Study On The Function Of SNAT2 On Milk Protein Synthesis In Mammary Glands Of Dairy Cows

Milk is a natural food that is rich in nutrients,easy to absorb,and widely popular,and an excellent source of high-quality protein in human food.The milk protein in milk contains all essential amino acids and other amino acids required for human growth and development,and its composition ratio is reasonable.The casein content in cow’s milk accounts for 80% of the total protein content in cow’s milk,and has high nutritional value.With the increasing population,the demand for dairy products has gradually increased.Therefore,how to improve the quality of milk and increase the content of milk protein is a problem that needs to be solved urgently.During lactation,milk proteins are synthesized in large amounts in breast epithelial cells.Amino acid transporters play a key role in the synthesis of milk proteins,assisting the transport of a variety of essential amino acids into cells and participating in milk protein synthesis.The amino acid transporters of the SLC38 family mainly mediate the absorption of Na +-dependent neutral amino acids.SLC38 family member SNAT2(SLC38A2)is expressed in breast tissue during lactation,plays an important role in the process of transporting amino acids into the breast,and is considered to be one of the important amino acid transporters in cells.However,in dairy cow mammary epithelial cells,the relationship between SNAT2 and milk protein synthesis and the specific molecular mechanism through which milk protein synthesis is regulated are not clear.In this study,cow breast tissue and cow mammary epithelial cells were used as experimental materials to study the expression pattern of SNAT2 in cow breast tissue and the effect of SNAT2 on milk protein synthesis.We first used western blot and immunofluorescence techniques to detect the expression of SNAT2 in the mammary gland tissues of cows.The results showed that the expression of SNAT2 in the breast tissue of lact ating cows was significantly higher than that in the dry period,and β-casein was also highly expressed during lactation.Immunofluorescence detection results showed that SNAT2 is highly expressed in mammary epithelial cells surrounding the acinus in the b reast tissue of lactating cows.Subsequently,the expression of β-casein in cow mammary epithelial cells after SNAT2 gene overexpression and interference was studied.The results showed that after SNAT2 gene overexpression,the amount of β-casein synthesis in cow mammary epithelial cells increased;The amount of β-casein synthesis in cow mammary epithelial cells is reduced.The MTT method was used to detect the changes in the viability of dairy cow mammary epithelial cells after SNAT2 gene overexpression an d interference.The results showed that after SNAT2 overexpression,cell viability increased;after SNAT2 gene interference,cell viability decreased.These results indicate that SNAT2 plays an important role in the regulation of milk protein synthesis in the mammary epithelial cells of dairy cows.In order to clarify the regulation of SNAT2 expression in dairy cow mammary epithelial cells,we studied the regulation of SNAT2 expression by prolactin.Western blot and immunofluorescence results showed that the expression of SNAT2 in mammary epithelial cells of dairy cows treated with prolactin was significantly increased.At the same time,the content of β-casein in the prolactin treatment group also increased significantly.Based on the above results,it is pr eliminarily proved in the cell model that prolactin,as an important hormone for lactation regulation,can regulate the expression of SNAT2 and further regulate the synthesis of milk protein.In order to further study the signal pathway of prolactin regula ting the expression of SNAT2 in mammary epithelial cells of cows.In this study,the Western blot method was used to detect the phosphorylation level of AKT and m TOR signaling pathway molecules in dairy cow mammary epithelial cells treated with prolactin.The results showed that prolactin can induce the phosphorylation of AKT,m TOR and its downstream signaling molecules P70S6 K and 4E-BP1.When PI3 K inhibitors were used to inhibit PI3 K activity,the phosphorylation levels of AKT,m TOR,P70S6 K and 4E-BP1 decreased,and the expression levels of SNAT2 and β-casein also decreased accordingly.Using rapamycin to inhibit the m TOR signaling pathway,it was found that the phosphorylation levels of m TOR and its downstream signaling molecules P70S6 K and 4E-BP1 decreased,and the expression levels of SNAT2 and β-casein also decreased accordingly.These results indicate that prolactin regulates the expression of SNAT2 through the PI3 K / AKT / m TOR signaling pathway in cow mammary epithelial cells,which in turn affects milk protein synthesis.In summary,SNAT2 is highly expressed in mammary epithelial cells of dairy cows during lactation.SNAT2 can regulate milk protein synthesis in cow mammary epithelial cells,and prolactin can regulate the expression of SNAT2 through th e PI3 K / AKT / m TOR signaling pathway,which in turn affects the synthesis of milk protein.The results of this study can enrich the molecular mechanism of the regulation of milk protein synthesis in the mammary glands of lactating cows,and provide a refe rence for the future regulation of molecular protein synthesis and the improvement of milk quality in molecular production.