title: The P75 neurotrophin receptor regulates proliferation of the human MG63 osteoblast cell line.
abstract: The 75 kDa transmembrane protein, p75(NTR), is a marker of mesenchymal stem cells (MSCs). Isolated MSCs are capable of differentiating into osteoblasts, but the molecular function of p75(NTR) in MSCs and osteoblasts is poorly understood. The aim of this study was to examine the function of p75(NTR) in the human MG63 osteoblast cell line compared to the murine MC3T3E-1 pre-osteoblast cell line. MG63 cells and MC3T3-E1 cells expressing exogenous p75(NTR) protein (denoted as p75-MG63 and p75GFP-E1, respectively) were generated to compare osteogenic differentiation and cell proliferation abilities. Overexpression of p75(NTR) induced alkaline phosphatase activity and the mRNA expression of osteoblast-related genes such as osterix and bone sialoprotein in both p75-MG63 and p75GFP-E1. Interestingly, exogenous p75(NTR) stimulated cell proliferation and cell cycle progression in p75GFP-E1, but not in p75-MG63. To elucidate any different effects of p75(NTR) expression on osteogenic differentiation and cell proliferation, we examined the mRNA expression of tropomyosin receptor kinase (trk) genes (trkA, trkB, trkC) and Nogo receptor (NgR), which are binding partners of p75(NTR). Although trkA, trkB, and trkC were detected in both p75-MG63 and p75GFP-E1, only NgR was detected in p75-MG63. We then used the K252a inhibitor of the trks to identify the signaling pathway for osteogenic differentiation and cell proliferation. Inhibition of trks by K252a suppressed p75(NTR)-mediated osteogenic differentiation of p75GFP-E1, whereas deletion of the GDI domain in P75(NTR) from the p75-MG63 produced enhanced cell proliferation compared to p75-MG63. These results suggest that p75(NTR) signaling associated with trk receptors promotes both cell proliferation and osteoblast differentiation, but that p75(NTR)-mediated proliferation may be suppressed by signaling from the p75(NTR)/NgR complex.
authors.affiliation: Nihon University Graduate School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Akiyama
authors.affiliation: Department of Pathology, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Dental Research Center, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Mikami
authors.affiliation: Laboratory of Diagnostic Medicine, The Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Watanabe
authors.affiliation: Laboratory of Diagnostic Medicine, The Institute of Medical Science, The University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Nobukazu
authors.initials: N
authors.lastname: Watanabe
authors.affiliation: Dental Research Center, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Department of Anatomy, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Toriumi
authors.affiliation: Dental Research Center, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Department of Anatomy, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Tomihisa
authors.initials: T
authors.lastname: Takahashi
authors.affiliation: Department of Pathology, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Dental Research Center, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Komiyama
authors.affiliation: Dental Research Center, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Department of Anatomy, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Isokawa
authors.affiliation: Dental Research Center, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Shimizu
authors.affiliation: Dental Research Center, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Department of Anatomy, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan. Electronic address: honda.masaki@nihon-u.ac.jp.
authors.forename: Masaki J
authors.initials: MJ
authors.lastname: Honda
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D002227:Carbazoles / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation; D006801:Humans; D026121:Indole Alkaloids / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010012:Osteogenesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020800:Receptor, Nerve Growth Factor / Q000235:genetics / Q000378:metabolism*; D012795:Sialoglycoproteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D000076182:Sp7 Transcription Factor; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D002227:Carbazoles; D026121:Indole Alkaloids; D012333:RNA, Messenger; D020800:Receptor, Nerve Growth Factor; D012795:Sialoglycoproteins; D000076182:Sp7 Transcription Factor; C478163:SP7 protein, human; D014157:Transcription Factors; C049985:staurosporine aglycone; D020794:Receptor Protein-Tyrosine Kinases; D000469:Alkaline Phosphatase
keywords: Cell proliferation; MC3T-E1 cells; MG63 cells; NgR; p75(NTR); trk