Monday, 23 May 2005 - 9:15 AM

This presentation is part of: Transporters

Perspectives into the Molecular and Functional Characteristics of Intestinal Oligopeptide Transporters

Gregory T. Knipp, Rutgers, the State University of New Jersey, Piscataway, NJ

Peptide-based drugs are increasingly being utilized for the therapeutic intervention of many disorders including AIDS, hypertension, and cancer. The gastrointestinal absorption of small peptide-based agents may be significantly influenced by their affinity for proton-coupled, oligopeptide transporters (POT). Considerable focus has been traditionally placed on Peptide Transporter 1 (PepT1) since it was the first identified human POT and is expressed in the intestine. Recent evidence suggests that Peptide/Histidine Transporter 1 (PHT1) may also play a role in the intestinal absorption of peptides. Results from preliminary investigations into the mRNA and protein expression of PepT1 and PHT1 in the human intestine will be discussed. In addition, the development and characterization of stably transfected MDCK/hPepT1-V5/His clonal cell lines with varying expression levels (low, medium and high) of epitope-tagged hPepT1 have been utilized to quantify the relationship between hPepT1 expression and its functional kinetics. Uptake and transport kinetics of glycylsarcosine, carnosine, benzylpenicillin, aminolevulenic acid and valacyclovir were determined to delineate hPEPT1-mediated kinetics for each substrate. These studies demonstrated that the MDCK/hPepT1-V5/His clonal cells may be a more useful model for screening hPEPT1 affinity of peptide-based. Finally, human PHT1 transiently transfected into COS-7 cells demonstrate a sodium independent, proton dependent affinity for histidine and carnosine, but no affinity for glycylsarcosine. These results provide new insights into the molecular and functional significance of POT members in the human gastrointestinal tract and provide a framework for future studies focused on elucidating the interplay between their physiological expression and substrate-structure relationships necessary for the absorption of peptide-based agents.

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