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Li J, Guo J, Shang E, Zhu Z, Zhu KY, Li S, Zhao B, Jia L, Zhao J, Tang Z, Duan J. A metabolomics strategy to explore urinary biomarkers and metabolic pathways for assessment of interaction between Danhong injection and low-dose aspirin during their synergistic treatment. J Chromatogr B Analyt Technol Biomed Life Sci 2016; 1026:168-175. [DOI: 10.1016/j.jchromb.2015.07.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/26/2015] [Accepted: 07/22/2015] [Indexed: 01/01/2023]
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CHEN YIXIN, CHEN XIAOWEN, LI CHANGGANG, YUE LIJIE, MAI HUIRONG, WEN FEIQIU. Effect of tumor gangliosides on tyrosine phosphorylation of p125FAK in platelet adhesion to collagen. Oncol Rep 2012; 29:343-8. [DOI: 10.3892/or.2012.2092] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 09/28/2012] [Indexed: 11/05/2022] Open
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Gupta R, Chakrabarti P, Dikshit M, Dash D. Late signaling in the activated platelets upregulates tyrosine phosphatase SHP1 and impairs platelet adhesive functions: Regulation by calcium and Src kinase. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:131-40. [PMID: 17046078 DOI: 10.1016/j.bbamcr.2006.08.055] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 08/28/2006] [Accepted: 08/30/2006] [Indexed: 10/24/2022]
Abstract
Sustained stimulation of platelets with protease-activated receptor agonists in presence of extracellular calcium was associated with tyrosine dephosphorylation of specific proteins of relative mobilities 35, 67, and 75 kDa. From phosphatase assays and inhibitor studies SHP1, a Src homology 2 (SH2) domain-containing tyrosine phosphatase expressed abundantly in hemopoietic cells, was found to be upregulated in platelets between 25 and 30 min following thrombin stimulation. Concomitantly, SHP1 was tyrosine phosphorylated by, and coprecipitated with, Src tyrosine kinase. SHP1 activation, association with Src and dephosphorylation of specific proteins were dependent on extracellular calcium and maintenance of a higher cytosolic calcium plateau. There was progressive impairment of platelet functions like aggregability and clot retraction, associated with downregulation of fibrinogen-binding affinity of integrin alpha(IIb)beta(3), in the platelets exposed to thrombin for 45 min. This could reflect the late physiological changes in platelets when the cells are consistently exposed to stimulatory signals under thrombogenic environment in vivo.
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Affiliation(s)
- Ramkrishna Gupta
- Department of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi-221005, India
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Hernández-Hernández A, Garabatos MN, Rodríguez MC, Vidal ML, López-Revuelta A, Sánchez-Gallego JI, Llanillo M, Sánchez-Yagüe J. Structural characteristics of a lipid peroxidation product, trans-2-nonenal, that favour inhibition of membrane-associated phosphotyrosine phosphatase activity. Biochim Biophys Acta Gen Subj 2005; 1726:317-25. [PMID: 16269214 DOI: 10.1016/j.bbagen.2005.09.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 09/28/2005] [Accepted: 09/30/2005] [Indexed: 10/25/2022]
Abstract
Protein-tyrosine phosphatases (PTPs) are very susceptible to oxidation by reactive oxygen species (ROS), which induce the oxidation of catalytic cysteines, thereby inactivating these PTPs. PTPs are also inactivated by treatment with different aldehydes (such as trans-2-nonenal), produced after tissue damage by ROS. However, the molecular mechanisms behind such aldehyde-due inactivation remain unknown. Using commercially available compounds, we examined the structural characteristics of trans-2-nonenal that allow the inhibition of platelet membrane-associated PTP activity, as well as how these compounds affect the dynamics of SH-, CO- and NH2- protein groups on the membranes. PTP was effectively inhibited by physiological amounts of trans-2-nonenal (1-10 microM). Incubation with trans-2-nonene (10 microM) also decreased PTP activity, although to a lower extent. Treatment with nonyl aldehyde almost eliminated PTP inhibition. Decreases in protein thiols were visible after trans-2-nonenal and trans-2-nonene treatments. Both the latter compounds also increased protein carbonyls (although trans-2-nonenal was more effective) and decreased protein amino groups to an equal extent. Collectively, our data indicate that alpha,beta unsaturation (and not a double bond in another position) is the most important structural determinant for PTP inhibition, the alkenal with 9-carbon atoms being the most effective in eliciting such inhibition. The data allow us to predict the modification of sulfhydryls and/or the formation of addition products with lysyl or histidyl residues, and hence the kind of specific antibodies that it would be necessary to generate in order to test such modifications directly.
