Regulation of PTEN Activity in Cancer Cells

描述（由申请人提供）：正常细胞和癌细胞中PTEN活性和易位的调节。PTEN（10号染色体上缺失的磷酸酶和紧张素同源物）是最近发现的一种肿瘤抑制因子，在人类肿瘤中缺失/突变，包括胶质母细胞瘤、前列腺癌、子宫癌、膀胱癌、乳腺癌和恶性黑色素瘤。PTEN使磷脂酰肌醇(Pdtlns)-3-磷酸的3位去磷酸化，从而阻止pttlns -3-激酶活化Akt。PTEN还能使局灶黏附激酶（p125FAK）和Shc去磷酸化，Shc是一种将酪氨酸激酶与Ras信号和MAP激酶途径连接起来的sh2 -磷酸酪氨酸结合适配器蛋白。PTEN在其c端含有一个C2脂质结合域，负责以Ca2+不依赖的方式与质膜内小叶的磷脂酰胆碱结合。有人认为该结构域可能影响蛋白的活性，但PTEN的C2结构域没有明确的作用。我们最近发现一个小的氧化还原蛋白，硫氧还蛋白，直接结合到PTEN的C2结构域，从而能够负向调节PTEN的脂质活性。硫氧还蛋白与PTEN的Cys212结合形成稳定的复合物，可以通过氧化还原依赖的方式进行调节。此外，在细胞中添加硒，已知可以增加硫氧还蛋白还原酶的活性，能够恢复PTEN的活性。因此，我们的研究基于以下假设：1)PTEN活性受一个小氧化还原蛋白的变构调节，并间接受硒的调节；2)PTEN活性可由其C2结构域间接调节。我们提出的研究目标是为了更好地理解C2结构域在PTEN易位中的作用，以及通过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.