The Evolutionary Origins and Ancestral Features of Septins.
The Evolutionary Origins and Ancestral Features of Septins.
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Septins的进化起源和祖先特征。
DOI：
10.1101/2024.03.25.586683
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发表时间：
2024
期刊：
影响因子：
--
通讯作者：
Onishi,Masayuki
中科院分区：
文献类型：
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作者：
Delic,Samed;Shuman,Brent;Lee,Shoken;Bahmanyar,Shirin;Momany,Michelle;Onishi,Masayuki
Septin 是一类膜相关的细胞骨架鸟嘌呤核苷酸结合蛋白，在细胞分裂、吞噬作用和细胞器分裂等各种细胞过程中发挥着至关重要的作用。尽管脓毒症很重要，但其进化起源和祖先功能仍不清楚。在opisthokonts中，septin形成五个不同的直系同源物组，来自多个组的亚基组装成杂聚物，从而支持它们不同的分子功能。最近的研究表明，脓蛋白在藻类和原生生物中也保守，表明其古老起源于最后一个真核生物共同祖先。然而，真核生物中脓毒症之间的系统发育关系仍不清楚。在这里，我们扩展了非后孔菌脓毒症的列表，包括以前未被识别的来自蓝藻的脓毒症。构建了包含 254 个总脓毒症的有根系统发育树，我们观察到主要的非后康氏脓毒症和后脓毒症脓毒症进化枝之间存在分歧。在非后孔菌脓蛋白中，我们确定了三个主要的分支：第 6 组代表叶绿藻类（6A 主要用于具有单个脓蛋白的物种，6B 用于具有多个脓蛋白的物种），第 7 组代表叶绿藻、异性藻类、触手藻类、金藻类和红藻类中的藻类，第 8 类代表纤毛虫。灰藻和一些纤毛虫败类在所有其他败类和外群之间形成了孤儿谱系。结合祖先序列重建和 AlphaFold 预测，我们追踪了真核生物中脓毒症的结构进化。在 GTPase 结构域中，我们在大多数藻类和纤毛虫物种中的至少一个 septin 的 G 界面内发现了一个保守的 GAP 样精氨酸指。该残基是单个衣藻素二聚化所必需的，并且其丢失与不同谱系中的脓毒蛋白重复事件相一致。精氨酸指的缺失通常伴随着α0螺旋的出现，α0螺旋是一种已知的NC界面相互作用基序，可能意味着septin-septin相互作用机制从同源二聚化到异源寡聚化的多样化。最后，我们在所有脓毒蛋白组中发现了两亲性螺旋，这表明膜结合是一种祖先特征。卷曲螺旋结构域也广泛分布，而在第 6A 组和第 7 组的一些脓蛋白中发现了跨膜结构域。总之，这项研究增进了我们对脓蛋白分布和系统发育分组的理解，揭示了它们的祖先特征、潜在功能和早期进化。
Septins are a family of membrane-associated cytoskeletal guanine-nucleotide binding proteins that play crucial roles in various cellular processes, such as cell division, phagocytosis, and organelle fission. Despite their importance, the evolutionary origins and ancestral function of septins remain unclear. In opisthokonts, septins form five distinct groups of orthologs, with subunits from multiple groups assembling into heteropolymers, thus supporting their diverse molecular functions. Recent studies have revealed that septins are also conserved in algae and protists, indicating an ancient origin from the last eukaryotic common ancestor. However, the phylogenetic relationships among septins across eukaryotes remained unclear. Here, we expanded the list of non-opisthokont septins, including previously unrecognized septins from glaucophyte algae. Constructing a rooted phylogenetic tree of 254 total septins, we observed a bifurcation between the major non-opisthokont and opisthokont septin clades. Within the non-opisthokont septins, we identified three major subclades: Group 6 representing chlorophyte green algae (6A mostly for species with single septins, 6B for species with multiple septins), Group 7 representing algae in chlorophytes, heterokonts, haptophytes, chrysophytes, and rhodophytes, and Group 8 representing ciliates. Glaucophyte and some ciliate septins formed orphan lineages in-between all other septins and the outgroup. Combining ancestral-sequence reconstruction and AlphaFold predictions, we tracked the structural evolution of septins across eukaryotes. In the GTPase domain, we identified a conserved GAP-like arginine finger within the G-interface of at least one septin in most algal and ciliate species. This residue is required for homodimerization of the singleChlamydomonasseptin, and its loss coincided with septin duplication events in various lineages. The loss of the arginine finger is often accompanied by the emergence of the α0 helix, a known NC-interface interaction motif, potentially signifying the diversification of septin-septin interaction mechanisms from homo-dimerization to hetero-oligomerization. Lastly, we found amphipathic helices in all septin groups, suggesting that membrane binding is an ancestral trait. Coiled-coil domains were also broadly distributed, while transmembrane domains were found in some septins in Group 6A and 7. In summary, this study advances our understanding of septin distribution and phylogenetic groupings, shedding light on their ancestral features, potential function, and early evolution.