The regulatory mechanism by which interleukin-6 stimulates GH-gene expression in rat GH3 cells.
The present study was performed to elucidate the effect of interleukin (IL)-6 on the human GH (hGH)-gene expression in GH3 rat pituitary tumor cells using stable transfection of the hGH promoter fused to a luciferase reporter gene. Our results showed that IL-6 (10(2)-10(4) U/ml) stimulated GH secretion and synthesis, and promoted the luciferase expression in stably transfected GH3 cells with the maximal action of 1.99 times above the control by 10(4) U/ml IL-6. Among the inhibitors of signaling transduction pathways, mitogen-activated protein kinase kinase (MAPKK/MEK) inhibitor PD98059 (40 microM) and p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 (5 microM) completely blocked the stimulatory effect of IL-6. Western blot analysis demonstrated that IL-6 indeed increased the activation of phosphorylated MEK and p38 MAPK in GH3 cells. Neither overexpression of Pit-1 nor inhibiting Pit-1 expression affected IL-6 induction of hGH-promoter activity. To identify the DNA sequence that mediated the effect of IL-6, six deletion constructs of hGH promoter were created. The stimulatory effect of IL-6 was abolished following deletion of the -196 to -132 bp fragment. In conclusion, our data show that IL-6 promotes GH secretion and synthesis by rat pituitary GH3 cells. The stimulatory effect of IL-6 on hGH-gene promoter appears to require the activation of MEK and p38 MAPK, and a fragment of promoter sequence that spans the -196 to -132 bp of the gene, but may be unrelated to Pit-1 protein.
Gong
Feng-Ying
FY
Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 1# Shuai Fu Yuan Hu Tong, Dong Dan, Beijing 100730, China. fygong5074@yahoo.com.cn
Shi
Yi-Fan
YF
Deng
Jie-Ying
JY
D000818:Animals; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D005419:Flavonoids / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D013006:Growth Hormone / Q000235:genetics*; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000502:physiology*; D008301:Maleimides / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D009025:Morpholines / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050817:Transcription Factor Pit-1 / Q000235:genetics / Q000378:metabolism; D014162:Transfection / Q000379:methods; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors
D002867:Chromones; D005419:Flavonoids; D007093:Imidazoles; D007211:Indoles; D015850:Interleukin-6; D008301:Maleimides; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011725:Pyridines; D050817:Transcription Factor Pit-1; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D013006:Growth Hormone; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D048051:p38 Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C088060:bisindolylmaleimide; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one