MafB negatively regulates RANKL-mediated osteoclast differentiation

Kim, Kabsun,Kim, Jung Ha,Lee, Junwon,Jin, Hye Mi,Kook, Hyun,Kim, Kyung Keun,Lee, Soo Young,Kim, Nacksung American Society of Hematology 2007 Blood Vol.109 No.8

<B>Abstract</B><P>Receptor activator of nuclear factor κB ligand (RANKL) induces osteoclast formation from hematopoietic cells via regulation of various transcription factors. Here, we show that MafB negatively regulates RANKL-induced osteoclast differentiation. Expression levels of MafB are significantly reduced by RANKL during osteoclastogenesis. Overexpression of MafB in bone marrow-derived monocyte/macrophage lineage cells (BMMs) inhibits the formation of TRAP+ multinuclear osteoclasts, but phagocytic activity of BMMs is retained. Furthermore, overexpression of MafB in BMMs attenuates the gene induction of NFATc1 and osteoclast-associated receptor (OSCAR) during RANKL-mediated osteoclastogenesis. In addition, MafB proteins interfere with the DNA-binding ability of c-Fos, Mitf, and NFATc1, inhibiting their transactivation of NFATc1 and OSCAR. Furthermore, reduced expression of MafB by RNAi enhances osteoclastogenesis and increases expression of NFATc1 and OSCAR. Taken together, our results suggest that MafB can act as an important modulator of RANKL-mediated osteoclastogenesis.</P>

Role of CrkII Signaling in RANKL-Induced Osteoclast Differentiation and Function

Kim, Jung Ha,Kim, Kabsun,Kim, Inyoung,Seong, Semun,Nam, Kwang-Il,Lee, Seoung Hoon,Kim, Kyung Keun,Kim, Nacksung The American Association of Immunologists, Inc. 2016 JOURNAL OF IMMUNOLOGY Vol.196 No.3

<P>Rac1, a member of small GTPases, is a key regulator of osteoclast differentiation and function. The Crk family adaptor proteins, consisting of Src homology (SH) 2 and SH3 protein-binding domains, regulate cell proliferation, migration, and invasion through Rac1 activation. In this study, we examined the role of CrkII in osteoclast differentiation and function. Retroviral overexpression of CrkII in osteoclast precursors enhanced osteoclast differentiation and resorptive function through Rac1 activation. The knockdown of CrkII in osteoclast precursors using small interfering RNA inhibited osteoclast differentiation and its resorption activity. Unlike wild-type CrkII, overexpression of the three SH domains in mutant forms of CrkII did not enhance either osteoclast differentiation or function. Phosphorylation of p130 Crk-associated substrate (p130Cas) by osteoclastogenic cytokines in preosteoclasts increased the interaction between p130Cas and CrkII, which is known to be involved in Rac1 activation. Furthermore, transgenic mice over expressing CrkII under control of a tartrate-resistant acid phosphatase promoter exhibited a low bone mass phenotype, associated with increased resorptive function of osteoclasts in vivo. Taken together, our data suggest that the p130Cas/CrkII/Rac1 signaling pathway plays an important role in osteoclast differentiation and function, both in vitro and in vivo.</P>

TRIM38 regulates NF-κB activation through TAB2 degradation in osteoclast and osteoblast differentiation

Kim, Kabsun,Kim, Jung Ha,Kim, Inyoung,Seong, Semun,Kim, Nacksung Elsevier 2018 Bone Vol.113 No.-

<P><B>Abstract</B></P> <P>The tripartite motif protein 38 (TRIM38), a member of the TRIM family, is involved in various cellular processes such as cell proliferation, differentiation, apoptosis, and antiviral defense. However, the role of TRIM38 in osteoclast and osteoblast differentiation is not yet known. In this study, we report the involvement of TRIM38 in osteoclast and osteoblast differentiation. Overexpression of TRIM38, in osteoclast precursor cells, attenuated receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclast formation, RANKL-triggered NF-κB activation, and expression of osteoclast marker genes, such as NFATc1, osteoclast-associated receptor (OSCAR), and tartrate-resistant acid phosphatase (TRAP); and down-regulation of TRIM38 expression showed the opposite effects. Ectopic expression of TRIM38 in osteoblast precursors induced increased osteoblast differentiation and function. Elevated expression of alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin was also observed due to blockade of NF-κB activation. Conversely, knockdown of TRIM38 showed the opposite effects. TRIM38 also induced degradation of lysosome-dependent transforming growth factor beta-activated kinase 1 and MAP3K7-binding protein 2 (TAB2), further blocking NF-κB activation. Taken together, our data suggest that TRIM38 plays a critical role in bone remodeling as a negative regulator of NF-κB in both osteoclast and osteoblast differentiation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TRIM38 expression was regulated during osteoclast and osteoblast differentiation. </LI> <LI> TRIM38 negatively regulates osteoclast differentiation and activity. </LI> <LI> TRIM38 positively regulates osteoblast differentiation and function. </LI> <LI> TRIM38 regulates NF-kB activation through TAB2 degradation in osteoclasts and osteoblasts. </LI> </UL> </P>

Pim-1 regulates RANKL-induced osteoclastogenesis via NF-관B activation and NFATc1 induction.

