Figure 2.

Vacuolar sorting receptor (VSR)-mediated cargo trafficking from the endoplasmic reticulum (ER) to the trans-Golgi network (TGN): Model II. After targeting of nascent vacuolar proteins to the ER, the folded vacuolar proteins bind to VSRs in the ER. Ca²⁺ plays a critical role in this binding. VSR-cargo complexes are transported to the cis-Golgi via COPII vesicles. The complexes are maintained until they reach the TGN, where the cargoes are released from the VSR due to the low concentrations of Ca²⁺. VSRs are selectively recycled back to the ER by retromer. Vacuolar cargo-enriched domains of the TGN mature into the prevacuolar compartment (PVC). The endosomal sorting complexes required for transport (ESCRT) machinery might be involved in this maturation step. m, process occurring through maturation.