Details

Autor(en) / Beteiligte

• Maity, Soumya
• Bera, Amit
• Ghosh-Choudhury, Nandini
• Das, Falguni
• Kasinath, Balakuntalam S.
• Choudhury, Goutam Ghosh

Titel

microRNA-181a downregulates deptor for TGFβ-induced glomerular mesangial cell hypertrophy and matrix protein expression

Ist Teil von

• Experimental cell research, 2018-03, Vol.364 (1), p.5-15

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2018

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• TGFβ contributes to mesangial cell hypertrophy and matrix protein increase in various kidney diseases including diabetic nephropathy. Deptor is an mTOR-interacting protein and suppresses mTORC1 and mTORC2 activities. We have recently shown that TGFβ-induced inhibition of deptor increases the mTOR activity. The mechanism by which TGFβ regulates deptor expression is not known. Here we identify deptor as a target of the microRNA-181a. We show that in mesangial cells, TGFβ increases the expression of miR-181a to downregulate deptor. Decrease in deptor augments mTORC2 activity, resulting in phosphorylation/activation of Akt kinase. Akt promotes inactivating phosphorylation of PRAS40 and tuberin, leading to stimulation of mTORC1. miR-181a-mimic increased mTORC1 and C2 activities, while anti-miR-181a inhibited them. mTORC1 controls protein synthesis via phosphorylation of translation initiation and elongation suppressors 4EBP-1 and eEF2 kinase. TGFβ-stimulated miR-181a increased the phosphorylation of 4EBP-1 and eEF2 kinase, resulting in their inactivation. miR-181a-dependent inactivation of eEF2 kinase caused dephosphorylation of eEF2. Consequently, miR-181a-mimic increased protein synthesis and hypertrophy of mesangial cells similar to TGFβ. Anti-miR-181a blocked these events in a deptor-dependent manner. Finally, TGFβ-miR-181a-driven deptor downregulation increased the expression of fibronectin. Our results identify a novel mechanism involving miR-181a-driven deptor downregulation, which contributes to mesangial cell pathologies in renal complications. •TGFβ increases microRNA-181a to target deptor mRNA 3′UTR.•TGFβ-stimulated miR-181a activates Akt kinase to induce inactivating phosphorylation of mTORC1 inhibitors tuberin and PRAS40.•Increased miR-181a by TGFβ enhances mTORC1 activity via deptor downregulation.•TGFβ-induced miR-181a regulates phosphorylation of mRNA translation initiation and elongation factors.•miR-181a-targeted deptor regulates TGFβ-induced mesangial cell hypertrophy and matrix protein fibronectin expression.