Figure 2.

Vesicular transport along the lysosomal pathway. Pathway I, transport from the plasma membrane (PM) to “sorting endosomes.” The latter is experimentally defined by the use of a 19°C temperature block. Pathway II, “recycling” from sorting endosomes back to the plasma membrane. Pathway III, transport from sorting endosomes to lysosomes, was studied by measuring the concentration-dependent spectral changes in fluorescence as a BODIPY-lipid accumulated in the lysosomes. Pathway IV, alternative pathways for lipid transport to the Golgi complex. TGN, trans-Golgi network.