A novel L-glutamate transporter inhibitor reveals endogenous D-aspartate homeostasis in rat pheochromocytoma MPT1 cells.
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.
Koyama
Hayato
H
School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan.
Sekine
Masae
M
Furuchi
Takemitsu
T
Katane
Masumi
M
Nimura
Noriyuki
N
Shimamoto
Keiko
K
Nakajima
Terumi
T
Homma
Hiroshi
H
D027322:Amino Acid Transport System X-AG / Q000037:antagonists & inhibitors*; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D026603:D-Aspartic Acid / Q000378:metabolism* / Q000502:physiology; D005453:Fluorescence; D006706:Homeostasis / Q000187:drug effects* / Q000502:physiology; D016716:PC12 Cells; D051381:Rats
D027322:Amino Acid Transport System X-AG; C120673:benzyloxyaspartate; D001224:Aspartic Acid; D026603:D-Aspartic Acid