Paxillin family members function as Csk-binding proteins that regulate Lyn activity in human and murine platelets
Paxillin family members function as Csk-binding proteins that regulate Lyn activity in human and murine platelets
复制标题
DOI：
10.1042/bj20061618
复制
发表时间：
2007-04-15
影响因子：
4.1
通讯作者：
Newman, Debra K.
中科院分区：
文献类型：
--
作者：
Rathore, Vipul B.;Okada, Masato;Newman, Debra K.
SFK（Src家族激酶）在止血中对血小板功能有重要贡献。SFK活性受Csk（C-末端Src激酶）控制，Csk磷酸化SFK上的C-末端酪氨酸残基，导致SFK活性抑制。Csk被酪氨酸磷酸化的Csk结合蛋白募集到SFK活性位点。帕西林一种多结构域衔接蛋白，已显示作为Csk结合蛋白并在生长因子信号传导过程中抑制Src活性。人血小板表达桩蛋白家族的成员Hic-5;然而，其作为Csk结合蛋白的能力尚未被表征。我们试图鉴定和表征桩蛋白家族成员在血小板活化过程中作为Csk结合蛋白的能力。我们发现，鼠和人血小板不同的桩蛋白家族成员表达的补充。人血小板表达Hic-5，而鼠血小板除了表达Hic-5之外还表达桩蛋白和亮帕素。在聚集的人血小板中，Hic-5被酪氨酸磷酸化，并通过其SH 2结构域募集Csk。然而，在聚集小鼠血小板，Csk优先结合桩蛋白，即使桩蛋白和HIC-5都大量存在，并成为酪氨酸磷酸化。SFK林恩，而不是Src或Fyn，与静息和聚集的人类和小鼠血小板中的桩蛋白家族成员相关。然而，林恩的C-末端抑制性酪氨酸残基仅在血小板聚集后被磷酸化，这与Csk以依赖于先前α（IIb）β（3）接合的方式募集至桩蛋白和/或Hic-5相一致。这些观察结果支持了这样的观点，即Hic-5和桩蛋白作为聚集血小板中SFK的负反馈调节剂起作用，并且当两者都存在时，桩蛋白优先使用。
SFKs (Src family kinases) contribute importantly to platelet function in haemostasis. SFK activity is controlled by Csk (C-terminal Src kinase), which phosphorylates a C-terminal tyrosine residue on SFKs, resulting in inhibition of SFK activity. Csk is recruited to sites of SFK activity by tyrosine-phosphorylated Csk-binding proteins. Paxillin. a multidomain adaptor protein, has been shown to act as a Csk-binding protein and to inhibit Src activity during growth factor signalling. Human platelets express Hic-5, a member of the paxillin family; however, its ability to act as a Csk-binding protein has not been characterized. We sought to identify and characterize the ability of paxillin family members to act as Csk-binding proteins during platelet activation. We found that murine and human platelets differ in the complement of paxillin family members expressed. Human platelets express Hic-5, whereas murine platelets express paxillin and leupaxin in addition to Hic-5. In aggregating human platelets, Hic-5 was tyrosine phosphorylated and recruited Csk via its SH2 domains. In aggregating murine platelets, however, Csk bound preferentially to paxillin, even though both paxillin and Hic-5 were abundantly present and became tyrosine phosphorylated. The SFK Lyn, but not Src or Fyn, was associated with paxillin family members in resting and aggregated human and murine platelets. Lyn, however, was phosphorylated on its C-terminal inhibitory tyrosine residue only following platelet aggregation, which was coincident with recruitment of Csk to paxillin and/or Hic-5 in a manner dependent on prior alpha(IIb)beta(3) engagement. These observations support the notion that Hic-5 and paxillin function as negative feedback regulators of SFKs in aggregated platelets and that, when both are present, paxillin is preferentially used.