A novel L-glutamate transporter inhibitor reveals endogenous D-aspartate homeostasis in rat pheochromocytoma MPT1 cells.

Hayato Koyama, Masae Sekine, Takemitsu Furuchi, Masumi Katane, Noriyuki Nimura, Keiko Shimamoto, Terumi Nakajima, Hiroshi Homma

School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.

Life sciences 2005 May 6

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We previously reported for the first time that D-aspartate (D-Asp) is biosynthesized by cultured mammalian cells such as pheochromocytoma (PC)12 cells and its subclone MPT1 (FEBS Lett. 434 (1998) 231, Arch. Biochem. Biophys. 404 (2002) 92). We speculated that D-Asp levels in the intra- and extracellular spaces of the cultured cells are maintained in a dynamic state of homeostasis. To test this here, we utilized a novel and potent L-Glu transporter inhibitor, TFB-TBOA. This inhibitor proved to be a genuine nontransportable blocker of the transporter even during long periods of culture. Use of this inhibitor with MPT1 cells confirmed that D-Asp levels are in a dynamic steady state where it is constantly released into the extracellular space by a yet undefined mechanism as well as being constantly and intensively taken up by the cells via the L-Glu transporter. We estimated the rate with which D-Asp is constitutively released from MPT1 cells is approx. 3.8 pmol/h/1x10(5) cells.

Citation

Hayato Koyama, Masae Sekine, Takemitsu Furuchi, Masumi Katane, Noriyuki Nimura, Keiko Shimamoto, Terumi Nakajima, Hiroshi Homma. A novel L-glutamate transporter inhibitor reveals endogenous D-aspartate homeostasis in rat pheochromocytoma MPT1 cells. Life sciences. 2005 May 6;76(25):2933-44