Regulation of PTEN Activity in Cancer Cells

描述(申请人提供)：正常细胞和癌细胞中PTEN活性和转位的调节。PTEN是新近发现的一种肿瘤抑制基因，在胶质母细胞瘤、前列腺癌、子宫癌、膀胱癌、乳腺癌和恶性黑色素瘤中均有缺失/突变。PTEN使磷脂酰肌醇(PDTLNS)-3-磷酸的3位去磷酸化，从而阻止PtDLNS-3-KEK激活Akt。PTEN还使粘着斑激酶(P125FAK)和Shc去磷酸化，Shc是一种SH2-磷酸酪氨酸结合的适配蛋白，将酪氨酸激酶与RAS信号和MAP激酶途径联系起来。PTEN在其C末端含有一个C2脂结合结构域，负责其与质膜内叶的磷脂酰胆碱以不依赖于钙离子的方式结合。我们最近发现，一个小的氧化还原蛋白硫氧还蛋白直接与PTEN的C2结构域结合，从而能够负性调节PTEN的脂质活性。硫氧还蛋白与PTEN的Cys212结合形成稳定的复合体，该复合体可以氧化还原依赖的方式进行调节。此外，向细胞中添加硒可以提高硫氧还蛋白还原酶的活性，从而能够恢复PTEN的活性。因此，我们研究的假设是：1)PTEN的活性受一个小的氧化还原蛋白的变构调节，并间接地受到硒的调节；2)PTEN的活性可以通过其C2结构域间接调节。我们研究的目的是为了更好地理解C2结构域在PTEN移位中的作用，以及通过它与其他蛋白质的相互作用来调节PTEN的活性。

DESCRIPTION (provided by applicant): Regulation of PTEN activity and translocation in normal and cancer cells. PTEN (phosphatase and tensin homolog deleted on chromosome ten) is a recently identified tumor suppressor, which is deleted/mutated in human tumors including glioblastomas, carcinomas of the prostate, uterus, bladder and breast and malignant melanomas. PTEN dephosphorylates the 3-position of phosphatidylinositol (Pdtlns)-3-phosphates, thus, preventing activation of Akt by Ptdlns-3-kinase. PTEN also dephosphorylates focal adhesion kinase (p125FAK) and Shc, a SH2-phosphotyrosine-binding adapter protein that links tyrosine kinases to Ras signaling and the MAP kinase pathway. PTEN contains a C2 lipid binding domain at its C-terminal end, which is responsible for its' binding to phosphatidylcholine at the inner leaflet of the plasma membrane in a Ca2+-independent manner. It has been suggested that this domain may influence the activity of the protein, but no clear-cut role for the C2 domain of PTEN has been proposed.We have recently found that a small redox protein, thioredoxin, binds directly to the C2 domain of PTEN and thereby is able to negatively regulate the lipid activity of PTEN. Thioredoxin binds to the Cys212 of PTEN forming a stable complex, which can be regulated in a redox dependent manner. Moreover, the addition of selenium to cells, which is know to increase thioredoxin reductase activity, is able to restore PTEN activity.Hence, the hypotheses upon which our studies are based are that 1) PTEN activity is allosterically regulated by a small redox protein and indirectly by selenium and that 2) PTEN activity can be regulated indirectly by its C2 domain. The objectives of our proposed studies are directed towards a better understanding of the role of the C2 domain in the translocation of PTEN and in the regulation of the activity of PTEN via its interaction with other proteins.