Kim, Kabsun,Kim, Jung Ha,Youn, Bang Ung,Jin, Hye Mi,Kim, Nacksung Williams Wilkins 2010 JOURNAL OF IMMUNOLOGY Vol.185 No.12

<P>Pim kinases are emerging as important mediators of cytokine signaling pathways in hematopoietic cells. In this study, we demonstrate that Pim-1 positively regulates RANKL-induced osteoclastogenesis and that Pim-1 expression can be upregulated by RANKL signaling during osteoclast differentiation. The silencing of Pim-1 by RNA interference or overexpression of a dominant negative form of Pim-1 (Pim-1 DN) in bone marrow-derived macrophage cells attenuates RANKL-induced osteoclast formation. Overexpression of Pim-1 DN blocks RANKL-induced activation of TGF-관-activated kinase 1 (TAK1) and NF-관B as well as expression of NFATc1 during osteoclastogenesis. However, we found that overexpression of TAK1 in the presence of Pim-1 DN rescues NF-관B activation. Additionally, Pim-1 interacts with RANK as well as TAK1, indicating that Pim-1 is involved in RANKL-induced NF-관B activation via TAK1. Furthermore, we demonstrate that Pim-1 also regulates NFATc1 transcription activity and subsequently induces osteoclast-associated receptor expression, an osteoclast-specific gene. Taken together, our results reveal that Pim-1 positively regulates RANKL-induced osteoclastogenesis.</P>

Kruppel-like factor 4 attenuates osteoblast formation, function, and cross talk with osteoclasts

Kim, Jung Ha,Kim, Kabsun,Youn, Bang Ung,Lee, Jongwon,Kim, Inyoung,Shin, Hong-In,Akiyama, Haruhiko,Choi, Yongwon,Kim, Nacksung The Rockefeller University Press 2014 The Journal of cell biology Vol.204 No.6

<P>KLF4 controls bone homeostasis by negatively regulating both osteoclast and osteoblast differentiation.</P>

MicroRNA-26a Regulates RANKL-Induced Osteoclast Formation

Kim, Kabsun,Kim, Jung Ha,Kim, Inyoung,Lee, Jongwon,Seong, Semun,Park, Yong-Wook,Kim, Nacksung Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.1

Osteoclasts are unique cells responsible for the resorption of bone matrix. MicroRNAs (miRNAs) are involved in the regulation of a wide range of physiological processes. Here, we examined the role of miR-26a in RANKL-induced osteoclastogenesis. The expression of miR-26a was upregulated by RANKL at the late stage of osteoclastogenesis. Ectopic expression of an miR-26a mimic in osteoclast precursor cells attenuated osteoclast formation, actin-ring formation, and bone resorption by suppressing the expression of connective tissue growth factor/CCN family 2 (CTGF/CCN2), which can promote osteoclast formation via upregulation of dendritic cell-specific transmembrane protein (DC-STAMP). On the other hand, overexpression of miR-26a inhibitor enhanced RANKL-induced osteoclast formation and function as well as CTGF expression. In addition, the inhibitory effect of miR-26a on osteoclast formation and function was prevented by treatment with recombinant CTGF. Collectively, our results suggest that miR-26a modulates osteoclast formation and function through the regulation of CTGF.

The transmembrane adaptor protein, linker for activation of T cells (LAT), regulates RANKL-induced osteoclast differentiation

Kim, Kabsun,Kim, Jung Ha,Moon, Jang Bae,Lee, Jongwon,Kwak, Han bok,Park, Yong-Wook,Kim, Nacksung Springer-Verlag 2012 Molecules and cells Vol.33 No.4

Rev-erbα Negatively Regulates Osteoclast and Osteoblast Differentiation through p38 MAPK Signaling Pathway

Kim, Kabsun,Kim, Jung Ha,Kim, Inyoung,Seong, Semun,Kim, Nacksung Korean Society for Molecular and Cellular Biology 2020 Molecules and cells Vol.43 No.1

