Transferrin receptor recycling in the absence of perinuclear recycling endosomes.
In mammalian cells, internalized receptors such as transferrin (Tfn) receptor are presumed to pass sequentially through early endosomes (EEs) and perinuclear recycling endosomes (REs) before returning to the plasma membrane. Whether passage through RE is obligatory, however, remains unclear. Kinetic analysis of endocytosis in CHO cells suggested that the majority of internalized Tfn bypassed REs returning to the surface from EEs. To determine directly if REs are dispensable for recycling, we studied Tfn recycling in cytoplasts microsurgically created to contain peripheral EEs but to exclude perinuclear REs. The cytoplasts actively internalized and recycled Tfn. Surprisingly, they also exhibited spatially and temporally distinct endosome populations. The first appeared to correspond to EEs, labeling initially with Tfn, being positive for early endosomal antigen 1 (EEA-1) and containing only small amounts of Rab11, an RE marker. The second was EEA-1 negative and with time recruited Rab11, suggesting that cytoplasts assembled functional REs. These results suggest that although perinuclear REs are not essential components of the Tfn recycling pathway, they are dynamic structures which preexist in the peripheral cytoplasm or can be regenerated from EE- and cytosol-derived components such as Rab11.
Sheff
David
D
Department of Cell Biology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, CT 06520.
Pelletier
Laurence
L
O'Connell
Christopher B
CB
Warren
Graham
G
Mellman
Ira
I
D000818:Animals; D016466:CHO Cells; D002451:Cell Compartmentation / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D006224:Cricetinae; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006801:Humans; D007150:Immunohistochemistry; D008164:Luminescent Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D021381:Protein Transport / Q000502:physiology*; D011990:Receptors, Transferrin / Q000378:metabolism*; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D011990:Receptors, Transferrin; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C093846:early endosome antigen 1