Apatite-mediated actin dynamics in resorbing osteoclasts.
The actin cytoskeleton is essential for osteoclasts main function, bone resorption. Two different organizations of actin have been described in osteoclasts, the podosomes belt corresponding to numerous F-actin columns arranged at the cell periphery, and the sealing zone defined as a unique large band of actin. To compare the role of these two different actin organizations, we imaged osteoclasts on various substrata: glass, dentin, and apatite. Using primary osteoclasts expressing GFP-actin, we found that podosome belts and sealing zones, both very dynamic actin structures, were present in mature osteoclasts; podosome belts were observed only in spread osteoclasts adhering onto glass, whereas sealing zone were seen in apico-basal polarized osteoclasts adherent on mineralized matrix. Dynamic observations of several resorption cycles of osteoclasts seeded on apatite revealed that 1) podosomes do not fuse together to form the sealing zone; 2) osteoclasts alternate successive stationary polarized resorption phases with a sealing zone and migration, nonresorption phases without any specific actin structure; and 3) apatite itself promotes sealing zone formation though c-src and Rho signaling. Finally, our work suggests that apatite-mediated sealing zone formation is dependent on both c-src and Rho whereas apico-basal polarization requires only Rho.
Saltel
Frédéric
F
Laboratoire de Biologie Moléculaire de la Cellule, ENS/CNRS 5161, IFR 128 Biosciences Lyon-Gerland, 69007 Lyon, France.
Destaing
Olivier
O
Bard
Frédéric
F
Eichert
Diane
D
Jurdic
Pierre
P
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001031:Apatites / Q000494:pharmacology*; D001862:Bone Resorption / Q000378:metabolism* / Q000473:pathology*; D000081247:CSK Tyrosine-Protein Kinase; D002454:Cell Differentiation; D002465:Cell Movement; D016764:Cell Polarity; D002478:Cells, Cultured; D006801:Humans; D008297:Male; D051379:Mice; D008855:Microscopy, Electron, Scanning; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism; D019061:src-Family Kinases
D000199:Actins; D001031:Apatites; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D020741:rho GTP-Binding Proteins