51
|
Worzfeld T, Wettschureck N, Offermanns S. G(12)/G(13)-mediated signalling in mammalian physiology and disease. Trends Pharmacol Sci 2008; 29:582-9. [PMID: 18814923 DOI: 10.1016/j.tips.2008.08.002] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 08/08/2008] [Accepted: 08/08/2008] [Indexed: 01/10/2023]
Abstract
The human genome encodes hundreds of G-protein-coupled receptors. Their intracellular effects, however, are mediated by only four families of heterotrimeric G proteins: G(s), G(i)/G(o), G(q)/G(11) and G(12)/G(13). Progress in the knowledge about the G(12)/G(13) family has somewhat lagged behind because their downstream effectors remained unknown for several years, and tools to specifically interfere with G(12)/G(13)-mediated signalling were, therefore, missing. However, with the identification of G(12)/G(13)-regulated signalling pathways and the recent application of new techniques, such as conditional gene inactivation, RNA interference or expression of inhibitory proteins, new insights into the in vivo functions of this G-protein family have been gained. It has become clear that this pathway regulates cellular proliferation, movement and morphology in many different organs and that it is centrally involved in various diseases including cancer and cardiovascular disorders. Here, we focus on recent progress made in the analyses of the in vivo functions of mammalian G(12)/G(13)-mediated signalling.
Collapse
Affiliation(s)
- Thomas Worzfeld
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany
| | | | | |
Collapse
|
52
|
Uluçkan O, Eagleton MC, Floyd DH, Morgan EA, Hirbe AC, Kramer M, Dowland N, Prior JL, Piwnica-Worms D, Jeong SS, Chen R, Weilbaecher K. APT102, a novel adpase, cooperates with aspirin to disrupt bone metastasis in mice. J Cell Biochem 2008; 104:1311-23. [PMID: 18260128 DOI: 10.1002/jcb.21709] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Platelets contribute to the development of metastasis, the most common cause of mortality in cancer patients, but the precise role that anti-platelet drugs play in cancer treatment is not defined. Metastatic tumor cells can produce platelet alphaIIb beta3 activators, such as ADP and thromboxane A(2) (TXA(2)). Inhibitors of platelet beta3 integrins decrease bone metastases in mice but are associated with significant bleeding. We examined the role of a novel soluble apyrase/ADPase, APT102, and an inhibitor of TXA(2) synthesis, acetylsalicylic acid (aspirin or ASA), in mouse models of experimental bone metastases. We found that treatment with ASA and APT102 in combination (ASA + APT102), but not either drug alone, significantly decreased breast cancer and melanoma bone metastases in mice with fewer bleeding complications than observed with alphaIIb beta3 inhibition. ASA + APT102 diminished tumor cell induced platelet aggregation but did not directly alter tumor cell viability. Notably, APT102 + ASA treatment did not affect initial tumor cell distribution and similar results were observed in beta3-/- mice. These results show that treatment with ASA + APT102 decreases bone metastases without significant bleeding complications. Anti-platelet drugs such as ASA + APT102 could be valuable experimental tools for studying the role of platelet activation in metastasis as well as a therapeutic option for the prevention of bone metastases.
Collapse
Affiliation(s)
- Ozge Uluçkan
- Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
53
|
Grenegård M, Vretenbrant-Oberg K, Nylander M, Désilets S, Lindström EG, Larsson A, Ramström I, Ramström S, Lindahl TL. The ATP-gated P2X1 receptor plays a pivotal role in activation of aspirin-treated platelets by thrombin and epinephrine. J Biol Chem 2008; 283:18493-504. [PMID: 18480058 DOI: 10.1074/jbc.m800358200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Human platelets express protease-activated receptor 1 (PAR1) and PAR4 but limited data indicate for differences in signal transduction. We studied the involvement of PAR1 and PAR4 in the cross-talk between thrombin and epinephrine. The results show that epinephrine acted via alpha(2A)-adrenergic receptors to provoke aggregation, secretion, and Ca(2+) mobilization in aspirin-treated platelets pre-stimulated with subthreshold concentrations of thrombin. Incubating platelets with antibodies against PAR4 or the PAR4-specific inhibitor pepducin P4pal-i1 abolished the aggregation. Furthermore, platelets pre-exposed to the PAR4-activating peptide AYPGKF, but not to the PAR1-activating peptide SFLLRN, were aggregated by epinephrine, whereas both AYPGKF and SFLLRN synergized with epinephrine in the absence of aspirin. The roles of released ATP and ADP were elucidated by using antagonists of the purinergic receptors P2X(1), P2Y(1), and P2Y(12) (i.e. NF449, MRS2159, MRS2179, and cangrelor). Intriguingly, ATP, but not ADP, was required for the epinephrine/thrombin-induced aggregation. In Western blot analysis, a low concentration of AYPGKF, but not SFLLRN, stimulated phosphorylation of Akt on serine 473. Moreover, the phosphatidyl inositide 3-kinase inhibitor LY294002 antagonized the effect of epinephrine combined with thrombin or AYPGKF. Thus, in aspirin-treated platelets, PAR4, but not PAR1, interacts synergistically with alpha(2A)-adrenergic receptors, and the PI3-kinase/Akt pathway is involved in this cross-talk. Furthermore, in PAR4-pretreated platelets, epinephrine caused dense granule secretion, and subsequent signaling from the ATP-gated P2X(1)-receptor and the alpha(2A)-adrenergic receptor induced aggregation. These results suggest a new mechanism that has ATP as a key element and circumvents the action of aspirin on epinephrine-facilitated PAR4-mediated platelet activation.
Collapse
Affiliation(s)
- Magnus Grenegård
- Department of Medicine and Health, Division of Drug Research, Division of Clinical Chemistry, Cardiovascular Inflammation Research Center, Linköping University, Linköping SE-581 85 Sweden.
| | | | | | | | | | | | | | | | | |
Collapse
|
54
|
Santos MT, Valles J, Lago A, Tembl J, Sánchez E, Moscardo A, Cosin J. Residual platelet thromboxane A2 and prothrombotic effects of erythrocytes are important determinants of aspirin resistance in patients with vascular disease. J Thromb Haemost 2008; 6:615-21. [PMID: 18221358 DOI: 10.1111/j.1538-7836.2008.02915.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Permanent inactivation of cyclooxygenase-1 and inhibition of platelet thromboxane A(2) (TxA(2)) constitute the main mechanisms underlying the prevention of vascular disease by aspirin. METHODS AND RESULTS We studied platelet TxA(2) synthesis and its impact on platelet reactivity and platelet-erythrocyte [platelet-rich plasma (PRP)-RBC] interactions in 533 aspirin-treated patients with vascular disease. Seventy aspirin-free and 16 aspirin-treated normal subjects were evaluated as controls. Collagen (1 mug mL(-1))-induced platelet activation ((14)C-5HT release) and recruitment (proaggregatory activity of cell-free releasates from activated platelets) were assessed in PRP, PRP + RBC, and whole blood (WB). TxA(2) was quantified in releasates from WB. Aspirin inhibited TxA(2) synthesis and platelet function in all patients, but to different degrees. Forty-two patients (8%) displayed partial (<95%) inhibition of TxA(2) relative to that of aspirin-free controls. They produced >3.5 ng mL(-1) TxA(2) and had higher platelet reactivity than 491 patients who had undetectable TxA(2) or produced residual TxA(2) (R-TxA(2); =3.5 ng mL(-1)). Patients with R-TxA(2) were distributed into TxA(2) quartiles. Patients in the third and fourth quartiles had significantly elevated (14)C-5HT release in PRP, which was markedly amplified in PRP + RBC and WB. TxA(2) in the fourth quartile translated into increased platelet aggregation and recruitment. Significant correlations were found between R-TxA(2) and platelet hyperfunction. CONCLUSION Biochemical markers (TxA(2) synthesis, (14)C-5HT release) and biological assays (platelet aggregation and recruitment) used to monitor the aspirin effect in a large population of patients presenting with vascular disease have evidenced the importance of R-TxA(2) and the prothrombotic effects of RBC in aspirin resistance.
