Thromb Haemost 1996; 75(04): 648-654
DOI: 10.1055/s-0038-1650337
Original Article
Schattauer GmbH Stuttgart

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

Naoki Asazuma
The Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan
,
Yutaka Yatomi
The Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan
,
Yukio Ozaki
The Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan
,
Ruomei Qi
The Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan
,
Kenji Kuroda
The Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan
,
Kaneo Satoh
The Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan
,
Shoji Kume
The Department of Clinical and Laboratory Medicine, Yamanashi Medical University, Yamanashi, Japan
› Author Affiliations
Further Information

Publication History

Received 02 August 1995

Accepted after revision 19 December 1995

Publication Date:
10 July 2018 (online)

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Summary

In 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.