ALTERED IN-VITRO SPREADING AND CYTOSKELETAL ORGANIZATION IN HUMAN GLIOMA-CELLS BY DOWN-REGULATION OF UROKINASE RECEPTOR

The interaction of urokinase-type plasminogen activator (UPA) with its cell-surface receptor (uPAR) is implicated in diverse biological proc esses such as cell migration, tissue remodeling, and tumor cell invasi on. Recent studies indicated that uPAR can act as an extracellular mat rix receptor during cell adhesion. Recently, we showed that transfecti on of the human glioma cell line SNB19 with antisense uPAR resulted in downregulation of uPAR at both the mRNA and protein levels. In this s tudy, we used SNB19 to determine how the presence or absence of uPAR p romotes cell spreading and associated changes in cell morphology. Micr oscopic analysis of cell spreading revealed that antisense uPAR-transf ected cells were larger, remained round, and did not spread efficientl y over extracellular matrix substrate type IV collagen and fibronectin , unlike parental SNB19 cells, which were smaller and spindle shaped. Biochemical studies showed that antisense uPAR-transfected cells, in a ddition to not spreading, exhibited increased expression of alpha 3 be ta 1 integrin but not alpha 5 beta 1 integrin. However, we could not f ind a change in the expression of extracellular matrix components or a ltered growth rate in these cells. Furthermore, despite the increased alpha 3 beta 1 integrin expression, antisense uPAR-transfected cells f ailed to form an organized actin cytoskeleton when plated on type IV c ollagen or fibronectin, unlike parental SNB19 cells, which displayed a n organized cytoskeleton. These findings show that the absence of uPAR in human glioma cells leads to morphological changes associated with decreased spreading and a disorganized cytoskeleton resulting in alter ed cell morphology, suggesting that coordinated expression of uPAR and integrin may be involved in spreading of antisense uPAR-transfected g lioma cells. (C) 1997 Wiley-Liss, Inc.