Activation of 5-HT receptors that stimulate the adenylyl cyclase pathway positively regulates IGF-I in cultured craniofacial mesenchymal cells.
Results of the present study demonstrate that activation of the adenylyl cyclase/protein kinase A (PKA) pathway leads to increased levels of insulin-like growth factor I (IGF-I) in cultured embryonic mouse mandibular mesenchymal cells. Treatment of serum-free cultures with 10(-8) M 8-OH-DPAT (DPAT) or with 10(-5) M forskolin in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX; 10(-5) M) increased levels of IGF-I (but not IGF-II), as measured by [(125)I]protein A immunobinding. In a previous study, we showed that DPAT, forskolin, IBMX and the 5-HT(4) receptor agonist SC53116 all increased the synthesis of cyclic adenosine monophosphate (cAMP) in these cultures. Taken together, these results provide evidence that stimulation of the adenylyl cyclase/PKA pathway in embryonic mandibular mesenchymal cells positively regulates IGF-I. This is supported by the ability of the PKA inhibitor Rp-cAMPS to block increases in IGF-I caused by both DPAT and forskolin. Consistent with these results, DPAT and forskolin increased phosphorylation of the cAMP response element binding protein (CREB), which was also blocked by Rp-cAMPS. These results suggest that activation of 5-HT receptors positively coupled to the adenylyl cyclase/PKA pathway may promote transcription of IGF-I through a cAMP response element (CRE) in the IGF-I promoter. This may represent one mechanism whereby 5-HT positively regulates IGF-I expression in developing craniofacial mesenchymal cells.
Lambert
H W
HW
Department of Cell Biology and Anatomy, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7090, USA.
Weiss
E R
ER
Lauder
J M
JM
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D008334:Mandible / Q000166:cytology / Q000196:embryology*; D008648:Mesoderm / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000502:physiology; D011985:Receptors, Serotonin / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology
D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D010726:Phosphodiesterase Inhibitors; D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D013873:Thionucleotides; D005576:Colforsin; C016957:adenosine-3',5'-cyclic phosphorothioate; D007334:Insulin-Like Growth Factor I; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D015056:1-Methyl-3-isobutylxanthine