Collapse
Affiliation(s)
- M T Santos
- Research Center, University Hospital La Fe, Valencia, Spain.
| | | | | | | | | | | | | |
Collapse
|
55
|
Characterization of a new peptide agonist of the protease-activated receptor-1. Biochem Pharmacol 2007; 75:438-47. [PMID: 17950254 DOI: 10.1016/j.bcp.2007.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 08/27/2007] [Accepted: 09/04/2007] [Indexed: 01/27/2023]
Abstract
A new peptide (TFRRRLSRATR), derived from the c-terminal of human platelet P2Y(1) receptor, was synthesized and its biological function was evaluated. This peptide activated platelets in a concentration-dependent manner, causing shape change, aggregation, secretion and calcium mobilization. Of the several receptor antagonists tested, only BMS200261, a protease activated receptor 1 (PAR-1) specific antagonist, totally abolished the peptide-induced platelet aggregation, secretion and calcium mobilization. The TFRRR-peptide-pretreated washed platelets failed to aggregate in response to SFLLRN (10 microM) but not to AYPGKF (500 microM). In addition, in mouse platelets, peptide concentrations up to 600 microM failed to cause platelet activation, indicating that the TFRRR-peptide activated platelets through the PAR-1 receptor, rather than through the PAR-4 receptor. The shape change induced by 10 microM peptide was totally abolished by Y-27632, an inhibitor of p160(ROCK) which is a downstream mediator of G12/13 pathways. The TFRRR-peptide, YFLLRNP, and the physiological agonist thrombin selectively activated G12/13 pathways at low concentrations and began to activate both Gq and G12/13 pathways with increasing concentrations. Similar to SFLLRN, the TFRRR-peptide caused phosphorylation of Akt and Erk in a P2Y(12) receptor-dependent manner, and p-38 MAP kinase activation in a P2Y(12)-independent manner. The effects of this peptide are elicited by the first six amino acids (TFRRRL) whereas the remaining peptide (LSRATR), TFERRN, or TFEERN had no effects on platelets. We conclude that TFRRRL activates human platelets through PAR-1 receptors.
Collapse
|
56
|
Fang Y, Ferrie AM. Optical biosensor differentiates signaling of endogenous PAR1 and PAR2 in A431 cells. BMC Cell Biol 2007; 8:24. [PMID: 17587449 PMCID: PMC1925066 DOI: 10.1186/1471-2121-8-24] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Accepted: 06/22/2007] [Indexed: 01/07/2023] Open
Abstract
Background Protease activated receptors (PARs) consist of a family of four G protein-coupled receptors. Many types of cells express several PARs, whose physiological significance is mostly unknown. Results Here, we show that non-invasive resonant waveguide grating (RWG) biosensor differentiates signaling of endogenous protease activated receptor subtype 1 (PAR1) and 2 (PAR2) in human epidermoid carcinoma A431 cells. The biosensor directly measures dynamic mass redistribution (DMR) resulted from ligand-induced receptor activation in adherent cells. In A431, both PAR1 and PAR2 agonists, but neither PAR3 nor PAR4 agonists, trigger dose-dependent Ca2+ mobilization as well as Gq-type DMR signals. Both Ca2+ flux and DMR signals display comparable desensitization patterns upon repeated stimulation with different combinations of agonists. However, PAR1 and PAR2 exhibit distinct kinetics of receptor re-sensitization. Furthermore, both trypsin- and thrombin-induced Ca2+ flux signals show almost identical dependence on cell surface cholesterol level, but their corresponding DMR signals present different sensitivities. Conclusion Optical biosensor provides an alternative readout for examining receptor activation under physiologically relevant conditions, and differentiates the signaling of endogenous PAR1 and PAR2 in A431.
Collapse
Affiliation(s)
- Ye Fang
- Biochemical Technologies, Science and Technology Division, Corning Incorporated, Sullivan Park, Corning, NY 14831, USA
| | - Ann M Ferrie
- Biochemical Technologies, Science and Technology Division, Corning Incorporated, Sullivan Park, Corning, NY 14831, USA
| |
Collapse
|
57
|
Garcia A, Shankar H, Murugappan S, Kim S, Kunapuli S. Regulation and functional consequences of ADP receptor-mediated ERK2 activation in platelets. Biochem J 2007; 404:299-308. [PMID: 17298299 PMCID: PMC1868805 DOI: 10.1042/bj20061584] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have previously shown that ADP-induced thromboxane generation in platelets requires signalling events from the G(q)-coupled P2Y1 receptor (platelet ADP receptor coupled to stimulation of phospholipase C) and the G(i)-coupled P2Y12 receptor (platelet ADP receptor coupled to inhibition of adenylate cyclase) in addition to outside-in signalling. While it is also known that extracellular calcium negatively regulates ADP-induced thromboxane A2 generation, the underlying mechanism remains unclear. In the present study we sought to elucidate the signalling mechanisms and regulation by extracellular calcium of ADP-induced thromboxane A2 generation in platelets. ERK (extracllular-signal-regulated kinase) 2 activation occurred when outside-in signalling was blocked, indicating that it is a downstream event from the P2Y receptors. However, blockade of either P2Y1 or the P2Y12 receptors with corresponding antagonists completely abolished ERK phosphorylation, indicating that both P2Y receptors are required for ADP-induced ERK activation. Inhibitors of Src family kinases or the ERK upstream kinase MEK [MAPK (mitogen-activated protein kinase)/ERK kinase] abrogated ADP-induced ERK phosphorylation and thromboxane A2 generation. Finally ADP- or G(i)+G(z)-induced ERK phosphorylation was blocked in the presence of extracellular calcium. The present studies show that ERK2 is activated downstream of P2Y receptors through a complex mechanism involving Src kinases and this plays an important role in ADP-induced thromboxane A2 generation. We also conclude that extracellular calcium blocks ADP-induced thromboxane A2 generation through the inhibition of ERK activation.
Collapse
Affiliation(s)
- Analia Garcia
- *Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
- †Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
| | - Haripriya Shankar
- *Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
| | - Swaminathan Murugappan
- *Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
- †Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
| | - Soochong Kim
- *Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
- †Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
| | - Satya P. Kunapuli
- *Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
- †Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
- ‡Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, U.S.A
- To whom correspondence should be addressed (email )
| |
Collapse
|
58
|
Abstract
Platelets play a central role in hemostasis, but also in atherothrombosis, as they rapidly adhere to tissue and to one another as a response to any vascular injury. This process involves a large number of surface receptors, signaling pathways, and enzymatic cascades as well as their complex interplay. Although in vitro experiments proved successful in both identifying new receptors and pathways and developing potent and selective antithrombotic drugs, in vitro research cannot mimic the myriad hemodynamic and spatiotemporal cellular and molecular interactions that occur during the generation and propagation of thrombi in vivo. Animal models, and, with the availability of genetically modified mouse strains and of modern intravital imaging techniques, mouse models in particular, have opened new ways to identify both individual roles and the interplay of platelet proteins in complex in vivo settings. In vivo models revealed the important role of, eg, Gas6 or blood coagulation factor XII in thrombus formation, and results obtained in in vivo models raised the interesting possibility that (physiologic) hemostasis and (pathologic) thrombosis might represent 2 mechanistically different processes. This review summarizes in vivo findings that contributed significantly to our understanding of hemostatic and thrombotic processes and which may help to guide future research.
Collapse
Affiliation(s)
- Ulrich J H Sachs
- Rudolf Virchow Center, Deutsche Forschungsgemeinschaft Research Center for Experimental Biomedicine, University of Würzburg, Germany
| | | |
Collapse
|
59
|
Nurden AT. Does ATP act through P2X(1) receptors to regulate platelet activation and thrombus formation? J Thromb Haemost 2007; 5:907-9. [PMID: 17461925 DOI: 10.1111/j.1538-7836.2007.02456.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- A T Nurden
- Institut Fédératif No. 4 and Centre de Référence des Pathologies Plaquettaires, Centre Hospitalier Universitaire de Bordeaux, Pessac, France.
| |
Collapse
|
60
|
Voss B, McLaughlin JN, Holinstat M, Zent R, Hamm HE. PAR1, but not PAR4, activates human platelets through a Gi/o/phosphoinositide-3 kinase signaling axis. Mol Pharmacol 2007; 71:1399-406. [PMID: 17303701 DOI: 10.1124/mol.106.033365] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Thrombin-mediated activation of platelets is critical for hemostasis, but the signaling pathways responsible for this process are not completely understood. In addition, signaling within this cascade can also lead to thrombosis. In this study, we have defined a new signaling pathway for the thrombin receptor protease activated receptor-1 (PAR1) in human platelets. We show that PAR1 couples to G(i/o) in human platelets and activates phosphoinositide-3 kinase (PI3K). PI3K activation regulates platelet integrin alphaIIbbeta3 activation and platelet aggregation and potentiates the PAR1-mediated increase in intraplatelet calcium concentration. PI3K inhibitors eliminated these effects downstream of PAR1, but they had no effect on PAR4 signaling. This study has identified an important role for the direct activation of G(i/o) by PAR1 in human platelets. Given the efficacy of clopidogrel, which blocks the G(i/o)-coupled P2Y purinoceptor 12, as an antiplatelet/antithrombotic drug, our data suggest that specifically blocking only PAR1-mediated G(i/o) signaling could also be an effective therapeutic approach with the possibility of less unwanted bleeding.
