l-Glutamate in the extracellular space regulates endogenous d-aspartate homeostasis in rat pheochromocytoma MPT1 cells

d-Aspartate—An important bioactive substance in mammals: A review from an analytical and biological point of view

“…However, in contrast to PC12 cells, MPT1 cells express the l-Glu transporter, and the released dAsp is actively taken up into the cells [139,141]. Thus, there is a dynamic exchange of d-Asp between the intra-and extracellular spaces during the culture of MPT1 cells.…”

“…MPT1 and 2068 cells are spontaneously-occurring flat cell variants of PC12 cells [137,138]. In contrast to PC12 cells, MPT1 and 2068 cells express the l-Glu transporter and are able to efficiently take up d-Asp from the culture medium [137][138][139]. In the culture of PC12 cells that are able to synthesize their own d-Asp, the d-Asp contents in the cells and culture media increase with the duration of culture (Fig.…”

“…In fact, the addition of substrates other than d-Asp or inhibitors of the l-Glu transporter competitively inhibits the uptake of d-Asp by MPT1 cells, resulting in the accumulation of d-Asp in the culture medium (Fig. 2C) [26,139,141]. Therefore, it appears that in cells that exhibit dynamic d-Asp homeostasis, as observed in MPT1 cells, l-Glu transporter substrates or inhibitors regulate the concentration of d-Asp in the extracellular space.…”

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

“…Under such conditions, L-Glu and L-Glu transporter substrates in the medium are assumed to competitively inhibit the uptake of D-Asp, resulting in its accumulation in the extracellular space. To substantiate the hypothesis that D-Asp levels are in homeostasis, we have utilized a L-Glu transporter inhibitor, DL-TBOA, which was reported to inhibit the transporter while not being transported itself (Adachi et al, 2004;Lebrun et al, 1997;Shimamoto et al, 1998). As expected, the inhibitor induced D-Asp, which is constantly released from MPT1 cells, to accumulate in the medium (Fig.…”

“…We demonstrated previously that L-Glu and L-Glu transporter substrates in the extracellular space regulate the homeostasis of endogenous D-Asp in MPT1 cells, a subclonal strain of PC12 cells (Adachi et al, 2004). We speculated that D-Asp levels may be in a dynamic state of homeostasis where it is constantly released into the extracellular space by an as yet undefined mechanism and at the same time is continuously and intensively taken up by the cells via the LGlu transporter (Fig.…”