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Affiliation(s)
- Angel Hernández-Hernández
- Department of Biochemistry and Molecular Biology, University of Salamanca, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain
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Hernández-Hernández A, Sánchez-Bernal C, Rodríguez MC, Gómez FP, Llanillo M, Sánchez-Yagüe J. Loss of phosphotyrosine phosphatase activity and changes in the tyrosine phosphorylation state of proteins after storage of sheep platelets in plasma or Seto solution at 4 degrees C. Vox Sang 2001; 81:241-7. [PMID: 11904000 DOI: 10.1046/j.1423-0410.2001.00111.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND AND OBJECTIVES During platelet storage an array of deleterious changes occur, through mechanisms not fully understood, which impair platelet haemostasis. Transfused platelets should maintain the integrated networks of signalling pathways that regulate platelet activation and functionality. We hypothesized that protein phosphorylation and dephosphorylation, which play a fundamental role in these pathways, might be affected by platelet storage. We therefore investigated whether the activity of phosphotyrosine phosphatase (PTP), which belongs to an oxidant-susceptible group of enzymes involved in the platelet signal-transduction pathways that ensure platelet functionality, is affected by platelet storage. MATERIALS AND METHODS Using sheep platelet species as a model system, we conducted serial studies on the membranes of platelets and microparticles shed during platelet storage, in their own plasma or in a synthetic medium called Seto, for up to 5 days at 4 degrees C. RESULTS A progressive decrease in both total and specific membrane-associated PTP activities from whole platelets (but not from microparticles) located within each platelet storage bag was observed from day 1 onwards in both types of storage media. These decreases could be partly avoided by the addition of vitamin E. Additionally, the observed decrease in PTP activity was accompanied with increases in the tyrosine phosphorylation of proteins from whole platelets or crude platelet membranes, the tyrosine phosphorylation state of proteins from microparticles remaining basically unchanged. CONCLUSION Our findings suggest that alterations of at least the tyrosine phosphorylation balance might be one of the reasons for the decrease in the haemostatic function of stored platelets.
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Affiliation(s)
- A Hernández-Hernández
- Department of Biochemistry and Molecular Biology, University of Salamanca, 106 Plaza Doctores de la Reina, E-37007 Salamanca, Spain
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Schoene NW, Guidry CA. Genistein inhibits reactive oxygen species (ROS) production, shape change, and aggregation in rat platelets. Nutr Res 2000. [DOI: 10.1016/s0271-5317(99)00137-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Catalán RE, Gargiulo L, Martínez AM, Liras A. Endothelin-1 effect on tyrosine phosphorylation and on tyrosine phosphatase (PTP-1C) translocation in rabbit platelets. J Recept Signal Transduct Res 1999; 19:909-25. [PMID: 10533980 DOI: 10.3109/10799899909038431] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This study examined the temporal relationships of endothelin-1-stimulated rabbit platelets tyrosine phosphorylated proteins. The effect of endothelin-1 on tyrosine phosphorylation was dose- and time-dependent and caused a rapid tyrosine phosphorylation of three groups of proteins in the molecular mass range 70-100 kDa, 100-150 kDa and 150-200 kDa. Significant protein tyrosine phosphatase activity and amount were found to be associated with the cytoskeleton of endothelin-1-stimulated rabbit platelets. Under our experimental conditions, translocation from the cytosolic fraction to the cytoskeleton reached its highest levels within 10-20 sec of endothelin-1 stimulation. Endothelin-1-induced translocation of protein tyrosine phosphatase, associated with the increase in its activity was demonstrated by immunoblotting and immunoelectron microscopy.
