Search results for "KINASE"
showing 10 items of 2635 documents
Differential roles of cAMP and cGMP in megakaryocyte maturation and platelet biogenesis
2012
The cyclic nucleotides cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) regulate the activity of protein kinase A (PKA) and protein kinase G (PKG), respectively. This process helps maintain circulating platelets in a resting state. Here we studied the role of cAMP and cGMP in the regulation of megakaryocyte (MK) differentiation and platelet formation. Cultured, platelet-producing MKs were differentiated from fetal livers harvested from 13.5 days postcoital mouse embryos. MK development was accompanied by a dramatic increase in cAMP production and expression of soluble guanylate cyclase, PKG, and PKA as well as their downstream targets vasodilator-stimulated ph…
Time-resolved characterization of cAMP/PKA-dependent signaling reveals that platelet inhibition is a concerted process involving multiple signaling p…
2014
One of the most important physiological platelet inhibitors is endothelium-derived prostacyclin which stimulates the platelet cyclic adenosine monophosphate/protein kinase A (cAMP/PKA)-signaling cascade and inhibits virtually all platelet-activating key mechanisms. Using quantitative mass spectrometry, we analyzed time-resolved phosphorylation patterns in human platelets after treatment with iloprost, a stable prostacyclin analog, for 0, 10, 30, and 60 seconds to characterize key mediators of platelet inhibition and activation in 3 independent biological replicates. We quantified over 2700 different phosphorylated peptides of which 360 were significantly regulated upon stimulation. This com…
Potential and limitations of PKA/ PKG inhibitors for platelet studies
2021
Cyclic nucleotides (cAMP and cGMP) and corresponding protein kinases, protein kinase A (PKA) and protein kinase G (PKG), are the main intracellular mediators of endothelium-derived platelet inhibitors. Pharmacological PKA/PKG inhibitors are often used to discriminate between these two kinase activities and to analyze their underlying mechanisms. Previously we showed that all widely used PKG inhibitors (KT5823, DT3, RP isomers) either did not inhibit PKG or inhibited and even activated platelets independently from PKG. In this study, we examined several PKA inhibitors as well as inhibitors of adenylate and guanylate cyclases to reveal their effects on platelets and establish whether they are…
Large platelets but not putative endothelial progenitor cells are associated with low strut coverage after drug-eluting stent implantation
2015
Objectives This study assessed whether different subsets of circulating endothelial and putative endothelial progenitor cells (CEC and EPC) correlate with stent strut coverage (SSC) using second generation optical coherence tomography (OCT). Background Due to the lack of imaging modalities with a resolution down to the magnitude of a few cells, the influence of EPC on endothelialisation of drug-eluting stents has not been assessed in patients. Methods In 37 patients, SSC of everolimus-eluting stents was assessed by OCT 5-7months after stent implantation. Different subsets of EPC (CD34(+)KDR(+), CD34(+)KDR(+)CD45(dim), CD133(+), CD3(+)CD31(+)), CEC (CD31(+)CD45(-)CD146(+)), and CD31(+)CD45(-…
Activation of cGMP-dependent Protein Kinase Iβ Inhibits Interleukin 2 Release and Proliferation of T Cell Receptor-stimulated Human Peripheral T Cells
2000
Several major functions of type I cGMP-dependent protein kinase (cGK I) have been established in smooth muscle cells, platelets, endothelial cells, and cardiac myocytes. Here we demonstrate that cGK Ibeta is endogenously expressed in freshly purified human peripheral blood T lymphocytes and inhibits their proliferation and interleukin 2 release. Incubation of human T cells with the NO donor, sodium nitroprusside, or the membrane-permeant cGMP analogs PET-cGMP and 8-pCPT-cGMP, activated cGK I and produced (i) a distinct pattern of phosphorylation of vasodilator-stimulated phosphoprotein, (ii) stimulation of the mitogen-activated protein kinases ERK1/2 and p38 kinase, and, upon anti-CD3 stimu…
The histone deacetylase sirtuin 2 is a new player in the regulation of platelet function
2015
SummaryBackground Histone deacetylases (HDACs) play a key role in signaling in many cell types. However, little is known about the participation of HDACs, particularly sirtuins (SIRTs), in platelet reactivity. Objective To investigate the role of HDACs in platelets, we examined the effects of SIRT inhibition on platelet function and protein acetylation in human platelets. Methods We used washed platelets obtained from healthy subjects. Cambinol (SIRT1 and SIRT2 inhibitor), AGK2 (specific SIRT2 inhibitor) and EX527 (specific SIRT1 inhibitor) were used as SIRT inhibitors. Platelets were stimulated with collagen, thrombin, or U46619, and platelet responses were determined according to optical …
Phosphorylation of CalDAG-GEFI by protein kinase A prevents Rap1b activation.
2013
Summary Background Signaling via protein kinase A (PKA) and protein kinase G (PKG) is critical for maintaining platelets in the resting state. Both kinases down-regulate the activity of the small GTPase Rap1b, a critical signaling switch for integrin activation and platelet aggregation. However, the mechanism of Rap1b regulation by PKA and PKG is largely unknown. Objective To identify the PKA phosphorylation sites in calcium and diacylglycerol-regulated guanine nucleotide exchange factor I (CalDAG-GEFI), the main GEF for Rap1b in platelets, and the effect of CalDAG-GEFI phosphorylation in Rap1b activation. Methods The phosphorylation sites in CalDAG-GEFI were identified by radio-active phos…
Deciphering of ADP-induced, phosphotyrosine-dependent signaling networks in human platelets by Src-homology 2 region (SH2)-profiling.
2012
Tyrosine phosphorylation plays a central role in signal transduction controlling many important biological processes. In platelets, the activity of several signaling proteins is controlled by tyrosine phosphorylation ensuring proper platelet activation and aggregation essential for regulation of the delicate balance between bleeding and hemostasis. Here, we applied Src-homology 2 region (SH2)-profiling for deciphering of the phosphotyrosine state of human platelets activated by adenosine diphosphate (ADP). Applying a panel of 31 SH2-domains, rapid and complex regulation of the phosphotyrosine state of platelets was observed after ADP stimulation. Specific inhibition of platelet P2Y receptor…
New Insights into Platelet Signalling Pathways by Functional and Proteomic Approaches
2018
As circulating sentinels of vascular integrity, platelets act as crucial haemostatic cells as well as important inflammatory and immune cells, whereas under pathological conditions platelets drive thrombotic as well as non-thrombotic diseases related to chronic inflammation. In addition, platelets serve as an important cellular model to study the biology and pharmacology of signal transduction pathways. Platelet inhibition and activation responses are mediated by multiple signalling networks, which are tightly regulated by balanced catalysis of protein phosphorylation and dephosphorylation through protein kinases and protein phosphatases, respectively. However, we are only at the beginning …
Reciprocal regulation of human platelet function by endogenous prostanoids and through multiple prostanoid receptors
2014
Platelets are permanently exposed to a variety of prostanoids formed by blood cells or the vessel wall. The two major prostanoids, prostacyclin and thromboxane act through well established pathways mediated by their respective G-protein coupled receptors inhibiting or promoting platelet aggregation accordingly. Yet the role of other prostanoids and prostanoid receptors for platelet function regulation has not been thoroughly investigated. We aimed at a comprehensive analysis of prostanoid effects on platelets, the receptors and pathways involved and functional consequences. We analyzed cAMP formation and phosphorylation of proteins pivotal to platelet function as well as functional platelet…