Proteases have been implicated in a variety of developmental processes during the malaria parasite lifecycle. In particular, invasion and egress of the parasite from the infected hepatocyte and erythrocyte, critically depend on protease activity. Although falcipain-1 was the first cysteine protease to be characterized in P. falciparum, its role in the lifecycle of the parasite has been the subject of some controversy. While an inhibitor of falcipain-1 blocked erythrocyte invasion by merozoites, two independent studies showed that falcipain-1 disruption did not affect growth of blood stage parasites. To shed light on the role of this protease over the entire Plasmodium lifecycle, we disrupted berghepain-1, its ortholog in the rodent parasite P. berghei. We found that this mutant parasite displays a pronounced delay in blood stage infection after inoculation of sporozoites. Experiments designed to pinpoint the defect of berghepain-1 knockout parasites found that it was not due to alterations in gliding motility, hepatocyte invasion or liver stage development and that injection of berghepain-1 knockout merosomes replicated the phenotype of delayed blood stage growth after sporozoite inoculation. We identified an additional role for berghepain-1 in preparing blood stage merozoites for infection of erythrocytes and observed that berghepain-1 knockout parasites exhibit a reticulocyte restriction, suggesting that berghepain-1 activity broadens the erythrocyte repertoire of the parasite. The lack of berghepain-1 expression resulted in a greater reduction in erythrocyte infectivity in hepatocyte-derived merozoites than it did in erythrocyte-derived merozoites. These observations indicate a role for berghepain-1 in processing ligands important for merozoite infectivity and provide evidence supporting the notion that hepatic and erythrocytic merozoites, though structurally similar, are not identical.

在疟原虫的生命周期中，蛋白酶与多种发育过程有关。特别地，寄生虫从受感染的肝细胞和红细胞的侵袭和流出严重地取决于蛋白酶的活性。尽管falcipain-1是第一个在P中鉴定出的半胱氨酸蛋白酶。恶性疟原虫，其在寄生虫生命周期中的作用一直是一些争议的主题。尽管falcipain-1的抑制剂阻止了裂殖子对红细胞的侵袭，但两项独立的研究表明，falcipain-1的破坏并不影响血期寄生虫的生长。为了阐明这种蛋白酶在整个疟原虫生命周期中的作用，我们破坏了其在啮齿动物寄生虫P中的直系同源基因berghepain-1。。贝热。我们发现这种突变体寄生虫在接种子孢子后在血液阶段感染中显示出明显的延迟。旨在确定berghepain-1敲除寄生虫缺陷的实验发现，这不是由于滑行运动的改变，肝细胞浸润或肝阶段发育所致，而注射berghepain-1敲除的血清体复制了子孢子接种后血液阶段生长延迟的表型。 。我们确定了berghepain-1在制备血液阶段裂殖子以感染红细胞方面的其他作用，并观察到berghepain-1敲除的寄生虫表现出网状细胞的限制，表明berghepain-1活性拓宽了该寄生虫的红细胞库。缺乏berghepain-1的表达导致肝细胞衍生的裂殖子中红细胞感染性的降低比其衍生于红细胞的裂殖子中更大。这些观察结果表明了伯氏肝素-1在加工对裂殖子感染性重要的配体中的作用，并提供证据支持肝和红细胞裂殖子尽管结构相似但并不相同的观点。