title: Prostaglandin E2 enhances osteoclastic differentiation of precursor cells through protein kinase A-dependent phosphorylation of TAK1.
abstract: Prostaglandin E2 (PGE2) synergistically enhances the receptor activator for NF-kappa B ligand (RANKL)-induced osteoclastic differentiation of the precursor cells. Here we investigated the mechanisms of the stimulatory effect of PGE2 on osteoclast differentiation. PGE2 enhanced osteoclastic differentiation of RAW264.7 cells in the presence of RANKL through EP2 and EP4 prostanoid receptors. RANKL-induced degradation of I kappa B alpha and phosphorylation of p38 MAPK and c-Jun N-terminal kinase in RAW264.7 cells were up-regulated by PGE2 in a cAMP-dependent protein kinase A (PKA)-dependent manner, suggesting that EP2 and EP4 signals cross-talk with RANK signals. Transforming growth factor beta-activated kinase 1 (TAK1), an important MAPK kinase kinase in several cytokine signals, possesses a PKA recognition site at amino acids 409-412. PKA directly phosphorylated TAK1 in RAW264.7 cells transfected with wild-type TAK1 but not with the Ser412 --> Ala mutant TAK1. Ser412 --> Ala TAK1 served as a dominant-negative mutant in PKA-enhanced degradation of I kappa B alpha, phosphorylation of p38 MAPK, and PGE2-enhanced osteoclastic differentiation in RAW264.7 cells. Furthermore, forskolin enhanced tumor necrosis factor alpha-induced I kappa B alpha degradation, p38 MAPK phosphorylation, and osteoclastic differentiation in RAW264.7 cells. Ser412 --> Ala TAK1 abolished the stimulatory effects of forskolin on those cellular events induced by tumor necrosis factor alpha. Ser412 --> Ala TAK1 also inhibited the forskolin-induced up-regulation of interleukin 6 production in RAW264.7 cells treated with lipopolysaccharide. These results suggest that the phosphorylation of the Ser412 residue in TAK1 by PKA is essential for cAMP/PKA-induced up-regulation of osteoclastic differentiation and cytokine production in the precursor cells.
authors.affiliation: Institute for Oral Science, Matsumoto Dental University, Shiojiri, Nagano, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Toshihide
authors.initials: T
authors.lastname: Mizoguchi
authors.forename: Ikuko
authors.initials: I
authors.lastname: Take
authors.forename: Saburo
authors.initials: S
authors.lastname: Kurihara
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Udagawa
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D015232:Dinoprostone / Q000494:pharmacology*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D020930:MAP Kinase Kinase Kinases / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D010766:Phosphorylation; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018078:Receptors, Prostaglandin E / Q000032:analysis / Q000502:physiology; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000099151:MAP Kinase Kinase Kinase 7
chemical_list: D002352:Carrier Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015232:Dinoprostone; D015850:Interleukin-6; D020930:MAP Kinase Kinase Kinases; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7; C545644:PTGER2 protein, human; C545650:PTGER4 protein, human; C545645:Ptger2 protein, mouse; C545651:Ptger4 protein, mouse; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse