Adhesion structures and their cytoskeleton-membrane interactions at podosomes of osteoclasts in culture

• Published in: Cell and tissue research Vol. 331; no. 3; pp. 625 - 641
• Main Authors: Akisaka, Toshitaka, Yoshida, Hisaho, Suzuki, Reiko, Takama, Keiko
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.03.2008; Springer Nature B.V
• Subjects: Actin Cytoskeleton - chemistry; Actin Cytoskeleton - metabolism; Actin Cytoskeleton - ultrastructure; Actins - analysis; Animals; Biomedical and Life Sciences; Biomedicine; Cell adhesion & migration; Cell culture; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cell Surface Extensions - metabolism; Cell Surface Extensions - ultrastructure; Cell-Matrix Junctions - metabolism; Cell-Matrix Junctions - ultrastructure; Cells, Cultured; Cellular biology; Clathrin - analysis; Coated Pits, Cell-Membrane - chemistry; Coated Pits, Cell-Membrane - metabolism; Coated Pits, Cell-Membrane - ultrastructure; Cytoskeleton - metabolism; Cytoskeleton - ultrastructure; Human Genetics; Imaging, Three-Dimensional; Immunohistochemistry; Intermediate Filaments - chemistry; Intermediate Filaments - metabolism; Intermediate Filaments - ultrastructure; Membranes; Microscopy, Electron, Transmission; Microtubules - chemistry; Microtubules - metabolism; Microtubules - ultrastructure; Molecular Medicine; Osteoclasts - cytology; Osteoclasts - metabolism; Osteoclasts - ultrastructure; Proteomics; Rabbits; Regular Article; Tubulin - analysis; Vimentin - analysis; Quick-freezing; Cell shearing; Podosome; Clathrin plaque; Rabbit; Cytoskeleton; Osteoclast
• ISSN: 0302-766X; 1432-0878
• DOI: 10.1007/s00441-007-0552-x

The organization of the cytoskeleton in the podosomes of osteoclasts was studied by use of cell shearing, rotary replication, and fluorescence cytochemical techniques. After shearing, clathrin plaques and particles associated with the cytoskeleton were left behind on the exposed cytoplasmic side of the membrane. The cytoskeleton of the podosomes was characterized by two types of actin filaments: relatively long filaments in the portion surrounding the podosome core, and highly branched short filaments in the core. Individual actin filaments radiating from the podosomes interacted with several membrane particles along the length of the filaments. Many lateral contacts with the membrane surface by the particles were made along the length of individual actin filaments. The polarity of actin filaments in podosomes became oriented such that their barbed ends were directed toward the core of podosomes. The actin cytoskeletons terminated or branched at the podosomes, where the membrane tightly adhered to the substratum. Microtubules were not usually present in the podosome structures; however, certain microtubules appeared to be morphologically in direct contact with the podosome core. Most of the larger clathrin plaques consisted of flat sheets of clathrin lattices that interconnected neighboring clathrin lattices to form an extensive clathrin area. However, the small deeply invaginated clathrin plaques and the podosomal cytoskeleton were located close together. Thus, the clathrin plaques on the ventral membrane of osteoclasts might be involved in both cell adhesion and the formation of receptor-ligand complexes, i.e., endocytosis.