The formation of complexes between human plasminogen activator inhibitor-1 (PAI-1) and sodium dodecyl sulfate: possible implication in the functional properties of PAI-1

Abstract

The effect of the anionic detergent sodium dodecyl sulfate (SDS) on human PAI-1 present in plasma, platelet extracts and endothelial cell cultures, was examined. Using the dye partitional extraction method of Mukerjee ((1956) Anal. Chem. 28, 870–873) to quantitate ionic surfactants, and a discontinuous spectrophotometric assay for the titration of PAI-1 based on the measurement of residual active t-PA, we found (i) that SDS remains tightly bound to PAI-1 after equilibrium dialysis and (ii) that the activity of the latter was closely related to the amount of SDS carried over the PAI-1 solution. The highest concentrations of SDS (ratio of SDS to protein greater than 0.1) were detected in the platelet-derived sources of PAI-1 which also showed the lowest residual t-PA activity. Moreover, it is demonstrated by SDS-PAGE and autoradiography that the tight binding of SDS to PAI-1 decreases its ability to form complexes with t-PA. Similar results were obtained with PAI-1 previously inactivated at 37°C: the inability of PAI-1 to form complexes with t-PA was unchanged after SDS treatment. These observations suggest that the decrease in the residual activity of t-PA observed with the SDS-treated PAI-1 preparations is not related to an increase in the inhibitory activity of PAI-1. In fact, SDS was able to produce a decrease in both the binding of t-PA to fibrin and the activation of plasminogen by fibrindashbound t-PA. Bovine PAI-1 has been shown to exist in a latent SDS-activatable form. Our data indicate that such a form might not be present in the human sources of PAI-1 we have tested.