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Human Plasma Fibronectin Mediates Adhesion of U937 Cells by RGD and CS1
1The First Department of Internal Medicine, Yokohama City University School of Medicine, Yokohama, Japan.
Fibronectin specifically binds to U937 cells (monocytic cell line) in a dose-dependent manner. The specific receptors for the RGD sequence have been identified as alphainfinity 5beta infinity 1wedge alpha infinity: IIb& beta infinity 3, and that for CS1 has been defined as alpha infinity 4& beta infinity 1. RGDS, CS1 peptide, and two peptides together showed similar inhibitory activities on this adhesion, while the 29-kD dispase-digested fragment of the C-terminal heparin-binding domain did not. Thus, the adhesion of fibronectin to U937 cells is mainly mediated by RGDS in the cell-binding domain and CS1 in the alternatively spliced region. Flow cytometry using monoclonal antibodies revealed expressions of alpha infinity 3& beta 1 infinity, alpha4 & beta infinity 1, and alpha infinity 5 beta 1, and not expression of alpha infinity 2 beta infinity 1. Adhesion of U937 cells to fibronectin-coated wells is specific and is inhibited by anti-alpha infinity 4 beta infinity 1 and anti- alpha infinity 5 beta infinity 1 monoclonal antibodies. The IC-50 for anti-alpha infinity 5 beta infinity 1 antibody was almost a log lower than the value for anti-alpha infinity 4 beta infinity 1 antibody. These results demonstrated that interactions of RGDS and CS1 sequence of fibronectin with alpha infinity 5 beta infinity 1 and alpha infinity 4 beta infinity 1& on U937 cells were required for the adhesion of U937 cells to fibronectin. These results may provide further information to understand the mechanism(s) of tumor cell adhesion and atherogenesis.
Fibronectin specifically binds to U937 cells (monocytic cell line) in a dose-dependent manner. The specific receptors for the RGD sequence have been identified as alphainfinity 5beta infinity 1wedge alpha infinity: IIb& beta infinity 3, and that for CS1 has been defined as alpha infinity 4& beta infinity 1. RGDS, CS1 peptide, and two peptides together showed similar inhibitory activities on this adhesion, while the 29-kD dispase-digested fragment of the C-terminal heparin-binding domain did not. Thus, the adhesion of fibronectin to U937 cells is mainly mediated by RGDS in the cell-binding domain and CS1 in the alternatively spliced region. Flow cytometry using monoclonal antibodies revealed expressions of alpha infinity 3& beta 1 infinity, alpha4 & beta infinity 1, and alpha infinity 5 beta 1, and not expression of alpha infinity 2 beta infinity 1. Adhesion of U937 cells to fibronectin-coated wells is specific and is inhibited by anti-alpha infinity 4 beta infinity 1 and anti- alpha infinity 5 beta infinity 1 monoclonal antibodies. The IC-50 for anti-alpha infinity 5 beta infinity 1 antibody was almost a log lower than the value for anti-alpha infinity 4 beta infinity 1 antibody. These results demonstrated that interactions of RGDS and CS1 sequence of fibronectin with alpha infinity 5 beta infinity 1 and alpha infinity 4 beta infinity 1& on U937 cells were required for the adhesion of U937 cells to fibronectin. These results may provide further information to understand the mechanism(s) of tumor cell adhesion and atherogenesis.