Mafb Negatively Regulates RANKL-Mediated Osteoclast Differentiation
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HEMATOPOIESIS MafB negatively regulates RANKL-mediated osteoclast differentiation Kabsun Kim,1 Jung Ha Kim,1 Junwon Lee,1 Hye Mi Jin,1 Hyun Kook,1 Kyung Keun Kim,1 Soo Young Lee,2 and Nacksung Kim1 1Research Institute of Medical Sciences and Medical Research Center for Gene Regulation, Chonnam National University Medical School, Gwangju, Korea; 2Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul, Korea Receptor activator of nuclear factor B phage lineage cells (BMMs) inhibits the transactivation of NFATc1 and OSCAR. Fur- ligand (RANKL) induces osteoclast forma- formation of TRAP؉ multinuclear osteo- thermore, reduced expression of MafB by tion from hematopoietic cells via regula- clasts, but phagocytic activity of BMMs is RNAi enhances osteoclastogenesis and tion of various transcription factors. Here, retained. Furthermore, overexpression of increases expression of NFATc1 and we show that MafB negatively regulates MafB in BMMs attenuates the gene induc- OSCAR. Taken together, our results sug- 2020 31 August on guest by https://ashpublications.org/blood/article-pdf/109/8/3253/1291252/zh800807003253.pdf from Downloaded RANKL-induced osteoclast differentia- tion of NFATc1 and osteoclast-associated gest that MafB can act as an important tion. Expression levels of MafB are signifi- receptor (OSCAR) during RANKL-mediated modulator of RANKL-mediated osteoclas- cantly reduced by RANKL during osteo- osteoclastogenesis. In addition, MafB pro- togenesis. (Blood. 2007;109:3253-3259) clastogenesis. Overexpression of MafB teins interfere with the DNA-binding ability in bone marrow-derived monocyte/macro- of c-Fos, Mitf, and NFATc1, inhibiting their © 2007 by The American Society of Hematology Introduction Bone is continuously remodeled by 2 specialized cells: osteoblasts In addition, NFATc1 synergistically induces OSCAR gene expres- and osteoclasts. Proper balance between bone matrix formation by sion with Mitf.13,14 Therefore, a positive feedback circuit involving osteoblasts and resorption by osteoclasts is essential for proper RANKL, NFATc1, and OSCAR appears to be important for bone metabolism and these processes are tightly regulated by efficient differentiation of osteoclasts.13,15 various hormones and cytokines in local microenvironments. An Maf family proteins have been implicated in eye, hindbrain, and imbalance of these processes can lead to bone diseases such as hematopoietic developement.16-19 Maf proteins share a conserved osteoporosis.1-3 basic region and leucine zipper (bZIP) motif that mediate DNA Current dogma dictates that macrophages, osteoclasts, and binding and dimer formation. Members of the Maf family are dendritic cells originate from bone marrow precursors. Cytokine divided into 2 subgroups: the large Maf proteins (MafA/L-Maf, conditions favoring differentiation into these cell types in vitro MafB/Kreisler, c-Maf, and NRL), which contain an acidic transcrip- have been well defined. For example, granulocyte-macrophage tion-activating domain (TAD) located at their N-terminus, and the colony-stimulating factor (GM-CSF) favors the outgrowth of small Maf proteins (MafK, MafF, and MafG), which contain only dendritic cells from bone marrow progenitors. Macrophage colony- the bZIP region.17,20 stimulating factor (M-CSF) regulates the growth, differentiation, MafB is expressed selectively in monocytes and macrophages, and function of monocytes and macrophages, whereas RANKL but not in other hematopoietic cells.21,22 During macrophage (also called TRANCE, OPGL, and ODF) and M-CSF are essential differentiation, MafB expression is undetectable in multipotent cytokines for the differentiation of osteoclast precursors in bones.2,4,5 progenitors, but is expressed at moderate levels in myeloblasts, and Binding of RANKL to its receptor, receptor activator of nuclear strongly up-regulated in monocytes and macrophages.22 MafB factor B (RANK), activates transcription factors including c-Fos, contributes to the establishment and maintenance of the myelomono- Mi transcription factor (Mitf), PU.1, and nuclear factor of activated cytic phenotype by preventing erythroid-specific gene expres- T cells (NFAT) c1, which are known to be important for osteoclas- sion.22 Overexpression of MafB in transformed myeloblasts stimu- togenesis.1,3,6 Costimulatory signals mediated by immunoreceptor lates the rapid formation of macrophages,23 suggesting that MafB is tyrosine-based activation motif (ITAM)–harboring adaptors, includ- important for macrophage differentiation. ing DNAX-activating protein (DAP) 12 and Fc receptor common ␥ In this study, we have attempted to elucidate the regulatory chain (FcR␥), cooperate with RANKL during osteoclastogenesis, molecules