Collapse
Affiliation(s)
- Bryan Voss
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA
| | | | | | | | | |
Collapse
|
61
|
Huang JS, Dong L, Kozasa T, Le Breton GC. Signaling through G(alpha)13 switch region I is essential for protease-activated receptor 1-mediated human platelet shape change, aggregation, and secretion. J Biol Chem 2007; 282:10210-22. [PMID: 17298951 DOI: 10.1074/jbc.m605678200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
This study investigated the involvement of Galpha(13) switch region I (SRI) in protease-activated receptor 1 (PAR1)-mediated platelet function and signaling. To this end, myristoylated peptides representing the Galpha(13) SRI (Myr-G(13)SRI(pep)) and its random counterpart were evaluated for their effects on PAR1 activation. Initial studies demonstrated that Myr-G(13)SRI(pep) and Myr-G(13)SRI(Random-pep) were equally taken up by human platelets and did not interfere with PAR1-ligand interaction. Subsequent experiments revealed that Myr-G(13)SRI(pep) specifically bound to platelet RhoA guanine nucleotide exchange factor (p115RhoGEF) and blocked PAR1-mediated RhoA activation in platelets and human embryonic kidney cells. These results suggest a direct interaction of Galpha(13) SRI with p115RhoGEF and a mechanism for Myr-G(13)SRI(pep) inhibition of RhoA activation. Platelet function studies demonstrated that Myr-G(13)SRI(pep) specifically inhibited PAR1-stimulated shape change, aggregation, and secretion in a dose-dependent manner but did not inhibit platelet activation induced by either ADP or A23187. It was also found that Myr-G(13)SRI(pep) inhibited low dose, but not high dose, thrombin-induced aggregation. Additional experiments showed that PAR1-mediated calcium mobilization was partially blocked by Myr-G(13)SRI(pep) but not by the Rho kinase inhibitor Y-27632. Finally, Myr-G(13)SRI(pep) effectively inhibited PAR1-induced stress fiber formation and cell contraction in endothelial cells. Collectively, these results suggest the following: 1) interaction of Galpha(13) SRI with p115RhoGEF is required for G(13)-mediated RhoA activation in platelets; 2) signaling through the G(13) pathway is critical for PAR1-mediated human platelet functional changes and low dose thrombin-induced aggregation; and 3) G(13) signaling elicits calcium mobilization in human platelets through a Rho kinase-independent mechanism.
Collapse
Affiliation(s)
- Jin-Sheng Huang
- Department of Pharmacology, College of Medicine University of Illinois at Chicago, Chicago, Illinois 60612
| | | | | | | |
Collapse
|
62
|
Abstract
Because of their ability to become rapidly activated at places of vascular injury, platelets are important players in primary hemostasis as well as in arterial thrombosis. In addition, they are also involved in chronic pathological processes including the atherosclerotic remodeling of the vascular system. Although primary adhesion of platelets to the vessel wall is largely independent of G protein-mediated signaling, the subsequent recruitment of additional platelets into a growing platelet thrombus requires mediators such as ADP, thromboxane A(2), or thrombin, which act through G protein-coupled receptors. Platelet activation via G protein-coupled receptors involves 3 major G protein-mediated signaling pathways that are initiated by the activation of the G proteins G(q), G(13), and G(i). This review summarizes recent progress in understanding the mechanisms underlying platelet activation and thrombus extension via G protein-mediated signaling pathways.
Collapse
Affiliation(s)
- Stefan Offermanns
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany.
| |
Collapse
|
63
|
|
64
|
|
65
|
Abstract
The G-protein-coupled receptor signaling system, consisting of a huge variety of receptors as well as of many G-proteins and effectors, operates in every cell and is involved in many physiological and pathological processes. The versatility of this system and the involvement of specific components makes G-protein-coupled receptors and their signaling pathways ideal targets for pharmacological interventions. Classical mouse knockout models have often provided important preliminary insights into the biological roles of individual receptors and signaling pathways and they are routinely used in the process of target validation. The recent development of efficient conditional mutagenesis techniques now allows a much more detailed analysis of G-protein-mediated signaling transduction processes. This review summarizes some of the areas in which progress has recently been made by applying conditional mutagenesis of genes coding for G-proteins and G-protein-coupled receptors.
Collapse
Affiliation(s)
- S Offermanns
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany.
| |
Collapse
|
66
|
Minuz P, Fumagalli L, Gaino S, Tommasoli R, Degan M, Cavallini C, Lecchi A, Cattaneo M, Lechi Santonastaso C, Berton G. Rapid stimulation of tyrosine phosphorylation signals downstream of G-protein-coupled receptors for thromboxane A2 in human platelets. Biochem J 2006; 400:127-34. [PMID: 16859489 PMCID: PMC1635449 DOI: 10.1042/bj20061015] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Signals ensuing from trimeric G-protein-coupled receptors synergize to induce platelet activation. At low doses, the thromboxane A2 analogue U46619 does not activate integrin alphaIIbbeta3 or trigger platelet aggregation, but it induces shape changes. In the present study, we addressed whether low doses of U46619 trigger tyrosine phosphorylation independently of integrin alphaIIbbeta3 activation and ADP secretion, and synergize with adrenaline (epinephrine) to induce aggregation in acetylsalicylic acid (aspirin)-treated platelets. Low doses of U46619 triggered tyrosine phosphorylation of different proteins, including FAK (focal adhesion kinase), Src and Syk, independently of signals ensuing from integrin alphaIIbbeta3 or ADP receptors engaged by secreted ADP. The G(12/13)-mediated Rho/Rho-kinase pathway was also increased by low doses of U46619; however, this pathway was not upstream of tyrosine phosphorylation, because this occurred in the presence of the Rho-kinase inhibitor Y-27632. Although low doses of U46619 or adrenaline alone were unable to trigger platelet aggregation and integrin alphaIIbbeta3 activation, the combination of the two stimuli effectively induced these responses. PP2, a tyrosine kinase inhibitor, and Y-27632 inhibited platelet activation induced by low doses of U46619 plus adrenaline and, when used in combination, totally suppressed this platelet response. In addition, the two inhibitors selectively blocked tyrosine kinases and the Rho/Rho-kinase pathway respectively. These findings suggest that both tyrosine phosphorylation and the Rho/Rho-kinase pathway are required to activate platelet aggregation via G(12/13) plus G(z) signalling.
Collapse
Affiliation(s)
- Pietro Minuz
- *Department of Biomedical and Surgical Sciences, University of Verona, Verona, Italy
| | - Laura Fumagalli
- †Department of Pathology, Section of General Pathology, University of Verona, Verona, Italy
| | - Stefania Gaino
- ‡Department of Morphological and Biomedical Sciences, University of Verona, Verona, Italy
| | - Rosa M. Tommasoli
- ‡Department of Morphological and Biomedical Sciences, University of Verona, Verona, Italy
| | - Maurizio Degan
- ‡Department of Morphological and Biomedical Sciences, University of Verona, Verona, Italy
| | - Chiara Cavallini
- ‡Department of Morphological and Biomedical Sciences, University of Verona, Verona, Italy
| | - Anna Lecchi
- §Angelo Bianchi Bonomi Haemophila and Thrombosis Centre, IRCCS Maggiore Hospital, University of Milan, Milan, Italy
| | - Marco Cattaneo
- ∥Unit of Haematology and Thrombosis, San Paolo Hospital, DMCO-University of Milan, Milan, Italy
| | | | - Giorgio Berton
- †Department of Pathology, Section of General Pathology, University of Verona, Verona, Italy
- To whom correspondence should be addressed (email )
| |
Collapse
|
67
|
Kahner BN, Shankar H, Murugappan S, Prasad GL, Kunapuli SP. Nucleotide receptor signaling in platelets. J Thromb Haemost 2006; 4:2317-26. [PMID: 17059469 DOI: 10.1111/j.1538-7836.2006.02192.x] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Upon injury to a vessel wall the exposure of subendothelial collagen results in the activation of platelets. Platelet activation culminates in shape change, aggregation, release of granule contents and generation of lipid mediators. These secreted and generated mediators trigger a positive feedback mechanism potentiating the platelet activation induced by physiological agonists such as collagen and thrombin. Adenine nucleotides, adenosine diphosphate (ADP) and adenosine triphosphate (ATP), released from damaged cells and that are secreted from platelet-dense granules, contribute to the positive feedback mechanism by acting through nucleotide receptors on the platelet surface. ADP acts through two G protein-coupled receptors, the Gq-coupled P2Y1 receptor, and the Gi-coupled P2Y12 receptor. ATP, on the other hand, acts through the ligand-gated channel P2X1. Stimulation of platelets by ADP leads to shape change, aggregation and thromboxane A2 generation. ADP-induced dense granule release depends on generated thromboxane A2. Furthermore, costimulation of both P2Y1 and P2Y12 receptors is required for ADP-induced platelet aggregation. ATP stimulation of P2X1 is involved in platelet shape change and helps to amplify platelet responses mediated by agonists such as collagen. Activation of each of these nucleotide receptors results in unique signal transduction pathways that are important in the regulation of thrombosis and hemostasis.
