Mori S, Heldin C H, Claesson-Welsh L
Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden.
J Biol Chem. 1992 Mar 25;267(9):6429-34.
We have analyzed the nature of ligand-induced shift to higher molecular weight forms of the beta-receptor for platelet-derived growth factor expressed in porcine aortic endothelial cells. The modification of the beta-receptor was found to be due to polyubiquitination, as judged by immunoblotting using an anti-ubiquitin antiserum. A mutant beta-receptor made kinase negative by a point mutation (K634A mutant) did not undergo ubiquitination in response to ligand stimulation. A mutant in which carboxyl-terminal 98 amino acids were deleted (CT98 mutant) and which retained kinase activity was likewise not ubiquitinated. These data suggest that the kinase activity, as well as the carboxyl-terminal 98 amino acids, is required for ubiquitination of the beta-receptor. Ligand-induced degradation of the receptor-bound ligand, as well as of the receptor itself, was partially impaired in the CT98-receptor-expressing cells, suggesting that the ubiquitination is of importance for efficient degradation of the ligand-receptor complex.
我们分析了在猪主动脉内皮细胞中表达的血小板衍生生长因子β受体向更高分子量形式的配体诱导转变的性质。通过使用抗泛素抗血清进行免疫印迹判断，发现β受体的修饰是由于多聚泛素化所致。通过点突变使激酶失活的突变型β受体（K634A突变体）在配体刺激下不会发生泛素化。缺失羧基末端98个氨基酸且保留激酶活性的突变体（CT98突变体）同样不会发生泛素化。这些数据表明，β受体的泛素化需要激酶活性以及羧基末端98个氨基酸。在表达CT98受体的细胞中，配体诱导的受体结合配体以及受体自身的降解部分受损，这表明泛素化对于配体-受体复合物的有效降解很重要。
