Rab conversion as a mechanism of progression from early to late endosomes.
The mechanisms of endosome biogenesis and maintenance are largely unknown. The small GTPases Rab 5 and Rab 7 are key determinants of early and late endosomes, organizing effector proteins into specific membrane subdomains. Whether such Rab machineries are indefinitely maintained on membranes or can disassemble in the course of cargo transport is an open question. Here, we combined novel image-analysis algorithms with fast live-cell imaging. We found that the level of Rab 5 dynamically fluctuates on individual early endosomes, linked by fusion and fission events into a network in time. Within it, degradative cargo concentrates in progressively fewer and larger endosomes that migrate from the cell periphery to the center where Rab 5 is rapidly replaced with Rab 7. The class C VPS/HOPS complex, an established GEF for Rab 7, interacts with Rab 5 and is required for Rab 5-to-Rab 7 conversion. Our results reveal unexpected dynamics of Rab domains and suggest Rab conversion as the mechanism of cargo progression between early and late endosomes.
Rink
Jochen
J
Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
Ghigo
Eric
E
Kalaidzidis
Yannis
Y
Zerial
Marino
M
D001692:Biological Transport; D045744:Cell Line, Tumor; D011992:Endosomes / Q000378:metabolism*; D005456:Fluorescent Dyes; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008077:Lipoproteins, LDL / Q000378:metabolism; D018715:Microscopy, Video; D008954:Models, Biological; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
D005456:Fluorescent Dyes; D008077:Lipoproteins, LDL; D000090802:rab7 GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins