Toxoplasma ceramide synthases: a curious case of gene duplication, divergence and key functionality
Toxoplasma ceramide synthases: a curious case of gene duplication, divergence and key functionality
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DOI：
10.1101/2022.01.05.475179
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发表时间：
2022-01
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影响因子：
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通讯作者：
Zisis Koutsogiannis;John G. M. Mina;C. Albus;M. Kol;J. Holthuis;E. Pohl;P. Denny
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作者：
Zisis Koutsogiannis;John G. M. Mina;C. Albus;M. Kol;J. Holthuis;E. Pohl;P. Denny
刚地弓形虫是一种专性的、细胞内真核顶复门原虫寄生虫，可引起动物和人类的胎儿损伤和流产。鞘脂作为信号分子具有不可或缺的功能，是真核生物膜的必需和普遍存在的组分，由顶复门合成和清除。神经酰胺是所有鞘脂的前体，在这里，我们报告的识别，定位和分析的弓形虫神经酰胺脱氢酶TgCerS 1和TgCerS 2，并使用条件基因调控的方法，建立其在致病性和寄生虫健身的作用。有趣的是，我们观察到，虽然TgCerS 1是能够催化二氢鞘氨醇转化为神经酰胺的酵母Lag 1 p的全功能直向同源物，但相比之下，TgCerS 2没有催化活性。此外，使用CRISPR/Cas-9的TgCerS 1基因组缺失导致存活但生长缓慢的寄生虫，表明其重要性但不是不可或缺的。相比之下，基因组敲除TgCerS 2只能利用雷帕霉素诱导的Cre重组酶系统。令人惊讶的是，结果表明，这种“假”神经酰胺合酶TgCerS 2在寄生虫适应性中的作用甚至比其催化活性直向同源物（TgCerS 1）更大。系统发育分析表明，在人类和植物中，神经酰胺合酶亚型发现弓形虫和其他Apicomplexa通过基因复制。然而，在Apicomplexa中，复制的拷贝随后演变成一个无功能的“假”神经酰胺合酶。这种安排是独特的Apicomplexa，并进一步说明了不寻常的生物学特性，这些原生动物寄生虫，一个功能，可能会被利用在开发新的抗原动物。鞘脂是真核生物中普遍存在的必需脂质，由寄生的顶复门原虫（包括刚地弓形虫）合成和清除。神经酰胺是所有鞘脂的前体，在这里，我们报告的识别，定位和分析的弓形虫神经酰胺脱氢酶TgCerS 1和TgCerS 2。令人惊讶的是，虽然TgCerS 1是完全功能性的，催化二氢鞘氨醇转化为神经酰胺，但TgCerS 2是无催化活性的。然而，我们证明了这种“假”神经酰胺合酶在寄生虫适应性中的作用比催化活性的TgCerS 1更大。系统发育分析表明，这些异构体出现通过基因复制和复制副本随后演变成'假'神经酰胺合酶。这种排列是Apicomplexa所独有的，进一步说明了这些原生动物寄生虫的高度不寻常的生物学特征，这一特征可能被用于开发新的抗原动物。
Toxoplasma gondii is an obligate, intracellular eukaryotic apicomplexan protozoan parasite that can cause foetal damage and abortion in both animals and humans. Sphingolipids have indispensable functions as signaling molecules and are essential and ubiquitous components of eukaryotic membranes that are both synthesized and scavenged by the Apicomplexa. Ceramide is the precursor for all sphingolipids, and here we report the identification, localisation and analyses of the Toxoplasma ceramide synthases TgCerS1 and TgCerS2 and, using a conditional gene regulation approach, establish their roles in pathogenicity and parasite fitness. Interestingly, we observed that whilst TgCerS1 was a fully functional orthologue of the yeast Lag1p capable of catalysing the conversion of sphinganine to ceramide, in contrast TgCerS2 was catalytically inactive. Furthermore, genomic deletion of TgCerS1 using CRISPR/Cas-9 led to viable but slow growing parasites indicating its importance but not indispensability. In contrast, genomic knock out of TgCerS2 was only accessible utilising the rapamycin-inducible Cre recombinase system. Surprisingly, the results demonstrated that this ‘pseudo’ ceramide synthase, TgCerS2, has an even greater role in parasite fitness than its catalytically active orthologue (TgCerS1). Phylogenetic analyses indicated that, as in humans and plants, the ceramide synthase isoforms found in Toxoplasma and other Apicomplexa arose through gene duplication. However, in the Apicomplexa the duplicated copy subsequently evolved into a non-functional ‘pseudo’ ceramide synthase. This arrangement is unique to the Apicomplexa and further illustrates the unusual biology that characterize these protozoan parasites, a feature that could potentially be exploited in the development of new antiprotozoals. Author Summary Sphingolipids, essential and ubiquitous lipids in the Eukaryota, are both synthesized and scavenged by the parasitic apicomplexan protozoa, including Toxoplasma gondii. Ceramide is the precursor for all sphingolipids and here we report the identification, localisation and analyses of the Toxoplasma ceramide synthases TgCerS1 and TgCerS2. Surprisingly, whilst TgCerS1 was fully functional, catalysing the conversion of sphinganine to ceramide, TgCerS2 was catalytically inactive. However, we demonstrated that this ‘pseudo’ ceramide synthase has an even greater role in parasite fitness than the catalytically active TgCerS1. Phylogenetic analyses indicated that these isoforms arose through gene duplication and the duplicated copy subsequently evolved into the ‘pseudo’ ceramide synthase. This arrangement is unique to the Apicomplexa and further illustrates the highly unusual biology that characterizes these protozoan parasites, a feature that could potentially be exploited for the development of new antiprotozoals.