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Singh PK, Dangelmaier CA, Vari HR, Tsygankov AY, Kunapuli SP. Biochemical characterization of spleen tyrosine kinase (SYK) isoforms in platelets. Platelets 2023; 34:2249549. [PMID: 37661351 PMCID: PMC10502920 DOI: 10.1080/09537104.2023.2249549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 07/12/2023] [Accepted: 08/14/2023] [Indexed: 09/05/2023]
Abstract
Alternate splicing is among the regulatory mechanisms imparting functional diversity in proteins. Studying protein isoforms generated through alternative splicing is therefore critical for understanding protein functions in many biological systems. Spleen tyrosine kinase (Syk) plays an essential role in ITAM/hemITAM signaling in many cell types, including platelets. However, the spectrum of Syk isoforms expressed in platelets has not been characterized. Syk has been shown to have a full-length long isoform SykL and a shorter SykS lacking 23 amino acid residues within its interdomain B. Furthermore, putative isoforms lacking another 23 amino acid-long sequence or a combination of the two deletions have been postulated to exist. In this report, we demonstrate that mouse platelets express full-length SykL and the previously described shorter isoform SykS, but lack other shorter isoforms, whereas human platelets express predominantly SykL. These results both indicate a possible role of alternative Syk splicing in the regulation of receptor signaling in mouse platelets and a difference between signaling regulation in mouse and human platelets.
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Affiliation(s)
- Pankaj Kumar Singh
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Carol A. Dangelmaier
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Hymavathi Reddy Vari
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Alexander Y. Tsygankov
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Satya P. Kunapuli
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
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Dangelmaier CA, Patchin M, Vajipayajula DN, Vari HR, Singh PK, Wright MN, Kostyak JC, Tsygankov AY, Kunapuli SP. Phosphorylation of spleen tyrosine kinase at Y346 negatively regulates ITAM-mediated signaling and function in platelets. J Biol Chem 2023; 299:104865. [PMID: 37268160 PMCID: PMC10320515 DOI: 10.1016/j.jbc.2023.104865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 04/29/2023] [Accepted: 05/02/2023] [Indexed: 06/04/2023] Open
Abstract
Spleen tyrosine kinase (Syk) is expressed in a variety of hemopoietic cells. Upon phosphorylation of the platelet immunoreceptor-based activation motif of the glycoprotein VI (GPVI)/Fc receptor gamma chain collagen receptor, both the tyrosine phosphorylation and activity of Syk are increased leading to downstream signaling events. Although it has been established that the activity of Syk is regulated by tyrosine phosphorylation, the specific roles of individual phosphorylation sites remain to be elucidated. We observed that Syk Y346 in mouse platelets was still phosphorylated when GPVI-induced Syk activity was inhibited. We then generated Syk Y346F mice and analyzed the effect this mutation exerts on platelet responses. Syk Y346F mice bred normally, and their blood cell count was unaltered. We did observe potentiation of GPVI-induced platelet aggregation and ATP secretion as well as increased phosphorylation of other tyrosines on Syk in the Syk Y346F mouse platelets when compared to WT littermates. This phenotype was specific for GPVI-dependent activation, since it was not seen when AYPGKF, a PAR4 agonist, or 2-MeSADP, a purinergic receptor agonist, was used to activate platelets. Despite a clear effect of Syk Y346F on GPVI-mediated signaling and cellular responses, there was no effect of this mutation on hemostasis as measured by tail-bleeding times, although the time to thrombus formation determined using the ferric chloride injury model was reduced. Thus, our results indicate a significant effect of Syk Y346F on platelet activation and responses in vitro and reveal its complex nature manifesting itself by the diversified translation of platelet activation into physiological responses.
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Affiliation(s)
- Carol A Dangelmaier
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Margaret Patchin
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Dhruv N Vajipayajula
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Hymavathi Reddy Vari
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Pankaj K Singh
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Monica N Wright
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - John C Kostyak
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Alexander Y Tsygankov
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Satya P Kunapuli
- Department of Cardiovascular Sciences, Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA.
