Direct Vesicular Transport of MHC Class II Molecules from Lysosomal Structures to the Cell Surface

• Published in: The Journal of cell biology Vol. 135; no. 3; pp. 611 - 622
• Main Authors: Wubbolts, Richard, Fernandez-Borja, Mar, Oomen, Lauran, Verwoerd, Desiree, Janssen, Hans, Calafat, Jero, Tulp, Abraham, Dusseljee, Simone, Neefjes, Jacques
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 01-11-1996; The Rockefeller University Press
• Subjects: Antibodies; Antigens; Biological Transport; Brefeldin A; Cell lines; Cell Membrane - chemistry; Cell membranes; Cells; Cellular biology; Cyclopentanes - pharmacology; Endosomes; Endosomes - metabolism; Fluorescence; Green Fluorescent Proteins; HLA-DR1 Antigen - analysis; HLA-DR1 Antigen - genetics; HLA-DR1 Antigen - metabolism; Humans; Intracellular Membranes - chemistry; Luminescent Proteins - analysis; Luminescent Proteins - genetics; Lysosomes - chemistry; Lysosomes - metabolism; Melanoma; Membrane Fusion; Membranes; Microscopy, Confocal; Molecular chains; Molecular structure; Molecules; Peptides; Protein Synthesis Inhibitors - pharmacology; Recombinant Fusion Proteins - analysis; Recombinant Fusion Proteins - metabolism; Tumor Cells, Cultured
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.135.3.611

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 β chain with the Green Fluorescent Protein (GFP) coupled to its cytoplasmic tail (β-GFP) in class II-expressing Mel JuSo cells. This modification of the class II β chain does not affect assembly, intracellular distribution, and peptide loading of the MHC class II complex. Transport of the class II/β-GFP chimera was studied in living cells at 37°C. We visualize rapid movement of acidic class II/β-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.