Osteoclast interaction with extracellular matrix drives the sequential events that end with bone resorption. However, the role of matrix proteins is not yet fully understood. We studied this problem on human osteoclast-like cells derived from giant cell tumors of bone (GCT cells). On GCT cells we considered cytoskeletal organization, adhesion properties, and integrin expression upon plating in serum-free medium onto fibronectin (FN), collagen (COL), thrombospondin (TSP), bone sialoprotein (BSPII), and osteopontin (OPN). GCT cells promptly adhered and spread on FN, BSPII, and OPN, while only 50% adhered on COL and none on TSP. The integrin β1 chain was always associated to focal adhesions, while the αvβ3 heterodimer was detected in focal contacts only upon plating on BSPII, OPN, and FN. The focal clustering of β1 was impaired by monensin treatment, indicating that endogenous FN secretion was required to drive β1 into focal contacts. Conversely, αvβ3 clustering was also not affected by monensin when cells were plated onto plasma FN. Immunoprecipitation of metabolically labeled GCT cell lysates showed that three different heterodimers (αvβ3, α3β1, and α5β1) were assembled. Adhesion to FN was completely inhibited by β1 antibodies at dilutions up to 1:400, while β3 antibodies, at similar dilutions, impaired spreading but not adhesion. We conclude that αvβ3 is the main integrin used by GCT cells in bone recognition. We also suggest that selected substrata may induce the release and the organization of endogenous FN that eventually drives the recruitment of a β1 integrin receptor into focal contacts.
|Number of pages||10|
|Journal||Experimental Cell Research|
|Publication status||Published - 1994|
ASJC Scopus subject areas
- Cell Biology