Posttranscriptional up-regulation of thyrotropin-releasing hormone (TRH) receptor messenger ribonucleic acid by TRH in COS-1 cells transfected with mouse pituitary TRH receptor complementary deoxyribonucleic acid

• Published in: Endocrinology (Philadelphia) Vol. 131; no. 4; p. 1716
• Main Authors: Fujimoto, J, Narayanan, C S, Benjamin, J E, Gershengorn, M C
• Format: Journal Article
• Language: English
• Published: United States 01.10.1992
• Subjects: Animals; Cell Line, Transformed; DNA; Haplorhini; Mice - genetics; Pituitary Gland - metabolism; Protein Processing, Post-Translational; Receptors, Neurotransmitter - genetics; Receptors, Neurotransmitter - metabolism; Receptors, Thyrotropin-Releasing Hormone; RNA, Messenger - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Thyrotropin-Releasing Hormone - pharmacology
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.131.4.1716

We found previously that the level of endogenous TRH receptor (TRH-R) mRNA in pituitary (GH3) cells and the level of mouse TRH-R mRNA in GH3 cells stably transfected with mouse pituitary TRH-R cDNA are down-regulated by TRH. This down-regulation is caused by TRH stimulation of TRH-R mRNA degradation via a mechanism that appears to involve protein kinase-C. In this report we study regulation of TRH-R mRNA in monkey kidney (COS-1) cells transiently transfected with mouse pituitary TRH-R cDNA. In transfected COS-1 cells, TRH and phorbol 12-myristate 13-acetate (PMA) caused increases in the level of TRH-R mRNA. In contrast, TRH caused only a small transient increase in the level of the mRNA for the neomycin resistance gene, which was cotransfected with TRH-R, and did not affect the level of the mRNA for glyceraldehyde phosphate dehydrogenase, an endogenous gene. The increases in TRH-R mRNA caused by TRH and PMA were inhibited to similar extents by H-7 (1-[5-isoquinolinesulfonyl]2-methyl piperazine dihydrochloride), an inhibitor of protein kinases. The effect of TRH was observed in cells transfected with expression vectors in which TRH-R cDNA was controlled by cytomegalovirus or Rous sarcoma virus promoters. There was no effect of TRH or PMA on the rate of transcription of the transfected TRH-R cDNA. In contrast, TRH caused the rate of degradation of TRH-R mRNA to decrease from 8.0% to 5.1%/h. Hence, TRH, most likely via a protein kinase-C-mediated mechanism, up-regulates TRH-R mRNA levels in transfected COS-1 cells by decreasing the rate of TRH-R mRNA degradation. Since TRH and PMA down-regulate TRH-R mRNA in GH3 cells, posttranscriptional regulation of TRH-R mRNA is a cell-type specific process.