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Human dipeptide transporter, hPEPT1, stably transfected into Chinese hamster ovary cells
K M Covitz1, G L Amidon, W Sadée
1Department of Biopharmaceutical Sciences, University of California, San Francisco 94143-0446, USA.
Purpose:
A cDNA encoding the H(+)-coupled peptide transporter, hPEPT1, has previously been cloned from human ileum (8). The objective of this study was to establish a stably transfected cell line expressing hPEPT1 in mammalian cell culture.
Methods:
The hPEPT1 cDNA was subcloned into an expression vector carrying the CMV promoter and a neomycin resistance gene. This vector, pCDNA3-PEPT1, was transiently transfected into several cell lines to identify those capable of expressing PEPT1 transport function. CHO cells were selected and stably transfected with PEPT1 (CHO-PEPT1). Dipeptide transport activity was measured with 3H-Gly-Sar, in the presence and absence of inhibitors.
Results:
The clonal cell line, CHO-PEPT1, displayed high transport activity. Dipeptide transport was sensitive to pH and specific for dipeptides and other small peptides. Peptidomimetic antibiotics, such as cephalexin, were competitors for peptide transport.
Conclusions:
The stably transfected cell line, CHO-PEPT1 exhibits enhanced transport over that of cell lines with native expression of PEPT1, and therefore, represents a useful tool for rapid screening of drugs that utilize the peptide transporter in the human intestine for absorption.