Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Binding of activation peptide from the fifth component of C (C5a) to its receptor triggers events leading to both stimulation of cellular responses and receptor desensitization in myeloid cells. However, although transmission of a signal to pertussis toxin-sensitive G proteins is a prerequisite to neutrophil activation, we show that the process of receptor phosphorylation is mainly independent from activation of this pathway. Treatment of cells with pertussis toxin did not modify the incorporation of phosphate mediated by a saturating concentration of C5a, indicating that agonist-occupied C5aR can be fully phosphorylated, presumably by a specific G protein-coupled receptor kinase, in the absence of activation of the Gi protein. Receptor phosphorylation was transient, with a half-life of 30 to 40 min, which suggested a role for protein phosphatases in the regulation of the state of phosphorylation of C5aR in dHL60 cells. Pretreatment of cells with okadaic acid, an inhibitor of protein phosphatases 1 and 2A, increased the basal phosphorylation of unoccupied receptor and extended the phosphorylation mediated by C5a binding. Okadaic acid delayed, but did not suppress, the dephosphorylation process, which suggests either the involvement of additional phosphatase(s) or the degradation of nondephosphorylated receptors in the endocytic pathway. The data strongly suggest that internalized C5aR are recycled to the plasma membrane with a time course consistent with the kinetics of dephosphorylation. Dephosphorylation of C5aR might be essential to receptor recycling and resensitization during chemotaxis.
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PMID:Phosphorylation, dephosphorylation, and recycling of the C5a receptor in differentiated HL60 cells. 770 44

While an age-associated diminution in myocardial contractile response to beta-adrenergic receptor (beta-AR) stimulation has been widely demonstrated to occur in the context of increased levels of plasma catecholamines, some critical mechanisms that govern beta-AR signaling must still be examined in aged hearts. Specifically, the contribution of beta-AR subtypes (beta1 versus beta2) to the overall reduction in contractile response with aging is unknown. Additionally, whether G protein-coupled receptor kinases (GRKs), which mediate receptor desensitization, or adenylyl cyclase inhibitory G proteins (Gi) are increased with aging has not been examined. Both these inhibitory mechanisms are upregulated in chronic heart failure, a condition also associated with diminished beta-AR responsiveness and increased circulatory catecholamines. In this study, the contractile responses to both beta1-AR and beta2-AR stimulation were examined in rat ventricular myocytes of a broad age range (2, 8, and 24 mo). A marked age-associated depression in contractile response to both beta-AR subtype stimulation was observed. This was associated with a nonselective reduction in the density of both beta-AR subtypes and a reduction in membrane adenylyl cyclase response to both beta-AR subtype agonists, NaF or forskolin. However, the age-associated diminutions in contractile responses to either beta1-AR or beta2-AR stimulation were not rescued by inhibiting Gi with pertussis toxin treatment. Further, the abundance or activity of beta-adrenergic receptor kinase, GRK5, or Gi did not significantly change with aging. Thus, we conclude that the positive inotropic effects of both beta1- and beta2-AR stimulation are markedly decreased with aging in rat ventricular myocytes and this is accompanied by decreases in both beta-AR subtype densities and a reduction in membrane adenylate cyclase activity. Neither GRKs nor Gi proteins appear to contribute to the age-associated reduction in cardiac beta-AR responsiveness.
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PMID:Age-associated reductions in cardiac beta1- and beta2-adrenergic responses without changes in inhibitory G proteins or receptor kinases. 950 68

