title: Identification and analysis of function of a novel splicing variant of mouse receptor activator of NF-κB.
abstract: Receptor activator of NF-κB (RANK) is a member of the tumor necrosis factor receptor (TNFR) family expressed in osteoclast precursors, and RANK-RANK ligand (RANKL) signaling is a key system for differentiation, activation and survival of osteoclasts. Here, we report the identification of a novel alternative splicing variant of mouse RANK gene (vRANK) that contains a new intervening exon between exon 1 and exon 2 of mouse full-length RANK (fRANK) mRNA. Since this novel exon contains the stop codon, vRANK encodes truncated amino acids that have a portion of the signal peptide of fRANK and an additional 19 amino acids that show no homology to previously reported domains. By transient transfection studies with vRANK-GFP and -Flag expressing constructs, vRANK was found localized mostly in the cytoplasm and partly in the cell membrane, but was not secreted into the culture supernatant. Under the stimulation of various factors, the expression of vRANK mRNA was almost parallel to that of fRANK in RAW264.7 cells not treated with M-CSF. Overexpression of vRANK, on the other hand, decreased TRACP (a marker of osteoclasts) mRNA expression as well as the number of TRACP-positive multinucleated giant cells. While the mRNA expression levels of NFATc1 (a master transcriptional factor of the osteoclast differentiation program) were not affected, apoptotic cells increased significantly in vRAN K-transfected cells treated with sRANKL. Taken together, these results suggest that vRANK is a novel osteoclast suppressor that reduces the number of RANKL-induced mature osteoclasts mainly by negating the anti-apoptotic effect of RANKL.
authors.affiliation: Division of Diagnostic Molecular Pathology, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Satomi
authors.initials: S
authors.lastname: Mukai
authors.forename: Riko
authors.initials: R
authors.lastname: Kitazawa
authors.forename: Junko
authors.initials: J
authors.lastname: Ishii
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kondo
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hakozaki
authors.forename: Keisuke
authors.initials: K
authors.lastname: Horiuchi
authors.forename: Ryuma
authors.initials: R
authors.lastname: Haraguch
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Mori
authors.forename: Sohei
authors.initials: S
authors.lastname: Kitazawa
mesh_terms: D017398:Alternative Splicing / Q000235:genetics / Q000502:physiology*; D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D010010:Osteoclasts / Q000378:metabolism / Q000502:physiology; D020033:Protein Isoforms / Q000032:analysis / Q000235:genetics / Q000502:physiology; D053245:RANK Ligand / Q000502:physiology; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*
chemical_list: D020033:Protein Isoforms; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B