CELL SIGNALLING IN C ELEGANS

拟议研究的长期目标是了解细胞是如何 通过外阴诱导，信号控制细胞的生长和分化 在线虫中作为一个模型系统。许多控制外阴的信号基因 诱导作用已经从遗传学和分子水平上得到了证实。有些是 构成受体酪氨酸激酶途径的基因的同源物 哺乳动物和果蝇，包括let-23(一种受体酪氨酸激酶基因)， Let-60(ras同源物)和MPK-1(MAPK同源物)。其他外阴 信号基因(如LIN-2、LIN-7和LIN-10)可能会延长这一过程 高度保守的信号通路，因为它们可能识别新的信号 步骤，因为它们与以前 在这种类型的信号通路中被识别。 在LIN-2和LIN-7中发现的蛋白质基序表明了几种可能的 关于这些蛋白质如何与受体酪氨酸相互作用的解释 蛋白水解酶途径。这些蛋白质类似于一类紧密连接 哺乳动物和果蝇的蛋白质，提示LIN-2和LIN-7 (可能也是LIN-10)可能是线虫Tell的组成成分 它们的功能是将let-23受体定位于 极化的外阴前体细胞的基面。在这个模型中，这是 Let-23受体的不对称分布对其 激活。LIN-2还包含一个类似于 参与鸟嘌呤核苷酸代谢的酶，提出了另一种选择 LIN-2与GTP酶活性相互作用的模型 拉斯。 将使用三种方法来确定这些新信令的作用 外阴诱导中的基因。首先，每个模型都做出了具体的预测 关于各种LIN-2蛋白结构域的功能重要性 和预测的酶活性；这些预测将得到检验。 其次，LIN-2、LIN-7和LIN-10之间的相互作用将定义为 确定这些蛋白质是否定位于 以及它们是否在物理上相互作用。第三， 受体定位模型将通过确定LET是否- 23受体主要集中在外阴前体细胞的基底面， 以及这种极化分布是否需要LIN-2、LIN-7和LIN-10。 支持这一模型的数据将进一步加深我们对 但人们对细胞极性和细胞之间的关系知之甚少 发信号。 拟议的对新细胞功能的调查涉及高度- 保守的受体酪氨酸激酶信号通路与 了解肿瘤的形成，因为类似的结构性激活 哺乳动物细胞中的通路是致癌的。

The long term goal of the proposed research is to understand how cell signaling controls cell growth and differentiation, using vulval induction in C. elegans as a model system. Many signaling genes that control vulval induction have been genetically and molecularly identified. Some are homologs of genes that constitute the receptor tyrosine kinase pathway in mammals and Drosophila, including let-23 (a receptor tyrosine kinase gene), let-60 (a ras homolog) and mpk-1 (a MAP kinase homolog). Other vulval signaling genes (such as lin-2, lin-7 and lin-10) are likely to extend this highly-conserved signaling pathway because they may identify new signaling steps, since they are not similar to genes that have previously been identified in this type of signaling pathway. Protein motifs found in LIN-2 and LIN-7 suggest several possible explanations about how these proteins interact with the receptor tyrosine kinase pathway. These proteins are similar to a class of tight junction proteins in mammals and Drosophila, suggesting that LIN-2 and LIN-7 (possible LIN-10 as well) may be constituents of the nematode tight junction, and that their function is to localize the LET-23 receptor to the basal surface of polarized vulval precursor cells. In this model, this asymmetric distribution of the LET-23 receptor would be essential for its activation. LIN-2 also contains a protein domain that is similar to an enzyme involved in guanine nucleotide metabolism, suggesting an alternative model involving an interaction between LIN-2 and the GTPase activity of Ras. Three approaches will be used to determine the role of these new signaling genes in vulval induction. First, each model makes specific predictions regarding the functional importance of the various lIN-2 protein domains and predicted enzymatic activities; these predictions will be tested. Second, the interactions between LIN-2, LIN-7 and LIN-10 will be defined by determining whether these proteins are localized to the same region within the cell and whether they physically interact with each other. Third, the receptor localization model will be tested by determining whether the LET- 23 receptor is concentrated on the basal surface of vulval precursor cells, and whether this polarized distribution requires LIN-2, LIN-7 and LIN-10. Data supporting this model will further our understanding of the important but poorly understood relationship between cell polarity and cell signaling. The proposed investigation of new cellular functions involved in a highly- conserved receptor tyrosine kinase signaling pathway is relevant to understanding tumor formation, since constitutive activation of similar pathways in mammalian cells is oncogenic.