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Khatlani T, Pradhan S, Langlois K, Subramanyam D, Rumbaut RE, Vijayan KV. Opposing Roles for the α Isoform of the Catalytic Subunit of Protein Phosphatase 1 in Inside-Out and Outside-In Integrin Signaling in Murine Platelets. Cells 2023; 12:2424. [PMID: 37887268 PMCID: PMC10605409 DOI: 10.3390/cells12202424] [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: 09/07/2023] [Revised: 10/04/2023] [Accepted: 10/06/2023] [Indexed: 10/28/2023] Open
Abstract
Platelet activation during hemostasis and thrombosis is facilitated by agonist-induced inside-out and integrin αIIbβ3-initiated outside-in signaling via protein kinases and phosphatases. Pharmacological inhibitor studies suggest that the serine/threonine protein phosphatase 1 (PP1) promotes platelet activation. However, since phosphatase inhibitors block all the isoforms of the catalytic subunit of PP1 (PP1c), the role of specific PP1c isoform in platelet signaling remains unclear. Here, we employed a platelet-specific PP1cα-/- mice to explore the contribution of a major PP1 isoform in platelet functions. Loss of PP1cα moderately decreased activation of integrin αIIbβ3, binding of soluble fibrinogen, and aggregation to low-dose thrombin, ADP, and collagen. In contrast, PP1cα-/- platelets displayed increased adhesion to immobilized fibrinogen, fibrin clot retraction, and thrombus formation on immobilized collagen. Mechanistically, post-fibrinogen engagement potentiated p38 mitogen-activated protein kinase (MAPK) activation in PP1cα-/- platelets and the p38 inhibitor blocked the increased integrin-mediated outside-in signaling function. Tail bleeding time and light-dye injury-induced microvascular thrombosis in the cremaster venules and arterioles were not altered in PP1cα-/- mice. Thus, PP1cα displays pleiotropic signaling in platelets as it amplifies agonist-induced signaling and attenuates integrin-mediated signaling with no impact on hemostasis and thrombosis.
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Affiliation(s)
- Tanvir Khatlani
- Cardiovascular Research Section, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
- Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, USA
| | - Subhashree Pradhan
- Cardiovascular Research Section, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
- Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, USA
| | - Kimberly Langlois
- Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, USA
- Pulmonary Section, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Deepika Subramanyam
- Cardiovascular Research Section, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
- Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, USA
| | - Rolando E. Rumbaut
- Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, USA
- Pulmonary Section, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - K. Vinod Vijayan
- Cardiovascular Research Section, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
- Center for Translational Research on Inflammatory Diseases (CTRID), Michael E. DeBakey Veterans Affairs Medical Center (MEDVAMC), Houston, TX 77030, USA
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Jansen EE, Hartmann M. Clot Retraction: Cellular Mechanisms and Inhibitors, Measuring Methods, and Clinical Implications. Biomedicines 2021; 9:1064. [PMID: 34440268 PMCID: PMC8394358 DOI: 10.3390/biomedicines9081064] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/09/2021] [Accepted: 08/17/2021] [Indexed: 11/22/2022] Open
Abstract
Platelets have important functions in hemostasis. Best investigated is the aggregation of platelets for primary hemostasis and their role as the surface for coagulation leading to fibrin- and clot-formation. Importantly, the function of platelets does not end with clot formation. Instead, platelets are responsible for clot retraction through the concerted action of the activated αIIbβ3 receptors on the surface of filopodia and the platelet's contractile apparatus binding and pulling at the fibrin strands. Meanwhile, the signal transduction events leading to clot retraction have been investigated thoroughly, and several targets to inhibit clot retraction have been demonstrated. Clot retraction is a physiologically important mechanism allowing: (1) the close contact of platelets in primary hemostasis, easing platelet aggregation and intercellular communication, (2) the reduction of wound size, (3) the compaction of red blood cells to a polyhedrocyte infection-barrier, and (4) reperfusion in case of thrombosis. Several methods have been developed to measure clot retraction that have been based on either the measurement of clot volume or platelet forces. Concerning the importance of clot retraction in inborn diseases, the failure of clot retraction in Glanzmann thrombasthenia is characterized by a bleeding phenotype. Concerning acquired diseases, altered clot retraction has been demonstrated in patients with coronary heart disease, stroke, bronchial asthma, uremia, lupus erythematodes, and other diseases. However, more studies on the diagnostic and prognostic value of clot retraction with methods that have to be standardized are necessary.
