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The peptide transporter PepT2 is expressed in rat brain and mediates the accumulation of the fluorescent dipeptide derivative β‐Ala‐Lys‐N ε ‐AMCA in astrocytes
Author(s) -
Dieck Susanne Tom,
Heuer Heike,
Ehrchen Jan,
Otto Christiane,
Bauer Karl
Publication year - 1999
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/(sici)1098-1136(19990101)25:1<10::aid-glia2>3.0.co;2-y
Subject(s) - dipeptide , biology , peptide , oligopeptide , biochemistry , green fluorescent protein , transporter , microbiology and biotechnology , fluorescence , in situ hybridization , biophysics , messenger rna , gene , physics , quantum mechanics
We describe the synthesis of a fluorescent dipeptide derivative, β‐Ala‐Lys‐N ε ‐AMCA, which could be used as an excellent reporter molecule for studying the oligopeptide transport system in brain cell cultures. Fluorescence microscopic and immunocytochemical studies revealed that the reporter peptide specifically accumulated in astrocytes (type I and II) and O‐2A progenitor cells but not in neurons or differentiated oligodendrocytes. In astroglia‐rich cell culture the dipeptide derivative is taken up in unmetabolized form by an energy dependent, saturable process with apparent kinetic constants of K M = 28 μM and Vmax = 6 nmol v̄mZ h −1 v̄mZ mg protein −1 at pH 7.2. Competition studies revealed that the accumulation of β‐Ala‐Lys‐N ε ‐AMCA is strongly inhibited by dipeptides and pseudopeptides such as bestatin, arphamenine A and B. The biochemical data indicated that the properties of this high‐affinity oligopeptide carrier closely resemble those of the renal peptide transport system PepT2 and Northern blot analysis demonstrated that PepT2 mRNA is expressed in glial but not in neuronal cell cultures. In situ hybridization histochemistry also revealed a non‐neuronal localization of PepT2 transcripts and a diffuse, widespread distribution of PepT2 signals throughout the entire rat brain. The selective accumulation of the fluorescent reporter molecule by brain cells under viable conditions may provide a useful tool for studying peptide uptake systems and other aspects of astroglial physiology. GLIA 25:10–20, 1999. © 1999 Wiley‐Liss, Inc.