Tilney L G, Connelly P S, Portnoy D A
Department of Biology, University of Pennsylvania, Philadelphia 19104-6018.
J Cell Biol. 1990 Dec;111(6 Pt 2):2979-88. doi: 10.1083/jcb.111.6.2979.
Shortly after Listeria is phagocytosed by a macrophage, it dissolves the phagosomal membrane and enters the cytoplasm. 1 h later, actin filaments coat the Listeria and then become rearranged to form a tail with which the Listeria moves to the macrophage surface as a prelude to spreading. If infected macrophages are treated with cytochalasin D, all the actin filaments associated with the Listeria break down leaving a fine, fibrillar material that does not decorate with subfragment 1 of myosin. This material is associated with either the surface of the Listeria (the cloud stage) or one end (the tail stage). If the cytochalasin-treated infected macrophages are detergent extracted and then incubated in nuclei-free monomeric actin under polymerizing conditions, actin filaments assemble from the fine, fibrillar material, the result being that each Listeria has actin filaments radiating from its surface like the spokes of a wheel (cloud form) or possesses a long tail of actin filaments formed from the fine, fibrillar material located at one end of the Listeria. Evidence that the fine fibrillar material is involved in nucleating actin assembly comes from a Listeria mutant. Although the mutant replicates at a normal rate in macrophages, actin filaments do not form on its surface (cloud stage) or from one end (tail stage), nor does the bacterium spread. Furthermore it does not form the fine fibrillar material. Evidence that the nucleating material is a secretory product of Listeria and not the macrophage comes from experiments using chloramphenicol, which inhibits protein synthesis in Listeria but not in macrophages. If chloramphenicol is applied 1 h after infection, a time before actin filaments are found attached to the Listeria in untreated macrophages, actin filaments never assemble on the Listeria even when fixed 3 h later. Furthermore the fine fibrillar material is absent, although there is a coat of dense granular material.
单核细胞增生李斯特菌被巨噬细胞吞噬后不久，便会溶解吞噬体膜并进入细胞质。1小时后，肌动蛋白丝包裹住李斯特菌，随后重新排列形成一条尾巴，李斯特菌借此移向巨噬细胞表面，为扩散做准备。如果用细胞松弛素D处理受感染的巨噬细胞，与李斯特菌相关的所有肌动蛋白丝都会分解，留下一种精细的纤维状物质，这种物质不会与肌球蛋白亚片段1结合。这种物质要么与李斯特菌表面相关（云状阶段），要么与一端相关（尾状阶段）。如果用去污剂提取经细胞松弛素处理的受感染巨噬细胞，然后在聚合条件下于无核单体肌动蛋白中孵育，肌动蛋白丝会从这种精细的纤维状物质中组装而成，结果是每个李斯特菌都有从其表面像车轮辐条一样辐射出的肌动蛋白丝（云状形式），或者在李斯特菌一端由精细的纤维状物质形成一条长长的肌动蛋白丝尾巴。有证据表明这种精细的纤维状物质参与肌动蛋白组装的成核过程，这来自一种李斯特菌突变体。尽管该突变体在巨噬细胞中以正常速率复制，但肌动蛋白丝不会在其表面形成（云状阶段），也不会从一端形成（尾状阶段），而且细菌也不会扩散。此外，它不会形成这种精细的纤维状物质。有证据表明成核物质是李斯特菌的分泌产物而非巨噬细胞的，这来自使用氯霉素的实验，氯霉素会抑制李斯特菌中的蛋白质合成，但不会抑制巨噬细胞中的蛋白质合成。如果在感染后1小时（即在未处理的巨噬细胞中发现肌动蛋白丝附着在李斯特菌上之前的时间）应用氯霉素，即使3小时后固定，李斯特菌上也不会形成肌动蛋白丝。此外，尽管有一层致密的颗粒状物质，但精细的纤维状物质不存在。
