Dynamic changes in the osteoclast cytoskeleton in response to growth factors and cell attachment are controlled by beta3 integrin.
The beta3 integrin cytoplasmic domain, and specifically S752, is critical for integrin localization and osteoclast (OC) function. Because growth factors such as macrophage colony-stimulating factor and hepatocyte growth factor affect integrin activation and function via inside-out signaling, a process requiring the beta integrin cytoplasmic tail, we examined the effect of these growth factors on OC precursors. To this end, we retrovirally expressed various beta3 integrins with cytoplasmic tail mutations in beta3-deficient OC precursors. We find that S752 in the beta3 cytoplasmic tail is required for growth factor-induced integrin activation, cytoskeletal reorganization, and membrane protrusion, thereby affecting OC adhesion, migration, and bone resorption. The small GTPases Rho and Rac mediate cytoskeletal reorganization, and activation of each is defective in OC precursors lacking a functional beta3 subunit. Activation of the upstream mediators c-Src and c-Cbl is also dependent on beta3. Interestingly, although the FAK-related kinase Pyk2 interacts with c-Src and c-Cbl, its activation is not disrupted in the absence of functional beta3. Instead, its activation is dependent upon intracellular calcium, and on the beta2 integrin. Thus, the beta3 cytoplasmic domain is responsible for activation of specific intracellular signals leading to cytoskeletal reorganization critical for OC function.
Faccio
Roberta
R
Department of Pathology, Washington University School of Medicine, 216 South Kingshighway, St. Louis, MO 63110, USA.
Novack
Deborah V
DV
Zallone
Alberta
A
Ross
F Patrick
FP
Teitelbaum
Steven L
SL
D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D001862:Bone Resorption / Q000235:genetics / Q000378:metabolism*; D001842:Bone and Bones / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018821:CD18 Antigens / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D000081247:CSK Tyrosine-Protein Kinase; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051418:Focal Adhesion Kinase 2; D020558:GTP Phosphohydrolases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D006133:Growth Substances / Q000378:metabolism / Q000494:pharmacology; D039661:Integrin beta3 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl; D012694:Serine / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D019061:src-Family Kinases
D018821:CD18 Antigens; D006133:Growth Substances; D039661:Integrin beta3; D011518:Proto-Oncogene Proteins; D012694:Serine; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D051418:Focal Adhesion Kinase 2; C496053:Ptk2b protein, mouse; D019061:src-Family Kinases; D020558:GTP Phosphohydrolases; C493849:Cbl protein, mouse