fig5

Figure 5. Sorting of RSP proteins into DCV by retention and constitutive-like secretion. RSP proteins can be packaged into DCVs by a “sorting-by-retention” mechanism: C-terminal disulfide bond is necessary for proTRH to remain in RSP vesicles (A); Non-RSP proteins in immature DCVs are removed by constitutive-like secretory pathways. AP-1 binds to the cytoplasmic tails of furin and M6PR and removes furin and M6PR from immature DCV via clathrin-mediated constitutive-like secretion (B). Golgi-localized, γ-ear containing ADP-ribosylation factor binding (GGA) mediates the removal of VAMP4 from immature DCVs (B); APS1 increases the activity of H-ATPase on DCVs to facilitate vesicle acidification. Rbcn3 promotes the translocation of CAPS1 to DCVs from the cytoplasm (C). proTRH: prothyrotropin-releasing hormone; M6PR: mannose-6-phosphate receptor; Rbcn3: rabconnectin 3; DCV: dense core vesicles; RSP: regulated secretory pathway.