Rab3D regulates a novel vesicular trafficking pathway that is required for osteoclastic bone resorption.
Rab3 proteins are a subfamily of GTPases, known to mediate membrane transport in eukaryotic cells and play a role in exocytosis. Our data indicate that Rab3D is the major Rab3 species expressed in osteoclasts. To investigate the role of Rab3D in osteoclast physiology we examined the skeletal architecture of Rab3D-deficient mice and found an osteosclerotic phenotype. Although basal osteoclast number in null animals is normal the total eroded surface is significantly reduced, suggesting that the resorptive defect is due to attenuated osteoclast activity. Consistent with this hypothesis, ultrastructural analysis reveals that Rab3D(-/-) osteoclasts exhibit irregular ruffled borders. Furthermore, while overexpression of wild-type, constitutively active, or prenylation-deficient Rab3D has no significant effects, overexpression of GTP-binding-deficient Rab3D impairs bone resorption in vitro. Finally, subcellular localization studies reveal that, unlike wild-type or constitutively active Rab3D, which associate with a nonendosomal/lysosomal subset of post-trans-Golgi network (TGN) vesicles, inactive Rab3D localizes to the TGN and inhibits biogenesis of Rab3D-bearing vesicles. Collectively, our data suggest that Rab3D modulates a post-TGN trafficking step that is required for osteoclastic bone resorption.
Pavlos
Nathan J
NJ
Unit of Orthopaedics, School of Surgery and Pathology, University of Western Australia, 2nd Floor M Block, QEII Medical Centre, Nedlands, Perth, Western Australia 6009, Australia.
Xu
Jiake
J
Riedel
Dietmar
D
Yeoh
Joyce S G
JS
Teitelbaum
Steven L
SL
Papadimitriou
John M
JM
Jahn
Reinhard
R
Ross
F Patrick
FP
Zheng
Ming H
MH
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D001862:Bone Resorption; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002478:Cells, Cultured; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008854:Microscopy, Electron; D015388:Organelles / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000502:physiology*; D010022:Osteopetrosis / Q000378:metabolism / Q000473:pathology; D010641:Phenotype; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013977:Tibia / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D022161:Transport Vesicles / Q000378:metabolism*; D020692:rab3 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism
D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D020033:Protein Isoforms; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D011993:Recombinant Fusion Proteins; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; C116711:Rab3d protein, mouse; D020692:rab3 GTP-Binding Proteins