Porcine IGF-1R synonymous mutations in the intracellular domain affect cell proliferation and alter kinase activity

Effects of synonymous mutations on kinetic properties and structure of firefly luciferase: Molecular dynamics simulation, molecular docking, RNA folding, and experimental study

Although synonymous mutations have long been thought to lack striking results, a growing body of research shows these mutations have highly variable effects. In this study, the impact of synonymous mutations in the development of thermostable luciferase was investigated using a combination of experimental and theoretical approaches. Using bioinformatics analysis, the codon usage features in the Lampyridae family's luciferases were studied and four synonymous mutations of Arg in luciferase were created. An exciting result was that the analysis of kinetic parameters showed a slight increase in the thermal stability of the mutant luciferase. AutoDock Vina, %MinMax algorithm, and UNAFold Server were used to perform molecular docking, folding rate, and RNA folding, respectively. Here, it was assumed that in the region (Arg337) with a moderate propensity for coil, synonymous mutation altered the rate of translation, which in turn may lead to a slight change in the structure of the enzyme. According to the molecular dynamics simulation data, local minor global flexibility is observed in the context of the protein conformation. A plausible explanation is that this flexibility may strengthen hydrophobic interactions due to its sensitivity to a molecular collision. Accordingly, thermostability originated mainly from hydrophobic interaction.

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

As a key regulator of gene transcription and post-transcriptional modification, miRNAs play a wide range of roles in skeletal muscle development. Skeletal muscle satellite cells contribute to postnatal growing muscle fibers. Thus, the goal of this study was to explore the effects of novel miRNA Y-56 on porcine skeletal muscle satellite cells (PSCs). We found that Y-56 was highly expressed in porcine muscle tissues, and its expression was higher in Bama Xiang pigs than in Landrace pigs. The EdU assay, cell counting kit-8, and flow cytometry results showed that Y-56 overexpression suppressed cell proliferation and cell cycle, whereas Y-56 inhibition resulted in the opposite consequences. The results of qRT-PCR and Western blot showed that Y-56 remarkably inhibited the expression levels of cyclin-dependent kinase 4 (CDK4), proliferating cell nuclear antigen (PCNA), and cyclin D1. We identified that IGF-1R was a direct target of Y-56 by dual-luciferase reporter assay. Moreover, IGF-1R overexpression promoted the proliferation and cell cycle process of PSCs and upregulated the expression of CDK4, PCNA, and cyclin D1. Conversely, IGF-1R knockdown had the opposite effect. Furthermore, IGF-1R overexpression partially reversed the inhibition of the cell proliferation and cell cycle process of PSCs and the downregulation of the expression of CDK4, PCNA, and Cyclin D1 caused by Y-56 overexpression. Finally, Y-56 inhibited the protein expression levels of p-AKT and p-ERK. Collectively, our findings suggested that Y-56 represses the proliferation and cell cycle process of PSCs by targeting IGF-1R-mediated AKT and ERK pathways.

Synonymous Mutations of Porcine Igf1r Extracellular Domain Affect Differentiation and Mineralization in MC3T3-E1 Cells

Owing to the wide application of miniature pigs in biomedicine, the formation mechanism of its short stature must be elucidated. The insulin-like growth factor 1 receptor (IGF-1R), which receives signals through the extracellular domain (ECD) binding with ligands, is crucial in regulating cell growth and bone matrix mineralization. In this study, two haplotypes of Igf1r with four synonymous mutations in the coding sequences of IGF-1R ECD between large pigs (LP) and Bama pigs (BM) were stably expressed in the Igf1r-knockout MC3T3-E1 cells and named as MC3T3-LP cells (LP group) and MC3T3-BM cells (BM group), respectively. IGF-1R expression was lower in the BM group than in the LP group both in terms of transcription and translation levels, and IGF-1R expression inhibited cell proliferation. In addition, IGF-1R expression in the BM group promoted early-stage differentiation but delayed late-stage differentiation, which not only suppressed the expression of bone-related factors but also reduced alkaline phosphatase activity and calcium deposition. Moreover, different haplotypes of Igf1r changed the stability and conformation of the protein, further affecting the binding with IGF-1. Our data indicated that the four synonymous mutations of IGF1R ECD encoded by affect gene transcription and translation, thereby further leading to differences in the downstream pathways and functional changes of osteoblasts.