Wang Jiz-Yuh, Yang Chi-Hwa, Yeh Chi-Ling, Lin Chia-Hua, Chen Yi-Rong
Division of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan Town, Taiwan.
J Neurochem. 2008 Dec;107(6):1544-55. doi: 10.1111/j.1471-4159.2008.05714.x. Epub 2008 Nov 11.
Neuroendocrine-associated phosphatase (NEAP), an atypical dual specificity phosphatase is preferentially expressed in neuroendocrine cells. In this study we found that NEAP, but not NEAP-(C152S) mutant, evidently reduced epidermal growth factor (EGF) receptor (EGFR) downstream signaling, and impaired cell growth in response to EGF stimulation in PC12 cells. These phenomena were associated with NEAP-mediated down-regulation of EGFR mRNA and protein. NEAP had no significant effect on ErbB2/3 expression and phosphorylation levels in response to heregulin, indicating that the negative effect of NEAP on EGFR was selective. We showed that NEAP suppressed EGFR expression via decreasing the EGFR promoter activity and this was mediated through down-regulations of the Akt pathway and Wilms' tumor gene product (WT1). Consistent with these results, expression of WT1 reversed the suppressive effect of NEAP on EGFR promoter activity. Additionally, NEAP knockdown by RNA interference enhanced EGFR protein expression and nerve growth factor-induced differentiation, and an EGFR-specific inhibitor could reverse the later event. Taken together, our study indicated that NEAP modulates PC12 differentiation via suppression of EGFR expression and signaling.
神经内分泌相关磷酸酶（NEAP）是一种非典型双特异性磷酸酶，在神经内分泌细胞中优先表达。在本研究中，我们发现NEAP而非NEAP-（C152S）突变体显著降低了表皮生长因子（EGF）受体（EGFR）的下游信号传导，并损害了PC12细胞中对EGF刺激的细胞生长反应。这些现象与NEAP介导的EGFR mRNA和蛋白的下调有关。NEAP对ErbB2/3的表达以及对这里配体的磷酸化水平没有显著影响，表明NEAP对EGFR的负面影响具有选择性。我们表明NEAP通过降低EGFR启动子活性来抑制EGFR表达，这是通过下调Akt途径和威尔姆斯瘤基因产物（WT1）介导的。与这些结果一致，WT1的表达逆转了NEAP对EGFR启动子活性的抑制作用。此外，RNA干扰敲低NEAP增强了EGFR蛋白表达和神经生长因子诱导的分化，并且一种EGFR特异性抑制剂可以逆转后一事件。综上所述，我们的研究表明NEAP通过抑制EGFR表达和信号传导来调节PC12分化。