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Kunapuli SP, Tsygankov AY. TULA-Family Regulators of Platelet Activation. Int J Mol Sci 2022; 23:ijms232314910. [PMID: 36499237 PMCID: PMC9736690 DOI: 10.3390/ijms232314910] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/17/2022] [Accepted: 11/21/2022] [Indexed: 11/30/2022] Open
Abstract
The two members of the UBASH3/TULA/STS-protein family have been shown to critically regulate cellular processes in multiple biological systems. The regulatory function of TULA-2 (also known as UBASH3B or STS-1) in platelets is one of the best examples of the involvement of UBASH3/TULA/STS proteins in cellular regulation. TULA-2 negatively regulates platelet signaling mediated by ITAM- and hemITAM-containing membrane receptors that are dependent on the protein tyrosine kinase Syk, which currently represents the best-known dephosphorylation target of TULA-2. The biological responses of platelets to collagen and other physiological agonists are significantly downregulated as a result. The protein structure, enzymatic activity and regulatory functions of UBASH3/TULA/STS proteins in the context of platelet responses and their regulation are discussed in this review.
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Makhoul S, Trabold K, Gambaryan S, Tenzer S, Pillitteri D, Walter U, Jurk K. cAMP- and cGMP-elevating agents inhibit GPIbα-mediated aggregation but not GPIbα-stimulated Syk activation in human platelets. Cell Commun Signal 2019; 17:122. [PMID: 31519182 PMCID: PMC6743169 DOI: 10.1186/s12964-019-0428-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 08/29/2019] [Indexed: 12/29/2022] Open
Abstract
Background The glycoprotein (GP) Ib-IX-V complex is a unique platelet plasma membrane receptor, which is essential for platelet adhesion and thrombus formation. GPIbα, part of the GPIb-IX-V complex, has several physiological ligands such as von Willebrand factor (vWF), thrombospondin and distinct coagulation factors, which trigger platelet activation. Despite having an important role, intracellular GPIb-IX-V signaling and its regulation by other pathways are not well defined. Our aim was to establish the intracellular signaling response of selective GPIbα activation in human platelets, in particular the role of the tyrosine kinase Syk and its regulation by cAMP/PKA and cGMP/PKG pathways, respectively. We addressed this using echicetin beads (EB), which selectively bind to GPIbα and induce platelet aggregation. Methods Purified echicetin from snake Echis carinatus venom was validated by mass spectrometry. Washed human platelets were incubated with EB, in the presence or absence of echicetin monomers (EM), Src family kinase (SFK) inhibitors, Syk inhibitors and the cAMP- and cGMP-elevating agents iloprost and riociguat, respectively. Platelet aggregation was analyzed by light transmission aggregometry, protein phosphorylation by immunoblotting. Intracellular messengers inositolmonophosphate (InsP1) and Ca2+i were measured by ELISA and Fluo-3 AM/FACS, respectively. Results EB-induced platelet aggregation was dependent on integrin αIIbβ3 and secondary mediators ADP and TxA2, and was antagonized by EM. EB stimulated Syk tyrosine phosphorylation at Y352, which was SFK-dependent and Syk-independent, whereas Y525/526 phosphorylation was SFK-dependent and partially Syk-dependent. Furthermore, phosphorylation of both Syk Y352 and Y525/526 was completely integrin αIIbβ3-independent but, in the case of Y525/526, was partially ADP/TxA2-dependent. Syk activation, observed as Y352/ Y525/Y526 phosphorylation, led to the phosphorylation of direct substrates (LAT Y191, PLCγ2 Y759) and additional targets (Akt S473). PKA/PKG pathways inhibited EB-induced platelet aggregation and Akt phosphorylation but, surprisingly, enhanced Syk and LAT/PLCγ2 tyrosine phosphorylation. A similar PKA/PKG effect was confirmed with convulxin−/GPVI-stimulated platelets. EB-induced InsP1 accumulation/InsP3 production and Ca2+-release were Syk-dependent, but only partially inhibited by PKA/PKG pathways. Conclusion EB and EM are specific agonists and antagonists, respectively, of GPIbα-mediated Syk activation leading to platelet aggregation. The cAMP/PKA and cGMP/PKG pathways do not inhibit but enhance GPIbα−/GPVI-initiated, SFK-dependent Syk activation, but strongly inhibit further downstream responses including aggregation. These data establish an important intracellular regulatory network induced by GPIbα. Graphical abstract ![]()
Electronic supplementary material The online version of this article (10.1186/s12964-019-0428-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stephanie Makhoul
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Katharina Trabold
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Stepan Gambaryan
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, Mainz, Germany.,Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Stefan Tenzer
- Core Facility for Mass Spectrometry, Institute for Immunology, University Medical Center Mainz, Mainz, Germany
| | | | - Ulrich Walter
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Kerstin Jurk
- Center for Thrombosis and Hemostasis (CTH), University Medical Center Mainz of the Johannes Gutenberg University Mainz, Mainz, Germany.
