Evidence for nuclear localisation of two stage-specific isoenzymes of enolase in Toxoplasma gondii correlates with active parasite replication
Evidence for nuclear localisation of two stage-specific isoenzymes of enolase in Toxoplasma gondii correlates with active parasite replication
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DOI：
10.1016/s0020-7519(02)00129-7
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发表时间：
2002-10-01
影响因子：
4
通讯作者：
Tomavo, S
中科院分区：
文献类型：
--
作者：
Ferguson, DJP;Parmley, SF;Tomavo, S
弓形虫原虫有一个复杂的生活史，包括无性外肠道阶段(速殖子和缓虫体)和球虫型(有性体和无性体)之间的发育过渡(裂殖体、大配子和小配子)。以前的工作已经确定了某些蛋白质在弓形虫中的阶段特异性表达，包括两种糖酵解同工酶：烯醇化酶和乳酸脱氢酶。在这里，我们用免疫细胞化学的方法描述了两种烯醇化酶(ENO1和ENO2)和乳酸脱氢酶(LDH1和LDH2)在体内的表达和亚细胞定位。在小鼠中，肺中增殖的寄生虫表达ENO2和LDH1，并通过存在速殖子特异性表面抗原(SAG 1)而被定性为速殖子。相反，ENO1和LDH2是由脑组织包囊中存在的缓殖子表达的，其特征是存在缓殖子特异性抗原(BAG1)。在阶段转换(速殖子/缓殖子)期间，同工酶的变化发生在缓殖子活跃增殖的早期阶段，因此可能不仅仅是反映代谢需求的减少。在猫肠道检查球虫阶段时，SAG1、BAG1、LDH2和ENO1均为阴性，但与速殖子相似，LDH1和ENO2呈强阳性表达。LDH1和LDH2同工酶仅在细胞质中表达。相反，观察到ENO1和ENO2在细胞核中的标记最强，但胞浆染色较弱。免疫电子显微镜证实了乳酸脱氢酶的胞质定位和烯醇化酶的主要核定位。在早期的细胞内增殖和发育中，生命周期的所有阶段(速殖子、缓殖子和球虫阶段)都显示出很强的烯醇化酶核标记，但在成熟寄生虫中，这种标记明显减少到低于细胞质中的水平。烯醇化酶的核定位似乎与核活动(转录和/或分裂)有关，除了在糖酵解中发挥作用外，还可能在寄生虫增殖和分化过程中的基因调控中发挥一定的作用。(C)2002年澳大利亚寄生虫学协会。爱思唯尔科学有限公司出版。保留所有权利。
The protozoan parasite Toxoplasma gondii has a complex life cycle involving the developmental transition between the asexual exoenteric stages (tachyzoites and bradyzoites) and the coccidian (sexual and asexual) forms (schizonts, macrogametes and microgametes). Previous work has established the stage-specific expression of certain proteins including two glycolytic isoenzymes of enolase and lactate dehydrogenase in T. gondii. Here we describe the expression and subcellular localisation of the two isoforms of enolase (ENO1 and ENO2) and lactate dehydrogenase (LDH1 and LDH2) in vivo using immunocytochemistry. In mice, proliferating parasites in the lung expressed ENO2 and LDH1 and were characterised as tachyzoites by the presence of a tachyzoite specific surface antigen (SAG 1). In contrast, ENO1 and LDH2 were expressed by bradyzoites present in tissue cysts in the brain characterised by the presence of the bradyzoite-specific antigen (BAG1). During stage conversion (tachyzoite/bradyzoite), the isoenzyme changes occur at an early stage when the bradyzoites are actively proliferating and thus may not simply be reflecting reduced metabolic needs. When the coccidian stages were examined in the cat intestine, they were negative for SAG1, BAG1, LDH2 and ENO1 but were similar to the tachyzoite in strongly expressing LDH1 and ENO2. The isoenzymes LDH1 and LDH2 were exclusively expressed in the cytoplasm. In contrast, it was observed that the strongest labelling for both ENO1 and ENO2 was observed in the nucleus with less intense but specific cytoplasmic staining. Immunoelectron microscopy confirmed the cytoplasmic location of LDH and the predominantly nuclear location of enolase. During early intracellular proliferation and development, all stages of the life cycle (tachyzoite, bradyzoite and coccidian stages) exhibited very strong nuclear labelling for enolase but this was markedly reduced in mature parasites to levels below that seen in the cytoplasm. The specific nuclear localisation of enolases appears to be associated with nuclear activity (transcription and/or division) and may play some part in the control of gene regulation during parasite proliferation and differentiation in addition to its role in glycolysis. (C) 2002 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.