Journal
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
Volume 301, Issue 3, Pages 820-829Publisher
AMER SOC PHARMACOLOGY EXPERIMENTAL THERAPEUTICS
DOI: 10.1124/jpet.301.3.820
Keywords
-
Categories
Funding
- NHLBI NIH HHS [P01 HL018575] Funding Source: Medline
- NIGMS NIH HHS [R01 GM035498, T32 GM007767] Funding Source: Medline
- NINDS NIH HHS [R01 NS034709] Funding Source: Medline
Ask authors/readers for more resources
Recent studies have established the functional and molecular presence of a high-affinity peptide transporter, PEPT2, in whole tissue rat choroid plexus. However, the precise membrane location and directionality of PEPT2-mediated transport is uncertain at present. In this study, we examined the transport kinetics of a model dipeptide, glycylsarcosine (GlySar), along with the protein expression of PEPT2 using primary cell cultures of choroidal epithelium from neonatal rats. GlySar accumulation and transepithelial transport were 3 to 4 times higher when introduced from the apical as opposed to the basal side of the monolayers. GlySar apical uptake was also stimulated by an inwardly directed proton gradient. The uptake of GlySar was inhibited by di/tripeptides, carnosine, and alpha-amino cephalosporins but was unaffected by amino acids, cephalosporins lacking an alpha-amino group, and organic anions and cations. The Michaelis constant (K-m) of GlySar was 59.6 muM for apical uptake and 1.4 mM for basal uptake; this is consistent with the high-affinity properties of PEPT2 at the apical membrane. Immunoblot analyses and immunofluorescent confocal microscopy demonstrated the presence of PEPT2, but not PEPT1, in rat choroid plexus epithelial cells. Moreover, PEPT2 was present in the apical and subapical regions of the cell but was absent in the basolateral membrane. These findings demonstrate, for the first time, that PEPT2 protein is present at the apical membrane of choroidal epithelial cells and that it is functionally active at this membrane surface. The results suggest that PEPT2 may have a role in the efflux of peptides and/or mimetics from cerebrospinal fluid to the blood.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available