Intracellular localization of TBLR1. 3T3 cells respond to apoptotic stimuli with increased expression of TBLR1 and with translocation of TBLR1 into the nucleus. grown in on collagen coated cover slips were used. Untreated cells in the log phase of growth are shown in panels a and d. Apoptosis was induced by either serum starvation (incubation with DMEM containing 0.2% FBS for 16 h) [panels b and e] or growth with100 ng/ml of the topoisomerase inhibitor, camptothecin (CPT) [panels d and f]. The top panels [a, b, and c] were stained for total TBLR1 with anti TBLR1 [117-125] while the bottom panels [d, e, and f] were stained with anti TBLR1β. The images were obtained using a Leitz Orthlux microscope at an original magnification of 600 × with a Nikon 60X phase fluorescence objective (NA 1.4) and captured with a Nikon digital camera.