Thyrotropin Stimulates Glucose-Regulated Protein (GRP78) Gene Expression in Rat Functional Thyroid Epithelial Cells, FRTL

We cloned a 1.2-kilobase cDNA (C17–16) from a transformed FRTL thyroid cell library. Northern blot analysis revealed that the size of the corresponding mRNA was 2.0 kilobases. C17–16 mRNA was found in all tissues investigated, but interestingly, its expression was 5- to 10-fold higher in the thyroid glands than in other tissues. Addition of TSH to FRTL cells showed a time- and dose-dependent increase in the steady state level of C17–16 mRNA, and the effect was mimicked by (Bu)2cAMP. An in vitro nuclear run-off assay demonstrated that the stimulatory effect was due to an increase in the transcription rate of the C17–16 gene. TSH had no effect on the half-life of the C17–16 mRNA. Transcriptional induction of the C17–16 gene was inhibited when the cells were treated with cycloheximide. Nucleotide sequencing revealed that C17–16 was identical to the cDNA of rat glucose-regulated protein (GRP78), a member of the heat shock protein family. These results suggest that the expression of GRP78 in thyroid cells is r...