The Cardeza Foundation for Hematologic Research and the Department of Medicine, Thomas Jefferson University, Jefferson Medical College, Philadelphia, PA, USA.
Department of Human & Molecular Genetics, Baylor College of Medicine, Houston, TX, USA.
J Thromb Haemost. 2018 Dec;16(12):2501-2514. doi: 10.1111/jth.14318. Epub 2018 Nov 22.
Essentials The rs773902 SNP results in differences in platelet protease-activated receptor (PAR4) function. The functional consequences of rs773902 were analyzed in human platelets and stroke patients. rs773902 affects thrombin-induced platelet function, PAR4 desensitization, stroke association. Enhanced PAR4 Thr120 effects on platelet function are blocked by ticagrelor. SUMMARY: Background F2RL3 encodes protease-activated receptor (PAR) 4 and harbors an A/G single-nucleotide polymorphism (SNP) (rs773902) with racially dimorphic allelic frequencies. This SNP mediates an alanine to threonine substitution at residue 120 that alters platelet PAR4 activation by the artificial PAR4-activation peptide (PAR4-AP) AYPGKF. Objectives To determine the functional effects of rs773902 on stimulation by a physiological agonist, thrombin, and on antiplatelet antagonist activity. Methods Healthy human donors were screened and genotyped for rs773902. Platelet function in response to thrombin was assessed without and with antiplatelet antagonists. The association of rs773902 alleles with stroke was assessed in the Stroke Genetics Network study. Results As compared with rs773902 GG donors, platelets from rs773902 AA donors had increased aggregation in response to subnanomolar concentrations of thrombin, increased granule secretion, and decreased sensitivity to PAR4 desensitization. In the presence of PAR1 blockade, this genotype effect was abolished by higher concentrations of or longer exposure to thrombin. We were unable to detect a genotype effect on thrombin-induced PAR4 cleavage, dimerization, and lipid raft localization; however, rs773902 AA platelets required a three-fold higher level of PAR4-AP for receptor desensitization. Ticagrelor, but not vorapaxar, abolished the PAR4 variant effect on thrombin-induced platelet aggregation. A significant association of modest effect was detected between the rs773902 A allele and stroke. Conclusion The F2RL3 rs773902 SNP alters platelet reactivity to thrombin; the allelic effect requires P2Y , and is not affected by gender. Ticagrelor blocks the enhanced reactivity of rs773902 A platelets. PAR4 encoded by the rs773902 A allele is relatively resistant to desensitization and may contribute to stroke risk.
要点：rs773902 导致血小板蛋白酶激活受体 (PAR4) 功能的差异。在人类血小板和中风患者中分析了 rs773902 的功能后果。rs773902 影响凝血酶诱导的血小板功能、PAR4 脱敏、中风关联。增强的 PAR4 Thr120 对血小板功能的影响被替格瑞洛阻断。
摘要：背景 F2RL3 编码蛋白酶激活受体 (PAR) 4，并带有一个与种族相关的单核苷酸多态性 (SNP) (rs773902)，其等位基因频率不同。该 SNP 介导丙氨酸到苏氨酸的取代，该取代改变了人工 PAR4 激活肽 (PAR4-AP) AYPGKF 对血小板 PAR4 的激活。目的确定 rs773902 对生理激动剂凝血酶刺激和抗血小板拮抗剂活性的功能影响。方法筛选健康的人类供体并对 rs773902 进行基因分型。评估血小板对凝血酶的反应而无需抗血小板拮抗剂。评估 rs773902 等位基因与中风的关联在中风遗传学网络研究中。
结果与 rs773902 GG 供体相比，rs773902 AA 供体的血小板对亚纳摩尔浓度的凝血酶的聚集反应增加，颗粒分泌增加，对 PAR4 脱敏的敏感性降低。在用 PAR1 阻断的情况下，这种基因型效应被更高浓度的凝血酶或更长时间的暴露所消除。我们无法检测到基因型对凝血酶诱导的 PAR4 切割、二聚化和脂筏定位的影响；然而，rs773902 AA 血小板对受体脱敏需要三倍高浓度的 PAR4-AP。替格瑞洛，但不是 vorapaxar，消除了 PAR4 变体对凝血酶诱导的血小板聚集的影响。检测到 rs773902 A 等位基因与中风之间存在中度效应的显著关联。结论 F2RL3 rs773902 SNP 改变了血小板对凝血酶的反应性；等位基因效应需要 P2Y ，不受性别影响。替格瑞洛阻断 rs773902 A 血小板的反应性增强。由 rs773902 A 等位基因编码的 PAR4 对脱敏相对耐药，可能与中风风险有关。