The mu opioid receptor (MOR) has been shown to desensitize after 1 h of exposure to the opioid peptide, [D-Ala(2), N-MePhe(4), Gly-ol(5)]enkephalin (DAMGO), largely by the loss of receptors from the cell surface and receptor down-regulation. We have previously shown that the Thr(394) in the carboxyl tail is essential for agonist-induced early desensitization, presumably by serving as a primary phosphorylation site for G protein-coupled receptor kinase. Using a T394A mutant receptor, we determined that Thr(394) was also responsible for mu opioid receptor down-regulation. The T394A mutant receptor displayed 50% reduction of receptor down-regulation (14.8%) compared with wild type receptor (34%) upon 1 h of exposure to DAMGO. Agonist-induced T394A receptor down-regulation was unaffected by pertussis toxin treatment, indicating involvement of a mechanism independent of G protein function. Interestingly, pertussis toxin-insensitive T394A receptor down-regulation was completely inhibited by a tyrosine kinase inhibitor, genistein. Tyrosine kinase inhibition blocked wild type MOR down-regulation by 50%, and the genistein-resistant wild type MOR down-regulation was completely pertussis toxin-sensitive. Following DAMGO stimulation, MOR was shown to be phosphorylated at tyrosine residue(s), indicating that the receptor was a direct substrate for tyrosine kinase action. Mutagenesis of the four intracellular tyrosine residues resulted in complete inhibition of the G protein-insensitive MOR internalization. Therefore, agonist-induced MOR down-regulation appears to be mediated by two distinct cellular signal transduction pathways. One is G protein-dependent and GRK-dependent, which can be abolished by pertussis toxin treatment of wild type MOR or by mutagenesis of Thr(394). The other novel pathway is G protein-independent but tyrosine kinase-dependent, blocked by genistein treatment, and one in which Thr(394) has no regulatory role but phosphorylation of tyrosine residues appears essential.
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PMID:Agonist-induced, G protein-dependent and -independent down-regulation of the mu opioid receptor. The receptor is a direct substrate for protein-tyrosine kinase. 1048

Here we provide evidence to show that the platelet-derived growth factor beta receptor is tethered to endogenous G-protein-coupled receptor(s) in human embryonic kidney 293 cells. The tethered receptor complex provides a platform on which receptor tyrosine kinase and G-protein-coupled receptor signals can be integrated to produce more efficient stimulation of the p42/p44 mitogen-activated protein kinase pathway. This was based on several lines of evidence. First, we have shown that pertussis toxin (which uncouples G-protein-coupled receptors from inhibitory G-proteins) reduced the platelet-derived growth factor stimulation of p42/p44 mitogen-activated protein kinase. Second, transfection of cells with inhibitory G-protein alpha subunit increased the activation of p42/p44 mitogen-activated protein kinase by platelet-derived growth factor. Third, platelet-derived growth factor stimulated the tyrosine phosphorylation of the inhibitory G-protein alpha subunit, which was blocked by the platelet-derived growth factor kinase inhibitor, tyrphostin AG 1296. We have also shown that the platelet-derived growth factor beta receptor forms a tethered complex with Myc-tagged endothelial differentiation gene 1 (a G-protein-coupled receptor whose agonist is sphingosine 1-phosphate) in cells co-transfected with these receptors. This facilitates platelet-derived growth factor-stimulated tyrosine phosphorylation of the inhibitory G-protein alpha subunit and increases p42/p44 mitogen-activated protein kinase activation. In addition, we found that G-protein-coupled receptor kinase 2 and beta-arrestin I can associate with the platelet-derived growth factor beta receptor. These proteins play an important role in regulating endocytosis of G-protein-coupled receptor signal complexes, which is required for activation of p42/p44 mitogen-activated protein kinase. Thus, platelet-derived growth factor beta receptor signaling may be initiated by G-protein-coupled receptor kinase 2/beta-arrestin I that has been recruited to the platelet-derived growth factor beta receptor by its tethering to a G-protein-coupled receptor(s). These results provide a model that may account for the co-mitogenic effect of certain G-protein-coupled receptor agonists with platelet-derived growth factor on DNA synthesis.
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PMID:Tethering of the platelet-derived growth factor beta receptor to G-protein-coupled receptors. A novel platform for integrative signaling by these receptor classes in mammalian cells. 1135 79

