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Phorbol myristate acetate enhances degradation of TRH receptor mRNA in a pituitary cell type-specific manner
M C Gershengorn1, C S Narayanan, J Fujimoto
1Department of Medicine, Cornell University Medical College, New York Hospital, New York 10021.
Abstract:
Regulation of the level of thyrotropin-releasing hormone (TRH) receptor (TRH-R) mRNA appears to involve both modulation of gene transcription and of mRNA degradation. To study regulation of TRH-R mRNA degradation and circumvent any physiological effect on transcription, we use cells stably transfected with mouse TRH-R cDNA under control of the constitutively active cytomegalovirus promoter. In stably transfected GH pituitary cells, we find that phorbol 12-myristate 13-acetate (PMA), like TRH, down-regulates TRH-R mRNA by increasing the rate of TRH-R mRNA degradation. In contrast, in stably transfected AtT-20 pituitary cells and in nonpituitary cell lines, neither TRH nor PMA decreased TRH-R mRNA levels. These findings are consistent with the idea that activation of protein kinase C leads to enhanced degradation of TRH-R mRNA in a cell-type-specific manner.
Insights
Thyrotropin-releasing hormone (TRH) receptor mRNA degradation is regulated by protein kinase C activation in a cell-specific manner. This mechanism affects TRH-R mRNA levels in GH pituitary cells but not other cell types.
Area of Science:
- Molecular Endocrinology
- Gene Regulation
- Cell Biology
Background:
- Thyrotropin-releasing hormone (TRH) receptor (TRH-R) mRNA levels are controlled by gene transcription and mRNA degradation.
- Understanding mRNA degradation mechanisms is crucial for comprehending TRH-R regulation.
Purpose of the Study:
- To investigate the regulation of TRH-R mRNA degradation.
- To determine the role of protein kinase C (PKC) in TRH-R mRNA stability.
- To assess the cell-type specificity of TRH-R mRNA degradation regulation.
Main Methods:
- Utilized stably transfected GH pituitary cells, AtT-20 pituitary cells, and nonpituitary cell lines expressing mouse TRH-R cDNA.
- Employed the cytomegalovirus promoter for constitutive TRH-R expression, bypassing transcriptional regulation.
- Administered phorbol 12-myristate 13-acetate (PMA), a PKC activator, and TRH to assess effects on TRH-R mRNA levels and degradation rates.
Main Results:
- Phorbol 12-myristate 13-acetate (PMA) and TRH significantly decreased TRH-R mRNA levels in stably transfected GH pituitary cells.
- This downregulation in GH cells was attributed to an increased rate of TRH-R mRNA degradation.
- Neither TRH nor PMA affected TRH-R mRNA levels in stably transfected AtT-20 pituitary cells or nonpituitary cell lines, indicating cell-type specificity.
Conclusions:
- Activation of protein kinase C enhances the degradation of TRH-R mRNA.
- The regulation of TRH-R mRNA degradation by PKC is cell-type specific.
- These findings provide insights into the post-transcriptional control of TRH receptor expression.