Graves D T, Antoniades H N
Department of Periodontics, University of Texas Health Science Center, San Antonio 78284.
J Cell Physiol. 1988 Nov;137(2):263-71. doi: 10.1002/jcp.1041370208.
We previously demonstrated that a high-molecular-weight glycoprotein could be immunoprecipitated from metabolically labeled U-2 OS cells with platelet-derived growth factor (PDGF) antiserum and that it appears to be derived from a different precursor than is the 30 kD PDGF-like mitogen produced by these cells. These findings were unexpected, since the molecular weight of this glycoprotein is too large to be encoded by the PDGF structural genes. From experiments with metabolically labeled U-2 OS human osteosarcoma, fibroblasts, and NRK cells, we report here that a 185 kD protein immunoprecipitated with PDGF antiserum has the following characteristics. 1) It is a PDGF binding protein that is unrelated to alpha 2-macroglobulin. 2) It is phosphorylated in response to PDGF stimulation. 3) It is immunoprecipitated by phosphotyrosine antibodies. 4) It is not a substrate of epidermal growth factor-induced tyrosine kinase activity. These studies indicate that high-molecular-weight proteins immunoprecipitated by antiserum to PDGF represent a complex between PDGF and a binding protein capable of being phosphorylated by a PDGF-induced tyrosine kinase. These characteristics are identical to those of the PDGF receptor.
我们之前证明，一种高分子量糖蛋白可通过血小板衍生生长因子（PDGF）抗血清从经代谢标记的U-2 OS细胞中免疫沉淀出来，并且它似乎来源于与这些细胞产生的30 kD PDGF样促分裂原不同的前体。这些发现出乎意料，因为这种糖蛋白的分子量太大，无法由PDGF结构基因编码。通过对经代谢标记的U-2 OS人骨肉瘤细胞、成纤维细胞和NRK细胞进行的实验，我们在此报告，用PDGF抗血清免疫沉淀出的一种185 kD蛋白质具有以下特征。1）它是一种与α2-巨球蛋白无关的PDGF结合蛋白。2）它在PDGF刺激下发生磷酸化。3）它可被磷酸酪氨酸抗体免疫沉淀。4）它不是表皮生长因子诱导的酪氨酸激酶活性的底物。这些研究表明，用PDGF抗血清免疫沉淀出的高分子量蛋白质代表了PDGF与一种能够被PDGF诱导的酪氨酸激酶磷酸化的结合蛋白之间的复合物。这些特征与PDGF受体的特征相同。
