title: Downregulation of small GTPase Rab7 impairs osteoclast polarization and bone resorption.
abstract: During skeletal growth and remodeling the mineralized bone matrix is resorbed by osteoclasts through the constant secretion of protons and proteases to the bone surface. This relies on the formation of specialized plasma membrane domains, the sealing zone and the ruffled border, and vectorial transportation of intracellular vesicles in bone-resorbing osteoclasts. Here we show that Rab7, a small GTPase that is associated with late endosomes, is highly expressed and is predominantly localized at the ruffled border in bone-resorbing osteoclasts. The decreased expression of Rab7 in cultured osteoclasts by antisense oligodeoxynucleotides disrupted the polarization of the osteoclasts and the targeting of vesicles to the ruffled border. These impairments caused a significant inhibition of bone resorption in vitro. The results indicate that the late endocytotic pathway is involved in the osteoclast polarization and bone resorption and underscore the importance of Rab7 in osteoclast function.
authors.affiliation: Department of Anatomy, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, FIN-20520 Turku, Finland. hzhao@pathology.wustl.edu
authors.forename: H
authors.initials: H
authors.lastname: Zhao
authors.forename: T
authors.initials: T
authors.lastname: Laitala-Leinonen
authors.forename: V
authors.initials: V
authors.lastname: Parikka
authors.forename: H K
authors.initials: HK
authors.lastname: Väänänen
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D001862:Bone Resorption; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005109:Extracellular Matrix / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009841:Oligonucleotides / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D010010:Osteoclasts / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D013997:Time Factors; D014168:Transferrin / Q000378:metabolism / Q000493:pharmacokinetics; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000090802:rab7 GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins
chemical_list: D000199:Actins; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D014168:Transferrin; D020691:rab GTP-Binding Proteins; D000090802:rab7 GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C000716466:rab7 GTP-binding proteins, rat