Glutamate receptor subunit δ2 is highly expressed in a novel population of glial-like cells in rat pineal glands in culture

Shouki Yatsushiro, Mitsuko Hayashi, Mitsuhiro Morita, Akitsugu Yamamoto, Yoshinori Moriyama

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The mammalian pineal gland uses L-glutamate as an intercellular chemical transmitter to regulate negatively melatonin synthesis. To receive glutamate signals, pinealocytes express at least three kinds of glutamate receptors: metabotropic receptor types 3 and 5 and an ionotropic receptor, GluR1. In this study, we examined whether or not the fourth class of ionotropic receptor, δ, which is known for its nondefinitive molecular function and its unique expression pattern in brain, is expressed in pineal gland. RT-PCR analyses with specific probes indicated the expression of mRNA of δ2 but not that of δ1 in pineal gland and cultured pineal cells. Western blotting analysis with polyclonal antibodies specific to the carboxyl-terminal region of the δ2 receptor recognized a single 110-kDa polypeptide of cerebellar membranes and specifically immunostained Purkinje cells. The δ2 antibodies recognized a 110-kDa polypeptide of pineal membranes and specifically immunostained huge glial-like cells with the occasional presence of several long, branching processes in a pineal cell culture. δ2 is not uniformly distributed throughout the cells and is relatively abundant at the periphery of the cell bodies and long processes, where the terminals of synaptophysin-positive processes of pinealocytes, a site for glutamate secretion, are frequently present. The δ2-positive cells constitute a very minor population among total pineal cells (~0.03%). Double immunolabeling with δ2 antibodies and antibodies against marker proteins for pineal interstitial cells clearly distinguishes δ2-positive pineal cells and other known interstitial cells, including glial fibrillary acidic protein-or vimentin-positive glial-like cells. These results indicated that the δ2 glutamate receptor is expressed in a novel subpopulation of pineal glial-like cells in culture and suggest the presence of a glutamate-mediated intercellular signal transduction mechanism between pinealocytes and δ2-expressing cells. The pineal cells may provide a good experimental system for studies on the function of glutamate receptor δ2.

Original languageEnglish
Pages (from-to)1115-1122
Number of pages8
JournalJournal of Neurochemistry
Volume75
Issue number3
DOIs
Publication statusPublished - Sep 11 2000

Keywords

  • Endocrine cell
  • Glial cell
  • Glutamate
  • Glutamate receptor δ2
  • Pineal gland
  • Pinealocyte
  • Signal transduction

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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