Epidermal growth factor binds to a receptor on Trypanosoma cruzi amastigotes inducing signal transduction events and cell proliferation
Epidermal growth factor binds to a receptor on Trypanosoma cruzi amastigotes inducing signal transduction events and cell proliferation
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DOI：
10.1111/j.1550-7408.2002.tb00216.x
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发表时间：
2002-09-01
影响因子：
2.2
通讯作者：
Lima, MF
中科院分区：
文献类型：
--
作者：
Ghansah, TJ;Ager, EC;Lima, MF
宿主生长因子诱导克氏锥虫无鞭毛体增殖的机制尚不清楚。在这里，我们检测了人表皮生长因子(EGF)与哺乳动物繁殖型毛滴虫结合并诱导寄生虫生长的能力。EGF以浓度依赖的方式刺激[H-3]胸腺嘧啶核苷掺入DNA和无鞭毛体生长。放射性标记的EGF以浓度依赖且可饱和的方式与无鞭毛体结合，但不与类鞭毛体结合。Scatchard分析表明，每个无鞭毛体只有一类受体，其K-d为0.8 nm，数量为3.1×103。内化实验结果为受体介导的EGF内吞作用提供了证据。Northern分析显示，在无鞭毛虫中有一条3.0kb的EGF受体(EGFR)同源基因的转录本，而在类鞭毛虫中则没有。表皮生长因子与无鞭毛体结合可诱导信号转导事件。通过将γ-[P-32]-ATP掺入无鞭毛体蛋白来确定EGF诱导的“体外”激酶活性。EGF还以浓度依赖的方式增加蛋白激酶C的活性，以时间和浓度依赖的方式增加丝裂原活化蛋白(MAP)的活性。EGFR的特异性抑制剂(AG14782)和MAP激酶抑制剂(PD98059)可降低依赖于EGF的克氏锥虫MAP激酶活性。这些结果描述了无鞭毛体通过依赖于EGF的信号转导途径来调节其增殖的一种新机制。
Host growth factors induce proliferation of Trypanosoma cruzi amastigotes by mechanisms that remain poorly defined. Here we examined human epidermal growth factor (EGF) for its ability to bind to the mammalian multiplicative forms of T. cruzi and to induce growth of the parasites. EGF stimulated incorporation of [H-3] thymidine into DNA and growth of amastigotes both in a concentration-dependent manner. Radiolabeled EGF was found to bind to amastigotes in a concentration-dependent and saturable manner but it did not bind to trypomastigotes. Scatchard analysis showed a single class of receptors with a K-d of 0.8 nM and numbering 3.1 X 103 per amastigote. Results from internalization experiments provided evidence of receptor-mediated endocytosis of EGF. Northern analysis showed a 3.0-kb transcript for the putative EGF receptor (EGFR) homologue in amastigotes, but not trypomastigotes. Binding of EGF to amastigotes induced signal transduction events. EGF induced "in vitro" kinase activity as determined by gamma-[P-32] ATP incorporation into amastigote proteins. EGF also increased protein kinase C activity in a concentration-dependent manner and Mitogen Activated Protein (MAP) kinase activity in a time- and concentration-dependent manner. A specific inhibitor (AG14782) of the EGFR and a MAP kinase inhibitor (PD98059) decreased EGF-dependent T. cruzi MAP kinase activity. These results describe a novel mechanism used by amastigotes to regulate their proliferation mediated by an EGF-dependent signal transduction pathway.