Mechanism and function of a novel actin nucleator

描述(由申请人提供)：我们最近证明了果蝇尖顶基因的产物P150-Spir(Spir)通过一种独特的机制使肌动蛋白细丝形成(Quinlan等人，2005年)。我们最近发现Spir直接与另一类肌动蛋白核因子卡布奇诺家族的成员结合(初步结果)。这一结果与先前的遗传学研究一致，该研究表明这两种蛋白质在发育中的胚胎中以相同的途径指定前-后轴和背-腹轴(Manseau和Schupach，1989)，并且定位研究表明它们在胚胎和成年哺乳动物组织中具有相同的表达模式(Schumacher等人，2004年)。Spir和Cappuccino家族蛋白在从果蝇到人类和哺乳动物的后生动物物种中都是保守的，每一种已知的表达Spir家族蛋白的生物也表达Cappuccino家族的Forin。然而，尽管它们的保护和它们在发展中的重要性，Spir和Capu的功能和调节还没有被很好地理解。我们的结果表明，Spir和Cappuccino的活性是直接偶联的，它们在体内可能以单丝形成复合体的形式共同发挥作用。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在体内可能被靶向的潜在机制。具体地说，我们将：1.确定肌动蛋白的SPIR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。

DESCRIPTION (provided by applicant): 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.