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Affiliation(s)
- R E Catalán
- Departamento Biología Molecular/Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM) Universidad Autónoma de Madrid, Spain
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Hernández-Hernández A, Llanillo M, Rodríguez MC, Gómez F, Sánchez-Yagüe J. Amphiphilic and hydrophilic nature of sheep and human platelet phosphotyrosine phosphatase forms. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1419:195-206. [PMID: 10407071 DOI: 10.1016/s0005-2736(99)00066-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To date, although at least 75 different PTPases (protein-tyrosine-phosphate-phosphohydrolase, EC 3.1.3.48) have been identified, those detected in platelets are rather scarce. Based on previous results from our laboratory, we investigated the existence of new PTPases in platelets. Triton X-114 phase partitioning of Triton X-100-solubilized human and sheep platelet membranes allowed PTPase to be recovered in the detergent-rich (40-35%, respectively) and -poor phases (60-65%, respectively). Sedimentation analyses of both phases from the sheep species revealed hydrophilic 6S and 3.7S, and amphiphilic 7.5S and 10.3S PTPase forms. Sedimentation analyses of human platelet membrane-associated or cytosolic PTPase revealed hydrophilic 6.7S and 4.3S, and amphiphilic 5.5S and 10.8S forms, or hydrophilic 4S, 5.9S and 6.9S forms, respectively. Western blot analysis using monoclonal antibodies (MoAb) against human PTP1B, PTP1C, PTP1D and RPTPalpha (mouse anti-human PTPase MoAbs) showed that RPTPalpha was not present in platelets and that the PTP1C type and PTP1D type (but probably not the PTP1B type) were expressed in sheep species. Immunoblots also revealed that all PTPases detected were mainly membrane-associated, with similar percentages of cellular distribution in both species. All PTPases were mainly recovered in the detergent-poor phases from the Triton X-114 phase partitioning, although PTP1D from human species was also significantly present (30%) in the detergent-rich phase. Additionally, all PTPases sedimented within the same PTPase peak in sucrose gradients (sedimentation coefficients around 4S). These findings indicate that amphiphilic and hydrophilic PTPases different from PTP1B, PTP1C, PTP1D or RPTPalpha, with higher sedimentation coefficients and with higher activity when O-phosphotyrosine or a synthetic peptide phosphorylated on tyrosine were used as substrates, are present in platelets.
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Affiliation(s)
- A Hernández-Hernández
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental (Laboratorio 106), Plaza Doctores de la Reina s/n, E-37007, Salamanca, Spain
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9
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Hernández-Hernández A, Sánchez-Yagüe J, Martín-Valmaseda EM, Llanillo M. Oxidative inactivation of human and sheep platelet membrane-associated phosphotyrosine phosphatase activity. Free Radic Biol Med 1999; 26:1218-30. [PMID: 10381193 DOI: 10.1016/s0891-5849(98)00306-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Incubation of human or sheep platelet crude membranes with xanthine oxidase/hypoxanthine in the presence of Fe2+/ADP inactivated phosphotyrosine phosphatase (PTPase, protein-tyrosine-phosphate-phosphohydrolase, EC 3.1.3.48) activity in a time-dependent manner, this inhibition being significant within 5 min of treatment. The dynamics of protein thiols differed depending on the platelet species, but in any case decreases in protein thiols were only visible 20-45 min after the start of the treatment. The inhibition of PTPase activity in general showed good a correlation with the production of thiobarbituric acid-reactive substances (TBARS). The results with several antioxidants suggest that the inhibition of PTPase activity is related to the generation of alkoxyl and/or peroxyl radicals. Furthermore, the formation of fluorescent products and changes in amino groups were observed only after long incubation times with the oxidizing agents, these fluorescent products and the residual enzyme activity remaining in the membrane fraction. Treatment of platelet membranes with trans-2-nonenal and n-heptaldehyde, but not with acetaldehyde, also inhibited membrane-associated PTPase activity. However, the amount of protein thiols was reduced only by treatment with trans-2-nonenal. Fluorescence product formation was always higher with trans-2-nonenal, these products being mainly located in the protein fraction. The results with aldehydes suggest that secondary degraded products of lipid hydroperoxides affect PTPase activity. Kinetic studies of PTPase activity indicated that with all treatments enzyme inhibition is mainly due to a decrease in the Vmax value. The results of fluorescence anisotropy measurements of labeled platelet membranes did not support the notion of a contribution of the lipid organization to peroxidation-mediated PTPase inhibition. All the above results indicate that platelet membrane-associated PTPase inhibition due to treatment with xanthine oxidase/ hypoxanthine in the presence of Fe2+/ADP is a very complex, time-dependent process, and that it is probably related, at least after long periods of peroxidation, to changes in protein thiols and amino groups. We predict that the sensitivity of PTPase to lipid peroxidation must be physiologically relevant because of the increasing importance of tyrosine phosphorylation in signal transduction, in general, and in platelet activation and aggregation in particular.
