Mendelsohn M E, Zhu Y, O'Neill S
Department of Medicine, Brigham and Women's Hospital, Boston, MA.
Proc Natl Acad Sci U S A. 1991 Dec 15;88(24):11212-6. doi: 10.1073/pnas.88.24.11212.
Thrombin plays a critical role in platelet activation, hemostasis, and thrombosis. Cellular activation by thrombin leads to the phosphorylation of multiple proteins, most of which are unidentified. We have characterized several 29-kDa proteins that are rapidly phosphorylated following exposure of intact human platelets to thrombin. A murine monoclonal antibody raised to an unidentified estrogen receptor-related 29-kDa protein selectively recognized these proteins as well as a more basic, unphosphorylated 27-kDa protein. Cellular activation by thrombin led to a marked shift in the proportion of protein from the 27-kDa unphosphorylated form to the 29-kDa phosphoprotein species. Using this antibody, we isolated and sequenced a human cDNA clone encoding a protein that was identical to the mammalian 27-kDa heat shock protein (HSP27), a protein of uncertain function that is known to be phosphorylated to several forms and to be transcriptionally induced by estrogen. The 29-kDa proteins were confirmed to be phosphorylated forms of HSP27 by immunoprecipitation studies. Thus, the "estrogen receptor-related protein" is HSP27, and the three major 29-kDa proteins phosphorylated in thrombin-activated platelets are forms of HSP27. These data suggest a role for HSP27 in the signal transduction events of platelet activation.
凝血酶在血小板激活、止血和血栓形成过程中起着关键作用。凝血酶引起的细胞激活会导致多种蛋白质磷酸化，其中大多数蛋白质身份不明。我们已鉴定出几种29 kDa的蛋白质，在完整的人血小板暴露于凝血酶后会迅速磷酸化。一种针对身份不明的雌激素受体相关29 kDa蛋白质产生的鼠单克隆抗体，能选择性识别这些蛋白质以及一种更碱性的未磷酸化27 kDa蛋白质。凝血酶引起的细胞激活导致蛋白质比例从27 kDa未磷酸化形式显著转变为29 kDa磷蛋白形式。利用这种抗体，我们分离并测序了一个人cDNA克隆，该克隆编码的蛋白质与哺乳动物27 kDa热休克蛋白（HSP27）相同，HSP27是一种功能不明的蛋白质，已知可磷酸化为多种形式并受雌激素转录诱导。通过免疫沉淀研究证实，29 kDa蛋白质是HSP27的磷酸化形式。因此，“雌激素受体相关蛋白”就是HSP27，在凝血酶激活的血小板中磷酸化的三种主要29 kDa蛋白质是HSP27的不同形式。这些数据表明HSP27在血小板激活的信号转导事件中发挥作用。
