Alternative regulatory mechanism for the maintenance of bone homeostasis via STAT5-mediated regulation of the differentiation of BMSCs into adipocytes

Seong Semun,Kim Jung Ha,Kim Kabsun,Kim In Young,Koh Jeong-Tae,Kim Nacksung 생화학분자생물학회 2021 Experimental and molecular medicine Vol.53 No.-

STAT5 is a transcription factor that is activated by various cytokines, hormones, and growth factors. Activated STAT5 is then translocated to the nucleus and regulates the transcription of target genes, affecting several biological processes. Several studies have investigated the role of STAT5 in adipogenesis, but unfortunately, its role in adipogenesis remains controversial. In the present study, we generated adipocyte-specific Stat5 conditional knockout (cKO) ( Stat5 fl/fl ;Apn-cre ) mice to investigate the role of STAT5 in the adipogenesis of bone marrow mesenchymal stem cells (BMSCs). BMSC adipogenesis was significantly inhibited upon overexpression of constitutively active STAT5A, while it was enhanced in the absence of Stat5 in vitro. In vivo adipose staining and histological analyses revealed increased adipose volume in the bone marrow of Stat5 cKO mice. ATF3 is the target of STAT5 during STAT5-mediated inhibition of adipogenesis, and its transcription is regulated by the binding of STAT5 to the Atf3 promoter. ATF3 overexpression was sufficient to suppress the enhanced adipogenesis of Stat5- deficient adipocytes, and Atf3 silencing abolished the STAT5-mediated inhibition of adipogenesis. Stat5 cKO mice exhibited reduced bone volume due to an increase in the osteoclast number, and coculture of bone marrow-derived macrophages with Stat5 cKO adipocytes resulted in enhanced osteoclastogenesis, suggesting that an increase in the adipocyte number may contribute to bone loss. In summary, this study shows that STAT5 is a negative regulator of BMSC adipogenesis and contributes to bone homeostasis via direct and indirect regulation of osteoclast differentiation; therefore, it may be a leading target for the treatment of both obesity and bone loss-related diseases.

Pro-inflammatory Cytokines Modulating Osteoclast Differentiation and Function

( Semun Seong ),( Jung Ha Kim ),( Nacksung Kim ) 대한류마티스학회 2016 대한류마티스학회지 Vol.23 No.3

In general, bone homeostasis is maintained through the balance between bone formation and resorption. Disruption in this balance results in bone-related diseases such as osteopetrosis, osteoporosis, and rheumatoid arthritis. Often, enhanced osteoclastogenesis is followed by accelerated bone resorption that is induced by pro-inflammatory cytokines in osteoporosis or rheumatoid arthritis, and leads to bone destruction. In this review study, factors involved in osteoclast differentiation and function are discussed, and how the prevention of such factors is effective in ameliorating bone loss in osteoporosis or rheumatoid arthritis. (J Rheum Dis 2016;23:148-153)

BCAP promotes osteoclast differentiation through regulation of the p38-dependent CREB signaling pathway

Kim, Jung Ha,Kim, Kabsun,Kim, Inyoung,Seong, Semun,Lee, Keun-Bae,Kim, Nacksung Elsevier 2018 Bone Vol.107 No.-

<P><B>Abstract</B></P> <P>Many studies have determined that PI3K-Akt signaling pathways play important roles in osteoclast differentiation and function. In the present study, we investigated the roles of B-cell adaptor for PI3K (BCAP), which is a PI3K binding molecule, in osteoclasts. Overexpression of BCAP in osteoclast precursor cells enhanced osteoclast differentiation induced by tumor necrosis factor alpha (TNF-α) as well as receptor activator of nuclear factor-κB ligand (RANKL). Conversely, osteoclast differentiation mediated by both cytokines was attenuated when BCAP expression was downregulated using small interfering RNA. Notably, BCAP induced Akt activation only upon stimulation by RANKL, but not by TNF-α. However, BCAP activated p38-dependent cAMP response element-binding protein (CREB) phosphorylation induced by both RANKL and TNF-α. Collectively, we showed that BCAP plays an important role in osteoclast differentiation by regulating the p38-dependent CREB signaling pathway, and that BCAP might be a new therapeutic target for bone diseases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> BCAP positively regulates both RANKL- and TNF-α-induced osteoclast differentiation. </LI> <LI> BCAP increases the phosphorylation of Akt by RANKL, but not TNF-α. </LI> <LI> BCAP enhances both RANKL- and TNF-α-induced CREB activation. </LI> <LI> BCAP promotes osteoclast differentiation by regulating p38-dependent CREB signaling pathway rather than PI3K-Akt signaling pathway. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</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>