Collapse
Affiliation(s)
- B N Kahner
- The Cell Signaling Group, Department of Physiology, Temple University School of Medicine, Philadelphia, PA, USA
| | | | | | | | | |
Collapse
|
68
|
Rieken S, Herroeder S, Sassmann A, Wallenwein B, Moers A, Offermanns S, Wettschureck N. Lysophospholipids control integrin-dependent adhesion in splenic B cells through G(i) and G(12)/G(13) family G-proteins but not through G(q)/G(11). J Biol Chem 2006; 281:36985-92. [PMID: 17023430 DOI: 10.1074/jbc.m605287200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Integrin-mediated adhesion is a crucial step in lymphocyte extravasation and homing. We show here that not only the chemokines CXCL12 and CXCL13 but also the lysophospholipids sphingosine 1-phosphate (S1P) and lysophosphatidic acid (LPA) enhance adhesion of murine follicular and marginal zone B cells to ICAM-1 in vitro. This process involves clustering of integrin LFA-1 and is blocked by pertussis toxin, suggesting that G(i) family G-proteins are involved. In addition, lysophospholipid-induced adhesion on ICAM-1 depends on Rho and Rhokinase, indicative of an involvement of G(12)/G(13), possibly also G(q)/G(11) family G-proteins. We used G(12)/G(13)- or G(q)/G(11)-deficient B cells to study the role of these G-protein families in lysophospholipid-induced adhesion and found that the pro-adhesive effects of LPA and S1P are completely abrogated in G(12)/G(13)-deficient marginal zone B cells, reduced in G(12)/G(13)-deficient follicular B cells, and normal in G(q)/G(11)-deficient B cells. We also show that loss of lysophospholipid-induced adhesion results in disinhibition of migration in response to the follicular chemokine CXCL13, which might contribute to the abnormal localization of splenic B cell populations observed in B cell-specific G(12)/G(13)-deficient mice in vivo. Taken together, this study shows that lysophospholipids regulate integrin-mediated adhesion of splenic B cells to ICAM-1 through G(i) and G(12)/G(13) family G-proteins but not through G(q)/G(11).
Collapse
Affiliation(s)
- Stefan Rieken
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, Heidelberg, Germany
| | | | | | | | | | | | | |
Collapse
|
69
|
Abbracchio MP, Burnstock G, Boeynaems JM, Barnard EA, Boyer JL, Kennedy C, Knight GE, Fumagalli M, Gachet C, Jacobson KA, Weisman GA. International Union of Pharmacology LVIII: update on the P2Y G protein-coupled nucleotide receptors: from molecular mechanisms and pathophysiology to therapy. Pharmacol Rev 2006; 58:281-341. [PMID: 16968944 PMCID: PMC3471216 DOI: 10.1124/pr.58.3.3] [Citation(s) in RCA: 987] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
There have been many advances in our knowledge about different aspects of P2Y receptor signaling since the last review published by our International Union of Pharmacology subcommittee. More receptor subtypes have been cloned and characterized and most orphan receptors de-orphanized, so that it is now possible to provide a basis for a future subdivision of P2Y receptor subtypes. More is known about the functional elements of the P2Y receptor molecules and the signaling pathways involved, including interactions with ion channels. There have been substantial developments in the design of selective agonists and antagonists to some of the P2Y receptor subtypes. There are new findings about the mechanisms underlying nucleotide release and ectoenzymatic nucleotide breakdown. Interactions between P2Y receptors and receptors to other signaling molecules have been explored as well as P2Y-mediated control of gene transcription. The distribution and roles of P2Y receptor subtypes in many different cell types are better understood and P2Y receptor-related compounds are being explored for therapeutic purposes. These and other advances are discussed in the present review.
Collapse
Affiliation(s)
- Maria P Abbracchio
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
70
|
Wentworth J, Pula G, Poole A. Vasodilator-stimulated phosphoprotein (VASP) is phosphorylated on Ser157 by protein kinase C-dependent and -independent mechanisms in thrombin-stimulated human platelets. Biochem J 2006; 393:555-64. [PMID: 16197368 PMCID: PMC1360706 DOI: 10.1042/bj20050796] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
VASP (vasodilator-stimulated phosphoprotein) is an actin- and profilin-binding protein that is expressed in platelets at high levels and plays a major role in negatively regulating secretory and adhesive events in these cells. VASP is a major substrate for cAMP- and cGMP-regulated protein kinases and it has been shown to be directly phosphorylated on Ser157 by PKC (protein kinase C). In the present paper, we show that, in human platelets, VASP is phosphorylated by PKC on Ser157, but not Ser239, in response to phorbol ester stimulation, in a manner blocked by the PKC inhibitor BIM I (bisindolylmaleimide I). In response to thrombin, VASP was also phosphorylated on Ser157, but this response was only partially inhibited by BIM I, indicating PKC-dependent and -independent pathways to VASP phosphorylation by thrombin. Using inhibitors, we have ruled out the possibility that the PKC-independent pathway acts through guanylate cyclase generation of cGMP, or through a phosphoinositide 3-kinase-dependent kinase. Inhibition of Rho kinase, however, substantially reduced Ser157 VASP phosphorylation, and its effects were additive with BIM I. This implicates Rho kinase and PKC as the major kinases that phosphorylate VASP Ser157 in response to thrombin in platelets.
Collapse
Affiliation(s)
- James K. T. Wentworth
- Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, U.K
| | - Giordano Pula
- Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, U.K
| | - Alastair W. Poole
- Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, U.K
- To whom correspondence should be addressed (email )
| |
Collapse
|
71
|
Abstract
Heterotrimeric G proteins are key players in transmembrane signaling by coupling a huge variety of receptors to channel proteins, enzymes, and other effector molecules. Multiple subforms of G proteins together with receptors, effectors, and various regulatory proteins represent the components of a highly versatile signal transduction system. G protein-mediated signaling is employed by virtually all cells in the mammalian organism and is centrally involved in diverse physiological functions such as perception of sensory information, modulation of synaptic transmission, hormone release and actions, regulation of cell contraction and migration, or cell growth and differentiation. In this review, some of the functions of heterotrimeric G proteins in defined cells and tissues are described.
Collapse
Affiliation(s)
- Nina Wettschureck
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany
| | | |
Collapse
|
72
|
Soulet C, Hechler B, Gratacap MP, Plantavid M, Offermanns S, Gachet C, Payrastre B. A differential role of the platelet ADP receptors P2Y1 and P2Y12 in Rac activation. J Thromb Haemost 2005; 3:2296-306. [PMID: 16194206 DOI: 10.1111/j.1538-7836.2005.01588.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dynamics of the actin cytoskeleton, largely controlled by the Rho family of small GTPases (Rho, Rac and Cdc42), is critical for the regulation of platelet responses such as shape change, adhesion, spreading and aggregation. Here, we investigated the role of adenosine diphosphate (ADP), a major co-activator of platelets, on the activation of Rac. ADP rapidly activated Rac in a dose-dependent manner and independently of GPIIb/IIIa and phosphoinositide 3-kinase. ADP alone, used as a primary agonist, activated Rac and its effector PAK via its P2Y1 receptor, through a G(q)-dependent pathway and independently of P2Y12. The P2Y12 receptor appeared unable to activate the GTPase per se as also observed for the adenosine triphosphate receptor P2X1. Conversely, secreted ADP strongly potentiated Rac activation induced by FcgammaRIIa clustering or TRAP via its P2Y12 receptor, the target of antithrombotic thienopyridines. Stimulation of the alpha(2A)-adrenergic receptor/G(z) pathway by epinephrine was able to replace the P2Y12/G(i)-mediated pathway to amplify Rac activation by FcgammaRIIa or by the thrombin receptor PAR-1. This co-activation appeared necessary to reach a full stimulation of Rac as well as PAK activation and actin polymerization and was blocked by a G-protein betagamma subunits scavenger peptide.
Collapse
Affiliation(s)
- C Soulet
- Inserm U563, Département d'Oncogenèse et signalisation dans les cellules hématopoïétiques, Hôpital Purpan, Toulouse, France
| | | | | | | | | | | | | |
Collapse
|
73
|
Abstract
Platelets play a central role in hemostasis and thrombosis but also in the initiation of atherosclerosis, making platelet receptors and their intracellular signaling pathways important molecular targets for antithrombotic and anti-inflammatory therapy. Historically, much of the knowledge about hemostasis and thrombosis has been derived from patients suffering from bleeding and thrombotic disorders and the identification of the underlying molecular defects. In recent years, the availability of genetically modified mouse strains with defined defects in platelet function and the development of in vivo models to assess platelet-related physiologic and pathophysiologic processes have opened new ways to identify the individual roles and the interplay of platelet proteins in adhesion, activation, aggregation, secretion, and procoagulant activity in vitro and in vivo. This review will summarize key findings made by these approaches and discuss them in the context of human disease.