In this study, we have shown that nerve growth factor (NGF)-dependent activation of the p42/p44 mitogen-activated protein kinase (p42/p44 MAPK) pathway in PC12 cells can be partially blocked by pertussis toxin (which inactivates the G proteins G(i/o)). This suggests that the Trk A receptor may use a G protein-coupled receptor pathway to signal to p42/p44 MAPK. This was supported by data showing that the NGF-dependent activation of p42/p44 MAPK is potentiated in cells transfected with G protein-coupled receptor kinase 2 (GRK2) or beta-arrestin I. Moreover, GRK2 is constitutively bound with the Trk A receptor, whereas NGF stimulates the pertussis toxin-sensitive binding of beta-arrestin I to the TrkA receptor-GRK2 complex. Both GRK2 and beta-arrestin I are involved in clathrin-mediated endocytic signaling to p42/p44 MAPK. Indeed, inhibitors of clathrin-mediated endocytosis (e.g., monodansylcadaverine, concanavalin A, and hyperosmolar sucrose) reduced the NGF-dependent activation of p42/p44 MAPK. Finally, we have found that the G protein-coupled receptor-dependent component regulating p42/p44 MAPK is required for NGF-induced differentiation of PC12 cells. Thus, NGF-dependent inhibition of DNA synthesis was partially blocked by PD098059 (inhibitor of MAPK kinase-1 activation) and pertussis toxin. Our findings are the first to show that the Trk A receptor uses a classic G protein-coupled receptor-signaling pathway to promote differentiation of PC12 cells.
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PMID:Nerve growth factor stimulation of p42/p44 mitogen-activated protein kinase in PC12 cells: role of G(i/o), G protein-coupled receptor kinase 2, beta-arrestin I, and endocytic processing. 1140 1

Recent evidence suggests that many signaling molecules localize in microdomains of the plasma membrane, particularly caveolae. In this study, overexpression of adenylyl cyclase was used as a functional probe of G protein-coupled receptor (GPCR) compartmentation. We found that three endogenous receptors in neonatal rat cardiomyocytes couple with different levels of efficiency to the activation of adenylyl cyclase type 6 (AC6), which localizes to caveolin-rich membrane fractions. Overexpression of AC6 enhanced the maximal cAMP response to beta(1)-adrenergic receptor (beta(1)AR)-selective activation 3.7-fold, to beta(2)AR-selective activation only 1.6-fold and to prostaglandin E(2) (PGE(2)) not at all. Therefore, the rank order of efficacy in coupling to AC6 is beta(1)AR > beta(2)AR > prostaglandin E(2) receptor (EP(2)R). beta(2)AR coupling efficiency was greater when we overexpressed the receptor or blocked its desensitization by expressing betaARKct, an inhibitor of G protein-coupled receptor kinase activation, but was not significantly greater when cells were treated with pertussis toxin. Assessment of receptor and AC expression indicated co-localization of AC5/6, beta(1)AR, and beta(2)AR, but not EP(2)R, in caveolin-rich membranes and caveolin-3 immunoprecipitates, likely explaining the observed activation of AC6 by betaAR subtypes but lack thereof by PGE(2). When cardiomyocytes were stimulated with a betaAR agonist, beta(2)AR were no longer found in caveolin-3 immunoprecipitates; an effect that was blocked by expression of betaARKct. Thus, agonist-induced translocation of beta(2)AR out of caveolae causes a sequestration of receptor from effector and likely contributes to the lower efficacy of beta(2)AR coupling to AC6 as compared with beta(1)AR, which do not similarly translocate. Therefore, spatial co-localization is a key determinant of efficiency of coupling by particular extracellular signals to activation of GPCR-linked effectors.
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PMID:Receptor number and caveolar co-localization determine receptor coupling efficiency to adenylyl cyclase. 1153 56

Lysophosphatidic acid (LPA) is a naturally occurring phospholipid that activates a variety of biological activities including cell proliferation. Three mammalian LPA receptor (LPAr) subtypes have been identified by molecular cloning, named lp(A1), lp(A2) and lp(A3), that are coupled to heterotrimeric G-proteins for signal transduction. The LPAr are endogenously expressed in the rat thyroid cell line FRTL-5 and we used the FRTL-5 cells permanently transfected to obtain moderate overexpression of G-protein-coupled receptor kinase-2 (GRK2) or beta-arrestin1 to study whether GRK2 and beta-arrestin1 desensitise LPAr-mediated signalling and regulate LPA-stimulated functional effects. Using RT-PCR we documented that lp(A1), lp(A2) and lp(A3) receptors are all expressed in FRTL-5 cells. We then analysed the signal transduction of the LPAr in FRTL-5 cells. Exposure to LPA did not stimulate inositol phosphate formation nor cAMP accumulation but reduced forskolin-stimulated cAMP. LPA was also able to stimulate MAP kinase activation and this effect was abolished by pertussis toxin pretreatment. These results suggest that LPAr are mainly coupled to a pertussis toxin-sensitive G-protein in FRTL-5 cells. In order to investigate whether GRKs and arrestins are involved in the regulation of LPAr-mediated signalling, we used the FRTL-5 cell line permanently transfected to overexpress GRK2 (named L5GRK2 cells) or beta-arrestin1 (L5betaarr1 cells). The ability of LPA to inhibit forskolin-stimulated cAMP accumulation was blunted in L5GRK2 and more markedly in L5betaarr1. The MAP kinase activation was also blunted in L5GRK2 and in L5betaarr1B cells. Exposure to 20 microM LPA increased the phosphorylation of extracellular signal-regulated kinases ERK1/2 by approximately 3-fold in L5pBJI cells (FRTL-5 cells transfected with the empty vector pBJI) while it induced a modest increase in L5betaarr1 and was ineffective in L5GRK2. We measured [3H]thymidine uptake in L5betaarr1B and in L5 GRK2 cells to test whether GRK2 and beta-arrestin1 could have a role in the regulation of LPAr-mediated cell proliferation. The mitogenic response induced by 35 microM LPA was substantially blunted in L5betaarr1 (-69+/-6%) and in L5GRK2 (-69.8+/-4.5%) cells as compared with L5pBJI. Our findings document that the receptor-mediated responses elicited by LPA are regulated by GRK2 and beta-arrestin1 in FRTL-5 cells and indicate that this mechanism is potentially important for the control of the LPA-stimulated proliferative response.
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PMID:Regulation of lysophosphatidic acid receptor-stimulated response by G-protein-coupled receptor kinase-2 and beta-arrestin1 in FRTL-5 rat thyroid cells. 1209 68

In neonatal cardiomyocytes, activation of the G(q)-coupled alpha(1)-adrenergic receptor (alpha(1)AR) induces hypertrophy by activating mitogen-activated protein kinases, including c-Jun NH(2)-terminal kinase (JNK). Here, we show that JNK activation is essential for alpha(1)AR-induced hypertrophy, in that alpha(1)AR-induced hypertrophic responses, such as reorganization of the actin cytoskeleton and increased protein synthesis, could be blocked by expressing the JNK-binding domain of JNK-interacting protein-1, a specific inhibitor of JNK. We also identified the classes and subunits of G proteins that mediate alpha(1)AR-induced JNK activation and hypertrophic responses by generating several recombinant adenoviruses that express polypeptides capable of inhibiting the function of specific G-protein subunits. alpha(1)AR-induced JNK activation was inhibited by the expression of carboxyl terminal regions of Galpha(q), Galpha(12), and Galpha(13). JNK activation was also inhibited by the Galpha(q/11)- or Galpha(12/13)-specific regulator of G-protein signaling (RGS) domains and by C3 toxin but was not affected by treatment with pertussis toxin or by expression of the carboxyl terminal region of G protein-coupled receptor kinase 2, a polypeptide that sequesters Gbetagamma. alpha(1)AR-induced hypertrophic responses were inhibited by Galpha(q/11)- and Galpha(12/13)-specific RGS domains, C3 toxin, and the carboxyl terminal region of G protein-coupled receptor kinase 2 but not by pertussis toxin. Activation of Rho was inhibited by carboxyl terminal regions of Galpha(12) and Galpha(13) but not by Galpha(q). Our findings suggest that alpha(1)AR-induced hypertrophic responses are mediated in part by a Galpha(12/13)-Rho-JNK pathway, in part by a G(q/11)-JNK pathway that is Rho independent, and in part by a Gbetagamma pathway that is JNK independent.
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PMID:Galpha(12/13) mediates alpha(1)-adrenergic receptor-induced cardiac hypertrophy. 1243 42

