A, Rb is not required for ligand-induced adhesion of Jurkat adhesion to high- density fibronectin (FN). Jurkat cells stably transfected with DN Rb or control vector were allowed to adhere to low- or high-density fibronectin with or without PDBu stimulation. B, Lysates of Jurkat cells transfected with DN RB or control were blotted with Ab to total Rb (top), phospho-specific Rb (middle), or actin as a loading control (bottom). C, Jurkat cells were transiently transfected with Rb siRNA or control construct. After 48 h, cells were allowed to adhere to low- or high-density fibronectin with or without PDBu stimulation. D, Concurrent Jurkat cell transfectants were lysed, and equal amounts of protein were separated by SDS-PAGE and then blotted with Ab to Rb (top) or tubulin as a loading control (bottom). E, Microtubules but not actin cytoskeleton are involved in ligand-induced adhesion. Jurkat cells were pretreated with nocodazole (20 µM), jasplakinolide (50 ng/ml), or cytochalsin D (1 µM) for 20 min, then were allowed to adhere to the EC matrix. Data are the means of triplicate wells ± SD.