Urokinase Anchors uPAR to the Actin Cytoskeleton Audrey

RESULTS. uPA/uPAR was immunodetected in large (200 m) aggregates devoid of detectable F-actin. However, when uPA was added to corneal fibroblasts before fixation, a dynamic association between uPAR and the actin cytoskeleton was revealed: the uPA/uPAR complex was immunodetected throughout the surface of the plasma membrane in the form of dispersed small aggregates (0.05 m). Association of uPAR with actin stress fibers was visualized when FITC-labeled uPA was added to the cells. This codistribution of uPA/uPAR and actin was not detected when the cells were pretreated with the actin-depolymerizing drug, cytochalasin D. uPAR was found also in focal adhesions, the termination points of F-actin, where it colocalized with the integrin v 3 in cells migrating into a scrape wound. Coimmunoprecipitation experiments confirmed the physical association of uPAR with v 3 in fibroblasts.

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