Fei Z L, D'Ambrosio C, Li S, Surmacz E, Baserga R
Jefferson Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Mol Cell Biol. 1995 Aug;15(8):4232-39. doi: 10.1128/MCB.15.8.4232.
Mouse embryo cells expressing a wild-type number of insulin-like growth factor I receptors (IGF-IR) (W cells) can be transformed either by simian virus 40 large T antigen (SV40 T) or by overexpressed insulin receptor substrate 1 (IRS-1), singly transfected. Neither SV40 T antigen nor IRS-1, individually, can transform mouse embryo cells with a targeted disruption of the IGF-IR genes (R- cells). However, cotransfection of SV40 T antigen and IRS-1 does transform R- cells. In this study, using different antibodies and different cell lines, we found that SV40 T antigen and IRS-1 are coprecipitated from cell lysates in a specific fashion, regardless of whether the lysates are immunoprecipitated with an antibody to SV40 T antigen or an antibody to IRS-1. The same antibody to SV40 T antigen, however, fails to coprecipitate another substrate of IGF-IR, the transforming protein Shc, and two other signal-transducing molecules, Grb2 and Sos. Finally, an SV40 T antigen lacking the amino-terminal 250 amino acids fails to coprecipitate IRS-1 and also fails to transform R- cells overexpressing mouse IRS-1. These experiments indicate that IRS-1 associates with SV40 T antigen and that this association plays a critical role in the combined ability of these proteins to transform R- cells. This finding is discussed in light of the crucial role of the IGF-IR in the establishment and maintenance of the transformed phenotype.
表达野生型数量胰岛素样生长因子I受体（IGF-IR）的小鼠胚胎细胞（W细胞），可通过单独转染猿猴病毒40大T抗原（SV40 T）或过表达的胰岛素受体底物1（IRS-1）实现转化。单独的SV40 T抗原和IRS-1均无法转化IGF-IR基因靶向破坏的小鼠胚胎细胞（R细胞）。然而，SV40 T抗原与IRS-1共转染确实能使R细胞发生转化。在本研究中，使用不同抗体和不同细胞系，我们发现无论细胞裂解物是用抗SV40 T抗原抗体还是抗IRS-1抗体进行免疫沉淀，SV40 T抗原和IRS-1都以特定方式从细胞裂解物中共沉淀。然而，相同的抗SV40 T抗原抗体无法共沉淀IGF-IR的另一种底物、转化蛋白Shc以及另外两种信号转导分子Grb2和Sos。最后，缺失氨基末端250个氨基酸的SV40 T抗原无法与IRS-1共沉淀，也无法转化过表达小鼠IRS-1的R细胞。这些实验表明IRS-1与SV40 T抗原相关联，且这种关联在这些蛋白质联合转化R细胞的能力中起关键作用。鉴于IGF-IR在转化表型的建立和维持中的关键作用，对这一发现进行了讨论。
