Localization of PEPT1 and PEPT2 proton-coupled oligopeptide transporter mRNA and protein in rat kidney

Abstract

To determine the renal localization of oligopeptide transporters, Northern blot analyses were performed and polyclonal antisera were generated against PEPT1 and PEPT2, the two cloned rat H+/peptide transporters. Under high-stringency conditions, a 3.0-kb mRNA transcript of rat PEPT1 was expressed primarily in superficial cortex, whereas a 3.5-kb mRNA transcript of PEPT2 was expressed primarily in deep cortex/outer stripe of outer medulla. PEPT1 antisera detected a specific band on immunoblots of renal and intestinal brush-border membrane vesicles (BBMV) with an apparent mobility of ∼90 kDa. PEPT2 antisera detected a specific broad band of ∼85 kDa in renal but not in intestinal BBMV. PEPT1 immunolocalization experiments showed detection of a brush border antigen in S1 segments of the proximal tubule and in the brush border of villi from all segments of the small intestine. In contrast, PEPT2 immunolocalization was primarily confined to the brush border of S3 segments of the proximal tubule. All other nephron segments in rat were negative for PEPT1 and PEPT2 staining. Overall, our results conclusively demonstrate that although PEPT1 is expressed in early regions of the proximal tubule (pars convoluta), PEPT2 is specific for the latter regions of proximal tubule (pars recta).

Glycylsarcosine uptake in rabbit renal brush border membrane vesicles isolated from outer cortex or outer medulla: Evidence for heterogeneous distribution of oligopeptide transporters

“…mRNA expression studies in rat (11) have demonstrated that while PEPT1 is specific for early regions of the proximal tubule (pars convoluta), PEPT2 is overwhelmingly but not exclusively expressed in latter regions of the proximal tubule (pars recta). More recent studies (12) have corroborated these findings and provided definitive evidence for the heterogeneous distribution of PEPT1 and PEPT2 proteins in rat kidney. In this regard, strong PEPT1-specific immunostaining was observed in outer cortex, with progressively weaker staining in deeper cortical regions and no staining in outer medulla.…”

“…These investigators and others (9,10) have shown that while PEPT1 is expressed in the intestine and to a smaller extent in kidney, PEPT2 is expressed only in kidney. In addition, more recent studies (11,12) have demonstrated that PEPT1 and PEPT2 are differentially distributed along the proximal tubule, with PEPT1 being predominant in the convoluted segment and PEPT2 being predominant in the straight segment. However, mRNA and/or protein expression levels do not always reflect a similar degree of substrate activity.…”

An update on renal peptide transporters

“…It was then also found in the brush-border membrane of epithelial cells in the kidney proximal tubule S1 segment (60). By immunostaining and transport analysis, PEPT1 has also recently been shown to be present in the apical membrane of bile duct epithelial cells (36).…”

“…It was initially cloned from a renal cDNA library and detected in brush-border membranes of cells in S2 and S3 segments (10,60). More recently, PEPT2 has been identified in the peripheral nervous system, in the membranes and cytoplasm of satellite glial cells surrounding the ganglionic neurons (29), and in the central nervous system.…”

PepT1-Mediated Tripeptide KPV Uptake Reduces Intestinal Inflammation

“…The specificity of hPepT1 is broad and includes many di-and tripeptides in addition to various peptide-derived drugs (3)(4)(5)(6)(7)(8). PepT1 is mainly expressed in brush-border membranes of enterocytes in the small intestine, in proximal tubular cells of the S1 segment of the kidney, and in bile-duct epithelial cells (4,5,(9)(10)(11)(12)(13)(14)(15). By contrast, in the colon, expression of PepT1 mRNA and protein is low (16) and sometimes cannot be detected (10,15,17).…”