Dey Nirmalya, Bera Amit, Das Falguni, Ghosh-Choudhury Nandini, Kasinath Balakuntalam S, Choudhury Goutam Ghosh
Department of Medicine, University of Texas Health Science Center at San Antonio Texas, United States.
VA Research, South Texas Veterans Health Care System, San Antonio, TX, United States; Department of Pathology, University of Texas Health Science Center at San Antonio, Texas, United States.
Cell Signal. 2015 Jul;27(7):1276-85. doi: 10.1016/j.cellsig.2015.03.007. Epub 2015 Mar 20.
High glucose milieu inhibits PTEN expression to activate Akt kinase and induces glomerular mesangial cell hypertrophy and matrix protein expression in diabetic nephropathy. Specific mechanism by which high glucose inhibits PTEN expression is not clear. We found that high glucose increased the expression of the microRNA-26a (miR-26a) in mesangial cells. Using a sensor plasmid with 3'UTR-driven luciferase, we showed PTEN as a target of miR-26a in response to high glucose. Overexpression of miR-26a reduced the PTEN protein levels resulting in increased Akt kinase activity similar to high glucose treatment. In contrast, anti-miR-26a reversed high glucose-induced suppression of PTEN with concomitant inhibition of Akt kinase activity. Akt-mediated phosphorylation of tuberin and PRAS40 regulates mTORC1, which is necessary for mesangial cell hypertrophy and matrix protein expression. Inhibition of high glucose-induced miR-26a blocked phosphorylation of tuberin and PRAS40, which lead to suppression of phosphorylation of S6 kinase and 4EBP-1, two substrates of mTORC1. Furthermore, we show that expression of miR-26a induced mesangial cell hypertrophy and increased fibronectin and collagen I (α2) expression similar to that observed with the cells incubated with high glucose. Anti-miR-26a inhibited these phenomena in response to high glucose. Together our results provide the first evidence for the involvement of miR-26a in high glucose-induced mesangial cell hypertrophy and matrix protein expression. These data indicate the potential therapeutic utility of anti-miR-26a for the complications of diabetic kidney disease.
高糖环境抑制PTEN表达以激活Akt激酶，并在糖尿病肾病中诱导肾小球系膜细胞肥大和基质蛋白表达。高糖抑制PTEN表达的具体机制尚不清楚。我们发现高糖可增加系膜细胞中微小RNA-26a（miR-26a）的表达。使用带有3'UTR驱动荧光素酶的传感器质粒，我们证明PTEN是高糖刺激下miR-26a的靶标。miR-26a的过表达降低了PTEN蛋白水平，导致Akt激酶活性增加，类似于高糖处理。相反，抗miR-26a可逆转高糖诱导的PTEN抑制，并同时抑制Akt激酶活性。Akt介导的结节性硬化蛋白和PRAS40的磷酸化调节mTORC1，这对于系膜细胞肥大和基质蛋白表达是必需的。抑制高糖诱导的miR-26a可阻断结节性硬化蛋白和PRAS40的磷酸化，进而抑制mTORC1的两个底物S6激酶和4EBP-1的磷酸化。此外，我们发现miR-26a的表达诱导系膜细胞肥大，并增加纤连蛋白和I型胶原（α2）的表达，类似于用高糖培养的细胞所观察到的情况。抗miR-26a可抑制高糖诱导的这些现象。我们的结果共同提供了首个证据，证明miR-26a参与高糖诱导的系膜细胞肥大和基质蛋白表达。这些数据表明抗miR-26a在糖尿病肾病并发症治疗中的潜在应用价值。
