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 regulated by TSH via cAMP, for which cycloheximide-sensitive protein synthesis might be required, and that more GRP78 might be needed to assist in the synthesis and transport of glycoprotein molecules in TSH-stimulated cells.
Endo
T
T
Third Department of Internal Medicine, University of Yamanashi Medical School, Japan.
Shimura
H
H
Saito
T
T
Ikeda
M
M
Ohmori
M
M
Onaya
T
T
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics*; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D000091342:Endoplasmic Reticulum Chaperone BiP; D004848:Epithelium / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006207:Half-Life; D006360:Heat-Shock Proteins; D007143:Immunoglobulin Heavy Chains / Q000378:metabolism; D007700:Kinetics; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D013961:Thyroid Gland / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*; D014018:Tissue Distribution; D014158:Transcription, Genetic / Q000187:drug effects
D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D007143:Immunoglobulin Heavy Chains; D018832:Molecular Chaperones; D012333:RNA, Messenger; D013972:Thyrotropin; D004247:DNA