肾小管上皮细胞中Rictor/mTORC2信号通路调控急性肾损伤后炎症反应的作用及机制研究

Renal tubular epithelial cells are sensitive to acute kidney injury (AKI) and they play a pro-inflammatory role in AKI, which secrete inflammatory cytokines and promote inflammatory cells accumulation. Rictor/mTORC2 contribute to the regulation of diverse cellular processes . Our previous study demonstrated that Tubular-Rictor-/- mice were characterized with increased tubular cell apoptosis and severe kidney injury compared with the Tubular-Rictor+/+ mice group. However, The role and mechanisms of Rictor/mTORC2 signaling in regulating inflammation after AKI are uncertain. Our further study in vitro showed that Rictor/mTORC2 signaling in tubular epithelial cells was activated in response to inflammatory stimuli and mediated the inflammatory cytokines secretion through the NF-κB pathway. To this end, we propose the hypothesis: Rictor/mTORC2 signaling was activated in renal tubular cells after AKI, mTORC2 could regulate IκB ubiquitination and NF-κB pathway activation in a glycogen synthase kinase-3β（GSK3β）dependent way, which mediated inflammatory response and kidney injury. This study will clarify the role and mechanisms of Rictor/mTORC2 signaling in regulating inflammation after AKI and will provide us new ideas and theoretical basis to improve the prognosis of AKI.

急性肾损伤(AKI)发生后，肾小管上皮细胞产生炎症因子促进炎症反应，与AKI的严重程度与预后密切相关。Rictor/mTORC2信号通路参与多种细胞学行为。我们先前已经发表的研究结果证明Rictor/mTORC2信号通路在介导肾小管上皮细胞存活以及AKI的过程中发挥重要作用。然而，肾小管上皮细胞中Rictor/mTORC2信号对AKI后炎症反应的调控作用和机制尚且未知。我们前期实验证明，肾小管上皮细胞中Rictor/mTORC2信号通路在炎症模型中活化，通过NF-κB信号通路反向介导炎症因子表达，并可能受到GSK3β激酶的调控。据此我们提出假设：AKI发生后，肾小管上皮细胞中Rictor/mTORC2信号通路激活，其靶蛋白GSK3β通过介导iκB的泛素化影响NF-κB通路，进一步调控炎症反应与肾脏损伤，为确立Rictor/mTORC2通路作为AKI治疗的新靶点提供更充分的依据。

哺乳动物雷帕霉素靶蛋白（mTOR）是一种高度保守的非典型丝／苏氨酸蛋白激酶，包括 mTORC1 和 mTORC2 两种复合体，在调控细胞增殖、生长、分化、蛋白质合成等细胞学行为中发挥重要作用。我们前期研究表明Rictor/mTORC2 信号在肾小管上皮细胞凋亡和 AKI 中扮演重要角色，但是 mTORC2 在 AKI中的炎症反应尚且未有研究。而据报道 mTORC2 可以调控 Yap/Taz 的转录水平，并参与NF-κB 信号通路。因此，我们设想肾小管细胞中 mTORC2 可能通过 Yap/Taz 调控肾脏炎症反应以及 AKI。我们利用 LPS 诱导小鼠的 AKI 与炎症反应，通过 Cre-loxp 系统构建了肾小管细胞中 Rictor 基因特异性敲除小鼠，利用 LPS 诱导后，我们发现Tubular-Rictor-/-小鼠出现更明显的急性肾损伤与肾脏炎症反应。体外利用 NRK-52E 细胞系，利用 siRNA 以及特异性抑制剂阻断 Rictor/Akt 信号通路，可以进一步诱导 LPS 导致的NF κ B 信号活化；其机制是通过调控 Yap/Taz的降解。本项目利用模式动物，以及多种分子生物学、细胞生物学手段阐明了肾小管上皮细胞中mTORC2信号在调控AKI后炎症反应和肾脏损伤的作用和机制, 提出了新的治疗AKI的潜在靶点。