Abstract
Mammalian pinealocytes are neuroendocrine cells that synthesize and secrete melatonin, these processes being positively controlled by norepinephrine derived from innervating sympathetic neurons. Previously, we showed that pinealocytes contain a large number of microvesicles (MVs) that specifically accumulate L-glutamate through a vesicular glutamate transporter and contain proteins for exocytosis such as synaptobrevin 2 (VAMP2). These findings suggested that the MVs are counterparts of synaptic vesicles and are involved in paracrine-like chemical transduction in the pineal gland. Here, we show that pinealocytes actually secrete glutamate upon stimulation by KCl in the presence of Ca2+ at 37°C. The ability of glutamate secretion disappeared when the cells were incubated at below 20°C. Loss of the activity was also observed on successive stimulation, but it was recovered after 12 hr incubation. A low concentration of cadmium chloride or ω-conotoxin GVIA inhibited the secretion. Botulinum neurotoxin E cleaved synaptic vesicle-associated protein 25 (SNAP-25) and thus inhibited the secretion. The released L-glutamate stimulated pinealocytes themselves via glutamate receptor(s) and inhibited norepinephrine-stimulated melatonin secretion. These results strongly suggest that pinealocytes are glutaminergic paraneurons, and that the glutaminergic system regulates negatively the synthesis and secretion of melatonin. The MV-mediated paracrine-like chemical transduction seems to be a novel mechanism that regulates hormonal secretion by neuroendocrine cells.
| Original language | English |
|---|---|
| Pages (from-to) | 175-191 |
| Number of pages | 17 |
| Journal | Journal of Pineal Research |
| Volume | 21 |
| Issue number | 3 |
| Publication status | Published - Oct 1996 |
| Externally published | Yes |
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Keywords
- Chemical transaction
- Glutamate receptors
- L-glutamate
- Melatonin
- Microvestcles
- Paracrine
- Paraneuron
- Pineal gland
ASJC Scopus subject areas
- Endocrinology
Cite this
Microvesicle-mediated exocytosis of glutamate is a novel paracrine-like chemical transduction mechanism and inhibits melatonin secretion in rat pinealocytes. / Yamada, Hiroshi; Yamamoto, Akitsugu; Yodozawa, Susumu; Kozaki, Shunji; Takahashi, Masami; Morita, Mitsuhiro; Michibata, Hitoshi; Furuichi, Teiichi; Mikoshiba, Katsuhiko; Moriyama, Yoshinori.
In: Journal of Pineal Research, Vol. 21, No. 3, 10.1996, p. 175-191.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Microvesicle-mediated exocytosis of glutamate is a novel paracrine-like chemical transduction mechanism and inhibits melatonin secretion in rat pinealocytes
AU - Yamada, Hiroshi
AU - Yamamoto, Akitsugu
AU - Yodozawa, Susumu
AU - Kozaki, Shunji
AU - Takahashi, Masami
AU - Morita, Mitsuhiro
AU - Michibata, Hitoshi
AU - Furuichi, Teiichi
AU - Mikoshiba, Katsuhiko
AU - Moriyama, Yoshinori
PY - 1996/10
Y1 - 1996/10
N2 - Mammalian pinealocytes are neuroendocrine cells that synthesize and secrete melatonin, these processes being positively controlled by norepinephrine derived from innervating sympathetic neurons. Previously, we showed that pinealocytes contain a large number of microvesicles (MVs) that specifically accumulate L-glutamate through a vesicular glutamate transporter and contain proteins for exocytosis such as synaptobrevin 2 (VAMP2). These findings suggested that the MVs are counterparts of synaptic vesicles and are involved in paracrine-like chemical transduction in the pineal gland. Here, we show that pinealocytes actually secrete glutamate upon stimulation by KCl in the presence of Ca2+ at 37°C. The ability of glutamate secretion disappeared when the cells were incubated at below 20°C. Loss of the activity was also observed on successive stimulation, but it was recovered after 12 hr incubation. A low concentration of cadmium chloride or ω-conotoxin GVIA inhibited the secretion. Botulinum neurotoxin E cleaved synaptic vesicle-associated protein 25 (SNAP-25) and thus inhibited the secretion. The released L-glutamate stimulated pinealocytes themselves via glutamate receptor(s) and inhibited norepinephrine-stimulated melatonin secretion. These results strongly suggest that pinealocytes are glutaminergic paraneurons, and that the glutaminergic system regulates negatively the synthesis and secretion of melatonin. The MV-mediated paracrine-like chemical transduction seems to be a novel mechanism that regulates hormonal secretion by neuroendocrine cells.
AB - Mammalian pinealocytes are neuroendocrine cells that synthesize and secrete melatonin, these processes being positively controlled by norepinephrine derived from innervating sympathetic neurons. Previously, we showed that pinealocytes contain a large number of microvesicles (MVs) that specifically accumulate L-glutamate through a vesicular glutamate transporter and contain proteins for exocytosis such as synaptobrevin 2 (VAMP2). These findings suggested that the MVs are counterparts of synaptic vesicles and are involved in paracrine-like chemical transduction in the pineal gland. Here, we show that pinealocytes actually secrete glutamate upon stimulation by KCl in the presence of Ca2+ at 37°C. The ability of glutamate secretion disappeared when the cells were incubated at below 20°C. Loss of the activity was also observed on successive stimulation, but it was recovered after 12 hr incubation. A low concentration of cadmium chloride or ω-conotoxin GVIA inhibited the secretion. Botulinum neurotoxin E cleaved synaptic vesicle-associated protein 25 (SNAP-25) and thus inhibited the secretion. The released L-glutamate stimulated pinealocytes themselves via glutamate receptor(s) and inhibited norepinephrine-stimulated melatonin secretion. These results strongly suggest that pinealocytes are glutaminergic paraneurons, and that the glutaminergic system regulates negatively the synthesis and secretion of melatonin. The MV-mediated paracrine-like chemical transduction seems to be a novel mechanism that regulates hormonal secretion by neuroendocrine cells.
KW - Chemical transaction
KW - Glutamate receptors
KW - L-glutamate
KW - Melatonin
KW - Microvestcles
KW - Paracrine
KW - Paraneuron
KW - Pineal gland
UR - http://www.scopus.com/inward/record.url?scp=0030254346&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0030254346&partnerID=8YFLogxK
M3 - Article
C2 - 8981262
AN - SCOPUS:0030254346
VL - 21
SP - 175
EP - 191
JO - Journal of Pineal Research
JF - Journal of Pineal Research
SN - 0742-3098
IS - 3
ER -