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endocytic pathway compartments

In biology, an endosome is a membrane-bounded compartment inside eukaryotic cells. It is a compartment of the endocytic membrane transport pathway from the plasma membrane to the lysosome. Molecules internalized from the plasma membrane can follow this pathway all the way to lysosomes for degradation, or they can be recycled back to the plasma membrane. Molecules are also transported to endosomes from the Golgi and either continue to lysosomes or recycle back to the Golgi. Furthermore, molecules can be directed into vesicles that bud from the perimeter membrane into the endosome lumen. Therefore, endosomes represent a major sorting compartment of the endomembrane system in cells.[1] In HeLa cells, endosomes are approximately 500 nm in diameter when fully mature.[2]


Endosomes provide an environment for material to be sorted before it reaches the degradative lysosome.[1] For example, LDL is taken into the cell by binding to the LDL receptor at the cell surface. On reaching early endosomes, the LDL dissociates from the receptor, and the receptor can be recycled to the cell surface. The LDL remains in the endosome and is delivered to lysosomes for processing. LDL dissociates because of the slightly acidified environment of the early endosome, generated by a vacuolar membrane proton pump V-ATPase. On the other hand, EGF and the EGF receptor have a pH-resistant bond that persists until it is delivered to lysosomes for their degradation. The mannose 6-phosphate receptor carries ligands from the Golgi destined for the lysosome by a similar mechanism.


Endosomes comprise three different compartments: early endosomes, late endosomes, and recycling endosomes.[1] They are distinguished by the time it takes for endocytosed material to reach them, and by markers such as rabs.[3] They also have different morphology. Once endocytic vesicles have uncoated, they fuse with early endosomes. Early endosomes then mature into late endosomes before fusing with lysosomes.[4][5]

Early endosomes mature in several ways to form late endosomes. They become increasingly acidic mainly through the activity of the V-ATPase.[6] Many molecules that are recycled are removed by concentration in the tubular regions of early endosomes. Loss of these tubules to recycling pathways means that late endosomes mostly lack tubules. They also increase in size due to the homotypic fusion of early endosomes into larger vesicles.[7] Molecules are also sorted into smaller vesicles that bud from the perimeter membrane into the endosome lumen, forming lumenal vesicles; this leads to the multivesicular appearance of late endosomes and so they are also known as multivesicular bodies (MVBs). Removal of recycling molecules such as transferrin receptors and mannose 6-phosphate receptors continues during this period, probably via budding of vesicles out of endosomes.[4] Finally, the endosomes lose RAB5A and acquire RAB7A, making them competent for fusion with lysosomes.[7]


Some material recycles to the plasma membrane directly from early endosomes,[9] but most traffics via recycling endosomes.

  • Late endosomes, also known as MVBs, are mainly spherical, lack tubules, and contain many close-packed lumenal vesicles. Markers include RAB7, RAB9, and mannose 6-phosphate receptors.[10]


Phagosomes, macropinosomes and autophagosomes[12] mature in a manner similar to endosomes, and may require fusion with normal endosomes for their maturation. Some intracellular pathogens subvert this process, for example, by preventing RAB7 acquisition.[13]



animal cell endocytic pathway


It should be noted that there is no consensus as to the exact nature of these pathways, and the sequential route taken by any given cargo in any given situation will tend to be a matter of debate.

Golgi to/from endosomes[edit]




Late endosomes to lysosomes[edit]



