scholarly journals Calcium store depletion in dimethyl BAPTA-loaded human platelets increases protein tyrosine phosphorylation in the absence of a rise in cytosolic calcium

1994 ◽  
Vol 79 (2) ◽  
pp. 269-272 ◽  
Author(s):  
P Sargeant ◽  
RW Farndale ◽  
SO Sage
Keyword(s):  
Tyrosine Phosphorylation ◽  
Cytosolic Calcium ◽  
Human Platelets ◽  
Protein Tyrosine Phosphorylation ◽  
Calcium Store ◽  
Protein Tyrosine ◽  
Store Depletion

scholarly journals The effect of calcium-store depletion and refilling with various bivalent cations on tyrosine phosphorylation and Mn2+ entry in fura-2-loaded human platelets

1994 ◽  
Vol 303 (2) ◽  
pp. 337-339 ◽  
Author(s):  
S Jenner ◽  
R W Farndale ◽  
S O Sage
Keyword(s):  
Phosphatase Activity ◽  
Tyrosine Phosphorylation ◽  
Tyrosine Phosphatase ◽  
Human Platelets ◽  
Calcium Store ◽  
Protein Tyrosine ◽  
Fura 2 ◽  
Store Depletion ◽  
Bivalent Cations

To investigate the possible involvement of tyrosine phosphorylation in the process of store-regulated Ca2+ entry, ionomycin (in the presence of EGTA) was used to deplete the intracellular Ca2+ stores of fura-2-loaded human platelets, and the effect of refilling with Ca2+, Ba2+ or Sr2+ evaluated. Depletion of the intracellular Ca2+ stores resulted in an increase in protein tyrosine phosporylation. This increase is reversed when the stores were refilled in Ca2+ or Sr2+, but not Ba2+. Refilling of the stores with Ca2+ or Sr2+, but not Ba2+, suppressed Mn2+ entry. These findings support the hypothesis that tyrosine phosphorylation plays a role in mediating store-regulated Ca2+ entry in human platelets and provides evidence for tyrosine phosphatase activity regulated by the Ca2+ content of the intracellular stores.

Protein-Tyrosine Phosphorylation and p72 syk Activation in Human Platelets Stimulated with Collagen Is Dependent upon Glycoprotein Ia/IIa and Actin Polymerization

1996 ◽  
Vol 75 (04) ◽  
pp. 648-654 ◽  
Author(s):  
Naoki Asazuma ◽  
Yutaka Yatomi ◽  
Yukio Ozaki ◽  
Ruomei Qi ◽  
Kenji Kuroda ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Actin Polymerization ◽  
Human Platelets ◽  
Dependent Manner ◽  
Protein Tyrosine Phosphorylation ◽  
Concentration Dependent Manner ◽  
Protein Tyrosine ◽  
Collagen Receptors ◽  
Fibrinogen Binding ◽  
Adp Release

SummaryIn human platelets treated with acetylsalicylic acid, collagen induced protein-tyrosine-phosphorylation of several proteins. The major 75 kDa band included cortactin and autophosphorylated p72 syk . p72 syk activity rapidly increased upon collagen stimulation, whereas p60c-src activation was below detectable levels. A combination of inhibitors to remove the effects of extracellular and intracellular Ca2+, released ADP, and fibrinogen binding to GPIIb/IIIa delayed and attenuated the major 75 kDa band. By contrast, p72 syk activation was not inhibited by these treatments. Cytochalasin D completely inhibited protein tyrosine phosphorylation and p72 syk activation. It also potently inhibited aggregation and [Ca2+]i elevation. Anti-GPMIa/IIa MoAb in a concentration-dependent manner partially attenuated protein tyrosine phosphorylation and p72 syk activation. Its inhibitory effects on intracellular Ca2+ mobilization, release of intracellular granule contents, and aggregation also were partial. No tyrosine kinase activity was coprecipitated with GPIa/IIa. These results suggest that p72 syk activation lies upstream of protein tyrosine phosphorylation, Ca2+ mobilization, ADP release, thromboxane A2 production and aggregation. GPIa/IIa plays a key role in p72 syk activation induced by collagen, but other collagen receptors may work in synergy to fully activate p72 syk . Actin polymerization is a prerequisite for both p72 syk activation and other intracellular signal transduction pathways.

Lysophosphatidic acid induces protein tyrosine phosphorylation in the absence of phospholipase C activation in human platelets

Platelets ◽  
1997 ◽  
Vol 8 (2) ◽  
pp. 181-188
Author(s):  
M. Torti ◽  
E. Tolnai Festetics ◽  
A. Bertoni ◽  
R. Moratti ◽  
C. Balduini ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Tyrosine Phosphorylation ◽  
Lysophosphatidic Acid ◽  
Human Platelets ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine

Lysophosphatidic acid induces protein tyrosine phosphorylation in the absence of phospholipase C activation in human platelets

Platelets ◽  
1997 ◽  
Vol 8 (2) ◽  
pp. 181-187
Author(s):  
M. Torti ◽  
E. Tolnai Festetics ◽  
A. Bertoni ◽  
R. Moratti ◽  
C. Balduini ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Tyrosine Phosphorylation ◽  
Lysophosphatidic Acid ◽  
Human Platelets ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine

lonomycin-stimulated Arachidonic Acid Release in Human Platelets: a Role for Protein Kinase C and Tyrosine Phosphorylation

1996 ◽  
Vol 76 (02) ◽  
pp. 248-252 ◽  
Author(s):  
Philip G Hargreaves ◽  
Susanne Jenner ◽  
Janet E Merritt ◽  
Stewart O Sage ◽  
Richard W Farndale
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Tyrosine Phosphorylation ◽  
Human Platelets ◽  
Protein Tyrosine Phosphorylation ◽  
Arachidonic Acid Release ◽  
Protein Tyrosine ◽  
Kinase C ◽  
Acid Release

SummaryCollagen (10-90 Μg/ml) and ionomycin (1 ΜM; a calcium iono-phore) each evoked rises in intracellular free calcium, protein kinase C activity and arachidonic acid release in human platelets, and as previously demonstrated for collagen, ionomycin (1 p,M) stimulated protein tyrosine phosphorylation. However, at lower concentrations (60 and 250 nM) ionomycin selectively mobilised calcium. Ro31-8220 (a selective inhibitor of protein kinase C) inhibited (by 50%) ionomycin-stimulated arachidonic acid release. Genistein (an inhibitor of protein tyrosine kinases) also reduced by 50% ionomycin-stimulated arachidonic acid release. In combination, genistein and Ro31-8220 abolished ionomycin-stimulated arachidonic acid release. These findings show 1) that a rise in calcium is not sufficient, and 2) the activation of both protein kinase C and protein tyrosine phosphorylation is necessary, for full ionomycin-stimulated arachidonic acid release in human platelets.

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