Abstract
L-Lysine (L-Lys) is an essential amino acid that plays fundamental roles in protein synthesis. Many nuclear phosphorylated proteins such as Stat5 and mTOR regulate milk protein synthesis. However, the details of milk protein synthesis control at the transcript and translational levels are not well known. In this current study, a two-dimensional gel electrophoresis (2-DE)/MS-based proteomic technology was used to identify phosphoproteins responsible for milk protein synthesis in dairy cow mammary epithelial cells (DCMECs). The effect of L-Lys on DCMECs was analyzed by CASY technology and reversed phase high performance liquid chromatography (RP-HPLC). The results showed that cell proliferation ability and β-casein expression were enhanced in DCMECs treated with L-Lys. By phosphoproteomics analysis, six proteins, including MAPK1, were identified up-expressed in DCMECs treated with 1.2 mM L-Lys for 24 h, and were verified by quantitative real-time PCR (qRT-PCR) and western blot. Overexpression and siRNA inhibition of MAPK1 experiments showed that MAPK1 upregulated milk protein synthesis through Stat5 and mTOR pathway. These findings that MAPK1 involves in regulation of milk synthesis shed new insights for understanding the mechanisms of milk protein synthesis.
Highlights
In eukaryotes, protein phosphorylation is among the most important regulatory events in cells, guiding primary biological processes, such as cell division, growth, migration, differentiation, and protein synthesis
Overexpression and siRNA inhibition of mitogen-activated protein kinase 1 (MAPK1) experiments showed that MAPK1 upregulated milk protein synthesis through Stat5 and mammalian target of rapamycin (mTOR) pathway
We still do not know the details of the cell signal transduction pathway for milk protein synthesis, including what molecules participate in the Jak2-Stat5 pathway to regulate milk protein synthesis at the transcriptional level, and what molecules affect the mTOR pathway to regulate milk protein synthesis at the translational level, and what molecules transfer the signals of amino acids to Jak2-Stat5 pathway and mTOR pathway
Summary
Protein phosphorylation is among the most important regulatory events in cells, guiding primary biological processes, such as cell division, growth, migration, differentiation, and protein synthesis. Amino acids (AA) are known as anabolic factors, which induce protein gain by stimulating protein synthesis while inhibiting proteolysis. We still do not know the details of the cell signal transduction pathway for milk protein synthesis, including what molecules participate in the Jak2-Stat pathway to regulate milk protein synthesis at the transcriptional level, and what molecules affect the mTOR pathway to regulate milk protein synthesis at the translational level, and what molecules transfer the signals of amino acids to Jak2-Stat pathway and mTOR pathway. We used two-dimensional gel electrophoresis (2-DE) to profile the nuclear phosphoproteomics of DCMECs treated with L-Lys in order to identify differentially expressed phosphoproteins. This will facilitate a better understanding of the lactation molecular mechanism
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