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Pasquet JM, Dachary-Prigent J, Nurden AT. Microvesicle release is associated with extensive protein tyrosine dephosphorylation in platelets stimulated by A23187 or a mixture of thrombin and collagen. Biochem J 1998; 333 ( Pt 3):591-9. [PMID: 9677317 PMCID: PMC1219621 DOI: 10.1042/bj3330591] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Phosphatidylserine exposure and microvesicle release give rise to procoagulant activity during platelet activation. We have previously shown that whereas the Ca2+ ionophore A23187 and 2,5-di-(t-butyl)-1, 4-benzohydroquinone, a Ca2+-ATPase inhibitor, induce phosphatidylserine exposure, only the former triggers microvesicle release. We now report that microvesicle formation with ionophore A23187 is specifically associated with mu-calpain activation, increased protein tyrosine phosphatase (PTP) activity and decreased tyrosine phosphorylation. The degree to which calpain and individual PTPs were activated in response to A23187 depended on the extent of bivalent cation chelation in the external medium. EGTA (2 mM) blocked or severely retarded their activation, and addition of extracellular Ca2+ in excess (2 mM) resulted in virtually immediate tyrosine dephosphorylation. Dephosphorylation was correlated with an increase in total PTP activity in platelet lysates. In platelets stimulated by a combination of thrombin and collagen, only the subpopulation undergoing microvesicle release and isolated by their binding to annexin-V-coated magnetic beads exhibited protein tyrosine dephosphorylation. Detection of PTP activity in an 'in-gel' assay showed the Ca2+-dependent appearance of active low-molecular-mass bands at 38, 36 and 27 kDa. Individual PTPs varied in their protease sensitivity to changes in intracellular Ca2+ levels. For example, PTP1B was a more sensitive substrate than SH2-domain-containing tyrosine phosphatase-1 for mu-calpain cleavage. Incubation of platelets with the PTP inhibitors, phenylarsine oxide and benzylphosphonic acid acetoxymethyl ester, led to increased tyrosine phosphorylation and the surface expression of aminophospholipids but little microvesicle formation. Furthermore, microvesicle release in response to ionophore A23187 was inhibited. We conclude that platelet microvesicle formation is associated with extensive protein tyrosine dephosphorylation.
