The Small GTPase Rab4 Controls an Early Endocytic Sorting Event
Small GTP binding proteins of the rab family have been implicated in the control of vesicular traffic in eukaryotes. It is thought that rab proteins ensure the specificity or directionality of a vesicle budding or fusion event by coupling the completion of the reaction to the hydrolysis of bound GTP (Bourne, 1988). Rab4 and rab5, two distinct rab proteins, have now been localized to early endosomes (Chavrier et al., 1990; van der Sluijs et al., 1991). Although the functions of the endosome-associated rabs are not clear, in vitro evidence indicates that rab5 is involved in lateral fusion between early endosomes (Gorvel et al., 1991). Although an activity for rab4 has yet to be established, it seems likely that it will play a role in the pathway of receptor recycling since it co-localizes with the transferrin receptor (Tfn-R) (van der Sluijs et al., 1991).
KeywordsTransferrin Receptor Early Endosome Semliki Forest Virus Lateral Fusion Endocytic Compartment
Unable to display preview. Download preview PDF.
- Gorvel, J P, Chavrier, P,: erial, M, and Gruenberg, (1991) rab5 controls early endosome fusion in vitro. Cell 64, 915 925.Google Scholar
- Klausner, R D, van Rensv oude, J, Kempf, C, Rao, (, Bateman, J L, and Robbins, A R (1984) Failure to release iro i from transferrin in a CHO cell mutant pleiotropically defective in endocytosis. J Cell Biol 8, 1098–1101.Google Scholar
- Schmid, S L, Fuchs, R, t“iale, P, and Mellman, I (1988) Two distinct subpopulations of endosomes involved in me nbrane recycling and transport to lysosomes. Cell 52, 73–83.Google Scholar
- van der Sluijs, P, Hull, M. Webster, P, Goud, B, and Mellman, I (1992) The small GTP binding protein rab4 contrc s an early sorting event on the endocytic pathway. Cell in pressGoogle Scholar
- van der Sluijs, P, Hull, M, Male, P, Goud, B, and Mellman, I (1992a) Reversible phosphorylation-dephosptiorylation determines the localization of rab4 during the cell cycle. EMBO J in press.Google Scholar