Role of Erythrocytes in Signal Transduction Mechanisms of Recruiting Platelets: Effects on Platelet Tyrosine Phosphorylation and Cytoskeletal Reorganization.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3887-3887
Author(s):  
Juana Valles ◽  
Maria T. Santos ◽  
Antonio Moscardo ◽  
Maria A. Dasi ◽  
Justo Aznar
Keyword(s):  
Signal Transduction ◽  
Tyrosine Phosphorylation ◽  
Platelet Activation ◽  
Receptor Activation ◽  
Cytoskeletal Reorganization ◽  
Functional Responses ◽  
Transduction Mechanisms ◽  
Platelet Releasate ◽  
Biochemical Mechanisms

Abstract Platelet activation induces the release of granular components and metabolic products. This platelet releasate is a complex physiological agonist that upon interaction with other platelets induces platelet recruitment and thrombus growth. The agonistic potency of the platelet releasate is increased when platelets are stimulated in the presence of intact erythrocytes (RBCs) (Santos et al J. Clin Invest1991; 87: 571; Valles et al Blood1991;78:154). The result is enhanced recruitment, α IIbβ3 receptor activation and P-selectin exposure in recruiting platelets (Valles et al Blood2002;99:3978). Receptor-mediated platelet activation initiates mechanisms of signal transduction that culminate in platelet functional responses. The biochemical mechanisms regulating the effects of cell-releasates in promoting platelet recruitment have not yet been elucidated. The aims of this study are: a) to characterize the effects of releasates from collagen-stimulated platelets on protein tyrosine phosphorylation (PTP), cytoskeletal reorganization and translocation to cytoskeleton of proteins in platelets being tested for recruitment; and b) to study the effects of platelet-erythrocyte interactions in these processes. Washed platelets (WP) or WP+RBCs (Htc. 40%) were stimulated with fibrillar collagen (1μg/mL) and rapidly centrifuged to obtain a cell-free collagen-free releasate within 1 min. An aliquot of this releasate was used as platelet agonist and the proaggregatory response (recruitment) was monitored by optical aggregometry as in the references above. For kinetic studies the reaction was halted at 15–180 sec., and PTP, cytoskeletal reorganization and cytoskeletal-associated tyrosine phosphorylated substrates were evaluated (Santos et al Circulation2000; 102:1924–1930). Our results demonstrate for the first time that the platelet releasate induces PTP in the platelets tested for recruitment. This effect is remarkably amplified with releasates from platelet-erythrocyte mixtures especially at earlier time points. Of interest is the strong FAK phosphorylation induced by this releasate, a kinase thought to play a role in αIIbβ3 clustering and focal adhesion formation. The greater potency of the platelet-erythrocyte releasate was also evident in cytoskeletal reorganization (actin, ABP, talin). The platelet-erythrocyte releasate induced more PTP and cytoskeletal reorganization than 20 m M ADP. Cytoskeletal reorganization and translocation of tyrosine phosphorylated substrates to the cytoskeleton induced by the platelet-erythrocyte releasate were quicker than those induced by 1 U/ml thrombin and were of comparable final intensity. Interestingly, erythrocytes markedly enhanced translocation of FAK kinase and αIIbβ3 to the platelet cytoskeleton. The data reveal new biochemical mechanisms regulating platelet recruitment and demonstrate the remarkable role of erythrocytes in the signal transduction mechanisms of platelets during the recruitment process, which is a limiting step in mural thrombus formation. (Grant FIS 03/0270).

Distinct Domains of αIIbβ3 Support Different Aspects of Outside-In Signal Transduction and Platelet Activation Induced by LSARLAF, an αIIbβ3 Interacting Peptide

2001 ◽  
Vol 86 (09) ◽  
pp. 894-901 ◽  
Author(s):  
Jerry Derrick ◽  
Sanford Shattil ◽  
Mortimer Poncz ◽  
Ralph Gruppo ◽  
Kent Gartner
Keyword(s):  
Signal Transduction ◽  
Platelet Aggregation ◽  
Tyrosine Phosphorylation ◽  
Platelet Activation ◽  
Cytoplasmic Tail ◽  
Cytoplasmic Domain ◽  
Cytoskeletal Reorganization ◽  
Integrin Β3 ◽  
Platelet Spreading

