High-molecular-weight serum protein complexes differentially promote cell migration and the focal adhesion localization of the urokinase receptor in human glioma cells

The distribution of the urokinase-type plasminogen activator receptor (uPAR ) on human glioma cells was examined as a function of culture conditions, u sing immunofluorescence and immunophotoelectron microscopy, Both uPAR coloc alization with focal adhesion proteins and glioma cell motility were maxima l in medium containing whole serum or a serum fraction retained by a 500,00 0 mol wt cutoff centrifugal concentration filter. High motility also took p lace in medium containing a serum fraction passed by the 500,000 cutoff fil ter but retained by a 100,000 cutoff filter and in minimal medium containin g added vitronectin; however, under these conditions only a small percentag e of the otherwise abundant focal adhesions contained colocalized uPAR, Gli oma cells in minimal medium with added laminin migrated with a highly elong ated morphology but without either classical focal adhesions or well-define d uPAR labeling. In contrast, glioma cells in minimal medium with no additi ons did not migrate, nor did they adhere well or display defined labeling p atterns for focal adhesion proteins or uPAR, The results indicate that high -molecular-weight serum protein complexes promote both uPAR focal adhesion colocalization and cell migration in glioma cells. However, conditions can be selected in which migration takes place with minimal uPAR-focal adhesion localization, as well as in the absence of apparent-focal adhesions. (C) 2 000 Academic Press.