Role of manganese in MG-63 osteosarcoma cell attachment to fibrinogen and von Willebrand factor.

Some integrin receptors have been reported to be functionally distinct in different cell types. In endothelial and melanoma cells, the vitronectin receptor, alpha v beta 3 binds fibrinogen (fg) and von Willebrand factor (vWf) in addition to vitronectin itself, whereas it fails to do so in MG-63 osteosarcoma cells. In this report, it is shown that, in the presence of Mn2+, MG-63 cells attach more efficiently to vitronectin and acquire the de novo capacity to adhere to fg- and vWf-coated surfaces. The latter phenomenon occurs with full cell spreading, F-actin microfilament organization, and alpha v and beta 3 clustering at focal contacts. In contrast, beta 1 and beta 5 do not localize to adhesion plaques under the same experimental conditions. An antiserum to the beta 3 chain and a synthetic peptide containing the sequence Gly-Arg-Gly-Asp-Ser-Pro block MG-63 attachment to fg and vWf in the presence of Mn2+. The minimal active concentration of Mn2+ is in the range of 0.1 to 1 microns. These data suggest that the acquired capacity of MG-63 to attach to fg and vWf in the presence of Mn2+ is mediated by alpha v beta 3 and that differences in alpha v beta 3 receptor specificity may be modulated by exogenous factors.