The recycling pathway of protein ERGIC-53 and dynamics of the ER-Golgi intermediate compartment.
To establish recycling routes in the early secretory pathway we have studied the recycling of the ER-Golgi intermediate compartment (ERGIC) marker ERGIC-53 in HepG2 cells. Immunofluorescence microscopy showed progressive concentration of ERGIC-53 in the Golgi area at 15 degreesC. Upon rewarming to 37 degreesC ERGIC-53 redistributed into the cell periphery often via tubular processes that largely excluded anterograde transported albumin. Immunogold labeling of cells cultured at 37 degreesC revealed ERGIC-53 predominantly in characteristic beta-COP-positive tubulo-vesicular clusters both near the Golgi apparatus and in the cell periphery. Concentration of ERGIC-53 at 15 degreesC resulted from both accumulation of ERGIC-53 in the ERGIC and movement of ERGIC membranes closer to the Golgi apparatus. Upon rewarming to 37 degreesC the labeling of ERGIC-53 in the ERGIC rapidly returned to normal levels whereas ERGIC-53's labeling in the cis-Golgi was unchanged. Temperature manipulations had no effect on the average number of ERGIC-53 clusters. Density gradient centrifugation indicated that the surplus ERGIC-53 accumulating in the ERGIC at 15 degreesC was rapidly transported to the ER upon rewarming. These results suggest that the ERGIC is a dynamic membrane system composed of a constant average number of clusters and that the major recycling pathway of ERGIC-53 bypasses the Golgi apparatus.
Klumperman
J
J
Department of Cell Biology, School of Medicine, Utrecht University, The Netherlands.
Schweizer
A
A
Clausen
H
H
Tang
B L
BL
Hong
W
W
Oorschot
V
V
Hauri
H P
HP
D000418:Albumins / Q000032:analysis / Q000096:biosynthesis; D001692:Biological Transport / Q000502:physiology; D006528:Carcinoma, Hepatocellular; D002451:Cell Compartmentation / Q000502:physiology*; D020756:Coatomer Protein; D006056:Golgi Apparatus / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry; D013696:Temperature; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure
D000418:Albumins; D020756:Coatomer Protein; C084004:LMAN1 protein, human; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins