Tyrosine phosphorylation of cortactin associated with Syk accompanies thromboxane analogue-induced platelet shape change
Tyrosine phosphorylation of cortactin associated with Syk accompanies thromboxane analogue-induced platelet shape change
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DOI：
10.1074/jbc.274.33.23610
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发表时间：
1999-08-13
影响因子：
4.8
通讯作者：
Maclouf, J
中科院分区：
文献类型：
--
作者：
Gallet, C;Rosa, JP;Maclouf, J
血栓素A(2)(TXA(2))是一种有效的血管收缩和血小板激动剂。药理学研究已在人的血小板中定义了两类血栓素受体：与激动剂1S-(1，2(5Z)，3-(1E，3S)，4)-7-3-(3-羟基-4-(4‘-碘苯氧基)-1-丁烯基)-7-氧双环-2.2.1-庚烷-2-基-5-庚烯酸(I-BOP)高亲和力结合的部位支持血小板形状的改变，而与拮抗剂GR 32191不可逆结合的低亲和力部位则转导血小板聚集。由于参与血小板聚集的信号转导机制尚未阐明，很少有结果涉及与血小板形状变化无关的GPIIb/IIIa结合。为了阐明两类药物结合部位在形状变化中的各自作用，分别用低浓度的I-BOP和高浓度的I-BOP孵育或经GR 32191预处理后的I-BOP或用低浓度的8-表前列腺素F(2)α激活。在这三种情况下，细胞骨架蛋白Cortactin的80/85 kDa双重体的蛋白酪氨酸磷酸化被快速刺激，Cortactin的酪氨酸磷酸化与形状改变的发生呈动力学相关，这些生化和形态事件都被TP拮抗剂SQ 29548抑制，表明信号的特异性。由于酪氨酸激酶Syk在血小板激活的早期被激活，我们探讨了Cortactin在TXA(2)诱导的血小板形状改变中是Syk的潜在底物的可能性。在低浓度的I-BOP刺激下，P72Syk的磷酸化和激酶活性发生在血小板变形过程中，而且Cortactin与Syk相关，并且这种联系随着磷酸化水平的升高而增强。这些数据表明，Gr蛋白偶联TXA(2)高亲和力受体到蛋白酪氨酸激酶Syk的新途径，该蛋白与Cortactin在非常早期的血小板激活步骤有关。
Thromboxane A(2) (TxA(2)) is a potent vasoconstrictor and platelet agonist. Pharmacological studies have defined two classes of thromboxane receptors (TPs) in human platelets; sites that bind the agonist 1S-(1,2(5Z),3-(1E,3S),4)-7- 3-(3-hydroxy-4-(4'-iodophenoxy)-1-butenyl)- 7-oxabicyclo-2.2.1-heptan-2-yl-5-heptenoic acid (I-BOP) with high affinity support platelet shape change, whereas low affinity sites that bind irreversibly the antagonist GR 32191 transduce platelet aggregation. As the mechanisms of signal transduction involved in platelet aggregation bean to be elucidated, few results concern those involved in platelet shape change, which is independent of the engagement of GPIIb/IIIa, To elucidate the respective role of the two classes of pharmacological binding sites of TPs in shape change, platelets were incubated with I-BOP at low concentrations or stimulated by I-BOP at high concentrations after pretreatment with GR 32191 or activated with low concentrations of 8-epi-prostaglandin F(2)alpha. Under these three conditions, there is a rapid stimulation of protein tyrosine phosphorylation of the 80/85-kDa doublet identified as the cytoskeletal protein cortactin, Tyrosine phosphorylation of cortactin is kinetically correlated with the occurrence of shape change, These biochemical and morphological events are both inhibited by SQ 29548, a TP antagonist, indicating the specificity of the signal.Since tyrosine kinase Syk was activated early during platelet activation, we examined the possibility that cortactin is a potential substrate of Syk in TxA(2)-induced platelet shape change. p72 Syk phosphorylation and kinase activity took place during the period when platelets were changing shape upon low concentrations of I-BOP stimulation, Furthermore, cortactin was associated with Syk, and this association increases along with the level of phosphorylation. These data suggest a novel pathway for a Gr protein coupled TxA(2) high affinity receptor to the protein-tyrosine kinase Syk, which is associated with cortactin in the very early steps of platelet activation.