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Affiliation(s)
- J M Pasquet
- UMR 5533 CNRS, Hôpital Cardiologique, 33604 Pessac, France
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11
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Hernández-Hernández A, Sánchez-Yagüe J, Martín-Valmaseda EM, Llanillo M. Characterization of phosphotyrosine phosphatase activity in sheep platelets: amphiphilic and hydrophilic forms. Comp Biochem Physiol B Biochem Mol Biol 1997; 117:437-44. [PMID: 9253182 DOI: 10.1016/s0305-0491(97)00141-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Using O-phosphotyrosine as a substrate, we characterized the phosphotyrosine phosphatase (PTPase; protein-tyrosine-phosphate-phosphohydrolase, EC 3.1.3.48) activity from sheep platelets. PTPase was found to be located in three particulate subcellular fractions and in the cytosol, with K(m) values in the millimolar range. PTPase was strongly inhibited by vanadate, molybdate and HgCl2 and only weakly inhibited by Zn2+. Other divalent cations and NaF had no significant effect on the activity associated with the membrane fraction but were slightly stimulatory as regards cytosolic activity. Heparin inhibited cytosolic activity 2-fold more than membrane-bound activity and dithiothreitol only inhibited cytosolic PTPase. Polycationic compounds were seen to be weak stimulators of all the PTPase activity. Solubilization of the PTPase from membranes always required a detergent. When subjected to Triton X-114 phase partitioning, PTPase was recovered in the detergent-rich (35%) and in the detergent-poor (65%) phases. Sedimentation analysis of the cytosolic PTPase showed a peak of 3.2S that remained unmodified when Triton X-100 or Brij 97 sucrose gradients were used. Sedimentation analysis of the membrane-associated PTPase showed 6S and 3.7S peaks unchanged in Triton X-100 or Brij 97 gradients together with 7.5S and 10.3S shoulders that shifted to smaller sedimentation coefficients in Brij 97 sucrose gradients. These results support the view that sheep platelets contain amphiphilic and hydrophilic forms of PTPase.
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Affiliation(s)
- A Hernández-Hernández
- Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departmental, Spain
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12
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The Platelet Integrin, GP IIb-IIIa (αIIbß3). ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1569-2558(08)60411-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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13
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Borges LG, Seifert RA, Grant FJ, Hart CE, Disteche CM, Edelhoff S, Solca FF, Lieberman MA, Lindner V, Fischer EH, Lok S, Bowen-Pope DF. Cloning and characterization of rat density-enhanced phosphatase-1, a protein tyrosine phosphatase expressed by vascular cells. Circ Res 1996; 79:570-80. [PMID: 8781490 DOI: 10.1161/01.res.79.3.570] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have cloned from cultured vascular smooth muscle cells a protein tyrosine phosphatase, rat density-enhanced phosphatase-1 (rDEP-1), which is a probable rat homologue of DEP-1/HPTP eta. rDEP-1 is encoded by an 8.7-kb transcript and is expressed as a 180- to 220-kD protein. The rDEP-1 gene is located on human chromosome 11 (region p11.2) and on mouse chromosome 2 (region 2E). The cDNA sequence predicts a transmembrane protein consisting of a single phosphatase catalytic domain in the intracellular region, a single transmembrane domain, and eight fibronectin type III repeats in the extracellular region (GenBank accession number U40790). In situ hybridization analysis demonstrates that rDEP-1 is widely expressed in vivo but that expression is highest in cells that form epithelioid monolayers. In cultured cells with epitheliod morphology, including endothelial cells and newborn smooth muscle cells, but not in fibroblast-like cells, rDEP-1 transcript levels are dramatically upregulated as population density increases. In vivo, quiescent endothelial cells in normal arteries express relatively high levels of rDEP-1. During repair of vascular injury, expression of rDEP-1 is downregulated in migrating and proliferating endothelial cells. In vivo, rDEP-1 transcript levels are present in very high levels in megakaryocytes, and circulating plates have high levels of the rDEP-1 protein. In vitro, initiation of differentiation of the human megakaryoblastic cell line CHRF-288-11 with phorbol 12-myristate 13-acetate leads to a very strong upregulation of rDEP-1 transcripts. The deduced structure and the regulation of expression of rDEP-1 suggest that it may play a role in adhesion and/or signaling events involving cell-cell and cell-matrix contact.
