Relevance of Akt phosphorylation in cell transformation induced by Jaagsiekte sheep retrovirus.
Relevance of Akt phosphorylation in cell transformation induced by Jaagsiekte sheep retrovirus.
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DOI：
10.1016/s0042-6822(03)00205-8
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发表时间：
2003-07
期刊：
影响因子：
3.7
通讯作者：
G. Zavala;Carla D. Pretto;Y. Chow;Leeann Jones;A. Alberti;E. Grego;M. De las Heras;M. Palmarini
中科院分区：
文献类型：
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作者：
G. Zavala;Carla D. Pretto;Y. Chow;Leeann Jones;A. Alberti;E. Grego;M. De las Heras;M. Palmarini
JSRV包膜（Env）的表达足以转化永生化啮齿动物成纤维细胞。在JSRV Env的跨膜结构域的胞质尾部中的PI 3-K激酶（Y 590-X-X-M593）的推定对接位点是病毒诱导的细胞转化的主要决定因素。Akt在由JSRV Env转化的啮齿动物成纤维细胞中组成性磷酸化。然而，最近的数据表明，Y 590和M593不是JSRV Env诱导的永生化鸡成纤维细胞系DF-1转化所必需的。在本研究中，我们发现JSRV诱导的DF-1细胞转化是Akt非依赖性的。此外，表达JSRV Env的可复制禽类载体（RCASBP（A）+JE）也能够诱导原代鸡胚成纤维细胞（CEF）的转化。表达JSRV Env Y 590突变体的载体仍然能够诱导CEF细胞转化，但不如表达野生型Env的载体有效。在CEF细胞中，如在DF-1细胞中，只有野生型Env的表达诱导Akt的组成性磷酸化。因此，在鸡细胞中，在存在Y 590和Akt磷酸化的情况下，JSRV Env诱导的转化程度最大。我们解决了大鼠208 F细胞中Akt磷酸化的意义，并显示Akt确实被激活，并显示激酶活性。PI-3 K/Akt途径的抑制剂可重复地降低JSRV Env的转化效率。在体内，我们发现磷酸化Akt仅在由地方性鼻肿瘤病毒（ENTV）（一种JSRV相关的β-逆转录病毒）诱导的鼻肿瘤中。在肺腺癌绵羊肺肿瘤切片中未发现Akt磷酸化的证据。总的来说，这些结果表明PI-3 K/Akt通路的激活有助于JSRV诱导的细胞转化过程，但很可能不是体外和体内的主要决定因素。
Expression of the JSRV envelope (Env) is sufficient to transform immortalized rodent fibroblasts. A putative docking site for the PI3-K kinase (Y590-X-X-M593) in the cytoplasmic tail of the transmembrane domain of the JSRV Env is a major determinant of viral-induced cell transformation. Akt is constitutively phosphorylated in rodent fibroblasts transformed by the JSRV Env. However, recent data suggest that Y590 and M593 are not necessary for JSRV Env-induced transformation of the immortalized chicken fibroblasts cell line DF-1. In this study we found that JSRV-induced transformation of DF-1 cells is Akt-independent. In addition, a replication-competent avian vector expressing the JSRV Env (RCASBP(A)+JE) was also able to induce transformation of primary chicken embryo fibroblasts (CEF). Vectors expressing JSRV Env Y590 mutants were still able to induce CEF cells transformation but not as efficiently as the vectors expressing the wild-type Env. In CEF cells, as in DF-1 cells, only the expression of the wild-type Env induced constitutive phosphorylation of Akt. Thus, in chicken cells, the degree of transformation induced by the JSRV Env is maximum in the presence of Y590 and Akt phosphorylation. We addressed the significance of Akt phosphorylation in rat 208F cells transformed by the JSRV Env and showed that Akt is indeed activated and shows kinase activity. Inhibitors of the PI-3K/Akt pathway reproducibly decreased the transformation efficiency of the JSRV Env. In vivo, we found phosphorylated Akt only in nasal tumors induced by the enzootic nasal tumor virus (ENTV), a JSRV-related β-retrovirus. No evidence of Akt phosphorylation was found in lung tumor sections of sheep affected by pulmonary adenocarcinoma. As a whole, these results suggest that the activation of the PI-3K/Akt pathway contributes to the process of JSRV-induced cell transformation but most likely is not the primary determinant both in vitro and in vivo.