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Misra A, Prakash P, Aggarwal H, Dhankani P, Kumar S, Pandey CP, Pugh N, Bihan D, Barthwal MK, Farndale RW, Dikshit DK, Dikshit M. Anti-thrombotic efficacy of S007-867: Pre-clinical evaluation in experimental models of thrombosis in vivo and in vitro. Biochem Pharmacol 2018; 148:288-297. [DOI: 10.1016/j.bcp.2018.01.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Accepted: 01/03/2018] [Indexed: 12/30/2022]
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6
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Getz TM, Manne B, Buitrago L, Mao Y, Kunapuli SP. Dextran sulphate induces fibrinogen receptor activation through a novel Syk-independent PI-3 kinase-mediated tyrosine kinase pathway in platelets. Thromb Haemost 2017; 109:1131-40. [DOI: 10.1160/th12-09-0645] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 03/01/2013] [Indexed: 12/14/2022]
Abstract
SummaryIn our attempt to find a physiological agonist that activates PAR3 receptors, we screened several coagulation proteases using PAR4 null platelets. We observed that FXIIa and heat inactivated FXIIa, but not FXII, caused platelet aggregation. We have identified a contaminant activating factor in FXIIa preparation as dextran sulfate (DxS), which caused aggregation of both human and mouse platelets. DxS-induced platelet aggregation was unaffected by YM254890, a Gq inhibitor, but abolished by pan-Src family kinase (SFK) inhibitor PP2, suggesting a role for SFKs in this pathway. However, DxS-induced platelet aggregation was unaffected in FcRγ-chain null murine platelets, ruling out the possibility of glycoprotein VI-mediated events. More interesting, OXSI-2 and Go6976, two structurally unrelated inhibitors shown to affect Syk, had only a partial effect on DxS-induced PAC-1 binding. DxS-induced platelet aggregation and intracellular calcium increases were abolished by the pan PI-3 kinase inhibitor LY294002, or an isoform-specific PI-3 kinase β inhibitor TGX-221. Pretreatment of platelets with Syk inhibitors or ADP receptor antagonists had little effect on Akt phosphorylation following DxS stimulation. These results, for the first time, establish a novel tyrosine kinase pathway in platelets that causes fibrinogen receptor activation in a PI-3 kinase-dependent manner without a crucial role for Syk.
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7
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Liu D, Mamorska-Dyga A. Syk inhibitors in clinical development for hematological malignancies. J Hematol Oncol 2017; 10:145. [PMID: 28754125 PMCID: PMC5534090 DOI: 10.1186/s13045-017-0512-1] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Accepted: 07/20/2017] [Indexed: 01/03/2023] Open
Abstract
Spleen tyrosine kinase (Syk) is a cytosolic non-receptor protein tyrosine kinase (PTK) and is mainly expressed in hematopoietic cells. Syk was recognized as a critical element in the B-cell receptor signaling pathway. Syk is also a key component in signal transduction from other immune receptors like Fc receptors and adhesion receptors. Several oral Syk inhibitors including fostamatinib (R788), entospletinib (GS-9973), cerdulatinib (PRT062070), and TAK-659 are being assessed in clinical trials. The second generation compound, entospletinib, showed promising results in clinical trials against B-cell malignancies, mainly chronic lymphoid leukemia. Syk inhibitors are being evaluated in combination regimens in multiple malignancies.
