Termination of immediate-early gene expression after stimulation by parathyroid hormone or isoproterenol.
cAMP/PKA signaling transiently stimulates mRNA expression of immediate-early genes, including IL-6 and c-fos. We confirmed that these mRNAs are transiently stimulated by parathyroid hormone (PTH) in ROS 17/2.8 osteoblastic cells. Consistent with the role for cAMP/PKA signaling in this response, PTH induces transient cAMP elevation, PKA activation, and cAMP-responsive element-binding protein (CREB) phosphorylation. Our goal was to determine whether termination of immediate-early gene expression is due to receptor desensitization or cAMP degradation. The approaches used were 1) inhibition of PTH receptor desensitization with G protein-coupled receptor kinase 2 (GRK2) antisense oligonucleotides or antisense plasmids, 2) sustained activation of adenyl cyclase with forskolin, and 3) inhibition of cAMP degradation with 3-isobutyl-1-methylxanthine. These experiments show that mechanisms downstream of receptor desensitization and cAMP degradation are primarily responsible for termination of PKA activity, CREB phosphorylation, and immediate-early gene expression. Similar conclusions were also obtained in response to PTH in a second osteoblastic cell line (MC3T3-E1) and in response to isoproterenol in NIH3T3 fibroblasts. This conclusion may therefore reflect a general mechanism for termination of immediate-early gene expression after induction by cAMP/PKA.
Chen
Xin
X
Department of Orthopaedics, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, Ohio 44106-5000, USA.
Dai
Jia-Chun
JC
Greenfield
Edward M
EM
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D016475:3T3 Cells; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054769:G-Protein-Coupled Receptor Kinase 2; D054770:G-Protein-Coupled Receptor Kinase 3; D015870:Gene Expression / Q000187:drug effects; D017781:Genes, Immediate-Early / Q000502:physiology*; D015850:Interleukin-6 / Q000235:genetics; D007545:Isoproterenol / Q000494:pharmacology*; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D012516:Osteosarcoma; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D018016:Receptors, Parathyroid Hormone / Q000378:metabolism; D013566:Sympathomimetics / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000502:physiology; D051552:beta-Adrenergic Receptor Kinases
D017362:Cyclic AMP Response Element-Binding Protein; D015850:Interleukin-6; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D010726:Phosphodiesterase Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D018016:Receptors, Parathyroid Hormone; D013566:Sympathomimetics; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D054770:G-Protein-Coupled Receptor Kinase 3; C517850:GRK3 protein, mouse; C496569:Grk2 protein, rat; C517851:Grk3 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2; D007545:Isoproterenol; D015056:1-Methyl-3-isobutylxanthine