The IRF2BP2-KLF2 axis regulates osteoclast and osteoblast differentiation

( Inyoung Kim ),( Jung Ha Kim ),( Kabsun Kim ),( Semun Seong ),( Nacksung Kim ) 생화학분자생물학회(구 한국생화학분자생물학회) 2019 BMB Reports Vol.52 No.7

Kruppel-like factor 2 (KLF2) has been implicated in the regulation of cell proliferation, differentiation, and survival in a variety of cells. Recently, it has been reported that KLF2 regulates the p65-mediated transactivation of NF-κB. Although the NF-κB pathway plays an important role in the differentiation of osteoclasts and osteoblasts, the role of KLF2 in these bone cells has not yet been fully elucidated. In this study, we demonstrated that KLF2 regulates osteoclast and osteoblast differentiation. The overexpression of KLF2 in osteoclast precursor cells inhibited osteoclast differentiation by downregulating c-Fos, NFATc1, and TRAP expression, while KLF2 overexpression in osteoblasts enhanced osteoblast differentiation and function by upregulating Runx2, ALP, and BSP expression. Conversely, the downregulation of KLF2 with KLF2-specific siRNA increased osteoclast differentiation and inhibited osteoblast differentiation. Moreover, the overexpression of interferon regulatory protein 2-binding protein 2 (IRF2BP2), a regulator of KLF2, suppressed osteoclast differentiation and enhanced osteoblast differentiation and function. These effects were reversed by downregulating KLF2. Collectively, our data provide new insights and evidence to suggest that the IRF2BP2/KLF2 axis mediates osteoclast and osteoblast differentiation, thereby affecting bone homeostasis. [BMB Reports 2019; 52(7): 469-474]

Tusc2/Fus1 regulates osteoclast differentiation through NF- κB and NFATc1

( Inyoung Kim ),( Jung Ha Kim ),( Kabsun Kim ),( Semun Seong ),( Nacksung Kim ) 생화학분자생물학회(구 한국생화학분자생물학회) 2017 BMB Reports Vol.50 No.9

Tumor suppressor candidate 2 (Tusc2, also known as Fus1) regulates calcium signaling, and Ca²⁺-dependent nuclear factor of activated T-cells (NFAT) and nuclear factor kappa B (NF-кB) pathways, which play roles in osteoclast differentiation. However, the role of Tusc2 in osteoclasts remains unknown. Here, we report that Tusc2 positively regulates the differentiation of osteoclasts. Overexpression of Tusc2 in osteoclast precursor cells enhanced receptor activator of nuclear factor кB ligand (RANKL)-induced osteoclast differentiation. In contrast, small interfering RNA-mediated knockdown of Tusc2 strongly inhibited osteoclast differentiation. In addition, Tusc2 induced the activation of RANKL-mediated NF-кB and calcium/calmodulin-dependent kinase IV (CaMKIV)/cAMP-response element (CRE)-binding protein CREB signaling cascades. Taken together, these results suggest that Tusc2 acts as a positive regulator of RANKL-mediated osteoclast differentiation. [BMB Reports 2017; 50(9): 454-459]

NRROS Negatively Regulates Osteoclast Differentiation by Inhibiting RANKL-Mediated NF-κB and Reactive Oxygen Species Pathways

Kim, Jung Ha,Kim, Kabsun,Kim, Inyoung,Seong, Semun,Kim, Nacksung Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.10

Negative regulator of reactive oxygen species (NRROS) is known to repress ROS generation in phagocytes. In this study, we examined the roles of NRROS in both osteoclasts and osteoblasts. Our results demonstrate that NRROS negatively regulates the differentiation of osteoclasts, but not osteoblasts. Further, overexpression of NRROS in osteoclast precursor cells attenuates RANKL-induced osteoclast differentiation. Conversely, osteoclast differentiation is enhanced upon siRNA-mediated knock-down of NRROS. Additionally, NRROS attenuates RANKL-induced $NF-{\kappa}B$ activation, as well as degradation of the NOX1 and NOX2 proteins, which are required for ROS generation. Based on our observations, we present NRROS as a novel negative regulator of RANKL-induced osteoclastogenesis.

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>