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Affiliation(s)
- Delong Liu
- Department of Oncology, The first Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
| | - Aleksandra Mamorska-Dyga
- Department of Medicine, New York Medical College and Westchester Medical Center, Valhalla, NY, 10595, USA
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8
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Manne BK, Badolia R, Dangelmaier C, Eble JA, Ellmeier W, Kahn M, Kunapuli SP. Distinct pathways regulate Syk protein activation downstream of immune tyrosine activation motif (ITAM) and hemITAM receptors in platelets. J Biol Chem 2015; 290:11557-68. [PMID: 25767114 DOI: 10.1074/jbc.m114.629527] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Indexed: 11/06/2022] Open
Abstract
Tyrosine kinase pathways are known to play an important role in the activation of platelets. In particular, the GPVI and CLEC-2 receptors are known to activate Syk upon tyrosine phosphorylation of an immune tyrosine activation motif (ITAM) and hemITAM, respectively. However, unlike GPVI, the CLEC-2 receptor contains only one tyrosine motif in the intracellular domain. The mechanisms by which this receptor activates Syk are not completely understood. In this study, we identified a novel signaling mechanism in CLEC-2-mediated Syk activation. CLEC-2-mediated, but not GPVI-mediated, platelet activation and Syk phosphorylation were abolished by inhibition of PI3K, which demonstrates that PI3K regulates Syk downstream of CLEC-2. Ibrutinib, a Tec family kinase inhibitor, also completely abolished CLEC-2-mediated aggregation and Syk phosphorylation in human and murine platelets. Furthermore, embryos lacking both Btk and Tec exhibited cutaneous edema associated with blood-filled vessels in a typical lymphatic pattern similar to CLEC-2 or Syk-deficient embryos. Thus, our data show, for the first time, that PI3K and Tec family kinases play a crucial role in the regulation of platelet activation and Syk phosphorylation downstream of the CLEC-2 receptor.
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Affiliation(s)
- Bhanu Kanth Manne
- From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Rachit Badolia
- From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Carol Dangelmaier
- From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Johannes A Eble
- the Institute for Physiological Chemistry and Pathobiochemistry, University of Münster, 48149 Münster, Germany
| | - Wilfried Ellmeier
- the Division of Immunobiology, Institution of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, A-1090 Vienna, Austria, and
| | - Mark Kahn
- the Department of Medicine and Division of Cardiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-5159
| | - Satya P Kunapuli
- From the Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140,
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9
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Manne BK, Getz TM, Hughes CE, Alshehri O, Dangelmaier C, Naik UP, Watson SP, Kunapuli SP. Fucoidan is a novel platelet agonist for the C-type lectin-like receptor 2 (CLEC-2). J Biol Chem 2013; 288:7717-7726. [PMID: 23341451 DOI: 10.1074/jbc.m112.424473] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fucoidan, a sulfated polysaccharide from Fucus vesiculosus, decreases bleeding time and clotting time in hemophilia, possibly through inhibition of tissue factor pathway inhibitor. However, its effect on platelets and the receptor by which fucoidan induces cellular processes has not been elucidated. In this study, we demonstrate that fucoidan induces platelet activation in a concentration-dependent manner. Fucoidan-induced platelet activation was completely abolished by the pan-Src family kinase (SFK) inhibitor, PP2, or when Syk is inhibited. PP2 abolished phosphorylations of Syk and Phospholipase C-γ2. Fucoidan-induced platelet activation had a lag phase, which is reminiscent of platelet activation by collagen and CLEC-2 receptor agonists. Platelet activation by fucoidan was only slightly inhibited in FcRγ-chain null mice, indicating that fucoidan was not acting primarily through GPVI receptor. On the other hand, fucoidan-induced platelet activation was inhibited in platelet-specific CLEC-2 knock-out murine platelets revealing CLEC-2 as a physiological target of fucoidan. Thus, our data show fucoidan as a novel CLEC-2 receptor agonist that activates platelets through a SFK-dependent signaling pathway. Furthermore, the efficacy of fucoidan in hemophilia raises the possibility that decreased bleeding times could be achieved through activation of platelets.
