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Cot kinase promotes Ca2+ oscillation/calcineurin-independent osteoclastogenesis by stabilizing NFATc1 protein.

ABSTRACT: Osteoclasts are multinuclear bone-resorbing cells formed by the fusion of monocyte/macrophage-lineage precursor cells. Activation of the transcription factor NFATc1 (nuclear factor of activated T cells c1) by the receptor activator of NF-?B ligand (RANKL) is critical for osteoclast differentiation. In our previous report (Y. Kuroda, C. Hisatsune, T. Nakamura, K. Matsuo, and K. Mikoshiba. Proc. Natl. Acad. Sci. U. S. A. 105:8643, 2008), we demonstrated that osteoblasts induce osteoclast differentiation via Ca(2+) oscillation/calcineurin-dependent and -independent NFATc1 activation pathways; however, the mechanism underlying the latter remained unclear. Here we show that Cot, a serine/threonine kinase also known as tumor progression locus 2 (Tpl-2), directly phosphorylates all Ca(2+)/calcineurin-regulated NFAT family members (NFATc1 through NFATc4) and increases their protein levels. Moreover, Cot activity in osteoclasts was enhanced via cell-cell interaction with osteoblasts, and Cot promoted Ca(2+) oscillation/calcineurin-independent osteoclastogenesis by increasing NFATc1 stability through phosphorylation. We propose that NFAT activation in vivo occurs via phosphorylation-induced protein stabilization, even in the absence of Ca(2+) oscillation and calcineurin activity.

SUBMITTER: Kuroda Y

PROVIDER: S-EPMC3416192 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Cot kinase promotes Ca2+ oscillation/calcineurin-independent osteoclastogenesis by stabilizing NFATc1 protein.

Kuroda Yukiko Y Kuroda Yukiko Y Hisatsune Chihiro C Mizutani Akihiro A Ogawa Naoko N Matsuo Koichi K Mikoshiba Katsuhiko K

Molecular and cellular biology 20120521 14

Osteoclasts are multinuclear bone-resorbing cells formed by the fusion of monocyte/macrophage-lineage precursor cells. Activation of the transcription factor NFATc1 (nuclear factor of activated T cells c1) by the receptor activator of NF-κB ligand (RANKL) is critical for osteoclast differentiation. In our previous report (Y. Kuroda, C. Hisatsune, T. Nakamura, K. Matsuo, and K. Mikoshiba. Proc. Natl. Acad. Sci. U. S. A. 105:8643, 2008), we demonstrated that osteoblasts induce osteoclast different ...[more]

PMID: 22615493

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Project description:Rationale: Bone homeostasis is maintained by a balanced interplay of osteoblasts and osteoclasts. Osteoclasts are derived from monocyte/macrophage lineage. Major vault protein (MVP) is known to promote apoptosis and prevent metabolic diseases in macrophage. However, whether MVP is involved in osteoclastogenesis is unknown. Here, we identified an important function of MVP as a negative regulator of osteoclastogenesis and its therapeutic potential in preventing bone loss. Methods: Expression of MVP in osteoclasts was investigated in human tumor tissues with immunohistochemical staining. Next, we generated total body (Mvp-/- ) and monocyte-specific (Mvpf/fLyz2-Cre) MVP gene knockout mice to observe bone phenotype and osteoclastogenesis using micro-CT and bone histomorphometry. Moreover, we examined the effects of MVP on osteoclast differentiation, bone resorption, NFATc1 activation and calcium oscillations in vitro. Finally, we explored the clinical potential of targeting MVP in two osteoporosis mouse models and used an adeno-associated virus (AAV) gene to overexpress MVP locally in mice. Results: We found that Mvp-/- and Mvpf/fLyz2-Cre mice both exhibited osteoporosis-like phenotypes. MVP-deficiency also enhanced calcineurin-NFATc1 signaling and promoted NFATc1 activity, which led to enhanced osteoclastogenesis and bone resorption. Calcineurin inhibition using the small molecule inhibitor FK506 corrected the enhanced osteoclastogenesis in Mvpf/fLyz2-Cre group. Additionally, MVP reexpression in Mvpf/fLyz2-Cre group rescued calcineurin expression. MVP overexpression in wild-type mice prevented pathologic bone loss in mouse models of ovariectomized (OVX) and calvaria-adjacent lipopolysaccharide (LPS)-injected. Conclusions: Our data suggested that MVP negatively regulates osteoclast differentiation and bone resorption via inhibition of calcineurin-NFATc1 signaling. In osteoclast-related bone diseases such as osteoporosis, manipulation of MVP activity may be an attractive therapeutic target.

Dataset Information

Cot kinase promotes Ca2+ oscillation/calcineurin-independent osteoclastogenesis by stabilizing NFATc1 protein.

Publications

Cot kinase promotes Ca2+ oscillation/calcineurin-independent osteoclastogenesis by stabilizing NFATc1 protein.

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