Abstract
Rat pinealocytes accumulate glutamate in microvesicles and secrete it through exocytosis so as to transmit signals intercellularly. Glutamate is involved in the negative regulation of norepinephrine-stimulated melatonin production. In this study, we found that aspartate is also released from cultured rat pinealocytes during the exocytosis of glutamate. The release of aspartate was triggered by addition of KCI or A23187 (a Ca 2+ ionophore) in the presence of Ca 2+ and was proportional to the amount of L-glutamate released. Furthermore, the release of aspartate was inhibited by both botulinum neurotoxin type E and L- or N-type voltage-gated Ca 2+ channel blockers. Bay K 8644, an agonist for the L-type Ca 2+ channel, stimulated the release of aspartate 2.1-fold. Immunohistochemical analyses with antibodies against aspartate and synaptophysin revealed that aspartate is colocalized with synaptophysin in a cultured pinealocyte. HPLC with fluorometric detection indicated that the released aspartate is of the L- form, although pinealocytes also contain the D form in their cytoplasm, corresponding to ~30% of the total free aspartate. Radiolabeled L-aspartate was taken up by the microsomal fraction from bovine pineal glands in a Na +- dependent manner. The Na +-dependent uptake of L-aspartate was strongly inhibited by L-cysteine sulfinate, β-hydroxyaspartate, and L-serine-O- sulfate, inhibitors for the Na +-dependent glutamate/aspartate transporter on the plasma membrane. Na +-dependent sequestration of L-aspartate was also observed in cultured rat pinealocytes, which was inhibited similarly by these transporter inhibitors. These results strongly suggest that L-aspartate is released through microvesicle-mediated exocytosis from pinealocytes and is taken up again through the Na +-dependent transporter at the plasma membrane. The possible role of L-aspartate as an intercellular chemical transmitter in the pineal gland is discussed.
| Original language | English |
|---|---|
| Pages (from-to) | 340-347 |
| Number of pages | 8 |
| Journal | Journal of Neurochemistry |
| Volume | 69 |
| Issue number | 1 |
| Publication status | Published - Jul 1997 |
| Externally published | Yes |
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Keywords
- Aspartate transporter
- D-Aspartate
- Exocytosis
- Glutamate transporter
- L-Aspartate
- Microvesicles (synaptic-like microvesicles)
- Pineal gland
ASJC Scopus subject areas
- Biochemistry
- Cellular and Molecular Neuroscience
Cite this
L-aspartate but not the D form is secreted through microvesicle-mediated exocytosis and is sequestered through Na +-dependent transporter in rat pinealocytes. / Yatsushiro, Shouki; Yamada, Hiroshi; Kozaki, Shunji; Kumon, Hiromi; Michibata, Hitoshi; Yamamoto, Akitsugu; Moriyama, Yoshinori.
In: Journal of Neurochemistry, Vol. 69, No. 1, 07.1997, p. 340-347.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - L-aspartate but not the D form is secreted through microvesicle-mediated exocytosis and is sequestered through Na +-dependent transporter in rat pinealocytes
AU - Yatsushiro, Shouki
AU - Yamada, Hiroshi
AU - Kozaki, Shunji
AU - Kumon, Hiromi
AU - Michibata, Hitoshi
AU - Yamamoto, Akitsugu
AU - Moriyama, Yoshinori
PY - 1997/7
Y1 - 1997/7
N2 - Rat pinealocytes accumulate glutamate in microvesicles and secrete it through exocytosis so as to transmit signals intercellularly. Glutamate is involved in the negative regulation of norepinephrine-stimulated melatonin production. In this study, we found that aspartate is also released from cultured rat pinealocytes during the exocytosis of glutamate. The release of aspartate was triggered by addition of KCI or A23187 (a Ca 2+ ionophore) in the presence of Ca 2+ and was proportional to the amount of L-glutamate released. Furthermore, the release of aspartate was inhibited by both botulinum neurotoxin type E and L- or N-type voltage-gated Ca 2+ channel blockers. Bay K 8644, an agonist for the L-type Ca 2+ channel, stimulated the release of aspartate 2.1-fold. Immunohistochemical analyses with antibodies against aspartate and synaptophysin revealed that aspartate is colocalized with synaptophysin in a cultured pinealocyte. HPLC with fluorometric detection indicated that the released aspartate is of the L- form, although pinealocytes also contain the D form in their cytoplasm, corresponding to ~30% of the total free aspartate. Radiolabeled L-aspartate was taken up by the microsomal fraction from bovine pineal glands in a Na +- dependent manner. The Na +-dependent uptake of L-aspartate was strongly inhibited by L-cysteine sulfinate, β-hydroxyaspartate, and L-serine-O- sulfate, inhibitors for the Na +-dependent glutamate/aspartate transporter on the plasma membrane. Na +-dependent sequestration of L-aspartate was also observed in cultured rat pinealocytes, which was inhibited similarly by these transporter inhibitors. These results strongly suggest that L-aspartate is released through microvesicle-mediated exocytosis from pinealocytes and is taken up again through the Na +-dependent transporter at the plasma membrane. The possible role of L-aspartate as an intercellular chemical transmitter in the pineal gland is discussed.
AB - Rat pinealocytes accumulate glutamate in microvesicles and secrete it through exocytosis so as to transmit signals intercellularly. Glutamate is involved in the negative regulation of norepinephrine-stimulated melatonin production. In this study, we found that aspartate is also released from cultured rat pinealocytes during the exocytosis of glutamate. The release of aspartate was triggered by addition of KCI or A23187 (a Ca 2+ ionophore) in the presence of Ca 2+ and was proportional to the amount of L-glutamate released. Furthermore, the release of aspartate was inhibited by both botulinum neurotoxin type E and L- or N-type voltage-gated Ca 2+ channel blockers. Bay K 8644, an agonist for the L-type Ca 2+ channel, stimulated the release of aspartate 2.1-fold. Immunohistochemical analyses with antibodies against aspartate and synaptophysin revealed that aspartate is colocalized with synaptophysin in a cultured pinealocyte. HPLC with fluorometric detection indicated that the released aspartate is of the L- form, although pinealocytes also contain the D form in their cytoplasm, corresponding to ~30% of the total free aspartate. Radiolabeled L-aspartate was taken up by the microsomal fraction from bovine pineal glands in a Na +- dependent manner. The Na +-dependent uptake of L-aspartate was strongly inhibited by L-cysteine sulfinate, β-hydroxyaspartate, and L-serine-O- sulfate, inhibitors for the Na +-dependent glutamate/aspartate transporter on the plasma membrane. Na +-dependent sequestration of L-aspartate was also observed in cultured rat pinealocytes, which was inhibited similarly by these transporter inhibitors. These results strongly suggest that L-aspartate is released through microvesicle-mediated exocytosis from pinealocytes and is taken up again through the Na +-dependent transporter at the plasma membrane. The possible role of L-aspartate as an intercellular chemical transmitter in the pineal gland is discussed.
KW - Aspartate transporter
KW - D-Aspartate
KW - Exocytosis
KW - Glutamate transporter
KW - L-Aspartate
KW - Microvesicles (synaptic-like microvesicles)
KW - Pineal gland
UR - http://www.scopus.com/inward/record.url?scp=0030919370&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0030919370&partnerID=8YFLogxK
M3 - Article
C2 - 9202328
AN - SCOPUS:0030919370
VL - 69
SP - 340
EP - 347
JO - Journal of Neurochemistry
JF - Journal of Neurochemistry
SN - 0022-3042
IS - 1
ER -