Evidence for a "Wattle and Daub'' Model of the Cyst Wall of Entamoeba
Evidence for a "Wattle and Daub'' Model of the Cyst Wall of Entamoeba
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DOI：
10.1371/journal.ppat.1000498
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发表时间：
2009-07-01
期刊：
影响因子：
6.7
通讯作者：
Samuelson, John
中科院分区：
文献类型：
--
作者：
Chatterjee, Anirban;Ghosh, Sudip K.;Samuelson, John
入侵内阿米巴(EI)的囊壁由几丁质纤维和三种几丁质结合凝集素(Jacob、Jessie3和几丁质酶)组成，是人类病原体的模型。在这里，我们展示了几丁质，它是由小麦胚芽凝集素检测到的，在沉积在包囊EI表面之前，是在分泌小泡中生成的。雅各布凝集素和几丁质酶都是在包囊形成的早期形成的，它们都具有排列成卷曲的几丁质结合结构域(CBD)和几丁质酶(具有N端CBD)。这些结果与它们在交联几丁质纤维(雅各布凝集素)和重塑囊壁(几丁质酶)中的假设作用是一致的。Jessie3凝集素可能形成囊壁的灰泥或涂抹物，因为1)Jessie凝集素是在包囊后期产生的；2)向囊壁添加Jessie凝集素与囊壁对核酸染色(DAPI)和肌动蛋白结合七肽(Pallidin)的渗透性显著降低有关；以及3)重组Jessie凝集素，在大肠杆菌周质中表达为麦芽糖结合蛋白，导致转化细菌在悬浮中凝集，并形成离心后不解离的硬颗粒。分泌型重组蛋白阴性染色显示Jessie3呈线状和玫瑰花环状。这些发现为内阿米巴孢囊壁的“片状和涂抹式”模型提供了证据，在添加砂浆或涂抹剂(耶西3凝集素)之前，片状或棒状(甲壳素纤维很可能由雅各布凝集素交叉连接)被构建。
The cyst wall of Entamoeba invadens (Ei), a model for the human pathogen Entamoeba histolytica, is composed of fibrils of chitin and three chitin-binding lectins called Jacob, Jessie3, and chitinase. Here we show chitin, which was detected with wheat germ agglutinin, is made in secretory vesicles prior to its deposition on the surface of encysting Ei. Jacob lectins, which have tandemly arrayed chitin-binding domains (CBDs), and chitinase, which has an N-terminal CBD, were each made early during encystation. These results are consistent with their hypothesized roles in cross-linking chitin fibrils (Jacob lectins) and remodeling the cyst wall (chitinase). Jessie3 lectins likely form the mortar or daub of the cyst wall, because 1) Jessie lectins were made late during encystation; 2) the addition to Jessie lectins to the cyst wall correlated with a marked decrease in the permeability of cysts to nucleic acid stains (DAPI) and actin-binding heptapeptide (phalloidin); and 3) recombinant Jessie lectins, expressed as a maltose-binding proteins in the periplasm of Escherichia coli, caused transformed bacteria to agglutinate in suspension and form a hard pellet that did not dissociate after centrifugation. Jessie3 appeared as linear forms and rosettes by negative staining of secreted recombinant proteins. These findings provide evidence for a "wattle and daub'' model of the Entamoeba cyst wall, where the wattle or sticks (chitin fibrils likely cross-linked by Jacob lectins) is constructed prior to the addition of the mortar or daub (Jessie3 lectins).