Met stimulates ARID1A degradation and activation of the PI3K-SREBP1 signaling to promote milk fat synthesis in bovine mammary epithelial cells

Methionine (Met) can promote milk fat synthesis in bovine mammary epithelial cells (BMECs), but the potential molecular mechanism is largely unknown. In this report, we aim to explore the role and molecular mechanism of AT-rich interaction domain 1A (ARID1A) in milk fat synthesis stimulated by Met. ARID1A knockdown and activation indicated that ARID1A negatively regulated the synthesis of triglycerides, cholesterol and free fatty acids and the formation of lipid droplets in BMECs. ARID1A also negatively regulated the phosphorylation of PI3K and AKT proteins, as well as the expression and maturation of SREBP1. Met stimulated the phosphorylation of PI3K and AKT proteins, as well as the expression and maturation of SREBP1, while ARID1A gene activation blocked the stimulatory effects of Met. We further found that ARID1A was located in the nucleus of BMECs, and Met reduced the nuclear localization and expression of ARID1A. ARID1A gene activation blocked the stimulation of <i>PI3K</i> and <i>SREBP1</i> mRNA expression by Met. In summary, our data suggests that ARID1A negatively regulates milk fat synthesis stimulated by Met in BMECs through inhibiting the PI3K-SREBP1 signaling pathway, which may provide some new perspectives for improving milk fat synthesis.