The morphology but not the function of endosomes and lysosomes is altered by brefeldin A.
Brefeldin A (BFA) induces the formation of an extensively fused network of membranes derived from the trans-Golgi network (TGN) and early endosomes (EE). We describe in detail here the unaffected passage of endocytosed material through the fused TGN/EE compartments to lysosomes in BFA-treated cells. We also confirmed that BFA caused the formation of tubular lysosomes, although the kinetics and extent of tubulation varied greatly between different cell types. The BFA-induced tubular lysosomes were often seen to form simple networks. Formation of tubular lysosomes was microtubule-mediated and energy-dependent; interestingly, however, maintenance of the tubulated lysosomes only required microtubules and was insensitive to energy poisons. Upon removal of BFA, the tubular lysosomes rapidly recovered in an energy-dependent process. In most cell types examined, the extensive TGN/EE network is ephemeral, eventually collapsing into a compact cluster of tubulo-vesicular membranes in a process that precedes the formation of tubular lysosomes. However, in primary bovine testicular cells, the BFA-induced TGN/EE network was remarkably stable (for > 12 h). During this time, the TGN/EE network coexisted with tubular lysosomes, however, the two compartments remained completely separate. These results show that BFA has multiple, profound effects on the morphology of various compartments of the endosome-lysosome system. In spite of these changes, endocytic traffic can continue through the altered compartments suggesting that transport occurs through noncoated vesicles or through vesicles that are insensitive to BFA.
Wood
S A
SA
Section of Biochemistry Molecular and Cell Biology, Cornell University, Ithaca, New York 14850.
Brown
W J
WJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D015415:Biomarkers; D020126:Brefeldin A; D002402:Cathepsin D / Q000302:isolation & purification; D002451:Cell Compartmentation; D002478:Cells, Cultured; D003517:Cyclopentanes / Q000494:pharmacology*; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D004734:Energy Metabolism; D006801:Humans; D007150:Immunohistochemistry; D007700:Kinetics; D008247:Lysosomes / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D008870:Microtubules / Q000502:physiology; D015388:Organelles / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D013347:Subcellular Fractions
D000900:Anti-Bacterial Agents; D015415:Biomarkers; D003517:Cyclopentanes; D020126:Brefeldin A; D000255:Adenosine Triphosphate; D002402:Cathepsin D