TRANSFERRIN RECEPTOR-CONTAINING THE SDYQRL MOTIF OF TGN38 CAUSES A REORGANIZATION OF THE RECYCLING COMPARTMENT BUT IS NOT TARGETED TO THE TGN

Citation
Ao. Johnson et al., TRANSFERRIN RECEPTOR-CONTAINING THE SDYQRL MOTIF OF TGN38 CAUSES A REORGANIZATION OF THE RECYCLING COMPARTMENT BUT IS NOT TARGETED TO THE TGN, The Journal of cell biology, 135(6), 1996, pp. 1749-1762
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cell Biology
Journal title
ISSN journal
0021-9525
Volume
135
Issue
6
Year of publication
1996
Part
2
Pages
1749 - 1762
Database
ISI
SICI code
0021-9525(1996)135:6<1749:TRTSMO>2.0.ZU;2-F
Abstract
The SDYQRL motif of the cytoplasmic domain of TGN38 is involved in tar geting TGN38 from endosomes to the TGN, To create a system for studyin g this pathway, we replaced the native transferrin receptor (TR) inter nalization motif (YTRF) with the SDYQRL TGN-targeting motif. The advan tages of using TR as a reporter molecule include the ability to monito r trafficking, in both biochemical and microscopy experiments, using t he natural ligand transferrin. When expressed in CHO cells, the SDYQRL -TR con struct accumulated in juxtanuclear tubules and vesicles that a re in the vicinity of the TGN, The SDYQRL-TR-containing structures, ho wever, do not colocalize with TGN markers (e.g., NBD ceramide), and th erefore the SDYQRL motif is not sufficient to target the TR to the TGN . The morphology of the SDYQRL-TR-containing juxtanuclear structures i s different from the recycling compartment found in cells expressing t he wild-type TR. In addition, the SDYQRL-TR-containing juxtanuclear co mpartment is more acidic than the recycling compartment in cells expre ssing the wild-type TR. The juxtanuclear compartment, however, is a bo na fide recycling compartment since SDYQRL-TR was recycled back to the cell surface at a rate comparable to the wild-type TR, and sphingomye lin and cellubrevin, both which label all compartments of the endocyti c recycling pathway, colocalize with SDYQRL-TR in the juxtanuclear str uctures. These findings demonstrate that expression of the SDYQRL-TR c onstruct alters the morphology and pH of endocytic recycling compartme nts rather than selectively affecting the intracellular trafficking pa thway of the SDYQRL-TR construct. Therefore, the SDYQRL trafficking mo tif is not simply a molecular address that targets proteins to the TGN , but it can play an active role in determining the physical character istics of endosomal compartments.