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Affiliation(s)
- Bhanu Kanth Manne
- Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Todd M Getz
- Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Craig E Hughes
- Centre for Cardiovascular Sciences, Institute for Biomedical Research, The College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Osama Alshehri
- Centre for Cardiovascular Sciences, Institute for Biomedical Research, The College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Carol Dangelmaier
- Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Ulhas P Naik
- Cardiovascular Research Institute, University of Delaware, Newark, Delaware 19716
| | - Steve P Watson
- Centre for Cardiovascular Sciences, Institute for Biomedical Research, The College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Satya P Kunapuli
- Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
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10
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Bhavaraju K, Georgakis A, Jin J, Gartner TK, Tomiyama Y, Nurden A, Nurden P, Kunapuli SP. Antagonism of P2Y₁₂ reduces physiological thromboxane levels. Platelets 2011; 21:604-9. [PMID: 21067313 DOI: 10.3109/09537104.2010.511684] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Antiplatelet therapy for the management of patients with cardiovascular risks often includes a combination therapy of aspirin and clopidogrel, acting through inhibition of thromboxane generation and blockade of G(i)-coupled P2Y₁₂ receptor, respectively. We hypothesized that ADP acting through P2Y₁₂ regulates physiological thromboxane levels. The serum thromboxane levels in mice (n = 3) dosed with clopidogrel and prasugrel were decreased by 83.1 ± 5.3% and 94.26 ± 1.75% respectively compared to untreated mice. Pre-treatment of human blood (n = 3) ex vivo with active metabolites of clopidogrel or prasugrel led to a reduction in thromboxane levels to 16.3 ± 3.2% and 4.9 ± 0.8% respectively, compared to untreated human serum. We also evaluated serum thromboxane levels in P2Y receptor null mice (n = 4). Whereas serum thromboxane levels in P2Y₁ null mice were similar to those in wild type littermates, those in the P2Y₁₂ null mice were inhibited by 83.15 ± 3.8%. Finally, in a pilot study, serum thromboxane levels were reduced by 76.05 ± 8.41% in healthy human volunteers (n = 6) upon dosing with clopidogrel, compared to the levels before dosing. In conclusion, P2Y₁₂ antagonism alone can decrease physiological thromboxane levels. Thus, this study could pave way the for newer/modified treatment regimens for the management of patients with thrombotic complications who are allergic or non-responsive to aspirin.
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Affiliation(s)
- Kamala Bhavaraju
- Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA
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11
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G(12/13) signaling pathways substitute for integrin αIIbβ3-signaling for thromboxane generation in platelets. PLoS One 2011; 6:e16586. [PMID: 21347357 PMCID: PMC3037367 DOI: 10.1371/journal.pone.0016586] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 12/21/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND We have previously shown that ADP-induced TXA(2) generation requires signaling from αIIbβ3 integrin in platelets. Here we observed that, unlike ADP, protease-activated receptor (PAR)-mediated TXA(2) generation occurs independently of αIIbβ3. PAR agonists, but not ADP, activate G(12/13) signaling pathways. Hence, we evaluated the role of these pathways in TXA(2) generation. PRINCIPAL FINDINGS Inhibition of ADP-induced thromboxane generation by fibrinogen receptor antagonist SC57101 was rescued by co-stimulation of G(12/13) pathways with YFLLRNP. This observation suggested an existence of a common signaling effector downstream of integrins and G(12/13) pathways. Hence, we evaluated role of three potential tyrosine kinases; c-Src, Syk and FAK (Focal Adhesion Kinase) that are known to be activated by integrins. c-Src and Syk kinase did not play a role in ADP-induced functional responses in platelets. Selective activation of G(12/13) pathways resulted in the activation of FAK, in the absence of integrin signaling. Interestingly, αIIbβ3-mediated FAK activation occurred in a Src family kinase (SFK)-independent manner whereas G(12/13) pathway caused FAK activation in a SFK and RhoA-dependent manner. A FAK selective inhibitor TAE-226, blocked TXA(2) generation. However, in comparison to WT mice, Pf4-Cre/Fak-Floxed mice did not show any difference in platelet TXA(2) generation. CONCLUSIONS Therefore, we conclude that differential activation of FAK occurs downstream of Integrins and G(12/13) pathways. However, the common effector molecule, possibly a tyrosine kinase downstream of integrins and G(12/13) pathways contributing to TXA(2) generation in platelets remains elusive.