SummaryThe peptide LSARLAF causes αIIbβ3-dependent platelet activation exemplified by secretion, aggregation, spreading and adhesion on fibrinogen, and tyrosine phosphorylation. αIIbβ3-dependent outside-in signal transduction induced by LSARLAF was investigated in variant thrombasthenic platelets which lack most of the cytoplasmic domain of the integrin β3 subunit (αIIbβ3 Δ724). These studies revealed that only certain aspects of this αIIbβ3-dependent outside-in signaling were affected by the β3 truncation. Specifically, αIIbβ3 724 supported LSARLAF-induced platelet aggregation, agglutination and secretion, but failed to trigger cytoskeletal reorganization and platelet spreading on fibrinogen, despite the fact that PMA-induced non αIIbβ3 mediated signaling caused spreading of these platelets on fibrinogen. Thus, distinct domains of αIIbβ3 are required to support different aspects of LSARLAF-induced platelet activation. Furthermore, these studies suggest that not all αIIbβ3-dependent platelet responses require an intact β3 cytoplasmic tail.

Collagen Induces Normal Signal Transduction in Platelets Deficient in CD36 (Platelet Glycoprotein IV)

1994 ◽  
Vol 71 (03) ◽  
pp. 353-356 ◽  
Author(s):  
James L Daniel ◽  
Carol Dangelmaier ◽  
Robert Strouse ◽  
J Bryan Smith
Keyword(s):  
Signal Transduction ◽  
Tyrosine Phosphorylation ◽  
Platelet Activation ◽  
Tyrosine Kinases ◽  
Platelet Glycoprotein ◽  
Serotonin Secretion

SummaryThe receptor involved in platelet activation by collagen has not been identified. Platelet glycoprotein IV, now known as CD36, has been implicated in interaction with collagen and also been shown to be associated with intracellular tyrosine kinases. In order to investigate the possible role of collagen-mediated signal transduction via CD36, platelets were obtained from a donor that were deficient in CD36. The collagen-induced intracellular mobilization of Ca2+ in the CD36 deficient cells was of the same magnitude as that seen in platelets from normal donors. In addition, serotonin secretion did not appear to be impaired. Tyrosine phosphorylation was also comparable between the CD36-deficient and normal platelets. Thus, it is unlikely that CD36 plays a major role in collagen-dependent platelet signal transduction.

Streptococcus sanguis-induced platelet activation involves two waves of tyrosine phosphorylation mediated by FcγRIIA and αIIbβ3

2005 ◽  
Vol 93 (05) ◽  
pp. 932-939 ◽  
Author(s):  
Caroline Pampolina ◽  
Archibald McNicol
Keyword(s):  
Signal Transduction ◽  
Platelet Aggregation ◽  
Tyrosine Phosphorylation ◽  
Platelet Activation ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine Phosphatases ◽  
Lag Phase ◽  
Dependent Manner ◽  
Protein Tyrosine ◽  
Streptococcus Sanguis

SummaryThe low-affinity IgG receptor, FcγRIIA, has been implicated in Streptococcus sanguis-induced platelet aggregation. Therefore, it is likely that signal transduction is at least partly mediated by FcγRIIA activation and a tyrosine kinase-dependent pathway. In this study the signal transduction mechanisms associated with platelet activation in response to the oral bacterium, S. sanguis were characterised. In the presence of IgG, S. sanguis strain 2017–78 caused the tyrosine phosphorylation of FcγRIIA 30s following stimulation, which led to the phosphorylation of Syk, LAT, and PLCγ2. These early events were dependent on Src family kinases but independent of either TxA2 or the engagement of the αIIbβ3 integrin. During the lag phase prior to platelet aggregation, FcγRIIA, Syk, LAT, and PLCγ2 were each dephosphorylated, but were re-phosphorylated as aggregation occurred. Platelet stimulation by 2017–78 also induced the tyrosine phosphorylation of PECAM-1, an ITIM-containing receptor that recruits protein tyrosine phosphatases. PECAM-1 co-precipitated with the protein tyrosine phosphatase SHP-1 in the lag phase. SHP-1 was also maximally tyrosine phosphorylated during this phase, suggesting a possible role for SHP-1 in the observed dephosphorylation events. As aggregation occurred, SHP-1 was dephosphorylated, while FcγRIIA, Syk, LAT, and PLCγ2 were rephosphorylated in an RGDS-sensitive, and therefore αIIbβ3-dependent, manner. Additionally, TxA2 release, 5-hydro-xytryptamine secretion and phosphatidic acid formation were all blocked by RGDS. Aspirin also abolished these events, but only partially inhibited αIIbβ3-mediated re-phosphorylation. Therefore, S.sanguis-bound IgG cross links FcγRIIA and initiates a signaling pathway that is down-regulated by PECAM-1-bound SHP-1. Subsequent engagement of αIIbβ3 leads to SHP-1 dephosphorylation permiting a second wave of signaling leading to TxA2 release and consequent platelet aggregation.

