The enteric parasite Entamoeba uses an autocrine catecholamine system during differentiation into the infectious cyst stage
The enteric parasite Entamoeba uses an autocrine catecholamine system during differentiation into the infectious cyst stage
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DOI：
10.1074/jbc.m111895200
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发表时间：
2002-03-08
影响因子：
4.8
通讯作者：
Eichinger, D
中科院分区：
文献类型：
--
作者：
Coppi, A;Merali, S;Eichinger, D
内阿米巴属的肠道阿米巴以包囊形式在宿主之间传播。我们以前表明，在体外包囊发育的侵袭内阿米巴需要另外的定义量的多价半乳糖封端的分子，如粘蛋白的文化。阿米巴表面凝集素结合粘蛋白被假定为传递跨膜信号时，聚集的配体，但下游的凝集素功能的信号分子是未知的。我们在这里报告，内阿米巴包囊诱导半乳糖配体的情况下，当儿茶酚胺被添加到包囊培养基。微摩尔量的肾上腺素和去甲肾上腺素均诱导包囊形成。在所测试的多种合成的儿茶酚胺激动剂中，仅β（1）-肾上腺素能受体激动剂支持包囊形成，而α-和β（2）-肾上腺素能受体激动剂不支持包囊形成。只有β（1）-肾上腺素能受体拮抗剂抑制包囊形成，即使不加入外源性儿茶酚胺也能抑制包囊形成，表明包囊形成需要与儿茶酚胺结合，并提示配体的内源性来源。内阿米巴提取物的高效液相色谱分析表明，阿米巴自身含有儿茶酚胺，并且当细胞被半乳糖终止的配体刺激成包囊时，释放其中至少一种。用放射性标记的儿茶酚胺拮抗剂证实阿米巴滋养体表面存在儿茶酚胺结合位点。在用半乳糖配体或儿茶酚胺刺激分化的细胞中加入β（1）-肾上腺素能受体拮抗剂可抑制阿米巴包囊形成，但用二丁酰cAMP则不能。这表明变形虫儿茶酚胺受体的功能下游的半乳糖凝集素和腺苷酸环化酶的上游。因此，这种肠道原生动物寄生虫含有自分泌儿茶酚胺配体-受体系统的成分，该系统可能与半乳糖凝集素一起作用以调节分化为感染性囊肿阶段。
Enteric amoebae of the genus Entamoeba travel from host to host in an encysted form. We previously showed that in vitro cyst development of Entamoeba invadens requires the addition of defined amounts of multivalent galactose-terminated molecules, such as mucin, to the cultures. The amoeba surface lectin that binds mucin is presumed to convey transmembrane signals when clustered by the ligand, but the signaling molecules that function downstream of the lectin are not known. We report here that Entamoeba encystation was induced in the absence of galactose ligand when catecholamines were added to the encystation medium. Micromolar amounts of both epinephrine and norepinephrine induced encystation. Of a variety of synthetic catecholamine agonists tested, only beta(1)-adrenergic receptor agonists supported encystation, whereas alpha- and beta(2)-adrenergic receptor agonists did not. Only beta(1)-adrenergic receptor antagonists inhibited encystation, and did so even when exogenous catecholamines were not added, indicating that catecholamine binding is required for encystation and suggesting an endogenous source of the ligand. High performance liquid chromatography analysis of Entamoeba extracts showed that the amoebae themselves contain catecholamines and at least one of these is released when the cells are stimulated to encyst with galactose-terminated ligands. The presence of catecholamine binding sites on the surface of amoeba trophozoites was confirmed using radiolabeled catecholamine antagonist. Amoeba encystment was inhibited by addition of beta(1)-adrenergic receptor antagonist to cells that were stimulated to differentiate with either galactose ligand or catecholamines, but not with dibutyryl cAMP. This suggests that the amoeba catecholamine receptor functions downstream of the galactose lectin and upstream of adenylyl cyclase. This enteric protozoan parasite, therefore, contains the components of an autocrine catecholamine ligand-receptor system that may act in conjunction with a galactose lectin to regulate differentiation into the infectious cyst stage.