Current topics in pharmacological research on bone metabolism: osteoclast differentiation regulated by glycosphingolipids.
Glycosphingolipids are thought to play important roles in the development and function of several tissues, although the function of glycolipids in osteoclastogenesis has not been clearly demonstrated. In the present study, D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), a glucosylceramide synthase inhibitor, completely inhibited osteoclastogenesis induced by macrophage-colony stimulating factor (M-CSF) and receptor activator of NF-kappaB ligand (RANKL). Following treatment with D-PDMP, nearly all glycosphingolipid expression was dramatically reduced on the surface of bone marrow cells, which suggests that glycosphingolipids are necessary for osteoclastogenesis. To determine which kinds of glycolipids are important for osteoclastogenesis, we added several types of purified glycolipids to D-PDMP treated bone marrow cells, as the precursor of osteoclasts is known to express glucosylceramide (GlcCer) and lactosylceramide (LacCer). Following treatment with RANKL, ganglioside GM3 and GM1 were increased in the treated bone marrow cells, whereas other types were not detected using thin layer chromatography analysis. In cells cultured with those glycolipids, exogenously added LacCer rescued osteoclastogenesis blocking by D-PDMP. Furthermore, receptor activator of nuclear factor kappaB (RANK) induced the recruitment of tumor necrosis factor (TNF)-associated factors 2 and 6 (TRAF2 and 6, respectively) to the cytoplasmic tail of RANKL with activated IkappaB kinase and IkappaB phosphorylation, while D-PDMP treatment inhibited RANKL and induced IkappaB phosphorylation, and that inhibition was recovered by LacCer. In addition, RANK, TRAF2, TRAF6, and LacCer were found localized in lipid rafts on the cell surfaces. These results suggest that glycosphingolipids, especially LacCer, are important for the initial step of RANKL-induced osteoclastogenesis via lipid rafts.
Section of Pediatric Dentistry, Division of Oral Health, Growth and Development, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. fukumoto@dent.kyushu-u.ac.jp
Satoshi
S
Fukumoto
Tsutomu
T
Iwamoto
Eiko
E
Sakai
Kenji
K
Yuasa
Emiko
E
Fukumoto
Aya
A
Yamada
Tomokazu
T
Hasegawa
Kazuaki
K
Nonaka
Yuzo
Y
Kato
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism / Q000494:pharmacology; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D006028:Glycosphingolipids / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007790:Lactosylceramides / Q000378:metabolism / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D015398:Signal Transduction
D015703:Antigens, CD; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D006023:Glycoproteins; D006028:Glycosphingolipids; D007790:Lactosylceramides; D008562:Membrane Glycoproteins; D009025:Morpholines; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; C009744:CDw17 antigen; C033110:RV 538; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase