PHORBOL-MYRISTATE ACETATE ENHANCES DEGRADATION OF TRH RECEPTOR MESSENGER-RNA IN A PITUITARY CELL-TYPE-SPECIFIC MANNER

Regulation of the level of thyrotropin-releasing hormone (TRH) recepto r (TRH-R) mRNA appears to involve both modulation of gene transcriptio n and of mRNA degradation. To study regulation of TRH-R mRNA degradati on and circumvent any physiological effect on transcription, we use ce lls stably transfected with mouse TRH-R cDNA under control of the cons titutively active cytomegalovirus promoter. In stably transfected GH p ituitary cells, we find that phorbol 12-myristate 13-acetate (PMA), li ke TRH, down-regulates TRH-R mRNA by increasing the rate of TRH-R mRNA degradation. In contrast, in stably transfected AtT-20 pituitary cell s and in nonpituitary cell lines, neither TRH nor PMA decreased TRH-R mRNA levels. These findings are consistent with the idea that activati on of protein kinase C leads to enhanced degradation of TRH-R mRNA in a cell-type-specific manner. (C) 1994 Aeademic Press, Inc.