Functional analysis of the protein phosphatase activity of PTEN.
Functional analysis of the protein phosphatase activity of PTEN.
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DOI：
10.1042/bj20120098
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发表时间：
2012-06-15
期刊：
影响因子：
--
通讯作者：
Tonks NK
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文献类型：
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作者：
Zhang XC;Piccini A;Myers MP;Van Aelst L;Tonks NK
在体外，肿瘤抑制因子PTEN（10号染色体上缺失的磷酸酶和张力蛋白同源物）对蛋白质和脂质底物都显示出固有的磷酸酶活性。在体内，脂质磷酸酶活性的PTEN，通过它去磷酸化的3位在肌醇的磷脂酰肌醇衍生物的糖，是重要的肿瘤抑制功能，然而，其蛋白磷酸酶活性的意义仍然不清楚。使用双光子激光扫描显微镜和生物射弹基因递送GFP（绿色荧光蛋白）标记的结构到器官型海马切片培养，我们已经开发了一种测定活组织中的PTEN功能。使用这种生物测定，我们已经证明，野生型PTEN的过度表达导致神经元中的棘密度降低。此外，这是蛋白磷酸酶活性，而不是脂质磷酸酶活性，PTEN是必不可少的这种效果。PTEN降低神经元棘密度的能力取决于其C-末端片段中丝氨酸和苏氨酸残基的磷酸化状态和C-末端PDZ结合基序的完整性。本研究揭示了这一重要的肿瘤抑制因子的功能的一个新方面，并表明，除了去磷酸化的3位磷脂酰肌醇磷脂，关键的蛋白质底物的PTEN可能是PTEN本身。
In vitro, the tumour suppressor PTEN (phosphatase and tensin homologue deleted on chromosome 10) displays intrinsic phosphatase activity towards both protein and lipid substrates. In vivo, the lipid phosphatase activity of PTEN, through which it dephosphorylates the 3 position in the inositol sugar of phosphatidylinositol derivatives, is important for its tumour suppressor function; however, the significance of its protein phosphatase activity remains unclear. Using two-photon laser-scanning microscopy and biolistic gene delivery of GFP (green fluorescent protein)-tagged constructs into organotypic hippocampal slice cultures, we have developed an assay of PTEN function in living tissue. Using this bioassay, we have demonstrated that overexpression of wild-type PTEN led to a decrease in spine density in neurons. Furthermore, it was the protein phosphatase activity, but not the lipid phosphatase activity, of PTEN that was essential for this effect. The ability of PTEN to decrease neuronal spine density depended upon the phosphorylation status of serine and threonine residues in its C-terminal segment and the integrity of the C-terminal PDZ-binding motif. The present study reveals a new aspect of the function of this important tumour suppressor and suggest that, in addition to dephosphorylating the 3 position in phosphatidylinositol phospholipids, the critical protein substrate of PTEN may be PTEN itself.