Direct positive regulation of PTEN by the p85 subunit of phosphatidylinositol 3-kinase
Direct positive regulation of PTEN by the p85 subunit of phosphatidylinositol 3-kinase
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DOI：
10.1073/pnas.0908899107
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发表时间：
2010-03-23
影响因子：
11.1
通讯作者：
Anderson, Deborah H.
中科院分区：
文献类型：
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作者：
Chagpar, Ryaz B.;Links, Philip H.;Anderson, Deborah H.
磷脂酰肌醇3-激酶（PI 3 K）信号通路在许多人类疾病中失调，包括癌症、糖尿病、肥胖和自身免疫。PI 3 K由p110催化蛋白和p85 α调节蛋白组成，是p110-PI 3 K活性稳定和定位所需的。p110-PI 3 K酶产生关键信号脂质磷脂酰肌醇3，4，5-三磷酸，其被PI 3-磷酸酶PTEN去磷酸化。在这里，我们展示了p85 α调节蛋白的另一个功能：它直接结合并增强PTEN脂质磷酸酶活性。我们证明，异位表达FLAG标记的p85共免疫沉淀内源性PTEN的表皮生长因子依赖的方式。我们还显示了表皮生长因子依赖的免疫共沉淀的内源性p85和PTEN蛋白在HeLa细胞。因此，p85通过直接相互作用调节p110-PI 3 K和PTEN-磷酸酶。这一发现强调了在分析PI 3 K活性时需要谨慎，因为抗p85免疫沉淀可能含有p85：p110-PI 3 K和p85：PTEN-磷酸酶，因此可以测量净PI 3 K活性。我们鉴定了p85 α的N-末端SH 3-BH区域，其在较小的p55 α和p50 α亚型中不存在，作为介导PTEN结合和调节的区域。p85 δ SH 3-BH的细胞表达导致响应于生长因子刺激的pAkt水平的幅度和持续时间显著增加。p85结合和直接调节p110-PI 3 K和PTEN-PI 3-磷酸酶的能力使我们能够解释在PI 3 K或PTEN蛋白减少的小鼠中观察到的矛盾的胰岛素信号传导表型。这一发现将影响正在进行的使用靶向PI 3 K/PTEN/Akt通路的治疗剂的研究。
The phosphatidylinositol 3-kinase (PI3K) signaling pathway is deregulated in many human diseases including cancer, diabetes, obesity, and autoimmunity. PI3K consists of a p110 catalytic protein and a p85 alpha regulatory protein, required for the stabilization and localization of p110-PI3K activity. The p110-PI3K enzyme generates the key signaling lipid phosphatidylinositol 3,4,5-trisphosphate, which is dephosphorylated by the PI3-phosphatase PTEN. Here we show another function for the p85 alpha regulatory protein:it binds directly to and enhances PTEN lipid phosphatase activity. We demonstrate that ectopically expressed FLAG-tagged p85 coimmunoprecipitates endogenous PTEN in an epidermal growth factor dependent manner. We also show epidermal growth factor dependent coimmunoprecipitation of endogenous p85 and PTEN proteins in HeLa cells. Thus p85 regulates both p110-PI3K and PTEN-phosphatase enzymes through direct interaction. This finding underscores the need for caution in analyzing PI3K activity because anti-p85 immunoprecipitations may contain both p85:p110-PI3K and p85:PTEN-phosphatase enzymes and thus measure net PI3K activity. We identify the N-terminal SH3-BH region of p85 alpha, absent in the smaller p55 alpha and p50 alpha isoforms, as the region that mediates PTEN binding and regulation. Cellular expression of p85 Delta SH3-BH results in substantially increased magnitude and duration of pAkt levels in response to growth factor stimulation. The ability of p85 to bind and directly regulate both p110-PI3K and PTEN-PI3-phosphatase allows us to explain the paradoxical insulin signaling phenotypes observed in mice with reduced PI3K or PTEN proteins. This discovery will impact ongoing studies using therapeutics targeting the PI3K/PTEN/Akt pathway.