Role of α(v) integrins in mesangial cell adhesion to vitronectin and von Willebrand factor

Abstract

This study demonstrates (by flow cytometry and immunoprecipitation after cell surface radiolabeling and by using monoclonal antibodies to α(v), β3, and α(v)β3 and α(v)β5 complexes) that α(v)β3, the vitronectin receptor, and α(v)β5 are expressed in vitro on cultured human mesangial cells (HMC) of the 5th to 8th passages. Antibodies to α(v), β3, and α(v)β3 respectively precipitated an αβ heterodimer with molecular weights of 140 and 97 kDa. We analyzed the role of the various integrins in HMC interactions with vitronectin, and with fibronectin and von Willebrand factor (vWf), which are synthetized respectively by mesangial and endothelial cells. Cell adhesion increased in a dose dependent manner with the concentration of plastic-coated matrix protein and vWf. Inhibition of cell attachment with monoclonal antibodies to integrins indicated that HMC adhesion to vWf primarily involves α(v)β3, and that α(v)β5 may also contribute to cell binding to vWf. Adhesion to vitronectin involves both α(v)β3 and α(v)β5 complexes. In contrast, adhesion to fibronectin was not affected by monoclonal antibodies to α(v)β3 and α(v)β5 complexes. We propose that integrins α(v)β3 and α(v)β5, present on HMC, could mediate an interaction between mesangial and endothelial cells by binding to vWf, released at the basal site of endothelial cells.