Figure 1.

Molecular events in lysosome biogenesis. Maturation; this model of lysosome biogenesis describes the formation of EVs (endocytic vesicles) from the plasma membrane and their progressive maturation to late endosomes and subsequently to lysosomes. The cargo targeted for recycling is carried by the TGN derived RVs (recycling vesicles), whereas cargo required for lysosomal degradation is transported by the cargo vesicle through late endosomes. Vesicular transport; requires ECV/MVBs (endosomal carrier vesicle/multi-vesicular bodies) carrying ILVs (intraluminal vesicles), which mobilize cargo from early-to-late endosomes and then to lysosomes or mobilize cargo directly from the matured late endosomes to lysosomes. Kiss-and-Run; describes contact site formation between lysosomes and late endosomes (“kiss”) followed the by cargo transfer and ensuing dissociation (“run”) of late endosomes from lysosomes. Fusion and fission; events involve heterotypic fusion of late endosome-lysosome to form a hybrid organelle and subsequently lysosome reformation.