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Rab4 affects both recycling and degradative endosomal trafficking
Author(s) -
McCaffrey Mary W.,
Bielli Anna,
Cantalupo Giuseppina,
Mora Silvia,
Roberti Vera,
Santillo Mariarosaria,
Drummond Frances,
Bucci Cecilia
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02359-6
Subject(s) - endosome , microbiology and biotechnology , endocytic cycle , internalization , endocytosis , transferrin receptor , mutant , biology , compartment (ship) , rab , transport protein , intracellular , transferrin , receptor , gtpase , biochemistry , oceanography , geology , gene
The small GTPases Rab4, Rab5 and Rab7 are endosomal proteins which play important roles in the regulation of various stages of endosomal trafficking. Rab4 and Rab5 have both been localized to early endosomes and have been shown to control recycling and endosomal fusion, respectively. Rab7, a marker of the late endosomal compartment, is involved in the regulation of the late endocytic pathway. Here, we compare the role of Rab4, Rab5 and Rab7 in early and late endosomal trafficking in HeLa cells monitoring ligand uptake, recycling and degradation. Expression of the Rab4 dominant negative mutant (Rab4AS22N) leads to a significant reduction in both recycling and degradation while, as expected, Rab7 mutants exclusively affect epidermal growth factor (EGF) and low density lipoprotein degradation. As also expected, expression of the dominant negative Rab5 mutant perturbs internalization kinetics and affects both recycling and degradation. Expression of Rab4WT and dominant positive mutant (Rab4AQ67L) changes dramatically the morphology of the transferrin compartment leading to the formation of membrane tubules. These transferrin positive tubules display swellings (varicosities) some of which are positive for early endosomal antigen‐1 and contain EGF. We propose that the Rab4GTPase is important for the function of the early sorting endosomal compartment, affecting trafficking along both recycling and degradative pathways.