Structural Studies of the Pseudokinase Domain of Jak2.

描述（由申请方提供）：Janus激酶（Jaks）是非受体蛋白酪氨酸激酶家族的成员，是免疫系统细胞和造血细胞中信号传导途径的关键组分。JAK与细胞因子受体的胞质结构域相关，并且在酪氨酸介导的受体二聚化后，在酪氨酸残基上进行反式自磷酸化，这刺激其酪氨酸激酶活性。激活的Jaks磷酸化STAT（信号转导和转录激活因子），其易位到细胞核并充当转录激活因子。Jak家族有四个哺乳动物成员（Jak 1 -3和Tyk 2），它们具有四个共同的结构域：N-末端FERM结构域、SH 2样结构域、假激酶结构域和酪氨酸激酶结构域。广泛的生化数据，以及导致骨髓增生性疾病/癌症的功能获得性突变，暗示了Jaks的假激酶结构域对于维持低基础水平的酪氨酸激酶活性至关重要。该提案的目标是了解假激酶结构域负调控Jak 2酪氨酸激酶活性的结构/分子机制。为了实现这一目标，将采用X射线晶体学来确定假激酶结构域和串联的假激酶和酪氨酸激酶结构域的三维结构。 公共卫生相关性：Jaks中的功能获得性突变，主要在假激酶结构域中，是人类各种骨髓增生性疾病/癌症的病因，如真性红细胞增多症、原发性骨髓纤维化和急性淋巴细胞白血病。该提案的目标是通过X射线晶体学确定Jak 2假激酶和酪氨酸激酶结构域的三维结构，以了解这些骨髓增生性疾病的分子基础，并促进用于治疗干预的新型小分子抑制剂的开发。

DESCRIPTION (provided by applicant): Janus kinases (Jaks), members of the non-receptor protein tyrosine kinase family, are key components of signaling pathways in cells of the immune system and in hematopoietic cells. Jaks are associated with the cytoplasmic domains of cytokine receptors and, upon cytokine-mediated receptor dimerization, undergo trans- autophosphorylation on tyrosine residues, which stimulates their tyrosine kinase activity. Activated Jaks phosphorylate STATs (signal transducers and activators of transcription), which translocate to the nucleus and serve as transcriptional activators. There are four mammalian members of the Jak family (Jak1-3 and Tyk2) which possess four domains in common: an N-terminal FERM domain, an SH2-like domain, a pseudokinase domain, and a tyrosine kinase domain. Extensive biochemical data, as well as gain-of-function mutations that cause myeloproliferative diseases/cancers, have implicated the pseudokinase domain of Jaks as crucial for maintaining a low basal level of tyrosine kinase activity. The goal of this proposal is to understand the structural/molecular mechanisms by which the pseudokinase domain negatively regulates the tyrosine kinase activity of Jak2. To achieve this goal, x-ray crystallography will be employed to determine the three-dimensional structures of the pseudokinase domain and the tandem pseudokinase and tyrosine kinase domains. PUBLIC HEALTH RELEVANCE: Gain-of-function mutations in Jaks, predominantly in the pseudokinase domain, are causative for various myeloproliferative diseases/cancers in humans, such as polycythemia vera, primary myelofibrosis, and acute lymphoblastic leukemia. The goal of this proposal is to determine by x-ray crystallography the three- dimensional structure of the Jak2 pseudokinase and tyrosine kinase domains, to understand the molecular bases for these myeloproliferative diseases and to facilitate the development of novel small-molecule inhibitors for therapeutic intervention.