Expression and function of PEPT2 during transdifferentiation of alveolar epithelial cells |
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Authors: | Mikihisa Takano Taishi HoriuchiYoshihiro Sasaki Yuki KatoJunya Nagai Ryoko Yumoto |
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Institution: | Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan |
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Abstract: | AimsThe purpose of this study was to clarify the expression and function of peptide transporter 2 (PEPT2) in primary cultured alveolar type II epithelial cells and in transdifferentiated type I-like cells.Main methodsReal-time PCR analysis, uptake study of 3H]Gly-Sar, and immunostaining were performed in alveolar epithelial cells.Key findingsThe expression of PEPT2 mRNA in type II cells isolated from rat lungs was highest at day 0, and decreased rapidly during culture of the cells. In accordance with this change, PEPT2 activity estimated as cefadroxil-sensitive 3H]Gly-Sar uptake also decreased along with transdifferentiation. The expression of PEPT2 protein in type II cells was confirmed by immunostaining and Western blot analysis. The uptake of 3H]Gly-Sar in type II cells was time- and pH-dependent. In contrast, minimal time-dependence and no pH-dependence of 3H]Gly-Sar uptake were observed in type I-like cells. The maximal 3H]Gly-Sar uptake was observed at pH 6.0, and the uptake decreased at higher pHs in type II cells. The uptake of 3H]Gly-Sar in type II cells was inhibited by cefadroxil in a concentration-dependent manner, the IC50 value being 4.3 μM. On the other hand, no significant inhibition by cefadroxil was observed in type I-like cells. In addition, 3H]Gly-Sar uptake in type II cells was saturable, the Km value being 72.0 μM.SignificancePEPT2 is functionally expressed in alveolar type II epithelial cells, but the expression decreases along with transdifferentiation, and PEPT2 would be almost completely lost in type I cells. |
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Keywords: | Oligopeptide transporter PEPT2 Gly-Sar uptake Alveolar epithelial cells Transdifferentiation |
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