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12
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Chen X, Ren L, Kim S, Carpino N, Daniel JL, Kunapuli SP, Tsygankov AY, Pei D. Determination of the substrate specificity of protein-tyrosine phosphatase TULA-2 and identification of Syk as a TULA-2 substrate. J Biol Chem 2010; 285:31268-76. [PMID: 20670933 PMCID: PMC2951201 DOI: 10.1074/jbc.m110.114181] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2010] [Revised: 07/28/2010] [Indexed: 11/06/2022] Open
Abstract
TULA-1 (UBASH3A/STS-2) and TULA-2 (p70/STS-1) represent a novel class of protein-tyrosine phosphatases. Previous studies suggest that TULA-2 is sequence-selective toward phosphotyrosyl (Tyr(P)) peptides. In this work the substrate specificity of TULA-1 and -2 was systematically evaluated by screening a combinatorial Tyr(P) peptide library. Although TULA-1 showed no detectable activity toward any of the Tyr(P) peptides in the library, TULA-2 recognizes two distinct classes of Tyr(P) substrates. On the N-terminal side of Tyr(P), the class I substrates contain a proline at the Tyr(P)-1 position, a hydrophilic residue at the Tyr(P)-2 position, and aromatic hydrophobic residues at positions Tyr(P)-3 and beyond. The class II substrates typically contain two or more acidic residues, especially at Tyr(P)-1 to Tyr(P)-3 positions, and aromatic hydrophobic residues at other positions. At the C-terminal side of Tyr(P), TULA-2 generally prefers acidic and aromatic residues. The library screening results were confirmed by kinetic analysis of representative peptides selected from the library as well as Tyr(P) peptides derived from various Tyr(P) proteins. TULA-2 is highly active toward peptides corresponding to the Tyr(P)-323 and Tyr(P)-352 sites of Syk, and the Tyr(P)-397 site of focal adhesion kinase and has lower activity toward other Tyr(P) sites in these proteins. In glycoprotein VI-stimulated platelets, knock-out of the TULA-2 gene significantly increased the phosphorylation level of Syk at Tyr-323 and Tyr-352 sites and to a lesser degree at the Tyr-525/526 sites. These results suggest that Syk is a bona fide TULA-2 substrate in platelets.
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Affiliation(s)
- Xianwen Chen
- From the Department of Chemistry and Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210
| | - Lige Ren
- From the Department of Chemistry and Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210
| | | | - Nicholas Carpino
- the Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794, and
| | - James L. Daniel
- Pharmacology
- the Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Satya P. Kunapuli
- Physiology, and
- the Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Alexander Y. Tsygankov
- the Departments of Microbiology and Immunology
- the Fels Institute for Cancer Research and Molecular Biology, and
- the Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140
| | - Dehua Pei
- From the Department of Chemistry and Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210
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13
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Ghosh D, Tsokos GC. Spleen tyrosine kinase: an Src family of non-receptor kinase has multiple functions and represents a valuable therapeutic target in the treatment of autoimmune and inflammatory diseases. Autoimmunity 2010; 43:48-55. [PMID: 20001666 DOI: 10.3109/08916930903374717] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Spleen tyrosine kinase (Syk) is involved in the development and function of B and T cells, the Fc receptor-mediated degranulation of basophils and mast cells. Recent work has assigned important roles for Syk in the aberrant function of T cells in patients with systemic lupus erythematosus (SLE), osteoclasts, and urate crystal-induced neutrophil stimulation. Preclinical and early clinical studies have urged Syk inhibition for the treatment of patients with rheumatoid arthritis, whereas ex vivo experiments and preclinical studies point to a therapeutic potential of Syk inhibition in patients with SLE and crystal-induced arthritides.
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Affiliation(s)
- Debjani Ghosh
- Division of Rheumatology, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA 02115, USA
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Lee YG, Chain BM, Cho JY. Distinct role of spleen tyrosine kinase in the early phosphorylation of inhibitor of κBα via activation of the phosphoinositide-3-kinase and Akt pathways. Int J Biochem Cell Biol 2009; 41:811-21. [DOI: 10.1016/j.biocel.2008.08.011] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 07/17/2008] [Accepted: 08/11/2008] [Indexed: 10/21/2022]
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Wälchli S, Aasheim HC, Skånland SS, Spilsberg B, Torgersen ML, Rosendal KR, Sandvig K. Characterization of clathrin and Syk interaction upon Shiga toxin binding. Cell Signal 2009; 21:1161-8. [PMID: 19289168 DOI: 10.1016/j.cellsig.2009.03.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 03/05/2009] [Indexed: 11/19/2022]
Abstract
Shiga toxin (Stx) is a bacterial toxin that binds to its receptor Gb3 at the plasma membrane. It is taken up by endocytosis and transported retrogradely via the Golgi apparatus to the endoplasmic reticulum. The toxin is then translocated to the cytosol where it exerts its toxic effect. We have previously shown that phosphorylation of clathrin heavy chain (CHC) is an early event following Stx binding to HeLa cells, and that this requires the activity of the tyrosine kinase Syk. Here, we have investigated this event in more detail in the B lymphoid cell line Ramos, which expresses high endogenous levels of both Syk and Gb3. We report that efficient endocytosis of Stx in Ramos cells requires Syk activity and that Syk is recruited to the uptake site of Stx. Furthermore, in response to Stx treatment, CHC and Syk were rapidly phosphorylated in a Src family kinase dependent manner at Y1477 and Y352, respectively. We show that these phosphorylated residues act as binding sites for the direct interaction between Syk and CHC. Interestingly, Syk-CHC complex formation could be induced by both Stx and B cell receptor stimulation.
