Putative phosphatidylinositol 3-kinase (PI3K) binding motifs in ovine betaretrovirus Env proteins are not essential for rodent fibroblast transformation and PI3K/Akt activation
Putative phosphatidylinositol 3-kinase (PI3K) binding motifs in ovine betaretrovirus Env proteins are not essential for rodent fibroblast transformation and PI3K/Akt activation
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DOI：
10.1128/jvi.77.14.7924-7935.2003
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发表时间：
2003-07-01
影响因子：
5.4
通讯作者：
Miller, AD
中科院分区：
文献类型：
--
作者：
Liu, SL;Lerman, MI;Miller, AD
绵羊Jaagsiekte羊反转录病毒（JSRV）和地方性鼻肿瘤病毒（ENTV）是一种简单的β -逆转录病毒，可引起绵羊和山羊下呼吸道和上呼吸道上皮细胞肿瘤。这两种病毒的包膜（Env）糖蛋白都能转化啮齿动物和鸡成纤维细胞，表明它们在肿瘤发生中起重要作用。先前的研究发现，Env细胞质尾部的YXXM基序是酪氨酸磷酸化后磷脂酰肌醇3-激酶（PI3K）的假定对接位点，是啮齿动物细胞转化所必需的，但不是DF-1鸡成纤维细胞转化所必需的。本研究表明，YXXM基序中酪氨酸或蛋氨酸突变的JSRV和ENTV Env蛋白仍然可以转化啮齿动物成纤维细胞，尽管效率降低。Akt在JSRV或ENTV Env蛋白转化的细胞和酪氨酸突变蛋白转化的细胞中被激活。此外，PI3K特异性抑制剂LY294002在所有情况下都能抑制Akt的激活和细胞转化，表明Akt的激活和转化依赖于PI3K。然而，在转化的细胞中，我们没有检测到JSRV或ENTV Env蛋白的酪氨酸磷酸化或Env蛋白与PI3K之间的相互作用。我们没有发现在被JSRV或ENTV Env蛋白转化的细胞中有丝裂原活化的蛋白激酶活化的证据。我们得出结论，羊β -逆转录病毒Env蛋白通过间接激活PI3K/Akt通路转化啮齿动物成纤维细胞。
Jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV) are simple betaretroviruses that cause epithelial cell tumors in the lower and upper airways of sheep and goats. The envelope (Env) glycoproteins of both viruses can transform rodent and chicken fibroblasts, indicating that they play an essential role in oncogenesis. Previous studies found that a YXXM motif in the Env cytoplasmic tail, a putative docking site for phosphatidylinositol 3-kinase (PI3K) after tyrosine phosphorylation, was necessary for rodent cell transformation but was not required for transformation of DF-1 chicken fibroblasts. Here we show that JSRV and ENTV Env proteins with tyrosine or methionine mutations in the YXXM motif can still transform rodent fibroblasts, albeit with reduced efficiency. Akt was activated in cells transformed by JSRV or ENTV Env proteins and in cells transformed by the proteins with tyrosine mutations. Furthermore, the PI3K-specific inhibitor LY294002 could inhibit Akt activation and cell transformation in all cases, indicating that Akt activation and transformation is PI3K dependent. However, we could not detect tyrosine phosphorylation of JSRV or ENTV Env proteins or an interaction between the Env proteins and PI3K in the transformed cells. We found no evidence for mitogen-activated protein kinase activation in cells that were transformed by the JSRV or ENTV Env proteins. We conclude that ovine betaretrovirus Env proteins transform the rodent fibroblasts by indirectly activating the PI3K/Akt pathway.