Collapse
Affiliation(s)
- B Nieswandt
- Rudolf Virchow Center, DFG Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany.
| | | | | | | |
Collapse
|
74
|
Gachet C. The platelet P2 receptors as molecular targets for old and new antiplatelet drugs. Pharmacol Ther 2005; 108:180-92. [PMID: 15955565 DOI: 10.1016/j.pharmthera.2005.03.009] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Accepted: 03/24/2005] [Indexed: 12/15/2022]
Abstract
Platelet activation by ADP and ATP plays a crucial role in haemostasis and thrombosis, and their so-called P2 receptors are potential targets for antithrombotic drugs. The ATP-gated channel P2X1 and the 2 G protein-coupled P2Y1 and P2Y12 ADP receptors selectively contribute to platelet aggregation. The P2Y1 receptor is responsible for ADP-induced shape change and weak and transient aggregation, while the P2Y12 receptor is responsible for the completion and amplification of the response to ADP and to all platelet agonists, including thromboxane A2 (TXA2), thrombin, and collagen. The P2X1 receptor is involved in platelet shape change and in activation by collagen under shear conditions. Due to its central role in the formation and stabilization of a thrombus, the P2Y12 receptor is a well-established target of antithrombotic drugs like ticlopidine or clopidogrel, which have proved efficacy in many clinical trials and experimental models of thrombosis. Competitive P2Y12 antagonists have also been shown to be effective in experimental thrombosis as well as in several clinical trials. Studies in P2Y1 and P2X1 knockout mice and experimental thrombosis models using selective P2Y1 and P2X1 antagonists have shown that, depending on the conditions, these receptors could also be potential targets for new antithrombotic drugs.
Collapse
Affiliation(s)
- Christian Gachet
- INSERM U.311, Etablissement Français du Sang-Alsace, 10 rue Spielmann, B.P. No. 36, 67065 Strasbourg Cedex, France.
| |
Collapse
|
75
|
McLaughlin JN, Shen L, Holinstat M, Brooks JD, Dibenedetto E, Hamm HE. Functional selectivity of G protein signaling by agonist peptides and thrombin for the protease-activated receptor-1. J Biol Chem 2005; 280:25048-59. [PMID: 15878870 DOI: 10.1074/jbc.m414090200] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Thrombin activates protease-activated receptor-1 (PAR-1) by cleavage of the amino terminus to unmask a tethered ligand. Although peptide analogs can activate PAR-1, we show that the functional responses mediated via PAR-1 differ between the agonists. Thrombin caused endothelial monolayer permeability and mobilized intracellular calcium with EC(50) values of 0.1 and 1.7 nm, respectively. The opposite order of activation was observed for agonist peptide (SFLLRN-CONH(2) or TFLLRNKPDK) activation. The addition of inactivated thrombin did not affect agonist peptide signaling, suggesting that the differences in activation mechanisms are intramolecular in origin. Although activation of PAR-1 or PAR-2 by agonist peptides induced calcium mobilization, only PAR-1 activation affected barrier function. Induced barrier permeability is likely to be Galpha(12/13)-mediated as chelation of Galpha(q)-mediated intracellular calcium with BAPTA-AM, pertussis toxin inhibition of Galpha(i/o), or GM6001 inhibition of matrix metalloproteinase had no effect, whereas Y-27632 inhibition of the Galpha(12/13)-mediated Rho kinase abrogated the response. Similarly, calcium mobilization is Galpha(q)-mediated and independent of Galpha(i/o) and Galpha(12/13) because pertussis toxin Y-27632 and had no effect, whereas U-73122 inhibition of phospholipase C-beta blocked the response. It is therefore likely that changes in permeability reflect Galpha(12/13) activation, and changes in calcium reflect Galpha(q) activation, implying that the pharmacological differences between agonists are likely caused by the ability of the receptor to activate Galpha(12/13) or Galpha(q). This functional selectivity was characterized quantitatively by a mathematical model describing each step leading to Rho activation and/or calcium mobilization. This model provides an estimate that peptide activation alters receptor/G protein binding to favor Galpha(q) activation over Galpha(12/13) by approximately 800-fold.
Collapse
Affiliation(s)
- Joseph N McLaughlin
- Department of Pharmacology, Vanderbilt University Medical Center, Vanderbilt University, Nashville, Tennessee 37232, USA
| | | | | | | | | | | |
Collapse
|
76
|
Steinhoff M, Buddenkotte J, Shpacovitch V, Rattenholl A, Moormann C, Vergnolle N, Luger TA, Hollenberg MD. Proteinase-activated receptors: transducers of proteinase-mediated signaling in inflammation and immune response. Endocr Rev 2005; 26:1-43. [PMID: 15689571 DOI: 10.1210/er.2003-0025] [Citation(s) in RCA: 364] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Serine proteinases such as thrombin, mast cell tryptase, trypsin, or cathepsin G, for example, are highly active mediators with diverse biological activities. So far, proteinases have been considered to act primarily as degradative enzymes in the extracellular space. However, their biological actions in tissues and cells suggest important roles as a part of the body's hormonal communication system during inflammation and immune response. These effects can be attributed to the activation of a new subfamily of G protein-coupled receptors, termed proteinase-activated receptors (PARs). Four members of the PAR family have been cloned so far. Thus, certain proteinases act as signaling molecules that specifically regulate cells by activating PARs. After stimulation, PARs couple to various G proteins and activate signal transduction pathways resulting in the rapid transcription of genes that are involved in inflammation. For example, PARs are widely expressed by cells involved in immune responses and inflammation, regulate endothelial-leukocyte interactions, and modulate the secretion of inflammatory mediators or neuropeptides. Together, the PAR family necessitates a paradigm shift in thinking about hormone action, to include proteinases as key modulators of biological function. Novel compounds that can modulate PAR function may be potent candidates for the treatment of inflammatory or immune diseases.
Collapse
Affiliation(s)
- Martin Steinhoff
- Department of Dermatology and Boltzmann Institute for Immunobiology of the Skin, University of Münster, von-Esmarch-Strasse 58, 48149 Münster, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
77
|
Kim YJ, Sekiya F, Poulin B, Bae YS, Rhee SG. Mechanism of B-cell receptor-induced phosphorylation and activation of phospholipase C-gamma2. Mol Cell Biol 2004; 24:9986-99. [PMID: 15509800 PMCID: PMC525462 DOI: 10.1128/mcb.24.22.9986-9999.2004] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Phospholipase C-gamma2 (PLC-gamma2) plays an important role in B-cell signaling. Phosphorylation of various tyrosine residues of PLC-gamma2 has been implicated in regulation of its lipase activity. With the use of antibodies specific for each of the putative phosphorylation sites, we have now shown that PLC-gamma2 is phosphorylated on Y753, Y759, and Y1217 in response to engagement of the B-cell receptor in Ramos cells, as well as in murine splenic B cells. In cells stimulated maximally via this receptor, the extent of phosphorylation of Y1217 was three times that of Y753 or of Y759. Stimulation of Jurkat T cells or platelets via their immunoreceptors also elicited phosphorylation of Y753 and Y759 but not that of Y1217. A basal level of phosphorylation of Y753 was apparent in unstimulated lymphocytes. The extent of phosphorylation of Y753 and Y759, but not that of Y1217, correlated with the lipase activity of PLC-gamma2. Examination of the effects of various pharmacological inhibitors and of RNA interference in Ramos cells suggested that Btk is largely, but not completely, responsible for phosphorylation of Y753 and Y759, whereas phosphorylation of Y1217 is independent of Btk. Finally, phosphorylation of Y1217 and that of Y753 and Y759 occurred on different PLC-gamma2 molecules.
Collapse
Affiliation(s)
- Yeun Ju Kim
- Laboratory of Cell Signaling, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | | | | | | | | |
Collapse
|
78
|
Sakurai K, Matsuo Y, Sudo T, Takuwa Y, Kimura S, Kasuya Y. Role of p38 Mitogen-Activated Protein Kinase in Thrombus Formation. J Recept Signal Transduct Res 2004; 24:283-96. [PMID: 15648447 DOI: 10.1081/rrs-200040324] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The present study was designed to elucidate the role of p38 mitogen-activated protein kinase (p38) in thrombus formation. We used p38alpha heterozygous (p38alpha+/-) mice and used ferric chloride (FeCl3)-induced carotid artery injury as a model of thrombus formation. The time to thrombotic occlusion induced by FeCl3 in p38alpha+/- mice was prolonged compared to that in wild-type (WT) mice. Platelets prepared from p38alpha+/- mice showed impairment of the aggregatory response to a low concentration of U46619, a thromboxane A2 analogue. Furthermore, platelets prepared from p38alpha+/- mice and activated by U46619 were poorly bound to fibrinogen compared with those from WT mice. Both the expression and activity of tissue factor induced by FeCl3 in WT mice were higher than those in p38alpha+/- mice. These results suggest that p38 plays an important role in thrombus formation by regulating platelet function and tissue factor activity.
