Drs. B. Morte and M. A. Iñiguez have contributed equally to this study.
Thyroid Hormone-Regulated Expression of RC3/Neurogranin in the Immortalized Hypothalamic Cell Line GT1-7
Version of Record online: 18 NOV 2002
Journal of Neurochemistry
Volume 69, Issue 3, pages 902–909, September 1997
How to Cite
Morte, B., Iñiguez, M. A., Lorenzo, P. I. and Bernal, J. (1997), Thyroid Hormone-Regulated Expression of RC3/Neurogranin in the Immortalized Hypothalamic Cell Line GT1-7. Journal of Neurochemistry, 69: 902–909. doi: 10.1046/j.1471-4159.1997.69030902.x
- Issue online: 18 NOV 2002
- Version of Record online: 18 NOV 2002
- Received January 31, 1997; revised manuscript received April 14, 1997; accepted April 21, 1997.
- Gene expression;
Abstract: The calmodulin-binding, protein kinase C substrate RC3/neurogranin is the product of a neuron-specific gene expressed in the forebrain that is under specific regional and temporal control by thyroid hormone (3,5,3′-triiodothyronine, T3). In vivo, some neuronal populations are sensitive and others are insensitive to T3. The goal of this study was to identify neuronal cell cultures that express RC3/neurogranin, to check whether they are sensitive to T3, and to examine the mechanism of regulation. We found that RC3 is induced by T3 in the hypothalamic cell line GT1-7 at the transcriptional level. The half-life of the mature mRNA was 20 h and was not affected by the hormone. Addition of T3 to the cell culture induces neurogranin mRNA after 6 h in the absence of new protein synthesis. These results suggest a direct transcriptional effect of T3 mediated through nuclear receptors. Indeed, GT1-7 cells express functional T3 receptors, as shown by northern blotting, nuclear T3-binding assays, and transactivation of reporter genes. The role of retinoic acid and glucocorticoids on RC3 expression was also evaluated, because we have previously noted the presence of consensus response elements for these hormones in the RC3 upstream promoter region. In contrast to T3, neither retinoic acid nor dexamethasone influences neurogranin expression despite the presence of respective functional receptors.
Abbreviations used: AD, actinomycin D; CAT, chloramphenicol acetyltransferase; Chx, cycloheximide; Cy, cyclophilin; Dex, dexamethasone; β-gal, β-galactosidase; GRE, glucocorticoid response element; H serum, Dowex-treated newborn calf serum; LHRH, gonadotropin-releasing hormone; LTP, long-term potentiation; LTR, long terminal repeat; NSE, neuron-specific enolase; PBS, phosphate-buffered saline; PKC, protein kinase C; RA, retinoic acid; RAR, retinoic acid receptor; RARE, retinoic acid response element; RC3, neuron-specific RC3/neurogranin; RXR, retinoid X receptor or 9-cis-retinoic acid receptor; SDS, sodium dodecyl sulfate; T3, 3,5,3′-triiodothyronine; tk, thymidine kinase; TR, thyroid hormone receptor; T3RE, thyroid hormone response element.