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Dangelmaier C, Vari HR, Vajipayajula DN, Elzoheiry M, Wright M, Iyer A, Tsygankov AY, Kunapuli SP. Phosphorylation of (Ser 291) in the linker insert of Syk negatively regulates ITAM signaling in platelets. Platelets 2024; 35:2369766. [PMID: 38904212 DOI: 10.1080/09537104.2024.2369766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
Receptor-induced tyrosine phosphorylation of spleen tyrosine kinase (Syk) has been studied extensively in hematopoietic cells. Metabolic mapping and high-resolution mass spectrometry, however, indicate that one of the most frequently detected phosphorylation sites encompassed S297 (S291 in mice) located within the linker B region of Syk. It has been reported that Protein kinase C (PKC) phosphorylates Syk S297, thus influencing Syk activity. However, conflicting studies suggest that this phosphorylation enhances as well as reduces Syk activity. To clarify the function of this site, we generated Syk S291A knock-in mice. We used platelets as a model system as they possess Glycoprotein VI (GPVI), a receptor containing an immunoreceptor tyrosine-based activation motif (ITAM) which transduces signals through Syk. Our analysis of the homozygous mice indicated that the knock-in platelets express only one isoform of Syk, while the wild-type expresses two isoforms at 69 and 66 kDa. When the GPVI receptor was activated with collagen-related peptide (CRP), we observed an increase in functional responses and phosphorylations in Syk S291A platelets. This potentiation did not occur with AYPGKF or 2-MeSADP, although they also activate PKC isoforms. Although there was potentiation of platelet functional responses, there was no difference in tail bleeding times. However, the time to occlusion in the FeCl3 injury model was enhanced. These data indicate that the effects of Syk S291 phosphorylation represent a significant outcome on platelet activation and signaling in vitro but also reveals its multifaceted nature demonstrated by the differential effects on physiological responses in vivo.
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Affiliation(s)
- Carol Dangelmaier
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Hymavathi Reddy Vari
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Dhruv N Vajipayajula
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Manal Elzoheiry
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Monica Wright
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Ashvin Iyer
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Alexander Y Tsygankov
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
| | - Satya P Kunapuli
- Sol Sherry Thrombosis Research Center, Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA
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Sun L, Wang Z, Liu Z, Mu G, Cui Y, Xiang Q. C-type lectin-like receptor 2: roles and drug target. Thromb J 2024; 22:27. [PMID: 38504248 PMCID: PMC10949654 DOI: 10.1186/s12959-024-00594-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Accepted: 03/07/2024] [Indexed: 03/21/2024] Open
Abstract
C-type lectin-like receptor-2 (CLEC-2) is a member of the C-type lectin superfamily of cell surface receptors. The first confirmed endogenous and exogenous ligands of CLEC-2 are podoplanin and rhodocytin, respectively. CLEC-2 is expressed on the surface of platelets, which participates in platelet activation and aggregation by binding with its ligands. CLEC-2 and its ligands are involved in pathophysiological processes, such as atherosclerosis, cancer, inflammatory thrombus status, maintenance of vascular wall integrity, and cancer-related thrombosis. In the last 5 years, different anti- podoplanin antibody types have been developed for the treatment of cancers, such as glioblastoma and lung cancer. New tests and new diagnostics targeting CLEC-2 are also discussed. CLEC-2 mediates thrombosis in various pathological states, but CLEC-2-specific deletion does not affect normal hemostasis, which would provide a new therapeutic tool for many thromboembolic diseases. The CLEC-2-podoplanin interaction is a target for cancer treatment. CLEC-2 may be applied in clinical practice and play a therapeutic role.
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Affiliation(s)
- Lan Sun
- Department of Pharmacy, Peking University First Hospital, No. 6, Da Hong Luo Chang Street, Xicheng District, Beijing, 100034, China
- Department of Pharmacy Administration and Clinical Pharmacy, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China
| | - Zhe Wang
- Department of Pharmacy, Peking University First Hospital, No. 6, Da Hong Luo Chang Street, Xicheng District, Beijing, 100034, China
- Institute of Clinical Pharmacology, Peking University, Beijing, China
| | - Zhiyan Liu
- Department of Pharmacy, Peking University First Hospital, No. 6, Da Hong Luo Chang Street, Xicheng District, Beijing, 100034, China
- Institute of Clinical Pharmacology, Peking University, Beijing, China
| | - Guangyan Mu
- Department of Pharmacy, Peking University First Hospital, No. 6, Da Hong Luo Chang Street, Xicheng District, Beijing, 100034, China
- Institute of Clinical Pharmacology, Peking University, Beijing, China
| | - Yimin Cui
- Department of Pharmacy, Peking University First Hospital, No. 6, Da Hong Luo Chang Street, Xicheng District, Beijing, 100034, China
- Department of Pharmacy Administration and Clinical Pharmacy, School of Pharmaceutical Sciences, Peking University Health Science Center, Beijing, China
- Institute of Clinical Pharmacology, Peking University, Beijing, China
| | - Qian Xiang
- Department of Pharmacy, Peking University First Hospital, No. 6, Da Hong Luo Chang Street, Xicheng District, Beijing, 100034, China.
