Adhesion structures and their cytoskeleton-membrane interactions at podosomes of osteoclasts in culture |
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Authors: | Toshitaka Akisaka Hisaho Yoshida Reiko Suzuki Keiko Takama |
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Institution: | (1) Department of Oral Anatomy, Asahi University School of Dentistry, Hozumi 1851, Mizuho, Gifu 501-0296, Japan;(2) Department of Oral Anatomy, Osaka Dental University, Hirakata 573-1121 Kuzuhahanazono 8-1, Osaka, Japan |
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Abstract: | 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.
This work was supported by the following grants to T.A.: Grants-in-Aid for Scientific Research (C) (18592020) from the Ministry
of Education, Science, and Culture of Japan and the Miyata Research Fund of Asahi University. |
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Keywords: | Osteoclast Podosome Clathrin plaque Cytoskeleton Cell shearing Quick-freezing Rabbit |
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