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Extracellular calcium‐sensing receptor in rat oligodendrocytes: Expression and potential role in regulation of cellular proliferation and an outward K + channel
Author(s) -
Chattopadhyay Naibedya,
Ye ChianPing,
Yamaguchi Toru,
Kifor Olga,
Vassilev Peter M.,
Nishimura Robert,
Brown Edward M.
Publication year - 1998
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/(sici)1098-1136(199812)24:4<449::aid-glia10>3.0.co;2-9
Subject(s) - galactocerebroside , biology , immunocytochemistry , extracellular , microbiology and biotechnology , oligodendrocyte , astrocyte , receptor , medicine , endocrinology , myelin , biochemistry , central nervous system
Abstract A G protein‐coupled, extracellular calcium (Ca 0 2+ )‐sensing receptor (CaR) cloned from parathyroid, kidney, and brain plays crucial roles in systemic calcium metabolism. In brain, the CaR is located in nerve terminals as well as in fiber tracts, where it may be expressed in glia. Moreover, there is Ca 2+ ‐ and K + ‐dependent communication between axons and oligodendroglia. To investigate further the potential role of the CaR in oligodendroglia, we studied expression of CaR mRNA and protein as well as the effects of CaR agonists on cellular proliferation and Ca 2+ ‐activated K + channel activity in immature rat oligodendrocytes in primary culture. Reverse transcriptase polymerase chain reaction and sequencing of CaR transcripts from oligodendrocytes revealed >99% sequence identity with the rat kidney CaR. Northern analysis demonstrated 7.5 and 4.1 kb transcripts in oligodendrocytes, similar to those in rat parathyroid and kidney, while Western analysis and immunocytochemistry with CaR‐specific antisera showed the presence of CaR protein. Immunocytochemically, the CaR was co‐localized with galactocerebroside in the cultured oligodendrocytes. Raising Ca 0 2+ from 1.8 to 4.8 mM or addition of the polycationic CaR agonist neomycin (300 μM) modestly but significantly increased [ 3 H]‐thymidine incorporation into oligodendrocytes. Elevating Ca 0 2+ from 0.75 to 3.0 mM or addition of 100 μM neomycin also produced 2–2.5‐fold increases in the open state probability (P O ) of an outward K + channel with a unitary conductance of 88 ± 5 pS. Taken together, our data show that the CaR is expressed in immature oligodendrocytes and may be functionally linked to cellular proliferation and an outward K + channel potentially contributing to local ionic homeostasis in the vicinity of oligodendroglia. GLIA 24:449–458, 1998. © 1998 Wiley‐Liss, Inc.