title: Ubiquitin E3 Ligase LNX2 is Critical for Osteoclastogenesis In Vitro by Regulating M-CSF/RANKL Signaling and Notch2.
abstract: The Notch signaling pathway plays a crucial role in skeletal development and homeostasis by regulating the proliferation and differentiation of osteoblasts and osteoclasts. However, the molecular mechanisms modulating the level and activity of Notch receptors in bone cells remain unknown. In this study, we uncovered that LNX2, an E3 ubiquitin ligase and Notch inhibitor Numb binding protein, was up-regulated during osteoclast differentiation. Knocking-down LNX2 expression in bone marrow macrophages by lentivirus-mediated short hairpin RNAs markedly inhibited osteoclast formation. Decreased LNX2 expression attenuated macrophage colony-stimulating factor (M-CSF)-induced ERK and AKT activation and RANKL-stimulated activation of NF-κB and JNK pathways; therefore, accelerated osteoclast apoptosis. Additionally, loss of LNX2 led to an increased accumulation of Numb, which promoted the degradation of Notch and caused a reduction of the expression of the Notch downstream target gene, Hes1. We conclude that LNX2 regulates M-CSF/RANKL and the Notch signaling pathways during osteoclastogenesis.
authors.affiliation: Department of Orthopedics, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yishan Road, Xuhui District, Shanghai, 200233, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Shiqiao
authors.initials: S
authors.lastname: Ye
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Li
authors.forename: Haibo
authors.initials: H
authors.lastname: Zhao
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000502:physiology*; D015151:Immunoblotting; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000166:cytology* / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D051883:Receptor, Notch2 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C454301:Lnx2 protein, mouse; C497765:Notch2 protein, mouse; D053245:RANK Ligand; D051883:Receptor, Notch2; C505689:Tnfsf11 protein, mouse; D016173:Macrophage Colony-Stimulating Factor