scholarly journals Wortmannin inhibits store-mediated calcium entry and protein tyrosine phosphorylation in human platelets

FEBS Letters ◽  
1996 ◽  
Vol 381 (3) ◽  
pp. 249-251 ◽  
Author(s):  
Susanne Jenner ◽  
Richard W. Farndale ◽  
Stewart O. Sage
Keyword(s):  
Tyrosine Phosphorylation ◽  
Human Platelets ◽  
Calcium Entry ◽  
Protein Tyrosine Phosphorylation ◽  
Protein Tyrosine

scholarly journals Signal transduction mechanisms involved in in vitro ram sperm capacitation

Reproduction ◽  
2006 ◽  
Vol 132 (5) ◽  
pp. 721-732 ◽  
Author(s):  
Patricia Grasa ◽  
José Álvaro Cebrián-Pérez ◽  
Teresa Muiño-Blanco
Keyword(s):  
Tyrosine Phosphorylation ◽  
Calcium Influx ◽  
Calcium Entry ◽  
Calcium Entry Blocker ◽  
Protein Tyrosine Phosphorylation ◽  
Sperm Capacitation ◽  
Protein Tyrosine ◽  
Entry Blocker ◽  
Ram Sperm

We validate the chlortetracycline (CTC) technique for the evaluation of capacitation and acrosome reaction-like changes in ram sperm, carrying out a double estimation of the acrosome status after treatment with lysophosphatidylcholine, using fluorescein isocyanate (FITC)-RCA/ethidium homodimer 1 (EthD-1) and CTC/EthD-1. Highly consistent results and a positive correlation between the results of acrosome-reacted sperm evaluated with both techniques were obtained. In this study, we evaluate the effects of ram sperm capacitation of BSA, Ca2+, NaHCO3and cAMP agonists and their influence on the associated protein tyrosine phosphorylation. We found a time-dependent increase in capacitation related to protein tyrosine phosphorylation, either in the absence or the presence of BSA. The addition of an increasing concentration of cholesterol to samples containing BSA did not influence results. The effect of bicarbonate was concentration-dependent, with a significantly lowered value of non-capacitated sperm in the presence 18 and 25 mM. The addition of extracellular calcium did not significantly increase either the proportion of capacitated sperm or the protein tyrosine phosphorylation signalling, although a significantly higher value of acrosome-reacted sperm was found in samples containing 4 mM Ca2+. cAMP agonists increased capacitated sperm and protein tyrosine phosphorylation signalling. The inhibition of protein kinase A by H-89 caused a decrease in sperm capacitation. Addition of a calcium-entry blocker (Verapamil; Sigma) did not influence results, which suggests that the calcium entry blocker was unable to inhibit the calcium influx associated with capacitation in ram sperm. Our findings might benefit our understanding of the biochemical mechanisms involved in mammalian sperm capacitation and ultimately, fertility.

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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