Question

Name three possible fates for an endocytosed cargo that has reached the endosome in a

polarized epithelial cell and explain the mechanism for how that cargo vesicle finds and fuses

with the endosomal membrane.

Answer 1

The three possible fates are as follows:

1. Endocytosed cargo protein that are not specifically retrieved from early endosomes are transferred to lysosomes and degraded.

2. Retreived endocytosed cargo proteins are returned either to the membrane domain of origin (recycling) or to another domain (transcytosis).

3. If the ligand bound to the cargo protein stays bound in the acidic environment of the endosome, it will follow the same pathway as the cargo protein otherwise it will be transferred to a lysosome and degraded.

Mechanism of cargo vesicles finding and fusion: The cargo protein binds to receptors on the cell surface and in internalized in clathrin-coated vesicles.The vesicles then lose their coats and fuse with endosomes.