DNAJA1 positively regulates amino acid‐stimulated milk protein and fat synthesis in bovine mammary epithelial cells.

Several cellular processes, including the recovery of misfolded proteins, the folding of polypeptide chains, transit of polypeptides across the membrane, construction and disassembly of protein complexes, and modulation of protein control, are carried out by DnaJ homolog subfamily A member 1 (DNAJA1), which belongs to the DnaJ heat‐shock protein family. It is unknown if DNAJA1 regulates the production of milk in bovine mammary epithelium cells (BMECs). Methionine and leucine increased DNAJA1 expression and nuclear location, as seen by us. In contrast to DNAJA1 knockdown, overexpression of DNAJA1 boosted the production of milk proteins and fats as well as mammalian target of rapamycin (mTOR) and sterol regulatory element binding protein‐1c (SREBP‐1c). As a result of amino acids, mTOR and SREBP‐1c gene expression are stimulated, and DNAJA1 is a positive regulator of BMECs' amino acid‐induced controlled milk protein and fat production. Significance statement: The aim of this study was to investigate whether DnaJ homolog subfamily A member 1 (DNAJA1) from the DnaJ heat‐shock protein family has an effect on milk fat and milk protein synthesis in bovine mammary epithelial cells stimulated by amino acids. We found that DNAJA1 plays a positive regulatory role in milk protein and fat synthesis of bovine mammary epithelium cells and in the expression and activation of mammalian target of rapamycin and sterol regulatory element binding protein‐1c induced by amino acids. Although the exact biochemical mechanism by which amino acids promote DNAJA1 expression is unknown, stimulation of this amino acid may lead to protein alterations in DNAJA1, such as phosphorylation. Future studies must examine these underlying processes. [ABSTRACT FROM AUTHOR]