Publications

• Molecular mechanism of dipeptide and drug transport by the human renal H+/oligopeptide cotransporter hPEPT2.

  Sala-Rabanal M., Loo D.D., Hirayama B.A., Wright E.M.

  The human proton/oligopeptide cotransporters hPEPT1 and hPEPT2 have been targeted to enhance the bioavailability of drugs and prodrugs. Previously, we established the mechanisms of drug transport by hPEPT1. Here, we extend these studies to hPEPT2. Major variants hPEPT2*1 and hPEPT2*2 were expresse ... >> More

  The human proton/oligopeptide cotransporters hPEPT1 and hPEPT2 have been targeted to enhance the bioavailability of drugs and prodrugs. Previously, we established the mechanisms of drug transport by hPEPT1. Here, we extend these studies to hPEPT2. Major variants hPEPT2*1 and hPEPT2*2 were expressed in Xenopus oocytes, and each was examined using radiotracer uptake and electrophysiological methods. Glycylsarcosine (Gly-Sar); the beta-lactam antibiotics ampicillin, amoxicillin, cephalexin, and cefadroxil; and the anti-neoplastics delta-aminolevulinic acid (delta-ALA) and bestatin induced inward currents, indicating that they are transported. Variations in transport rate were due to differences in affinity and in turnover rate: for example, cefadroxil was transported with higher apparent affinity but at a lower maximum velocity than Gly-Sar. Transport rates were highest at pH 5 and decreased significantly as the external pH was increased. Our results strongly suggest that the protein does not operate as a cotransporter in tissues where there is little or no pH gradient, such as choroid plexus, lung, or mammary gland. In the absence of substrates, rapid voltage jumps produced hPEPT2 capacitive currents at pH 7. These transients were significantly reduced at pH 5 but recovered on addition of substrates. The seven-state ordered kinetic model previously proposed for hPEPT1 accounts for the steady-state kinetics of neutral drug and dipeptide transport by hPEPT2. The model also explains the capacitive transients, the striking difference in pre-steady-state behavior between hPEPT2 and hPEPT1, and differences in turnover numbers for Gly-Sar and cefadroxil. No functional differences were found between the common variants hPEPT2*1 and hPEPT2*2. << Less

  Am. J. Physiol. 294:F1422-F1432(2008) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Human intestinal H+/peptide cotransporter. Cloning, functional expression, and chromosomal localization.

  Liang R., Fei Y.-J., Prasad P.D., Ramamoorthy S., Han H., Yang-Feng T.L., Hediger M.A., Ganapathy V., Leibach F.H.

  In mammalian small intestine, a H(+)-coupled peptide transporter is responsible for the absorption of small peptides arising from digestion of dietary proteins. Recently a cDNA clone encoding a H+/peptide cotransporter has been isolated from a rabbit intestinal cDNA library (Fei, Y.J., Kanai, Y., ... >> More

  In mammalian small intestine, a H(+)-coupled peptide transporter is responsible for the absorption of small peptides arising from digestion of dietary proteins. Recently a cDNA clone encoding a H+/peptide cotransporter has been isolated from a rabbit intestinal cDNA library (Fei, Y.J., Kanai, Y., Nussberger, S., Ganapathy, V., Leibach, F.H., Romero, M.F., Singh, S.K., Boron, W. F., and Hediger, M. A. (1994) Nature 368, 563-566). Screening of a human intestinal cDNA library with a probe derived from the rabbit H+/peptide cotransporter cDNA resulted in the identification of a cDNA which when expressed in HeLa cells or in Xenopus laevis oocytes induced H(+)-dependent peptide transport activity. The predicted protein consists of 708 amino acids with 12 membrane-spanning domains and two putative sites for protein kinase C-dependent phosphorylation. The cDNA-induced transport process accepts dipeptides, tripeptides, and amino beta-lactam antibiotics but not free amino acids as substrates. The human H+/peptide cotransporter exhibits a high degree of homology (81% identity and 92% similarity) to the rabbit H+/peptide cotransporter. But surprisingly these transporters show only a weak homology to the H(+)-coupled peptide transport proteins present in bacteria and yeast. Chromosomal assignment studies with somatic cell hybrid analysis and in situ hybridization have located the gene encoding the cloned human H+/peptide cotransporter to chromosome 13 q33-->q34. << Less

  J. Biol. Chem. 270:6456-6463(1995) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.