Functional linkage of H +/peptide transporter PEPT2 and Na +/H + exchanger in primary cultures of astrocytes from mouse cerebral cortex

• Published in: Brain research 2005-05, Vol.1044 (1), p.33-41
• Main Authors: Wada, Miyuki, Miyakawa, Sakiko, Shimada, Ayumi, Okada, Naoki, Yamamoto, Akira, Fujita, Takuya
• Format: Article
• Language: English
• Subjects: Animals; Astrocytes; Astrocytes - drug effects; Astrocytes - physiology; Biological and medical sciences; Blotting, Northern - methods; Blotting, Western - methods; Cells, Cultured; Cerebral Cortex - cytology; Dipeptides - pharmacokinetics; Dose-Response Relationship, Drug; Embryo, Mammalian; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Glial Fibrillary Acidic Protein - genetics; Glial Fibrillary Acidic Protein - metabolism; Hydrogen-Ion Concentration; Immunohistochemistry - methods; Isolated neuron and nerve. Neuroglia; Kyotorphin; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Na +/H + exchanger; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurons - drug effects; Neurons - metabolism; PEPT2; Peptide transporter; Reverse Transcriptase Polymerase Chain Reaction - methods; RNA, Messenger - biosynthesis; Sodium-Hydrogen Exchangers - classification; Sodium-Hydrogen Exchangers - genetics; Sodium-Hydrogen Exchangers - metabolism; Substrate Specificity - drug effects; Symporters - antagonists & inhibitors; Symporters - genetics; Symporters - metabolism; Synaptosomal-Associated Protein 25; Tritium - pharmacokinetics; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2005.02.064

In our previous studies, we demonstrated that the high-affinity type peptide transporter PEPT2 is expressed in rat cerebral cortex using synaptosomal membrane study and that the uptake of dipeptide [ 14C]glycylsarcosine into synaptosomes was stimulated by an inwardly directed H + gradient (Fujita et al., Brain Res. 972, 52–61, 2004). However, there is no information available for the driving force of PEPT2 function in the nervous system. In the present study, we investigated functional characteristics of PEPT2 mediated transport of Gly-Sar in primary cultured astrocytes from mouse cerebral cortex and examined the effects of Na +/H + exchanger (NHE) inhibitor on Gly-Sar uptake in mouse astrocytes. In mouse astrocytes, extracellular H + influenced only the maximal velocity ( V max) of Gly-Sar uptake without affecting the apparent affinity ( K t). Interestingly, removal of Na + from uptake buffer significantly reduced Gly-Sar uptake and Gly-Sar uptake was modulated by NHE inhibitors. The treatment of EIPA, an NHE inhibitor, altered the V max value of Gly-Sar uptake but had no effect on its K t value. RT-PCR revealed that NHE1 and NHE2 mRNA are expressed in mouse cerebrocortical astrocytes. These results demonstrated that NHE activity is required to allow optimal uptake of dipeptides mediated by PEPT2 into the astrocytes. This study represents the first description of the functional co-operation of PEPT2 and NHE1 and/or NHE2 in cerebrocortical astrocytes.