Distinct roles of p130Cas and c-Cbl in adhesion-induced or macrophage colony-stimulating factor-mediated signaling pathways in prefusion osteoclasts.
Both p130Cas and c-Cbl have been reported to play critical roles in osteoclast function as downstream targets of c-Src kinase. The purpose of this study was to examine adhesion- and macrophage colony-stimulating factor (M-CSF)-induced tyrosine phosphorylation of these two molecules in prefusion osteoclasts (pOCs) derived from either Src+/? or Src-/- mice and to directly compare the roles of p130Cas and c-Cbl in osteoclast function. Cell attachment of normal pOCs to vitronectin induces tyrosine phosphorylation of p130Cas and, to a much lesser extent, of c-Cbl. Treatment with M-CSF results in further tyrosine phosphorylation of both p130Cas and c-Cbl, suggesting cooperation between alpha v beta 3 integrin and the M-CSF receptor, c-Fms, in osteoclasts. However, M-CSF induces tyrosine phosphorylation of c-Cbl, but not p130Cas in pOCs in suspension, confirming the role of c-Cbl as a downstream effector of c-Fms. This observation also suggests that M-CSF-mediated p130Cas phosphorylation requires ligand engagement of alpha v beta 3 integrin. In Src-deficient pOCs plated on vitronectin, although M-CSF highly induces Cbl phosphorylation, it does not affect p130Cas phosphorylation. These results suggest that in osteoclasts 1) tyrosine phosphorylation of p130Cas depends on alpha v beta 3 integrin-mediated cell adhesion, even in the presence of M-CSF; 2) on the other hand, c-Cbl phosphorylation is predominantly activated by M-CSF and is independent of cell adhesion; 3) lastly, although c-Src is essential for both adhesion- and M-CSF-mediated phosphorylation of p130Cas, it is clearly not required for c-Cbl phosphorylation in M-CSF-treated pOCs. Taken together, p130Cas and c-Cbl play distinct roles in the signal transduction pathways that mediate cytoskeletal organization in osteoclasts.
Nakamura
Ichiro
I
Department of Bone Biology and Osteoporosis Research, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. ichiclast@aol.com
Rodan
Gideon A
GA
Duong
Le T
LT
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002478:Cells, Cultured; D050719:Crk-Associated Substrate Protein; D016173:Macrophage Colony-Stimulating Factor / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D010010:Osteoclasts / Q000502:physiology*; D010750:Phosphoproteins / Q000502:physiology*; D010766:Phosphorylation; D011506:Proteins; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D050721:Proto-Oncogene Proteins c-cbl; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000172:deficiency / Q000502:physiology; D050717:Retinoblastoma-Like Protein p130; D015398:Signal Transduction / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
C493842:Bcar1 protein, mouse; D050719:Crk-Associated Substrate Protein; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050717:Retinoblastoma-Like Protein p130; D014443:Tyrosine; D016173:Macrophage Colony-Stimulating Factor; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D016392:Proto-Oncogene Proteins pp60(c-src); C067419:CBL protein, human; C493849:Cbl protein, mouse