PMID:15485831

Citation	Chaisson, ML, Branstetter, DG, Derry, JM, Armstrong, AP, Tometsko, ME, Takeda, K, Akira, S and Dougall, WC (2004) Osteoclast differentiation is impaired in the absence of inhibitor of kappa B kinase alpha. J. Biol. Chem. 279:54841-8
Abstract	Signaling through the receptor activator of nuclear factor kappa B (RANK) is required for both osteoclast differentiation and mammary gland development, yet the extent to which RANK utilizes similar signaling pathways in these tissues remains unclear. Mice expressing a kinase-inactive form of the inhibitor of kappa B kinase alpha (IKK alpha) have mammary gland defects similar to those of RANK-null mice yet have apparently normal osteoclast function. Because mice that completely lack IKK alpha have severe skin and skeletal defects that are not associated with IKK alpha-kinase activity, we wished to directly examine osteoclastogenesis in IKK alpha(-/-) mice. We found that unlike RANK-null mice, which completely lack osteoclasts, IKK alpha(-/-) mice did possess normal numbers of TRAP(+) osteoclasts. However, only 32% of these cells were multinucleated compared with 57% in wild-type littermates. A more profound defect in osteoclastogenesis was observed in vitro using IKK alpha(-/-) hematopoietic cells treated with colony-stimulating factor 1 and RANK ligand (RANKL), as the cells failed to form large, multinucleated osteoclasts. Additionally, overall RANKL-induced global gene expression was significantly blunted in IKK alpha(-/-) cells, including osteoclast-specific genes such as TRAP, MMP-9, and c-Src. IKK alpha was not required for RANKL-mediated I kappa B alpha degradation or phosphorylation of mitogen-activated protein kinases but was required for RANKL-induced p100 processing. Treatment of IKK alpha(-/-) cells with tumor necrosis factor alpha (TNF alpha) in combination with RANKL led to partial rescue of osteoclastogenesis despite a lack of p100 processing. However, the ability of TNF alpha alone or in combination with transforming growth factor beta to induce osteoclast differentiation was dependent on IKK alpha, suggesting that synergy between RANKL and TNFalpha can overcome p100 processing defects in IKK alpha(-/-) cells.
Links	PubMed Online version:10.1074/jbc.M406392200
Keywords	Acid Phosphatase/genetics; Animals; Carrier Proteins/pharmacology; Cell Differentiation/physiology; Cells, Cultured; Drug Synergism; Embryo, Mammalian; Enzyme Inhibitors; Female; Gene Expression/drug effects; Gene Expression Regulation/drug effects; Genes, src/genetics; Hematopoietic Stem Cells/cytology; Hematopoietic Stem Cells/drug effects; I-kappa B Kinase; I-kappa B Proteins/metabolism; Keratinocytes/cytology; Liver; Macrophage Colony-Stimulating Factor/pharmacology; Male; Matrix Metalloproteinase 9/genetics; Membrane Glycoproteins/pharmacology; Mice; Mice, Knockout; NF-kappa B/physiology; Osteoclasts/cytology; Osteoclasts/metabolism; Protein-Serine-Threonine Kinases/antagonists & inhibitors; Protein-Serine-Threonine Kinases/deficiency; Protein-Serine-Threonine Kinases/physiology; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Transforming Growth Factor beta/pharmacology; Tumor Necrosis Factor-alpha/pharmacology; Tumor Necrosis Factor-alpha/physiology
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