RANKL-Induced Expression of Tetraspanin CD9 in Lipid Raft Membrane Microdomain Is Essential for Cell Fusion During Osteoclastogenesis

• DOI: 10.1359/jbmr.060308
• Publication Date: 2006-06-05T15:34:04Z
• Authors: Masaru Ishii; Kaori Iwai; Masato Koike; Shiro Ohshima; Eriko Kudo-Tanaka; Taeko Ishii; Toru Mima; Yoshinori Katada; Kunio Miyatake; Yasuo Uchiyama; Yukihiko Saeki
• Keywords: Tetraspanin; Lipid microdomain; Lipid raft; Cell fusion

We showed that CD9, a member of tetraspanin superfamily proteins, is expressed in specific membrane microdomain, called "lipid raft," and crucial for cell fusion during osteoclastogenesis after activation the RANK/RANKL system. Introduction: Osteoclasts are bone-resorbing multinuclear polykaryons essential bone remodeling formed through mononuclear macrophage/monocyte lineage precursors. Although has been shown to be critically regulated by system, mechanism how precursor cells fuse with each other remains unclear. examined function superfamily, which previously form macromolecular microdomains regulate cell–cell various types. Materials Methods: used RAW264.7, line, can differentiate into osteoclast-like on application RANKL. Expression distribution CD9 was assessed Western blotting, fluorescence-assorted sorting (FACS) immunohistochemistry light electron microscopy. A neutralizing antibody RNA interference were inhibit green fluorescent protein (GFP)-CD9 exogenously enhance effect CD9. The lipid microdomain biochemical (sucrose density gradient) isolation imaging technique. Results: surfaces enhanced Targeted inhibition decreases number cells. On hand, overexpression promotes spontaneous even absence localized detergent-insoluble raft" RANKL stimulation, disruption rafts markedly reduces formation polykaryons. Immunohistochemical studies tissues revealed expression osteoclasts vivo. Conclusions: These data suggest its osteoclastogenesis.