In the present study, we examined the roles of G(12), G(13), G(q), and G(i) in endothelin-1-induced hypertrophic responses. Endothelin-1 stimulation activated extracellular signal-regulated kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK) in cultured rat neonatal myocytes. The activation of JNK, but not ERK, was inhibited by the expression of carboxyl terminal regions of G alpha(12) and G alpha(13). JNK activation was also inhibited by expression of the G alpha(12)/G alpha(13)-specific inhibitor regulator of G protein signaling (RGS) domain of p115RhoGEF and the G alpha(q)-specific inhibitor RGS domain of the G protein-coupled receptor kinase 2 (GRK2-RGS). JNK activation was not, however, inhibited by expression of the carboxyl terminal region of G protein-coupled receptor kinase 2 (GRK2-ct), which is a G beta gamma-sequestering polypeptide. Additionally, JNK activation but not ERK activation was inhibited by the expression of C3 exoenzyme that inactivates small GTPase Rho. These results suggest that JNK activation by G alpha(12), G alpha(13), and G alpha(q) is involved in Rho. On the other hand, ERK activation was inhibited by pertussis toxin treatment, the receptor-G(i) uncoupler, and GRK2-ct. Thus, ERK was activated by G alpha(i)- and G beta gamma-dependent pathways. These results clearly demonstrate that differential pathways activate JNK and ERK.
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PMID:Differential requirement of G alpha12, G alpha13, G alphaq, and G beta gamma for endothelin-1-induced c-Jun NH2-terminal kinase and extracellular signal-regulated kinase activation. 1260 54

Endothelin-1 has dual vasoactive effects, mediating vasoconstriction via ETA receptor activation of vascular smooth muscle cells and vasorelaxation via ETB receptor activation of endothelial cells. Although it is commonly accepted that endothelin-1 binding to endothelial cell ETB receptors stimulates nitric oxide (NO) synthesis and subsequent smooth muscle relaxation, the signaling pathways downstream of ETB receptor activation are unknown. Here, using a model in which we have utilized isolated primary endothelial cells, we demonstrate that ET-1 binding to sinusoidal endothelial cell ETB receptors led to increased protein kinase B/Akt phosphorylation, endothelial cell nitric-oxide synthase (eNOS) phosphorylation, and NO synthesis. Furthermore, eNOS activation was not dependent on tyrosine phosphorylation, and pretreatment of endothelial cells with pertussis toxin as well as overexpression of a dominant negative G-protein-coupled receptor kinase construct that sequesters betagamma subunits inhibited Akt phosphorylation and NO synthesis. Taken together, the data elucidate a G-protein-coupled receptor signaling pathway for ETB receptor-mediated NO production and call attention to the absolute requirement for heterotrimeric G-protein betagamma subunits in this cascade.
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PMID:Endothelin-1 activates endothelial cell nitric-oxide synthase via heterotrimeric G-protein betagamma subunit signaling to protein jinase B/Akt. 1452 27


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