CD82 attenuates TGF-beta 1-mediated epithelial-mesenchymal transition by blocking smad-dependent signaling in ARPE-19 cells

In retinal pigment epithelial (RPE) cells, transforming growth factor-beta (TGF-beta) plays a critical role in epithelial-mesenchymal transition (EMT), which contributes to various fibrotic retinal disorders. In the present study, we investigated the effect of recombinant human cluster of differentiation 82 (rhCD82), a tumor metastasis suppressor, on TGF-beta-induced EMT in the human RPE cell line APRE-19. The results show that TGF-beta 1 significantly enhanced cell migration, invasion and the expression of EMT-mediate factors in ARPE-19 cells. However, rhCD82 markedly inhibited cell mobility and the expression of epithelial marker, zonula occludens-1, as well as increased the expression of mesenchymal markers, such as vimentin and alpha-smooth muscle actin in TGF-beta 1-treated APRE-19 cells. In addition, TGF-beta 1 upregulated the phosphorylation of Smad, extracellular signal regulated kinase (ERK) and glycogen synthase kinase-3 beta (GSK-3 beta), but only phosphorylation of Smad was suppressed by rhCD82. Noteworthy, rhCD82 greatly suppressed the expression of TGF-beta receptor I (TGFRI), TGFRII and integrins in TGF-beta 1-treated APRE-19 cells. In particular, the result of molecular docking analysis and structural modeling show that rhCD82 partially interacts with the TGF-beta 1 binding sites of TGFRI, TGFRII, integrin beta 1 and integrin alpha v. Taken together, this finding suggested that rhCD82 suppressed TGF-beta 1-induced EMT of RPE by blocking of Smad-dependent pathway, which is caused by rhCD82 interaction with TGFRs and integrins, suggesting new insight into CD82 as a potential therapeutic strategy in fibrotic retinal disorders.