Sorting of EGF and transferrin at the plasma membrane and by cargo-specific signaling to EEA1-enriched endosomes.
The biological function of receptors is determined by their appropriate trafficking through the endosomal pathway. Following internalization, the transferrin (Tf) receptor quantitatively recycles to the plasma membrane, whereas the epidermal growth factor (EGF) receptor undergoes degradation. To determine how Tf and EGF engage these two different pathways we imaged their binding and early endocytic pathway in live cells using total internal reflection fluorescence microscopy (TIRF-M). We find that EGF and Tf bind to distinct plasma membrane regions and are incorporated into different endocytic vesicles. After internalization, both EGF-enriched and Tf-enriched vesicles interact with endosomes containing early endosome antigen 1 (EEA1). EGF is incorporated and retained in these endosomes, while Tf-containing vesicles rapidly dissociate and move to a juxtanuclear compartment. Endocytic vesicles carrying EGF recruit more Rab5 GTPase than those carrying Tf, which, by strengthening their association with EEA1-enriched endosomes, may provide a mechanism for the observed cargo-specific sorting. These results reveal pre-endocytic sorting of Tf and EGF, a specialized role for EEA1-enriched endosomes in EGF trafficking, and a potential mechanism for cargo-specified sorting of endocytic vesicles by these endosomes.
Leonard
Deborah
D
Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
Hayakawa
Akira
A
Lawe
Deirdre
D
Lambright
David
D
Bellve
Karl D
KD
Standley
Clive
C
Lifshitz
Lawrence M
LM
Fogarty
Kevin E
KE
Corvera
Silvia
S
D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism*; D002522:Chlorocebus aethiops; D011992:Endosomes / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D014168:Transferrin / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*
D014168:Transferrin; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; D004815:Epidermal Growth Factor