The pre-early endosome sorting is independent of pH, but depends on microtubules and endocytic adaptor protein. (A) The effect of ammonium chloride on the balance between the dynamic (maturation time < 100 s) and static (maturation time > 100 s) endosome populations. (B) The effect of nocodazole (30 min treatment) on the balance between the two populations. In (A) and (B), colored histograms are for all endosomes, Tfn-receiving, LDL-receiving, and virus-receiving endosomes in drug-treated cells; shaded histograms are for those in untreated cells. (C) The effect of AP-2 knockdown on the balance between the two populations.