Rhomboid 4 (ROM4) affects the processing of surface adhesins and facilitates host cell invasion by Toxoplasma gondii.
Rhomboid 4 (ROM4) affects the processing of surface adhesins and facilitates host cell invasion by Toxoplasma gondii.
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DOI：
10.1371/journal.ppat.1000858
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发表时间：
2010-04-22
期刊：
影响因子：
6.7
通讯作者：
Sibley LD
中科院分区：
文献类型：
--
作者：
Buguliskis JS;Brossier F;Shuman J;Sibley LD
刚地弓形虫粘附宿主细胞依赖于微丝释放的顶端粘附素的极化分泌。随后这些粘附复合物通过肌动蛋白-肌球蛋白马达移位，为运动和宿主细胞侵袭提供动力。侵袭和运动也伴随着通过膜内蛋白水解的表面粘附素的脱落。先前的几项研究已经涉及菱形蛋白酶在这一步骤中，然而，它们在体内的确切作用尚未阐明。使用条件性敲除策略，我们证明了TgROM 4参与表面粘附素的加工，包括MIC 2，AMA 1和MIC 3。TgROM 4的抑制导致粘附素MIC 2释放到上清液中的减少，并伴随着增加该粘附素和其他粘附素的子集的表面表达。TgROM 4的抑制导致正常滑动的破坏，大多数寄生虫在其后端旋转。缺乏TgROM 4的寄生虫更好地结合宿主细胞，但失去了顶端定向的能力，因此大多数未能产生移动连接;因此，入侵严重受损。我们的研究结果表明，TgROM 4参与脱落的微线蛋白从细胞表面。TgROM 4的下调破坏了粘附素的正常顶后梯度，这对于T.刚地。顶复门寄生虫使用多步骤过程侵入宿主细胞，该过程取决于粘附素的调节分泌、对细胞的附着和主动渗透。协调这些活动需要控制适当的时间和释放介导粘附的表面蛋白。弓形虫等寄生虫由于其顶端粘附蛋白的选择性释放而定向附着于其宿主细胞。然后，所产生的复合物沿着寄生虫的长轴移位，从而推动寄生虫进入细胞。细胞侵入的完成还需要这些相互作用最终被切断以允许分离。脱落是通过粘附蛋白在其跨越寄生虫外膜的点处的蛋白水解裂解来完成的。通过破坏膜内蛋白酶菱形体4（ROM 4）的表达，我们证明了它对粘附素的脱落很重要。在不存在ROM 4的情况下，表面粘附蛋白的子集在寄生虫细胞表面上过表达。尽管ROM 4敲低的寄生虫与宿主细胞的结合更好，但它们失去了定向结合的能力，因此在细胞进入中受损。我们的研究结果表明，顶复门寄生虫的宿主细胞入侵依赖于有效感染的表面粘附素的组成性脱落。
Host cell attachment by Toxoplasma gondii is dependent on polarized secretion of apical adhesins released from the micronemes. Subsequent translocation of these adhesive complexes by an actin-myosin motor powers motility and host cell invasion. Invasion and motility are also accompanied by shedding of surface adhesins by intramembrane proteolysis. Several previous studies have implicated rhomboid proteases in this step; however, their precise roles in vivo have not been elucidated. Using a conditional knockout strategy, we demonstrate that TgROM4 participates in processing of surface adhesins including MIC2, AMA1, and MIC3. Suppression of TgROM4 led to decreased release of the adhesin MIC2 into the supernatant and concomitantly increased the surface expression of this and a subset of other adhesins. Suppression of TgROM4 resulted in disruption of normal gliding, with the majority of parasites twirling on their posterior ends. Parasites lacking TgROM4 bound better to host cells, but lost the ability to apically orient and consequently most failed to generate a moving junction; hence, invasion was severely impaired. Our findings indicate that TgROM4 is involved in shedding of micronemal proteins from the cell surface. Down regulation of TgROM4 disrupts the normal apical-posterior gradient of adhesins that is important for efficient cell motility and invasion of host cells by T. gondii. Apicomplexan parasites invade host cells using a multi-step process that depends on regulated secretion of adhesins, attachment to the cell, and active penetration. Coordinating these activities requires control of proper timing and release of surface proteins that mediate adhesion. Parasites like Toxoplasma gondii attach directionally to their host cells due to the selective discharge of adhesive proteins at their apical end. The resulting complexes are then translocated along the long axis of the parasite, thus propelling the parasite into the cell. Completion of cell invasion also requires that these interactions ultimately be severed to allow detachment. Shedding is accomplished by proteolytic cleavage of the adhesive proteins at the point where they span the parasite outer membrane. By disrupting the expression of the intramembrane protease rhomboid 4 (ROM4), we demonstrate that it is important for shedding of adhesins. In the absence of ROM4, a subset of surface adhesive proteins was over-expressed on the parasite cell surface. Although ROM4 knockdown parasites bound better to host cells, they lost their ability to do so directionally, and hence were impaired in cell entry. Our findings demonstrate that host cell invasion by apicomplexan parasites relies on constitutive shedding of surface adhesins for efficient infection.
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DOI：
10.1084/jem.20020258
发表时间：
2002-06-17
期刊：
The Journal of experimental medicine
影响因子：
--
作者：
Barragan A;Sibley LD
通讯作者：
Sibley LD
影响因子：
6.7
作者：
Baker RP;Wijetilaka R;Urban S
通讯作者：
Urban S
影响因子：
3.3
作者：
Håkansson, S;Morisaki, H;Sibley, LD
通讯作者：
Sibley, LD
影响因子：
3.4
作者：
Barragan, A;Brossier, F;Sibley, LD
通讯作者：
Sibley, LD
影响因子：
--
作者：
Brossier, Fabien;Starnes, G. Lucas;Sibley, L. David
通讯作者：
Sibley, L. David