Toxoplasma ceramide synthases: Gene duplication, functional divergence, and roles in parasite fitness
Toxoplasma ceramide synthases: Gene duplication, functional divergence, and roles in parasite fitness
复制标题
DOI：
10.1096/fj.202201603rrr
复制
发表时间：
2023-11-01
期刊：
影响因子：
4.8
通讯作者：
Denny，Paul W.
中科院分区：
文献类型：
--
作者：
Koutsogiannis，Zisis;Mina，John G.;Denny，Paul W.
刚地弓形虫是一种专性的、细胞内的顶复合体原生动物寄生虫，存在于人类和动物体内，可导致胎儿损伤和流产，免疫抑制者可导致严重疾病。鞘脂作为信号分子具有不可缺少的功能，是真核生物膜的基本和普遍存在的成分，由顶复合体合成和清除。神经酰胺是所有鞘脂的前体，在这里我们报道了弓形虫酰胺合成酶estgcers1和tgcers2的鉴定、定位和分析。有趣的是，我们观察到，虽然tgcers1是酵母神经酰胺合成酶（Lag1p）的全功能同源物，能够催化鞘氨氨酸转化为神经酰胺，但tgcers2却没有催化活性。此外，利用CRISPR/Cas‐9基因缺失tgcers1导致了存活但生长缓慢的寄生虫，这表明它的重要性，但不是必不可少的。相比之下，tgcers2的基因组敲除只能利用雷帕霉素诱导的Cre重组酶系统进行。令人惊讶的是，结果表明，这种“伪”神经酰胺合成酶TgCerS2在寄生虫适应性方面的作用比其催化活性同源物TgCerS1要大得多。系统发育分析表明，与人类和植物一样，中毒菌和其他顶复合体的神经酰胺合成酶异构体可能是通过基因复制产生的。然而，在顶复合体中，复制的副本被假设随后进化成无功能的“伪”神经酰胺合成酶。这种排列是顶复合体所特有的，进一步说明了这些原生动物寄生虫的不寻常的生物学特征。
Toxoplasma gondiiis an obligate, intracellular apicomplexan protozoan parasite of both humans and animals that can cause fetal damage and abortion and severe disease in the immunosuppressed. 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, localization and analyses of theToxoplasmaceramide synthasesTgCerS1 andTgCerS2. Interestingly, we observed that whileTgCerS1 was a fully functional orthologue of the yeast ceramide synthase (Lag1p) capable of catalyzing the conversion of sphinganine to ceramide, in contrastTgCerS2 was catalytically inactive. Furthermore, genomic deletion ofTgCerS1 using CRISPR/Cas‐9 led to viable but slow‐growing parasites indicating its importance but not indispensability. In contrast, genomic knock out ofTgCerS2 was only accessible utilizing the rapamycin‐inducible Cre recombinase system. Surprisingly, the results demonstrated that this “pseudo” ceramide synthase,TgCerS2, has a considerably 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 inToxoplasmaand other Apicomplexa may have arisen through gene duplication. However, in the Apicomplexa the duplicated copy is hypothesized to have 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.