title: Proteomic and functional analyses reveal MAPK1 regulates milk protein synthesis.
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.
authors.affiliation: Key Laboratory of Dairy Science of Education Ministry, Northeast Agricultural University, Harbin 150030, Heilongjiang, China.
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Lu
authors.forename: Qing-Zhang
authors.initials: QZ
authors.lastname: Li
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Huang
authors.forename: Xue-Jun
authors.initials: XJ
authors.lastname: Gao
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002364:Caseins / Q000096:biosynthesis*; D002417:Cattle; D002470:Cell Survival; D002851:Chromatography, High Pressure Liquid; D015180:Electrophoresis, Gel, Two-Dimensional; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D007774:Lactation; D008239:Lysine / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism; D008892:Milk / Q000737:chemistry; D008894:Milk Proteins / Q000096:biosynthesis*; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D040901:Proteomics / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation
chemical_list: D002364:Caseins; D008894:Milk Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D050799:STAT5 Transcription Factor; D058570:TOR Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D008239:Lysine