Loss of Cbl-PI3K interaction enhances osteoclast survival due to p21-Ras mediated PI3K activation independent of Cbl-b.
Cbl family proteins, Cbl and Cbl-b, are E3 ubiquitin ligases and adaptor proteins, which play important roles in bone-resorbing osteoclasts. Loss of Cbl in mice decreases osteoclast migration, resulting in delayed bone development where as absence of Cbl-b decreases bone volume due to hyper-resorptive osteoclasts. A major structural difference between Cbl and Cbl-b is tyrosine 737 (in YEAM motif) only on Cbl, which upon phosphorylation interacts with the p85 subunit of phosphatidylinositol-3 Kinase (PI3K). In contrast to Cbl(-/-) and Cbl-b(-/-) , mice lacking Cbl-PI3K interaction due to a Y737F (tyrosine to phenylalanine, YF) mutation showed enhanced osteoclast survival, but defective bone resorption. To investigate whether Cbl-PI3K interaction contributes to distinct roles of Cbl and Cbl-b in osteoclasts, mice bearing CblY737F mutation in the Cbl-b(-/-) background (YF/YF;Cbl-b(-/-) ) were generated. The differentiation and survival were augmented similarly in YF/YF and YF/YF;Cbl-b(-/-) osteoclasts, associated with enhanced PI3K signaling suggesting an exclusive role of Cbl-PI3K interaction, independent of Cbl-b. In addition to PI3K, the small GTPase Ras also regulates osteoclast survival. In the absence of Cbl-PI3K interaction, increased Ras GTPase activity and Ras-PI3K binding were observed and inhibition of Ras activation attenuated PI3K mediated osteoclast survival. In contrast to differentiation and survival, increased osteoclast activity observed in Cbl-b(-/-) mice persisted even after introduction of the resorption-defective YF mutation in YF/YF;Cbl-b(-/-) mice. Hence, Cbl and Cbl-b play mutually exclusive roles in osteoclasts. Whereas Cbl-PI3K interaction regulates differentiation and survival, bone resorption is predominantly regulated by Cbl-b in osteoclasts.
Department of Orthopedic Surgery, University of Connecticut Health Center, Farmington, Connecticut, 06032.
Naga Suresh
NS
Adapala
Mary F
MF
Barbe
Alexander Y
AY
Tsygankov
Joseph A
JA
Lorenzo
Archana
A
Sanjay
D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D015519:Bone Density / Q000235:genetics; D016723:Bone Remodeling / Q000235:genetics; D001862:Bone Resorption / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D058543:Class Ia Phosphatidylinositol 3-Kinase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D009154:Mutation; D010010:Osteoclasts / Q000166:cytology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D053245:RANK Ligand / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics
D048868:Adaptor Proteins, Signal Transducing; C118387:Cblb protein, mouse; D002867:Chromones; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D050721:Proto-Oncogene Proteins c-cbl; D058543:Class Ia Phosphatidylinositol 3-Kinase; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D016283:Proto-Oncogene Proteins p21(ras); C493849:Cbl protein, mouse
AKT; Cbl-b; GSK; RANKL; SURVIVAL