- Institute of Clinical Pharmacology, Peking University, Beijing, China.
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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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Tsygankov AY. TULA Proteins in Men, Mice, Hens, and Lice: Welcome to the Family. Int J Mol Sci 2023; 24:ijms24119126. [PMID: 37298079 DOI: 10.3390/ijms24119126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 05/16/2023] [Accepted: 05/18/2023] [Indexed: 06/12/2023] Open
Abstract
The two members of the UBASH3/STS/TULA protein family have been shown to critically regulate key biological functions, including immunity and hemostasis, in mammalian biological systems. Negative regulation of signaling through immune receptor tyrosine-based activation motif (ITAM)- and hemITAM-bearing receptors mediated by Syk-family protein tyrosine kinases appears to be a major molecular mechanism of the down-regulatory effect of TULA-family proteins, which possess protein tyrosine phosphatase (PTP) activity. However, these proteins are likely to carry out some PTP-independent functions as well. Whereas the effects of TULA-family proteins overlap, their characteristics and their individual contributions to cellular regulation also demonstrate clearly distinct features. Protein structure, enzymatic activity, molecular mechanisms of regulation, and biological functions of TULA-family proteins are discussed in this review. In particular, the usefulness of the comparative analysis of TULA proteins in various metazoan taxa, for identifying potential roles of TULA-family proteins outside of their functions already established in mammalian systems, is examined.
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Affiliation(s)
- Alexander Y Tsygankov
- Sol Sherry Thrombosis Research Center, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, 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: 0] [Impact Index Per Article: 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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Kostyak JC, Mauri B, Dangelmaier C, Vari HR, Patel A, Wright M, Reddy H, Tsygankov AY, Kunapuli SP. Phosphorylation on Syk Y342 is important for both ITAM and hemITAM signaling in platelets. J Biol Chem 2022; 298:102189. [PMID: 35753354 PMCID: PMC9287148 DOI: 10.1016/j.jbc.2022.102189] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 06/09/2022] [Accepted: 06/10/2022] [Indexed: 11/29/2022] Open
Abstract
Immune cells express receptors bearing an immune tyrosine activation motif (ITAM) containing two YXXL motifs or hemITAMs containing only one YXXL motif. Phosphorylation of the ITAM/hemITAM is mediated by Src family kinases allowing for the binding and activation of spleen tyrosine kinase (Syk). It is believed that Syk must be phosphorylated on tyrosine residues for activation, and Tyr342, а conserved tyrosine in the interdomain B region, has been shown to be critical for regulating Syk in FcεR1-activated mast cells. Syk is a key mediator of signaling pathways downstream of several platelet pathways including the ITAM bearing glycoprotein VI (GPVI)/Fc receptor gamma chain collagen receptor and the hemITAM containing C-type lectin-like receptor-2 (CLEC-2). Since platelet activation is a crucial step in both hemostasis and thrombosis, we evaluated the importance of Syk Y342 in these processes by producing an Syk Y342F knock-in mouse. When using a CLEC-2 antibody as an agonist, reduced aggregation and secretion were observed in Syk Y342F mouse platelets when compared with control mouse platelets. Platelet reactivity was also reduced in response to the GPVI agonist collagen-related peptide. Signaling initiated by either GPVI or CLEC-2 was also greatly inhibited, including Syk Y519/520 phosphorylation. Hemostasis, as measured by tail bleeding time, was not altered in Syk Y342F mice, but thrombus formation in response to FeCl3 injury was prolonged in Syk Y342F mice. These data demonstrate that phosphorylation of Y342 on Syk following stimulation of either GPVI or CLEC-2 receptors is important for the ability of Syk to transduce a signal.
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Affiliation(s)
- John C Kostyak
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Benjamin Mauri
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Carol Dangelmaier
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Hymavathi Reddy Vari
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Akruti Patel
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Monica Wright
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Haritha Reddy
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Alexander Y Tsygankov
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA
| | - Satya P Kunapuli
- Sol Sherry Thrombosis Research Center and Department of Cardiovascular Sciences, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, USA.