Collapse
Affiliation(s)
- Kanako Sakurai
- Department of Biochemistry and Molecular Pharmacology and Chiba University Graduate School of Medicine, Chiba, Japan
| | | | | | | | | | | |
Collapse
|
79
|
Dorsam RT, Kim S, Murugappan S, Rachoor S, Shankar H, Jin J, Kunapuli SP. Differential requirements for calcium and Src family kinases in platelet GPIIb/IIIa activation and thromboxane generation downstream of different G-protein pathways. Blood 2004; 105:2749-56. [PMID: 15546949 DOI: 10.1182/blood-2004-07-2821] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
G(12/13) or G(q) signaling pathways activate platelet GPIIb/IIIa when combined with G(i) signaling. We tested whether combined G(i) and G(z) pathways also cause GPIIb/IIIa activation and compared the signaling requirements of these events. Platelet aggregation occurred by combined stimulation of G(i) and G(z) pathways in human platelets and in P2Y1-deficient and G alpha(q)-deficient mouse platelets, confirming that the combination of G(i) and G(z) signaling causes platelet aggregation. When G(i) stimulation was combined with G(z) stimulation, there was a small mobilization of intracellular calcium. Chelation of intracellular calcium decreased the extent of this platelet aggregation, whereas it abolished the G(q) plus G(i)-mediated platelet aggregation. Costimulation of G(i) plus G(z) pathways also caused thromboxane generation that was dependent on outside-in signaling and was inhibited by PP2, a Src family tyrosine kinase inhibitor. Src family tyrosine kinase inhibitors also inhibited platelet aggregation and decreased the PAC-1 binding caused by costimulation of G(i) and G(z) signaling pathways in aspirin-treated platelets. However, Src family kinase inhibitors did not affect G(q) plus G(i)-mediated platelet aggregation. We conclude that the combination of G(i) plus G(z) pathways have different requirements than G(q) plus G(i) pathways for calcium and Src family kinases in GPIIb/IIIa activation and thromboxane production.
Collapse
Affiliation(s)
- Robert T Dorsam
- Department of Pharmacology, and The Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | | | | | | | | | | | | |
Collapse
|
80
|
Moers A, Wettschureck N, Grüner S, Nieswandt B, Offermanns S. Unresponsiveness of Platelets Lacking Both Gαq and Gα13. J Biol Chem 2004; 279:45354-9. [PMID: 15326177 DOI: 10.1074/jbc.m408962200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The diffusible platelet stimuli ADP and thromboxane A(2) activate multiple G protein-mediated signaling pathways and function as important secondary mediators of platelet activation as they are released from activated platelets. Because they can also increase their own formation and release, their effects are amplified; eventually, all major G protein-mediated signaling pathways are activated. The multiple positive feedback mechanisms operating during platelet activation have obscured the exact analysis of the roles individual G protein-mediated signaling pathways play during the platelet activation process. In this report, we show that platelets lacking G(q) and G(13) are completely unresponsive to diffusible stimuli such as ADP, thromboxane A(2), or thrombin, even when applied at very high concentrations in combination, whereas all stimuli are able to induce platelet aggregation, shape change, and RhoA activation in platelets lacking only one Galpha subunit. This shows that G(q) or G(13) is required to induce some platelet activation, whereas the activation of G(i)-mediated signaling alone is not sufficient to induceactivation of mouse platelets. In addition, platelets lacking Galpha(q) and Galpha(13) adhered normally to collagen under high shearbut did not aggregate any more in response to collagen, indicating that collagen-induced platelet activation but not platelet adhesion requires intact G protein-mediated signaling pathways.
Collapse
Affiliation(s)
- Alexandra Moers
- Pharmakologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | | | | | | | | |
Collapse
|
81
|
Herkert O, Djordjevic T, BelAiba RS, Görlach A. Insights into the redox control of blood coagulation: role of vascular NADPH oxidase-derived reactive oxygen species in the thrombogenic cycle. Antioxid Redox Signal 2004; 6:765-76. [PMID: 15242558 DOI: 10.1089/1523086041361695] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Various cardiovascular diseases including thrombosis, atherosclerosis, (pulmonary) hypertension and diabetes, are associated with disturbed coagulation. Alterations in the vessel wall common to many cardiovascular disorders have been shown to initiate the activity of the coagulation system, but also to be the result of an abnormal coagulation system. The primary link between the coagulation and the vascular system appears to be tissue factor (TF), which is induced on the surface of vascular cells and initiates the extrinsic pathway of the blood coagulation cascade, leading to the formation of thrombin. Thrombin can also interact with the vascular wall via specific receptors and can increase vascular TF expression. Such a "thrombogenic cycle" may be essentially involved in the pathogenesis of cardiovascular disorders associated with an abnormal coagulation. Therefore, the identification of the signaling pathways regulating this cycle and each of its relevant connecting links is of fundamental importance for the understanding of these disorders and their putative therapeutic potential. Reactive oxygen species (ROS) and the ROS-generating NADPH oxidases have been shown to play important roles as signaling molecules in the vasculature. In this review, we summarize the data supporting a substantial role of ROS in promoting a thrombogenic cycle in the vascular system.
Collapse
Affiliation(s)
- Olaf Herkert
- Experimental Pediatric Cardiology, Clinic for Pediatric Cardiology and Congenital Heart Diseases, German Heart Center Munich at the Technical University Munich, 80636
| | | | | | | |
Collapse
|
82
|
Tanaka N, Morita T, Nezu A, Tanimura A, Mizoguchi I, Tojyo Y. Signaling Mechanisms Involved in Protease-Activated Receptor-1-Mediated Interleukin-6 Production by Human Gingival Fibroblasts. J Pharmacol Exp Ther 2004; 311:778-86. [PMID: 15210834 DOI: 10.1124/jpet.104.068569] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human gingival fibroblasts (HGFs) express protease-activated receptor-1 (PAR-1) at high levels. In cultured HGFs, we studied the signaling pathway of thrombin-induced interleukin-6 (IL-6) production. The PAR-1 agonist peptide SFLLRN mimicked the thrombin-induced IL-6 production in the presence of amastatin, an aminopeptidase inhibitor. Thrombin or a combination of SFLLRN and amastatin also strikingly induced the expression of IL-6 mRNA. Although continuous exposure of HGFs to thrombin rapidly desensitized Ca(2+) signaling, the cells did not lose their ability to produce IL-6 in response to thrombin. Similarly, although treatment of HGFs with BAPTA-AM [1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester], an intracellular Ca(2+) chelator, markedly attenuated the thrombin-induced increase in intracellular Ca(2+) concentration, the same treatment did not suppress the thrombin-induced IL-6 production. However, thrombin-induced IL-6 production was strongly inhibited by the p38 mitogen-activated protein (MAP) kinase and tyrosine kinase inhibitors, and Western blotting analyses showed that thrombin stimulates p38 MAP kinase phosphorylation. Specific inhibitors that inhibit extracellular signal-regulated kinase 1/2 kinase, phosphatidylinositol 3-kinase, and RhoA kinase also partially suppressed the thrombin-induced IL-6 production, but the effects were smaller than those of the p38 MAP and tyrosine kinase inhibitors. Thus, thrombin induces HGFs to produce IL-6 by activating PAR-1, and the tyrosine kinase- and p38 MAP kinase-dependent pathways, rather than the Ca(2+) signaling pathway, may play a crucial role in the IL-6 production.
Collapse
Affiliation(s)
- Nobuhisa Tanaka
- Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan.
| | | | | | | | | | | |
Collapse
|
83
|
Quinton TM, Murugappan S, Kim S, Jin J, Kunapuli SP. Different G protein-coupled signaling pathways are involved in alpha granule release from human platelets. J Thromb Haemost 2004; 2:978-84. [PMID: 15140134 DOI: 10.1111/j.1538-7836.2004.00741.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Alpha granule release plays an important role in propagating a hemostatic response upon platelet activation. We evaluated the ability of various agonists to cause alpha granule release in platelets. Alpha granule release was measured by determining P-selectin surface expression in aspirin-treated washed platelets. ADP-induced P-selectin expression was inhibited both by MRS 2179 (a P2Y1 selective antagonist) and AR-C69931MX (a P2Y12 selective antagonist), suggesting a role for both Galpha(q) and Galpha(i) pathways in ADP-mediated alpha granule release. Consistent with these observations, the combination of serotonin (a Galpha(q) pathway stimulator) and epinephrine (a Galpha(z) pathway stimulator) also caused alpha granule release. Furthermore, U46619-induced P-selectin expression was unaffected by MRS 2179 but was dramatically inhibited by AR-C69931, indicating a dominant role for P2Y12 in U46619-mediated alpha granule release. Additionally, the Galpha(12/13)-stimulating peptide YFLLRNP potentiated alpha granule secretion in combination with either ADP or serotonin/epinephrine costimulation but was unable to induce secretion by itself. Finally, costimulation of the Galpha(i) and Galpha(12/13) pathways resulted in a significant dose-dependent increase in alpha granule release. We conclude that ADP-induced alpha granule release in aspirin-treated platelets occurs through costimulation of Galpha(q) and Galpha(i) signaling pathways. The P2Y12 receptor plays an important role in thromboxane A(2)-mediated alpha granule release, and furthermore activation of Galpha(12/13) and Galpha(q) signaling pathway can cause alpha granule release.
Collapse
Affiliation(s)
- T M Quinton
- Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | | | | | | | | |
Collapse
|
84
|
Abstract
The G-protein-mediated signaling system has evolved as one of the most widely used transmembrane signaling mechanisms in eukaryotic organisms. Mammalian cells express many G-protein-coupled receptors as well as several types of heterotrimeric G-proteins and effectors. This review focuses on recent data from studies in mutant mice, which have elucidated some of the roles of G-protein-mediated signaling in physiology and pathophysiology.
