Mechanism and function of a novel actin nucleator

我们最近发现，果蝇Spire基因的产物P150-Spir(Spir)可以形成肌动蛋白细丝 通过独特的机制形成(Quinlan等人，2005年)。我们最近发现，Spir直接结合到 另一类肌动蛋白核仁的成员，卡布奇诺-福尔明家族(初步结果)。这 这一结果与之前的遗传学研究一致，表明这两种蛋白质的作用是相同的 发育中胚胎的前-后轴和背-腹轴的确定途径(Manseau和 Schupach，1989)和本地化研究表明它们在 胚胎和成年哺乳动物组织(Schumacher等人，2004年)。Spir和Cappuccino家族蛋白 在后生动物中，从果蝇到人类，在哺乳动物和每一种有机体中都是保守的 已知表达Spir家族蛋白的人也表达卡布奇诺家族的Forin。尽管他们 保护及其在发育中的重要性，然而，Spir和Capu的功能和调节 都没有被很好地理解。我们的结果表明，Spir和Cappuccino的活性是直接偶联的 它们可能在体内作为一个单一的微丝形成复合体一起发挥作用。我们的长期目标是 了解这些肌动蛋白成核因素如何共同决定卵母细胞和胚胎的极性。 我们的短期目标是了解Spir和Capu单独和复杂的活动。我们还将 研究这两种蛋白质在体内可能被靶向的潜在机制。具体来说，我们会： 1.用SPIR确定肌动蛋白的成核机制。 2.表征卡布奇诺与肌动蛋白的相互作用。 3.表征Spir与卡布奇诺之间的相互作用。 4.研究Spir FYVE结构域与脂类的相互作用。

We recently showed that the product of the Drosophila spire gene, p150-Spir (Spir) nucleates actin filament formation by a unique mechanism (Quinlan et al.,2005). We recently discovered that Spir binds directly to members of another class of actin nucleators, the Cappuccino-family formins (Preliminary Results). This result is consistent with previous genetic studies indicating that the two proteins operate in the same pathway to specify both anterior-posterior and dorsal-ventral axes of developing embryos (Manseau and Schupach, 1989) and localization studies demonstrating that they have identical expression patterns in embryonic and adult mammalian tissues (Schumacher et al.,2004). Spir- and Cappuccino-family proteins are conserved across metazoan species from fruitflies to humans and in mammals and every organism known to express a Spir-family protein also expresses a Cappuccino-family formin. Despite their conservation and their importance in development, however, the function and regulation of Spir and Capu are not well understood. Our results suggest that the activities of Spir and Cappuccino are directly coupled and that they may function together in vivo as a single filament-forming complex. Our long-term goal is to understand how these actin nucleation factors work together to determine polarity of oocytes and embryos. Our short-term goals are to understand the activities of Spir and Capu alone and in complex. We will also investigate a potential mechanism by which the two proteins may be targeted in vivo. Specifically, we will: 1. Determine the mechanism of actin nucleation by Spir. 2. Characterize the interaction of Cappuccino with actin. 3. Characterize the interaction between Spir and Cappuccino. 4. Characterize the interaction of the Spir FYVE domain with lipids.