title: Parathyroid hormone induces expression of the inducible cAMP early repressor in osteoblastic MC3T3-E1 cells and mouse calvariae.
abstract: Parathyroid hormone (PTH) regulates gene expression in skeletal osteoblasts mainly through the cAMP-protein kinase A (PKA) pathway. In neuroendocrine cells, activation of the cAMP-PKA signaling pathway leads to induction of the inducible cAMP early repressor (ICER), which is transcribed from an intronic promoter of the CREM gene and acts as a transcriptional repressor. To investigate whether PTH induces ICER expression in osteoblastic cells, RNA from MC3T3-E1 cells was subjected to reverse transcriptase-polymerase chain reaction using primers spanning the ICER sequence. Amplified products were subcloned, sequenced, and used as a probe for Northern blot analysis. In MC3T3-E1 cells, PTH induced ICER mRNA levels, which peaked at 2 h and declined to baseline by 8 h. Cycloheximide caused superinduction of ICER mRNA in response to PTH. In cultured mouse calvariae, PTH also induced ICER mRNA accumulation, which peaked at 2 h and returned almost to baseline by 10 h. Overexpression of ICER IIgamma decreased both baseline and PTH-stimulated prostaglandin G/H synthase 2 promoter activity in MC3T3-E1 cells. The induction of ICER represents a novel mechanism by which PTH regulates gene expression in osteoblastic cells.
authors.affiliation: Department of Oral Diagnosis, School of Dental Medicine, The University of Connecticut Health Center, Farmington, Connecticut, USA.
authors.forename: S
authors.initials: S
authors.lastname: Tetradis
authors.forename: J M
authors.initials: JM
authors.lastname: Nervina
authors.forename: K
authors.initials: K
authors.lastname: Nemoto
authors.forename: B E
authors.initials: BE
authors.lastname: Kream
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis*; D051786:Cyclic AMP Response Element Modulator; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D051546:Cyclooxygenase 2; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D007438:Introns; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics; D012886:Skull
chemical_list: D004268:DNA-Binding Proteins; D007527:Isoenzymes; D010281:Parathyroid Hormone; D011500:Protein Synthesis Inhibitors; D012097:Repressor Proteins; D051786:Cyclic AMP Response Element Modulator; D003513:Cycloheximide; D000242:Cyclic AMP; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D017868:Cyclic AMP-Dependent Protein Kinases