Tripathi R C, Borisuth N S, Kolli S P, Tripathi B J
Department of Ophthalmology and Visual Science, University of Chicago, Illinois 60637.
Invest Ophthalmol Vis Sci. 1993 Jan;34(1):260-3.
To quantitate the receptors for transforming growth factor (TGF)-beta 1 on trabecular cells in culture and to determine the relative affinities of TGF-beta 1 and TGF-beta 2 for these receptors.
We quantitated the receptors for TGF-beta 1 by Scatchard analysis of radioligand binding of 125I-TGF-beta 1 to cultured porcine trabecular cells. We established the relative affinities of TGF-beta 1 and TGF-beta 2 for the receptors by competitive binding of 125I-TGF-beta 1 with increasing concentrations of the unlabeled TGF-beta 1 or TGF-beta 2. We also investigated the binding of 125I-TGF-beta 1 after pre-treatment of trabecular cells with heparinase.
Trabecular cells expressed approximately 4,000 high-affinity receptors per cell for TGF-beta 1, with a dissociation constant (Kd) of 15.8 +/- 7.6 pmol/l. By varying the concentrations of the unlabeled growth factors, we determined that the relative affinities of TGF-beta 1 and TGF-beta 2 for the receptors were 16 pmol/l and 50 pmol/l, respectively. Heparinase treatment of the trabecular cells did not change the binding affinity of the receptor for 125I-TGF-beta 1.
Our findings show that trabecular cells express heparinase-insensitive TGF-beta receptors that have an approximately threefold greater affinity for TGF-beta 1 than for TGF-beta 2. Based on the present investigation, together with our previous data on the molecular weights of the binding sites, we conclude that trabecular cells do possess types II and III receptors but not type I receptors.
对培养的小梁细胞上转化生长因子（TGF）-β1的受体进行定量，并确定TGF-β1和TGF-β2对这些受体的相对亲和力。
我们通过对125I-TGF-β1与培养的猪小梁细胞进行放射性配体结合的Scatchard分析来定量TGF-β1的受体。我们通过125I-TGF-β1与浓度不断增加的未标记TGF-β1或TGF-β2的竞争性结合来确定TGF-β1和TGF-β2对受体的相对亲和力。我们还研究了用肝素酶预处理小梁细胞后125I-TGF-β1的结合情况。
小梁细胞每个细胞表达约4000个TGF-β1的高亲和力受体，解离常数（Kd）为15.8±7.6 pmol/L。通过改变未标记生长因子的浓度，我们确定TGF-β1和TGF-β2对受体的相对亲和力分别为16 pmol/L和50 pmol/L。用肝素酶处理小梁细胞并未改变受体对125I-TGF-β1的结合亲和力。
我们的研究结果表明，小梁细胞表达对肝素酶不敏感的TGF-β受体，这些受体对TGF-β1的亲和力比对TGF-β2的亲和力大约高三倍。基于目前的研究以及我们之前关于结合位点分子量的数据，我们得出结论，小梁细胞确实拥有II型和III型受体，但不拥有I型受体。
