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Endosome maturation: 
the endocytic pathway from the plasma 
membrane to lysosomes. Near the cell 
periphery, endocytic vesicles fuse with 
an early endosome, which is the primary 
sorting station. Tubular portions of the early 
endosome bud off vesicles that recycle 
endocytosed cargo back to the plasma 
membrane—either directly or indirectly 
via recycling endosomes. Recycling 
endosomes can store proteins until they are 
needed. Conversion of early endosomes to 
late endosomes is accompanied by loss of 
the tubular projections. Membrane proteins 
destined for degradation are internalized 
in intralumenal vesicles. The developing 
late endosome, or multivesicular body, 
moves on microtubules to the cell interior. 
Fully matured late endosomes no longer 
send vesicles to the plasma membrane, 
and they fuse with one another and with 
endolysosomes and lysosomes to degrade 
their contents. Each stage of endosome 
maturation is connected to the TGN via 
transport vesicles, providing a continual 
supply of newly synthesized lysosomal 
proteins.