Glycine and L-arginine transport in cultured Müller glial cells (TR-MUL)

Ken Ichi Hosoya, Takamichi Ichikawa, Shin Ichi Akanuma, Shirou Hirose, Masanori Tachikawa

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

We have reported previously that creatine is biosynthesized from glycine and l-arginine in Müller cells, but the mechanism responsible for glycine and l-arginine uptake by Müller cells remains elusive. To explore this issue, [14C]glycine and [3H]l-arginine uptake by Müller cells was characterized using a conditionally immortalized rat Müller cell line (TR-MUL5 cells). [14C]Glycine uptake by TR-MUL5 cells was Na+- and Cl--dependent, and a saturable process with Michaelis-Menten constants of 48.6μM and 4.53mM, and inhibited by glycine transporter 1 (GlyT1) and system A substrates. Under Cl--free conditions, the high-affinity process was abolished. RT-PCR analysis demonstrated that GlyT1 and system A (encoding ATA1 and ATA2) mRNA are expressed in TR-MUL5 cells. These uptake studies suggest that GlyT1 and system A are involved in [14C]glycine uptake for the high- and low-affinity processes, respectively, in TR-MUL5 cells. [3H]l-Arginine uptake by TR-MUL5 cells was primarily an Na+-independent and saturable process with Michaelis-Menten constants of 15.0 and 403μM. This process was inhibited by substrates of cationic amino acid transporter (CAT)s, such as l-arginine, l-lysine, and l-ornithine. The expression of CAT1 protein was detected in TR-MUL5 cells. These results suggest that CAT1 is at least involved in [3H]l-arginine uptake by TR-MUL5 cells. In conclusion, GlyT1 and CAT1 most likely mediate glycine and l-arginine uptake, respectively, by Müller cells and are expected to play an important role in supplying precursors for creatine biosynthesis in Müller cells.

Original languageEnglish
Pages (from-to)262-268
Number of pages7
JournalNeurochemistry International
Volume57
Issue number3
DOIs
Publication statusPublished - 2010 Oct

Keywords

  • CAT1
  • GlyT1
  • Glycine
  • L-Arginine
  • Müller cells
  • System A

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Cell Biology

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