  1. ^ a b c Mellman I (1996). "Endocytosis and molecular sorting". Annual Review of Cell and Developmental Biology 12: 575–625. doi:10.1146/annurev.cellbio.12.1.575. PMID 8970738. 
  2. ^ Ganley et al. (December 2004). "Rab9 GTPase Regulates Late Endosome Size and Requires Effector Interaction for Its Stability". Molecular Biology of the Cell 15 (12): 5420–5430. doi:10.1091/mbc.E04-08-0747. PMC 532021. PMID 15456905. 
  3. ^ Stenmark, H. (Aug 2009). "Rab GTPases as coordinators of vesicle traffic". Nat Rev Mol Cell Biol 10 (8): 513–25. doi:10.1038/nrm2728. PMID 19603039. 
  4. ^ a b Futter, CE.; Pearse, A.; Hewlett, LJ.; Hopkins, CR. (Mar 1996). "Multivesicular endosomes containing internalized EGF-EGF receptor complexes mature and then fuse directly with lysosomes". J Cell Biol 132 (6): 1011–23. doi:10.1083/jcb.132.6.1011. PMC 2120766. PMID 8601581. 
  5. ^ Luzio JP, Rous BA, Bright NA, Pryor PR, Mullock BM, Piper RC. (2000). "Lysosome-endosome fusion and lysosome biogenesis". Journal of Cell Science 113: 1515–1524. PMID 10751143. 
  6. ^ Lafourcade, C.; Sobo, K.; Kieffer-Jaquinod, S.; Garin, J.; van der Goot, FG. (2008). Joly, Etienne, ed. "Regulation of the V-ATPase along the endocytic pathway occurs through reversible subunit association and membrane localization". PLoS ONE 3 (7): e2758. doi:10.1371/journal.pone.0002758. PMC 2447177. PMID 18648502. 
  7. ^ a b Rink, J.; Ghigo, E.; Kalaidzidis, Y.; Zerial, M. (Sep 2005). "Rab conversion as a mechanism of progression from early to late endosomes". Cell 122 (5): 735–49. doi:10.1016/j.cell.2005.06.043. PMID 16143105. 
  8. ^ Mullock, BM.; Bright, NA.; Fearon, CW.; Gray, SR.; Luzio, JP. (Feb 1998). "Fusion of lysosomes with late endosomes produces a hybrid organelle of intermediate density and is NSF dependent". J Cell Biol 140 (3): 591–601. doi:10.1083/jcb.140.3.591. PMC 2140175. PMID 9456319. 
  9. ^ Hopkins, CR, I.S. Trowbridge, IS. (1983). "Internalization and processing of transferrin and the transferrin receptor in human carcinoma A431 cells". Journal of Cell Biology 97 (2): 508–21. doi:10.1083/jcb.97.2.508. PMC 2112524. PMID 6309862. 
  10. ^ Russell, MR.; Nickerson, DP.; Odorizzi, G. (Aug 2006). "Molecular mechanisms of late endosome morphology, identity and sorting". Curr Opin Cell Biol 18 (4): 422–8. doi:10.1016/j.ceb.2006.06.002. PMID 16781134. 
  11. ^ Ullrich, O.; Reinsch, S.; Urbé, S.; Zerial, M.; Parton, RG. (Nov 1996). "Rab11 regulates recycling through the pericentriolar recycling endosome". J Cell Biol 135 (4): 913–24. doi:10.1083/jcb.135.4.913. PMC 2133374. PMID 8922376. 
  12. ^ Fader, CM.; Colombo, MI. (Jan 2009). "Autophagy and multivesicular bodies: two closely related partners". Cell Death Differ 16 (1): 70–8. doi:10.1038/cdd.2008.168. PMID 19008921. 
  13. ^ Körner, U.; Fuss, V.; Steigerwald, J.; Moll, H. (Feb 2006). "Biogenesis of Leishmania major-harboring vacuoles in murine dendritic cells". Infect Immun 74 (2): 1305–12. doi:10.1128/IAI.74.2.1305-1312.2006. PMC 1360340. PMID 16428780. 
  14. ^ Ghosh, P.; Kornfeld, S. (Jul 2004). "The GGA proteins: key players in protein sorting at the trans-Golgi network". Eur J Cell Biol 83 (6): 257–62. doi:10.1078/0171-9335-00374. PMID 15511083. 
  15. ^ Grant, BD.; Donaldson, JG. (Sep 2009). "Pathways and mechanisms of endocytic recycling". Nat Rev Mol Cell Biol 10 (9): 597–608. doi:10.1038/nrm2755. PMC 3038567. PMID 19696797. 
  16. ^ Futter, CE.; Collinson, LM.; Backer, JM.; Hopkins, CR. (Dec 2001). "Human VPS34 is required for internal vesicle formation within multivesicular endosomes". J Cell Biol 155 (7): 1251–64. doi:10.1083/jcb.200108152. PMC 2199316. PMID 11756475. 
  17. ^ Felder, S.; Miller, K.; Moehren, G.; Ullrich, A.; Schlessinger, J.; Hopkins, CR. (May 1990). "Kinase activity controls the sorting of the epidermal growth factor receptor within the multivesicular body". Cell 61 (4): 623–34. doi:10.1016/0092-8674(90)90474-S. PMID 2344614. 
  18. ^ Dautry-Varsat, A. (Mar 1986). "Receptor-mediated endocytosis: the intracellular journey of transferrin and its receptor". Biochimie 68 (3): 375–81. doi:10.1016/S0300-9084(86)80004-9. PMID 2874839. 
  19. ^ Hicke, L.; Dunn, R. (2003). "Regulation of membrane protein transport by ubiquitin and ubiquitin-binding proteins". Annu Rev Cell Dev Biol 19: 141–72. doi:10.1146/annurev.cellbio.19.110701.154617. PMID 14570567. 
  20. ^ Hurley, JH. (Feb 2008). "ESCRT complexes and the biogenesis of multivesicular bodies". Curr Opin Cell Biol 20 (1): 4–11. doi:10.1016/j.ceb.2007.12.002. PMC 2282067. PMID 18222686. 
  • Alberts, Bruce; et al. (2004). Essential Cell Biology (2nd ed.). New York, NY: Garland Science. ISBN 0-8153-3480-X. 

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