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Affiliation(s)
- Ellen E. Jansen
- Clinic for Operative Dentistry, Periodontology and Preventive Dentistry, RWTH Aachen University, 52074 Aachen, Germany;
| | - Matthias Hartmann
- Klinik für Anästhesiologie und Intensivmedizin, Universitätsklinikum Essen, Universität Duisburg-Essen, 45122 Essen, Germany
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Hurtado B, Trakala M, Ximénez-Embún P, El Bakkali A, Partida D, Sanz-Castillo B, Álvarez-Fernández M, Maroto M, Sánchez-Martínez R, Martínez L, Muñoz J, García de Frutos P, Malumbres M. Thrombocytopenia-associated mutations in Ser/Thr kinase MASTL deregulate actin cytoskeletal dynamics in platelets. J Clin Invest 2018; 128:5351-5367. [PMID: 30252678 DOI: 10.1172/jci121876] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 09/18/2018] [Indexed: 12/18/2022] Open
Abstract
MASTL, a Ser/Thr kinase that inhibits PP2A-B55 complexes during mitosis, is mutated in autosomal dominant thrombocytopenia. However, the connections between the cell-cycle machinery and this human disease remain unexplored. We report here that, whereas Mastl ablation in megakaryocytes prevented proper maturation of these cells, mice carrying the thrombocytopenia-associated mutation developed thrombocytopenia as a consequence of aberrant activation and survival of platelets. Activation of mutant platelets was characterized by hyperstabilized pseudopods mimicking the effect of PP2A inhibition and actin polymerization defects. These aberrations were accompanied by abnormal hyperphosphorylation of multiple components of the actin cytoskeleton and were rescued both in vitro and in vivo by inhibiting upstream kinases such as PKA, PKC, or AMPK. These data reveal an unexpected role of Mastl in actin cytoskeletal dynamics in postmitotic cells and suggest that the thrombocytopenia-associated mutation in MASTL is a pathogenic dominant mutation that mimics decreased PP2A activity resulting in altered phosphorylation of cytoskeletal regulatory pathways.
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Affiliation(s)
- Begoña Hurtado
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain.,Department of Cell Death and Proliferation, Institut d'Investigacions Biomèdiques de Barcelona-Consejo Superior de Investigaciones Científicas- Institut d'Investigacions Biomèdiques August Pi i Sunyer- (IIBB-CSIC-IDIBAPS), Barcelona, Spain
| | - Marianna Trakala
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Pilar Ximénez-Embún
- ProteoRed - Instituto de Salud Carlos III (ISCIII) and Proteomics Unit, CNIO, Madrid, Spain
| | - Aicha El Bakkali
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - David Partida
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Belén Sanz-Castillo
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | | | - María Maroto
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Ruth Sánchez-Martínez
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | | | - Javier Muñoz
- ProteoRed - Instituto de Salud Carlos III (ISCIII) and Proteomics Unit, CNIO, Madrid, Spain
| | - Pablo García de Frutos
- Department of Cell Death and Proliferation, Institut d'Investigacions Biomèdiques de Barcelona-Consejo Superior de Investigaciones Científicas- Institut d'Investigacions Biomèdiques August Pi i Sunyer- (IIBB-CSIC-IDIBAPS), Barcelona, Spain
| | - Marcos Malumbres
- Cell Division and Cancer Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
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Abstract
Integrin αIIbβ3 is a highly abundant heterodimeric platelet receptor that can transmit information bidirectionally across the plasma membrane, and plays a critical role in hemostasis and thrombosis. Upon platelet activation, inside-out signaling pathways increase the affinity of αIIbβ3 for fibrinogen and other ligands. Ligand binding and integrin clustering subsequently stimulate outside-in signaling, which initiates and amplifies a range of cellular events driving essential platelet processes such as spreading, thrombus consolidation, and clot retraction. Integrin αIIbβ3 has served as an excellent model for the study of integrin biology, and it has become clear that integrin outside-in signaling is highly complex and involves a vast array of enzymes, signaling adaptors, and cytoskeletal components. In this review, we provide a concise but comprehensive overview of αIIbβ3 outside-in signaling, focusing on the key players involved, and how they cooperate to orchestrate this critical aspect of platelet biology. We also discuss gaps in the current understanding of αIIbβ3 outside-in signaling and highlight avenues for future investigation.
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