Collapse
Affiliation(s)
- Nina Wettschureck
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120, Heidelberg, Germany.
| | | | | |
Collapse
|
85
|
Shankar H, Murugappan S, Kim S, Jin J, Ding Z, Wickman K, Kunapuli SP. Role of G protein-gated inwardly rectifying potassium channels in P2Y12 receptor-mediated platelet functional responses. Blood 2004; 104:1335-43. [PMID: 15142872 DOI: 10.1182/blood-2004-01-0069] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The role of the G(i)-coupled platelet P2Y(12) receptor in platelet function has been well established. However, the functional effector or effectors contributing directly to alphaIIbbeta3 activation in human platelets has not been delineated. As the P2Y(12) receptor has been shown to activate G protein-gated, inwardly rectifying potassium (GIRK) channels, we investigated whether GIRK channels mediate any of the functional responses of the platelet P2Y(12) receptor. Western blot analysis revealed that platelets express GIRK1, GIRK2, and GIRK4. In aspirin-treated and washed human platelets, 2 structurally distinct GIRK inhibitors, SCH23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride) and U50488H (trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(pyrrolidinyl)cyclohexyl] benzeneacetamide methanesulfonate), inhibited adenosine diphosphate (ADP)-, 2-methylthioADP (2-MeSADP)-, U46619-, and low-dose thrombin-mediated platelet aggregation. However, the GIRK channel inhibitors did not affect platelet aggregation induced by high concentrations of thrombin, AYPGKF, or convulxin. Furthermore, the GIRK channel inhibitors reversed SFLLRN-induced platelet aggregation, inhibited the P2Y(12)-mediated potentiation of dense granule secretion and Akt phosphorylation, and did not affect the agonist-induced G(q)-mediated platelet shape change and intracellular calcium mobilization. Unlike AR-C 69931MX, a P2Y(12) receptor-selective antagonist, the GIRK channel blockers did not affect the ADP-induced adenlylyl cyclase inhibition, indicating that they do not directly antagonize the P2Y(12) receptor. We conclude that GIRK channels are important functional effectors of the P2Y(12) receptor in human platelets.
Collapse
Affiliation(s)
- Haripriya Shankar
- Department of Physiology, Temple University, 3420 N Broad St, Philadelphia, PA 19140, USA.
| | | | | | | | | | | | | |
Collapse
|
86
|
Feijge MAH, Ansink K, Vanschoonbeek K, Heemskerk JWM. Control of platelet activation by cyclic AMP turnover and cyclic nucleotide phosphodiesterase type-3. Biochem Pharmacol 2004; 67:1559-67. [PMID: 15041473 DOI: 10.1016/j.bcp.2003.12.028] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Accepted: 12/18/2003] [Indexed: 10/26/2022]
Abstract
Prostaglandin-induced cAMP elevation restrains key signaling pathways in platelet activation including Ca(2+) mobilization and integrin alphaIIbbeta3 affinity regulation. We investigated how cAMP turnover by cyclic nucleotide phosphodiesterases (PDEs) regulates platelet activation. In washed human platelets, inhibition of all PDEs and also specific inhibition of PDE3 but not of PDE5 suppressed thrombin-induced Ca(2+) responses. The effect of general PDE or PDE3 inhibition was accompanied by an increase in cAMP, and potentiated by Gs stimulation with prostaglandin E(1). In platelet-rich plasma, general or PDE3 inhibition blocked platelet aggregation, integrin activation, secretion and thrombin generation. In contrast, inhibition of PDE5 increased the cGMP level, but without significant influence on aggregation, alphaIIbbeta3 activation, secretion or procoagulant activity. Nitroprusside (nitric oxide) potentiated the effect of PDE5 inhibition in elevating cGMP. Nitroprusside inhibited platelet responses, but this was accompanied by elevation of cAMP. Together, these results indicate that cAMP is persistently formed in platelets, independently of agonist-induced Gs stimulation. PDE3 thus functions to keep cAMP at a low equilibrium level and reduce the cAMP-regulated threshold for platelet activation. This crucial role of PDE3, but not of PDE5, extends to all major processes in thrombus formation: assembly of platelets into aggregates, secretion of autocrine products, and procoagulant activity.
Collapse
Affiliation(s)
- Marion A H Feijge
- Department of Biochemistry, University of Maastricht, P.O. Box 616, Maastricht, MD 6200, The Netherlands.
| | | | | | | |
Collapse
|
87
|
Dorsam RT, Kunapuli SP. Central role of the P2Y12 receptor in platelet activation. J Clin Invest 2004. [PMID: 14755328 DOI: 10.1172/jci200420986] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Platelet activation occurs in response to vessel injury and is important for the arrest of bleeding. Platelet activation during disease states leads to vascular occlusion and ischemic damage. The P2Y(12) receptor, activated by ADP, plays a central role in platelet activation and is the target of P2Y(12) receptor antagonists that have proven therapeutic value.
Collapse
Affiliation(s)
- Robert T Dorsam
- Department of Pharmacology, Temple University Medical School, Philadelphia, Pennsylvania 19140, USA
| | | |
Collapse
|
88
|
Roger S, Pawlowski M, Habib A, Jandrot-Perrus M, Rosa JP, Bryckaert M. Costimulation of the Gi-coupled ADP receptor and the Gq-coupled TXA2 receptor is required for ERK2 activation in collagen-induced platelet aggregation. FEBS Lett 2004; 556:227-35. [PMID: 14706855 DOI: 10.1016/s0014-5793(03)01430-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The stimulation of platelets by low doses of collagen induces extracellular signal-regulated kinase 2 (ERK2) activation. In this report, we demonstrate that collagen-induced ERK2 activation depends on thromboxane A(2) (TXA(2)) formation and ADP release. The collagen-induced ERK2 activation was inhibited by indomethacin (88%) and by AR-C69931MX (70%), a specific antagonist of P2Y12, a Gi-coupled ADP receptor. AR-C69931MX (10 microM) inhibition was overcome by epinephrine (1 microM), an agonist of the Gi-coupled alpha(2A)-adrenergic receptor, suggesting that the Gi-coupled receptor was necessary for ERK2 activation by collagen. By contrast, MRS 2179 (10 microM), a specific antagonist of P2Y1, a Gq-coupled ADP receptor, did not affect collagen-induced ERK2 activation. Little or no ERK2 activation was observed with ADP alone (10 microM). By contrast, U46619 (10 microM), a stable analog of TXA(2), induced ERK2 activation in an ADP-dependent manner, via the P2Y12 receptor. These results suggest that the Gi-dependent signaling pathway, stimulated by ADP or epinephrine, was not the only pathway required for ERK2 activation by collagen. Costimulation of the specific G(12/13)-coupled TXA(2) receptor with a low dose of U46619 (10 nM) and of Gi- and Gq-coupled ADP receptor (10 microM) induced very low levels of ERK2 activation, similar to those observed with ADP alone, suggesting that G(12/13) is not involved or not sufficient to induce the additional pathway necessary for ERK2 activation. The Gq-coupled TXA(2) receptor was required for ERK2 activation by U46619 (10 microM) and low doses of collagen, clearly showing that a coordinated pathway through both Gq from TXA(2) and Gi from ADP was necessary for ERK2 activation. Finally, we demonstrate that ERK2 activation is involved in collagen-induced aggregation and secretion.
Collapse
MESH Headings
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/metabolism
- 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid/pharmacology
- Adenosine Diphosphate/analogs & derivatives
- Adenosine Diphosphate/pharmacology
- Adenosine Monophosphate/analogs & derivatives
- Adenosine Monophosphate/pharmacology
- Animals
- Cattle
- Collagen/metabolism
- Collagen/pharmacology
- Enzyme Activation/drug effects
- Epinephrine/pharmacology
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Humans
- Integrin alpha2beta1/metabolism
- Membrane Proteins/antagonists & inhibitors
- Membrane Proteins/metabolism
- Mitogen-Activated Protein Kinase 1/metabolism
- Phosphorylation
- Platelet Aggregation/drug effects
- Platelet Membrane Glycoproteins/metabolism
- Protein Kinase C/metabolism
- Purinergic P2 Receptor Antagonists
- Receptors, Purinergic P2/metabolism
- Receptors, Purinergic P2Y12
- Receptors, Thromboxane A2, Prostaglandin H2/antagonists & inhibitors
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
- Signal Transduction
- Thromboxane A2/metabolism
- Thromboxane A2/pharmacology
Collapse
Affiliation(s)
- Séverine Roger
- U348 INSERM, IFR 6 Circulation Lariboisière, Hôpital Lariboisière, 41 Bd de la Chapelle, 75475 Cedex 10, Paris, France
| | | | | | | | | | | |
Collapse
|
89
|
Abstract
Platelet activation occurs in response to vessel injury and is important for the arrest of bleeding. Platelet activation during disease states leads to vascular occlusion and ischemic damage. The P2Y(12) receptor, activated by ADP, plays a central role in platelet activation and is the target of P2Y(12) receptor antagonists that have proven therapeutic value.
