ELF5 modulates casein synthesis in goat mammary epithelial cells via JAK2/STAT5 signaling pathway.

OBJECTIVE: Goat milk contains a high concentration of caseins which are beneficial to human health. Understanding the regulatory mechanisms of casein synthesis in goats contribute to improving milk quality. Epithelial-specific E74-like factor 5 (ELF5) is important in milk protein synthesis, although the molecular mechanism by which ELF5 regulates casein synthesis remains unclear. This study aims to investigate the regulatory roles of ELF5 on casein production in goat mammary epithelial cells (GMECs). METHODS: Primary GMECs were isolated from goats and characterized using immunofluorescence and oil red O staining. The goat ELF5 gene overexpression vector and small interfering RNA were transfected into GMECs, respectively. Cell viability was accessed using cell counting kit-8 assay, and cell apoptosis was detected by flow cytometry. Genes involved in cell proliferation, apoptosis, and casein synthesis were examined by quantitative realtime polymerase chain reaction and Western blot. After co-treatment of Janus kinase 2 (JAK2) or signal transducer and activator of transcription 5 (STAT5) inhibitors, casein gene expression was examined by using Western blot. The interaction between ELF5 and STAT5 was verified by co-immunoprecipitation assay. RESULTS: ELF5 enhances cell viability and the expression of genes associated with proliferation, while simultaneously inhibiting apoptosis and the expression of apoptosis-related genes. Then, ELF5 upregulates the expression of αS1-, αS2-, β- and κ-casein, in addition to enhancing JAK2/STAT5 signaling pathway. The inhibition assay of JAK2 and STAT5 activity reveals that ELF5 regulates casein synthesis via JAK2/STAT5 signaling pathway. CONCLUSION: ELF5 upregulates casein synthesis through the activation of the JAK2/STAT5 signaling pathway, offering a strategy for manipulating ELF5 to increase casein content and improve the protein quality of goat milk.