at play during RANKL-mediated osteoclastogenesis by and their activation enhances the induction of NFATc1 via calcium means of microarray analysis. We report that MafB negatively signaling.7-9 Osteoclast-associated receptor (OSCAR) is a member regulates RANKL-induced osteoclastogenesis by interfering with of the immunoglobulin-like surface receptor family and plays an the DNA-binding domains of transcription factors including c-Fos, important role as a costimulatory receptor for osteoclast differentia- Mitf, and NFATc1, thereby inhibiting the transactivation of NFATc1 tion by activating NFATc1 via association with the FcR␥ chain.7,10-12 and OSCAR. Our data suggest that RANKL stimulation skews Submitted September 21, 2006; accepted November 28, 2006. Prepublished online The publication costs of this article were defrayed in part by page charge as Blood First Edition Paper, December 7, 2006; DOI 10.1182/blood-2006-09-048249. payment. Therefore, and solely to indicate this fact, this article is hereby marked ‘‘advertisement’’ in accordance with 18 USC section 1734. The online version of this article contains a data supplement. © 2007 by The American Society of Hematology BLOOD, 15 APRIL 2007 ⅐ VOLUME 109, NUMBER 8 3253 3254 KIM et al BLOOD, 15 APRIL 2007 ⅐ VOLUME 109, NUMBER 8 phagocytic monocytes/macrophages toward a nonphagocytic, bone- CTT CGAAAC T -3Ј;5Ј-TRAP, 5Ј-CTG GAG TGC ACG ATG CCA GCG resorbing osteoclast lineage by overcoming negative regulation of ACA -3Ј;3Ј-TRAP, 5Ј-TCC GTG CTC GGC GAT GGA CCA GA -3Ј; the macrophage factor MafB. 5Ј-HPRT, 5Ј-GTA ATG ATC AGT CAA CGG GGG AC -3Ј;3Ј-HPRT, 5Ј-CCA GCAAGC TTG CAA CCT TAA CCA -3Ј ;5Ј-MafA, 5Ј-GCT TGG AGG AGC GCT TCT CCG ACG -3Ј;3Ј-MafA, 5Ј-CTG CTC CAC CTG GCT CTG GAG CTG -3Ј;5Ј-c-Maf, 5Ј-ATG GCT TCA GAA CTG GCA Materials and methods ATG AAC -3Ј;3Ј-c-Maf, 5Ј-GTC TTC CAG GTG CGC CTT CTG TTC -3Ј;5Ј-NRL, 5Ј-GCT GCA GAA CCA GGG TCC TGT CTC -3Ј;3Ј-NRL, Reagents 5Ј-TTG CAG CCG CTT GGA GCG ACAAGC -3Ј. SB203580, LY294002, PD98059, L-l-tosylamido-2-phenylethyl chloro- methyl ketone (TPCK), and SP600125 were purchased from Calbiochem Real-time PCR (San Diego, CA). Antibodies specific for Flag and actin were from Total RNA was extracted from cultured cells using TRIzol (Invitrogen, Sigma-Aldrich (St Louis, MO); c-Fos from Calbiochem; MafB from Bethyl Carlsbad, CA). First-strand cDNA was transcribed from 1 g RNA using Laboratories (Montgomery, TX); NFATc1 from BD Biosciences (San Jose, Superscript RT (Invitrogen) following the protocol provided by supplier. To CA); GST from Cell Signaling Technology (Beverly, MA); and hemagglu- determine the expression levels of specific genes and HPRT (for endoge- 2020 31 August on guest by https://ashpublications.org/blood/article-pdf/109/8/3253/1291252/zh800807003253.pdf from Downloaded tinin (HA) from Roche Applied Sciences (Indianapolis, IN). A polyclonal nous reference), PCRs were done with the QuantiTect SYBR Green PCR kit antibody for OSCAR was prepared as previously described.13 (Qiagen, Valencia, CA) in triplicates in Rotor-Gene 3000 (Corbett Re- search, Mortlake, Australia). The thermal cycling conditions were as Constructs follows: 15 minutes at 95°C, followed by 40 cycles of 95°C for 30 seconds, MafB was prepared by reverse transcription–polymerase chain reaction 58°C for 30 seconds, and 72°C for 30 seconds. All quantitations were (RT-PCR) using RNA from BMMs. The primer sequences are as follows: normalized to an endogenous control HPRT. The relative quantitation 5Ј-GGA TCC ACC ATG GCC GCG GAG CTG AGC ATG G-3Ј (5Ј-MafB) value for each target gene compared to the calibrator for that target is and 5Ј-GCG GCC GCT TAC AGAAAG AAC TCA GGA GAG GAG G-3Ј expressed as 2Ϫ(CtϪCc) (Ct and Cc are the mean threshold cycle (3Ј-MafB). The amplified PCR fragments were cloned into the pMX-IRES- differences after normalizing to HPRT). The relative expression levels EGFP vector or pGEX-6p. All constructs were confirmed by DNA of samples are presented by semilog plot. sequencing (Korea Basic Science Institute, Gwangju, Korea). The OSCAR reporter vector and expression vectors for Mitf, PU.1, NFATc1, and c-Fos Northern hybridization and Western blot analysis were previously described.13,24 Northern blot analysis was performed as previously described.13 For Osteoclast formation immunoblotting analysis, BMMs were transduced with pMX or pMX- MafB for the indicated times in the presence of M-CSF and RANKL. Cells Murine osteoclasts were prepared from bone marrow cells as previously were washed with ice-cold PBS and lysed in extraction buffer (50 mM described.14,25 In brief, bone marrow cells were cultured in ␣-MEM Tris-HCl, pH 8.0, 150 mM NaCl, 1 mM EDTA, 0.5% Nonidet P-40, and containing 10% FBS with M-CSF (5 ng/mL) for 16 hours. Nonadherent protease inhibitors). Cell lysates were