Collapse
Affiliation(s)
- Robert T Dorsam
- Department of Pharmacology, Temple University Medical School, Philadelphia, Pennsylvania 19140, USA
| | | |
Collapse
|
90
|
Huang C, Hujer KM, Wu Z, Miller RT. The Ca2+-sensing receptor couples to Galpha12/13 to activate phospholipase D in Madin-Darby canine kidney cells. Am J Physiol Cell Physiol 2004; 286:C22-30. [PMID: 12954603 DOI: 10.1152/ajpcell.00229.2003] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Ca2+-sensing receptor (CaR) couples to multiple G proteins involved in distinct signaling pathways: Galphai to inhibit the activity of adenylyl cyclase and activate ERK, Galphaq to stimulate phospholipase C and phospholipase A2, and Gbetagamma to stimulate phosphatidylinositol 3-kinase. To determine whether the receptor also couples to Galpha12/13, we investigated the signaling pathway by which the CaR regulates phospholipase D (PLD), a known Galpha12/13 target. We established Madin-Darby canine kidney (MDCK) cell lines that stably overexpress the wild-type CaR (CaRWT) or the nonfunctional mutant CaRR796W as a negative control, prelabeled these cells with [3H]palmitic acid, and measured CaR-stimulated PLD activity as the formation of [3H]phosphatidylethanol (PEt). The formation of [3H]PEt increased in a time-dependent manner in the cells that overexpress the CaRWT but not the CaRR796W. Treatment of the cells with C3 exoenzyme inhibited PLD activity, which indicates that the CaR activates the Rho family of small G proteins, targets of Galpha12/13. To determine which G protein(s) the CaR couples to in order to activate Rho and PLD, we pretreated the cells with pertussis toxin to inactivate Galphai or coexpressed regulators of G protein-signaling (RGS) proteins to attenuate G protein signaling (RGS4 for Galphai and Galphaq, and a p115RhoGEF construct containing the RGS domain for Galpha12/13). Overexpression of p115RhoGEF-RGS in the MDCK cells that overexpress CaRWT inhibited extracellular Ca2+-stimulated PLD activity, but pretreatment of cells with pertussis toxin and overexpression of RGS4 were without effect. The involvement of other signaling components such as protein kinase C, ADP-ribosylation factor, and phosphatidylinositol biphosphate was excluded. These findings demonstrate that the CaR couples to Galpha12/13 to regulate PLD via a Rho-dependent mechanism and does so independently of Galphai and Galphaq. This suggests that the CaR may regulate cytoskeleton via Galpha12/13, Rho, and PLD.
Collapse
Affiliation(s)
- Chunfa Huang
- Division of Nephrology, Department of Medicine, Case Western Reserve University, Louis Stokes Veteran Affairs Medical Center, 10701 East Boulevard 151W, Cleveland, OH 44106, USA.
| | | | | | | |
Collapse
|
91
|
Abstract
At the injured vessel wall, blood platelets become activated and adhere to the subendothelial surface as well as to each other. These cellular adhesion processes are required for primary hemostasis, but can also lead to thrombosis. Considerable progress has been made during recent years in understanding the molecular mechanisms underlying platelet activation and adhesion. This knowledge will drive future efforts towards the development of new antiplatelet drugs for the prevention and treatment of cardiovascular diseases.
Collapse
Affiliation(s)
- B Nieswandt
- Rudolf Virchow Center for Experimental Biomedicine, Vascular Biology, University of Würzburg, 97078, Würzburg, Germany
| | | |
Collapse
|
92
|
Haserück N, Erl W, Pandey D, Tigyi G, Ohlmann P, Ravanat C, Gachet C, Siess W. The plaque lipid lysophosphatidic acid stimulates platelet activation and platelet-monocyte aggregate formation in whole blood: involvement of P2Y1 and P2Y12 receptors. Blood 2003; 103:2585-92. [PMID: 14645014 DOI: 10.1182/blood-2003-04-1127] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Despite the fact that lysophosphatidic acid (LPA) has been identified as a main platelet-activating lipid of mildly oxidized low-density lipoprotein (LDL) and human atherosclerotic lesions, it remains unknown whether it is capable of activating platelets in blood. We found that LPA at concentrations slightly above plasma levels induces platelet shape change, aggregation, and platelet-monocyte aggregate formation in blood. 1-alkyl-LPA (16:0 fatty acid) was almost 20-fold more potent than 1-acyl-LPA (16:0). LPA directly induced platelet shape change in blood and platelet-rich plasma obtained from all blood donors. However, LPA-stimulated platelet aggregation in blood was donor dependent. It could be completely blocked by apyrase and antagonists of the platelet adenosine diphosphate (ADP) receptors P2Y1 and P2Y12. These substances also inhibited LPA-induced aggregation of platelet-rich plasma and aggregation and serotonin secretion of washed platelets. These results indicate a central role for ADP-mediated P2Y1 and P2Y12 receptor activation in supporting LPA-induced platelet aggregation. Platelet aggregation and platelet-monocyte aggregate formation stimulated by LPA was insensitive to inhibition by aspirin. We conclude that LPA at concentrations approaching those found in vivo can induce platelet shape change, aggregation, and platelet-monocyte aggregate formation in whole blood and suggest that antagonists of platelet P2Y1 and P2Y12 receptors might be useful preventing LPA-elicited thrombus formation in patients with cardiovascular diseases.
Collapse
Affiliation(s)
- Nadine Haserück
- Institute for Prevention of Cardiovascular Diseases, University of Munich, Germany
| | | | | | | | | | | | | | | |
Collapse
|
93
|
Moers A, Nieswandt B, Massberg S, Wettschureck N, Grüner S, Konrad I, Schulte V, Aktas B, Gratacap MP, Simon MI, Gawaz M, Offermanns S. G13 is an essential mediator of platelet activation in hemostasis and thrombosis. Nat Med 2003; 9:1418-22. [PMID: 14528298 DOI: 10.1038/nm943] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Accepted: 09/13/2003] [Indexed: 11/09/2022]
Abstract
Platelet activation at sites of vascular injury is essential for primary hemostasis, but also underlies arterial thrombosis leading to myocardial infarction or stroke. Platelet activators such as adenosine diphosphate, thrombin or thromboxane A(2) (TXA(2)) activate receptors that are coupled to heterotrimeric G proteins. Activation of platelets through these receptors involves signaling through G(q), G(i) and G(z) (refs. 4-6). However, the role and relative importance of G(12) and G(13), which are activated by various platelet stimuli, are unclear. Here we show that lack of Galpha(13), but not Galpha(12), severely reduced the potency of thrombin, TXA(2) and collagen to induce platelet shape changes and aggregation in vitro. These defects were accompanied by reduced activation of RhoA and inability to form stable platelet thrombi under high shear stress ex vivo. Galpha(13) deficiency in platelets resulted in a severe defect in primary hemostasis and complete protection against arterial thrombosis in vivo. We conclude that G(13)-mediated signaling processes are required for normal hemostasis and thrombosis and may serve as a new target for antiplatelet drugs.
Collapse
Affiliation(s)
- Alexandra Moers
- Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
94
|
Li Z, Zhang G, Le Breton GC, Gao X, Malik AB, Du X. Two waves of platelet secretion induced by thromboxane A2 receptor and a critical role for phosphoinositide 3-kinases. J Biol Chem 2003; 278:30725-31. [PMID: 12796499 DOI: 10.1074/jbc.m301838200] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thromboxane A2 (TXA2)-mediated platelet secretion and aggregation are important in thrombosis. Here, we present a novel finding that the stable TXA2 analogue, U46619, induces two waves of platelet secretion, each of which precedes a distinct wave of platelet aggregation. ADP released from platelets during the first wave of secretion played a major role in augmenting the first wave of platelet aggregation. The second wave of platelet secretion and aggregation required the first wave of both ADP secretion and aggregation and were blocked by either the integrin inhibitor RGDS or a P2Y12 receptor antagonist, indicating a requirement for both the integrin outside-in signal and ADP-activated Gi pathway. U46619 stimulated phosphoinositide 3-kinase (PI3K)-dependent phosphorylation of Akt, which was augmented by ADP but did not require integrin outside-in signaling. Platelets from PI3Kgamma knock-out mice or PI3K inhibitor-treated platelets showed an impaired second wave of platelet secretion and aggregation. However, the second wave of platelet aggregation was restored by addition of exogenous ADP to PI3Kgamma deficient or PI3K inhibitor-treated platelets. Thus, our data indicate that PI3K, together with the integrin outside-in signaling, play a central role in inducing the second wave of platelet secretion, which leads to the second wave of irreversible platelet aggregation.
Collapse
Affiliation(s)
- Zhenyu Li
- Department of Pharmacology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA
| | | | | | | | | | | |
Collapse
|