AGGREGATION-DEPENDENT SIGNALING IN HUMAN PLATELETS IS SENSITIVE TO PROTEIN SERINE/THREONINE PHOSPHATASE INHIBITORS

被引:22
作者
HOYT, CH [1 ]
LEREA, KM [1 ]
机构
[1] NEW YORK MED COLL,DEPT ANAT & CELL BIOL,VALHALLA,NY 10595
关键词
D O I
10.1021/bi00029a033
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
When platelets are stimulated by the addition of thrombin, a series of temporally linked signaling events are initiated. Some of the early events are needed to engage the integrin glycoprotein (GP) IIb-IIIa in a high-affinity state. This in turn leads to aggregation, which initiates a wave of events distinct from those triggered by thrombin. Platelet responses are sensitive to protein serine/threonine phosphatase inhibitors, but which events are dependent on protein phosphatase activity is not known. In the present studies, the effect of the phosphatase inhibitor calyculin A on aggregation-induced signaling was examined. The addition of 0.2 unit/mL thrombin caused aggregation-dependent redistribution of cytoskeletal proteins (actin binding protein, talin, vinculin, and alpha-actinin), glycoproteins (GPIIb-IIIa, PECAM), and signaling molecules (PI3-kinase, pp60(c-src)) to the cytoskeletal fraction of platelets. Addition of 1-2 mu M calyculin A blocked the ability of 0.2 unit/mL thrombin to induce aggregation and the association of these molecules with the cytoskeleton. Aggregation (60-80% of control) was restored if 1 unit/mL thrombin was added, but there was no corresponding redistribution of actin binding protein, talin, vinculin, alpha-actinin, GPIIb-IIIa, PECAM, PD-kinase, and pp60(c-src) to the cytoskeleton. Treatment of platelets with calyculin A resulted in an increase in the phosphorylation state of a membrane skeletal protein of 50 kDa. These data strongly suggest that platelet aggregation is dissociable from aggregation-induced signaling, which is dependent on type 1 and 2A phosphatase activities.
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页码:9565 / 9570
页数:6
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