Dey B R, Spence S L, Nissley P, Furlanetto R W
Metabolism Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 1998 Sep 11;273(37):24095-101. doi: 10.1074/jbc.273.37.24095.
SOCS (suppressor of cytokine signaling) proteins have been shown to be negative regulators of cytokine receptor signaling via the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway. We have cloned a member of this family (hSOCS-2) by utilizing the insulin-like growth factor I receptor (IGF-IR) cytoplasmic domain as bait in a yeast two-hybrid screen of a human fetal brain library. The hSOCS-2 protein interacted strongly with the activated IGF-IR and not with a kinase negative mutant receptor in the two-hybrid assay. Mutation of receptor tyrosines 950, 1250, 1251, and 1316 to phenylalanine or deletion of the COOH-terminal 93 amino acids did not result in decreased interaction of the receptor with hSOCS-2 protein. hSOCS-1 protein also interacted strongly with IGF-IR in the two-hybrid assay. Glutathione S-transferase-hSOCS-2 associated with activated IGF-IR in lysates of mouse fibroblasts overexpressing IGF-IR. Human embryonic kidney cells (293) were transiently transfected with vectors containing IGF-IR and FLAG epitope-tagged hSOCS-2. After IGF-I stimulation, activated IGF-IR was found in anti-FLAG immunoprecipitates and, conversely, FLAG-hSOCS-2 was found in anti IGF-IR immunoprecipitates. Thus, hSOCS-2 interacted with IGF-IR both in vitro and in vivo. HSOCS-2 mRNA was expressed in many human fetal and adult tissues with particularly high abundance in fetal kidney and adult heart, skeletal muscle, pancreas, and liver. These results raise the possibility that SOCS proteins may also play a regulatory role in IGF-I receptor signaling.
细胞因子信号转导抑制因子（SOCS）蛋白已被证明是通过Janus激酶（JAK）/信号转导子和转录激活子（STAT）途径对细胞因子受体信号进行负调控的因子。我们利用胰岛素样生长因子I受体（IGF-IR）的胞质结构域作为诱饵，在人胎脑文库的酵母双杂交筛选中克隆了该家族的一个成员（hSOCS-2）。在双杂交实验中，hSOCS-2蛋白与活化的IGF-IR强烈相互作用，而不与激酶阴性突变受体相互作用。将受体酪氨酸950、1250、1251和1316突变为苯丙氨酸或缺失COOH末端的93个氨基酸，并不会导致受体与hSOCS-2蛋白的相互作用减少。在双杂交实验中，hSOCS-1蛋白也与IGF-IR强烈相互作用。在过表达IGF-IR的小鼠成纤维细胞裂解物中，谷胱甘肽S-转移酶-hSOCS-2与活化的IGF-IR相关联。用人胚胎肾细胞（293）瞬时转染含有IGF-IR和FLAG表位标签的hSOCS-2的载体。IGF-I刺激后，在抗FLAG免疫沉淀中发现活化的IGF-IR，相反，在抗IGF-IR免疫沉淀中发现FLAG-hSOCS-2。因此，hSOCS-2在体外和体内均与IGF-IR相互作用。HSOCS-2 mRNA在许多人胎儿和成人组织中表达，在胎儿肾脏和成人心脏、骨骼肌、胰腺和肝脏中表达量特别高。这些结果提示SOCS蛋白可能在IGF-I受体信号传导中也发挥调节作用。
