- Thyrotropin-releasing Hormone(TRH) Receptor Gene Expression in GH3 Cells Permanently Transfected with a Mutant Gs alpha Gene.
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Seung Joon Park, In Myung Yang, Sung Vin Yim, Joo Ho Chung, Jee Chang Jung, Kye Chang Ko, Young Seol Kim, Young Kil Choi
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J Korean Endocr Soc. 2000;15(1):46-54. Published online January 1, 2001
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 Abstract
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- BACKGROUND
Gs alpha gene mutation, that constitutively increases intracellular cAMP, is found in some acromegalic patients. It was demonstrated that increased intracellular cAMP levels suppress the expression of rat TRH receptor (TRH-R) mRNA. We previously demonstrated that transient expression of a mutant Gs alpha gene suppress the rat TRH-R gene expression in the cultured rat growth hormone-secreting tumor cell line (GH3), whereas TRH-R gene expression in adenomas with Gs alpha gene mutation (gsp oncogene) did not differ from that in tumors without the mutation. The discrepancy suggests the possibilities that the effect of permanent expression of mutant Gs alpha gene on TRH-R gene expression is different from that of transient expression of the mutant gene and hypothalamic hormones including TRH regulate the gene expression. METHODS: We investigated whether permanent expression of the mutant-type Gs alpha does not suppress the TRH receptor gene expression in GH3 cells, and whether TRH suppresses the gene expression by using reverse transcription-polymerase chain reaction (RT-PCR) and in vitro transcription. RESULTS: Permanent expression of a mutant-type Gs alpha increased basal cAMP levels up to 1.7-fold relative to the controls, whereas the wild-type cell line did not show increased cAMP levels. Permanent expression of a mutant-type Gs alpha increased TRH receptor mRNA level up to 2.8 fold compared with the controls. Treatment of the permanently transfected GH3 cells with TRH suppressed TRH-R gene expression more prominently compared to the wild type GH3 cells. CONCLUSION: These results suggest that permanent expression of mutant Gs alpha enhances the expression of TRH-R in GH-secreting pituitary tumors with gsp oncogene, but the gene expression may also be regulated by other factors including TRH.
- Effect of Ga2 gene mutation on the Expression of Thyrotropin-Releasing Hormone ( TRH ) Receptor Gene in GH3 Cells.
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Seung Joon Park, In Myung Yang, Jeong Hwa Ryu, Joo Ho Chung, Jee Chang Jung, Kye Chang Ko, Young Seol Kim, Young Kil Choi
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J Korean Endocr Soc. 1997;12(3):357-363. Published online January 1, 2001
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- Expression of TRH Receptor Gene in GH-Secreting Piruitary Adenomas.
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In Myung Yang, Seung Joon Park, Jeong Wha Ryu, Joo Ho Chung, Mee Sook Ryu, Jeong Taek Woo, Sung Woon Kim, Jin Woo Kim, Young Seol Kim, Young Kil Choi
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J Korean Endocr Soc. 1997;12(3):349-356. Published online January 1, 2001
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Abstract
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- Background
To test the hypothesis that Galphas gene mutation may suppress the expression of TRH-R gene, we investigated whether hTRH-R gene expression is lower in human GH-secreting pituitary adenomas with Galphas mutation than in tumors without the mutation. Method: TRH-induced paradoxical response of GH was observed in 8 acromegalic patients. The mutation of gene was identified by direct sequencing of the genomic DNA prepared from GH-secreting pituitary adenomas. The expression of hTRHT mRNA was quantitated by RT-PCR. Results: The transcript of hTRH-R gene was detected in 6 of 8(75%) tumors. Three of these(50%) showed the paradoxical GH response to TRH and the other three patients did not show the response. The relative expression of hTRH-R mRNA in the tumors from patients with the paradoxical response of GH to TRH did not differ from that in the tumors from patients without the paradoxical response. Direct PCR sequencing of Galphas disclosed a mutant allele and a normal allele only at codon 201 in 4 of 8 tumors. The paradoxical response to TRH was observed in 2 of 4 patients without the mutation, and 2 of 4 patients with the mutation. The hTRH-R gene expression of pituitary adenomas did not differ between the tumors without the mutation and those with mutation. Conclusion: This study suggests that the expression of TRH-R gene is not likely to be a main determinant for the paradoxical response of GH to TRH, and that Galphas mutation does not seem to suppress the gene expression of TRH-R in GH secreting adenoma.
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