Zarich Natasha, Oliva José Luis, Martínez Natalia, Jorge Rocío, Ballester Alicia, Gutiérrez-Eisman Silvia, García-Vargas Susana, Rojas José M
Unidad de Biología Celular, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain.
Mol Biol Cell. 2006 Aug;17(8):3591-7. doi: 10.1091/mbc.e05-12-1104. Epub 2006 Jun 7.
hSos1 is a Ras guanine-nucleotide exchange factor. It was suggested that the carboxyl-terminal region of hSos1 down-regulates hSos1 functionality and that the intrinsic guanine-nucleotide exchange activity of this protein may be different before and after stimulation of tyrosine kinase receptors. Using different myristoylated hSos1 full-length and carboxyl-terminal truncated mutants, we show that Grb2 function accounts not only for recruitment of hSos1 to the plasma membrane but also for modulation of hSos1 activity. Our results demonstrate that the first two canonical Grb2 binding sites, inside the carboxyl-terminal region of hSos1, are responsible for this regulation. Following different approaches, such as displacement of Grb2 from the hSos1-Grb2 complex or depletion of Grb2 levels by small interfering RNA, we found that the full-length Grb2 proteins mediate negative regulation of the intrinsic Ras guanine-nucleotide exchange activity of hSos1.
hSos1是一种Ras鸟嘌呤核苷酸交换因子。有人提出，hSos1的羧基末端区域会下调hSos1的功能，并且该蛋白的内在鸟嘌呤核苷酸交换活性在酪氨酸激酶受体受到刺激前后可能有所不同。我们使用不同的肉豆蔻酰化hSos1全长和羧基末端截短突变体，证明Grb2的功能不仅负责将hSos1募集到质膜，还负责调节hSos1的活性。我们的结果表明，hSos1羧基末端区域内的前两个典型Grb2结合位点负责这种调节。通过不同的方法，如将Grb2从hSos1-Grb2复合物中置换出来或通过小干扰RNA降低Grb2水平，我们发现全长Grb2蛋白介导对hSos1内在Ras鸟嘌呤核苷酸交换活性的负调节。
