Developmental up-regulation and agonist-dependent down-regulation of GABAA receptor subunit mRNAs in chick cortical neurons

Barnes Jr., Eugene M.; Baumgartner, Brian J.; Harvey, Robert J.; Darlison, Mark G.

Abstract

Research report
We have used quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to analyze the expression of {GABAA} receptor subunit genes in cultured neurons from the chick embryo cerebral cortex. During maturation of the neurons between day 2 and day 8 in culture, levels of the α1 subunit transcript (per ng total RNA) increased 3.8 ± 0.3 fold, while those for the β2S and β4S subunits increased 2.4 ± 0.4 and 1.8 ± 0.2 fold, respectively. The accumulation of the β4S subunit mRNA was more rapid than those encoding either the α1 or β2S polypeptides. After 4 days in culture the β4S subunit transcript level reached 105 ± 7.7% of that found after 8 days, while the corresponding amounts for the α1 and β2S subunit mRNAs were 50 ± 7.1% and 44 ± 10.7%, respectively. On the other hand, no significant differences were observed in the level of either the γ1 or the γ2S subunit mRNA during development in vitro. Likewise, the ratios of the large/small splice variants (β2 = 0.16 ± 0.02; β4 = 0.57 ± 0.02; γ2 = 0.30 ± 0.06) did not show detectable changes during this period. To study the down-regulation of the mRNAs, a single dose of 100 μM {GABA} was added to the culture medium. After 7 days of exposure to GABA, the levels of transcripts for the α1, β2, β4, γ1, and γ2 subunits and their splice variants (where present) were all reduced by 47–65% compared to untreated controls. However, {GABA} treatment for 4 days did not produce a significant change in the level of the α1 subunit mRNA. The subunit specificity observed for developmental up-regulation and the lack of specificity in down-regulation suggests that mRNA down-regulation does not involve suppression of a developmental process. Comparisons with previous work indicate that the GABA-dependent reduction in the levels of subunit transcripts occurs after the loss of {GABAA} receptor binding sites [Hablitz et al., Brain Res., 501 (1989) 332–338] and subunit polypeptides [Calkin and Barnes, J. Biol. Chem., 269 (1994) 1548–1553]. Thus, for the down-regulation of {GABAA} receptors, it appears that translational or post-translational mechanisms may take precedence over the controlled synthesis or stability of subunit mRNAs.

Citation

Barnes Jr., E. M., Baumgartner, B. J., Harvey, R. J., & Darlison, M. G. (1994). Developmental up-regulation and agonist-dependent down-regulation of GABAA receptor subunit mRNAs in chick cortical neurons. Molecular Brain Research, 26(1-2), 9-17. https://doi.org/10.1016/0169-328x%2894%2990068-x

• Journal Article Type: Other
• Publication Date: 1994-10
• Deposit Date: Jul 27, 2016
• Journal: Molecular Brain Research
• Print ISSN: 0169-328X
• Publisher: Elsevier
• Peer Reviewed: Not Peer Reviewed
• Volume: 26
• Issue: 1-2
• Pages: 9-17
• DOI: https://doi.org/10.1016/0169-328x%2894%2990068-x
• Keywords: Molecular Biology; Cellular and Molecular Neuroscience
• Public URL: http://researchrepository.napier.ac.uk/Output/317686
• Publisher URL: http://www.sciencedirect.com/science/article/pii/0169328X9490068X