International Mammalian Genome Society

17th International Mouse Genome Conference

9-12 November 2003, Braunschweig, Germany


POSTER 188 - TARGETED DISRUPTION OF THE PEPTIDE TRANSPORTER PEPT2 IN MICE LEADS TO ALTERED RENAL HANDLING OF PEPTIDES

Frey I
Molecular Nutrition Unit, Technical University of Munich

Co-Authors: 1) Rubio-Aliaga I, 2) Eichinger H M, 1) Daniel H
Institutions: Molecular Nutrition Unit, Technical University of Munich

Transporters for di- and tripeptides that belong to the proton-coupled oligopeptide transporter family (POT) are found in prokaryotes and eukaryotes. In mammals two different systems have been identified. PEPT1 is mainly expressed in the small intestine where it mediates the absorption of dietary peptides. PEPT2 on the other hand shows widespread expression. The highest PEPT2 expression is found in the kidney, where it mediates the reabsorption of filtered di- and tripeptides. To study the physiological role of PEPT2 we have generated a knockout mouseline that lacks a functional PEPT2 protein. The accumulation of labelled model dipeptides in kidneys was markedly reduced in null mice. A compensatory upregulation of PEPT1 or of the dipeptide/histidine transporter PHT1 could not be observed. Pept2-/- mice showed a lower kidney weight. To determine whether there is an increased renal loss of dipeptides in urine, amino acids were analysed by HPLC previous to and after in vitro digestion with a renal dipeptidase (EC 3.4.19.13). Normal urine samples showed a slightly increased free amino acid excretion in the Pept2-/- mice and a significantly higher excretion of a not yet identified metabolite. Dipeptidase digestion of urine samples lead to a significant rise of the concentration of glycine and cystine in the transporter deficient animals. This effect became even more pronounced when mice were fed a high protein diet. Our studies confirm the importance of PEPT2 in renal reabsorption of di- and tripeptides and suggest that mainly the reuptake of cystinylglycine may be impaired.


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