Background: PCTP (phosphatidylcholine transfer protein) regulates the intermembrane transfer of phosphatidylcholine. Higher platelet PCTP expression is associated with increased platelet responses on activation of protease-activated receptor 4 thrombin receptors noted in black subjects compared with white subjects. Little is known about the regulation of platelet PCTP. Haplodeficiency of RUNX1, a major hematopoietic transcription factor, is associated with thrombocytopenia and impaired platelet responses on activation. Platelet expression profiling of a patient with a RUNX1 loss-of-function mutation revealed a 10-fold downregulation of the PCTP gene compared with healthy controls.

Methods: We pursued the hypothesis that PCTP is regulated by RUNX1 and that PCTP expression is correlated with cardiovascular events. We studied RUNX1 binding to the PCTP promoter using DNA-protein binding studies and human erythroleukemia cells and promoter activity using luciferase reporter studies. We assessed the relationship between RUNX1 and PCTP in peripheral blood RNA and PCTP and death or myocardial infarction in 2 separate patient cohorts (587 total patients) with cardiovascular disease.

Results: Platelet PCTP protein in the patient was reduced by ≈50%. DNA-protein binding studies showed RUNX1 binding to consensus sites in ≈1 kB of PCTP promoter. PCTP expression was increased with RUNX1 overexpression and reduced with RUNX1 knockdown in human erythroleukemia cells, indicating that PCTP is regulated by RUNX1. Studies in 2 cohorts of patients showed that RUNX1 expression in blood correlated with PCTP gene expression; PCTP expression was higher in black compared with white subjects and was associated with future death/myocardial infarction after adjustment for age, sex, and race (odds ratio, 2.05; 95% confidence interval 1.6–2.7; P<0.0001). RUNX1 expression is known to initiate at 2 alternative promoters, a distal P1 and a proximal P2 promoter. In patient cohorts, there were differential effects of RUNX1 isoforms on PCTP expression with a negative correlation in blood between RUNX1 expressed from the P1 promoter and PCTP expression.

Conclusions: PCTP is a direct transcriptional target of RUNX1. PCTP expression is associated with death/myocardial infarction in patients with cardiovascular disease. RUNX1 regulation of PCTP may play a role in the pathogenesis of platelet-mediated cardiovascular events.

背景： PCTP（磷脂酰胆碱转移蛋白）调节磷脂酰胆碱的跨膜转移。与白人受试者相比，黑人受试者中发现较高的血小板PCTP表达与血小板活化蛋白酶激活受体4凝血酶受体活化后的血小板反应增加有关。关于血小板PCTP的调控知之甚少。RUNX1是主要的造血转录因子，其单倍型缺乏与血小板减少和激活时血小板反应受损有关。与健康对照组相比，具有RUNX1功能丧失突变的患者的血小板表达谱显示PCTP基因下调了10倍。

方法：我们提出了这样一种假设，即PCTP受RUNX1调节，并且PCTP的表达与心血管事件相关。我们使用DNA-蛋白质结合研究和人红血球细胞研究了RUNX1与PCTP启动子的结合，并使用萤光素酶报告基因研究了启动子的活性。我们评估了两个独立的心血管病患者队列（共587例患者）中外周血RNA和PCTP中RUNX1和PCTP与死亡或心肌梗死之间的关系。

结果：患者的血小板PCTP蛋白降低了约50％。DNA-蛋白质结合研究表明，RUNX1与PCTP启动子的约1 kB共有位点结合。在人红白血病细胞中，PCTP表达随RUNX1过表达而增加，而由于RUNX1敲低而降低，这表明PCTP受RUNX1调节。在2个患者队列中的研究表明，血液中RUNX1的表达与PCTP基因的表达相关。PCTP黑人的表达高于白人，并且与年龄，性别和种族调整后的未来死亡/心肌梗塞有关（比值比为2.05； 95％的置信区间为1.6-2.7；P <0.0001）。已知RUNX1表达起始于2个替代启动子，即远端P1和近端P2启动子。在患者队列中，RUNX1亚型对PCTP表达有差异作用，血液中从P1启动子表达的RUNX1与PCTP表达之间呈负相关。

结论： PCTP是RUNX1的直接转录靶标。PCTP表达与心血管疾病患者的死亡/心肌梗死有关。PCTP的RUNX1调节可能在血小板介导的心血管事件的发病机理中起作用。