Calcium-dependent protein kinase 1 is an essential regulator of exocytosis in Toxoplasma.
Calcium-dependent protein kinase 1 is an essential regulator of exocytosis in Toxoplasma.
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钙调节的胞吐作用是真核生物中普遍存在的过程，分泌囊泡与质膜融合并释放其内容物以响应细胞内钙激增。这个过程调节多种细胞功能，如植物和动物的质膜修复，草履虫防御尖峰的释放，胰腺细胞分泌胰岛素，淋巴细胞分泌免疫调节剂，神经元分泌化学递质。在动物细胞中，丝氨酸/苏氨酸激酶包括PKA、PKC和CaM-激酶已经涉及导致调节分泌的钙信号转导。虽然植物和原生动物也通过细胞内钙调节分泌，但这些信号传递的方式尚未阐明。在这里，我们表明，弓形虫钙依赖性蛋白激酶1（TgCDPK 1）是一个重要的调节钙依赖性胞吐在这个机会人类病原体。TgCDPK 1的条件性抑制显示，它控制钙依赖性分泌的专门细胞器称为微线，导致一个块的基本表型，包括寄生虫的运动，宿主细胞的入侵和出口。使用化学生物学方法重现了这种表型，其中吡唑并嘧啶衍生的化合物特异性抑制TgCDPK 1，并在依赖于微线体分泌的阶段破坏寄生虫生命周期。抑制是特异性的TgCDPK 1，因为耐药激酶突变体逆转敏感性的抑制剂的表达。TgCDPK 1在顶复门动物中是保守的，并且属于与植物和纤毛虫共享的激酶家族，这表明相关的CDPKs可能在其他生物体中的钙调节分泌中发挥作用。由于该激酶家族在哺乳动物宿主中不存在，因此它代表了一个经验证的靶点，可用于针对T.弓形虫和相关的顶复门。
Calcium-regulated exocytosis is a ubiquitous process in eukaryotes, whereby secretory vesicles fuse with the plasma membrane and release their contents in response to an intracellular calcium surge. This process regulates diverse cellular functions like plasma membrane repair in plants and animals, discharge of defensive spikes in Paramecium, and secretion of insulin from pancreatic cells, immune modulators from lymphocytes, and chemical transmitters from neurons. In animal cells, serine/threonine kinases including PKA, PKC and CaM-kinases have been implicated in calcium-signal transduction leading to regulated secretion. Although plants and protozoa also regulate secretion via intracellular calcium, the means by which these signals are relayed have not been elucidated. Here we demonstrate that the Toxoplasma gondii calcium-dependent protein kinase 1 (TgCDPK1) is an essential regulator of calcium-dependent exocytosis in this opportunistic human pathogen. Conditional suppression of TgCDPK1 revealed that it controls calcium-dependent secretion of specialized organelles called micronemes, resulting in a block of essential phenotypes including parasite motility, host-cell invasion, and egress. This phenotype was recapitulated using a chemical biology approach, wherein pyrazolopyrimidine-derived compounds specifically inhibited TgCDPK1 and disrupted the parasite life cycle at stages dependent on microneme secretion. Inhibition was specific to TgCDPK1, since expression of a resistant kinase mutant reversed sensitivity to the inhibitor. TgCDPK1 is conserved among apicomplexans and belongs to a family of kinases shared with plants and ciliates, suggesting that related CDPKs may play a role in calcium-regulated secretion in other organisms. Since this kinase family is absent from mammalian hosts, it represents a validated target that may be exploitable for chemotherapy against T. gondii and related apicomplexans.
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影响因子：
3.3
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