Image: Endocytic pathway of animal cells showing EGF receptors, transferrin receptors and mannose-6-phosphate receptors

Description: The endocytic pathway in animal cells. Endocytosed molecules from the cell surface are internalized to early endosomes. These then develop into late endosomes/multivesicular bodies (MVBs) by maturation; recycling molecules are removed, pH is lowered, lumenal vesicles form, and RAB5 is replaced with RAB7, making them competent for fusion with lysosomes. Fusion creates a hybrid, from which a lysosome is reformed. Molecules recycling to the plasma membrane can traffic via recycling endosomes (not shown). Molecules are also transported to/from the Golgi. More complicated pathways exist in specialized cells. Transferrin and its receptor cycle between the plasma membrane and (mainly) early endosomes. Transferrin releases its iron in the acidic endosome. EGF receptors that are activated by binding EGF, are downregulated by degradation in lysosomes. EGF binding stimulates ubiquitination of EGFRs and this targets them to the lysosome lumen, via lumenal vesicles. Mannose-6-phosphate receptors cycle between the Golgi and endosomes, releasing their cargo due to the low pH of the endosomes.
Title: Endocytic pathway of animal cells showing EGF receptors, transferrin receptors and mannose-6-phosphate receptors
Credit: Own work
Author: Matthew R G Russell
Usage Terms: Creative Commons Attribution-Share Alike 3.0
License: CC BY-SA 3.0
License Link: https://creativecommons.org/licenses/by-sa/3.0
Attribution Required?: Yes