Chronic Disease Research Institute, Department of Nutrition and Food Hygiene, Zhejiang University School of Public Health, 866 Yu-Hang-Tang Road, Hangzhou, 310058, China.
Department of Pharmacology, School of Basic Medical Sciences, Guizhou Medical University, Guiyang, Guizhou, China.
J Transl Med. 2021 May 10;19(1):201. doi: 10.1186/s12967-021-02756-y.
Due to mTOR (mammalian/mechanistic target of rapamycin) gene-loss mice die during embryonic development, the role of mTOR in platelets has not been evaluated using gene knockout technology.
A mouse model with megakaryocyte/platelet-specific deletion of mTOR was established, and be used to evaluate the role of mTOR in platelet activation and thrombus formation.
mTOR platelets were deficient in thrombus formation when grown on low-concentration collagen-coated surfaces; however, no deficiency in thrombus formation was observed when mTOR platelets were perfused on higher concentration collagen-coated surfaces. In FeCl-induced mouse mesenteric arteriole thrombosis models, wild-type (WT) and mTOR mice displayed significantly different responses to low-extent injury with respect to the ratio of occluded mice, especially within the first 40 min. Additionally, mTOR platelets displayed reduced aggregation and dense granule secretion (ATP release) in response to low doses of the glycoprotein VI (GPVI) agonist collagen related peptide (CRP) and the protease-activated receptor-4 (PAR4) agonist GYPGKF-NH; these deficiencies were overcame by stimulation with higher concentration agonists, suggesting dose dependence of the response. At low doses of GPVI or PAR agonist, the activation of αβ in mTOR platelets was reduced. Moreover, stimulation of mTOR platelets with low-dose CRP attenuated the phosphorylation of S6K1, S6 and Akt Ser473, and increased the phosphorylation of PKCδ Thr505 and PKCε Ser729. Using isoform-specific inhibitors of PKCs (δ, ɛ, and α/β), we established that PKCδ/ɛ, and especially PKCδ but not PKCα/β or PKCθ, may be involved in low-dose GPVI-mediated/mTOR-dependent signaling.
These observations indicate that mTOR plays an important role in GPVI-dependent platelet activation and thrombus formation.
由于 mTOR（哺乳动物/雷帕霉素靶蛋白）基因缺失的小鼠在胚胎发育过程中死亡，因此尚未使用基因敲除技术评估 mTOR 在血小板中的作用。
建立了巨核细胞/血小板特异性 mTOR 缺失的小鼠模型，并用于评估 mTOR 在血小板激活和血栓形成中的作用。
mTOR 血小板在低浓度胶原蛋白涂层表面上形成血栓的能力缺陷；然而，当 mTOR 血小板在高浓度胶原蛋白涂层表面上灌注时，没有观察到血栓形成的缺陷。在 FeCl 诱导的小鼠肠系膜小动脉血栓形成模型中，野生型（WT）和 mTOR 小鼠对低程度损伤的反应明显不同，尤其是在前 40 分钟内。此外，mTOR 血小板对低剂量糖蛋白 VI（GPVI）激动剂胶原相关肽（CRP）和蛋白酶激活受体-4（PAR4）激动剂 GYPGKF-NH 的聚集和致密颗粒分泌（ATP 释放）减少；这些缺陷通过刺激更高浓度的激动剂得到克服，表明反应的剂量依赖性。在低剂量的 GPVI 或 PAR 激动剂下，mTOR 血小板中的αβ激活减少。此外，低剂量 CRP 刺激 mTOR 血小板可降低 S6K1、S6 和 Akt Ser473 的磷酸化，并增加 PKCδ Thr505 和 PKCε Ser729 的磷酸化。使用 PKC（δ、ɛ 和 α/β）同工型特异性抑制剂，我们确定 PKCδ/ɛ，特别是 PKCδ，而不是 PKCα/β 或 PKCθ，可能参与低剂量 GPVI 介导的/mTOR 依赖性信号传导。
这些观察结果表明，mTOR 在 GPVI 依赖性血小板激活和血栓形成中发挥重要作用。
