Abstract
The role of LeuRS, an aminoacyl-tRNA synthetase, as an intracellular l-leucine sensor for the mTORC1 pathway has been the subject of much research recently. Despite this, the association between LeuRS and lactation in dairy cow mammary epithelial cells (DCMECs) remains unknown. In this study, we found that LeuRS expression in mammary gland tissue was significantly higher during lactation than pregnancy. Moreover, our data demonstrates that LeuRS is localized in the cytoplasm. Treatment with leucine increased DCMECs viability and proliferation, as well as mammalian target of rapamycin (mTOR), p-mTOR, ribosomal protein S6 kinase 1 (S6K1), p-S6K1, β-Casein, sterol regulatory element binding protein 1c (SREBP-1c), glucose transporter 1 (GLUT1), and Cyclin D1 mRNA and protein expression. Secretion of lactose and triglyceride were also increased. siRNA-mediated knockdown of LeuRS led to reduction in all of these processes. Based on these data, LeuRS up-regulates the mTOR pathway to promote proliferation and lactation of DCMECs in response to changes in the intracellular leucine concentration.
Highlights
Lactation regulation has been the subject of much scientific and clinical interest for several decades.the effect of hormones and amino acids on lactation in the dairy cow has been studied since the last century [1,2,3]
Quantitative real-time PCR (Figure 1C) and western blotting analysis (Figure 1D) revealed that the level of LeuRS expression was significantly higher in lactating mammary gland tissue than in pregnancy mammary gland tissue
Our results showed that proteins related to proliferation and lactation were increased in dairy cow mammary epithelial cells (DCMECs) treated with 1.2 mmol/L leucine for 24 and 48 h
Summary
Lactation regulation has been the subject of much scientific and clinical interest for several decades. Leucine and other essential amino acids have been linked to processes performed by the mammary gland of dairy cows [4]. Combined with these insights, researchers began to focus on the molecular regulation mechanisms of amino acids on lactation in the last decade [5,6,7]. MTOR is a serine/threonine kinase that integrates signals from amino acids, growth factors, and the energy status of the cell. LeuRS plays a critical role in milk synthesis by sensing the intracellular leucine concentration and regulating amino acid-induced mTORC1 activation
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