The Orphan Nuclear Receptor Estrogen Receptor-related Receptor γ Negatively Regulates BMP2-induced Osteoblast Differentiation and Bone Formation

Abstract

Estrogen receptor-related receptor ␥ (ERR␥/ERR3/NR3B3) is a member of the orphan nuclear receptor with important functions in development and homeostasis. Recently it has been reported that ERR␣ is involved in osteoblast differentiation and bone formation. In the present study we examined the role of ERR␥ in osteoblast differentiation. Here, we showed that ERR␥ is expressed in osteoblast progenitors and primary osteoblasts, and its expression is increased temporarily by BMP2. Overexpression of ERR␥ reduced BMP2-induced alkaline phosphatase activity and osteocalcin production as well as calcified nodule formation, whereas inhibition of ERR␥ expression significantly enhanced BMP2-induced osteogenic differentiation and mineralization, suggesting that endogenous ERR␥ plays an important role in osteoblast differentiation. In addition, ERR␥ significantly repressed Runx2 transactivity on osteocalcin and bone sialoprotein promoters. We also observed that ERR␥ physically interacts with Runx2 in vitro and in vivo and competes with p300 to repress Runx2 transactivity. Notably, intramuscular injection of ERR␥ strongly inhibited BMP2-induced ectopic bone formation in a dose-dependent manner. Taken together, these results suggest that ERR␥ is a novel negative regulator of osteoblast differentiation and bone formation via its regulation of Runx2 transactivity.Bone formation is a series of well orchestrated lineage-specific differentiation events (1). Osteoblasts, which play key roles in bone formation, are derived from pluripotent mesenchymal stem cells that have the capacity to differentiate into myocytes, adipocytes, and chondrocytes (2). Osteoblasts possess the necessary components to form bone matrix, which allows subsequent mineralization. Several hormones, growth factors, cytokines, and nuclear receptor proteins regulate these sequential events to trigger a complex network of signaling pathways.Bone morphogenetic proteins (BMPs) 5 are members of the transforming growth factor ␤ family and were originally identified by their capacity to induce ectopic bone formation (3, 4). Among the BMP family members, the action of BMP2 has been studied extensively in embryonic skeletal development, postnatal bone remodeling, and bone repair (5, 6). BMP2 promotes the commitment of pluripotent mesenchymal cells to the osteoblast lineage by regulating the signals that stimulate the specific transcriptional programs required for bone formation (5, 7).A master regulator of osteoblasts, Runx2, is indispensable for a skeletal development and maturation. Targeted disruption of Runx2 results in a complete lack of functional osteoblasts (8, 9). Runx2 directly regulates osteoblast-specific genes such as osteocalcin (OC), bone sialoprotein (BSP), osteopontin, and type I collagen through binding to specific DNA enhancer elements of its target gene promoters (4). In addition, Runx2 interacts with a variety of transcription factors (10) and recruits both co-activators (11-13) and co-repressors (14, 15) to form a complex on its target promoter. Theref...

Estrogen-Related Receptor γ Plays a Key Role in Vascular Calcification Through the Upregulation of BMP2 Expression

“…Taken together, our data indicate that GSK5182 may reduce the risk of cardiovascular morbidity and mortality by attenuating vascular calcification. However, because ERRγ had contrasting roles in mineralization between osteoblasts and VSMCs, 19 it will be necessary to elucidate the tissue-specific role of ERRγ before it can be used as a target in clinical applications.…”

“…17,18 Previously, we reported that ERRγ is expressed in osteoblast progenitors and negatively regulates BMP2-induced osteoblast differentiation and bone formation. 19 However, the role of ERRγ in vascular calcification remains to be determined.…”

Orphan Nuclear Receptor Estrogen-Related Receptor γ (ERRγ) Is Key Regulator of Hepatic Gluconeogenesis

“…Recombinant Adenovirus-Adenoviruses expressing unspecific (US) shRNA, shERR␥, shCRTC2, control GFP, SIK1, SIK2, CRTC2 S171A, A-CREB, and ERR␥ were described previously (6,26,27). All viruses were purified by using CsCl or an Adeno-X Maxi Purification kit (Clontech).…”

An energetic orphan in an endocrine tissue: A revised perspective of the function of estrogen receptor-related receptor alpha in bone and cartilage

“…In this article we do not review these in detail, but they include: (1) small heterodimer partner (SHP), which physically interacts with all three ERRs, repressing their activity (27)(28)(29) ; (2) hypoxia-inducible factor-a (HIF1a), which physically interacts with ERRa to stimulate HIF-induced transcription (30)(31)(32)(33) ; and (3) vascular endothelial growth factor (VEGF), which is a direct target gene of the ERRa/PGC1a complex and HIF1a in muscle and in breast cancer cells. (34,35) Several factors, including prostaglandin E1, BMP, and insulin-like growth factor 1, known to regulate ERRa or g expression and/or activity, also modulate VEGF production in bone cells, suggesting direct VEGF regulation by ERRa/g in OBs and OCs (10,25,38,39) ; (4) aryl hydrocarbon receptor (AhR), which has been reported to interact with ERa and ERRa (40)(41)(42)(43) ; (5) PPARa, which was reported to be directly regulated by ERRa in cardiac myocytes and skeletal muscles (44)(45)(46) ; and (6) Wnt11, which has been shown to be regulated in breast cancer cells by ERRa/b-catenin complex and in C3H10T1/2 cells through its interaction with PGC1a. (12,(47)(48)(49) Recently, we found osteoprotegerin (OPG) regulated in breast cancer cells impacting on bone metastases formation.…”

“…(19,24) ERRg is also involved in osteoblastogenesis and can regulate the bone morphogenic protein 2 (BMP2) pathway. (25) ERRg heterozygote male mice exhibited a slightly but significantly increased bone volume fraction (BV/TV) at 14 weeks, associated with an increased bone mineral content, and increased expression of alkaline phosphatase (ALP) (26) (Cardelli and Aubin, unpublished data).…”