A spatially localized rhomboid protease cleaves cell surface adhesins essential for invasion by Toxoplasma
A spatially localized rhomboid protease cleaves cell surface adhesins essential for invasion by Toxoplasma
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DOI：
10.1073/pnas.0407918102
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发表时间：
2005-03-15
影响因子：
11.1
通讯作者：
Urban, S
中科院分区：
文献类型：
--
作者：
Brossier, F;Jewett, TJ;Urban, S
Apicomplexan寄生虫引起严重的人类和动物疾病，这种治疗需要鉴定新的治疗靶标。宿主 - 细胞侵袭最终导致寄生虫粘附素的必要裂解，尽管尚未发现负责该加工的蛋白酶在其跨膜结构域中的几个粘附素图的裂解位点。我们已经确定，克隆和表征了五个非蒙臂菱形内膜内蛋白酶，该蛋白酶在最近完成的弓形虫Gondii基因组中编码。四个T. gondii菱形（TGROM）是具有相似底物特异性的活性蛋白酶。 TGROM1，TGROM4和TGROM5在负责该疾病的次唑次阶段表达，而TGROM2和TGROM3在参与传播的卵囊阶段表示。尽管TGROM5和TGROM4均位于速二菌中的细胞表面，但TGROM5主要在寄生虫的后部，而将粘合剂隔离在内属内膜中。在侵袭过程中发生的微原质分泌后，米云2粘附素被分泌到顶端末端，并易位到后部，即裂解部位，仅与TGROM共定位。此外，只有TGROM能够在基于细胞的测定中裂解MIC粘附素，这表明它可能提供了入侵所需的关键蛋白酶活动。 T. gondii菱形在包括疟疾在内的其他Apicomplexans中具有明显的同源物。因此，我们的发现为研究这种致命的病原体的侵袭提供了模型，并为治疗干预提供了目标。
Apicomplexan parasites cause serious human and animal diseases, the treatment of which requires identification of new therapeutic targets. Host-cell invasion culminates in the essential cleavage of parasite adhesins, and although the cleavage site for several adhesins maps within their transmembrane domains, the protease responsible for this processing has not been discovered. We have identified, cloned, and characterized the five nonmitochondrial rhomboid intramembrane proteases encoded in the recently completed genome of Toxoplasma gondii. Four T. gondii rhomboids (TgROMs) were active proteases with similar substrate specificity. TgROM1, TgROM4, and TgROM5 were expressed in the tachyzoite stage responsible for the disease, whereas TgROM2 and TgROM3 were expressed in the oocyst stage involved in transmission. Although both TgROM5 and TgROM4 localized to the cell surface in tachyzoites, TgROM5 was primarily at the posterior of the parasite, whereas adhesins were sequestered in internal micronemes. Upon microneme secretion, as occurs during invasion, the MIC2 adhesin was secreted to the apical end and translocated to the posterior, the site of cleavage, where it colocalized only with TgROMS. Moreover, only TgROMS was able to cleave MIC adhesins in a cell-based assay, indicating that it likely provides the key protease activity necessary for invasion. T. gondii rhomboids have clear homologues in other apicomplexans including malaria; thus, our findings provide a model for studying invasion by this deadly pathogen and offer a target for therapeutic intervention.