TGFβ/Smad3信号通路在肾小管上皮细胞溶酶体耗竭中的作用

The most important pathophysiological basis of acute kidney injury and chronic kidney disease is the reduction of damage resistance and repair ability in renal tubular epithelial cells (TECs). On the one hand, our previous studies have shown that lysosome depletion is a common manifestation of injured TECs induced by various risk factors, and that exacerbates TECs damage and diminishes its ability to resist damage via impairing protective autophagy. However, the underlying mechanism of lysosome depletion is still unclear. On the other hand, hyperactive TGFβ/Smad3 signaling pathway plays a crucial role in TECs injury caused by a lot of kidney insult factors, which has been proven by many experts and my Ph.D supervisor Prof. LAN Hui-yao’s group. We hypothesize that TGFβ/Smad3 signaling acts as a key part in kidney insult caused lysosome depletion of TECs. To test this hypothesis, we will explore whether TGFβ/Smad3 signaling is involved in the lysosome depletion of TECs firstly. Then the specific mechanism of TGFβ/Smad3 signaling involved in the lysosome depletion will be determined, which may directly induce lysosome damage, or indirectly disrupt TFEB-driven CLEAR-mediated lysosome biogenesis. Due to these experiments mentioned above, we attempt to determine the mechanism of lysosome depletion in TECs, and to develop a novel approach to attenuate tubular injury and elevate tubular ability to resist damage by restoring protective autophagy.

肾小管上皮细胞（TECs）抗损伤和修复能力的下降是联系急性肾损伤和慢性肾脏病的重要病理生理基础。一方面，本课题组前期研究发现：溶酶体耗竭是多种原因所致TECs损伤的共同表现，并已发现溶酶体耗竭通过损害保护性自噬而参与TECs损伤或（和）削弱其抗损伤能力，但导致TECs溶酶体耗竭的机制目前未明。另一方面，申请人读博期间参与的香港中大蓝辉耀教授课题组已证实TGFβ/Smad3信号过度活化参与了多种原因所致TECs损伤，但TGFβ/Smad3是否作为关键信号通路介导TECs溶酶体耗竭尚未明确。本项目拟首先明确TGFβ/Smad3信号通路是否参与肾损伤因素所致TECs溶酶体耗竭，并在此基础上进一步探讨TGFβ/Smad3信号通路过度活化究竟是直接损伤细胞溶酶体，还是通过干扰转录因子EB控制的CLEAR网络而影响溶酶体新生？为下一步探索如何重塑保护性自噬来减轻TECs损伤或提高其抗损伤能力奠定基础。

自噬失调在糖尿病肾病中的关键作用已经被重视，但是其具体的调节机制尚未完全阐明。 .在本研究中，我们揭示，TGF-β/Smad通路下游关键因子Smad3通过抑制TFEB依赖的溶酶体新生、诱导溶酶体耗竭，促进糖尿病肾病状态下肾小管上皮细胞自噬失调。我们发现在糖尿病肾病体外细胞模型和小鼠动物模型中，利用特异性药物或基因干预Smad3的活性或表达，可以通过解除对 TFEB转录的抑制作用，促进溶酶体新生；进而改善溶酶体耗竭，疏通肾小管上皮细胞受阻的自噬通路。机制方面，我们发现Smad3直接结合于TFEB基因3′UTR区域并抑制其转录。然而，一旦干预肾小管上皮细胞TFEB的表达，则废除Smad3抑制对糖尿病状态下促进溶酶体新生、改善溶酶体耗竭的保护作用。.综上，Smad3通过抑制TFEB依赖的溶酶体新生进而促进溶酶体耗竭，这一作用可能是糖尿病肾病中肾小管上皮细胞自噬失调的重要机制。