title: Expression levels of gp130 in bone marrow stromal cells determine the magnitude of osteoclastogenic signals generated by IL-6-type cytokines.
abstract: Interleukin-6 (IL-6)-type cytokines stimulate osteoclast formation by activating the glycoprotein 130 (gp130) receptor subunit on stromal/osteoblastic cells, which in turn leads to signal transducer and activator of transcription 3 (STAT3)-mediated expression of receptor activator of NF-kappaB ligand (RANKL). Based on evidence that gp130 expression is regulated by a variety of cytokines and hormones, we have determined here whether changes in gp130 levels directly contribute to the magnitude of the osteoclastogenic stimulus delivered by IL-6-type cytokines. To accomplish this, gp130 protein levels were modulated using a tetracycline-regulated expression system in a stromal/osteoblastic cell line, UAMS-32, which supports osteoclast formation. Removal of doxycycline from the culture medium elevated gp130 expression and increased the responsiveness of a STAT-responsive promoter-luciferase construct to IL-6 complexed with its soluble receptor (IL-6+sIL-6R), but diminished the responsiveness to oncostatin M (OSM). IL-6+sIL-6R-stimulated osteoclast formation was greater when osteoclast precursors were cocultured with the cells expressing elevated gp130 levels than when cells expressing low gp130 levels were used. However, increased gp130 levels reduced OSM-stimulated osteoclast formation. These results establish that the level of gp130 in stromal/osteoblastic cells directly modulates the magnitude of the osteoclastogenic response to IL-6-type cytokines such that an increase in gp130 increases the cellular responsiveness to IL-6+sIL-6R but reduces responsiveness to OSM.
authors.affiliation: Division of Endocrinology & Metabolism, Department of Medicine, Center for Osteoporosis & Metabolic Bone Diseases, and the McClellan VAMC, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA. obriencharlesa@exchange.uams.edu
authors.forename: C A
authors.initials: CA
authors.lastname: O'Brien
authors.forename: S C
authors.initials: SC
authors.lastname: Lin
authors.forename: T
authors.initials: T
authors.lastname: Bellido
authors.forename: S C
authors.initials: SC
authors.lastname: Manolagas
mesh_terms: D016475:3T3 Cells; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D050822:Cytokine Receptor gp130; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D015848:Interleukin-5 / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D053683:Oncostatin M; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D019947:Receptors, Interleukin-6 / Q000378:metabolism; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D004268:DNA-Binding Proteins; C494200:Il6st protein, mouse; D015848:Interleukin-5; D008562:Membrane Glycoproteins; C508352:Osm protein, mouse; D010455:Peptides; D019947:Receptors, Interleukin-6; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D053683:Oncostatin M; D050822:Cytokine Receptor gp130