The circadian clock regulates various physiological processes, including bone metabolism. The nuclear receptors Reverbs, comprising Rev-erbα and Rev-erbβ, play a key role as transcriptional regulators of the circadian clock. In this study, we demonstrate that Rev-erbs negatively regulate differentiation of osteoclasts and osteoblasts. The knockdown of Rev-erbα in osteoclast precursor cells enhanced receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation, as well as expression of nuclear factor of activated T cells 1 (NFATc1), osteoclast-associated receptor (OSCAR), and tartrate-resistant acid phosphatase (TRAP). The overexpression of Rev-erbα leads to attenuation of the NFATc1 expression via inhibition of recruitment of c-Fos to the NFATc1 promoter. The overexpression of Rev-erbα in osteoblast precursors attenuated the expression of osteoblast marker genes including Runx2, alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin (OC). Rev-erbα interfered with the recruitment of Runx2 to the promoter region of the target genes. Conversely, knockdown of Rev-erbα in the osteoblast precursors enhanced the osteoblast differentiation and function. In addition, Rev-erbα negatively regulated osteoclast and osteoblast differentiation by suppressing the p38 MAPK pathway. Furthermore, intraperitoneal administration of GSK4112, a Rev-erb agonist, protects RANKL-induced bone loss via inhibition of osteoclast differentiation in vivo. Taken together, our results demonstrate a molecular mechanism of Rev-erbs in the bone remodeling, and provide a molecular basis for a potential therapeutic target for treatment of bone disease characterized by excessive bone resorption.

Endoplasmic Reticulum–Bound Transcription Factor CREBH Stimulates RANKL-Induced Osteoclastogenesis

Kim, Jung Ha,Kim, Kabsun,Kim, Inyoung,Seong, Semun,Nam, Kwang-Il,Kim, Kyung Keun,Kim, Nacksung American Association of Immunologists 2018 Journal of Immunology Vol. No.

<P>Endoplasmic reticulum (ER) stress is triggered by various metabolic factors, such as cholesterol and proinflammatory cytokines. Recent studies have revealed that ER stress is closely related to skeletal disorders, such as osteoporosis. However, the precise mechanism by which ER stress regulates osteoclast differentiation has not been elucidated. In this study, we identified an ER-bound transcription factor, cAMP response element-binding protein H (CREBH), as a downstream effector of ER stress during RANKL-induced osteoclast differentiation. RANKL induced mild ER stress and the simultaneous accumulation of active nuclear CREBH (CREBH-N) in the nucleus during osteoclastogenesis. Overexpression of CREBH-N in osteoclast precursors enhanced RANKL-induced osteoclast formation through NFATc1 upregulation. Inhibiting ER stress using a specific inhibitor attenuated the expression of osteoclast-related genes and CREBH activation. In addition, inhibition of reactive oxygen species using <I>N</I>-acetylcysteine attenuated ER stress, expression of osteoclast-specific marker genes, and RANKL-induced CREBH activation. Furthermore, inhibition of ER stress and CREBH signaling pathways using an ER stress–specific inhibitor or CREBH small interfering RNAs prevented RANKL-induced bone destruction in vivo. Taken together, our results suggest that reactive oxygen species/ER stress signaling-dependent CREBH activation plays an important role in RANKL-induced osteoclastogenesis. Therefore, inactivation of ER stress and CREBH signaling pathways may represent a new treatment strategy for osteoporosis.</P>

c-Src–Dependent and –Independent Functions of Matk in Osteoclasts and Osteoblasts

Kim, Jung Ha,Kim, Kabsun,Kim, Inyoung,Seong, Semun,Kim, Nacksung American Association of Immunologists 2018 Journal of Immunology Vol. No.

<P>The non-receptor tyrosine kinase c-Src participates in bone metabolism by regulating the activities of both the bone-resorbing osteoclasts and bone-forming osteoblasts. In this study, we investigated whether megakaryocyte-associated tyrosine kinase (Matk), a potent inhibitor of c-Src, affects the functions of murine osteoclasts and osteoblasts. Results revealed that the formation of osteoclasts with actin rings was attenuated by Matk overexpression in osteoclast precursor cells but was enhanced by Matk knockdown. The inhibitory effect of Matk on osteoclasts was closely related with the inhibition of c-Src activity. Intriguingly, Matk overexpression in osteoblasts reduced bone nodule formation. Conversely, Matk knockdown increased osteoblast function. Most importantly, binding of Matk to Runx2 resulted in the inhibition of Runx2 translocation into the nucleus and downregulation of Runx2 target genes. Taken together, our findings demonstrated that Matk plays a critical role in bone metabolism by impairing the functions of osteoclasts and osteoblasts via distinct mechanisms involving inhibition of c-Src–dependent and –independent signaling pathways.</P>