scholarly journals Role of GRK6 in the Regulation of Platelet Activation through Selective G Protein-Coupled Receptor (GPCR) Desensitization

2020 ◽  
Vol 21 (11) ◽  
pp. 3932 ◽  
Author(s):  
Preeti Kumari Chaudhary ◽  
Sanggu Kim ◽  
Youngheun Jee ◽  
Seung-Hun Lee ◽  
Kyung-Mee Park ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
G Protein ◽  
Platelet Activation ◽  
Functional Role ◽  
Thrombus Formation ◽  
Receptor Activation ◽  
G Protein Coupled ◽  
Gpcr Desensitization ◽  
Stimulation Of

Platelet G protein-coupled receptors (GPCRs) regulate platelet function by mediating the response to various agonists, including adenosine diphosphate (ADP), thromboxane A2, and thrombin. Although GPCR kinases (GRKs) are considered to have the crucial roles in most GPCR functions, little is known regarding the regulation of GPCR signaling and mechanisms of GPCR desensitization by GRKs in platelets. In this study, we investigated the functional role of GRK6 and the molecular basis for regulation of specific GPCR desensitization by GRK6 in platelets. We used GRK6 knockout mice to evaluate the functional role of GRK6 in platelet activation. Platelet aggregation, dense- and α-granule secretion, and fibrinogen receptor activation induced by 2-MeSADP, U46619, thrombin, and AYPGKF were significantly potentiated in GRK6−/− platelets compared to the wild-type (WT) platelets. However, collagen-related peptide (CRP)-induced platelet aggregation and secretion were not affected in GRK6−/− platelets. Interestingly, platelet aggregation induced by co-stimulation of serotonin and epinephrine which activate Gq-coupled 5HT2A and Gz-coupled α2A adrenergic receptors, respectively, was not affected in GRK6−/− platelets, suggesting that GRK6 was involved in specific GPCR regulation. In addition, platelet aggregation in response to the second challenge of ADP and AYPGKF was restored in GRK6−/− platelets whereas re-stimulation of the agonist failed to induce aggregation in WT platelets, indicating that GRK6 contributed to P2Y1, P2Y12, and PAR4 receptor desensitization. Furthermore, 2-MeSADP-induced Akt phosphorylation and AYPGKF-induced Akt, extracellular signal-related kinase (ERK), and protein kinase Cδ (PKCδ) phosphorylation were significantly potentiated in GRK6−/− platelets. Finally, GRK6−/− mice exhibited an enhanced and stable thrombus formation after FeCl3 injury to the carotid artery and shorter tail bleeding times, indicating that GRK6−/− mice were more susceptible to thrombosis and hemostasis. We conclude that GRK6 plays an important role in regulating platelet functional responses and thrombus formation through selective GPCR desensitization.

Fyn and Lyn phosphorylate the Fc receptor γ chain downstream of glycoprotein VI in murine platelets, and Lyn regulates a novel feedback pathway

Blood ◽  
2000 ◽  
Vol 96 (13) ◽  
pp. 4246-4253 ◽  
Author(s):  
Lynn S. Quek ◽  
Jean-Max Pasquet ◽  
Ingeborg Hers ◽  
Richard Cornall ◽  
Graham Knight ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Fc Receptor ◽  
Inhibitory Pathway ◽  
Functional Responses ◽  
Glycoprotein Vi ◽  
Granule Secretion ◽  
Activation Motif ◽  
Additional Role ◽  
Feedback Pathway

