MicroRNA-126 regulates the induction and function of CD4(+) Foxp3(+) regulatory T cells through PI3K/AKT pathway.
Bottom Line: In this study, we reported that miR-126 was expressed in mouse and human Tregs.Furthermore, miR-126 silencing could obviously reduce the expression of Foxp3 on Tregs, which was accompanied by decreased expression of CTLA-4 and GITR, as well as IL-10 and TGF-β, and impair its suppressive function.Finally, we further revealed that miR-126 silencing could impair the suppressive function of Tregs in vivo and endow effectively antitumour effect of CD8(+) T cells in adoptive cell transfer assay using a murine breast cancer model.
Affiliation: Department of Immunology, Zunyi Medical College, Guizhou, 563000, China.Show MeSH
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Mentions: Recent evidence showed that PI3K/Akt pathway was critical for the expression of Foxp3 in Tregs [10, 11]. And other research works reported miR-126 could target to p85β and regulate the transduction of PI3K/Akt pathway [17, 18]. Then, the direct effect of miR-126 mimics on the expression of p85β in Tregs was detected and similar result was found that miR-126 mimics could obviously inhibit p85 expression in Tregs (data not shown). Next, we further investigated whether miR-126 silencing could enhance the expression of p85β and successively regulate the transduction of TCR-mediated PI3K/Akt pathway which ultimately influenced the expression of Foxp3 in Tregs. As shown in Figure 5A, the expression of p85β in miR-126 ASO-transfected group increased about 2.5 times (P < 0.05). Moreover, the level of phosphorylation of Akt and phosphorylation of mTOR increased significantly in miR-126 ASO-transfected group compared with those in control group (Fig. 5A), indicating that miR-126 could regulate the activation of PI3K/Akt pathway in Tregs. Consistently, we also found that miR-126 ASO significantly enhance the expression of p85β, as well as phosphorylated Akt and phosphorylated mTOR, in the induction of Tregs (Supporting Information Figure S2, P < 0.05). To further confirm whether this enhanced activation of PI3K-Akt pathway was responsible for reduced expression of Foxp3 in Tregs, we further cotransfected p85β RNAi into Tregs and found that p85β RNAi could abrogate the effect of miR-126 ASO on the expression of Foxp3 in Tregs (Fig. 5B, P < 0.05). Furthermore, p85β RNAi also could reverse the effect of miR-126 ASO on Tregs induction (Fig. 5C, P < 0.05). To investigate the efficiency and specificity of p85β RNAi on Tregs in miR-126 ASO-transfected group, we further detected the expression of total p85, p85α and p85β on Tregs in miR-126 ASO-transfected group. Our data showed that p85β RNAi could significantly reduce the expression of p85β in miR-126 ASO-transfected Tregs (Supporting Information Figure S3A and B, P < 0.05). However, p85β RNAi did not alter the expression of p85α in miR-126 ASO-transfected Tregs (Supporting Information Figure S3B, P > 0.05). Finally, to confirm this finding, Akt inhibitor IV also was used and similar results were obtained (Fig. 5D and E, P < 0.05). These data strongly suggested that silencing of miR-126 reduced the expression of Foxp3 through up-regulating PI3K/Akt pathway, which ultimately altered the induction and suppressive function of Tregs.
Affiliation: Department of Immunology, Zunyi Medical College, Guizhou, 563000, China.