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Dangelmaier C, Vari HR, Wright M, Kostyak JC, Kunapuli SP. Clustering extent-dependent differential signaling by CLEC-2 receptors in platelets. Res Pract Thromb Haemost 2022; 6:e12710. [PMID: 35573643 PMCID: PMC9074038 DOI: 10.1002/rth2.12710] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 03/08/2022] [Indexed: 11/12/2022] Open
Abstract
Background C-type lectin receptor family members play a role in many cells including platelets, where they are crucial in the separation of lymphatic and blood vessels during development. The C-type lectin-like receptor 2 (CLEC-2) receptor contains the canonical intracellular hemITAM motif through which it signals to activate Syk. Objectives One proposed hypothesis for signaling cascade is that Syk bridges two receptors through phosphorylated hemITAM motifs. We demonstrated that the phosphorylated hemITAM stimulates PI3 kinase/Btk pathways to activate Syk. To address this controversy, we used a CLEC-2 selective agonist and studied the role of Btk in platelet activation. Results and Conclusions Platelet activation and downstream signaling were abolished in murine and human platelets in the presence of the Btk inhibitors ibrutinib or acalabrutinib when a low concentration of a CLEC-2 antibody was used to crosslink CLEC-2 receptors. This inhibition was overcome by increasing concentrations of the CLEC-2 antibody. Similar results were obtained in X-linked immunodeficient mouse platelets, with an inactivating mutation in Btk or in Lyn null platelets. We conclude that at low crosslinking conditions of CLEC-2, Btk plays an important role in the activation of Syk, but at higher crosslinking conditions their role becomes less important and other mechanisms take over to activate Syk.
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Affiliation(s)
- Carol Dangelmaier
- Sol Sherry Thrombosis Research Center Lewis Katz School of Medicine Temple University Philadelphia Pennsylvania USA
| | - Hymavathi Reddy Vari
- Sol Sherry Thrombosis Research Center Lewis Katz School of Medicine Temple University Philadelphia Pennsylvania USA
| | - Monica Wright
- Sol Sherry Thrombosis Research Center Lewis Katz School of Medicine Temple University Philadelphia Pennsylvania USA
| | - John C Kostyak
- Sol Sherry Thrombosis Research Center Lewis Katz School of Medicine Temple University Philadelphia Pennsylvania USA
| | - Satya P Kunapuli
- Sol Sherry Thrombosis Research Center Lewis Katz School of Medicine Temple University Philadelphia Pennsylvania USA
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Kostyak JC, Mauri B, Patel A, Dangelmaier C, Reddy H, Kunapuli SP. Phosphorylation of protein kinase Cδ Tyr311 positively regulates thromboxane generation in platelets. J Biol Chem 2021; 296:100720. [PMID: 33932405 PMCID: PMC8164046 DOI: 10.1016/j.jbc.2021.100720] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 04/21/2021] [Accepted: 04/27/2021] [Indexed: 11/19/2022] Open
Abstract
Platelets are key mediators of physiological hemostasis and pathological thrombosis, whose function must be carefully balanced by signaling downstream of receptors such as protease-activated receptor (PAR)4. Protein kinase C (PKC) is known to regulate various aspects of platelet function. For instance, PKCδ is known to regulate dense granule secretion, which is important for platelet activation. However, the mechanism by which PKCδ regulates this process as well as other facets of platelet activity is unknown. We speculated that the way PKCδ regulates platelet function may be because of the phosphorylation of tyrosine residues on PKCδ. We investigated phosphorylation of PKCδ following glycoprotein VI-mediated and PAR4-mediated platelet activation and found that Y311 is selectively phosphorylated when PAR4 is activated in human platelets. Therefore, we generated PKCδ Y311F knock-in mice, which are viable and have no gross abnormalities. However, PKCδY311F mice have significantly enhanced tail-bleeding times compared with WT littermate controls, which means hemostasis is interrupted. Furthermore, PKCδY311F mice exhibit longer time to carotid artery occlusion compared with WT control using a ferric chloride in vivo thrombosis model, indicating that the phosphorylation of PKCδ Y311 is prothrombotic. Washed platelets from PKCδY311F mice have reduced reactivity after stimulation with a PAR-4 agonist indicating its importance in platelet signaling. The phenotype observed in Y311F mouse platelets is because of reduced thromboxane generation, as an inhibitor of thromboxane generation equalizes the PKCδY311F platelet response to that of WT. Therefore, phosphorylation of PKCδ on Y311 is important for regulation of platelet function and specifically thromboxane generation, which reinforces platelet activation.
