Mitchell E J, O'Connor-McCourt M D
National Research Council of Canada, Biotechnology Research Institute, Montreal, Quebec.
Biochemistry. 1991 Apr 30;30(17):4350-6. doi: 10.1021/bi00231a034.
Affinity-labeling techniques have been used to identify three types of high-affinity receptors for transforming growth factor beta (TGF-beta) on the surface of many cells in culture. Here we demonstrate that membrane preparations from tissue sources may also be used as an alternative system for studying the binding properties of TGF-beta receptors. Using a chemical cross-linking technique with 125I-TGF-beta 1 and 125I-TGF-beta 2 and bis(sulfosuccinimidyl)suberate (BS3), we have identified and characterized two high-affinity binding components in membrane preparations derived from human term placenta. The larger species, which migrates as a diffuse band of molecular mass 250-350 kDa on sodium dodecyl sulfate-polyacrylamide electrophoresis gels, is characteristic of the TGF-beta receptor type III, a proteoglycan containing glycosaminoglycan (GAG) chains of chondroitin and heparan sulfate. The smaller species of molecular mass 140 kDa was identified as the core glycoprotein of this type III receptor by using the techniques of enzymatic deglycosylation and peptide mapping. Competition experiments, using 125I-TGF-beta 1 or 125I-TGF-beta 2 and varying amounts of competing unlabeled TGF-beta 1 or TGF-beta 2, revealed that both the placental type III proteoglycan and its core glycoprotein belong to a novel class of type III receptors that exhibit a greater affinity for TGF-beta 2 than for TGF-beta 1. This preferential binding of TGF-beta 2 to placental type III receptors suggests differential roles for TGF-beta 2 and TGF-beta 1 in placental function.
亲和标记技术已被用于识别培养的许多细胞表面上的三种转化生长因子β（TGF-β）高亲和力受体。在这里，我们证明来自组织来源的膜制剂也可作为研究TGF-β受体结合特性的替代系统。使用化学交联技术，结合125I-TGF-β1、125I-TGF-β2和双（磺基琥珀酰亚胺基）辛二酸酯（BS3），我们已在源自人足月胎盘的膜制剂中鉴定并表征了两种高亲和力结合成分。较大的成分在十二烷基硫酸钠-聚丙烯酰胺电泳凝胶上迁移为分子量250-350 kDa的弥散条带，是TGF-β受体III型的特征，这是一种含有硫酸软骨素和硫酸乙酰肝素糖胺聚糖（GAG）链的蛋白聚糖。通过使用酶促去糖基化和肽图谱技术将分子量为140 kDa的较小成分鉴定为该III型受体的核心糖蛋白。使用125I-TGF-β1或125I-TGF-β2以及不同量的竞争性未标记TGF-β1或TGF-β2进行的竞争实验表明，胎盘III型蛋白聚糖及其核心糖蛋白均属于一类新型的III型受体，它们对TGF-β2的亲和力比对TGF-β1的亲和力更高。TGF-β2与胎盘III型受体的这种优先结合表明TGF-β2和TGF-β1在胎盘功能中具有不同的作用。
