Mutation of YY239/240 or Y317 of p52Shc does not affect ligand-dependent CXCR4 internalization. Flow cytometric analysis of surface CXCR4 on Jurkat T cell transfected with empty vector or stably expressing HA-tagged p52Shc or the Shc1F/Shc2F mutants, or JSL1 cells, after treatment for the indicated times with SDF-1α at 37°C. The results are plotted as percentage CXCR4 internalization (n ≥ 3). Error bars indicate SD.