Downregulation of OPA3 Is Responsible for Transforming Growth Factor-beta-Induced Mitochondrial Elongation and F-Actin Rearrangement in Retinal Pigment Epithelial ARPE-19 Cells

Abstract

Transforming growth factor-beta signaling is known to be a key signaling pathway in the induction of epithelial-mesenchymal transition. However, the mechanism of TGF-beta signaling in the modulation of EMT remains unclear. In this study, we found that TGF-beta treatment resulted in elongation of mitochondria accompanied by induction of N-cadherin, vimentin, and F-actin in retinal pigment epithelial cells. Moreover, OPA3, which plays a crucial role in mitochondrial dynamics, was downregulated following TGF-beta treatment. Suppression of TGF-beta signaling using Smad2 siRNA prevented loss of OPA3 induced by TGF-beta. Knockdown of OPA3 by siRNA and inducible shRNA significantly increased stress fiber levels, cell length, cell migration and mitochondrial elongation. In contrast, forced expression of OPA3 in ARPE-19 cells inhibited F-actin rearrangement and induced mitochondrial fragmentation. We also showed that Drp1 depletion increased cell length and induced rearrangement of F-actin. Depletion of Mfn1 blocked the increase in cell length during TGF-beta-mediated EMT. These results collectively substantiate the involvement of mitochondrial dynamics in TGF-beta-induced EMT.