Ultra and molecular structures of the adhesive apparatus occurred in the osteoclasts

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Osteoclasts are specialized in cells that play a central role in bone remodeling. Polarized osteoclasts are equipped with specialized structures called podosomes, dynamic actin rich adhesions, which distribute over the entire ventral membrane. To explore their cytoplasmic and membrane cytoskeletal organizations, we used a three-dimensional(3D) ultrastructural approach to visualize employed a method of"unroofing". Podosomal cytoskeletons are incorporated into a dense network of actin cytoskeletal organization in the lamellipodium. Detyrosinated or acetylated tubulin was detectable in the peripheral cytoplasm of the matured osteoclasts. Posttranslational modifications of microtubules may correlate with characteristic changes in podosome dynamics. On the ventral adherent membranes, an extensive flat clathrin lattice has been shown. Although clathrin-dependent endocytosis is the major pathway for the uptake of nutrients in eukaryotic cells, recent evidence shows that some flat clathrin plaques are apparently restricted to the adherent membrane which may reflect cell adhesion to the substrate.