DOK3 Modulates Bone Remodeling by Negatively Regulating Osteoclastogenesis and Positively Regulating Osteoblastogenesis†
| Autor: | Cai, Xiaofeng, Xing, Junjie, Long, Courtney L, Peng, Qisheng, Humphrey, Mary Beth |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
musculoskeletal diseases
Membrane Glycoproteins Osteoblasts Macrophage Colony-Stimulating Factor Macrophages RANK Ligand Osteoclasts Bone Marrow Cells Cell Differentiation Article Mice Inbred C57BL Mice RAW 264.7 Cells Osteogenesis Animals Osteoporosis Bone Remodeling Bone Resorption Phosphorylation Receptors Immunologic Adaptor Proteins Signal Transducing Cell Proliferation Signal Transduction |
| Popis: | Osteoclastogenesis is essential for bone remodeling and normal skeletal maintenance. RANKL promotes osteoclast differentiation and function but requires costimulation of immunoreceptor tyrosine-based activation motif (ITAM)-coupled immunoreceptors. Triggering receptor expressed on myeloid cells-2 (TREM2) coupled to ITAM-adaptor protein DNAX activation protein 12kDA (DAP12) provides costimulation of intracellular calcium signaling during osteoclastogenesis. Previously, we found that downstream of kinase-3 (DOK3) physically associates with DAP12 to inhibit toll-like receptor (TLR)-induced inflammatory signaling in macrophages. However, whether and how DOK3 modulates DAP12-dependent osteoclastogenesis is unknown and the focus of this study. Bone micro-architecture and histology of sex and age matched WT and DOK3-deficient (DOK3-/-) mice were evaluated. Male and female DOK3-/- mice have significantly reduced trabecular bone mass compared to WT mice with increased TRAP+ osteoclasts in vivo. In vitro, DOK3-/- BMMs have increased M-CSF induced proliferation and increased sensitivity to RANKL-induced osteoclastogenesis. Compared to WT, DOK3-/- osteoclasts are significantly larger with more nuclei and have increased resorptive capacity. Mechanistically, DOK3 limits osteoclastogenesis by inhibiting activation of Syk and ERK in response to RANKL and M-CSF. DOK3 is phosphorylated in a DAP12-dependent manner and associates with Grb2 and Cbl. Compared to DAP12-/- mice with high bone mass, DOK3- and DAP12- doubly deficient mice (DKO) have normalized bone mass, indicating that DOK3 also limits DAP12-independent osteoclastogenesis in vivo. In vitro osteoclasts derived from DKO mice are mononuclear with poor resorptive capacity similar to DAP12-/- osteoclasts. Histomorphometry reveals that DOK3-/- mice also have reduced osteoblast parameters. DOK3-/- osteoblasts have reduced in vitro osteoblastogenesis and increased OPG to RANKL expression ratio compared to WT osteoblasts. Co-culture of WT and DOK3-/- osteoblasts with pre-osteoclasts reveals a reduced capacity of DOK3-/- osteoblasts to support osteoclastogenesis. These data indicate that DOK3 regulates bone remodeling by negatively regulating M-CSF and RANKL mediated osteoclastogenesis and positively regulating osteoblastogenesis. |
| Databáze: | OpenAIRE |
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