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Affiliation(s)
- L G Borges
- Department of Pathology, University of Washington, Seattle 98195-7470, USA
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Mishan'kin MB, Aseeva LE, Goncharov EK, Mishan'kin BN. The murine toxin ofYersinia pestis: Some enzymatic activities. Bull Exp Biol Med 1995. [DOI: 10.1007/bf02445576] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Abstract
The platelet population in man and rat can be divided into two classes of about equal size based on the presence/absence of a p-nitrophenylphosphatase, which probably is a phosphotyrosine phosphatase (PTPase). Phosphorylation of tyrosines on several platelet proteins is implicated in platelet activation, and I carried out in vitro and in vivo experiments on rats to determine whether PTPase positive and negative platelets differed in their reaction time. I used adhesion to collagen in vitro and in vivo (longitudinal slits in aorta and vena portae) and platelet aggregates in clots formed in vivo. I present evidence that PTPase negative platelets react the fastest, most conspicuously seen in the arterial bleeding under high flow conditions, where the first platelets to respond and adhere are predominantly PTPase negative.
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Affiliation(s)
- O Behnke
- Department of Medical Anatomy, Panum Institute, University of Copenhagen, Denmark
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Luber K, Siess W. Integrin-dependent protein dephosphorylation on tyrosine induced by activation of the thrombin receptor in human platelets. Cell Signal 1994; 6:279-84. [PMID: 7917785 DOI: 10.1016/0898-6568(94)90032-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Activation of human platelets by thrombin or a thrombin receptor-activating peptide (TRAP) resulted in a decrease in tyrosine phosphorylation of two proteins, P38 and P140. Preincubation of platelets with the tyrosine phosphatase inhibitor orthovanadate prevented the tyrosine dephosphorylation of P38 and P140, and reduced platelet aggregation induced by thrombin receptor activation. When platelets were stimulated under conditions that precluded the activation of glycoprotein IIb/IIIa (dissociation of the complex by EGTA at 37 degrees C) or the binding of fibrinogen (preincubation of platelets with RGDS), tyrosine dephosphorylation of P38 and P140 was not observed. The results indicate that protein tyrosine phosphatase stimulation (a) occurs during platelet activation induced by a physiological stimulus, (b) is a positive regulatory signal for platelet aggregation and (c) is dependent on the activation of the integrin alpha IIb beta 3.
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Affiliation(s)
- K Luber
- Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten b.d. Universität München, Germany
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Liebenhoff U, Brockmeier D, Presek P. Substrate affinity of the protein tyrosine kinase pp60c-src is increased on thrombin stimulation of human platelets. Biochem J 1993; 295 ( Pt 1):41-8. [PMID: 7692843 PMCID: PMC1134817 DOI: 10.1042/bj2950041] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Human blood platelets contain high levels of non-receptor protein tyrosine kinases of the Src family, particularly pp60c-src, suggesting an important role for these enzymes in platelet physiology. Indeed, in response to various agonists of platelet function, a number of proteins become phosphorylated at tyrosine residues. However, no enzymic activation of an Src-related tyrosine kinase has yet been shown in platelets. In searching for the kinase(s) responsible, we found that all agonists tested that directly or indirectly activate protein kinase C in platelets (phorbol 12-myristate, 13-acetate, thrombin, vasopressin, collagen, calcium ionophore A23187) increased the overall activity of pp60c-src determined by IgG phosphorylation in an immunocomplex assay in the presence of low ATP concentrations. On the other hand, elevation of cyclic AMP directly by forskolin or indirectly by prostaglandin E1, or elevation of cyclic GMP by sodium nitroprusside did not significantly affect the activity of the enzyme. To substantiate the differences in enzyme activity, we determined Km and Vmax, values of pp60c-src from resting and thrombin-stimulated platelets. Thrombin treatment increased substrate affinity of pp60c-src as indicated by a 2- to 3-fold decrease in the Km values for ATP and the exogenous protein substrate casein. Vmax. values were only slightly altered under the assay conditions used. To further rule out modifications of pp60c-src in phosphorylation as a probable cause of the changed substrate affinity, we analysed tryptic phosphopeptides of immunoprecipitated, 32P-labelled pp60c-src of unstimulated and stimulated platelets. The platelet agonists listed above induced an increase in pp60c-src phosphorylation at Ser-12, which is the amino acid phosphorylated by protein kinase C. Surprisingly, we found that elevation of cyclic AMP did not affect 32P labelling of pp60c-src. On the basis of our data, we suggest that phosphorylation at Ser-12 might be one of the signal-triggering events that cause the increase in substrate affinity of pp60c-src.
