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.
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.
Fujimoto
J
J
Department of Medicine, Cornell University Medical College, New York, New York 10021.
Narayanan
C S
CS
Benjamin
J E
JE
Gershengorn
M C
MC
D000818:Animals; D002461:Cell Line, Transformed; D004247:DNA; D000882:Haplorhini; D051379:Mice / Q000235:genetics; D010902:Pituitary Gland / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism*; D017981:Receptors, Neurotransmitter / Q000235:genetics* / Q000378:metabolism; D018025:Receptors, Thyrotropin-Releasing Hormone; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D012333:RNA, Messenger; D017981:Receptors, Neurotransmitter; D018025:Receptors, Thyrotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone; D004247:DNA; D013755:Tetradecanoylphorbol Acetate