title: RANKL-induced TRPV2 expression regulates osteoclastogenesis via calcium oscillations.
abstract: The receptor activator of NFκB ligand (RANKL) induces Ca(2+) oscillations and activates the Nuclear Factor of Activated T cells 1 (NFATc1) during osteoclast differentiation (osteoclastogenesis). Ca(2+) oscillations are an important trigger signal for osteoclastogenesis, however the molecular basis of Ca(2+) permeable influx pathways serving Ca(2+) oscillations has not yet been identified. Using a DNA microarray, we found that Transient Receptor Potential Vanilloid channels 2 (TRPV2) are expressed significantly in RANKL-treated RAW264.7 cells (preosteoclasts) compared to untreated cells. Therefore, we further investigated the expression and functional role of TRPV2 on Ca(2+) oscillations and osteoclastogenesis. We found that RANKL dominantly up-regulates TRPV2 expression in preosteoclasts, and evokes spontaneous Ca(2+) oscillations and a transient inward cation current in a time-dependent manner. TRPV inhibitor ruthenium red and tetracycline-induced TRPV2 silencing significantly decreased both the frequency of Ca(2+) oscillations and the transient inward currents in RANKL-treated preosteoclasts. Silencing of store-operated Ca(2+) entry (SOCE) proteins similarly suppressed both RANKL-induced oscillations and currents in preosteoclasts. Furthermore, suppression of TRPV2 also reduced RANKL-induced NAFTc1 expression, its nuclear translocation, and osteoclastogenesis. In summary, Ca(2+) oscillations in preosteoclasts are triggered by RANKL-dependent TRPV2 and SOCE activation and intracellular Ca(2+) release. Subsequent activation of NFATc1 promotes osteoclastogenesis.
authors.affiliation: Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Sawara-ku, Fukuoka, Japan. kajiya@college.fdcnet.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kajiya
authors.forename: Fujio
authors.initials: F
authors.lastname: Okamoto
authors.forename: Tetsuomi
authors.initials: T
authors.lastname: Nemoto
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Kimachi
authors.forename: Kazuko
authors.initials: K
authors.lastname: Toh-Goto
authors.forename: Shuji
authors.initials: S
authors.lastname: Nakayana
authors.forename: Koji
authors.initials: K
authors.lastname: Okabe
mesh_terms: D000818:Animals; D001862:Bone Resorption; D015220:Calcium Channels / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D004791:Enzyme Inhibitors; D015870:Gene Expression; D020868:Gene Silencing; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D050778:NFATC Transcription Factors / Q000378:metabolism; D000071740:ORAI1 Protein; D020411:Oligonucleotide Array Sequence Analysis; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D053245:RANK Ligand / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D000071737:Stromal Interaction Molecule 1; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D004791:Enzyme Inhibitors; D008562:Membrane Glycoproteins; D050778:NFATC Transcription Factors; D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse; D053245:RANK Ligand; C100757:Stim1 protein, mouse; D000071737:Stromal Interaction Molecule 1; D050916:TRPV Cation Channels; C485717:Trpv2 protein, mouse; D010738:Type C Phospholipases