Abstract Activation of platelets by collagen is mediated by the complex glycoprotein VI (GPVI)/Fc receptor γ (FcRγ chain). In the current study, the role of 2 Src family kinases, Fyn and Lyn, in GPVI signaling has been examined using murine platelets deficient in one or both kinases. In the fyn−/−platelets, tyrosine phosphorylation of FcRγ chain, phopholipase C (PLC) activity, aggregation, and secretion are reduced, though the time of onset of response is unchanged. In the lyn−/−platelets, there is a delay of up to 30 seconds in the onset of tyrosine phosphorylation and functional responses, followed by recovery of phosphorylation and potentiation of aggregation and α-granule secretion. Tyrosine phosphorylation and aggregation in response to stimulation by collagen-related peptide is further attenuated and delayed in fyn−/−lyn−/−double-mutant platelets, and potentiation is not seen. This study provides the first genetic evidence that Fyn and Lyn mediate FcR immune receptor tyrosine-based activation motif phosphorylation and PLCγ2 activation after the ligation of GPVI. Lyn plays an additional role in inhibiting platelet activation through an uncharacterized inhibitory pathway.

scholarly journals Oxidation Impacts the Intracellular Signaling Machinery in Hematological Disorders

Antioxidants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 353
Author(s):  
Elena Tibaldi ◽  
Enrica Federti ◽  
Alessandro Matte ◽  
Iana Iatcenko ◽  
Anand B. Wilson ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Conformational Changes ◽  
Intracellular Signaling ◽  
Signal Transduction Pathways ◽  
Functional Connection ◽  
Intracellular Signaling Pathway ◽  
Hematological Disorders ◽  
Dynamic Coordination ◽  
Transduction Mechanisms

The dynamic coordination between kinases and phosphatases is crucial for cell homeostasis, in response to different stresses. The functional connection between oxidation and the intracellular signaling machinery still remains to be investigated. In the last decade, several studies have highlighted the role of reactive oxygen species (ROS) as modulators directly targeting kinases, phosphatases, and downstream modulators, or indirectly acting on cysteine residues on kinases/phosphatases resulting in protein conformational changes with modulation of intracellular signaling pathway(s). Translational studies have revealed the important link between oxidation and signal transduction pathways in hematological disorders. The intricate nature of intracellular signal transduction mechanisms, based on the generation of complex networks of different types of signaling proteins, revealed the novel and important role of phosphatases together with kinases in disease mechanisms. Thus, therapeutic approaches to abnormal signal transduction pathways should consider either inhibition of overactivated/accumulated kinases or homeostatic signaling resetting through the activation of phosphatases. This review discusses the progress in the knowledge of the interplay between oxidation and cell signaling, involving phosphatase/kinase systems in models of globally distributed hematological disorders.

Role of tyrosine kinase pathways in ETB receptor activation of NHE3

1996 ◽  
Vol 271 (3) ◽  
pp. C763-C771 ◽  
Author(s):  
T. S. Chu ◽  
H. Tsuganezawa ◽  
Y. Peng ◽  
A. Cano ◽  
M. Yanagisawa ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Focal Adhesion ◽  
Focal Adhesions ◽  
Integral Membrane Protein ◽  
Receptor Activation ◽  
Kinase C ◽  
Focal Adhesion Proteins ◽  
Etb Receptor

Endothelin-1 (ET-1) binding to ETB receptors increases the activity of the apical membrane Na+/H+ antiporter (NHE3) of renal proximal tubule and cultured OKP cells. In OKPETB6 cells, a clonal cell line of OKP cells that overexpresses ETB receptors, ET-1-induced increases in Na+/H+ antiporter activity are mediated 50% by Ca2(+)-dependent pathways and 50% by tyrosine kinase pathways. ET-1 induces tyrosine phosphorylation of proteins of 68, 110, 125, 130, and 210 kDa. ET-1-induced tyrosine phosphorylation is mediated by the ETB receptor and is not dependent on increases in cell Ca2+ or protein kinase C. The 68-, 110-, 125-, and 130-kDa phosphoproteins are cytosolic, whereas the 210-kDa phosphoprotein is an integral membrane protein. Immunoprecipitation studies showed that the 68-kDa protein is paxillin and the 125-kDa protein is p125FAK (focal adhesion kinase). Cytochalasin D, which disrupts focal adhesions, prevented ET-1-induced tyrosine phosphorylation of paxillin, p110, p125FAK, and p130 but did not prevent tyrosine phosphorylation of p210 and did not prevent ET-1-induced increases in Na+/H+ antiporter activity. Thus 50% of ETB receptor-induced Na+/H+ antiporter activation is mediated by tyrosine kinase pathways, possibly involving p210. ETB receptor activation also induces tyrosine phosphorylation of focal adhesion proteins, but this is not required for antiporter activation.

