Oligodendroglial metabotropic glutamate receptors are developmentally regulated and involved in the prevention of apoptosis

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Abstract
Oligodendrocytes (OLs) are responsible for axon myelination and are the principal cells targeted in preterm white matter injury. The cellular and molecular mechanisms involved in white matter development and immature OL injury are incompletely understood. Metabotropic glutamate receptors (mGluRs) modulate neuronal development and survival, and have recently been identified in oligodendrocyte progenitor cells (OPCs). Using the highly homogeneous CG‐4 OPC line and O4 marker‐immunoselected primary OLs, we established the differentiation stage‐specific expression profile of mGluR3 and mGluR5 mRNAs and proteins in the oligodendroglial lineage and type‐2‐astrocytes (ASTs). Our quantitative analysis indicated no changes in mGluR3, but a significant down‐regulation of mGluR5a mRNA and protein expression during differentiation of OPCs into OLs or ASTs. The down‐regulation of mGluR5a had functional consequences, with significantly fewer OLs and ASTs than OPCs responding to the group I mGluR agonist (RS)‐3,5‐dihydroxyphenylglycine with intracellular Ca2+concentration oscillations. Neither stimulation nor inhibition of mGluR3 or mGluR5 altered OPC migration, suggesting that these receptors do not play prominent roles in the regulation of OPC motility. The activation of mGluR5 completely protected OPCs and substantially reduced staurosporine‐induced apoptosis in OLs. This suggests that the down‐regulation of mGluR5 in premyelinating OLs is likely to contribute to their increased vulnerability, and that the targeting of mGluR5 may be a potential therapeutic strategy for future development.