Possible involvement of protein kinases and Smad2 signaling pathways on osteoclast differentiation enhanced by activin A.
Bone tissues reportedly contain considerable amounts of activin A and follistatin, an activin A-binding protein. In the present study, we found that follistatin strongly inhibited osteoclast formation in cocultures of mouse bone marrow cells and primary osteoblasts induced by 1alpha,25 dihydroxyvitamin D(3), prostaglandin E(2), and interleukin-1alpha. Antibody aganist activin A also inhibited the osteoclast formation. Furthermore, activin A synergistically stimulated osteoclast differentiation mediated by receptor activator NF-kappaB ligand (RANKL). RT-PCR analysis revealed that osteoblasts produced not only activin A but also follistatin. Western blot analysis of a panel of phosphorylated proteins revealed that activin A stimulated the phosphorylation of p44/42 mitogen activated protein (MAP) kinase (ERK1/2) and p38 MAP kinase in macrophage colony-stimulating factor-dependent bone marrow macrophages (M-BMMPhis). In addition, phosphorylation of Smad2 was observed in M-BMMPhis stimulated with activin A. These findings indicate that the phosphorylation of p44/42 MAP kinase, p38 MAP kinase, and Smad2 is involved in activin A-enhanced osteoclast differentiation induced by RANKL. Taken together, these results suggest that both activin A and follistatin produced by osteoblasts may play an important role in osteoclast differentiation through MAP kinases and Smad2 signaling pathways.
Murase
Y
Y
Department of Periodontology, Aichi Gakuin University, Nagoya, Japan.
Okahashi
N
N
Koseki
T
T
Itoh
K
K
Udagawa
N
N
Hashimoto
O
O
Sugino
H
H
Noguchi
T
T
Nishihara
T
T
D029404:Activin Receptors; D028341:Activins; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000201:enzymology; D002352:Carrier Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D038681:Follistatin; D015870:Gene Expression / Q000502:physiology; D006023:Glycoproteins / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology; D007265:Inhibins / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology* / Q000201:enzymology*; D010766:Phosphorylation; D053245:RANK Ligand; D012333:RNA, Messenger / Q000032:analysis; D053246:Receptor Activator of Nuclear Factor-kappa B; D017978:Receptors, Growth Factor / Q000235:genetics / Q000378:metabolism; D051899:Smad2 Protein; D015534:Trans-Activators / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D038681:Follistatin; D006023:Glycoproteins; D006133:Growth Substances; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D017978:Receptors, Growth Factor; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D015534:Trans-Activators; D028341:Activins; D007265:Inhibins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D029404:Activin Receptors