beta 3 integrin activation improves alpha v beta 3-mediated retraction of fibrin matrices

Background. Integrins are heterodimeric transmembrane glycoproteins that me diate cell interactions with the extracellular matrix. In vivo, integrin af finity can be modulated by intracellular signaling events. This can be simu lated by a point mutation (D723R) in the cytoplasmic tail of the beta 3 int egrin subunit which results in constitutive activation. The effects of beta 3 integrin activation on the function of alpha v beta 3, an integrin which is important to the adhesive events of multiple cell types, were addressed using Chinese hamster ovary cells expressing either the wild-type (alpha v beta 3 integrin or the mutant alpha v beta 3(D723R). The interactions of t hese cell lines with fibrin matrices were compared. Methods. Receptor expression levels were confirmed by FAGS analyses using a monoclonal anti-alpha v beta 3 antibody. Cell attachment to fibrin-coated dishes was determined after 1 h by fixation and crystal violet staining fol lowed by elution of the dye and OD measurement. Fibrin clot retraction was measured by culturing cells in fibrin clots for 24 h, The clots were detach ed from the dish and the surface area was calculated at individual time poi nts. Results. CHO alpha v beta 3(D723R) cells displayed a greater than twofold i ncrease in attachment to fibrinogen or to fibrin matrices when compared to wild-type transfectants, Further, CHO alpha v beta 3(D723R) cell retraction of fibrin matrices was significantly greater at nearly all time points. Conclusion. Activation of the beta 3 integrin subunit significantly improve s the interaction of alpha v beta 3 with fibrin and may play a role in the integrin-mediated signaling events which occur following vascular injury (C ) 1999 Academic Press.