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  • 學位論文

JAK2參與血小板活化之機轉探討

The signal of JAK2 regulation of platelets activation

指導教授 : 許準榕

摘要


Janus kinase (JAKs) 是細胞質內(cytoplasm)具有tyrosine kinase 活性的蛋白質,通常與細胞膜表面的cytokine receptor結合在一起。在哺乳類中,總共有四個JAK家族成員,分別是:JAK1、JAK2、JAK3以及TYK2。當受質(ligand)與細胞膜表面的受器(receptor)結合後便會活化JAKs,JAKs活化之後會參與細胞增生(proliferation)、細胞凋亡(apoptosis),也會參與造血作用(hematopoiesis)等等。 在許多不同的細胞中,JAK2都有參與不同的調控機制,例如:在血管平滑肌細胞(vascular smooth muscle cells)中,血小板衍生物生長因子(platelet-derived growth factor-BB)會透過活化JAK2而調控血管平滑肌細胞的移動性(motility)。因此本研究主要是要探討由血小板刺激劑造成血小板活化時,JAK2在其中扮演的角色為何。 本研究主要是利用JAK2的專一性抑制劑AG490來測試JAK2是否會調控血小板的活化,由實驗結果顯示,AG490在濃度25-50 μM,對於collagen 及 arachidonic acid (AA)引起的人類血小板凝集反應及鈣離子的流動會有抑制的作用。而測定血小板內PKC活性的實驗可以發現AG490 (25-50 M)可以抑制由collagen所活化的47 kDa的蛋白質磷酸化,且呈現濃度相關的抑制作用;AG490 (25-50 M)也會明顯抑制由collagen所活化的Akt、JNKs及STAT3的磷酸化。由上述的實驗結果可以證實,AG490 抑制血小板活性的作用會涉及下列路徑:AG490會經由調控PKC這條路徑來進一步抑制鈣離子的流動及血小板的凝集作用;AG490也會經由調控Akt、JNK2及STAT3的磷酸化來影響血小板凝集。未來可以藉由抑制JAK2的活性,做為一個研究標的來治療心血管方面的疾病。

並列摘要


Janus kinase (JAK) is a tyrosine kinase protein in cytoplasm; it's usually binding with cytokine receptor at the surface of cell membrane. There are four JAKs in mammalian: JAK1, JAK2, JAK3 and TYK2. When ligands bind to the receptor at the cell membrane, JAKs will be activated, this reaction participates in proliferation, apoptosis and hematopoiesis. In various kinds of cells, JAK2 is involved in different mechanisms. For instance, in vascular smooth muscle cells (VSMCs), the platelet-derived growth factor-BB (PDGF-BB) can induce VSMCs motility via activating JAK2. According to these reasons, I want to study and to know the role of JAK2 that regulates platelet activation stimulated by platelet inducers. In our study, we use JAK2 specific inhibitor, AG490, to test whether JAK2 can regulate platelet activation. We found that collagen (1 柰/ml) and arachidonic acid (AA) (60 M)-induced washed human platelet aggregation and calcium mobilization can be inhibited by AG490. Nervertheless, when stimulated by collagen (1 柰/ml), the phosphorylation of a 47KDa protein can be inhibited by AG490 via a dose-dependent reaction. The phosphorylation of 47 kDa proteins is a marker of protein kinase C activation which can be triggered by collagen. We also found that the phosphorylation of Akt 、JNK2 and STAT3, which is stimulated by collagen (1 柰/ml) can be inhibited by AG490 (25-50 M). In conclusion, our study suggested that, the mechanism of AG490 in anti-platelet activity may be involved in the following: (I) AG490 may regulate PKC pathway to inhibit the intracellular calcium mobilization and platelet aggregation. (II) AG490 can regulate the phosphorylation of Akt, JNKs and STAT3 to inhibit platelet aggregation. Hence, JAK2 may be a target in treating pathological disorder associated with cardiovascular disease.

並列關鍵字

Janus kinase2 AG490 platelet activation

參考文獻


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