Regulation of tyrosine kinase signaling through interaction with membrane lipids

 描述(申请人提供)：蛋白酪氨酸激酶6(PTK6)是一种细胞内酪氨酸激酶，含有SH3和SH2结构域，但缺乏促进膜定位的SH4结构域。缺乏膜靶向有利于其在细胞内定位和接触底物的灵活性。在分化的前列腺上皮细胞中，PTK6主要存在于细胞核中。然而，活化的PTK6在前列腺癌中与细胞膜相关，其高表达与前列腺癌的转移和预后密切相关。我们发现，膜相关的PTK6促进细胞转化、上皮间充质转化和肿瘤细胞转移，而核PTK6抑制生长。我们设计了一个合作方案来解决这个问题，“PTK6是如何被招募到促进肿瘤发生的质膜上的？”我们的初步数据表明，PTK6在血浆中直接与富含磷酸盐的脂类结合，包括磷脂酰肌醇-(3，4，5)-三磷酸(PIP3) 薄膜。在癌症中，由于PI3K的激活和/或肿瘤抑制因子脂质磷酸酶PTEN的突变，PIP3的产生增加是常见的。我们假设富含磷酸盐的脂类，如PIP3，调节PTK6在质膜上的募集和激活，从而推动肿瘤的发生和转移。由细胞生物学家Tyner博士和结构生物化学家Gaponenko博士提出的高度协同的研究利用一系列生化、生物物理、分子、遗传学和细胞生物学方法：(I)研究PTK6脂类结合；(Ii)确定PTK6中脂类结合所需的结构域；(Iii)确定PI3K/PTEN/PIP3对前列腺癌细胞膜上PTK6激活的贡献；以及(Iv)研究PTK6膜结合在前列腺癌发生中的作用。这项研究的结果将确定一种新的细胞内酪氨酸激酶膜靶向和激活机制，并可能确定抑制肿瘤中PTK6的新策略。此外，PTK6细胞内定位或表达的改变可能为前列腺癌的分期提供一个独特的标志物。

 DESCRIPTION (provided by applicant): Protein tyrosine kinase 6 (PTK6) is an intracellular tyrosine kinase that contains SH3 and SH2 domains, but lacks an SH4 domain that promotes membrane localization. Lack of membrane targeting facilitates flexibility in its intracellular localization and access to substrates. In differentiated prostate epithelial cells, PTK6 is primariy found in the nucleus. However, active PTK6 associates with the plasma membrane in prostate cancer, and its increased expression is correlated with metastasis and poor survival. We found that membrane-associated PTK6 promotes cell transformation, the epithelial mesenchymal transition, and tumor cell metastasis, while nuclear PTK6 inhibits growth. We designed a collaborative proposal to address the question, "How is PTK6 recruited to the plasma membrane where it promotes tumorigenesis?" Our preliminary data suggest PTK6 directly binds phosphate-rich lipids, including phosphatidylinositol-(3, 4, 5)-trisphosphate (PIP3), at the plasma membrane. Increased production of PIP3 is commonly observed in cancer due to activation of PI3K and/or mutation of the tumor suppressor lipid phosphatase PTEN. We hypothesize that phosphate-rich lipids, such as PIP3 regulate the recruitment and activation of PTK6 at the plasma membrane to drive tumorigenesis and metastases. Highly synergistic studies proposed by Dr. Tyner, a cell biologist, and Dr. Gaponenko, a structural biochemist, use an array of biochemical, biophysical, molecular, genetic and cell biology approaches to: (i) Investigate PTK6 lipid binding; (ii) Identify domains in PTK6 required for lipid binding; (iii) Determine contributions of PI3K/PTEN/PIP3 to activation of PTK6 at the membrane in prostate cancer cells; and (iv) Examine contributions of PTK6 membrane binding to prostate tumorigenesis in mice with prostate specific deletion of the gene encoding the tumor suppressor PTEN. The results of this research will define a novel mechanism for intracellular tyrosine kinase membrane targeting and activation, and could identify novel strategies to inhibit PTK6 in cancer. In additio, alterations in PTK6 intracellular localization or expression may provide a unique marker for staging prostate cancers.