Multivesicular endosomes containing internalized EGF-EGF receptor complexes mature and then fuse directly with lysosomes.

Abstract

Abstract. We have followed the transfer of EGF-EGF receptor (EGFR) complexes from endosomal vacuoles that contain transferrin receptors (TfR) to lysosome vacuoles identified by their content of HRP loaded as a 15-min pulse 4 h previously. We show that the HRPloaded lysosomes are lysosomal-associated membrane protein-1 (LAMP-l) positive, mannose-6-phosphate receptor (M6PR) negative, and contain active acid hydrolase. EGF-EGFR complexes are delivered to these lysosomes intact and are then rapidly degraded.Preactivating the HRP contained within the preloaded lysosomes inhibits the delivery of EGFR and degradation of EGF, and results in the accumulation of EGFR-containing multivesicular bodies (MVB). With time these accumulating MVB undergo a series of maturation changes that include the loss of TfR, the continued recruitment of EGFR, and the accumulation of internal vesicles, but they remain LAMP-1 and M6PR negative. The mature MVB are often seen to make direct contact with lysosomes containing preactivated HRP, but their perimeter membranes remain intact.Together our observations suggest that the transfer of EGF-EGFR complexes from the TfR-containing endosome compartment to the lysosomes that degrade them employs a single vacuolar intermediate, the maturing MVB, and can be achieved by a single heterotypic fusion step.

Tal, a Tsg101-specific E3 ubiquitin ligase, regulates receptor endocytosis and retrovirus budding

“…The first occurs at the plasma membrane and entails recruitment of active receptors to clathrin-coated regions of the plasma membrane. The postinternalization sorting event takes place at a late endosomal compartment, the MVB, and it involves budding of vesicles into the lumen of endosomes (Futter et al 1996). Importantly, these two sorting events differ in their topology: whereas the initial event represents an inward budding and fission process, the late outward budding engulfs portions of the cytoplasm.…”

Deubiquitylases From Genes to Organism

“…Under the influence of this machinery, the sorting endosome matures into multivesicular bodies (MVBs) with the accrual of luminal vesicles, laden with cargo molecules that bud from the limiting membrane. MVBs then deliver cargo to lysosomes by direct fusion (76).…”

Ent5p Is Required with Ent3p and Vps27p for Ubiquitin-dependent Protein Sorting into the Multivesicular Body

“…A critical membrane segregation and protein-sorting event takes place in late endosomes, regions of endosomal membranes invaginate and vesicles bud into the lumen of the organelle, giving rise to the multivesicular body (MVB; Felder et al, 1990). Mature MVB fuses with the vacuole/ lysosome releasing internal vesicles into its lumen and thereby exposing them to the activity of hydrolytic enzymes (Futter et al, 1996;Odorizzi et al, 1998). This mechanism allows a subset of endosomal membrane proteins to be sorted to the lumen of the lysosome/vacuole, whereas others are either selectively recycled back to the Golgi or to the plasma membrane, or they end up on the lysosomal/vacuolar membrane (Pelham, 2002).…”