title: Osteoclast inhibitory peptide 2 inhibits osteoclast formation via its C-terminal fragment.
abstract: Osteoclast inhibitory peptide 2 (OIP-2) is a novel autocrine/paracrine factor produced by osteoclasts (OCLs) that inhibits bone resorption and OCL formation in vitro and in vivo. It is identical to the asparaginyl endopeptidase legumain. During maturation of OIP-2, a signal peptide and a 17-kDa C-terminal fragment (CTF) are cleaved to produce the mature enzyme. To determine if enzyme activity is required for inhibition of OCL formation or if only the CTF is responsible for these effects, we synthesized His-tagged complementary DNA (cDNA) constructs for the CTF of OIP-2, the proform of OIP-2, and the "mature enzyme" form of OIP-2. The proform or the CTF portion of OIP-2 inhibited OCL formation in a dose-dependent manner in murine bone marrow cultures stimulated with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. The mature form of OIP-2, which was enzymatically active, did not inhibit OCL formation. In addition, OIP-2 inhibited OCL formation in cultures of highly purified human OCL precursor cells or RAW264.7 cells stimulated with 10 ng/ml of receptor activator of NF-kappaB (RANK) ligand. Binding studies with His-tagged OIP-2 showed expression of a putative OIP-2 receptor on RAW264.7 cells treated with RANK ligand for 4 days and human marrow cultures treated with 1,25(OH)2D3 for 3 weeks. These data show that the CTF of OIP-2, rather than the mature enzyme, mediates the inhibitory effects of OIP-2 through a putative receptor on OCL precursors.
authors.affiliation: Department of Medicine/Hematology, University of Texas Health Science Center, San Antonio, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Choi
authors.forename: N
authors.initials: N
authors.lastname: Kurihara
authors.forename: Y
authors.initials: Y
authors.lastname: Oba
authors.forename: G D
authors.initials: GD
authors.lastname: Roodman
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D001862:Bone Resorption; D002117:Calcitriol / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006023:Glycoproteins / Q000235:genetics; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D016296:Mutagenesis; D009842:Oligopeptides / Q000235:genetics; D010010:Osteoclasts / Q000166:cytology*; D053244:Osteoprotegerin; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins; D017434:Protein Structure, Tertiary; D053245:RANK Ligand; D051381:Rats; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor; D000099240:Asparaginyl Endopeptidase
chemical_list: D002117:Calcitriol; D002352:Carrier Proteins; D003546:Cysteine Endopeptidases; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D009842:Oligopeptides; D053244:Osteoprotegerin; D010455:Peptides; D010940:Plant Proteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; D000099240:Asparaginyl Endopeptidase; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C506032:Tnfrsf11b protein, rat; C505689:Tnfsf11 protein, mouse; C047981:arginyl-glycyl-aspartic acid