Components of Translation in Signal Transduction

该项目的重点是人类细胞中翻译装置的两个重要组成部分的新活动。这些组分是氨酰tRNA合成酶。在其典型作用中，氨酰tRNA合成酶在蛋白质合成的第一步催化转移RNA的氨酰化，从而建立遗传密码的规则。组成蛋白质的20种氨基酸中的每一种都有一个单独的、不同的氨酰tRNA合成酶。在最近的工作中，我们报道了一种特定的tRNA合成酶--氨基酸酪氨酸--可以被分成两种不同的细胞因子。虽然全长蛋白是无活性的，但这两个片段是具有不同生物活性的有效细胞因子。该蛋白质在细胞培养物中的细胞凋亡期间分泌，然后可以被蛋白酶如白细胞弹性蛋白酶切割。在进一步未发表的工作中，我们发现该合成酶的上述片段及其作用于氨基酸色氨酸的密切同系物的片段在血管生成或血管抑制中具有活性。（蛋白水解或选择性剪接产生后一种酶的片段。本项目的目的是扩大和进一步验证这些片段在血管生成或血管抑制中的活性的初步观察，使用几种不同的体内血管生成测定。参与血管生成途径的受体，负责活动的蛋白质内的特定基序，分泌机制和负责分泌的细胞信号将被研究。这些研究将阐明这些翻译装置的组成部分如何将蛋白质合成与信号转导途径联系起来。这些研究结果可为治疗细胞因子活性和血管生成起重要作用的人类疾病提供一种基础。

This project focuses on novel activities of two essential components of the translation apparatus in human cells. These components are aminoacyl tRNA synthetases. In their canonical role, aminoacyl tRNA synthetases catalyze aminoacylation of transfer RNAs in the first step of protein synthesis, and thereby establish the rules of the genetic code. Each of the 20 amino acids that make up proteins has a separate, distinct aminoacyl tRNA synthetase. In recent work we reported that one specific tRNA synthetase-for the amino acid tyrosine-could be split into two distinct cytokines. While the full-length protein is inactive, the two fragments are potent cytokines with distinct biological activities. The protein is secreted during apoptosis in cell culture and then can be cleaved by a protease such as leukocyte elastase. In further unpublished work, we found that the aforementioned fragments of this synthetase, and fragments of its close homolog that acts on the amino acid tryptophan, are active in angiogenesis or angiostasis. (Proteolysis or alternative splicing produces fragments of the latter enzyme.) The purpose of this project is to expand upon and further validate the initial observations of the activities of these fragments in angiogenesis or angiostasis, using several different assays for angiogenesis in vivo. The receptors involved in the angiogenic pathways, the specific motifs within the proteins responsible for the activities, the mechanism of secretion, and the cell signals responsible for secretion will investigated. These investigation will clarify how these components of the translation apparatus link protein synthesis to signal transduction pathways. The results of these studies can provide one kind of foundation for treating human diseases where cytokine activities and angiogenesis play an important role.