Distinct membrane domains on endosomes in the recycling pathway visualized by multicolor imaging of Rab4, Rab5, and Rab11.
Two endosome populations involved in recycling of membranes and receptors to the plasma membrane have been described, the early and the recycling endosome. However, this distinction is mainly based on the flow of cargo molecules and the spatial distribution of these membranes within the cell. To get insights into the membrane organization of the recycling pathway, we have studied Rab4, Rab5, and Rab11, three regulatory components of the transport machinery. Following transferrin as cargo molecule and GFP-tagged Rab proteins we could show that cargo moves through distinct domains on endosomes. These domains are occupied by different Rab proteins, revealing compartmentalization within the same continuous membrane. Endosomes are comprised of multiple combinations of Rab4, Rab5, and Rab11 domains that are dynamic but do not significantly intermix over time. Three major populations were observed: one that contains only Rab5, a second with Rab4 and Rab5, and a third containing Rab4 and Rab11. These membrane domains display differential pharmacological sensitivity, reflecting their biochemical and functional diversity. We propose that endosomes are organized as a mosaic of different Rab domains created through the recruitment of specific effector proteins, which cooperatively act to generate a restricted environment on the membrane.
Sönnichsen
B
B
Max Planck Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany. sonnichs@embl-heidelberg.de
De Renzis
S
S
Nielsen
E
E
Rietdorf
J
J
Zerial
M
M
D000730:Androstadienes / Q000494:pharmacology; D001692:Biological Transport; D020126:Brefeldin A / Q000494:pharmacology; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000502:physiology / Q000648:ultrastructure*; D049452:Green Fluorescent Proteins; D006801:Humans; D007425:Intracellular Membranes / Q000502:physiology / Q000648:ultrastructure*; D008164:Luminescent Proteins / Q000235:genetics / Q000302:isolation & purification; D008561:Membrane Fusion; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification; D014168:Transferrin / Q000378:metabolism; D014407:Tumor Cells, Cultured; D000077191:Wortmannin; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000302:isolation & purification*; D020695:rab4 GTP-Binding Proteins / Q000235:genetics / Q000302:isolation & purification; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000302:isolation & purification; D000099193:rab11 GTP-Binding Proteins
D000730:Androstadienes; D020126:Brefeldin A; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D014168:Transferrin; D000077191:Wortmannin; D020691:rab GTP-Binding Proteins; D020695:rab4 GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins