Mouse anti-Human SLC7A5 monoclonal antibody, clone 5E0

Scope: Understanding the regulatory mechanism of milk protein synthesis is important to develop strategies to improve milk protein and enhance lactation performance. The mammalian target of rapamycin (mTOR) pathway is a crucial modulator of protein synthesis. In this study, we want to investigate if T1R1/T1R3 can regulate milk protein synthesis and mediate the mTOR pathway in the mice mammary gland in vivo. Methods and results: T1R1 knockout mice, WT mice, and mammary explants were used. The weigh-suckle-weigh method was used to quantify the milk yield. The expression level of 13-casein and AA transporter mRNA were analyzed by qPCR. Western blot was used to analyze protein abundance of members of the mTOR pathway. As expected, the knockout of T1R1 not only reduced the total milk yield in the mice mammary glands, but also repressed 13-casein synthesis. Additionally, the phosphorylation of 4EB P1 and S6K was significantly decreased in T1R1 knockout mice. The T1R1 knockout also increased the protein abundance of the AA transporter SLC3A2 and mRNA expression of SLC7A5/SLC3A2 and SLC1A5. Activation of the mTOR pathway was repressed by inhibition of T1R3 or T1R1 knockout in mammary gland explants. Conclusion: T1R1/T1R3 modulates the mTOR pathway to regulate milk protein synthesis in the mouse mammary gland in vivo.

Large neutral amino acid transporter 1 (LAT1) is a solute carrier protein located primarily in the blood-brain barrier (BBB) that offers the potential to deliver drugs to the brain. It is also up-regulated in cancer cells, as part of a tumor's increased metabolic demands. Previously, amino acid prodrugs have been shown to be transported by LAT1. Carboxylic acid bioisosteres may afford prodrugs with an altered physicochemical and pharmacokinetic profile than those derived from natural amino acids, allowing for higher brain or tumor levels of drug and/or lower toxicity. The effect of replacing phenylalanine's carboxylic acid with a tetrazole, acylsulfonamide and hydroxamic acid (HA) bioisostere was examined. Compounds were tested for their ability to be LAT1 substrates using both cis-inhibition and trans-stimulation cell assays. As HA-Phe demonstrated weak substrate activity, its structure-activity relationship (SAR) was further explored by synthesis and testing of HA derivatives of other LAT1 amino acid substrates (i.e., Tyr, Leu, Ile, and Met). The potential for a false positive in the trans-stimulation assay caused by parent amino acid was evaluated by conducting compound stability experiments for both HA-Leu and the corresponding methyl ester derivative. We concluded that HA's are transported by LAT1. In addition, our results lend support to a recent account that amino acid esters are LAT1 substrates, and that hydrogen bonding may be as important as charge for interaction with the transporter binding site. (C) 2016 Elsevier Ltd. All rights reserved.