Department of Life Sciences, Faculty of Science and Engineering, Manchester Metropolitan University, Manchester M1 5GD, UK.
Discovery and Translational Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds LS2 3AA, UK.
Int J Mol Sci. 2024 Jul 11;25(14):7606. doi: 10.3390/ijms25147606.
A key step in platelet production is the migration of megakaryocytes to the vascular sinusoids within the bone marrow. This homing is mediated by the chemokine CXCL12 and its receptor CXCR4. CXCR4 is also a positive regulator of platelet activation and thrombosis. Pim-1 kinase has been shown to regulate CXCR4 signalling in other cell types, and we have previously described how Pim kinase inhibitors attenuate platelet aggregation to CXCL12. However, the mechanism by which Pim-1 regulates CXCR4 signalling in platelets and megakaryocytes has yet to be elucidated. Using human platelets, murine bone marrow-derived megakaryocytes, and the megakaryocyte cell line MEG-01, we demonstrate that pharmacological Pim kinase inhibition leads to reduced megakaryocyte and platelet function responses to CXCL12, including reduced megakaryocyte migration and platelet granule secretion. Attenuation of CXCL12 signalling was found to be attributed to the reduced surface expression of CXCR4. The decrease in CXCR4 surface levels was found to be mediated by rapid receptor internalisation, in the absence of agonist stimulation. We demonstrate that pharmacological Pim kinase inhibition disrupts megakaryocyte and platelet function by reducing constitutive CXCR4 surface expression, decreasing the number of receptors available for agonist stimulation and signalling. These findings have implications for the development and use of Pim kinase inhibitors for the treatment of conditions associated with elevated circulating levels of CXCL12/SDF1α and increased thrombotic risk.
血小板生成的一个关键步骤是巨核细胞向骨髓窦状隙的迁移。这种归巢是由趋化因子 CXCL12 和其受体 CXCR4 介导的。CXCR4 也是血小板激活和血栓形成的正调节剂。已经表明 Pim-1 激酶可以调节其他细胞类型中的 CXCR4 信号，我们之前描述了 Pim 激酶抑制剂如何减弱 CXCL12 诱导的血小板聚集。然而，Pim-1 调节血小板和巨核细胞中 CXCR4 信号的机制尚未阐明。使用人血小板、鼠骨髓来源的巨核细胞和巨核细胞系 MEG-01，我们证明了药理 Pim 激酶抑制导致对 CXCL12 的巨核细胞和血小板功能反应减弱，包括巨核细胞迁移和血小板颗粒分泌减少。发现 CXCL12 信号的衰减归因于 CXCR4 的表面表达减少。发现 CXCR4 表面水平的降低是由没有激动剂刺激的快速受体内化介导的。我们证明药理 Pim 激酶抑制通过减少组成性 CXCR4 表面表达、减少可用于激动剂刺激和信号的受体数量来破坏巨核细胞和血小板功能。这些发现对于开发和使用 Pim 激酶抑制剂治疗与循环 CXCL12/SDF1α 水平升高和血栓形成风险增加相关的疾病具有重要意义。
