DGKζ Downregulation Enhances Osteoclast Differentiation and Bone Resorption Activity Under Inflammatory Conditions.
Bone homeostasis is maintained by a balance between resorption of the bone matrix and its replacement by new bone. Osteoclasts play a crucially important role in bone metabolism. They are responsible for bone resorption under pathophysiological conditions. Differentiation of these cells, which are derived from bone marrow cells, depends on receptor activator of NF-κB ligand (RANKL). RANKL-induced osteoclastogenesis is regulated by the phosphoinositide (PI) signaling pathway, in which diacylglycerol (DG) serves as a second messenger in signal transduction. In this study, we examined the functional implications of DG kinase (DGK), an enzyme family responsible for DG metabolism, for osteoclast differentiation and activity. Of DGKs, DGKζ is most abundantly expressed in osteoclast precursors such as bone marrow-derived monocytes/macrophages. During osteoclast differentiation from precursor cells, DGKζ is downregulated at the protein level. In this regard, we found that DGKζ deletion enhances osteoclast differentiation and bone resorption activity under inflammatory conditions in an animal model of osteolysis. Furthermore, DGKζ deficiency upregulates RANKL expression in response to TNFα stimulation. Collectively, results suggest that DGKζ is silent under normal conditions, but it serves as a negative regulator in osteoclast function under inflammatory conditions. Downregulation of DGKζ might be one factor predisposing a person to osteolytic bone destruction in pathological conditions. J. Cell. Physiol. 232: 617-624, 2017. © 2016 Wiley Periodicals, Inc.
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.|Department of Orthopaedic, Yamagata University School of Medicine, Yamagata, Japan.
Kiyoshi
K
Iwazaki
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.
Toshiaki
T
Tanaka
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.
Yasukazu
Y
Hozumi
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.
Masashi
M
Okada
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.
Rieko
R
Tsuchiya
Department of Emergency and Critical Care Medicine, Yamagata University School of Medicine, Yamagata, Japan.
Ken
K
Iseki
Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah.
Matthew K
MK
Topham
Department of Anesthesiology, Yamagata University School of Medicine, Yamagata, Japan.
Kaneyuki
K
Kawamae
Department of Orthopaedic, Yamagata University School of Medicine, Yamagata, Japan.
Michiaki
M
Takagi
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata, Japan.
Kaoru
K
Goto
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015519:Bone Density / Q000187:drug effects; D001862:Bone Resorption / Q000150:complications / Q000201:enzymology* / Q000473:pathology*; D002454:Cell Differentiation / Q000187:drug effects; D019852:Diacylglycerol Kinase / Q000378:metabolism*; D004195:Disease Models, Animal; D015536:Down-Regulation; D005347:Fibroblasts / Q000378:metabolism; D007249:Inflammation / Q000150:complications / Q000201:enzymology / Q000473:pathology*; D007527:Isoenzymes / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D018345:Mice, Knockout; D010010:Osteoclasts / Q000187:drug effects / Q000473:pathology*; D010014:Osteolysis / Q000150:complications / Q000201:enzymology / Q000473:pathology; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects
D015415:Biomarkers; D007527:Isoenzymes; D053245:RANK Ligand; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D019852:Diacylglycerol Kinase; C512480:diacylglycerol kinase zeta, mouse