MTOC repositioning is biphasic. (A) Time-lapse montage showing MTOC repositioning in a representative Jurkat cell immediately after APC conjugation (merged image of the GFP-Cen-2–tagged MTOC and the RFP-Farnesyl–tagged synaptic membrane). The yellow and white arrowheads mark the transition between the polarization and docking phases and the docked MTOC, respectively. Distance from the IS is indicated on the right. See also Video 2. (B) Transmitted image of a Jurkat–Raji conjugate (left) and a maximum projection over time of the GFP-Cen-2 signal in the Jurkat (right). The yellow arrowhead marks the transition point between the two kinetic phases. (C) Cartoon depicting the two apparent kinetic phases. (D) Compilation of MTOC-repositioning events in eight additional conjugates, plotted as MTOC-to-IS distance versus time. (E) Scatter plot of the instantaneous speeds of MTOC movement as a function of MTOC-to-IS distance, obtained from the nine repositioning events presented in A and D. The red and green colors signify points grouped into the polarization and docking phases, respectively, as defined by statistical analyses (see text). (F) The average rates of MTOC movement during the polarization and docking phases. We note that the scatter plot in Fig. 3 E suggests that the MTOC slows down even more as it gets very close to the IS. Bar, 10 µm.