Wood S A, Brown W J
Section of Biochemistry Molecular and Cell Biology, Cornell University, Ithaca, New York 14850.
J Cell Biol. 1992 Oct;119(2):273-85. doi: 10.1083/jcb.119.2.273.
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.
布雷菲德菌素A（BFA）可诱导源自反式高尔基体网络（TGN）和早期内体（EE）的膜形成广泛融合的网络。我们在此详细描述了在BFA处理的细胞中，内吞物质通过融合的TGN/EE区室不受影响地传递至溶酶体的过程。我们还证实，BFA导致了管状溶酶体的形成，尽管不同细胞类型之间管状化的动力学和程度差异很大。BFA诱导的管状溶酶体常可见形成简单的网络。管状溶酶体的形成是微管介导的且依赖能量；然而，有趣的是，维持管状溶酶体仅需要微管，并且对能量毒物不敏感。去除BFA后，管状溶酶体在一个能量依赖的过程中迅速恢复。在大多数检测的细胞类型中，广泛的TGN/EE网络是短暂的，最终在管状溶酶体形成之前的一个过程中塌陷成紧密的微管泡状膜簇。然而，在原代牛睾丸细胞中，BFA诱导的TGN/EE网络非常稳定（超过12小时）。在此期间，TGN/EE网络与管状溶酶体共存，然而，这两个区室保持完全分离。这些结果表明，BFA对内体-溶酶体系统的各个区室的形态有多种深远影响。尽管发生了这些变化，内吞运输仍可通过改变后的区室继续进行，这表明运输是通过无被小泡或对BFA不敏感的小泡进行的。