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Affiliation(s)
- U Liebenhoff
- Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität, Giessen, Federal Republic of Germany
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18
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Murphy CT, Kellie S, Westwick J. Tyrosine-kinase activity in rabbit platelets stimulated with platelet-activating factor. The effect of inhibiting tyrosine kinase with genistein on platelet-signal-molecule elevation and functional responses. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 216:639-51. [PMID: 7690703 DOI: 10.1111/j.1432-1033.1993.tb18184.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The temporal relationship of tyrosine phosphorylation of proteins in platelet-activating-factor-(PAF)-stimulated rabbit platelets was characterised by Western blotting using a monoclonal anti-phosphotyrosine antibody, demonstrated to be specific for detecting only tyrosine phosphorylated proteins. In addition, the protein tyrosine kinase (PTKase) inhibitor genistein, was used to investigate the role of endogenously activated PTKase(s) in the regulation of receptor-stimulated changes in both signal molecule production and in platelet functional responses. Several tyrosine phosphorylated protein bands (52-62 kDa) were observed in unstimulated platelets, however, within 5 s of PAF stimulation, two further groups of tyrosine phosphorylated protein bands were observed (35-45 kDa and 66-90 kDa) and within 30 s of PAF stimulation a further group was detected (90-150 kDa). Under conditions where intracellular Ca2+ was chelated with acetoxymethyl 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetate (BAPTA-AM) and extracellular Ca2+ was chelated with EGTA, the number of tyrosine-phosphorylated bands was greatly reduced. Tyrosine phosphorylation of the proteins induced by PAF stimulation were differentially inhibited by treatment with genistein. Genistein inhibited PAF-induced elevation of the signal molecule inositol 1,4,5-trisphosphate and also inhibited both mobilization of Ca2+ and the influx of Ca2+ through the plasma membrane. These results suggest a role for endogenously activated PTKase(s) in the early stages of signal transduction in PAF-stimulated platelets. Moreover, inhibition of genistein-sensitive PTKase(s) also caused an inhibition of PAF-induced thromboxane B2 generation, dense-granule release and platelet aggregation, indicating a role for PTKase(s) in the regulation of platelet functional responses. Platelets stimulated with alpha-thrombin, ionomycin and 12-O-tetradecanylphorbol 13-acetate gave a similar pattern of phosphorylated proteins to PAF-stimulated platelets, however, whereas genistein inhibited protein phosphorylation, it had no significant effect on functional responses in platelets stimulated with these agents, suggesting that an alternative signalling pathway exists.
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Affiliation(s)
- C T Murphy
- School of Pharmacy and Pharmacology, University of Bath, Avon, England
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Affiliation(s)
- A Dhar
- Department of Pharmacology, University of Missouri School of Medicine, Columbia
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Shattil SJ, Brugge JS. Protein tyrosine phosphorylation and the adhesive functions of platelets. Curr Opin Cell Biol 1991; 3:869-79. [PMID: 1931088 DOI: 10.1016/0955-0674(91)90062-4] [Citation(s) in RCA: 125] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The intracellular signalling pathways that mediate changes in cell behavior induced by extracellular matrix and cell adhesion molecules are poorly understood. Studies on the regulation of tyrosine phosphorylation in platelets indicate that cell-to-cell aggregation mediated by fibrinogen binding to its integrin-family receptor, GP IIb-IIIa, and events regulated by the putative adhesion receptor, GP IV (CD36), involve tyrosine phosphorylation. Thus, tyrosine phosphorylation is implicated in cellular events crucial for hemostasis. It may also be involved in signaling mediated by integrin receptors in other cell types.
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Affiliation(s)
- S J Shattil
- University of Pennsylvania School of Medicine, Philadelphia
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