Direct vesicular transport of MHC class II molecules from lysosomal structures to the cell surface.
Newly synthesized MHC class II molecules are sorted to lysosomal structures where peptide loading can occur. Beyond this point in biosynthesis, no MHC class II molecules have been detected at locations other than the cell surface. We studied this step in intracellular transport by visualizing MHC class II molecules in living cells. For this purpose we stably expressed a modified HLA-DR1 beta chain with the Green Fluorescent Protein (GFP) coupled to its cytoplasmic tail (beta-GFP) in class II-expressing Mel JuSo cells. This modification of the class II beta chain does not affect assembly, intracellular distribution, and peptide loading of the MHC class II complex. Transport of the class II/ beta-GFP chimera was studied in living cells at 37 degrees C. We visualize rapid movement of acidic class II/beta-GFP containing vesicles from lysosomal compartments to the plasma membrane and show that fusion of these vesicles with the plasma membrane occurs. Furthermore, we show that this transport route does not intersect the earlier endosomal pathway.
Department of Cellular Biochemistry, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
R
R
Wubbolts
M
M
Fernandez-Borja
L
L
Oomen
D
D
Verwoerd
H
H
Janssen
J
J
Calafat
A
A
Tulp
S
S
Dusseljee
J
J
Neefjes
D001692:Biological Transport; D020126:Brefeldin A; D002462:Cell Membrane / Q000737:chemistry*; D003517:Cyclopentanes / Q000494:pharmacology; D011992:Endosomes / Q000378:metabolism; D049452:Green Fluorescent Proteins; D015798:HLA-DR1 Antigen / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000737:chemistry; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D008247:Lysosomes / Q000737:chemistry* / Q000378:metabolism; D008545:Melanoma; D008561:Membrane Fusion; D018613:Microscopy, Confocal; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000378:metabolism; D014407:Tumor Cells, Cultured
D003517:Cyclopentanes; D015798:HLA-DR1 Antigen; D008164:Luminescent Proteins; D011500:Protein Synthesis Inhibitors; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D020126:Brefeldin A