Phorbol Myristate Acetate Enhances Degradation of TRH Receptor mRNA in a Pituitary Cell Type-Specific Manner

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.