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Affiliation(s)
- John C Kostyak
- Sol Sherry Thrombosis Research Center, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA
| | - Benjamin Mauri
- Sol Sherry Thrombosis Research Center, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA
| | - Akruti Patel
- Sol Sherry Thrombosis Research Center, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA
| | - Carol Dangelmaier
- Sol Sherry Thrombosis Research Center, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA
| | - Haritha Reddy
- Sol Sherry Thrombosis Research Center, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA
| | - Satya P Kunapuli
- Sol Sherry Thrombosis Research Center, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA; Department of Physiology, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA; Department of Pharmacology, Temple University School Lewis M Katz School of Medicine, Philadelphia, Pennsylvania, USA.
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Parashar K, Carpino N. A role for the Sts phosphatases in negatively regulating IFNγ-mediated production of nitric oxide in monocytes. IMMUNITY INFLAMMATION AND DISEASE 2020; 8:523-533. [PMID: 32841534 PMCID: PMC7654413 DOI: 10.1002/iid3.336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 07/01/2020] [Accepted: 07/20/2020] [Indexed: 12/17/2022]
Abstract
Introduction The atypical Sts phosphatases negatively regulate signaling pathways in diverse immune cell types, with two of their molecular targets being the related kinases Syk and Zap‐70. Mice lacking Sts expression (Sts−/−) are resistant to infection by the live vaccine strain (LVS) of Francisella tularensis. Although the mechanisms underlying the enhanced resistance of Sts−/− mice have not been definitively established, Sts−/− bone marrow‐derived monocytes (BMMs) demonstrate greater clearance of intracellular LVS following ex vivo infection, relative to wild type cells. To determine how the Sts proteins regulate monocyte bactericidal properties, we analyzed responses of infected cells. Methods Monocyte bacterial clearance was assayed using ex vivo coculture infections followed by colony‐forming unit analysis of intracellular bacteria. Levels of gene expression were quantified by quantitative reverse‐transcription polymerase chain reaction, levels of Nos2 protein levels were quantified by Western blot analysis, and levels of nitric oxide (NO) were quantified directly using the Griess reagent. We characterized monocyte cytokine production via enzyme‐linked immunosorbent assay. Results We demonstrate that Sts−/− monocyte cultures produce elevated levels of interferon‐γ (IFNγ) after infection, relative to wild type cultures. Sts−/− monocytes also demonstrate heightened responsiveness to IFNγ. Specifically, Sts−/− monocytes produce elevated levels of antimicrobial NO following IFNγ stimulation, and this NO plays an important role in LVS restriction. Additional IFNγ‐stimulated genes, including Ip10 and members of the Gbp gene family, also display heightened upregulation in Sts−/− cells. Both Sts‐1 and Sts‐2 contribute to the regulation of NO production, as evidenced by the responses of monocytes lacking each phosphatase individually. Finally, we demonstrate that the elevated production of IFNγ‐induced NO in Sts−/− monocytes is abrogated following chemical inhibition of Syk kinase. Conclusion Our results indicate a novel role for the Sts enzymes in regulating monocyte antibacterial responses downstream of IFNγ.
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Affiliation(s)
- Kaustubh Parashar
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York
| | - Nicholas Carpino
- Department of Microbiology and Immunology, Stony Brook University, Stony Brook, New York
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Tsygankov AY. TULA proteins as signaling regulators. Cell Signal 2019; 65:109424. [PMID: 31639493 DOI: 10.1016/j.cellsig.2019.109424] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 09/16/2019] [Accepted: 09/18/2019] [Indexed: 10/25/2022]
Abstract
Two members of the UBASH3/STS/TULA family exhibit a unique protein domain structure, which includes a histidine phosphatase domain, and play a key role in regulating cellular signaling. UBASH3A/STS-2/TULA is mostly a lymphoid protein, while UBASH3B/STS-1/TULA-2 is expressed ubiquitously. Dephosphorylation of tyrosine-phosphorylated proteins by TULA-2 and, probably to a lesser extent, by TULA critically contribute to the molecular basis of their regulatory effect. The notable differences between the effects of the two family members on cellular signaling and activation are likely to be linked to the difference between their specific enzymatic activities. However, these differences might also be related to the functions of their domains other than the phosphatase domain and independent of their phosphatase activity. The down-regulation of the Syk/Zap-70-mediated signaling, which to-date appears to be the best-studied regulatory effect of TULA family, is discussed in detail in this publication.
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Affiliation(s)
- Alexander Y Tsygankov
- Sol Sherry Thrombosis Research Center, Fels Institute for Cancer Research and Department of Microbiology and Immunology, Lewis Katz School of Medicine at Temple University, 3400 N. Broad Street, Philadelphia, PA, 19140, United States.
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