title: Quantitative proteomics reveals ELP2 as a regulator to the inhibitory effect of TNF-α on osteoblast differentiation.
abstract: TNF-α, one of the most potent pro-inflammatory cytokines, plays a critical role in inhibition of osteoblast differentiation and bone regeneration in persistent inflammatory microenvironment. To explore the mechanism, quantitative proteomics based on iTRAQ and MRM was employed. The results showed 6 proteins involved in BMP-2 induced osteoblast differentiation inhibition by TNF-α: Periostin, Protein S100-A4, ATPase inhibitor, Cytochrome b5, SERCA3, and ELP2. The altered proteins were involved in molecular transport, tissue development, energy metabolism, and inflammation. One specific protein, ELP2 (STAT3-interacting protein 1, StIP1) up-regulated in the inhibition of osteoblast differentiation by TNF-α was verified to play a critical role in STAT3 pathway. Overexpression or knockdown of ELP2 in C2C12 and MC3T3-E1 cells affected osteoblast differentiation inhibition induced by TNF-α. These results highlight the function of ELP2 in inflammatory microenvironment, ELP2 up-regulation and STAT3 pathway activation may down-regulate BMPR2, then BMP-2 was blocked and osteoblast differentiation inhibited. The protein-expression profile revealed here should offer at least partly new clues to understand the mechanism of osteoblast differentiation inhibition by inflammation.
  
  
  CONCLUSIONS
  Persistent inflammation is always associated with osteogenesis and affects this balance to reduce bone mass including traumatic open bone fracture, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), but the cellular mechanisms are not fully elucidated. Tumor necrosis factor-α (TNF-α) is one of the most potent pro-inflammatory cytokines and is known to be a catabolic factor in these inflammatory reaction of diseases. We show for the first time using proteomics methods that in inflammatory microenvironment, osteoblast differentiation will be inhibited by TNF-α induced ELP2 up-regulation and STAT3 pathway activation. Our results are significant since they point to targeting ELP2 activity as a novel therapeutic option to limit the inhibition of osteoblast differentiation by inflammatory microenvironment.
authors.affiliation: Guangzhou Institute of Traumatic Surgery, The Fourth Affiliated Hospital of Medical College, Jinan University, Guangzhou, Guangdong, People's Republic of China; Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Chang-Peng
authors.initials: CP
authors.lastname: Xu
authors.affiliation: Department of Orthopaedics, Foshan Hospital of Traditional Chinese Medicine, Guangzhou University of Chinese Medicine, Foshan, Guangdong, People's Republic of China; Key Laboratory of Bone and Cartilage Regenerative Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Xue
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Yan-Jun
authors.initials: YJ
authors.lastname: Hu
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Cui
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Liang
authors.initials: L
authors.lastname: Liang
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
authors.forename: Yi-Lin
authors.initials: YL
authors.lastname: Zhou
authors.affiliation: Department of Pharmacology, Guangdong Medical College, Zhanjiang, Guangdong, People's Republic of China.
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Yang
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China. Electronic address: hospitalnanfang@163.com.
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D060833:Cellular Microenvironment; D015536:Down-Regulation / Q000187:drug effects; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000187:drug effects* / Q000502:physiology; D025941:Protein Interaction Mapping; D040901:Proteomics / Q000379:methods; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: C498805:Elp2 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D014409:Tumor Necrosis Factor-alpha
keywords: ELP2; MRM; Osteoblast differentiation; Quantitative proteomics; TNF-α; iTRAQ