Fine-Tuning of Platelet Responses by Serine/Threonine Protein Kinases and Phosphatases—Just the Beginning

Shiravand, Yavar; Walter, Ulrich; Jurk, Kerstin

doi:10.1055/a-1476-7873

Cited by 7 publications

(4 citation statements)

References 104 publications

(171 reference statements)

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“…On the other hand, we found that the inhibition of protein phosphatase 2A (PP2A) increased Syk S297 phosphorylation, which led to reduced Syk tyrosine phosphorylation and activity [29]. These data support the concept that the Syk S297 phosphorylation/dephosphorylation by the key protein kinase (PKC) and phosphatase (PP2A) is a mechanism of regulatory cross-talk linked to tyrosine phosphorylation, and that it represents a feedback mechanism for controlling Syk activation in human platelets [30].…”

Section: Introductionsupporting

confidence: 76%

Differential Regulation of GPVI-Induced Btk and Syk Activation by PKC, PKA and PP2A in Human Platelets

Zhang

Solari

Heemskerk

et al. 2023

IJMS

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Bruton’s tyrosine kinase (Btk) and spleen tyrosine kinase (Syk) are major signaling proteins in human platelets that are implicated in atherothrombosis and thrombo-inflammation, but the mechanisms controlling their activities are not well understood. Previously, we showed that Syk becomes phosphorylated at S297 in glycoprotein VI (GPVI)-stimulated human platelets, which limits Syk activation. Here, we tested the hypothesis that protein kinases C (PKC) and A (PKA) and protein phosphatase 2A (PP2A) jointly regulate GPVI-induced Btk activation in platelets. The GPVI agonist convulxin caused rapid, transient Btk phosphorylation at S180 (pS180↑), Y223 and Y551, while direct PKC activation strongly increased Btk pS180 and pY551. This increase in Btk pY551 was also Src family kinase (SFK)-dependent, but surprisingly Syk-independent, pointing to an alternative mechanism of Btk phosphorylation and activation. PKC inhibition abolished convulxin-stimulated Btk pS180 and Syk pS297, but markedly increased the tyrosine phosphorylation of Syk, Btk and effector phospholipase Cγ2 (PLCγ2). PKA activation increased convulxin-induced Btk activation at Y551 but strongly suppressed Btk pS180 and Syk pS297. PP2A inhibition by okadaic acid only increased Syk pS297. Both platelet aggregation and PLCγ2 phosphorylation with convulxin stimulation were Btk-dependent, as shown by the selective Btk inhibitor acalabrutinib. Together, these results revealed in GPVI-stimulated platelets a transient Syk, Btk and PLCγ2 phosphorylation at multiple sites, which are differentially regulated by PKC, PKA or PP2A. Our work thereby demonstrated the GPVI–Syk–Btk signalosome as a tightly controlled protein kinase network, in agreement with its role in atherothrombosis.

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Section: Introductionsupporting

confidence: 76%

Differential Regulation of GPVI-Induced Btk and Syk Activation by PKC, PKA and PP2A in Human Platelets

Zhang

Solari

Heemskerk

et al. 2023

IJMS

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“…Platelets are a major source of THBS1. Activation is followed by secretion from α-granules and recruitment and aggregation at the site of injury [ 33 , 34 ]. Therefore, we assumed that the increase in THBS1 in the liver might be paralleled by an increase in the blood.…”

Section: Resultsmentioning

confidence: 99%

Approaching Thrombospondin-1 as a Potential Target for Mesenchymal Stromal Cells to Support Liver Regeneration after Partial Hepatectomy in Mouse and Humans

Tietze,

Christ,

et al. 2024

Cells

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Extended liver resection carries the risk of post-surgery liver failure involving thrombospondin-1-mediated aggravation of hepatic epithelial plasticity and function. Mesenchymal stromal cells (MSCs), by interfering with thrombospondin-1 (THBS1), counteract hepatic dysfunction, though the mechanisms involved remain unknown. Herein, two-thirds partial hepatectomy in mice increased hepatic THBS1, downstream transforming growth factor-β3, and perturbation of liver tissue homeostasis. All these events were ameliorated by hepatic transfusion of human bone marrow-derived MSCs. Treatment attenuated platelet and macrophage recruitment to the liver, both major sources of THBS1. By mitigating THBS1, MSCs muted surgery-induced tissue deterioration and dysfunction, and thus supported post-hepatectomy regeneration. After liver surgery, patients displayed increased tissue THBS1, which is associated with functional impairment and may indicate a higher risk of post-surgery complications. Since liver dysfunction involving THBS1 improves with MSC treatment in various animal models, it seems feasible to also modulate THBS1 in humans to impede post-surgery acute liver failure.

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“…Whereas the PGI 2 receptor (PTGIR = prostaglandin I 2 receptor) is expressed on the platelet surface, NO signals via intracellular soluble guanylyl cyclases [57][58][59]. However, both set points induce VASP phosphorylation mediated through cAMP/cGMP-induced activation of PKA/PKG [60,61].…”

Section: Analysis Of Set Point Components For Homeostasismentioning

confidence: 99%

Platelets and the Cybernetic Regulation of Ischemic Inflammatory Responses through PNC Formation Regulated by Extracellular Nucleotide Metabolism and Signaling

Granja

Köhler²,

Leiss

et al. 2022

Cells

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Ischemic events are associated with severe inflammation and are here referred to as ischemic inflammatory response (IIR). Recent studies identified the formation of platelet–neutrophil complexes (PNC) as key players in IIR. We investigated the role of extracellular platelet nucleotide signaling in the context of IIR and defined a cybernetic circle, including description of feedback loops. Cybernetic circles seek to integrate different levels of information to understand how biological systems function. Our study specifies the components of the cybernetic system of platelets in IIR and describes the theoretical progression of IIR passing the cybernetic cycle with positive and negative feedback loops based on nucleotide-dependent signaling and functional regulation. The cybernetic components and feedback loops were explored by cytometry, immunohistological staining, functional blocking antibodies, and ADP/ATP measurements. Using several ex vivo and in vivo approaches we confirmed cybernetic parameters, such as controller, sensor, and effector (VASP phosphorylation, P2Y12, ADORAs and GPIIb/IIIa activity), as well as set points (ADP, adenosine) and interfering control and disturbance variables (ischemia). We demonstrate the impact of the regulated platelet–neutrophil complex (PNC) formation in blood and the resulting damage to the affected inflamed tissue. Taken together, extracellular nucleotide signaling, PNC formation, and tissue damage in IIR can be integrated in a controlled cybernetic circle of platelet function, as introduced through this study.

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Fine-Tuning of Platelet Responses by Serine/Threonine Protein Kinases and Phosphatases—Just the Beginning

Cited by 7 publications

References 104 publications

Differential Regulation of GPVI-Induced Btk and Syk Activation by PKC, PKA and PP2A in Human Platelets

Differential Regulation of GPVI-Induced Btk and Syk Activation by PKC, PKA and PP2A in Human Platelets

Approaching Thrombospondin-1 as a Potential Target for Mesenchymal Stromal Cells to Support Liver Regeneration after Partial Hepatectomy in Mouse and Humans

Platelets and the Cybernetic Regulation of Ischemic Inflammatory Responses through PNC Formation Regulated by Extracellular Nucleotide Metabolism and Signaling

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