphate receptor 1 (S1PR1) played a prominent, but not exclusive, role in enhancing the excitability of small-diameter sensory neurons, suggesting that other S1PRs can modulate neuronal excitability. To examine the potential role of S1PR2 in regulating neuronal excitability we used the established selective antagonist of S1PR2, JTE-013. Here we report that exposure to JTE-013 alone produced a significant increase in excitability in a time- and concentration-dependent manner in 70–80% of recorded neurons. Internal perfusion of sensory neurons with guanosine 5′- O-(2-thiodiphosphate) (GDP-β-S) via the recording pipette inhibited the sensitization produced by JTE-013 as well as prostaglandin E2. Pretreatment with pertussis toxin or the selective S1PR1 antagonist W146 blocked the sensitization produced by JTE-013. These results indicate that JTE-013 might act as an agonist at other G protein-coupled receptors. In neurons that were sensitized by JTE-013, single-cell RT-PCR studies demonstrated that these neurons did not express the mRNA for S1PR2. In behavioral studies, injection of JTE-013 into the rat's hindpaw produced a significant increase in the mechanical sensitivity in the ipsilateral, but not contralateral, paw. Injection of JTE-013 did not affect the withdrawal latency to thermal stimulation. Thus JTE-013 augments neuronal excitability independently of S1PR2 by unknown mechanisms that may involve activation of other G protein-coupled receptors such as S1PR1. Clearly, further studies are warranted to establish the causal nature of this increased sensitivity, and future studies of neuronal function using JTE-013 should be interpreted with caution.

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