Mechanism and function of a novel actin nucleator

描述（由申请人提供）：我们最近发现果蝇的螺旋基因产物p150-Spir （Spir）通过一种独特的机制形成肌动蛋白丝（Quinlan et al., 2005）。我们最近发现Spir直接与另一类肌动蛋白成核蛋白成员结合，即卡布奇诺家族形成蛋白（初步结果）。这一结果与先前的遗传学研究一致，表明这两种蛋白在相同的途径中指定发育胚胎的前后轴和背腹轴（Manseau and Schupach, 1989），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 et al., 2004）。Spir-和卡布奇诺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，每一种已知表达Spir-家族蛋白的生物也表达卡布奇诺家族的formin。然而，尽管Spir和Capu基因保存完好，在发育过程中也很重要，但它们的功能和调控尚不清楚。我们的研究结果表明，Spir和卡布奇诺的活性是直接耦合的，它们可能在体内作为一个单一的细丝形成复合物一起起作用。我们的长期目标是了解这些肌动蛋白成核因子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斯皮尔和卡普的单独和复杂的活动。我们还将研究这两种蛋白在体内可能被靶向的潜在机制。具体来说，我们将：1。用Spir测定肌动蛋白成核的机理。描述卡布奇诺与肌动蛋白的相互作用。3. 描述Spir和Cappuccino之间的相互作用。表征Spir FYVE结构域与脂质的相互作用。

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.