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Affiliation(s)
- Sébastien Wälchli
- Department of Biochemistry, Institute for Cancer Research, Faculty Division: The Norwegian Radium Hospital, Montebello, Oslo, Norway.
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Chari R, Getz T, Nagy B, Bhavaraju K, Mao Y, Bynagari YS, Murugappan S, Nakayama K, Kunapuli SP. Protein kinase C[delta] differentially regulates platelet functional responses. Arterioscler Thromb Vasc Biol 2009; 29:699-705. [PMID: 19213940 DOI: 10.1161/atvbaha.109.184010] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Protein Kinase C delta (PKCdelta) is expressed in platelets and activated downstream of protease-activated receptors (PAR)s and glycoprotein VI (GPVI) receptors. The purpose of this study was to investigate the role of PKCdelta in platelets. METHODS AND RESULTS We evaluated the role of PKCdelta in platelets using two approaches--pharmacological and molecular genetic approach. In human platelets pretreated with isoform selective antagonistic RACK peptide (delta V1-1)TAT, and in the murine platelets lacking PKCdelta, PAR4-mediated dense granule secretion was inhibited, whereas GPVI-mediated dense granule secretion was potentiated. These effects were statistically significant in the absence and presence of thromboxane A2 (TXA2). Furthermore, TXA2 generation was differentially regulated by PKCdelta. However, PKCdelta had a small effect on platelet P-selectin expression. Calcium- and PKC-dependent pathways independently activate fibrinogen receptor in platelets. When calcium pathways are blocked by dimethyl-BAPTA, AYPGKF-induced aggregation in PKCdelta null mouse platelets and in human platelets pretreated with (delta V1-1)TAT, was inhibited. In a FeCl3-induced injury in vivo thrombosis model, PKCdelta-/- mice occluded similar to their wild-type littermates. CONCLUSIONS Hence, we conclude that PKCdelta differentially regulates platelet functional responses such as dense granule secretion and TXA2 generation downstream of PARs and GPVI receptors, but PKCdelta deficiency does not affect the thrombus formation in vivo.
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Affiliation(s)
- Ramya Chari
- Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA
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Paoluzzi L, Kitagawa Y, Kalac M, Zain J, O'Connor OA. New drugs for the treatment of lymphoma. Hematol Oncol Clin North Am 2008; 22:1007-35, x. [PMID: 18954749 DOI: 10.1016/j.hoc.2008.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Historically, most drugs developed for treatment of leukemias, lymphomas, and myeloma had already been studied in the solid tumor setting. Nearly 10 years ago, chronic myelogenous leukemia (CML) forever changed this paradigm. Imatinib showed that it was possible to nullify the pathognomic genetic lesion in a hematologic malignancy. Since the approval of imatinib for CML, a host of new drugs active in blood cancers have emerged. This article highlights some areas of innovative drug development in lymphoma where possible; it emphasizes the biologic basis for the approach, linking this essential biology to the biochemical pharmacology. The article focuses on the many new targets including Syk, Bcl-2, CD-40, and the phosphoinositide-3 kinase/AKT/mammalian target of rapamycin pathway.
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Affiliation(s)
- Luca Paoluzzi
- Herbert Irving Comprehensive Cancer Center, Columbia University, 1130 St. Nicholas Avenue, Room 216, New York, NY 10032, USA
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