Role of guanine nucleotide-binding proteins, Giα3 and Gsα, in dopamine and thyrotropin-releasing hormone signal transduction: evidence for competition and commonality

1996 ◽  
Vol 148 (3) ◽  
pp. 447-455 ◽  
Author(s):  
R D Kineman ◽  
T W Gettys ◽  
L S Frawley
Keyword(s):  
Signal Transduction ◽  
G Proteins ◽  
Cell Cultures ◽  
Intracellular Signaling ◽  
Receptor Activation ◽  
Pituitary Cell ◽  
Thyrotropin Releasing Hormone ◽  
Female Rats ◽  
Releasing Hormone

Abstract It is clear that dopamine (DA) at high concentrations (>100 nmol/l) inhibits the release of prolactin (PRL). Paradoxically, this monoamine at low concentrations (<10 nmol/l) has also been shown to augment PRL secretion. One possible explanation for these divergent effects is that DA binds receptors capable of interacting with multiple G protein subtypes that recruit opposing intracellular signaling pathways within lactotropes. To identify G proteins which couple DA receptor activation to PRL secretion, we have selectively immunoneutralized the activity of Giα3 and Gsα in primary cultures of rat pituitaries and subsequently tested the ability of these cultures to respond to high and low dose DA. Specifically, permeabilized pituitary cell cultures from random-cycling female rats were treated with control immunoglobulins (IgGs; 50 μg/ml) purified from preimmune serum (PII) or IgGs directed against the C-terminal portion of Giα3 or Gsα. After immunoneutralization of these G proteins, cells were challenged with 10 or 1000 nmol Da/l and the relative amount of PRL released was assessed by reverse hemolytic plaque assay. Results were expressed as % of basal values and compared. Under control conditions (PII), 1000 nmol DA/l inhibited (61·4 ±7·6% of basal values; mean ± s.e.m.) while 10 nmol DA/l augmented (120·0 ± 7·0%) PRL release in five separate experiments. Treatment of cells with anti-Giα3 attenuated the inhibitory effect of high dose DA (87·3 ± 14·5%). However, elimination of Giα3 activity did not significantly alter the PRL stimulatory effect of 10 nmol DA/l (121·0 ± 5·2%). Interestingly, immunoneutralization of Gsα resulted in a reciprocal shift in the activity of the lower dose of DA from stimulatory to inhibitory (69·7 ± 7·3%) while combined treatment of anti-Giα3 and anti-Gsα abrogated the responsiveness of pituitary cell cultures to either DA treatment (1000 nmol/l, 70·7 ± 12·5% and 10 nmol/l, 87·5 ± 21·4%). These data reveal that ligand-activated DA receptors can interact with both Giα3 and Gsα. Elimination of the stimulatory component (Gsα) favors the DA receptor activation of the inhibitory pathway (Giα3) suggesting a competition between negative and positive intracellular signaling mechanisms in normal lactotropes. In addition to DA treatment, we also challenged permeabilized pituitary cells with 100 nmol thyrotropin-releasing hormone (TRH)/1 as a positive control for secretory integrity. As anticipated, TRH stimulated PRL release to 188·0±31·0% of basal values under control conditions. Unexpectedly, immunoneutralization of Gsα completely blocked the ability of TRH to induce PRL release (101·8 ± 12·0% This neutralizing effect was specific to Gsα in that blockade of Giα3 activity had no significant effect on TRH-stimulated PRL release (166·2 ± 13·1%). These data are the first to support a direct role of Gsα in TRH signal transduction within PRL-secreting cells. Journal of Endocrinology (1996) 148, 447–455

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