title: Activin A stimulates IkappaB-alpha/NFkappaB and RANK expression for osteoclast differentiation, but not AKT survival pathway in osteoclast precursors.
abstract: Recent studies have reported that activin A enhances osteoclastogenesis in cultures of mouse bone marrow cells stimulated with receptor activator of nuclear factor-kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). However, the exact mechanisms by which activin A functions during osteoclastogenesis are not clear. RANKL stimulation of RANK/TRAF6 signaling increases nuclear factor-kappaB (NFkappaB) nuclear translocation and activates the Akt/PKB cell survival pathway. Here we report that activin A alone activates IkappaB-alpha, and stimulates nuclear translocation of NFkappaB and receptor activator of nuclear factor-kappaB (RANK) expression for osteoclastogenesis, but not Akt/PKB survival signal transduction including BAD and mammalian target of rapamycin (mTOR) for survival in osteoclast precursors in vitro. Activin A alone failed to activate Akt, BAD, and mTOR by immunoblotting, and it also failed to prevent apoptosis in osteoclast precursors. While activin A activated IkappaB-alpha and induced nuclear translocation of phosphorylated-NFkappaB, and it also enhanced RANK expression in osteoclast precursors. Moreover, activin A enhanced RANKL- and M-CSF-stimulated nuclear translocation of NFkappaB. Our data suggest that activin A enhances osteoclastogenesis treated with RANKL and M-CSF via stimulation of RANK, thereby increasing the RANKL stimulation. Activin A alone activated the NFkappaB pathway, but not survival in osteoclast precursors in vitro, but it is, thus, insufficient as a sole stimulus to osteoclastogenesis.
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110, USA. sugatani_t@kids.wustl.edu
authors.forename: T
authors.initials: T
authors.lastname: Sugatani
authors.forename: U M
authors.initials: UM
authors.lastname: Alvarez
authors.forename: K A
authors.initials: KA
authors.lastname: Hruska
mesh_terms: D021581:Active Transport, Cell Nucleus; D028341:Activins / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D006023:Glycoproteins / Q000378:metabolism*; D020672:I-kappa B Proteins / Q000378:metabolism*; D028322:Inhibin-beta Subunits / Q000378:metabolism*; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010010:Osteoclasts / Q000502:physiology*; D053244:Osteoprotegerin; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases; D051025:bcl-Associated Death Protein
chemical_list: C494820:Bad protein, mouse; D002352:Carrier Proteins; D006023:Glycoproteins; D020672:I-kappa B Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D053244:Osteoprotegerin; D011518:Proto-Oncogene Proteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; C422405:activin A; D051025:bcl-Associated Death Protein; D028341:Activins; D000072000:NF-KappaB Inhibitor alpha; D016173:Macrophage Colony-Stimulating Factor; D028322:Inhibin-beta Subunits; D011494:Protein Kinases; C546843:mTOR protein, mouse; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases