concanamycin-b and Lymphoma--B-Cell

We have previously identified an intracellular compartment involved in the association between processed lysozyme and IAk major histocompatibility complex class II molecules (called the lysozyme-loading compartment (LLC)). Here, we show that the LLC polypeptide composition analyzed by two-dimensional gel electrophoresis shares similarities with that of early endosomes, but not with that of late endosomes. The transferrin receptor, a well known marker for both early and recycling endosomes, colocalizes with IAk molecules in LLC. Moreover, both transferrin and fluid-phase markers have access to LLC after 15 min of internalization. In the presence of concanamycin B, SDS-stable dimer formation and transport of class II molecules out of LLC are impaired. In contrast, nocodazole treatment has no effect. These results suggest that LLC is a specialized compartment of the recycling pathway involved in lysozyme loading and in the targeting of lysozyme-major histocompatibility class II complexes toward the cell surface.

Topics: Animals; Anti-Bacterial Agents; B-Lymphocytes; Cell Fractionation; Dimerization; Electrophoresis, Gel, Two-Dimensional; Endocytosis; Endosomes; Histocompatibility Antigens Class II; Horseradish Peroxidase; Kinetics; Lymphoma, B-Cell; Macrolides; Mice; Microscopy, Electron; Muramidase; Nocodazole; Tumor Cells, Cultured