Matsuda S, Kawamura-Tsuzuku J, Ohsugi M, Yoshida M, Emi M, Nakamura Y, Onda M, Yoshida Y, Nishiyama A, Yamamoto T
Department of Oncology, University of Tokyo, Japan.
Oncogene. 1996 Feb 15;12(4):705-13.
We have molecularly cloned a cDNA for a novel protein termed Tob (Transducer of ErbB-2) that interacts with the c-erbB-2 gene product p185erbB2. Nucleotide sequencing reveals that the Tob protein is a 45 kDa protein that does not contain either SH2 (Src Homology 2) or SH3 domain but is homologous to the previously characterized anti-proliferative gene product BTG-1 at its amino-terminal half. The carboxyl-terminal half of Tob is characterized by the presence of a sequence rich in proline and glutamine and shows no homology to known proteins. Like BTG-1, exogenously expressed Tob is able to suppress growth of NIH3T3 cells, but the growth suppression is hampered by the presence of kinase-active p185erbB2. By using the GST-Tob protein that contains either full length or amino-terminal half of Tob, we show that the carboxyl-terminal half of Tob is relevant to its interaction with p185erbB2. Furthermore, we could co-immunoprecipitate the Tob protein with anti-ErbB-2 antibody, and reciprocally the p185erbB2 with anti-Tob antibodies. These data suggest that p185erbB2 negatively regulates the Tob-mediated anti-proliferative pathway through its interaction with Tob, resulting possibly in growth stimulation by p185erbB2. Finally, expression of the Tob mRNA is observed in various cell types and is not correlated with expression of c-erbB-2, suggesting that other receptor-type protein-tyrosine kinases are also involved in the Tob-mediated regulation of cell growth.
我们通过分子克隆技术获得了一种名为Tob（ErbB-2转导蛋白）的新型蛋白质的cDNA，该蛋白可与c-erbB-2基因产物p185erbB2相互作用。核苷酸测序显示，Tob蛋白是一种45 kDa的蛋白质，既不包含SH2（Src同源结构域2）也不包含SH3结构域，但在其氨基末端一半与先前鉴定的抗增殖基因产物BTG-1同源。Tob的羧基末端一半的特征是存在富含脯氨酸和谷氨酰胺的序列，与已知蛋白质无同源性。与BTG-1一样，外源性表达的Tob能够抑制NIH3T3细胞的生长，但激酶活性的p185erbB2的存在会阻碍这种生长抑制作用。通过使用包含Tob全长或氨基末端一半的GST-Tob蛋白，我们发现Tob的羧基末端一半与其与p185erbB2的相互作用有关。此外，我们可以用抗ErbB-2抗体共免疫沉淀Tob蛋白，反之亦然，用抗Tob抗体共免疫沉淀p185erbB2。这些数据表明，p185erbB2通过与Tob相互作用负向调节Tob介导的抗增殖途径，可能导致p185erbB2刺激细胞生长。最后，在各种细胞类型中均观察到Tob mRNA的表达，且与c-erbB-2的表达无关，这表明其他受体型蛋白酪氨酸激酶也参与了Tob介导的细胞生长调节。
