Abstract
Mechanism and substrate specificity of the proton-coupled amino acid transporter 2 (PAT2, SLC36A2) have been studied so far only in heterologous expression systems such as HeLa cells and Xenopus laevis oocytes. In this study, we describe the identification of the first cell line that expresses PAT2. We cultured 3T3-L1 cells for up to 2 weeks and differentiated the cells into adipocytes in supplemented media containing 2 μM rosiglitazone. During the 14 day differentiation period the uptake of the prototype PAT2 substrate l-[3H]proline increased ~5-fold. The macro- and microscopically apparent differentiation of 3T3-L1 cells coincided with their H+ gradient-stimulated uptake of l-[3H]proline. Uptake was rapid, independent of a Na+ gradient but stimulated by an inwardly directed H+ gradient with maximal uptake occurring at pH 6.0. l-Proline uptake was found to be mediated by a transport system with a Michaelis constant (Kt) of 130 ± 10 μM and a maximal transport velocity of 4.9 ± 0.2 nmol × 5 min−1 mg of protein−1. Glycine, l-alanine, and l-tryptophan strongly inhibited l-proline uptake indicating that these amino acids also interact with the transport system. It is concluded that 3T3-L1 adipocytes express the H+-amino acid cotransport system PAT2.
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Acknowledgments
This work was supported by the Deutsche Forschungsgemeinschaft grant # BR 2430/4-3. The authors thank Valerie Voigt for assistance in PCR measurements. This work will be part of the doctoral thesis of Katja Zebisch.
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The authors declared no conflict of interest.
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The experiments comply with the current laws of the country in which they were performed.
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Zebisch, K., Brandsch, M. Transport of l-proline by the proton-coupled amino acid transporter PAT2 in differentiated 3T3-L1 cells. Amino Acids 44, 373–381 (2013). https://doi.org/10.1007/s00726-012-1340-9
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DOI: https://doi.org/10.1007/s00726-012-1340-9