An Interdisciplinary Approach to PKD2 Function

描述（由申请人提供）：TRP超家族包括一大批与果蝇TRP通道同源的阳离子通道，在光转导中起关键作用。在七个TRP亚家族中，TRPP蛋白受到特别关注，因为创始成员PKD2的突变可导致常染色体显性多囊肾病（ADPKD）。TRPP通道是进化保守的，在其他生物中也有，在雄性生殖中起着关键作用。最近的一些研究表明，TRPP家族的成员可以在纤毛结构中发现，它们被认为参与机械感觉信号转导途径。然而，尽管深入研究，TRPP生物学的许多方面仍然存在争议，包括TRPP的亚细胞定位和参与TRPP信号通路的蛋白质的身份。利用异源表达系统解决这些问题已经做了许多尝试。然而，结果并不总是一致的，而且很难在体内验证。我们开发了一个果蝇模型系统，在果蝇的PKD2同源物中有一个靶向突变（命名为amo，意为Almost There）。携带amo零突变的雄性果蝇被发现具有正常数量的活动精子，但由于精子无法储存在雌性储存器官中而无法生育。此外，我们发现Amo集中在精子鞭毛的尖端，这表明TRPPs在轴突结构中的保守作用。这种果蝇系统为我们提供了使用遗传上可处理的模式生物将体外研究结果与体内分析相关联的机会。在本提案中，我们将使用多学科方法来解决TRPP生物学中三个尚未解决的问题：1)体内TRPP2定位的发育调节2)体内TRPP2功能的阳离子通道活性要求3)TRPP信号级联的上游和下游组分的鉴定。我们预计这些研究将为TRPP类离子通道的关键功能和信号特性提供新的信息。

DESCRIPTION (provided by applicant): The TRP superfamily comprises a large group of cation channels with homology to the Drosophila TRP channel, which plays a key role in phototransduction. Among the seven TRP subfamilies, the TRPP proteins are of particular interest because mutations in the founding member, PKD2, result in Autosomal Dominant Polycystic Kidney Disease (ADPKD). TRPP channels are evolutionary conserved and in other organisms and play a key role in male fertility. A number of recent studies have demonstrated that members of the TRPP family can be found in ciliated structures where they are thought to participate in mechanosensory signal transduction pathways. Despite intensive investigation, however, there are numerous aspects of TRPP biology that remain controversial including the subcellular localization of TRPPs and the identity of proteins that participate in TRPP signaling pathways. Many attempts have been made to address these questions using heterologous expression systems. However, the results have not always been consistent and they have been difficult to verify in vivo. We have developed a Drosophila model system with a targeted mutation in the fly homologue of PKD2 (named amo for Almost There). Male flies carrying a null mutation in amo were found to have normal amounts of motile sperm but are infertile due to an inability of sperm to be stored in the female storage organs. In addition we find that Amo is concentrated at the tip of the sperm flagella suggesting a conserved role for TRPPs in axonemal structures. This Drosophila system offers us the opportunity to use a genetically tractable model organism to correlate in vitro findings with in vivo analyses. In this proposal we will use a multidisciplinary approach to address three unresolved issues in TRPP biology: 1) the developmental regulation of TRPP2 localization in vivo 2) The requirement of cation channel activity for TRPP2 function in vivo and 3) the identification of upstream and downstream components of the TRPP signaling cascade. We anticipate that these studies will provide new information about the critical functional and signaling properties of the TRPP class of ion channels.