Duan Yanru, Liu Demin, Yu Huahui, Zhang Shihan, Xia Yihua, Du Zhiyong, Qin Yanwen, Wang Yajing, Ma Xinliang, Liu Huirong, Du Yunhui
Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069, People's Republic of China.
Department of Cardiology, The Second Hospital of Hebei Medical University, Shijiazhuang, 050000, Hebei, China.
Cell Biosci. 2024 Oct 1;14(1):126. doi: 10.1186/s13578-024-01306-5.
Occludin, a crucial component of tight junctions, has emerged as a promising biomarker for the diagnosis of acute ischemic disease, highlighting its significant potential in clinical applications. In the diabetes, Occludin serves as a downstream target gene intricately regulated by the adiponectin (APN) signaling pathway. However, the specific mechanism by which adiponectin regulates Occludin expression remains unclear.
Endothelial-specific Ocln knockdown reduced APN-mediated blood flow recovery after femoral artery ligation and nullified APN's protection against high-fat diet (HFD)-triggered apoptosis and angiogenesis inhibition in vivo. Mechanically, we have meticulously elucidated APN's regulatory role in Occludin expression through a comprehensive analysis spanning transcriptional and post-translational dimensions. Foxo1 has been elucidated as a crucial transcriptional regulator of Occludin that is modulated by the APN/APPL1 signaling axis, as evidenced by validation through ChIP-qPCR assays and Western blot analysis. APN hindered Occludin degradation via the ubiquitin-proteasome pathway. Mass spectrometry analysis has recently uncovered a novel phosphorylation site, Tyr467, on Occludin. This site responds to APN, playing a crucial role in inhibiting Occludin ubiquitination by APN. The anti-apoptotic and pro-angiogenic effects of APN were attenuated in vitro and in vivo following Foxo1 knockdown or expression of a non-phosphorylatable mutant, OccludinY467A. Clinically, elevated plasma concentrations of Occludin were observed in patients with diabetes. A significant negative correlation was found between Occludin levels and APN concentrations.
Our study proposes that APN modulates Occludin expression through mechanisms involving both transcriptional and post-translational interactions, thereby conferring a protective effect on endothelial integrity within diabetic vasculature.
闭合蛋白是紧密连接的关键组成部分，已成为急性缺血性疾病诊断中有前景的生物标志物，凸显了其在临床应用中的巨大潜力。在糖尿病中，闭合蛋白作为脂联素（APN）信号通路复杂调控的下游靶基因。然而，脂联素调节闭合蛋白表达的具体机制仍不清楚。
内皮特异性Ocln基因敲低减少了股动脉结扎后APN介导的血流恢复，并消除了APN对高脂饮食（HFD）引发的体内细胞凋亡和血管生成抑制的保护作用。从机制上讲，我们通过涵盖转录和翻译后层面的综合分析，精心阐明了APN在闭合蛋白表达中的调节作用。通过染色质免疫沉淀定量聚合酶链反应（ChIP-qPCR）分析和蛋白质免疫印迹分析验证，已阐明叉头框蛋白O1（Foxo1）是由APN/衔接蛋白含有PH结构域和亮氨酸拉链基序1（APPL1）信号轴调节的闭合蛋白关键转录调节因子。APN通过泛素-蛋白酶体途径阻碍闭合蛋白降解。质谱分析最近在闭合蛋白上发现了一个新的磷酸化位点，酪氨酸467（Tyr467）。该位点对APN有反应，在抑制APN介导的闭合蛋白泛素化中起关键作用。在体外和体内，敲低Foxo1或表达不可磷酸化的突变体闭合蛋白Y467A后，APN的抗凋亡和促血管生成作用减弱。临床上，糖尿病患者血浆中闭合蛋白浓度升高。闭合蛋白水平与APN浓度之间存在显著负相关。
我们的研究表明，APN通过涉及转录和翻译后相互作用的机制调节闭合蛋白表达，从而对糖尿病血管系统中的内皮完整性产生保护作用。
