PDF(Pubmed)
Abstract：
An important question in cell biology is how cytoskeletal proteins evolved and drove the development of novel structures and functions. Here we address the origin of SPIRE actin nucleators. Mammalian SPIREs work with RAB GTPases, formin (FMN)-subgroup actin assembly proteins and class-5 myosin (MYO5) motors to transport organelles along actin filaments towards the cell membrane. However, the origin and extent of functional conservation of SPIRE among species is unknown. Our sequence searches show that SPIRE exist throughout holozoans (animals and their closest single-celled relatives), but not other eukaryotes. SPIRE from unicellular holozoans (choanoflagellate), interacts with RAB, FMN and MYO5 proteins, nucleates actin filaments and complements mammalian SPIRE function in organelle transport. Meanwhile SPIRE and MYO5 proteins colocalise to organelles in Salpingoeca rosetta choanoflagellates. Based on these observations we propose that SPIRE originated in unicellular ancestors of animals providing an actin-myosin driven exocytic transport mechanism that may have contributed to the evolution of complex multicellular animals.
摘要：
细胞生物学中的一个重要问题是细胞骨架蛋白如何进化并推动新结构和功能的发展。在这里，我们讨论了SPIRE肌动蛋白成核剂的起源。哺乳动物SPIRE与RABGTPases一起工作，形式蛋白（FMN）-亚组肌动蛋白组装蛋白和5类肌球蛋白（MYO5）马达沿着肌动蛋白丝向细胞膜运输细胞器。然而,物种之间SPIRE功能保护的起源和程度未知。我们的序列搜索表明，SPIRE存在于整个全息动物（动物及其最接近的单细胞亲属）中，但不是其他真核生物。来自单细胞全息动物的SPIRE（小囊鞭毛），与RAB互动，FMN和MYO5蛋白，使肌动蛋白丝成核并补充哺乳动物SPIRE在细胞器转运中的功能。同时，SPIRE和MYO5蛋白共同定位在Salpingoecarosetta鞭毛虫的细胞器上。基于这些观察，我们认为SPIRE起源于动物的单细胞祖先，提供了肌动蛋白-肌球蛋白驱动的胞吞运输机制，这可能有助于复杂多细胞动物的进化。
