Figure 2.

Quantitation of targeting of HRP-P-selectin chimeras to early endosomes. PC12 cells expressing the chimera indicated were labeled with ¹²⁵I-Trn, treated with ascorbate to inhibit HRP activity present on the plasma membrane, homogenized, and fractionated using 1–16% Ficoll velocity gradients followed by 3–16% Ficoll velocity gradients to isolate early endosomes. After fractionation, targeting to early endosomes was measured by calculating a targeting index (EE-TI) for each chimera as the amount of HRP activity within the peak of early endosomes normalized both by the expression level and by ¹²⁵I-Trn recovery. Each bar represents the mean ± SE of three independent experiments.