A Novel miRNA Y-56 Mediates the Proliferation of Porcine Skeletal Muscle Satellite Cells by Targeting the IGF-1R-mediated AKT and ERK Pathways

Background: The skeletal muscle phenotype of the Bama Xiang pig (BM) is significantly different from the Landrace pig (LP). Uncovering the mechanism of porcine skeletal muscle growth will be of great significance to elucidate the mechanism of the different formation. As the key post-transcriptional regulators, miRNAs play an indispensable role in skeletal muscle development. The proliferation of skeletal muscle satellite cells not only maintain the muscle stem cell population, but also provide a large number of muscle derived cells. Thus, the goal of this study is to explore the effects of a novel miRNA Y-56 on the porcine skeletal muscle satellite cells (PSCs). Results: Firstly, we found that Y-56 was highly expressed in porcine muscle tissues, and its expression was higher in the BM than the LP. The EdU staining and CCK-8 assays results showed that increased levels of Y-56 suppressed cell proliferation, whereas decreased levels of Y-56 resulted in the opposite consequences. Furthermore, flow cytometry results showed that overexpression of Y-56 significantly reduced the percentage of S-phase cells, and the qRT-PCR and western blotting results showed that the expression levels of cyclin dependent kinase 2 (CDK4), proliferating cell nuclear antigen (PCNA) and Cyclin D1 were significantly inhibited. Moreover, downregulation of Y-56 increased the number of S-phase cells and the expression of CDK, PCNA and Cyclin D1. Furtherly, we identified that insulin like growth factor-1 receptor (IGF-1R) was a direct target of Y-56. Consistently, overexpression of IGF-1R promoted the cell proliferation of the PSCs, and increased the number of S-phase cells, as well as up-regulated the expressions of CDK4, PCNA and Cyclin D1. Meanwhile, knock-down of IGF-1R was associated with the opposite tend. What’s more, overexpression of IGF-1R partially reversed the inhibition of cell proliferation of the PSCs, the decrease of the percentage of S-phase cells and down-regulation of the expression levels of CDK4, PCNA and Cyclin D1, which caused by overexpression of Y-56. Finally, there was a significant decrease in the expression level of p-AKT and p-ERK with transfecting Y-56 mimics in the PSCs, and overexpression of IGF-1R reversed the decrease. Conclusion: Collectively, our findings suggested that Y-56 represses proliferation and cell cycle process of the PSCs through targeting IGF-1R that activated the AKT and ERK pathways.