Cancer Research UK Beatson Institute for Cancer Research, Bearsden, Glasgow G61 1BD, Scotland, UK.
J Cell Biol. 2011 May 30;193(5):831-9. doi: 10.1083/jcb.201009119. Epub 2011 May 23.
WASP and SCAR homologue (WASH) is a recently identified and evolutionarily conserved regulator of actin polymerization. In this paper, we show that WASH coats mature Dictyostelium discoideum lysosomes and is essential for exocytosis of indigestible material. A related process, the expulsion of the lethal endosomal pathogen Cryptococcus neoformans from mammalian macrophages, also uses WASH-coated vesicles, and cells expressing dominant negative WASH mutants inefficiently expel C. neoformans. D. discoideum WASH causes filamentous actin (F-actin) patches to form on lysosomes, leading to the removal of vacuolar adenosine triphosphatase (V-ATPase) and the neutralization of lysosomes to form postlysosomes. Without WASH, no patches or coats are formed, neutral postlysosomes are not seen, and indigestible material such as dextran is not exocytosed. Similar results occur when actin polymerization is blocked with latrunculin. V-ATPases are known to bind avidly to F-actin. Our data imply a new mechanism, actin-mediated sorting, in which WASH and the Arp2/3 complex polymerize actin on vesicles to drive the separation and recycling of proteins such as the V-ATPase.
WASP 和 SCAR 同源物 (WASH) 是一种新发现的、进化上保守的肌动蛋白聚合调节因子。本文表明，WASH 包被成熟的 Dictyostelium discoideum 溶酶体，并对不消化物质的胞吐作用至关重要。一个相关的过程，即致命的内体病原体 Cryptococcus neoformans 从哺乳动物巨噬细胞中的排出，也使用 WASH 包被的囊泡，并且表达显性负性 WASH 突变体的细胞不能有效地排出 C. neoformans。D. discoideum WASH 导致溶酶体上形成丝状肌动蛋白 (F-actin) 斑点，导致液泡三磷酸腺苷酶 (V-ATPase) 的去除和溶酶体的中和形成后溶酶体。没有 WASH，就不会形成斑点或包被，不会看到中性后溶酶体，也不会排出葡聚糖等不消化的物质。当肌动蛋白聚合被 latrunculin 阻断时，会出现类似的结果。已知 V-ATPases 与 F-actin 紧密结合。我们的数据暗示了一种新的机制，即肌动蛋白介导的分选，其中 WASH 和 Arp2/3 复合物在囊泡上聚合肌动蛋白，以驱动 V-ATPase 等蛋白质的分离和回收。
