title: Diacylglycerol Kinase ζ (DGKζ) Is a Critical Regulator of Bone Homeostasis Via Modulation of c-Fos Levels in Osteoclasts.
abstract: Increased diacylglycerol (DAG) levels are observed in numerous pathologies, including conditions associated with bone loss. However, the effects of DAG accumulation on the skeleton have never been directly examined. Because DAG is strictly controlled by tissue-specific diacylglycerol kinases (DGKs), we sought to examine the biological consequences of DAG accumulation on bone homeostasis by genetic deletion of DGKζ, a highly expressed DGK isoform in osteoclasts (OCs). Strikingly, DGKζ(-/-) mice are osteoporotic because of a marked increase in OC numbers. In vitro, DGKζ(-/-) bone marrow macrophages (BMMs) form more numerous, larger, and highly resorptive OCs. Surprisingly, although increased DAG levels do not alter receptor activator of NF-κB (RANK)/RANK ligand (RANKL) osteoclastogenic pathway, DGKζ deficiency increases responsiveness to the proliferative and pro-survival cytokine macrophage colony-stimulating factor (M-CSF). We find that M-CSF is responsible for increased DGKζ(-/-) OC differentiation by promoting higher expression of the transcription factor c-Fos, and c-Fos knockdown in DGKζ(-/-) cultures dose-dependently reduces OC differentiation. Using a c-Fos luciferase reporter assay lacking the TRE responsive element, we also demonstrate that M-CSF induces optimal c-Fos expression through DAG production. Finally, to demonstrate the importance of the M-CSF/DGKζ/DAG axis on regulation of c-Fos during osteoclastogenesis, we turned to PLCγ2(+/-) BMMs, which have reduced DAG levels and form fewer OCs because of impaired expression of the master regulator of osteoclastogenesis NFATc1 and c-Fos. Strikingly, genetic deletion of DGKζ in PLCγ2(+/-) mice rescues OC formation and normalizes c-Fos levels without altering NFATc1 expression. To our knowledge, this is the first report implicating M-CSF/DGKζ/DAG axis as a critical regulator of bone homeostasis via its actions on OC differentiation and c-Fos expression.
authors.affiliation: Department of Orthopaedics, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Zamani
authors.affiliation: Department of Orthopaedics, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Corinne
authors.initials: C
authors.lastname: Decker
authors.affiliation: Department of Orthopaedics, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Viviana
authors.initials: V
authors.lastname: Cremasco
authors.affiliation: Department of Orthopaedics, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Lindsey
authors.initials: L
authors.lastname: Hughes
authors.affiliation: Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.|Division of Bone and Mineral, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Deborah V
authors.initials: DV
authors.lastname: Novack
authors.affiliation: Department of Orthopaedics, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: Roberta
authors.initials: R
authors.lastname: Faccio
mesh_terms: D000818:Animals; D019852:Diacylglycerol Kinase / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D016173:Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism*; D051966:Phospholipase C gamma / Q000235:genetics / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis* / Q000235:genetics; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics / Q000378:metabolism; D020218:Response Elements
chemical_list: D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D016760:Proto-Oncogene Proteins c-fos; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D016173:Macrophage Colony-Stimulating Factor; D019852:Diacylglycerol Kinase; C512480:diacylglycerol kinase zeta, mouse; D051966:Phospholipase C gamma
keywords: C-FOS; DAG; DGKζ; M-CSF; OSTEOCLASTS