ABSTRACT
In this study, we analyzed the influence of proteoglycans on the interaction between human high molecular weight kininogen (HK) and the cell surface. We found that D5- related peptide inhibits HK-biotin cellular uptake. Confocal microscopy showed that HK colocalizes with heparan sulfate proteoglycan (HSPG) at the cell surface. When biotin-HK is incubated with rabbit aorta endothelial cells (RAECs) and CHO-K1 cells, it is internalized into acidic intracellular vesicles, whereas when incubated with CHO-745 cells, which express reduced levels of glycosaminoglycans, HK is not internalized. To further verify the hypothesis that HSPG-dependent mechanisms are involved in HK uptake and proteolytic processing in lysosomes, we tested chloroquine, which blocks Alexa 488- HK colocalization with Lyso Tracker in acidic endosomal vesicles. The process of HK internalization was blocked by low temperatures, methyl-beta-cyclodextrin, FCCP and 2-deoxy-D-glucose, implying that HK uptake into acidic vesicles is energy-dependent and most likely involves binding to HSPG structures localized in cholesterol-rich domains present in the plasma membrane. Kinin generation at the cell surface was much higher in tumorigenic cells (CHO-K1) when compared to endothelial cells (RAECs). The present data indicate that the process of HK endocytosis involving HSPG is a novel additional mechanism which may control kinin generation at the cell surface.
